Remove heartbeat support
[openssl.git] / ssl / t1_lib.c
index 9250283..338334f 100644 (file)
 #include <openssl/ocsp.h>
 #include <openssl/conf.h>
 #include <openssl/x509v3.h>
-#include <openssl/rand.h>
 #include <openssl/dh.h>
 #include <openssl/bn.h>
 #include "ssl_locl.h"
 #include <openssl/ct.h>
 
-static int tls_decrypt_ticket(SSL *s, const unsigned char *tick, int ticklen,
-                              const unsigned char *sess_id, int sesslen,
+static int tls_decrypt_ticket(SSL *s, const unsigned char *tick, size_t ticklen,
+                              const unsigned char *sess_id, size_t sesslen,
                               SSL_SESSION **psess);
 static int ssl_check_clienthello_tlsext_early(SSL *s);
 static int ssl_check_serverhello_tlsext(SSL *s);
@@ -34,14 +33,13 @@ SSL3_ENC_METHOD const TLSv1_enc_data = {
     tls1_generate_master_secret,
     tls1_change_cipher_state,
     tls1_final_finish_mac,
-    TLS1_FINISH_MAC_LENGTH,
     TLS_MD_CLIENT_FINISH_CONST, TLS_MD_CLIENT_FINISH_CONST_SIZE,
     TLS_MD_SERVER_FINISH_CONST, TLS_MD_SERVER_FINISH_CONST_SIZE,
     tls1_alert_code,
     tls1_export_keying_material,
     0,
-    SSL3_HM_HEADER_LENGTH,
     ssl3_set_handshake_header,
+    tls_close_construct_packet,
     ssl3_handshake_write
 };
 
@@ -52,14 +50,13 @@ SSL3_ENC_METHOD const TLSv1_1_enc_data = {
     tls1_generate_master_secret,
     tls1_change_cipher_state,
     tls1_final_finish_mac,
-    TLS1_FINISH_MAC_LENGTH,
     TLS_MD_CLIENT_FINISH_CONST, TLS_MD_CLIENT_FINISH_CONST_SIZE,
     TLS_MD_SERVER_FINISH_CONST, TLS_MD_SERVER_FINISH_CONST_SIZE,
     tls1_alert_code,
     tls1_export_keying_material,
     SSL_ENC_FLAG_EXPLICIT_IV,
-    SSL3_HM_HEADER_LENGTH,
     ssl3_set_handshake_header,
+    tls_close_construct_packet,
     ssl3_handshake_write
 };
 
@@ -70,15 +67,32 @@ SSL3_ENC_METHOD const TLSv1_2_enc_data = {
     tls1_generate_master_secret,
     tls1_change_cipher_state,
     tls1_final_finish_mac,
-    TLS1_FINISH_MAC_LENGTH,
     TLS_MD_CLIENT_FINISH_CONST, TLS_MD_CLIENT_FINISH_CONST_SIZE,
     TLS_MD_SERVER_FINISH_CONST, TLS_MD_SERVER_FINISH_CONST_SIZE,
     tls1_alert_code,
     tls1_export_keying_material,
     SSL_ENC_FLAG_EXPLICIT_IV | SSL_ENC_FLAG_SIGALGS | SSL_ENC_FLAG_SHA256_PRF
         | SSL_ENC_FLAG_TLS1_2_CIPHERS,
-    SSL3_HM_HEADER_LENGTH,
     ssl3_set_handshake_header,
+    tls_close_construct_packet,
+    ssl3_handshake_write
+};
+
+SSL3_ENC_METHOD const TLSv1_3_enc_data = {
+    tls1_enc,
+    tls1_mac,
+    tls1_setup_key_block,
+    tls1_generate_master_secret,
+    tls1_change_cipher_state,
+    tls1_final_finish_mac,
+    TLS_MD_CLIENT_FINISH_CONST, TLS_MD_CLIENT_FINISH_CONST_SIZE,
+    TLS_MD_SERVER_FINISH_CONST, TLS_MD_SERVER_FINISH_CONST_SIZE,
+    tls1_alert_code,
+    tls1_export_keying_material,
+    SSL_ENC_FLAG_EXPLICIT_IV | SSL_ENC_FLAG_SIGALGS | SSL_ENC_FLAG_SHA256_PRF
+        | SSL_ENC_FLAG_TLS1_2_CIPHERS,
+    ssl3_set_handshake_header,
+    tls_close_construct_packet,
     ssl3_handshake_write
 };
 
@@ -122,12 +136,6 @@ typedef struct {
     unsigned int flags;         /* Flags: currently just field type */
 } tls_curve_info;
 
-/* Mask for curve type */
-# define TLS_CURVE_TYPE          0x3
-# define TLS_CURVE_PRIME         0x0
-# define TLS_CURVE_CHAR2         0x1
-# define TLS_CURVE_CUSTOM        0x2
-
 /*
  * Table of curve information.
  * Do not delete entries or reorder this array! It is used as a lookup
@@ -162,8 +170,7 @@ static const tls_curve_info nid_list[] = {
     {NID_brainpoolP256r1, 128, TLS_CURVE_PRIME}, /* brainpoolP256r1 (26) */
     {NID_brainpoolP384r1, 192, TLS_CURVE_PRIME}, /* brainpoolP384r1 (27) */
     {NID_brainpoolP512r1, 256, TLS_CURVE_PRIME}, /* brainpool512r1 (28) */
-    /* X25519 (29) */
-    {NID_X25519, 128, TLS_CURVE_CUSTOM},
+    {NID_X25519, 128, TLS_CURVE_CUSTOM}, /* X25519 (29) */
 };
 
 static const unsigned char ecformats_default[] = {
@@ -217,18 +224,21 @@ static const unsigned char eccurves_all[] = {
     0, 3,                       /* sect163r2 (3) */
 };
 
-
 static const unsigned char suiteb_curves[] = {
     0, TLSEXT_curve_P_256,
     0, TLSEXT_curve_P_384
 };
 
-int tls1_ec_curve_id2nid(int curve_id)
+int tls1_ec_curve_id2nid(int curve_id, unsigned int *pflags)
 {
+    const tls_curve_info *cinfo;
     /* ECC curves from RFC 4492 and RFC 7027 */
     if ((curve_id < 1) || ((unsigned int)curve_id > OSSL_NELEM(nid_list)))
         return 0;
-    return nid_list[curve_id - 1].nid;
+    cinfo = nid_list + curve_id - 1;
+    if (pflags)
+        *pflags = cinfo->flags;
+    return cinfo->nid;
 }
 
 int tls1_ec_nid2curve_id(int nid)
@@ -236,7 +246,7 @@ int tls1_ec_nid2curve_id(int nid)
     size_t i;
     for (i = 0; i < OSSL_NELEM(nid_list); i++) {
         if (nid_list[i].nid == nid)
-            return i + 1;
+            return (int)(i + 1);
     }
     return 0;
 }
@@ -254,13 +264,12 @@ int tls1_ec_nid2curve_id(int nid)
  * so cannot happen in the 1.0.x series.)
  */
 static int tls1_get_curvelist(SSL *s, int sess,
-                              const unsigned char **pcurves,
-                              size_t *num_curves)
+                              const unsigned char **pcurves, size_t *num_curves)
 {
     size_t pcurveslen = 0;
     if (sess) {
-        *pcurves = s->session->tlsext_ellipticcurvelist;
-        pcurveslen = s->session->tlsext_ellipticcurvelist_length;
+        *pcurves = s->session->tlsext_supportedgroupslist;
+        pcurveslen = s->session->tlsext_supportedgroupslist_length;
     } else {
         /* For Suite B mode only include P-256, P-384 */
         switch (tls1_suiteb(s)) {
@@ -279,8 +288,8 @@ static int tls1_get_curvelist(SSL *s, int sess,
             pcurveslen = 2;
             break;
         default:
-            *pcurves = s->tlsext_ellipticcurvelist;
-            pcurveslen = s->tlsext_ellipticcurvelist_length;
+            *pcurves = s->tlsext_supportedgroupslist;
+            pcurveslen = s->tlsext_supportedgroupslist_length;
         }
         if (!*pcurves) {
             *pcurves = eccurves_default;
@@ -347,13 +356,13 @@ int tls1_check_curve(SSL *s, const unsigned char *p, size_t len)
 }
 
 /*-
- * For nmatch >= 0, return the NID of the |nmatch|th shared curve or NID_undef
+ * For nmatch >= 0, return the NID of the |nmatch|th shared group or NID_undef
  * if there is no match.
  * For nmatch == -1, return number of matches
- * For nmatch == -2, return the NID of the curve to use for
+ * For nmatch == -2, return the NID of the group to use for
  * an EC tmp key, or NID_undef if there is no match.
  */
-int tls1_shared_curve(SSL *s, int nmatch)
+int tls1_shared_group(SSL *s, int nmatch)
 {
     const unsigned char *pref, *supp;
     size_t num_pref, num_supp, i, j;
@@ -388,8 +397,7 @@ int tls1_shared_curve(SSL *s, int nmatch)
         /* In practice, NID_undef == 0 but let's be precise. */
         return nmatch == -1 ? 0 : NID_undef;
     if (!tls1_get_curvelist
-        (s, !(s->options & SSL_OP_CIPHER_SERVER_PREFERENCE), &pref,
-         &num_pref))
+        (s, !(s->options & SSL_OP_CIPHER_SERVER_PREFERENCE), &pref, &num_pref))
         return nmatch == -1 ? 0 : NID_undef;
 
     /*
@@ -400,7 +408,7 @@ int tls1_shared_curve(SSL *s, int nmatch)
         supp = eccurves_all;
         num_supp = sizeof(eccurves_all) / 2;
     } else if (num_pref == 0 &&
-        (s->options & SSL_OP_CIPHER_SERVER_PREFERENCE) == 0) {
+               (s->options & SSL_OP_CIPHER_SERVER_PREFERENCE) == 0) {
         pref = eccurves_all;
         num_pref = sizeof(eccurves_all) / 2;
     }
@@ -414,7 +422,7 @@ int tls1_shared_curve(SSL *s, int nmatch)
                     continue;
                 if (nmatch == k) {
                     int id = (pref[0] << 8) | pref[1];
-                    return tls1_ec_curve_id2nid(id);
+                    return tls1_ec_curve_id2nid(id, NULL);
                 }
                 k++;
             }
@@ -426,34 +434,35 @@ int tls1_shared_curve(SSL *s, int nmatch)
     return NID_undef;
 }
 
-int tls1_set_curves(unsigned char **pext, size_t *pextlen,
-                    int *curves, size_t ncurves)
+int tls1_set_groups(unsigned char **pext, size_t *pextlen,
+                    int *groups, size_t ngroups)
 {
-    unsigned char *clist, *p;
+    unsigned char *glist, *p;
     size_t i;
     /*
-     * Bitmap of curves included to detect duplicates: only works while curve
+     * Bitmap of groups included to detect duplicates: only works while group
      * ids < 32
      */
     unsigned long dup_list = 0;
-    clist = OPENSSL_malloc(ncurves * 2);
-    if (clist == NULL)
+    glist = OPENSSL_malloc(ngroups * 2);
+    if (glist == NULL)
         return 0;
-    for (i = 0, p = clist; i < ncurves; i++) {
+    for (i = 0, p = glist; i < ngroups; i++) {
         unsigned long idmask;
         int id;
-        id = tls1_ec_nid2curve_id(curves[i]);
+        /* TODO(TLS1.3): Convert for DH groups */
+        id = tls1_ec_nid2curve_id(groups[i]);
         idmask = 1L << id;
         if (!id || (dup_list & idmask)) {
-            OPENSSL_free(clist);
+            OPENSSL_free(glist);
             return 0;
         }
         dup_list |= idmask;
         s2n(id, p);
     }
     OPENSSL_free(*pext);
-    *pext = clist;
-    *pextlen = ncurves * 2;
+    *pext = glist;
+    *pextlen = ngroups * 2;
     return 1;
 }
 
@@ -492,9 +501,8 @@ static int nid_cb(const char *elem, int len, void *arg)
     return 1;
 }
 
-/* Set curves based on a colon separate list */
-int tls1_set_curves_list(unsigned char **pext, size_t *pextlen,
-                         const char *str)
+/* Set groups based on a colon separate list */
+int tls1_set_groups_list(unsigned char **pext, size_t *pextlen, const char *str)
 {
     nid_cb_st ncb;
     ncb.nidcnt = 0;
@@ -502,7 +510,7 @@ int tls1_set_curves_list(unsigned char **pext, size_t *pextlen,
         return 0;
     if (pext == NULL)
         return 1;
-    return tls1_set_curves(pext, pextlen, ncb.nid_arr, ncb.nidcnt);
+    return tls1_set_groups(pext, pextlen, ncb.nid_arr, ncb.nidcnt);
 }
 
 /* For an EC key set TLS id and required compression based on parameters */
@@ -699,7 +707,7 @@ int tls1_check_ec_tmp_key(SSL *s, unsigned long cid)
         return 1;
     }
     /* Need a shared curve */
-    if (tls1_shared_curve(s, 0))
+    if (tls1_shared_group(s, 0))
         return 1;
     return 0;
 }
@@ -720,19 +728,19 @@ static int tls1_check_cert_param(SSL *s, X509 *x, int set_ee_md)
  */
 
 #ifdef OPENSSL_NO_RSA
-# define tlsext_sigalg_rsa(md) /* */
+# define tlsext_sigalg_rsa(md)  /* */
 #else
 # define tlsext_sigalg_rsa(md) md, TLSEXT_signature_rsa,
 #endif
 
 #ifdef OPENSSL_NO_DSA
-# define tlsext_sigalg_dsa(md) /* */
+# define tlsext_sigalg_dsa(md)  /* */
 #else
 # define tlsext_sigalg_dsa(md) md, TLSEXT_signature_dsa,
 #endif
 
 #ifdef OPENSSL_NO_EC
-# define tlsext_sigalg_ecdsa(md) /* */
+# define tlsext_sigalg_ecdsa(md)/* */
 #else
 # define tlsext_sigalg_ecdsa(md) md, TLSEXT_signature_ecdsa,
 #endif
@@ -750,8 +758,8 @@ static const unsigned char tls12_sigalgs[] = {
         tlsext_sigalg(TLSEXT_hash_sha1)
 #ifndef OPENSSL_NO_GOST
         TLSEXT_hash_gostr3411, TLSEXT_signature_gostr34102001,
-        TLSEXT_hash_gostr34112012_256, TLSEXT_signature_gostr34102012_256,
-        TLSEXT_hash_gostr34112012_512, TLSEXT_signature_gostr34102012_512
+    TLSEXT_hash_gostr34112012_256, TLSEXT_signature_gostr34102012_256,
+    TLSEXT_hash_gostr34112012_512, TLSEXT_signature_gostr34102012_512
 #endif
 };
 
@@ -866,8 +874,7 @@ int tls12_check_peer_sigalg(const EVP_MD **pmd, SSL *s,
     }
     /* Make sure security callback allows algorithm */
     if (!ssl_security(s, SSL_SECOP_SIGALG_CHECK,
-                      EVP_MD_size(*pmd) * 4, EVP_MD_type(*pmd),
-                      (void *)sig)) {
+                      EVP_MD_size(*pmd) * 4, EVP_MD_type(*pmd), (void *)sig)) {
         SSLerr(SSL_F_TLS12_CHECK_PEER_SIGALG, SSL_R_WRONG_SIGNATURE_TYPE);
         return 0;
     }
@@ -894,13 +901,13 @@ void ssl_set_client_disabled(SSL *s)
     s->s3->tmp.mask_k = 0;
     ssl_set_sig_mask(&s->s3->tmp.mask_a, s, SSL_SECOP_SIGALG_MASK);
     ssl_get_client_min_max_version(s, &s->s3->tmp.min_ver, &s->s3->tmp.max_ver);
-# ifndef OPENSSL_NO_PSK
+#ifndef OPENSSL_NO_PSK
     /* with PSK there must be client callback set */
     if (!s->psk_client_callback) {
         s->s3->tmp.mask_a |= SSL_aPSK;
         s->s3->tmp.mask_k |= SSL_PSK;
     }
-#endif                         /* OPENSSL_NO_PSK */
+#endif                          /* OPENSSL_NO_PSK */
 #ifndef OPENSSL_NO_SRP
     if (!(s->srp_ctx.srp_Mask & SSL_kSRP)) {
         s->s3->tmp.mask_a |= SSL_aSRP;
@@ -925,10 +932,10 @@ int ssl_cipher_disabled(SSL *s, const SSL_CIPHER *c, int op)
     if (s->s3->tmp.max_ver == 0)
         return 1;
     if (!SSL_IS_DTLS(s) && ((c->min_tls > s->s3->tmp.max_ver)
-            || (c->max_tls < s->s3->tmp.min_ver)))
+                            || (c->max_tls < s->s3->tmp.min_ver)))
         return 1;
     if (SSL_IS_DTLS(s) && (DTLS_VERSION_GT(c->min_dtls, s->s3->tmp.max_ver)
-            || DTLS_VERSION_LT(c->max_dtls, s->s3->tmp.min_ver)))
+                           || DTLS_VERSION_LT(c->max_dtls, s->s3->tmp.min_ver)))
         return 1;
 
     return !ssl_security(s, op, c->strength_bits, 0, (void *)c);
@@ -941,7 +948,8 @@ static int tls_use_ticket(SSL *s)
     return ssl_security(s, SSL_SECOP_TICKET, 0, 0, NULL);
 }
 
-static int compare_uint(const void *p1, const void *p2) {
+static int compare_uint(const void *p1, const void *p2)
+{
     unsigned int u1 = *((const unsigned int *)p1);
     unsigned int u2 = *((const unsigned int *)p2);
     if (u1 < u2)
@@ -960,7 +968,8 @@ static int compare_uint(const void *p1, const void *p2) {
  * contain duplicates, could not be successfully parsed, or an internal error
  * occurred.
  */
-static int tls1_check_duplicate_extensions(const PACKET *packet) {
+static int tls1_check_duplicate_extensions(const PACKET *packet)
+{
     PACKET extensions = *packet;
     size_t num_extensions = 0, i = 0;
     unsigned int *extension_types = NULL;
@@ -1014,12 +1023,8 @@ static int tls1_check_duplicate_extensions(const PACKET *packet) {
     return ret;
 }
 
-unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf,
-                                          unsigned char *limit, int *al)
+int ssl_add_clienthello_tlsext(SSL *s, WPACKET *pkt, int *al)
 {
-    int extdatalen = 0;
-    unsigned char *orig = buf;
-    unsigned char *ret = buf;
 #ifndef OPENSSL_NO_EC
     /* See if we support any ECC ciphersuites */
     int using_ecc = 0;
@@ -1034,7 +1039,7 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf,
             alg_k = c->algorithm_mkey;
             alg_a = c->algorithm_auth;
             if ((alg_k & (SSL_kECDHE | SSL_kECDHEPSK))
-                 || (alg_a & SSL_aECDSA)) {
+                || (alg_a & SSL_aECDSA)) {
                 using_ecc = 1;
                 break;
             }
@@ -1042,32 +1047,16 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf,
     }
 #endif
 
-    ret += 2;
-
-    if (ret >= limit)
-        return NULL;            /* this really never occurs, but ... */
-
     /* Add RI if renegotiating */
     if (s->renegotiate) {
-        int el;
-
-        if (!ssl_add_clienthello_renegotiate_ext(s, 0, &el, 0)) {
-            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
-        }
-
-        if ((limit - ret - 4 - el) < 0)
-            return NULL;
-
-        s2n(TLSEXT_TYPE_renegotiate, ret);
-        s2n(el, ret);
-
-        if (!ssl_add_clienthello_renegotiate_ext(s, ret, &el, el)) {
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_renegotiate)
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_sub_memcpy_u8(pkt, s->s3->previous_client_finished,
+                                   s->s3->previous_client_finished_len)
+                || !WPACKET_close(pkt)) {
             SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
+            return 0;
         }
-
-        ret += el;
     }
     /* Only add RI for SSLv3 */
     if (s->client_version == SSL3_VERSION)
@@ -1075,62 +1064,36 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf,
 
     if (s->tlsext_hostname != NULL) {
         /* Add TLS extension servername to the Client Hello message */
-        unsigned long size_str;
-        long lenmax;
-
-        /*-
-         * check for enough space.
-         * 4 for the servername type and extension length
-         * 2 for servernamelist length
-         * 1 for the hostname type
-         * 2 for hostname length
-         * + hostname length
-         */
-
-        if ((lenmax = limit - ret - 9) < 0
-            || (size_str =
-                strlen(s->tlsext_hostname)) > (unsigned long)lenmax)
-            return NULL;
-
-        /* extension type and length */
-        s2n(TLSEXT_TYPE_server_name, ret);
-        s2n(size_str + 5, ret);
-
-        /* length of servername list */
-        s2n(size_str + 3, ret);
-
-        /* hostname type, length and hostname */
-        *(ret++) = (unsigned char)TLSEXT_NAMETYPE_host_name;
-        s2n(size_str, ret);
-        memcpy(ret, s->tlsext_hostname, size_str);
-        ret += size_str;
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_server_name)
+                   /* Sub-packet for server_name extension */
+                || !WPACKET_start_sub_packet_u16(pkt)
+                   /* Sub-packet for servername list (always 1 hostname)*/
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_put_bytes_u8(pkt, TLSEXT_NAMETYPE_host_name)
+                || !WPACKET_sub_memcpy_u16(pkt, s->tlsext_hostname,
+                                           strlen(s->tlsext_hostname))
+                || !WPACKET_close(pkt)
+                || !WPACKET_close(pkt)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
     }
 #ifndef OPENSSL_NO_SRP
     /* Add SRP username if there is one */
-    if (s->srp_ctx.login != NULL) { /* Add TLS extension SRP username to the
-                                     * Client Hello message */
-
-        int login_len = strlen(s->srp_ctx.login);
-        if (login_len > 255 || login_len == 0) {
+    if (s->srp_ctx.login != NULL) {
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_srp)
+                   /* Sub-packet for SRP extension */
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_start_sub_packet_u8(pkt)
+                   /* login must not be zero...internal error if so */
+                || !WPACKET_set_flags(pkt, WPACKET_FLAGS_NON_ZERO_LENGTH)
+                || !WPACKET_memcpy(pkt, s->srp_ctx.login,
+                                   strlen(s->srp_ctx.login))
+                || !WPACKET_close(pkt)
+                || !WPACKET_close(pkt)) {
             SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
+            return 0;
         }
-
-        /*-
-         * check for enough space.
-         * 4 for the srp type type and extension length
-         * 1 for the srp user identity
-         * + srp user identity length
-         */
-        if ((limit - ret - 5 - login_len) < 0)
-            return NULL;
-
-        /* fill in the extension */
-        s2n(TLSEXT_TYPE_srp, ret);
-        s2n(login_len + 1, ret);
-        (*ret++) = (unsigned char)login_len;
-        memcpy(ret, s->srp_ctx.login, login_len);
-        ret += login_len;
     }
 #endif
 
@@ -1139,74 +1102,68 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf,
         /*
          * Add TLS extension ECPointFormats to the ClientHello message
          */
-        long lenmax;
         const unsigned char *pcurves, *pformats;
-        size_t num_curves, num_formats, curves_list_len;
+        size_t num_curves, num_formats;
         size_t i;
-        unsigned char *etmp;
 
         tls1_get_formatlist(s, &pformats, &num_formats);
 
-        if ((lenmax = limit - ret - 5) < 0)
-            return NULL;
-        if (num_formats > (size_t)lenmax)
-            return NULL;
-        if (num_formats > 255) {
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_ec_point_formats)
+                   /* Sub-packet for formats extension */
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_sub_memcpy_u8(pkt, pformats, num_formats)
+                || !WPACKET_close(pkt)) {
             SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
+            return 0;
         }
 
-        s2n(TLSEXT_TYPE_ec_point_formats, ret);
-        /* The point format list has 1-byte length. */
-        s2n(num_formats + 1, ret);
-        *(ret++) = (unsigned char)num_formats;
-        memcpy(ret, pformats, num_formats);
-        ret += num_formats;
-
         /*
-         * Add TLS extension EllipticCurves to the ClientHello message
+         * Add TLS extension supported_groups to the ClientHello message
          */
-        pcurves = s->tlsext_ellipticcurvelist;
-        if (!tls1_get_curvelist(s, 0, &pcurves, &num_curves))
-            return NULL;
-
-        if ((lenmax = limit - ret - 6) < 0)
-            return NULL;
-        if (num_curves > (size_t)lenmax / 2)
-            return NULL;
-        if (num_curves > 65532 / 2) {
+        /* TODO(TLS1.3): Add support for DHE groups */
+        pcurves = s->tlsext_supportedgroupslist;
+        if (!tls1_get_curvelist(s, 0, &pcurves, &num_curves)) {
             SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
+            return 0;
         }
 
-        s2n(TLSEXT_TYPE_elliptic_curves, ret);
-        etmp = ret + 4;
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_supported_groups)
+                   /* Sub-packet for supported_groups extension */
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_start_sub_packet_u16(pkt)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
         /* Copy curve ID if supported */
         for (i = 0; i < num_curves; i++, pcurves += 2) {
             if (tls_curve_allowed(s, pcurves, SSL_SECOP_CURVE_SUPPORTED)) {
-                *etmp++ = pcurves[0];
-                *etmp++ = pcurves[1];
+                if (!WPACKET_put_bytes_u8(pkt, pcurves[0])
+                    || !WPACKET_put_bytes_u8(pkt, pcurves[1])) {
+                        SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT,
+                               ERR_R_INTERNAL_ERROR);
+                        return 0;
+                    }
             }
         }
-
-        curves_list_len = etmp - ret - 4;
-
-        s2n(curves_list_len + 2, ret);
-        s2n(curves_list_len, ret);
-        ret += curves_list_len;
+        if (!WPACKET_close(pkt) || !WPACKET_close(pkt)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
     }
-#endif                         /* OPENSSL_NO_EC */
+#endif                          /* OPENSSL_NO_EC */
 
     if (tls_use_ticket(s)) {
-        int ticklen;
+        size_t ticklen;
         if (!s->new_session && s->session && s->session->tlsext_tick)
             ticklen = s->session->tlsext_ticklen;
         else if (s->session && s->tlsext_session_ticket &&
                  s->tlsext_session_ticket->data) {
             ticklen = s->tlsext_session_ticket->length;
             s->session->tlsext_tick = OPENSSL_malloc(ticklen);
-            if (s->session->tlsext_tick == NULL)
-                return NULL;
+            if (s->session->tlsext_tick == NULL) {
+                SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+                return 0;
+            }
             memcpy(s->session->tlsext_tick,
                    s->tlsext_session_ticket->data, ticklen);
             s->session->tlsext_ticklen = ticklen;
@@ -1215,17 +1172,12 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf,
         if (ticklen == 0 && s->tlsext_session_ticket &&
             s->tlsext_session_ticket->data == NULL)
             goto skip_ext;
-        /*
-         * Check for enough room 2 for extension type, 2 for len rest for
-         * ticket
-         */
-        if ((long)(limit - ret - 4 - ticklen) < 0)
-            return NULL;
-        s2n(TLSEXT_TYPE_session_ticket, ret);
-        s2n(ticklen, ret);
-        if (ticklen) {
-            memcpy(ret, s->session->tlsext_tick, ticklen);
-            ret += ticklen;
+
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_session_ticket)
+                || !WPACKET_sub_memcpy_u16(pkt, s->session->tlsext_tick,
+                                           ticklen)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
         }
     }
  skip_ext:
@@ -1233,82 +1185,73 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf,
     if (SSL_CLIENT_USE_SIGALGS(s)) {
         size_t salglen;
         const unsigned char *salg;
-        unsigned char *etmp;
+
         salglen = tls12_get_psigalgs(s, &salg);
-        if ((size_t)(limit - ret) < salglen + 6)
-            return NULL;
-        s2n(TLSEXT_TYPE_signature_algorithms, ret);
-        etmp = ret;
-        /* Skip over lengths for now */
-        ret += 4;
-        salglen = tls12_copy_sigalgs(s, ret, salg, salglen);
-        /* Fill in lengths */
-        s2n(salglen + 2, etmp);
-        s2n(salglen, etmp);
-        ret += salglen;
-    }
 
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_signature_algorithms)
+                   /* Sub-packet for sig-algs extension */
+                || !WPACKET_start_sub_packet_u16(pkt)
+                   /* Sub-packet for the actual list */
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !tls12_copy_sigalgs(s, pkt, salg, salglen)
+                || !WPACKET_close(pkt)
+                || !WPACKET_close(pkt)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
+    }
 #ifndef OPENSSL_NO_OCSP
     if (s->tlsext_status_type == TLSEXT_STATUSTYPE_ocsp) {
         int i;
-        long extlen, idlen, itmp;
-        OCSP_RESPID *id;
 
-        idlen = 0;
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_status_request)
+                   /* Sub-packet for status request extension */
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_put_bytes_u8(pkt, TLSEXT_STATUSTYPE_ocsp)
+                   /* Sub-packet for the ids */
+                || !WPACKET_start_sub_packet_u16(pkt)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
         for (i = 0; i < sk_OCSP_RESPID_num(s->tlsext_ocsp_ids); i++) {
+            unsigned char *idbytes;
+            int idlen;
+            OCSP_RESPID *id;
+
             id = sk_OCSP_RESPID_value(s->tlsext_ocsp_ids, i);
-            itmp = i2d_OCSP_RESPID(id, NULL);
-            if (itmp <= 0)
-                return NULL;
-            idlen += itmp + 2;
+            idlen = i2d_OCSP_RESPID(id, NULL);
+            if (idlen <= 0
+                       /* Sub-packet for an individual id */
+                    || !WPACKET_sub_allocate_bytes_u16(pkt, idlen, &idbytes)
+                    || i2d_OCSP_RESPID(id, &idbytes) != idlen) {
+                SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+                return 0;
+            }
+        }
+        if (!WPACKET_close(pkt)
+                || !WPACKET_start_sub_packet_u16(pkt)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
         }
-
         if (s->tlsext_ocsp_exts) {
-            extlen = i2d_X509_EXTENSIONS(s->tlsext_ocsp_exts, NULL);
-            if (extlen < 0)
-                return NULL;
-        } else
-            extlen = 0;
+            unsigned char *extbytes;
+            int extlen = i2d_X509_EXTENSIONS(s->tlsext_ocsp_exts, NULL);
 
-        if ((long)(limit - ret - 7 - extlen - idlen) < 0)
-            return NULL;
-        s2n(TLSEXT_TYPE_status_request, ret);
-        if (extlen + idlen > 0xFFF0)
-            return NULL;
-        s2n(extlen + idlen + 5, ret);
-        *(ret++) = TLSEXT_STATUSTYPE_ocsp;
-        s2n(idlen, ret);
-        for (i = 0; i < sk_OCSP_RESPID_num(s->tlsext_ocsp_ids); i++) {
-            /* save position of id len */
-            unsigned char *q = ret;
-            id = sk_OCSP_RESPID_value(s->tlsext_ocsp_ids, i);
-            /* skip over id len */
-            ret += 2;
-            itmp = i2d_OCSP_RESPID(id, &ret);
-            /* write id len */
-            s2n(itmp, q);
+            if (extlen < 0) {
+                SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+                return 0;
+            }
+            if (!WPACKET_allocate_bytes(pkt, extlen, &extbytes)
+                    || i2d_X509_EXTENSIONS(s->tlsext_ocsp_exts, &extbytes)
+                       != extlen) {
+                SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+                return 0;
+           }
+        }
+        if (!WPACKET_close(pkt) || !WPACKET_close(pkt)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
         }
-        s2n(extlen, ret);
-        if (extlen > 0)
-            i2d_X509_EXTENSIONS(s->tlsext_ocsp_exts, &ret);
-    }
-#endif
-#ifndef OPENSSL_NO_HEARTBEATS
-    if (SSL_IS_DTLS(s)) {
-        /* Add Heartbeat extension */
-        if ((limit - ret - 4 - 1) < 0)
-            return NULL;
-        s2n(TLSEXT_TYPE_heartbeat, ret);
-        s2n(1, ret);
-        /*-
-         * Set mode:
-         * 1: peer may send requests
-         * 2: peer not allowed to send requests
-         */
-        if (s->tlsext_heartbeat & SSL_DTLSEXT_HB_DONT_RECV_REQUESTS)
-            *(ret++) = SSL_DTLSEXT_HB_DONT_SEND_REQUESTS;
-        else
-            *(ret++) = SSL_DTLSEXT_HB_ENABLED;
     }
 #endif
 
@@ -1318,10 +1261,11 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf,
          * The client advertises an empty extension to indicate its support
          * for Next Protocol Negotiation
          */
-        if (limit - ret - 4 < 0)
-            return NULL;
-        s2n(TLSEXT_TYPE_next_proto_neg, ret);
-        s2n(0, ret);
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_next_proto_neg)
+                || !WPACKET_put_bytes_u16(pkt, 0)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
     }
 #endif
 
@@ -1331,52 +1275,116 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf,
      * (see longer comment below)
      */
     if (s->alpn_client_proto_list && !s->s3->tmp.finish_md_len) {
-        if ((size_t)(limit - ret) < 6 + s->alpn_client_proto_list_len)
-            return NULL;
-        s2n(TLSEXT_TYPE_application_layer_protocol_negotiation, ret);
-        s2n(2 + s->alpn_client_proto_list_len, ret);
-        s2n(s->alpn_client_proto_list_len, ret);
-        memcpy(ret, s->alpn_client_proto_list, s->alpn_client_proto_list_len);
-        ret += s->alpn_client_proto_list_len;
+        if (!WPACKET_put_bytes_u16(pkt,
+                    TLSEXT_TYPE_application_layer_protocol_negotiation)
+                   /* Sub-packet ALPN extension */
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_sub_memcpy_u16(pkt, s->alpn_client_proto_list,
+                                           s->alpn_client_proto_list_len)
+                || !WPACKET_close(pkt)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
         s->s3->alpn_sent = 1;
     }
 #ifndef OPENSSL_NO_SRTP
     if (SSL_IS_DTLS(s) && SSL_get_srtp_profiles(s)) {
-        int el;
-
-        /* Returns 0 on success!! */
-        if (ssl_add_clienthello_use_srtp_ext(s, 0, &el, 0)) {
+        STACK_OF(SRTP_PROTECTION_PROFILE) *clnt = SSL_get_srtp_profiles(s);
+        SRTP_PROTECTION_PROFILE *prof;
+        int i, ct;
+
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_use_srtp)
+                   /* Sub-packet for SRTP extension */
+                || !WPACKET_start_sub_packet_u16(pkt)
+                   /* Sub-packet for the protection profile list */
+                || !WPACKET_start_sub_packet_u16(pkt)) {
             SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
+            return 0;
         }
-
-        if ((limit - ret - 4 - el) < 0)
-            return NULL;
-
-        s2n(TLSEXT_TYPE_use_srtp, ret);
-        s2n(el, ret);
-
-        if (ssl_add_clienthello_use_srtp_ext(s, ret, &el, el)) {
+        ct = sk_SRTP_PROTECTION_PROFILE_num(clnt);
+        for (i = 0; i < ct; i++) {
+            prof = sk_SRTP_PROTECTION_PROFILE_value(clnt, i);
+            if (prof == NULL || !WPACKET_put_bytes_u16(pkt, prof->id)) {
+                SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+                return 0;
+            }
+        }
+        if (!WPACKET_close(pkt)
+                   /* Add an empty use_mki value */
+                || !WPACKET_put_bytes_u8(pkt, 0)
+                || !WPACKET_close(pkt)) {
             SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
+            return 0;
         }
-        ret += el;
     }
 #endif
     custom_ext_init(&s->cert->cli_ext);
     /* Add custom TLS Extensions to ClientHello */
-    if (!custom_ext_add(s, 0, &ret, limit, al))
-        return NULL;
-    s2n(TLSEXT_TYPE_encrypt_then_mac, ret);
-    s2n(0, ret);
+    if (!custom_ext_add(s, 0, pkt, al)) {
+        SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+        return 0;
+    }
+
+    if (!(s->options & SSL_OP_NO_ENCRYPT_THEN_MAC)) {
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_encrypt_then_mac)
+            || !WPACKET_put_bytes_u16(pkt, 0)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
+    }
+
 #ifndef OPENSSL_NO_CT
     if (s->ct_validation_callback != NULL) {
-        s2n(TLSEXT_TYPE_signed_certificate_timestamp, ret);
-        s2n(0, ret);
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_signed_certificate_timestamp)
+                || !WPACKET_put_bytes_u16(pkt, 0)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
     }
 #endif
-    s2n(TLSEXT_TYPE_extended_master_secret, ret);
-    s2n(0, ret);
+
+    if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_extended_master_secret)
+            || !WPACKET_put_bytes_u16(pkt, 0)) {
+        SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+        return 0;
+    }
+
+    if (SSL_IS_TLS13(s)) {
+        int min_version, max_version, reason, currv;
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_supported_versions)
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_start_sub_packet_u8(pkt)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
+        reason = ssl_get_client_min_max_version(s, &min_version, &max_version);
+        if (reason != 0) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, reason);
+            return 0;
+        }
+        /*
+         * TODO(TLS1.3): There is some discussion on the TLS list as to wheter
+         * we should include versions <TLS1.2. For the moment we do. To be
+         * reviewed later.
+         */
+        for (currv = max_version; currv >= min_version; currv--) {
+            /* TODO(TLS1.3): Remove this first if clause prior to release!! */
+            if (currv == TLS1_3_VERSION) {
+                if (!WPACKET_put_bytes_u16(pkt, TLS1_3_VERSION_DRAFT)) {
+                    SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT,
+                           ERR_R_INTERNAL_ERROR);
+                    return 0;
+                }
+            } else if (!WPACKET_put_bytes_u16(pkt, currv)) {
+                SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+                return 0;
+            }
+        }
+        if (!WPACKET_close(pkt) || !WPACKET_close(pkt)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
+    }
 
     /*
      * Add padding to workaround bugs in F5 terminators. See
@@ -1385,7 +1393,13 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf,
      * appear last.
      */
     if (s->options & SSL_OP_TLSEXT_PADDING) {
-        int hlen = ret - (unsigned char *)s->init_buf->data;
+        unsigned char *padbytes;
+        size_t hlen;
+
+        if (!WPACKET_get_total_written(pkt, &hlen)) {
+            SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
 
         if (hlen > 0xff && hlen < 0x200) {
             hlen = 0x200 - hlen;
@@ -1394,28 +1408,21 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf,
             else
                 hlen = 0;
 
-            s2n(TLSEXT_TYPE_padding, ret);
-            s2n(hlen, ret);
-            memset(ret, 0, hlen);
-            ret += hlen;
+            if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_padding)
+                    || !WPACKET_sub_allocate_bytes_u16(pkt, hlen, &padbytes)) {
+                SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+                return 0;
+            }
+            memset(padbytes, 0, hlen);
         }
     }
 
  done:
-
-    if ((extdatalen = ret - orig - 2) == 0)
-        return orig;
-
-    s2n(extdatalen, orig);
-    return ret;
+    return 1;
 }
 
-unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *buf,
-                                          unsigned char *limit, int *al)
+int ssl_add_serverhello_tlsext(SSL *s, WPACKET *pkt, int *al)
 {
-    int extdatalen = 0;
-    unsigned char *orig = buf;
-    unsigned char *ret = buf;
 #ifndef OPENSSL_NO_NEXTPROTONEG
     int next_proto_neg_seen;
 #endif
@@ -1426,30 +1433,16 @@ unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *buf,
     using_ecc = using_ecc && (s->session->tlsext_ecpointformatlist != NULL);
 #endif
 
-    ret += 2;
-    if (ret >= limit)
-        return NULL;            /* this really never occurs, but ... */
-
-    if (s->s3->send_connection_binding) {
-        int el;
-
-        if (!ssl_add_serverhello_renegotiate_ext(s, 0, &el, 0)) {
-            SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
-        }
-
-        if ((limit - ret - 4 - el) < 0)
-            return NULL;
-
-        s2n(TLSEXT_TYPE_renegotiate, ret);
-        s2n(el, ret);
-
-        if (!ssl_add_serverhello_renegotiate_ext(s, ret, &el, el)) {
-            SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
-        }
+    if (!WPACKET_start_sub_packet_u16(pkt)
+            || !WPACKET_set_flags(pkt, WPACKET_FLAGS_ABANDON_ON_ZERO_LENGTH)) {
+        SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+        return 0;
+    }
 
-        ret += el;
+    if (s->s3->send_connection_binding &&
+            !ssl_add_serverhello_renegotiate_ext(s, pkt)) {
+        SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+        return 0;
     }
 
     /* Only add RI for SSLv3 */
@@ -1457,12 +1450,12 @@ unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *buf,
         goto done;
 
     if (!s->hit && s->servername_done == 1
-        && s->session->tlsext_hostname != NULL) {
-        if ((long)(limit - ret - 4) < 0)
-            return NULL;
-
-        s2n(TLSEXT_TYPE_server_name, ret);
-        s2n(0, ret);
+            && s->session->tlsext_hostname != NULL) {
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_server_name)
+                || !WPACKET_put_bytes_u16(pkt, 0)) {
+            SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
     }
 #ifndef OPENSSL_NO_EC
     if (using_ecc) {
@@ -1471,69 +1464,54 @@ unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *buf,
         /*
          * Add TLS extension ECPointFormats to the ServerHello message
          */
-        long lenmax;
-
         tls1_get_formatlist(s, &plist, &plistlen);
 
-        if ((lenmax = limit - ret - 5) < 0)
-            return NULL;
-        if (plistlen > (size_t)lenmax)
-            return NULL;
-        if (plistlen > 255) {
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_ec_point_formats)
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_sub_memcpy_u8(pkt, plist, plistlen)
+                || !WPACKET_close(pkt)) {
             SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
+            return 0;
         }
-
-        s2n(TLSEXT_TYPE_ec_point_formats, ret);
-        s2n(plistlen + 1, ret);
-        *(ret++) = (unsigned char)plistlen;
-        memcpy(ret, plist, plistlen);
-        ret += plistlen;
-
     }
     /*
      * Currently the server should not respond with a SupportedCurves
      * extension
      */
-#endif                         /* OPENSSL_NO_EC */
+#endif                          /* OPENSSL_NO_EC */
 
     if (s->tlsext_ticket_expected && tls_use_ticket(s)) {
-        if ((long)(limit - ret - 4) < 0)
-            return NULL;
-        s2n(TLSEXT_TYPE_session_ticket, ret);
-        s2n(0, ret);
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_session_ticket)
+                || !WPACKET_put_bytes_u16(pkt, 0)) {
+            SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
     } else {
-        /* if we don't add the above TLSEXT, we can't add a session ticket later */
+        /*
+         * if we don't add the above TLSEXT, we can't add a session ticket
+         * later
+         */
         s->tlsext_ticket_expected = 0;
     }
 
     if (s->tlsext_status_expected) {
-        if ((long)(limit - ret - 4) < 0)
-            return NULL;
-        s2n(TLSEXT_TYPE_status_request, ret);
-        s2n(0, ret);
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_status_request)
+                || !WPACKET_put_bytes_u16(pkt, 0)) {
+            SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
     }
-
 #ifndef OPENSSL_NO_SRTP
     if (SSL_IS_DTLS(s) && s->srtp_profile) {
-        int el;
-
-        /* Returns 0 on success!! */
-        if (ssl_add_serverhello_use_srtp_ext(s, 0, &el, 0)) {
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_use_srtp)
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_put_bytes_u16(pkt, 2)
+                || !WPACKET_put_bytes_u16(pkt, s->srtp_profile->id)
+                || !WPACKET_put_bytes_u8(pkt, 0)
+                || !WPACKET_close(pkt)) {
             SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
-        }
-        if ((limit - ret - 4 - el) < 0)
-            return NULL;
-
-        s2n(TLSEXT_TYPE_use_srtp, ret);
-        s2n(el, ret);
-
-        if (ssl_add_serverhello_use_srtp_ext(s, ret, &el, el)) {
-            SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
-            return NULL;
+            return 0;
         }
-        ret += el;
     }
 #endif
 
@@ -1548,31 +1526,11 @@ unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *buf,
             0x2a, 0x85, 0x03, 0x02, 0x02, 0x16, 0x30, 0x08,
             0x06, 0x06, 0x2a, 0x85, 0x03, 0x02, 0x02, 0x17
         };
-        if (limit - ret < 36)
-            return NULL;
-        memcpy(ret, cryptopro_ext, 36);
-        ret += 36;
-
-    }
-#ifndef OPENSSL_NO_HEARTBEATS
-    /* Add Heartbeat extension if we've received one */
-    if (SSL_IS_DTLS(s) && (s->tlsext_heartbeat & SSL_DTLSEXT_HB_ENABLED)) {
-        if ((limit - ret - 4 - 1) < 0)
-            return NULL;
-        s2n(TLSEXT_TYPE_heartbeat, ret);
-        s2n(1, ret);
-        /*-
-         * Set mode:
-         * 1: peer may send requests
-         * 2: peer not allowed to send requests
-         */
-        if (s->tlsext_heartbeat & SSL_DTLSEXT_HB_DONT_RECV_REQUESTS)
-            *(ret++) = SSL_DTLSEXT_HB_DONT_SEND_REQUESTS;
-        else
-            *(ret++) = SSL_DTLSEXT_HB_ENABLED;
-
+        if (!WPACKET_memcpy(pkt, cryptopro_ext, sizeof(cryptopro_ext))) {
+            SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
     }
-#endif
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
     next_proto_neg_seen = s->s3->next_proto_neg_seen;
@@ -1586,18 +1544,20 @@ unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *buf,
                                               s->
                                               ctx->next_protos_advertised_cb_arg);
         if (r == SSL_TLSEXT_ERR_OK) {
-            if ((long)(limit - ret - 4 - npalen) < 0)
-                return NULL;
-            s2n(TLSEXT_TYPE_next_proto_neg, ret);
-            s2n(npalen, ret);
-            memcpy(ret, npa, npalen);
-            ret += npalen;
+            if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_next_proto_neg)
+                    || !WPACKET_sub_memcpy_u16(pkt, npa, npalen)) {
+                SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+                return 0;
+            }
             s->s3->next_proto_neg_seen = 1;
         }
     }
 #endif
-    if (!custom_ext_add(s, 1, &ret, limit, al))
-        return NULL;
+    if (!custom_ext_add(s, 1, pkt, al)) {
+        SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+        return 0;
+    }
+
     if (s->s3->flags & TLS1_FLAGS_ENCRYPT_THEN_MAC) {
         /*
          * Don't use encrypt_then_mac if AEAD or RC4 might want to disable
@@ -1609,36 +1569,41 @@ unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *buf,
             || s->s3->tmp.new_cipher->algorithm_enc == SSL_eGOST2814789CNT12)
             s->s3->flags &= ~TLS1_FLAGS_ENCRYPT_THEN_MAC;
         else {
-            s2n(TLSEXT_TYPE_encrypt_then_mac, ret);
-            s2n(0, ret);
+            if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_encrypt_then_mac)
+                    || !WPACKET_put_bytes_u16(pkt, 0)) {
+                SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+                return 0;
+            }
         }
     }
     if (s->s3->flags & TLS1_FLAGS_RECEIVED_EXTMS) {
-        s2n(TLSEXT_TYPE_extended_master_secret, ret);
-        s2n(0, ret);
+        if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_extended_master_secret)
+                || !WPACKET_put_bytes_u16(pkt, 0)) {
+            SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
     }
 
     if (s->s3->alpn_selected != NULL) {
-        const unsigned char *selected = s->s3->alpn_selected;
-        unsigned int len = s->s3->alpn_selected_len;
-
-        if ((long)(limit - ret - 4 - 2 - 1 - len) < 0)
-            return NULL;
-        s2n(TLSEXT_TYPE_application_layer_protocol_negotiation, ret);
-        s2n(3 + len, ret);
-        s2n(1 + len, ret);
-        *ret++ = len;
-        memcpy(ret, selected, len);
-        ret += len;
+        if (!WPACKET_put_bytes_u16(pkt,
+                    TLSEXT_TYPE_application_layer_protocol_negotiation)
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_start_sub_packet_u16(pkt)
+                || !WPACKET_sub_memcpy_u8(pkt, s->s3->alpn_selected,
+                                          s->s3->alpn_selected_len)
+                || !WPACKET_close(pkt)
+                || !WPACKET_close(pkt)) {
+            SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
     }
 
  done:
-
-    if ((extdatalen = ret - orig - 2) == 0)
-        return orig;
-
-    s2n(extdatalen, orig);
-    return ret;
+    if (!WPACKET_close(pkt)) {
+        SSLerr(SSL_F_SSL_ADD_SERVERHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
+        return 0;
+    }
+    return 1;
 }
 
 /*
@@ -1668,8 +1633,7 @@ static int tls1_alpn_handle_client_hello(SSL *s, PACKET *pkt, int *al)
     } while (PACKET_remaining(&protocol_list) != 0);
 
     if (!PACKET_memdup(&save_protocol_list,
-                       &s->s3->alpn_proposed,
-                       &s->s3->alpn_proposed_len)) {
+                       &s->s3->alpn_proposed, &s->s3->alpn_proposed_len)) {
         *al = TLS1_AD_INTERNAL_ERROR;
         return 0;
     }
@@ -1679,11 +1643,10 @@ static int tls1_alpn_handle_client_hello(SSL *s, PACKET *pkt, int *al)
 
 /*
  * Process the ALPN extension in a ClientHello.
- * ret: a pointer to the TLSEXT return value: SSL_TLSEXT_ERR_*
  * al: a pointer to the alert value to send in the event of a failure.
- * returns 1 on success, 0
+ * returns 1 on success, 0 on error.
  */
-static int tls1_alpn_handle_client_hello_late(SSL *s, int *ret, int *al)
+static int tls1_alpn_handle_client_hello_late(SSL *s, int *al)
 {
     const unsigned char *selected = NULL;
     unsigned char selected_len = 0;
@@ -1691,7 +1654,7 @@ static int tls1_alpn_handle_client_hello_late(SSL *s, int *ret, int *al)
     if (s->ctx->alpn_select_cb != NULL && s->s3->alpn_proposed != NULL) {
         int r = s->ctx->alpn_select_cb(s, &selected, &selected_len,
                                        s->s3->alpn_proposed,
-                                       s->s3->alpn_proposed_len,
+                                       (unsigned int)s->s3->alpn_proposed_len,
                                        s->ctx->alpn_select_cb_arg);
 
         if (r == SSL_TLSEXT_ERR_OK) {
@@ -1699,7 +1662,6 @@ static int tls1_alpn_handle_client_hello_late(SSL *s, int *ret, int *al)
             s->s3->alpn_selected = OPENSSL_memdup(selected, selected_len);
             if (s->s3->alpn_selected == NULL) {
                 *al = SSL_AD_INTERNAL_ERROR;
-                *ret = SSL_TLSEXT_ERR_ALERT_FATAL;
                 return 0;
             }
             s->s3->alpn_selected_len = selected_len;
@@ -1709,7 +1671,6 @@ static int tls1_alpn_handle_client_hello_late(SSL *s, int *ret, int *al)
 #endif
         } else {
             *al = SSL_AD_NO_APPLICATION_PROTOCOL;
-            *ret = SSL_TLSEXT_ERR_ALERT_FATAL;
             return 0;
         }
     }
@@ -1720,7 +1681,7 @@ static int tls1_alpn_handle_client_hello_late(SSL *s, int *ret, int *al)
 #ifndef OPENSSL_NO_EC
 /*-
  * ssl_check_for_safari attempts to fingerprint Safari using OS X
- * SecureTransport using the TLS extension block in |pkt|.
+ * SecureTransport using the TLS extension block in |hello|.
  * Safari, since 10.6, sends exactly these extensions, in this order:
  *   SNI,
  *   elliptic_curves
@@ -1731,7 +1692,7 @@ static int tls1_alpn_handle_client_hello_late(SSL *s, int *ret, int *al)
  * Sadly we cannot differentiate 10.6, 10.7 and 10.8.4 (which work), from
  * 10.8..10.8.3 (which don't work).
  */
-static void ssl_check_for_safari(SSL *s, const PACKET *pkt)
+static void ssl_check_for_safari(SSL *s, const CLIENTHELLO_MSG *hello)
 {
     unsigned int type;
     PACKET sni, tmppkt;
@@ -1763,7 +1724,7 @@ static void ssl_check_for_safari(SSL *s, const PACKET *pkt)
     /* Length of the common prefix (first two extensions). */
     static const size_t kSafariCommonExtensionsLength = 18;
 
-    tmppkt = *pkt;
+    tmppkt = hello->extensions;
 
     if (!PACKET_forward(&tmppkt, 2)
         || !PACKET_get_net_2(&tmppkt, &type)
@@ -1780,24 +1741,24 @@ static void ssl_check_for_safari(SSL *s, const PACKET *pkt)
     s->s3->is_probably_safari = PACKET_equal(&tmppkt, kSafariExtensionsBlock,
                                              ext_len);
 }
-#endif                         /* !OPENSSL_NO_EC */
+#endif                          /* !OPENSSL_NO_EC */
 
 /*
- * Parse ClientHello extensions and stash extension info in various parts of
- * the SSL object. Verify that there are no duplicate extensions.
+ * Loop through all remaining ClientHello extensions that we collected earlier
+ * and haven't already processed. For each one parse it and update the SSL
+ * object as required.
  *
  * Behaviour upon resumption is extension-specific. If the extension has no
  * effect during resumption, it is parsed (to verify its format) but otherwise
  * ignored.
  *
- * Consumes the entire packet in |pkt|. Returns 1 on success and 0 on failure.
+ * Returns 1 on success and 0 on failure.
  * Upon failure, sets |al| to the appropriate alert.
  */
-static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
+static int ssl_scan_clienthello_tlsext(SSL *s, CLIENTHELLO_MSG *hello, int *al)
 {
-    unsigned int type;
+    size_t loop;
     int renegotiate_seen = 0;
-    PACKET extensions;
 
     *al = SSL_AD_DECODE_ERROR;
     s->servername_done = 0;
@@ -1812,15 +1773,11 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
     OPENSSL_free(s->s3->alpn_proposed);
     s->s3->alpn_proposed = NULL;
     s->s3->alpn_proposed_len = 0;
-#ifndef OPENSSL_NO_HEARTBEATS
-    s->tlsext_heartbeat &= ~(SSL_DTLSEXT_HB_ENABLED |
-                             SSL_DTLSEXT_HB_DONT_SEND_REQUESTS);
-#endif
 
 #ifndef OPENSSL_NO_EC
     if (s->options & SSL_OP_SAFARI_ECDHE_ECDSA_BUG)
-        ssl_check_for_safari(s, pkt);
-# endif /* !OPENSSL_NO_EC */
+        ssl_check_for_safari(s, hello);
+#endif                          /* !OPENSSL_NO_EC */
 
     /* Clear any signature algorithms extension received */
     OPENSSL_free(s->s3->tmp.peer_sigalgs);
@@ -1834,32 +1791,23 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
 
     s->srtp_profile = NULL;
 
-    if (PACKET_remaining(pkt) == 0)
-        goto ri_check;
-
-    if (!PACKET_as_length_prefixed_2(pkt, &extensions))
-        return 0;
-
-    if (!tls1_check_duplicate_extensions(&extensions))
-        return 0;
-
     /*
      * We parse all extensions to ensure the ClientHello is well-formed but,
      * unless an extension specifies otherwise, we ignore extensions upon
      * resumption.
      */
-    while (PACKET_get_net_2(&extensions, &type)) {
-        PACKET extension;
-        if (!PACKET_get_length_prefixed_2(&extensions, &extension))
-            return 0;
+    for (loop = 0; loop < hello->num_extensions; loop++) {
+        RAW_EXTENSION *currext = &hello->pre_proc_exts[loop];
 
         if (s->tlsext_debug_cb)
-            s->tlsext_debug_cb(s, 0, type, PACKET_data(&extension),
-                               PACKET_remaining(&extension),
+            s->tlsext_debug_cb(s, 0, currext->type,
+                               PACKET_data(&currext->data),
+                               PACKET_remaining(&currext->data),
                                s->tlsext_debug_arg);
 
-        if (type == TLSEXT_TYPE_renegotiate) {
-            if (!ssl_parse_clienthello_renegotiate_ext(s, &extension, al))
+        if (currext->type == TLSEXT_TYPE_renegotiate) {
+            if (!ssl_parse_clienthello_renegotiate_ext(s,
+                    &currext->data, al))
                 return 0;
             renegotiate_seen = 1;
         } else if (s->version == SSL3_VERSION) {
@@ -1889,11 +1837,11 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
  *
  */
 
-        else if (type == TLSEXT_TYPE_server_name) {
+        else if (currext->type == TLSEXT_TYPE_server_name) {
             unsigned int servname_type;
             PACKET sni, hostname;
 
-            if (!PACKET_as_length_prefixed_2(&extension, &sni)
+            if (!PACKET_as_length_prefixed_2(&currext->data, &sni)
                 /* ServerNameList must be at least 1 byte long. */
                 || PACKET_remaining(&sni) == 0) {
                 return 0;
@@ -1945,10 +1893,10 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
             }
         }
 #ifndef OPENSSL_NO_SRP
-        else if (type == TLSEXT_TYPE_srp) {
+        else if (currext->type == TLSEXT_TYPE_srp) {
             PACKET srp_I;
 
-            if (!PACKET_as_length_prefixed_1(&extension, &srp_I))
+            if (!PACKET_as_length_prefixed_1(&currext->data, &srp_I))
                 return 0;
 
             if (PACKET_contains_zero_byte(&srp_I))
@@ -1966,11 +1914,11 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
 #endif
 
 #ifndef OPENSSL_NO_EC
-        else if (type == TLSEXT_TYPE_ec_point_formats) {
+        else if (currext->type == TLSEXT_TYPE_ec_point_formats) {
             PACKET ec_point_format_list;
 
-            if (!PACKET_as_length_prefixed_1(&extension,
-                                              &ec_point_format_list)
+            if (!PACKET_as_length_prefixed_1(&currext->data,
+                                             &ec_point_format_list)
                 || PACKET_remaining(&ec_point_format_list) == 0) {
                 return 0;
             }
@@ -1978,68 +1926,88 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
             if (!s->hit) {
                 if (!PACKET_memdup(&ec_point_format_list,
                                    &s->session->tlsext_ecpointformatlist,
-                                   &s->session->tlsext_ecpointformatlist_length)) {
+                                   &s->
+                                   session->tlsext_ecpointformatlist_length)) {
                     *al = TLS1_AD_INTERNAL_ERROR;
                     return 0;
                 }
             }
-        } else if (type == TLSEXT_TYPE_elliptic_curves) {
-            PACKET elliptic_curve_list;
-
-            /* Each NamedCurve is 2 bytes and we must have at least 1. */
-            if (!PACKET_as_length_prefixed_2(&extension,
-                                             &elliptic_curve_list)
-                || PACKET_remaining(&elliptic_curve_list) == 0
-                || (PACKET_remaining(&elliptic_curve_list) % 2) != 0) {
+        } else if (currext->type == TLSEXT_TYPE_supported_groups) {
+            PACKET supported_groups_list;
+
+            /* Each group is 2 bytes and we must have at least 1. */
+            if (!PACKET_as_length_prefixed_2(&currext->data,
+                                             &supported_groups_list)
+                || PACKET_remaining(&supported_groups_list) == 0
+                || (PACKET_remaining(&supported_groups_list) % 2) != 0) {
                 return 0;
             }
 
             if (!s->hit) {
-                if (!PACKET_memdup(&elliptic_curve_list,
-                                   &s->session->tlsext_ellipticcurvelist,
-                                   &s->session->tlsext_ellipticcurvelist_length)) {
+                if (!PACKET_memdup(&supported_groups_list,
+                                   &s->session->tlsext_supportedgroupslist,
+                                   &s->
+                                   session->tlsext_supportedgroupslist_length)) {
                     *al = TLS1_AD_INTERNAL_ERROR;
                     return 0;
                 }
             }
         }
-#endif                         /* OPENSSL_NO_EC */
-        else if (type == TLSEXT_TYPE_session_ticket) {
+#endif                          /* OPENSSL_NO_EC */
+        else if (currext->type == TLSEXT_TYPE_session_ticket) {
             if (s->tls_session_ticket_ext_cb &&
-                !s->tls_session_ticket_ext_cb(s, PACKET_data(&extension),
-                                              PACKET_remaining(&extension),
-                                              s->tls_session_ticket_ext_cb_arg)) {
+                !s->tls_session_ticket_ext_cb(s,
+                    PACKET_data(&currext->data),
+                    PACKET_remaining(&currext->data),
+                    s->tls_session_ticket_ext_cb_arg)) {
                 *al = TLS1_AD_INTERNAL_ERROR;
                 return 0;
             }
-        } else if (type == TLSEXT_TYPE_signature_algorithms) {
+        } else if (currext->type == TLSEXT_TYPE_signature_algorithms) {
             PACKET supported_sig_algs;
 
-            if (!PACKET_as_length_prefixed_2(&extension, &supported_sig_algs)
+            if (!PACKET_as_length_prefixed_2(&currext->data,
+                                             &supported_sig_algs)
                 || (PACKET_remaining(&supported_sig_algs) % 2) != 0
                 || PACKET_remaining(&supported_sig_algs) == 0) {
                 return 0;
             }
 
-            if  (!s->hit) {
+            if (!s->hit) {
                 if (!tls1_save_sigalgs(s, PACKET_data(&supported_sig_algs),
                                        PACKET_remaining(&supported_sig_algs))) {
                     return 0;
                 }
             }
-        } else if (type == TLSEXT_TYPE_status_request) {
-            if (!PACKET_get_1(&extension,
+        } else if (currext->type == TLSEXT_TYPE_status_request) {
+            if (!PACKET_get_1(&currext->data,
                               (unsigned int *)&s->tlsext_status_type)) {
                 return 0;
             }
-
 #ifndef OPENSSL_NO_OCSP
             if (s->tlsext_status_type == TLSEXT_STATUSTYPE_ocsp) {
                 const unsigned char *ext_data;
                 PACKET responder_id_list, exts;
-                if (!PACKET_get_length_prefixed_2(&extension, &responder_id_list))
+                if (!PACKET_get_length_prefixed_2
+                    (&currext->data, &responder_id_list))
                     return 0;
 
+                /*
+                 * We remove any OCSP_RESPIDs from a previous handshake
+                 * to prevent unbounded memory growth - CVE-2016-6304
+                 */
+                sk_OCSP_RESPID_pop_free(s->tlsext_ocsp_ids,
+                                        OCSP_RESPID_free);
+                if (PACKET_remaining(&responder_id_list) > 0) {
+                    s->tlsext_ocsp_ids = sk_OCSP_RESPID_new_null();
+                    if (s->tlsext_ocsp_ids == NULL) {
+                        *al = SSL_AD_INTERNAL_ERROR;
+                        return 0;
+                    }
+                } else {
+                    s->tlsext_ocsp_ids = NULL;
+                }
+
                 while (PACKET_remaining(&responder_id_list) > 0) {
                     OCSP_RESPID *id;
                     PACKET responder_id;
@@ -2051,16 +2019,10 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
                         return 0;
                     }
 
-                    if (s->tlsext_ocsp_ids == NULL
-                        && (s->tlsext_ocsp_ids =
-                            sk_OCSP_RESPID_new_null()) == NULL) {
-                        *al = SSL_AD_INTERNAL_ERROR;
-                        return 0;
-                    }
-
                     id_data = PACKET_data(&responder_id);
+                    /* TODO(size_t): Convert d2i_* to size_t */
                     id = d2i_OCSP_RESPID(NULL, &id_data,
-                                         PACKET_remaining(&responder_id));
+                                         (int)PACKET_remaining(&responder_id));
                     if (id == NULL)
                         return 0;
 
@@ -2077,7 +2039,8 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
                 }
 
                 /* Read in request_extensions */
-                if (!PACKET_as_length_prefixed_2(&extension, &exts))
+                if (!PACKET_as_length_prefixed_2(
+                        &currext->data, &exts))
                     return 0;
 
                 if (PACKET_remaining(&exts) > 0) {
@@ -2086,7 +2049,7 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
                                                X509_EXTENSION_free);
                     s->tlsext_ocsp_exts =
                         d2i_X509_EXTENSIONS(NULL, &ext_data,
-                                            PACKET_remaining(&exts));
+                                            (int)PACKET_remaining(&exts));
                     if (s->tlsext_ocsp_exts == NULL
                         || ext_data != PACKET_end(&exts)) {
                         return 0;
@@ -2101,32 +2064,9 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
                 s->tlsext_status_type = -1;
             }
         }
-#ifndef OPENSSL_NO_HEARTBEATS
-        else if (SSL_IS_DTLS(s) && type == TLSEXT_TYPE_heartbeat) {
-            unsigned int hbtype;
-
-            if (!PACKET_get_1(&extension, &hbtype)
-                    || PACKET_remaining(&extension)) {
-                *al = SSL_AD_DECODE_ERROR;
-                return 0;
-            }
-            switch (hbtype) {
-            case 0x01:         /* Client allows us to send HB requests */
-                s->tlsext_heartbeat |= SSL_DTLSEXT_HB_ENABLED;
-                break;
-            case 0x02:         /* Client doesn't accept HB requests */
-                s->tlsext_heartbeat |= SSL_DTLSEXT_HB_ENABLED;
-                s->tlsext_heartbeat |= SSL_DTLSEXT_HB_DONT_SEND_REQUESTS;
-                break;
-            default:
-                *al = SSL_AD_ILLEGAL_PARAMETER;
-                return 0;
-            }
-        }
-#endif
 #ifndef OPENSSL_NO_NEXTPROTONEG
-        else if (type == TLSEXT_TYPE_next_proto_neg &&
-                 s->s3->tmp.finish_md_len == 0) {
+        else if (currext->type == TLSEXT_TYPE_next_proto_neg
+                 && s->s3->tmp.finish_md_len == 0) {
             /*-
              * We shouldn't accept this extension on a
              * renegotiation.
@@ -2148,25 +2088,29 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
         }
 #endif
 
-        else if (type == TLSEXT_TYPE_application_layer_protocol_negotiation &&
-                 s->s3->tmp.finish_md_len == 0) {
-            if (!tls1_alpn_handle_client_hello(s, &extension, al))
+        else if (currext->type
+                     == TLSEXT_TYPE_application_layer_protocol_negotiation
+                 && s->s3->tmp.finish_md_len == 0) {
+            if (!tls1_alpn_handle_client_hello(s,
+                    &currext->data, al))
                 return 0;
         }
 
         /* session ticket processed earlier */
 #ifndef OPENSSL_NO_SRTP
         else if (SSL_IS_DTLS(s) && SSL_get_srtp_profiles(s)
-                 && type == TLSEXT_TYPE_use_srtp) {
-            if (ssl_parse_clienthello_use_srtp_ext(s, &extension, al))
+                 && currext->type == TLSEXT_TYPE_use_srtp) {
+            if (ssl_parse_clienthello_use_srtp_ext(s,
+                    &currext->data, al))
                 return 0;
         }
 #endif
-        else if (type == TLSEXT_TYPE_encrypt_then_mac)
+        else if (currext->type == TLSEXT_TYPE_encrypt_then_mac
+                 && !(s->options & SSL_OP_NO_ENCRYPT_THEN_MAC))
             s->s3->flags |= TLS1_FLAGS_ENCRYPT_THEN_MAC;
         /*
          * Note: extended master secret extension handled in
-         * tls_check_serverhello_tlsext_early()
+         * tls_check_client_ems_support()
          */
 
         /*
@@ -2177,20 +2121,13 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
          * ServerHello may be later returned.
          */
         else if (!s->hit) {
-            if (custom_ext_parse(s, 1, type, PACKET_data(&extension),
-                                 PACKET_remaining(&extension), al) <= 0)
+            if (custom_ext_parse(s, 1, currext->type,
+                    PACKET_data(&currext->data),
+                    PACKET_remaining(&currext->data), al) <= 0)
                 return 0;
         }
     }
 
-    if (PACKET_remaining(pkt) != 0) {
-        /* tls1_check_duplicate_extensions should ensure this never happens. */
-        *al = SSL_AD_INTERNAL_ERROR;
-        return 0;
-    }
-
- ri_check:
-
     /* Need RI if renegotiating */
 
     if (!renegotiate_seen && s->renegotiate &&
@@ -2210,11 +2147,11 @@ static int ssl_scan_clienthello_tlsext(SSL *s, PACKET *pkt, int *al)
     return 1;
 }
 
-int ssl_parse_clienthello_tlsext(SSL *s, PACKET *pkt)
+int ssl_parse_clienthello_tlsext(SSL *s, CLIENTHELLO_MSG *hello)
 {
     int al = -1;
     custom_ext_init(&s->cert->srv_ext);
-    if (ssl_scan_clienthello_tlsext(s, pkt, &al) <= 0) {
+    if (ssl_scan_clienthello_tlsext(s, hello, &al) <= 0) {
         ssl3_send_alert(s, SSL3_AL_FATAL, al);
         return 0;
     }
@@ -2237,7 +2174,7 @@ static char ssl_next_proto_validate(PACKET *pkt)
 
     while (PACKET_remaining(pkt)) {
         if (!PACKET_get_length_prefixed_1(pkt, &tmp_protocol)
-                || PACKET_remaining(&tmp_protocol) == 0)
+            || PACKET_remaining(&tmp_protocol) == 0)
             return 0;
     }
 
@@ -2258,10 +2195,6 @@ static int ssl_scan_serverhello_tlsext(SSL *s, PACKET *pkt, int *al)
 
     OPENSSL_free(s->s3->alpn_selected);
     s->s3->alpn_selected = NULL;
-#ifndef OPENSSL_NO_HEARTBEATS
-    s->tlsext_heartbeat &= ~(SSL_DTLSEXT_HB_ENABLED |
-                             SSL_DTLSEXT_HB_DONT_SEND_REQUESTS);
-#endif
 
     s->s3->flags &= ~TLS1_FLAGS_ENCRYPT_THEN_MAC;
 
@@ -2285,7 +2218,7 @@ static int ssl_scan_serverhello_tlsext(SSL *s, PACKET *pkt, int *al)
         PACKET spkt;
 
         if (!PACKET_get_sub_packet(pkt, &spkt, size)
-                ||  !PACKET_peek_bytes(&spkt, &data, size))
+            || !PACKET_peek_bytes(&spkt, &data, size))
             goto ri_check;
 
         if (s->tlsext_debug_cb)
@@ -2307,7 +2240,7 @@ static int ssl_scan_serverhello_tlsext(SSL *s, PACKET *pkt, int *al)
         else if (type == TLSEXT_TYPE_ec_point_formats) {
             unsigned int ecpointformatlist_length;
             if (!PACKET_get_1(&spkt, &ecpointformatlist_length)
-                    || ecpointformatlist_length != size - 1) {
+                || ecpointformatlist_length != size - 1) {
                 *al = TLS1_AD_DECODE_ERROR;
                 return 0;
             }
@@ -2330,7 +2263,7 @@ static int ssl_scan_serverhello_tlsext(SSL *s, PACKET *pkt, int *al)
 
             }
         }
-#endif                         /* OPENSSL_NO_EC */
+#endif                          /* OPENSSL_NO_EC */
 
         else if (type == TLSEXT_TYPE_session_ticket) {
             if (s->tls_session_ticket_ext_cb &&
@@ -2345,8 +2278,7 @@ static int ssl_scan_serverhello_tlsext(SSL *s, PACKET *pkt, int *al)
                 return 0;
             }
             s->tlsext_ticket_expected = 1;
-        }
-        else if (type == TLSEXT_TYPE_status_request) {
+        } else if (type == TLSEXT_TYPE_status_request) {
             /*
              * MUST be empty and only sent if we've requested a status
              * request message.
@@ -2397,14 +2329,19 @@ static int ssl_scan_serverhello_tlsext(SSL *s, PACKET *pkt, int *al)
                 *al = TLS1_AD_DECODE_ERROR;
                 return 0;
             }
-            if (s->
-                ctx->next_proto_select_cb(s, &selected, &selected_len, data,
-                                          size,
-                                          s->ctx->next_proto_select_cb_arg) !=
+            if (s->ctx->next_proto_select_cb(s, &selected, &selected_len, data,
+                                             size,
+                                             s->
+                                             ctx->next_proto_select_cb_arg) !=
                 SSL_TLSEXT_ERR_OK) {
                 *al = TLS1_AD_INTERNAL_ERROR;
                 return 0;
             }
+            /*
+             * Could be non-NULL if server has sent multiple NPN extensions in
+             * a single Serverhello
+             */
+            OPENSSL_free(s->next_proto_negotiated);
             s->next_proto_negotiated = OPENSSL_malloc(selected_len);
             if (s->next_proto_negotiated == NULL) {
                 *al = TLS1_AD_INTERNAL_ERROR;
@@ -2430,9 +2367,8 @@ static int ssl_scan_serverhello_tlsext(SSL *s, PACKET *pkt, int *al)
              *   uint8 proto[proto_length];
              */
             if (!PACKET_get_net_2(&spkt, &len)
-                    || PACKET_remaining(&spkt) != len
-                    || !PACKET_get_1(&spkt, &len)
-                    || PACKET_remaining(&spkt) != len) {
+                || PACKET_remaining(&spkt) != len || !PACKET_get_1(&spkt, &len)
+                || PACKET_remaining(&spkt) != len) {
                 *al = TLS1_AD_DECODE_ERROR;
                 return 0;
             }
@@ -2448,27 +2384,6 @@ static int ssl_scan_serverhello_tlsext(SSL *s, PACKET *pkt, int *al)
             }
             s->s3->alpn_selected_len = len;
         }
-#ifndef OPENSSL_NO_HEARTBEATS
-        else if (SSL_IS_DTLS(s) && type == TLSEXT_TYPE_heartbeat) {
-            unsigned int hbtype;
-            if (!PACKET_get_1(&spkt, &hbtype)) {
-                *al = SSL_AD_DECODE_ERROR;
-                return 0;
-            }
-            switch (hbtype) {
-            case 0x01:         /* Server allows us to send HB requests */
-                s->tlsext_heartbeat |= SSL_DTLSEXT_HB_ENABLED;
-                break;
-            case 0x02:         /* Server doesn't accept HB requests */
-                s->tlsext_heartbeat |= SSL_DTLSEXT_HB_ENABLED;
-                s->tlsext_heartbeat |= SSL_DTLSEXT_HB_DONT_SEND_REQUESTS;
-                break;
-            default:
-                *al = SSL_AD_ILLEGAL_PARAMETER;
-                return 0;
-            }
-        }
-#endif
 #ifndef OPENSSL_NO_SRTP
         else if (SSL_IS_DTLS(s) && type == TLSEXT_TYPE_use_srtp) {
             if (ssl_parse_serverhello_use_srtp_ext(s, &spkt, al))
@@ -2477,11 +2392,11 @@ static int ssl_scan_serverhello_tlsext(SSL *s, PACKET *pkt, int *al)
 #endif
         else if (type == TLSEXT_TYPE_encrypt_then_mac) {
             /* Ignore if inappropriate ciphersuite */
-            if (s->s3->tmp.new_cipher->algorithm_mac != SSL_AEAD
+            if (!(s->options & SSL_OP_NO_ENCRYPT_THEN_MAC) &&
+                s->s3->tmp.new_cipher->algorithm_mac != SSL_AEAD
                 && s->s3->tmp.new_cipher->algorithm_enc != SSL_RC4)
                 s->s3->flags |= TLS1_FLAGS_ENCRYPT_THEN_MAC;
-        }
-        else if (type == TLSEXT_TYPE_extended_master_secret) {
+        } else if (type == TLSEXT_TYPE_extended_master_secret) {
             s->s3->flags |= TLS1_FLAGS_RECEIVED_EXTMS;
             if (!s->hit)
                 s->session->flags |= SSL_SESS_FLAG_EXTMS;
@@ -2502,7 +2417,8 @@ static int ssl_scan_serverhello_tlsext(SSL *s, PACKET *pkt, int *al)
     if (!s->hit && tlsext_servername == 1) {
         if (s->tlsext_hostname) {
             if (s->session->tlsext_hostname == NULL) {
-                s->session->tlsext_hostname = OPENSSL_strdup(s->tlsext_hostname);
+                s->session->tlsext_hostname =
+                    OPENSSL_strdup(s->tlsext_hostname);
                 if (!s->session->tlsext_hostname) {
                     *al = SSL_AD_UNRECOGNIZED_NAME;
                     return 0;
@@ -2541,7 +2457,7 @@ static int ssl_scan_serverhello_tlsext(SSL *s, PACKET *pkt, int *al)
             *al = SSL_AD_HANDSHAKE_FAILURE;
             SSLerr(SSL_F_SSL_SCAN_SERVERHELLO_TLSEXT, SSL_R_INCONSISTENT_EXTMS);
             return 0;
-            }
+        }
     }
 
     return 1;
@@ -2600,6 +2516,7 @@ static int ssl_check_clienthello_tlsext_early(SSL *s)
         return 1;
     }
 }
+
 /* Initialise digests to default values */
 void ssl_set_default_md(SSL *s)
 {
@@ -2649,7 +2566,7 @@ int tls1_set_server_sigalgs(SSL *s)
         /* Fatal error is no shared signature algorithms */
         if (!s->cert->shared_sigalgs) {
             SSLerr(SSL_F_TLS1_SET_SERVER_SIGALGS,
-                   SSL_R_NO_SHARED_SIGATURE_ALGORITHMS);
+                   SSL_R_NO_SHARED_SIGNATURE_ALGORITHMS);
             al = SSL_AD_ILLEGAL_PARAMETER;
             goto err;
         }
@@ -2662,10 +2579,13 @@ int tls1_set_server_sigalgs(SSL *s)
     return 0;
 }
 
-int ssl_check_clienthello_tlsext_late(SSL *s)
+/*
+ * Upon success, returns 1.
+ * Upon failure, returns 0 and sets |al| to the appropriate fatal alert.
+ */
+int ssl_check_clienthello_tlsext_late(SSL *s, int *al)
 {
-    int ret = SSL_TLSEXT_ERR_OK;
-    int al = SSL_AD_INTERNAL_ERROR;
+    s->tlsext_status_expected = 0;
 
     /*
      * If status request then ask callback what to do. Note: this must be
@@ -2674,58 +2594,41 @@ int ssl_check_clienthello_tlsext_late(SSL *s)
      * influence which certificate is sent
      */
     if ((s->tlsext_status_type != -1) && s->ctx && s->ctx->tlsext_status_cb) {
-        int r;
+        int ret;
         CERT_PKEY *certpkey;
         certpkey = ssl_get_server_send_pkey(s);
         /* If no certificate can't return certificate status */
-        if (certpkey == NULL) {
-            s->tlsext_status_expected = 0;
-            return 1;
-        }
-        /*
-         * Set current certificate to one we will use so SSL_get_certificate
-         * et al can pick it up.
-         */
-        s->cert->key = certpkey;
-        r = s->ctx->tlsext_status_cb(s, s->ctx->tlsext_status_arg);
-        switch (r) {
-            /* We don't want to send a status request response */
-        case SSL_TLSEXT_ERR_NOACK:
-            s->tlsext_status_expected = 0;
-            break;
-            /* status request response should be sent */
-        case SSL_TLSEXT_ERR_OK:
-            if (s->tlsext_ocsp_resp)
-                s->tlsext_status_expected = 1;
-            else
+        if (certpkey != NULL) {
+            /*
+             * Set current certificate to one we will use so SSL_get_certificate
+             * et al can pick it up.
+             */
+            s->cert->key = certpkey;
+            ret = s->ctx->tlsext_status_cb(s, s->ctx->tlsext_status_arg);
+            switch (ret) {
+                /* We don't want to send a status request response */
+            case SSL_TLSEXT_ERR_NOACK:
                 s->tlsext_status_expected = 0;
-            break;
-            /* something bad happened */
-        case SSL_TLSEXT_ERR_ALERT_FATAL:
-            ret = SSL_TLSEXT_ERR_ALERT_FATAL;
-            al = SSL_AD_INTERNAL_ERROR;
-            goto err;
+                break;
+                /* status request response should be sent */
+            case SSL_TLSEXT_ERR_OK:
+                if (s->tlsext_ocsp_resp)
+                    s->tlsext_status_expected = 1;
+                break;
+                /* something bad happened */
+            case SSL_TLSEXT_ERR_ALERT_FATAL:
+            default:
+                *al = SSL_AD_INTERNAL_ERROR;
+                return 0;
+            }
         }
-    } else
-        s->tlsext_status_expected = 0;
-
-    if (!tls1_alpn_handle_client_hello_late(s, &ret, &al)) {
-        goto err;
     }
 
- err:
-    switch (ret) {
-    case SSL_TLSEXT_ERR_ALERT_FATAL:
-        ssl3_send_alert(s, SSL3_AL_FATAL, al);
-        return -1;
-
-    case SSL_TLSEXT_ERR_ALERT_WARNING:
-        ssl3_send_alert(s, SSL3_AL_WARNING, al);
-        return 1;
-
-    default:
-        return 1;
+    if (!tls1_alpn_handle_client_hello_late(s, al)) {
+        return 0;
     }
+
+    return 1;
 }
 
 int ssl_check_serverhello_tlsext(SSL *s)
@@ -2764,7 +2667,7 @@ int ssl_check_serverhello_tlsext(SSL *s)
         }
     }
     ret = SSL_TLSEXT_ERR_OK;
-#endif                         /* OPENSSL_NO_EC */
+#endif                          /* OPENSSL_NO_EC */
 
     if (s->ctx != NULL && s->ctx->tlsext_servername_callback != 0)
         ret =
@@ -2783,7 +2686,7 @@ int ssl_check_serverhello_tlsext(SSL *s)
      */
     OPENSSL_free(s->tlsext_ocsp_resp);
     s->tlsext_ocsp_resp = NULL;
-    s->tlsext_ocsp_resplen = -1;
+    s->tlsext_ocsp_resplen = 0;
 
     switch (ret) {
     case SSL_TLSEXT_ERR_ALERT_FATAL:
@@ -2818,16 +2721,33 @@ int ssl_parse_serverhello_tlsext(SSL *s, PACKET *pkt)
     return 1;
 }
 
-/*-
- * Since the server cache lookup is done early on in the processing of the
- * ClientHello and other operations depend on the result some extensions
- * need to be handled at the same time.
+/*
+ * Given a list of extensions that we collected earlier, find one of a given
+ * type and return it.
  *
- * Two extensions are currently handled, session ticket and extended master
- * secret.
+ * |exts| is the set of extensions previously collected.
+ * |numexts| is the number of extensions that we have.
+ * |type| the type of the extension that we are looking for.
  *
- *   session_id: ClientHello session ID.
- *   ext: ClientHello extensions (including length prefix)
+ * Returns a pointer to the found RAW_EXTENSION data, or NULL if not found.
+ */
+RAW_EXTENSION *tls_get_extension_by_type(RAW_EXTENSION *exts, size_t numexts,
+                                         unsigned int type)
+{
+    size_t loop;
+
+    for (loop = 0; loop < numexts; loop++) {
+        if (exts[loop].type == type)
+            return &exts[loop];
+    }
+
+    return NULL;
+}
+
+/*-
+ * Gets the ticket information supplied by the client if any.
+ *
+ *   hello: The parsed ClientHello data
  *   ret: (output) on return, if a ticket was decrypted, then this is set to
  *       point to the resulting session.
  *
@@ -2851,116 +2771,106 @@ int ssl_parse_serverhello_tlsext(SSL *s, PACKET *pkt)
  *   a session ticket or we couldn't use the one it gave us, or if
  *   s->ctx->tlsext_ticket_key_cb asked to renew the client's ticket.
  *   Otherwise, s->tlsext_ticket_expected is set to 0.
- *
- *   For extended master secret flag is set if the extension is present.
- *
  */
-int tls_check_serverhello_tlsext_early(SSL *s, const PACKET *ext,
-                                       const PACKET *session_id,
-                                       SSL_SESSION **ret)
+int tls_get_ticket_from_client(SSL *s, CLIENTHELLO_MSG *hello,
+                               SSL_SESSION **ret)
 {
-    unsigned int i;
-    PACKET local_ext = *ext;
-    int retv = -1;
-
-    int have_ticket = 0;
-    int use_ticket = tls_use_ticket(s);
+    int retv;
+    const unsigned char *etick;
+    size_t size;
+    RAW_EXTENSION *ticketext;
 
     *ret = NULL;
     s->tlsext_ticket_expected = 0;
-    s->s3->flags &= ~TLS1_FLAGS_RECEIVED_EXTMS;
 
     /*
      * If tickets disabled behave as if no ticket present to permit stateful
      * resumption.
      */
-    if ((s->version <= SSL3_VERSION))
+    if (s->version <= SSL3_VERSION || !tls_use_ticket(s))
         return 0;
 
-    if (!PACKET_get_net_2(&local_ext, &i)) {
-        retv = 0;
-        goto end;
+    ticketext = tls_get_extension_by_type(hello->pre_proc_exts,
+                                          hello->num_extensions,
+                                          TLSEXT_TYPE_session_ticket);
+    if (ticketext == NULL)
+        return 0;
+
+    size = PACKET_remaining(&ticketext->data);
+    if (size == 0) {
+        /*
+         * The client will accept a ticket but doesn't currently have
+         * one.
+         */
+        s->tlsext_ticket_expected = 1;
+        return 1;
     }
-    while (PACKET_remaining(&local_ext) >= 4) {
-        unsigned int type, size;
+    if (s->tls_session_secret_cb) {
+        /*
+         * Indicate that the ticket couldn't be decrypted rather than
+         * generating the session from ticket now, trigger
+         * abbreviated handshake based on external mechanism to
+         * calculate the master secret later.
+         */
+        return 2;
+    }
+    if (!PACKET_get_bytes(&ticketext->data, &etick, size)) {
+        /* Shouldn't ever happen */
+        return -1;
+    }
+    retv = tls_decrypt_ticket(s, etick, size, hello->session_id,
+                           hello->session_id_len, ret);
+    switch (retv) {
+    case 2:            /* ticket couldn't be decrypted */
+        s->tlsext_ticket_expected = 1;
+        return 2;
 
-        if (!PACKET_get_net_2(&local_ext, &type)
-                || !PACKET_get_net_2(&local_ext, &size)) {
-            /* Shouldn't ever happen */
-            retv = -1;
-            goto end;
-        }
-        if (PACKET_remaining(&local_ext) < size) {
-            retv = 0;
-            goto end;
-        }
-        if (type == TLSEXT_TYPE_session_ticket && use_ticket) {
-            int r;
-            const unsigned char *etick;
+    case 3:            /* ticket was decrypted */
+        return 3;
 
-            /* Duplicate extension */
-            if (have_ticket != 0) {
-                retv = -1;
-                goto end;
-            }
-            have_ticket = 1;
+    case 4:            /* ticket decrypted but need to renew */
+        s->tlsext_ticket_expected = 1;
+        return 3;
 
-            if (size == 0) {
-                /*
-                 * The client will accept a ticket but doesn't currently have
-                 * one.
-                 */
-                s->tlsext_ticket_expected = 1;
-                retv = 1;
-                continue;
-            }
-            if (s->tls_session_secret_cb) {
-                /*
-                 * Indicate that the ticket couldn't be decrypted rather than
-                 * generating the session from ticket now, trigger
-                 * abbreviated handshake based on external mechanism to
-                 * calculate the master secret later.
-                 */
-                retv = 2;
-                continue;
-            }
-            if (!PACKET_get_bytes(&local_ext, &etick, size)) {
-                /* Shouldn't ever happen */
-                retv = -1;
-                goto end;
-            }
-            r = tls_decrypt_ticket(s, etick, size, PACKET_data(session_id),
-                                   PACKET_remaining(session_id), ret);
-            switch (r) {
-            case 2:            /* ticket couldn't be decrypted */
-                s->tlsext_ticket_expected = 1;
-                retv = 2;
-                break;
-            case 3:            /* ticket was decrypted */
-                retv = r;
-                break;
-            case 4:            /* ticket decrypted but need to renew */
-                s->tlsext_ticket_expected = 1;
-                retv = 3;
-                break;
-            default:           /* fatal error */
-                retv = -1;
-                break;
-            }
-            continue;
-        } else {
-            if (type == TLSEXT_TYPE_extended_master_secret)
-                s->s3->flags |= TLS1_FLAGS_RECEIVED_EXTMS;
-            if (!PACKET_forward(&local_ext, size)) {
-                retv = -1;
-                goto end;
-            }
-        }
+    default:           /* fatal error */
+        return -1;
     }
-    if (have_ticket == 0)
-        retv = 0;
-end:
-    return retv;
+}
+
+/*
+ * Sets the extended master secret flag if the extension is present in the
+ * ClientHello
+ * Returns:
+ *  1 on success
+ *  0 on error
+ */
+int tls_check_client_ems_support(SSL *s, const CLIENTHELLO_MSG *hello)
+{
+    RAW_EXTENSION *emsext;
+
+    s->s3->flags &= ~TLS1_FLAGS_RECEIVED_EXTMS;
+
+    if (s->version <= SSL3_VERSION)
+        return 1;
+
+    emsext = tls_get_extension_by_type(hello->pre_proc_exts,
+                                       hello->num_extensions,
+                                       TLSEXT_TYPE_extended_master_secret);
+
+    /*
+     * No extensions is a success - we have successfully discovered that the
+     * client doesn't support EMS.
+     */
+    if (emsext == NULL)
+        return 1;
+
+    /* The extensions must always be empty */
+    if (PACKET_remaining(&emsext->data) != 0)
+        return 0;
+
+    s->s3->flags |= TLS1_FLAGS_RECEIVED_EXTMS;
+
+    return 1;
 }
 
 /*-
@@ -2981,20 +2891,19 @@ end:
  *    4: same as 3, but the ticket needs to be renewed.
  */
 static int tls_decrypt_ticket(SSL *s, const unsigned char *etick,
-                              int eticklen, const unsigned char *sess_id,
-                              int sesslen, SSL_SESSION **psess)
+                              size_t eticklen, const unsigned char *sess_id,
+                              size_t sesslen, SSL_SESSION **psess)
 {
     SSL_SESSION *sess;
     unsigned char *sdec;
     const unsigned char *p;
-    int slen, mlen, renew_ticket = 0, ret = -1;
+    int slen, renew_ticket = 0, ret = -1, declen;
+    size_t mlen;
     unsigned char tick_hmac[EVP_MAX_MD_SIZE];
     HMAC_CTX *hctx = NULL;
     EVP_CIPHER_CTX *ctx;
     SSL_CTX *tctx = s->initial_ctx;
-    /* Need at least keyname + iv + some encrypted data */
-    if (eticklen < 48)
-        return 2;
+
     /* Initialize session ticket encryption and HMAC contexts */
     hctx = HMAC_CTX_new();
     if (hctx == NULL)
@@ -3026,24 +2935,31 @@ static int tls_decrypt_ticket(SSL *s, const unsigned char *etick,
         if (HMAC_Init_ex(hctx, tctx->tlsext_tick_hmac_key,
                          sizeof(tctx->tlsext_tick_hmac_key),
                          EVP_sha256(), NULL) <= 0
-                || EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL,
-                                      tctx->tlsext_tick_aes_key,
-                                      etick + sizeof(tctx->tlsext_tick_key_name)) <= 0) {
+            || EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL,
+                                  tctx->tlsext_tick_aes_key,
+                                  etick + sizeof(tctx->tlsext_tick_key_name)) <=
+            0) {
             goto err;
-       }
+        }
     }
     /*
      * Attempt to process session ticket, first conduct sanity and integrity
      * checks on ticket.
      */
     mlen = HMAC_size(hctx);
-    if (mlen < 0) {
+    if (mlen == 0) {
+        goto err;
+    }
+    /* Sanity check ticket length: must exceed keyname + IV + HMAC */
+    if (eticklen <=
+        TLSEXT_KEYNAME_LENGTH + EVP_CIPHER_CTX_iv_length(ctx) + mlen) {
+        ret = 2;
         goto err;
     }
     eticklen -= mlen;
     /* Check HMAC of encrypted ticket */
     if (HMAC_Update(hctx, etick, eticklen) <= 0
-            || HMAC_Final(hctx, tick_hmac, NULL) <= 0) {
+        || HMAC_Final(hctx, tick_hmac, NULL) <= 0) {
         goto err;
     }
     HMAC_CTX_free(hctx);
@@ -3056,18 +2972,18 @@ static int tls_decrypt_ticket(SSL *s, const unsigned char *etick,
     p = etick + 16 + EVP_CIPHER_CTX_iv_length(ctx);
     eticklen -= 16 + EVP_CIPHER_CTX_iv_length(ctx);
     sdec = OPENSSL_malloc(eticklen);
-    if (sdec == NULL
-            || EVP_DecryptUpdate(ctx, sdec, &slen, p, eticklen) <= 0) {
+    if (sdec == NULL || EVP_DecryptUpdate(ctx, sdec, &slen, p,
+                                          (int)eticklen) <= 0) {
         EVP_CIPHER_CTX_free(ctx);
         OPENSSL_free(sdec);
         return -1;
     }
-    if (EVP_DecryptFinal(ctx, sdec + slen, &mlen) <= 0) {
+    if (EVP_DecryptFinal(ctx, sdec + slen, &declen) <= 0) {
         EVP_CIPHER_CTX_free(ctx);
         OPENSSL_free(sdec);
         return 2;
     }
-    slen += mlen;
+    slen += declen;
     EVP_CIPHER_CTX_free(ctx);
     ctx = NULL;
     p = sdec;
@@ -3095,7 +3011,7 @@ static int tls_decrypt_ticket(SSL *s, const unsigned char *etick,
      * For session parse failure, indicate that we need to send a new ticket.
      */
     return 2;
-err:
+ err:
     EVP_CIPHER_CTX_free(ctx);
     HMAC_CTX_free(hctx);
     return ret;
@@ -3149,11 +3065,11 @@ static int tls12_find_nid(int id, const tls12_lookup *table, size_t tlen)
     return NID_undef;
 }
 
-int tls12_get_sigandhash(unsigned char *p, const EVP_PKEY *pk,
-                         const EVP_MD *md)
+int tls12_get_sigandhash(WPACKET *pkt, const EVP_PKEY *pk, const EVP_MD *md)
 {
     int sig_id, md_id;
-    if (!md)
+
+    if (md == NULL)
         return 0;
     md_id = tls12_find_id(EVP_MD_type(md), tls12_md, OSSL_NELEM(tls12_md));
     if (md_id == -1)
@@ -3161,8 +3077,9 @@ int tls12_get_sigandhash(unsigned char *p, const EVP_PKEY *pk,
     sig_id = tls12_get_sigid(pk);
     if (sig_id == -1)
         return 0;
-    p[0] = (unsigned char)md_id;
-    p[1] = (unsigned char)sig_id;
+    if (!WPACKET_put_bytes_u8(pkt, md_id) || !WPACKET_put_bytes_u8(pkt, sig_id))
+        return 0;
+
     return 1;
 }
 
@@ -3185,9 +3102,11 @@ static const tls12_hash_info tls12_md_info[] = {
     {NID_sha256, 128, SSL_MD_SHA256_IDX, TLSEXT_hash_sha256},
     {NID_sha384, 192, SSL_MD_SHA384_IDX, TLSEXT_hash_sha384},
     {NID_sha512, 256, SSL_MD_SHA512_IDX, TLSEXT_hash_sha512},
-    {NID_id_GostR3411_94,       128, SSL_MD_GOST94_IDX, TLSEXT_hash_gostr3411},
-    {NID_id_GostR3411_2012_256, 128, SSL_MD_GOST12_256_IDX, TLSEXT_hash_gostr34112012_256},
-    {NID_id_GostR3411_2012_512, 256, SSL_MD_GOST12_512_IDX, TLSEXT_hash_gostr34112012_512},
+    {NID_id_GostR3411_94, 128, SSL_MD_GOST94_IDX, TLSEXT_hash_gostr3411},
+    {NID_id_GostR3411_2012_256, 128, SSL_MD_GOST12_256_IDX,
+     TLSEXT_hash_gostr34112012_256},
+    {NID_id_GostR3411_2012_512, 256, SSL_MD_GOST12_512_IDX,
+     TLSEXT_hash_gostr34112012_512},
 };
 
 static const tls12_hash_info *tls12_get_hash_info(unsigned char hash_alg)
@@ -3196,8 +3115,7 @@ static const tls12_hash_info *tls12_get_hash_info(unsigned char hash_alg)
     if (hash_alg == 0)
         return NULL;
 
-    for (i=0; i < OSSL_NELEM(tls12_md_info); i++)
-    {
+    for (i = 0; i < OSSL_NELEM(tls12_md_info); i++) {
         if (tls12_md_info[i].tlsext_hash == hash_alg)
             return tls12_md_info + i;
     }
@@ -3231,7 +3149,7 @@ static int tls12_get_pkey_idx(unsigned char sig_alg)
     case TLSEXT_signature_ecdsa:
         return SSL_PKEY_ECC;
 #endif
-# ifndef OPENSSL_NO_GOST
+#ifndef OPENSSL_NO_GOST
     case TLSEXT_signature_gostr34102001:
         return SSL_PKEY_GOST01;
 
@@ -3240,7 +3158,7 @@ static int tls12_get_pkey_idx(unsigned char sig_alg)
 
     case TLSEXT_signature_gostr34102012_512:
         return SSL_PKEY_GOST12_512;
-# endif
+#endif
     }
     return -1;
 }
@@ -3264,8 +3182,7 @@ static void tls1_lookup_sigalg(int *phash_nid, int *psign_nid,
     }
     if (psignhash_nid) {
         if (sign_nid == NID_undef || hash_nid == NID_undef
-                || OBJ_find_sigid_by_algs(psignhash_nid, hash_nid,
-                                          sign_nid) <= 0)
+            || OBJ_find_sigid_by_algs(psignhash_nid, hash_nid, sign_nid) <= 0)
             *psignhash_nid = NID_undef;
     }
 }
@@ -3331,24 +3248,25 @@ void ssl_set_sig_mask(uint32_t *pmask_a, SSL *s, int op)
         *pmask_a |= SSL_aECDSA;
 }
 
-size_t tls12_copy_sigalgs(SSL *s, unsigned char *out,
-                          const unsigned char *psig, size_t psiglen)
+int tls12_copy_sigalgs(SSL *s, WPACKET *pkt,
+                       const unsigned char *psig, size_t psiglen)
 {
-    unsigned char *tmpout = out;
     size_t i;
+
     for (i = 0; i < psiglen; i += 2, psig += 2) {
         if (tls12_sigalg_allowed(s, SSL_SECOP_SIGALG_SUPPORTED, psig)) {
-            *tmpout++ = psig[0];
-            *tmpout++ = psig[1];
+            if (!WPACKET_put_bytes_u8(pkt, psig[0])
+                    || !WPACKET_put_bytes_u8(pkt, psig[1]))
+                return 0;
         }
     }
-    return tmpout - out;
+    return 1;
 }
 
 /* Given preference and allowed sigalgs set shared sigalgs */
-static int tls12_shared_sigalgs(SSL *s, TLS_SIGALGS *shsig,
-                                const unsigned char *pref, size_t preflen,
-                                const unsigned char *allow, size_t allowlen)
+static size_t tls12_shared_sigalgs(SSL *s, TLS_SIGALGS *shsig,
+                                   const unsigned char *pref, size_t preflen,
+                                   const unsigned char *allow, size_t allowlen)
 {
     const unsigned char *ptmp, *atmp;
     size_t i, j, nmatch = 0;
@@ -3423,7 +3341,7 @@ static int tls1_set_shared_sigalgs(SSL *s)
 
 /* Set preferred digest for each key type */
 
-int tls1_save_sigalgs(SSL *s, const unsigned char *data, int dsize)
+int tls1_save_sigalgs(SSL *s, const unsigned char *data, size_t dsize)
 {
     CERT *c = s->cert;
     /* Extension ignored for inappropriate versions */
@@ -3491,14 +3409,16 @@ int tls1_process_sigalgs(SSL *s)
         if (pmd[SSL_PKEY_ECC] == NULL)
             pmd[SSL_PKEY_ECC] = EVP_sha1();
 #endif
-# ifndef OPENSSL_NO_GOST
+#ifndef OPENSSL_NO_GOST
         if (pmd[SSL_PKEY_GOST01] == NULL)
             pmd[SSL_PKEY_GOST01] = EVP_get_digestbynid(NID_id_GostR3411_94);
         if (pmd[SSL_PKEY_GOST12_256] == NULL)
-            pmd[SSL_PKEY_GOST12_256] = EVP_get_digestbynid(NID_id_GostR3411_2012_256);
+            pmd[SSL_PKEY_GOST12_256] =
+                EVP_get_digestbynid(NID_id_GostR3411_2012_256);
         if (pmd[SSL_PKEY_GOST12_512] == NULL)
-            pmd[SSL_PKEY_GOST12_512] = EVP_get_digestbynid(NID_id_GostR3411_2012_512);
-# endif
+            pmd[SSL_PKEY_GOST12_512] =
+                EVP_get_digestbynid(NID_id_GostR3411_2012_512);
+#endif
     }
     return 1;
 }
@@ -3508,7 +3428,8 @@ int SSL_get_sigalgs(SSL *s, int idx,
                     unsigned char *rsig, unsigned char *rhash)
 {
     const unsigned char *psig = s->s3->tmp.peer_sigalgs;
-    if (psig == NULL)
+    size_t numsigalgs = s->s3->tmp.peer_sigalgslen / 2;
+    if (psig == NULL || numsigalgs > INT_MAX)
         return 0;
     if (idx >= 0) {
         idx <<= 1;
@@ -3521,7 +3442,7 @@ int SSL_get_sigalgs(SSL *s, int idx,
             *rsig = psig[1];
         tls1_lookup_sigalg(phash, psign, psignhash, psig);
     }
-    return s->s3->tmp.peer_sigalgslen / 2;
+    return (int)numsigalgs;
 }
 
 int SSL_get_shared_sigalgs(SSL *s, int idx,
@@ -3529,7 +3450,8 @@ int SSL_get_shared_sigalgs(SSL *s, int idx,
                            unsigned char *rsig, unsigned char *rhash)
 {
     TLS_SIGALGS *shsigalgs = s->cert->shared_sigalgs;
-    if (!shsigalgs || idx >= (int)s->cert->shared_sigalgslen)
+    if (!shsigalgs || idx >= (int)s->cert->shared_sigalgslen
+            || s->cert->shared_sigalgslen > INT_MAX)
         return 0;
     shsigalgs += idx;
     if (phash)
@@ -3542,7 +3464,7 @@ int SSL_get_shared_sigalgs(SSL *s, int idx,
         *rsig = shsigalgs->rsign;
     if (rhash)
         *rhash = shsigalgs->rhash;
-    return s->cert->shared_sigalgslen;
+    return (int)s->cert->shared_sigalgslen;
 }
 
 #define MAX_SIGALGLEN   (TLSEXT_hash_num * TLSEXT_signature_num * 2)
@@ -3605,7 +3527,7 @@ static int sig_cb(const char *elem, int len, void *arg)
 }
 
 /*
- * Set suppored signature algorithms based on a colon separated list of the
+ * Set supported signature algorithms based on a colon separated list of the
  * form sig+hash e.g. RSA+SHA512:DSA+SHA512
  */
 int tls1_set_sigalgs_list(CERT *c, const char *str, int client)
@@ -3619,8 +3541,7 @@ int tls1_set_sigalgs_list(CERT *c, const char *str, int client)
     return tls1_set_sigalgs(c, sig.sigalgs, sig.sigalgcnt, client);
 }
 
-int tls1_set_sigalgs(CERT *c, const int *psig_nids, size_t salglen,
-                     int client)
+int tls1_set_sigalgs(CERT *c, const int *psig_nids, size_t salglen, int client)
 {
     unsigned char *sigalgs, *sptr;
     int rhash, rsign;
@@ -3716,7 +3637,7 @@ int tls1_check_chain(SSL *s, X509 *x, EVP_PKEY *pk, STACK_OF(X509) *chain,
         /* idx == -2 means checking client certificate chains */
         if (idx == -2) {
             cpk = c->key;
-            idx = cpk - c->pkeys;
+            idx = (int)(cpk - c->pkeys);
         } else
             cpk = c->pkeys + idx;
         pvalid = s->s3->tmp.valid_flags + idx;
@@ -3966,7 +3887,6 @@ int SSL_check_chain(SSL *s, X509 *x, EVP_PKEY *pk, STACK_OF(X509) *chain)
     return tls1_check_chain(s, x, pk, chain, -1);
 }
 
-
 #ifndef OPENSSL_NO_DH
 DH *ssl_get_auto_dh(SSL *s)
 {