Implement certificate_authorities extension
[openssl.git] / ssl / statem / extensions.c
index 2aad56b..d0b15d5 100644 (file)
  * https://www.openssl.org/source/license.html
  */
 
-#include <stdlib.h>
-#include <openssl/ocsp.h>
+#include <string.h>
 #include "../ssl_locl.h"
 #include "statem_locl.h"
 
-static int tls_parse_clienthello_renegotiate(SSL *s, PACKET *pkt, int *al);
-static int tls_parse_clienthello_server_name(SSL *s, PACKET *pkt, int *al);
-#ifndef OPENSSL_NO_SRP
-static int tls_parse_clienthello_srp(SSL *s, PACKET *pkt, int *al);
-#endif
+static int final_renegotiate(SSL *s, unsigned int context, int sent,
+                                     int *al);
+static int init_server_name(SSL *s, unsigned int context);
+static int final_server_name(SSL *s, unsigned int context, int sent,
+                                     int *al);
 #ifndef OPENSSL_NO_EC
-static int tls_parse_clienthello_ec_pt_formats(SSL *s, PACKET *pkt, int *al);
-static int tls_parse_clienthello_supported_groups(SSL *s, PACKET *pkt, int *al);
+static int final_ec_pt_formats(SSL *s, unsigned int context, int sent,
+                                       int *al);
+#endif
+static int init_session_ticket(SSL *s, unsigned int context);
+#ifndef OPENSSL_NO_OCSP
+static int init_status_request(SSL *s, unsigned int context);
 #endif
-static int tls_parse_clienthello_session_ticket(SSL *s, PACKET *pkt, int *al);
-static int tls_parse_clienthello_sig_algs(SSL *s, PACKET *pkt, int *al);
-static int tls_parse_clienthello_status_request(SSL *s, PACKET *pkt, int *al);
 #ifndef OPENSSL_NO_NEXTPROTONEG
-static int tls_parse_clienthello_npn(SSL *s, PACKET *pkt, int *al);
+static int init_npn(SSL *s, unsigned int context);
+#endif
+static int init_alpn(SSL *s, unsigned int context);
+static int final_alpn(SSL *s, unsigned int context, int sent, int *al);
+static int init_sig_algs(SSL *s, unsigned int context);
+static int init_certificate_authorities(SSL *s, unsigned int context);
+static int tls_construct_certificate_authorities(SSL *s, WPACKET *pkt,
+                                                 unsigned int context, X509 *x,
+                                                 size_t chainidx, int *al);
+static int tls_parse_certificate_authorities(SSL *s, PACKET *pkt,
+                                             unsigned int context, X509 *x,
+                                             size_t chainidx, int *al);
+#ifndef OPENSSL_NO_SRP
+static int init_srp(SSL *s, unsigned int context);
+#endif
+static int init_etm(SSL *s, unsigned int context);
+static int init_ems(SSL *s, unsigned int context);
+static int final_ems(SSL *s, unsigned int context, int sent, int *al);
+static int init_psk_kex_modes(SSL *s, unsigned int context);
+#ifndef OPENSSL_NO_EC
+static int final_key_share(SSL *s, unsigned int context, int sent, int *al);
 #endif
-static int tls_parse_clienthello_alpn(SSL *s, PACKET *pkt, int *al);
 #ifndef OPENSSL_NO_SRTP
-static int tls_parse_clienthello_use_srtp(SSL *s, PACKET *pkt, int *al);
+static int init_srtp(SSL *s, unsigned int context);
 #endif
-static int tls_parse_clienthello_etm(SSL *s, PACKET *pkt, int *al);
-static int tls_parse_clienthello_key_share(SSL *s, PACKET *pkt, int *al);
-static int tls_parse_clienthello_ems(SSL *s, PACKET *pkt, int *al);
+static int final_sig_algs(SSL *s, unsigned int context, int sent, int *al);
+static int final_early_data(SSL *s, unsigned int context, int sent, int *al);
 
-typedef struct {
-    /* The ID for the extension */
+/* Structure to define a built-in extension */
+typedef struct extensions_definition_st {
+    /* The defined type for the extension */
     unsigned int type;
-    int (*server_parse)(SSL *s, PACKET *pkt, int *al);
-    int (*client_parse)(SSL *s, PACKET *pkt, int *al);
+    /*
+     * The context that this extension applies to, e.g. what messages and
+     * protocol versions
+     */
     unsigned int context;
+    /*
+     * Initialise extension before parsing. Always called for relevant contexts
+     * even if extension not present
+     */
+    int (*init)(SSL *s, unsigned int context);
+    /* Parse extension sent from client to server */
+    int (*parse_ctos)(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
+                      size_t chainidx, int *al);
+    /* Parse extension send from server to client */
+    int (*parse_stoc)(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
+                      size_t chainidx, int *al);
+    /* Construct extension sent from server to client */
+    int (*construct_stoc)(SSL *s, WPACKET *pkt, unsigned int context, X509 *x,
+                          size_t chainidx, int *al);
+    /* Construct extension sent from client to server */
+    int (*construct_ctos)(SSL *s, WPACKET *pkt, unsigned int context, X509 *x,
+                          size_t chainidx, int *al);
+    /*
+     * Finalise extension after parsing. Always called where an extensions was
+     * initialised even if the extension was not present. |sent| is set to 1 if
+     * the extension was seen, or 0 otherwise.
+     */
+    int (*final)(SSL *s, unsigned int context, int sent, int *al);
 } EXTENSION_DEFINITION;
 
+/*
+ * Definitions of all built-in extensions. NOTE: Changes in the number or order
+ * of these extensions should be mirrored with equivalent changes to the 
+ * indexes ( TLSEXT_IDX_* ) defined in ssl_locl.h.
+ * Each extension has an initialiser, a client and
+ * server side parser and a finaliser. The initialiser is called (if the
+ * extension is relevant to the given context) even if we did not see the
+ * extension in the message that we received. The parser functions are only
+ * called if we see the extension in the message. The finalisers are always
+ * called if the initialiser was called.
+ * There are also server and client side constructor functions which are always
+ * called during message construction if the extension is relevant for the
+ * given context.
+ * The initialisation, parsing, finalisation and construction functions are
+ * always called in the order defined in this list. Some extensions may depend
+ * on others having been processed first, so the order of this list is
+ * significant.
+ * The extension context is defined by a series of flags which specify which
+ * messages the extension is relevant to. These flags also specify whether the
+ * extension is relevant to a particular protocol or protocol version.
+ *
+ * TODO(TLS1.3): Make sure we have a test to check the consistency of these
+ */
+#define INVALID_EXTENSION { 0x10000, 0, NULL, NULL, NULL, NULL, NULL, NULL }
 static const EXTENSION_DEFINITION ext_defs[] = {
     {
         TLSEXT_TYPE_renegotiate,
-        tls_parse_clienthello_renegotiate,
-        NULL,
         EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_SSL3_ALLOWED
-        | EXT_TLS1_2_AND_BELOW_ONLY
+        | EXT_TLS1_2_AND_BELOW_ONLY,
+        NULL, tls_parse_ctos_renegotiate, tls_parse_stoc_renegotiate,
+        tls_construct_stoc_renegotiate, tls_construct_ctos_renegotiate,
+        final_renegotiate
     },
     {
         TLSEXT_TYPE_server_name,
-        tls_parse_clienthello_server_name,
-        NULL,
         EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO
-        | EXT_TLS1_3_ENCRYPTED_EXTENSIONS
+        | EXT_TLS1_3_ENCRYPTED_EXTENSIONS,
+        init_server_name,
+        tls_parse_ctos_server_name, tls_parse_stoc_server_name,
+        tls_construct_stoc_server_name, tls_construct_ctos_server_name,
+        final_server_name
     },
 #ifndef OPENSSL_NO_SRP
     {
         TLSEXT_TYPE_srp,
-        tls_parse_clienthello_srp,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        EXT_CLIENT_HELLO | EXT_TLS1_2_AND_BELOW_ONLY,
+        init_srp, tls_parse_ctos_srp, NULL, NULL, tls_construct_ctos_srp, NULL
     },
+#else
+    INVALID_EXTENSION,
 #endif
 #ifndef OPENSSL_NO_EC
     {
         TLSEXT_TYPE_ec_point_formats,
-        tls_parse_clienthello_ec_pt_formats,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY,
+        NULL, tls_parse_ctos_ec_pt_formats, tls_parse_stoc_ec_pt_formats,
+        tls_construct_stoc_ec_pt_formats, tls_construct_ctos_ec_pt_formats,
+        final_ec_pt_formats
     },
     {
         TLSEXT_TYPE_supported_groups,
-        tls_parse_clienthello_supported_groups,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_3_ENCRYPTED_EXTENSIONS
+        EXT_CLIENT_HELLO | EXT_TLS1_3_ENCRYPTED_EXTENSIONS,
+        NULL, tls_parse_ctos_supported_groups, NULL,
+        NULL /* TODO(TLS1.3): Need to add this */,
+        tls_construct_ctos_supported_groups, NULL
     },
+#else
+    INVALID_EXTENSION,
+    INVALID_EXTENSION,
 #endif
     {
         TLSEXT_TYPE_session_ticket,
-        tls_parse_clienthello_session_ticket,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY,
+        init_session_ticket, tls_parse_ctos_session_ticket,
+        tls_parse_stoc_session_ticket, tls_construct_stoc_session_ticket,
+        tls_construct_ctos_session_ticket, NULL
     },
     {
         TLSEXT_TYPE_signature_algorithms,
-        tls_parse_clienthello_sig_algs,
-        NULL,
-        EXT_CLIENT_HELLO
+        EXT_CLIENT_HELLO | EXT_TLS1_3_CERTIFICATE_REQUEST,
+        init_sig_algs, tls_parse_ctos_sig_algs,
+        tls_parse_ctos_sig_algs, tls_construct_ctos_sig_algs,
+        tls_construct_ctos_sig_algs, final_sig_algs
     },
+#ifndef OPENSSL_NO_OCSP
     {
         TLSEXT_TYPE_status_request,
-        tls_parse_clienthello_status_request,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_3_CERTIFICATE
+        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO
+        | EXT_TLS1_3_CERTIFICATE,
+        init_status_request, tls_parse_ctos_status_request,
+        tls_parse_stoc_status_request, tls_construct_stoc_status_request,
+        tls_construct_ctos_status_request, NULL
     },
+#else
+    INVALID_EXTENSION,
+#endif
 #ifndef OPENSSL_NO_NEXTPROTONEG
     {
         TLSEXT_TYPE_next_proto_neg,
-        tls_parse_clienthello_npn,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY,
+        init_npn, tls_parse_ctos_npn, tls_parse_stoc_npn,
+        tls_construct_stoc_next_proto_neg, tls_construct_ctos_npn, NULL
     },
+#else
+    INVALID_EXTENSION,
 #endif
     {
+        /*
+         * Must appear in this list after server_name so that finalisation
+         * happens after server_name callbacks
+         */
         TLSEXT_TYPE_application_layer_protocol_negotiation,
-        tls_parse_clienthello_alpn,
-        NULL,
         EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO
-        | EXT_TLS1_3_ENCRYPTED_EXTENSIONS
+        | EXT_TLS1_3_ENCRYPTED_EXTENSIONS,
+        init_alpn, tls_parse_ctos_alpn, tls_parse_stoc_alpn,
+        tls_construct_stoc_alpn, tls_construct_ctos_alpn, final_alpn
     },
+#ifndef OPENSSL_NO_SRTP
     {
         TLSEXT_TYPE_use_srtp,
-        tls_parse_clienthello_use_srtp,
-        NULL,
         EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO
-        | EXT_TLS1_3_ENCRYPTED_EXTENSIONS | EXT_DTLS_ONLY
+        | EXT_TLS1_3_ENCRYPTED_EXTENSIONS | EXT_DTLS_ONLY,
+        init_srtp, tls_parse_ctos_use_srtp, tls_parse_stoc_use_srtp,
+        tls_construct_stoc_use_srtp, tls_construct_ctos_use_srtp, NULL
     },
+#else
+    INVALID_EXTENSION,
+#endif
     {
         TLSEXT_TYPE_encrypt_then_mac,
-        tls_parse_clienthello_etm,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY | EXT_SSL3_ALLOWED,
+        init_etm, tls_parse_ctos_etm, tls_parse_stoc_etm,
+        tls_construct_stoc_etm, tls_construct_ctos_etm, NULL
     },
+#ifndef OPENSSL_NO_CT
     {
         TLSEXT_TYPE_signed_certificate_timestamp,
+        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO
+        | EXT_TLS1_3_CERTIFICATE,
+        NULL,
         /*
          * No server side support for this, but can be provided by a custom
          * extension. This is an exception to the rule that custom extensions
          * cannot override built in ones.
          */
-        NULL,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_3_CERTIFICATE
+        NULL, tls_parse_stoc_sct, NULL, tls_construct_ctos_sct,  NULL
     },
+#else
+    INVALID_EXTENSION,
+#endif
     {
         TLSEXT_TYPE_extended_master_secret,
-        tls_parse_clienthello_ems,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY,
+        init_ems, tls_parse_ctos_ems, tls_parse_stoc_ems,
+        tls_construct_stoc_ems, tls_construct_ctos_ems, final_ems
     },
     {
         TLSEXT_TYPE_supported_versions,
-        /* Processed inline as part of version selection */
-        NULL,
+        EXT_CLIENT_HELLO | EXT_TLS_IMPLEMENTATION_ONLY | EXT_TLS1_3_ONLY,
         NULL,
-        EXT_CLIENT_HELLO | EXT_TLS_IMPLEMENTATION_ONLY
+        /* Processed inline as part of version selection */
+        NULL, NULL, NULL, tls_construct_ctos_supported_versions, NULL
     },
     {
-        TLSEXT_TYPE_padding,
-        /* We send this, but don't read it */
-        NULL,
-        NULL,
-        EXT_CLIENT_HELLO
+        TLSEXT_TYPE_psk_kex_modes,
+        EXT_CLIENT_HELLO | EXT_TLS_IMPLEMENTATION_ONLY | EXT_TLS1_3_ONLY,
+        init_psk_kex_modes, tls_parse_ctos_psk_kex_modes, NULL, NULL,
+        tls_construct_ctos_psk_kex_modes, NULL
     },
+#ifndef OPENSSL_NO_EC
     {
+        /*
+         * Must be in this list after supported_groups. We need that to have
+         * been parsed before we do this one.
+         */
         TLSEXT_TYPE_key_share,
-        tls_parse_clienthello_key_share,
-        NULL,
         EXT_CLIENT_HELLO | EXT_TLS1_3_SERVER_HELLO
         | EXT_TLS1_3_HELLO_RETRY_REQUEST | EXT_TLS_IMPLEMENTATION_ONLY
-        | EXT_TLS1_3_ONLY
+        | EXT_TLS1_3_ONLY,
+        NULL, tls_parse_ctos_key_share, tls_parse_stoc_key_share,
+        tls_construct_stoc_key_share, tls_construct_ctos_key_share,
+        final_key_share
+    },
+#endif
+    {
+        TLSEXT_TYPE_cookie,
+        EXT_CLIENT_HELLO | EXT_TLS1_3_HELLO_RETRY_REQUEST
+        | EXT_TLS_IMPLEMENTATION_ONLY | EXT_TLS1_3_ONLY,
+        NULL, NULL, tls_parse_stoc_cookie, NULL, tls_construct_ctos_cookie,
+        NULL
+    },
+    {
+        /*
+         * Special unsolicited ServerHello extension only used when
+         * SSL_OP_CRYPTOPRO_TLSEXT_BUG is set
+         */
+        TLSEXT_TYPE_cryptopro_bug,
+        EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY,
+        NULL, NULL, NULL, tls_construct_stoc_cryptopro_bug, NULL, NULL
+    },
+    {
+        TLSEXT_TYPE_early_data,
+        EXT_CLIENT_HELLO | EXT_TLS1_3_ENCRYPTED_EXTENSIONS
+        | EXT_TLS1_3_NEW_SESSION_TICKET,
+        NULL, tls_parse_ctos_early_data, tls_parse_stoc_early_data,
+        tls_construct_stoc_early_data, tls_construct_ctos_early_data,
+        final_early_data
+    },
+    {
+        TLSEXT_TYPE_certificate_authorities,
+        EXT_CLIENT_HELLO | EXT_TLS1_3_CERTIFICATE_REQUEST | EXT_TLS1_3_ONLY,
+        init_certificate_authorities,
+        tls_parse_certificate_authorities, tls_parse_certificate_authorities,
+        tls_construct_certificate_authorities,
+        tls_construct_certificate_authorities, NULL,
+    },
+    {
+        /* Must be immediately before pre_shared_key */
+        TLSEXT_TYPE_padding,
+        EXT_CLIENT_HELLO,
+        NULL,
+        /* We send this, but don't read it */
+        NULL, NULL, NULL, tls_construct_ctos_padding, NULL
+    },
+    {
+        /* Required by the TLSv1.3 spec to always be the last extension */
+        TLSEXT_TYPE_psk,
+        EXT_CLIENT_HELLO | EXT_TLS1_3_SERVER_HELLO | EXT_TLS_IMPLEMENTATION_ONLY
+        | EXT_TLS1_3_ONLY,
+        NULL, tls_parse_ctos_psk, tls_parse_stoc_psk, tls_construct_stoc_psk,
+        tls_construct_ctos_psk, NULL
     }
 };
 
-/*
- * Comparison function used in a call to qsort (see tls_collect_extensions()
- * below.)
- * The two arguments |p1| and |p2| are expected to be pointers to RAW_EXTENSIONs
- *
- * Returns:
- *  1 if the type for p1 is greater than p2
- *  0 if the type for p1 and p2 are the same
- * -1 if the type for p1 is less than p2
- */
-static int compare_extensions(const void *p1, const void *p2)
-{
-    const RAW_EXTENSION *e1 = (const RAW_EXTENSION *)p1;
-    const RAW_EXTENSION *e2 = (const RAW_EXTENSION *)p2;
-
-    if (e1->type < e2->type)
-        return -1;
-    else if (e1->type > e2->type)
-        return 1;
-
-    return 0;
-}
-
 /*
  * Verify whether we are allowed to use the extension |type| in the current
  * |context|. Returns 1 to indicate the extension is allowed or unknown or 0 to
- * indicate the extension is not allowed.
+ * indicate the extension is not allowed. If returning 1 then |*found| is set to
+ * 1 if we found a definition for the extension, and |*idx| is set to its index
  */
-static int verify_extension(SSL *s, unsigned int context, unsigned int type)
+static int verify_extension(SSL *s, unsigned int context, unsigned int type,
+                            custom_ext_methods *meths, RAW_EXTENSION *rawexlist,
+                            RAW_EXTENSION **found)
 {
     size_t i;
+    size_t builtin_num = OSSL_NELEM(ext_defs);
+    const EXTENSION_DEFINITION *thisext;
 
-    for (i = 0; i < OSSL_NELEM(ext_defs); i++) {
-        if (type == ext_defs[i].type) {
+    for (i = 0, thisext = ext_defs; i < builtin_num; i++, thisext++) {
+        if (type == thisext->type) {
             /* Check we're allowed to use this extension in this context */
-            if ((context & ext_defs[i].context) == 0)
+            if ((context & thisext->context) == 0)
                 return 0;
 
             if (SSL_IS_DTLS(s)) {
-                if ((ext_defs[i].context & EXT_TLS_ONLY) != 0)
+                if ((thisext->context & EXT_TLS_ONLY) != 0)
                     return 0;
-            } else if ((ext_defs[i].context & EXT_DTLS_ONLY) != 0) {
+            } else if ((thisext->context & EXT_DTLS_ONLY) != 0) {
                     return 0;
             }
 
+            *found = &rawexlist[i];
             return 1;
         }
     }
 
+    if ((context & (EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO)) == 0) {
+        /*
+         * Custom extensions only apply to <=TLS1.2. This extension is unknown
+         * in this context - we allow it
+         */
+        *found = NULL;
+        return 1;
+    }
+
+    /* Check the custom extensions */
+    if (meths != NULL) {
+        for (i = builtin_num; i < builtin_num + meths->meths_count; i++) {
+            if (meths->meths[i - builtin_num].ext_type == type) {
+                *found = &rawexlist[i];
+                return 1;
+            }
+        }
+    }
+
     /* Unknown extension. We allow it */
+    *found = NULL;
     return 1;
 }
 
 /*
- * Finds an extension definition for the give extension |type|.
- * Returns 1 if found and stores the definition in |*def|, or returns 0
- * otherwise.
+ * Check whether the context defined for an extension |extctx| means whether
+ * the extension is relevant for the current context |thisctx| or not. Returns
+ * 1 if the extension is relevant for this context, and 0 otherwise
  */
-static int find_extension_definition(SSL *s, unsigned int type,
-                                     const EXTENSION_DEFINITION **def)
+static int extension_is_relevant(SSL *s, unsigned int extctx,
+                                 unsigned int thisctx)
 {
-    size_t i;
-
-    for (i = 0; i < OSSL_NELEM(ext_defs); i++) {
-        if (type == ext_defs[i].type) {
-            *def = &ext_defs[i];
-            return 1;
-        }
-    }
+    if ((SSL_IS_DTLS(s)
+                && (extctx & EXT_TLS_IMPLEMENTATION_ONLY) != 0)
+            || (s->version == SSL3_VERSION
+                    && (extctx & EXT_SSL3_ALLOWED) == 0)
+            || (SSL_IS_TLS13(s)
+                && (extctx & EXT_TLS1_2_AND_BELOW_ONLY) != 0)
+            || (!SSL_IS_TLS13(s) && (extctx & EXT_TLS1_3_ONLY) != 0))
+        return 0;
 
-    /* Unknown extension */
-    return 0;
+    return 1;
 }
 
 /*
  * Gather a list of all the extensions from the data in |packet]. |context|
  * tells us which message this extension is for. The raw extension data is
- * stored in |*res| with the number of found extensions in |*numfound|. In the
- * event of an error the alert type to use is stored in |*ad|. We don't actually
- * process the content of the extensions yet, except to check their types.
+ * stored in |*res| on success. In the event of an error the alert type to use
+ * is stored in |*al|. We don't actually process the content of the extensions
+ * yet, except to check their types. This function also runs the initialiser
+ * functions for all known extensions (whether we have collected them or not).
+ * If successful the caller is responsible for freeing the contents of |*res|.
  *
  * Per http://tools.ietf.org/html/rfc5246#section-7.4.1.4, there may not be
  * more than one extension of the same type in a ClientHello or ServerHello.
  * This function returns 1 if all extensions are unique and we have parsed their
  * types, and 0 if the extensions contain duplicates, could not be successfully
- * parsed, or an internal error occurred.
- */
-/*
- * TODO(TLS1.3): Refactor ServerHello extension parsing to use this and then
- * remove tls1_check_duplicate_extensions()
+ * found, or an internal error occurred. We only check duplicates for
+ * extensions that we know about. We ignore others.
  */
 int tls_collect_extensions(SSL *s, PACKET *packet, unsigned int context,
-                           RAW_EXTENSION **res, size_t *numfound, int *ad)
+                           RAW_EXTENSION **res, int *al, size_t *len)
 {
     PACKET extensions = *packet;
-    size_t num_extensions = 0, i = 0;
+    size_t i = 0;
+    size_t num_exts;
+    custom_ext_methods *exts = NULL;
     RAW_EXTENSION *raw_extensions = NULL;
+    const EXTENSION_DEFINITION *thisexd;
+
+    *res = NULL;
+
+    /*
+     * Initialise server side custom extensions. Client side is done during
+     * construction of extensions for the ClientHello.
+     */
+    if ((context & EXT_CLIENT_HELLO) != 0) {
+        exts = &s->cert->srv_ext;
+        custom_ext_init(&s->cert->srv_ext);
+    } else if ((context & EXT_TLS1_2_SERVER_HELLO) != 0) {
+        exts = &s->cert->cli_ext;
+    }
+
+    num_exts = OSSL_NELEM(ext_defs) + (exts != NULL ? exts->meths_count : 0);
+    raw_extensions = OPENSSL_zalloc(num_exts * sizeof(*raw_extensions));
+    if (raw_extensions == NULL) {
+        *al = SSL_AD_INTERNAL_ERROR;
+        SSLerr(SSL_F_TLS_COLLECT_EXTENSIONS, ERR_R_MALLOC_FAILURE);
+        return 0;
+    }
 
-    /* First pass: count the extensions. */
     while (PACKET_remaining(&extensions) > 0) {
         unsigned int type;
         PACKET extension;
+        RAW_EXTENSION *thisex;
 
         if (!PACKET_get_net_2(&extensions, &type) ||
             !PACKET_get_length_prefixed_2(&extensions, &extension)) {
             SSLerr(SSL_F_TLS_COLLECT_EXTENSIONS, SSL_R_BAD_EXTENSION);
-            *ad = SSL_AD_DECODE_ERROR;
+            *al = SSL_AD_DECODE_ERROR;
             goto err;
         }
-        /* Verify this extension is allowed */
-        if (!verify_extension(s, context, type)) {
+        /*
+         * Verify this extension is allowed. We only check duplicates for
+         * extensions that we recognise. We also have a special case for the
+         * PSK extension, which must be the last one in the ClientHello.
+         */
+        if (!verify_extension(s, context, type, exts, raw_extensions, &thisex)
+                || (thisex != NULL && thisex->present == 1)
+                || (type == TLSEXT_TYPE_psk
+                    && (context & EXT_CLIENT_HELLO) != 0
+                    && PACKET_remaining(&extensions) != 0)) {
             SSLerr(SSL_F_TLS_COLLECT_EXTENSIONS, SSL_R_BAD_EXTENSION);
-            *ad = SSL_AD_ILLEGAL_PARAMETER;
+            *al = SSL_AD_ILLEGAL_PARAMETER;
             goto err;
         }
-        num_extensions++;
-    }
-
-    if (num_extensions > 0) {
-        raw_extensions = OPENSSL_zalloc(sizeof(*raw_extensions)
-                                        * num_extensions);
-        if (raw_extensions == NULL) {
-            *ad = SSL_AD_INTERNAL_ERROR;
-            SSLerr(SSL_F_TLS_COLLECT_EXTENSIONS, ERR_R_MALLOC_FAILURE);
-            goto err;
-        }
-
-        /* Second pass: collect the extensions. */
-        for (i = 0; i < num_extensions; i++) {
-            if (!PACKET_get_net_2(packet, &raw_extensions[i].type) ||
-                !PACKET_get_length_prefixed_2(packet,
-                                              &raw_extensions[i].data)) {
-                /* This should not happen. */
-                *ad = SSL_AD_INTERNAL_ERROR;
-                SSLerr(SSL_F_TLS_COLLECT_EXTENSIONS, ERR_R_INTERNAL_ERROR);
-                goto err;
-            }
+        if (thisex != NULL) {
+            thisex->data = extension;
+            thisex->present = 1;
+            thisex->type = type;
         }
+    }
 
-        if (PACKET_remaining(packet) != 0) {
-            *ad = SSL_AD_DECODE_ERROR;
-            SSLerr(SSL_F_TLS_COLLECT_EXTENSIONS, SSL_R_LENGTH_MISMATCH);
+    /*
+     * Initialise all known extensions relevant to this context, whether we have
+     * found them or not
+     */
+    for (thisexd = ext_defs, i = 0; i < OSSL_NELEM(ext_defs); i++, thisexd++) {
+        if(thisexd->init != NULL && (thisexd->context & context) != 0
+                && extension_is_relevant(s, thisexd->context, context)
+                && !thisexd->init(s, context)) {
+            *al = SSL_AD_INTERNAL_ERROR;
             goto err;
         }
-        /* Sort the extensions and make sure there are no duplicates. */
-        qsort(raw_extensions, num_extensions, sizeof(*raw_extensions),
-              compare_extensions);
-        for (i = 1; i < num_extensions; i++) {
-            if (raw_extensions[i - 1].type == raw_extensions[i].type) {
-                *ad = SSL_AD_DECODE_ERROR;
-                goto err;
-            }
-        }
     }
 
     *res = raw_extensions;
-    *numfound = num_extensions;
+    if (len != NULL)
+        *len = num_exts;
     return 1;
 
  err:
@@ -331,514 +499,663 @@ int tls_collect_extensions(SSL *s, PACKET *packet, unsigned int context,
     return 0;
 }
 
-int tls_parse_all_extensions(SSL *s, RAW_EXTENSION *exts, size_t numexts,
-                             int *al)
+/*
+ * Runs the parser for a given extension with index |idx|. |exts| contains the
+ * list of all parsed extensions previously collected by
+ * tls_collect_extensions(). The parser is only run if it is applicable for the
+ * given |context| and the parser has not already been run. If this is for a
+ * Certificate message, then we also provide the parser with the relevant
+ * Certificate |x| and its position in the |chainidx| with 0 being the first
+ * Certificate. Returns 1 on success or 0 on failure. In the event of a failure
+ * |*al| is populated with a suitable alert code. If an extension is not present
+ * this counted as success.
+ */
+int tls_parse_extension(SSL *s, TLSEXT_INDEX idx, int context,
+                        RAW_EXTENSION *exts, X509 *x, size_t chainidx, int *al)
 {
-    size_t loop;
+    RAW_EXTENSION *currext = &exts[idx];
+    int (*parser)(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
+                  size_t chainidx, int *al) = NULL;
 
-    for (loop = 0; loop < numexts; loop++) {
-        RAW_EXTENSION *currext = &exts[loop];
-        const EXTENSION_DEFINITION *extdef = NULL;
-        int (*parser)(SSL *s, PACKET *pkt, int *al) = NULL;
+    /* Skip if the extension is not present */
+    if (!currext->present)
+        return 1;
 
-        if (s->tlsext_debug_cb)
-            s->tlsext_debug_cb(s, 0, currext->type,
-                               PACKET_data(&currext->data),
-                               PACKET_remaining(&currext->data),
-                               s->tlsext_debug_arg);
+    if (s->ext.debug_cb)
+        s->ext.debug_cb(s, !s->server, currext->type,
+                        PACKET_data(&currext->data),
+                        PACKET_remaining(&currext->data),
+                        s->ext.debug_arg);
 
-        /* Skip if we've already parsed this extension */
-        if (currext->parsed)
-            continue;
+    /* Skip if we've already parsed this extension */
+    if (currext->parsed)
+        return 1;
 
-        currext->parsed = 1;
-
-        parser = NULL;
-        if (find_extension_definition(s, currext->type, &extdef))
-            parser = s->server ? extdef->server_parse : extdef->client_parse;
-
-        if (parser == NULL) {
-            /*
-             * Could be a custom extension. We only allow this if it is a non
-             * resumed session on the server side
-             */
-            if ((!s->hit || !s->server)
-                    && custom_ext_parse(s, s->server, currext->type,
-                                        PACKET_data(&currext->data),
-                                        PACKET_remaining(&currext->data),
-                                        al) <= 0)
-                return 0;
+    currext->parsed = 1;
 
-            continue;
-        }
+    if (idx < OSSL_NELEM(ext_defs)) {
+        /* We are handling a built-in extension */
+        const EXTENSION_DEFINITION *extdef = &ext_defs[idx];
 
-        /* Check if this extension is defined for our protocol. If not, skip */
-        if ((SSL_IS_DTLS(s)
-                    && (extdef->context & EXT_TLS_IMPLEMENTATION_ONLY) != 0)
-                || (s->version == SSL3_VERSION
-                        && (extdef->context & EXT_SSL3_ALLOWED) == 0)
-                || (SSL_IS_TLS13(s)
-                    && (extdef->context & EXT_TLS1_2_AND_BELOW_ONLY) != 0)
-                || (!SSL_IS_TLS13(s)
-                    && (extdef->context & EXT_TLS1_3_ONLY) != 0)
-                || (s->server && extdef->server_parse == NULL)
-                || (!s->server && extdef->client_parse == NULL))
-            continue;
+        /* Check if extension is defined for our protocol. If not, skip */
+        if (!extension_is_relevant(s, extdef->context, context))
+            return 1;
 
-        if (!parser(s, &currext->data, al))
-            return 0;
-    }
+        parser = s->server ? extdef->parse_ctos : extdef->parse_stoc;
 
-    return 1;
-}
+        if (parser != NULL)
+            return parser(s, &currext->data, context, x, chainidx, al);
 
-/*
- * Find a specific extension by |type| in the list |exts| containing |numexts|
- * extensions, and the parse it immediately. Returns 1 on success, or 0 on
- * failure. If a failure has occurred then |*al| will also be set to the alert
- * to be sent.
- */
-int tls_parse_extension(SSL *s, int type,  RAW_EXTENSION *exts, size_t numexts,
-                        int *al)
-{
-    RAW_EXTENSION *ext = tls_get_extension_by_type(exts, numexts, type);
+        /*
+         * If the parser is NULL we fall through to the custom extension
+         * processing
+         */
+    }
 
-    if (ext == NULL)
-        return 1;
+    /*
+     * This is a custom extension. We only allow this if it is a non
+     * resumed session on the server side.
+     *chain
+     * TODO(TLS1.3): We only allow old style <=TLS1.2 custom extensions.
+     * We're going to need a new mechanism for TLS1.3 to specify which
+     * messages to add the custom extensions to.
+     */
+    if ((!s->hit || !s->server)
+            && (context
+                & (EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO)) != 0
+            && custom_ext_parse(s, s->server, currext->type,
+                                PACKET_data(&currext->data),
+                                PACKET_remaining(&currext->data),
+                                al) <= 0)
+        return 0;
 
-    return tls_parse_all_extensions(s, ext, 1, al);
+    return 1;
 }
 
-
 /*
- * Parse the client's renegotiation binding and abort if it's not right
+ * Parse all remaining extensions that have not yet been parsed. Also calls the
+ * finalisation for all extensions at the end, whether we collected them or not.
+ * Returns 1 for success or 0 for failure. If we are working on a Certificate
+ * message then we also pass the Certificate |x| and its position in the
+ * |chainidx|, with 0 being the first certificate. On failure, |*al| is
+ * populated with a suitable alert code.
  */
-static int tls_parse_clienthello_renegotiate(SSL *s, PACKET *pkt, int *al)
+int tls_parse_all_extensions(SSL *s, int context, RAW_EXTENSION *exts, X509 *x,
+                             size_t chainidx, int *al)
 {
-    unsigned int ilen;
-    const unsigned char *data;
-
-    /* Parse the length byte */
-    if (!PACKET_get_1(pkt, &ilen)
-        || !PACKET_get_bytes(pkt, &data, ilen)) {
-        SSLerr(SSL_F_SSL_PARSE_CLIENTHELLO_RENEGOTIATE_EXT,
-               SSL_R_RENEGOTIATION_ENCODING_ERR);
-        *al = SSL_AD_ILLEGAL_PARAMETER;
-        return 0;
+    size_t i, numexts = OSSL_NELEM(ext_defs);
+    const EXTENSION_DEFINITION *thisexd;
+
+    /* Calculate the number of extensions in the extensions list */
+    if ((context & EXT_CLIENT_HELLO) != 0) {
+        numexts += s->cert->srv_ext.meths_count;
+    } else if ((context & EXT_TLS1_2_SERVER_HELLO) != 0) {
+        numexts += s->cert->cli_ext.meths_count;
     }
 
-    /* Check that the extension matches */
-    if (ilen != s->s3->previous_client_finished_len) {
-        SSLerr(SSL_F_SSL_PARSE_CLIENTHELLO_RENEGOTIATE_EXT,
-               SSL_R_RENEGOTIATION_MISMATCH);
-        *al = SSL_AD_HANDSHAKE_FAILURE;
-        return 0;
+    /* Parse each extension in turn */
+    for (i = 0; i < numexts; i++) {
+        if (!tls_parse_extension(s, i, context, exts, x, chainidx, al))
+            return 0;
     }
 
-    if (memcmp(data, s->s3->previous_client_finished,
-               s->s3->previous_client_finished_len)) {
-        SSLerr(SSL_F_SSL_PARSE_CLIENTHELLO_RENEGOTIATE_EXT,
-               SSL_R_RENEGOTIATION_MISMATCH);
-        *al = SSL_AD_HANDSHAKE_FAILURE;
-        return 0;
+    /*
+     * Finalise all known extensions relevant to this context, whether we have
+     * found them or not
+     */
+    for (i = 0, thisexd = ext_defs; i < OSSL_NELEM(ext_defs); i++, thisexd++) {
+        if(thisexd->final != NULL
+                && (thisexd->context & context) != 0
+                && !thisexd->final(s, context, exts[i].present, al))
+            return 0;
     }
 
-    s->s3->send_connection_binding = 1;
-
     return 1;
 }
 
-static int tls_parse_clienthello_server_name(SSL *s, PACKET *pkt, int *al)
+/*
+ * Construct all the extensions relevant to the current |context| and write
+ * them to |pkt|. If this is an extension for a Certificate in a Certificate
+ * message, then |x| will be set to the Certificate we are handling, and
+ * |chainidx| will indicate the position in the chainidx we are processing (with
+ * 0 being the first in the chain). Returns 1 on success or 0 on failure. If a
+ * failure occurs then |al| is populated with a suitable alert code. On a
+ * failure construction stops at the first extension to fail to construct.
+ */
+int tls_construct_extensions(SSL *s, WPACKET *pkt, unsigned int context,
+                             X509 *x, size_t chainidx, int *al)
 {
-    unsigned int servname_type;
-    PACKET sni, hostname;
-
-    /*-
-     * The servername extension is treated as follows:
-     *
-     * - Only the hostname type is supported with a maximum length of 255.
-     * - The servername is rejected if too long or if it contains zeros,
-     *   in which case an fatal alert is generated.
-     * - The servername field is maintained together with the session cache.
-     * - When a session is resumed, the servername call back invoked in order
-     *   to allow the application to position itself to the right context.
-     * - The servername is acknowledged if it is new for a session or when
-     *   it is identical to a previously used for the same session.
-     *   Applications can control the behaviour.  They can at any time
-     *   set a 'desirable' servername for a new SSL object. This can be the
-     *   case for example with HTTPS when a Host: header field is received and
-     *   a renegotiation is requested. In this case, a possible servername
-     *   presented in the new client hello is only acknowledged if it matches
-     *   the value of the Host: field.
-     * - Applications must  use SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
-     *   if they provide for changing an explicit servername context for the
-     *   session, i.e. when the session has been established with a servername
-     *   extension.
-     * - On session reconnect, the servername extension may be absent.
-     *
-     */
-    if (!PACKET_as_length_prefixed_2(pkt, &sni)
-        /* ServerNameList must be at least 1 byte long. */
-        || PACKET_remaining(&sni) == 0) {
-        *al = SSL_AD_DECODE_ERROR;
-        return 0;
-    }
+    size_t i;
+    int addcustom = 0, min_version, max_version = 0, reason, tmpal;
+    const EXTENSION_DEFINITION *thisexd;
 
     /*
-     * Although the server_name extension was intended to be
-     * extensible to new name types, RFC 4366 defined the
-     * syntax inextensibility and OpenSSL 1.0.x parses it as
-     * such.
-     * RFC 6066 corrected the mistake but adding new name types
-     * is nevertheless no longer feasible, so act as if no other
-     * SNI types can exist, to simplify parsing.
-     *
-     * Also note that the RFC permits only one SNI value per type,
-     * i.e., we can only have a single hostname.
+     * Normally if something goes wrong during construction it's an internal
+     * error. We can always override this later.
      */
-    if (!PACKET_get_1(&sni, &servname_type)
-        || servname_type != TLSEXT_NAMETYPE_host_name
-        || !PACKET_as_length_prefixed_2(&sni, &hostname)) {
-        *al = SSL_AD_DECODE_ERROR;
-        return 0;
+    tmpal = SSL_AD_INTERNAL_ERROR;
+
+    if (!WPACKET_start_sub_packet_u16(pkt)
+               /*
+                * If extensions are of zero length then we don't even add the
+                * extensions length bytes to a ClientHello/ServerHello in SSLv3
+                */
+            || ((context & (EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO)) != 0
+               && s->version == SSL3_VERSION
+               && !WPACKET_set_flags(pkt,
+                                     WPACKET_FLAGS_ABANDON_ON_ZERO_LENGTH))) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_EXTENSIONS, ERR_R_INTERNAL_ERROR);
+        goto err;
     }
 
-    if (!s->hit) {
-        if (PACKET_remaining(&hostname) > TLSEXT_MAXLEN_host_name) {
-            *al = TLS1_AD_UNRECOGNIZED_NAME;
-            return 0;
-        }
-
-        if (PACKET_contains_zero_byte(&hostname)) {
-            *al = TLS1_AD_UNRECOGNIZED_NAME;
-            return 0;
-        }
-
-        if (!PACKET_strndup(&hostname, &s->session->tlsext_hostname)) {
-            *al = TLS1_AD_INTERNAL_ERROR;
-            return 0;
+    if ((context & EXT_CLIENT_HELLO) != 0) {
+        reason = ssl_get_client_min_max_version(s, &min_version, &max_version);
+        if (reason != 0) {
+            SSLerr(SSL_F_TLS_CONSTRUCT_EXTENSIONS, reason);
+            goto err;
         }
+    }
 
-        s->servername_done = 1;
-    } else {
+    /* Add custom extensions first */
+    if ((context & EXT_CLIENT_HELLO) != 0) {
+        custom_ext_init(&s->cert->cli_ext);
+        addcustom = 1;
+    } else if ((context & EXT_TLS1_2_SERVER_HELLO) != 0) {
         /*
-         * TODO(openssl-team): if the SNI doesn't match, we MUST
-         * fall back to a full handshake.
+         * We already initialised the custom extensions during ClientHello
+         * parsing.
+         *
+         * TODO(TLS1.3): We're going to need a new custom extension mechanism
+         * for TLS1.3, so that custom extensions can specify which of the
+         * multiple message they wish to add themselves to.
          */
-        s->servername_done = s->session->tlsext_hostname
-            && PACKET_equal(&hostname, s->session->tlsext_hostname,
-                            strlen(s->session->tlsext_hostname));
+        addcustom = 1;
+    }
+
+    if (addcustom && !custom_ext_add(s, s->server, pkt, &tmpal)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_EXTENSIONS, ERR_R_INTERNAL_ERROR);
+        goto err;
+    }
+
+    for (i = 0, thisexd = ext_defs; i < OSSL_NELEM(ext_defs); i++, thisexd++) {
+        int (*construct)(SSL *s, WPACKET *pkt, unsigned int context, X509 *x,
+                         size_t chainidx, int *al);
+
+        /* Skip if not relevant for our context */
+        if ((thisexd->context & context) == 0)
+            continue;
+
+        construct = s->server ? thisexd->construct_stoc
+                              : thisexd->construct_ctos;
+
+        /* Check if this extension is defined for our protocol. If not, skip */
+        if ((SSL_IS_DTLS(s)
+                    && (thisexd->context & EXT_TLS_IMPLEMENTATION_ONLY)
+                       != 0)
+                || (s->version == SSL3_VERSION
+                        && (thisexd->context & EXT_SSL3_ALLOWED) == 0)
+                || (SSL_IS_TLS13(s)
+                    && (thisexd->context & EXT_TLS1_2_AND_BELOW_ONLY)
+                       != 0)
+                || (!SSL_IS_TLS13(s)
+                    && (thisexd->context & EXT_TLS1_3_ONLY) != 0
+                    && (context & EXT_CLIENT_HELLO) == 0)
+                || ((thisexd->context & EXT_TLS1_3_ONLY) != 0
+                    && (context & EXT_CLIENT_HELLO) != 0
+                    && (SSL_IS_DTLS(s) || max_version < TLS1_3_VERSION))
+                || construct == NULL)
+            continue;
+
+        if (!construct(s, pkt, context, x, chainidx, &tmpal))
+            goto err;
+    }
+
+    if (!WPACKET_close(pkt)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_EXTENSIONS, ERR_R_INTERNAL_ERROR);
+        goto err;
     }
 
     return 1;
+
+ err:
+    *al = tmpal;
+    return 0;
 }
 
-#ifndef OPENSSL_NO_SRP
-static int tls_parse_clienthello_srp(SSL *s, PACKET *pkt, int *al)
+/*
+ * Built in extension finalisation and initialisation functions. All initialise
+ * or finalise the associated extension type for the given |context|. For
+ * finalisers |sent| is set to 1 if we saw the extension during parsing, and 0
+ * otherwise. These functions return 1 on success or 0 on failure. In the event
+ * of a failure then |*al| is populated with a suitable error code.
+ */
+
+static int final_renegotiate(SSL *s, unsigned int context, int sent,
+                                     int *al)
 {
-    PACKET srp_I;
+    if (!s->server) {
+        /*
+         * Check if we can connect to a server that doesn't support safe
+         * renegotiation
+         */
+        if (!(s->options & SSL_OP_LEGACY_SERVER_CONNECT)
+                && !(s->options & SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION)
+                && !sent) {
+            *al = SSL_AD_HANDSHAKE_FAILURE;
+            SSLerr(SSL_F_FINAL_RENEGOTIATE,
+                   SSL_R_UNSAFE_LEGACY_RENEGOTIATION_DISABLED);
+            return 0;
+        }
 
-    if (!PACKET_as_length_prefixed_1(pkt, &srp_I)
-            || PACKET_contains_zero_byte(&srp_I)) {
-        *al = SSL_AD_DECODE_ERROR;
-        return 0;
+        return 1;
     }
 
-    /*
-     * TODO(openssl-team): currently, we re-authenticate the user
-     * upon resumption. Instead, we MUST ignore the login.
-     */
-    if (!PACKET_strndup(&srp_I, &s->srp_ctx.login)) {
-        *al = TLS1_AD_INTERNAL_ERROR;
+    /* Need RI if renegotiating */
+    if (s->renegotiate
+            && !(s->options & SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION)
+            && !sent) {
+        *al = SSL_AD_HANDSHAKE_FAILURE;
+        SSLerr(SSL_F_FINAL_RENEGOTIATE,
+               SSL_R_UNSAFE_LEGACY_RENEGOTIATION_DISABLED);
         return 0;
     }
 
+
     return 1;
 }
-#endif
 
-#ifndef OPENSSL_NO_EC
-static int tls_parse_clienthello_ec_pt_formats(SSL *s, PACKET *pkt, int *al)
+static int init_server_name(SSL *s, unsigned int context)
 {
-    PACKET ec_point_format_list;
+    if (s->server)
+        s->servername_done = 0;
 
-    if (!PACKET_as_length_prefixed_1(pkt, &ec_point_format_list)
-        || PACKET_remaining(&ec_point_format_list) == 0) {
-        *al = SSL_AD_DECODE_ERROR;
+    return 1;
+}
+
+static int final_server_name(SSL *s, unsigned int context, int sent,
+                                     int *al)
+{
+    int ret = SSL_TLSEXT_ERR_NOACK;
+    int altmp = SSL_AD_UNRECOGNIZED_NAME;
+
+    if (s->ctx != NULL && s->ctx->ext.servername_cb != 0)
+        ret = s->ctx->ext.servername_cb(s, &altmp,
+                                        s->ctx->ext.servername_arg);
+    else if (s->session_ctx != NULL
+             && s->session_ctx->ext.servername_cb != 0)
+        ret = s->session_ctx->ext.servername_cb(s, &altmp,
+                                       s->session_ctx->ext.servername_arg);
+
+    switch (ret) {
+    case SSL_TLSEXT_ERR_ALERT_FATAL:
+        *al = altmp;
         return 0;
+
+    case SSL_TLSEXT_ERR_ALERT_WARNING:
+        *al = altmp;
+        return 1;
+
+    case SSL_TLSEXT_ERR_NOACK:
+        s->servername_done = 0;
+        return 1;
+
+    default:
+        return 1;
     }
+}
+
+#ifndef OPENSSL_NO_EC
+static int final_ec_pt_formats(SSL *s, unsigned int context, int sent,
+                                       int *al)
+{
+    unsigned long alg_k, alg_a;
+
+    if (s->server)
+        return 1;
 
-    if (!s->hit) {
-        if (!PACKET_memdup(&ec_point_format_list,
-                           &s->session->tlsext_ecpointformatlist,
-                           &s->session->tlsext_ecpointformatlist_length)) {
-            *al = TLS1_AD_INTERNAL_ERROR;
+    alg_k = s->s3->tmp.new_cipher->algorithm_mkey;
+    alg_a = s->s3->tmp.new_cipher->algorithm_auth;
+
+    /*
+     * If we are client and using an elliptic curve cryptography cipher
+     * suite, then if server returns an EC point formats lists extension it
+     * must contain uncompressed.
+     */
+    if (s->ext.ecpointformats != NULL
+            && s->ext.ecpointformats_len > 0
+            && s->session->ext.ecpointformats != NULL
+            && s->session->ext.ecpointformats_len > 0
+            && ((alg_k & SSL_kECDHE) || (alg_a & SSL_aECDSA))) {
+        /* we are using an ECC cipher */
+        size_t i;
+        unsigned char *list = s->session->ext.ecpointformats;
+
+        for (i = 0; i < s->session->ext.ecpointformats_len; i++) {
+            if (*list++ == TLSEXT_ECPOINTFORMAT_uncompressed)
+                break;
+        }
+        if (i == s->session->ext.ecpointformats_len) {
+            SSLerr(SSL_F_FINAL_EC_PT_FORMATS,
+                   SSL_R_TLS_INVALID_ECPOINTFORMAT_LIST);
             return 0;
         }
     }
 
     return 1;
 }
-#endif                          /* OPENSSL_NO_EC */
+#endif
 
-static int tls_parse_clienthello_session_ticket(SSL *s, PACKET *pkt, int *al)
+static int init_session_ticket(SSL *s, unsigned int context)
 {
-    if (s->tls_session_ticket_ext_cb &&
-            !s->tls_session_ticket_ext_cb(s, PACKET_data(pkt),
-                                          PACKET_remaining(pkt),
-                                          s->tls_session_ticket_ext_cb_arg)) {
-        *al = TLS1_AD_INTERNAL_ERROR;
-        return 0;
-    }
+    if (!s->server)
+        s->ext.ticket_expected = 0;
 
     return 1;
 }
 
-static int tls_parse_clienthello_sig_algs(SSL *s, PACKET *pkt, int *al)
+#ifndef OPENSSL_NO_OCSP
+static int init_status_request(SSL *s, unsigned int context)
 {
-    PACKET supported_sig_algs;
-
-    if (!PACKET_as_length_prefixed_2(pkt, &supported_sig_algs)
-            || (PACKET_remaining(&supported_sig_algs) % 2) != 0
-            || PACKET_remaining(&supported_sig_algs) == 0) {
-        *al = SSL_AD_DECODE_ERROR;
-        return 0;
+    if (s->server) {
+        s->ext.status_type = TLSEXT_STATUSTYPE_nothing;
+    } else {
+        /*
+         * Ensure we get sensible values passed to tlsext_status_cb in the event
+         * that we don't receive a status message
+         */
+        OPENSSL_free(s->ext.ocsp.resp);
+        s->ext.ocsp.resp = NULL;
+        s->ext.ocsp.resp_len = 0;
     }
 
-    if (!s->hit && !tls1_save_sigalgs(s, PACKET_data(&supported_sig_algs),
-                                      PACKET_remaining(&supported_sig_algs))) {
-        *al = TLS1_AD_INTERNAL_ERROR;
-        return 0;
-    }
+    return 1;
+}
+#endif
+
+#ifndef OPENSSL_NO_NEXTPROTONEG
+static int init_npn(SSL *s, unsigned int context)
+{
+    s->s3->npn_seen = 0;
 
     return 1;
 }
+#endif
 
-static int tls_parse_clienthello_status_request(SSL *s, PACKET *pkt, int *al)
+static int init_alpn(SSL *s, unsigned int context)
 {
-    if (!PACKET_get_1(pkt, (unsigned int *)&s->tlsext_status_type)) {
-        *al = SSL_AD_DECODE_ERROR;
-        return 0;
+    OPENSSL_free(s->s3->alpn_selected);
+    s->s3->alpn_selected = NULL;
+    s->s3->alpn_selected_len = 0;
+    if (s->server) {
+        OPENSSL_free(s->s3->alpn_proposed);
+        s->s3->alpn_proposed = NULL;
+        s->s3->alpn_proposed_len = 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 (pkt, &responder_id_list)) {
-            *al = SSL_AD_DECODE_ERROR;
-            return 0;
-        }
+    return 1;
+}
 
-        /*
-         * 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) {
+static int final_alpn(SSL *s, unsigned int context, int sent, int *al)
+{
+    const unsigned char *selected = NULL;
+    unsigned char selected_len = 0;
+
+    if (!s->server)
+        return 1;
+
+    if (s->ctx->ext.alpn_select_cb != NULL && s->s3->alpn_proposed != NULL) {
+        int r = s->ctx->ext.alpn_select_cb(s, &selected, &selected_len,
+                                           s->s3->alpn_proposed,
+                                           (unsigned int)s->s3->alpn_proposed_len,
+                                           s->ctx->ext.alpn_select_cb_arg);
+
+        if (r == SSL_TLSEXT_ERR_OK) {
+            OPENSSL_free(s->s3->alpn_selected);
+            s->s3->alpn_selected = OPENSSL_memdup(selected, selected_len);
+            if (s->s3->alpn_selected == NULL) {
                 *al = SSL_AD_INTERNAL_ERROR;
                 return 0;
             }
+            s->s3->alpn_selected_len = selected_len;
+#ifndef OPENSSL_NO_NEXTPROTONEG
+            /* ALPN takes precedence over NPN. */
+            s->s3->npn_seen = 0;
+#endif
         } else {
-            s->tlsext_ocsp_ids = NULL;
+            *al = SSL_AD_NO_APPLICATION_PROTOCOL;
+            return 0;
         }
+    }
 
-        while (PACKET_remaining(&responder_id_list) > 0) {
-            OCSP_RESPID *id;
-            PACKET responder_id;
-            const unsigned char *id_data;
+    return 1;
+}
 
-            if (!PACKET_get_length_prefixed_2(&responder_id_list,
-                                              &responder_id)
-                    || PACKET_remaining(&responder_id) == 0) {
-                *al = SSL_AD_DECODE_ERROR;
-                return 0;
-            }
+static int init_sig_algs(SSL *s, unsigned int context)
+{
+    /* Clear any signature algorithms extension received */
+    OPENSSL_free(s->s3->tmp.peer_sigalgs);
+    s->s3->tmp.peer_sigalgs = NULL;
 
-            id_data = PACKET_data(&responder_id);
-            /* TODO(size_t): Convert d2i_* to size_t */
-            id = d2i_OCSP_RESPID(NULL, &id_data,
-                                 (int)PACKET_remaining(&responder_id));
-            if (id == NULL) {
-                *al = SSL_AD_DECODE_ERROR;
-                return 0;
-            }
+    return 1;
+}
 
-            if (id_data != PACKET_end(&responder_id)) {
-                OCSP_RESPID_free(id);
-                *al = SSL_AD_DECODE_ERROR;
-                return 0;
-            }
+#ifndef OPENSSL_NO_SRP
+static int init_srp(SSL *s, unsigned int context)
+{
+    OPENSSL_free(s->srp_ctx.login);
+    s->srp_ctx.login = NULL;
 
-            if (!sk_OCSP_RESPID_push(s->tlsext_ocsp_ids, id)) {
-                OCSP_RESPID_free(id);
-                *al = SSL_AD_INTERNAL_ERROR;
-                return 0;
-            }
-        }
+    return 1;
+}
+#endif
 
-        /* Read in request_extensions */
-        if (!PACKET_as_length_prefixed_2(pkt, &exts)) {
-            *al = SSL_AD_DECODE_ERROR;
-            return 0;
-        }
+static int init_etm(SSL *s, unsigned int context)
+{
+    s->ext.use_etm = 0;
 
-        if (PACKET_remaining(&exts) > 0) {
-            ext_data = PACKET_data(&exts);
-            sk_X509_EXTENSION_pop_free(s->tlsext_ocsp_exts,
-                                       X509_EXTENSION_free);
-            s->tlsext_ocsp_exts =
-                d2i_X509_EXTENSIONS(NULL, &ext_data,
-                                    (int)PACKET_remaining(&exts));
-            if (s->tlsext_ocsp_exts == NULL || ext_data != PACKET_end(&exts)) {
-                *al = SSL_AD_DECODE_ERROR;
-                return 0;
-            }
-        }
-    } else
-#endif
-    {
-        /*
-         * We don't know what to do with any other type so ignore it.
-         */
-        s->tlsext_status_type = -1;
-    }
+    return 1;
+}
+
+static int init_ems(SSL *s, unsigned int context)
+{
+    if (!s->server)
+        s->s3->flags &= ~TLS1_FLAGS_RECEIVED_EXTMS;
 
     return 1;
 }
 
-#ifndef OPENSSL_NO_NEXTPROTONEG
-static int tls_parse_clienthello_npn(SSL *s, PACKET *pkt, int *al)
+static int final_ems(SSL *s, unsigned int context, int sent, int *al)
 {
-    if (s->s3->tmp.finish_md_len == 0) {
-        /*-
-         * We shouldn't accept this extension on a
-         * renegotiation.
-         *
-         * s->new_session will be set on renegotiation, but we
-         * probably shouldn't rely that it couldn't be set on
-         * the initial renegotiation too in certain cases (when
-         * there's some other reason to disallow resuming an
-         * earlier session -- the current code won't be doing
-         * anything like that, but this might change).
-         *
-         * A valid sign that there's been a previous handshake
-         * in this connection is if s->s3->tmp.finish_md_len >
-         * 0.  (We are talking about a check that will happen
-         * in the Hello protocol round, well before a new
-         * Finished message could have been computed.)
+    if (!s->server && s->hit) {
+        /*
+         * Check extended master secret extension is consistent with
+         * original session.
          */
-        s->s3->next_proto_neg_seen = 1;
+        if (!(s->s3->flags & TLS1_FLAGS_RECEIVED_EXTMS) !=
+            !(s->session->flags & SSL_SESS_FLAG_EXTMS)) {
+            *al = SSL_AD_HANDSHAKE_FAILURE;
+            SSLerr(SSL_F_FINAL_EMS, SSL_R_INCONSISTENT_EXTMS);
+            return 0;
+        }
     }
 
     return 1;
 }
-#endif
 
-/*
- * Save the ALPN extension in a ClientHello.
- * pkt: the contents of the ALPN extension, not including type and length.
- * al: a pointer to the  alert value to send in the event of a failure.
- * returns: 1 on success, 0 on error.
- */
-static int tls_parse_clienthello_alpn(SSL *s, PACKET *pkt, int *al)
+static int init_certificate_authorities(SSL *s, unsigned int context)
 {
-    PACKET protocol_list, save_protocol_list, protocol;
+    sk_X509_NAME_pop_free(s->s3->tmp.ca_names, X509_NAME_free);
+    s->s3->tmp.ca_names = NULL;
+    return 1;
+}
+
+static int tls_construct_certificate_authorities(SSL *s, WPACKET *pkt,
+                                                 unsigned int context, X509 *x,
+                                                 size_t chainidx, int *al)
+{
+    STACK_OF(X509_NAME) *ca_sk = SSL_get_client_CA_list(s);
 
-    if (s->s3->tmp.finish_md_len != 0)
+    if (ca_sk == NULL || sk_X509_NAME_num(ca_sk) == 0)
         return 1;
 
-    if (!PACKET_as_length_prefixed_2(pkt, &protocol_list)
-        || PACKET_remaining(&protocol_list) < 2) {
+    if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_certificate_authorities)
+        || !WPACKET_start_sub_packet_u16(pkt)
+        || !construct_ca_names(s, pkt)
+        || !WPACKET_close(pkt)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_CERTIFICATE_AUTHORITIES,
+               ERR_R_INTERNAL_ERROR);
+        return 0;
+    }
+
+    return 1;
+}
+
+static int tls_parse_certificate_authorities(SSL *s, PACKET *pkt,
+                                             unsigned int context, X509 *x,
+                                             size_t chainidx, int *al)
+{
+    if (!parse_ca_names(s, pkt, al))
+        return 0;
+    if (PACKET_remaining(pkt) != 0) {
         *al = SSL_AD_DECODE_ERROR;
         return 0;
     }
+    return 1;
+}
 
-    save_protocol_list = protocol_list;
-    do {
-        /* Protocol names can't be empty. */
-        if (!PACKET_get_length_prefixed_1(&protocol_list, &protocol)
-                || PACKET_remaining(&protocol) == 0) {
-            *al = SSL_AD_DECODE_ERROR;
-            return 0;
-        }
-    } while (PACKET_remaining(&protocol_list) != 0);
+#ifndef OPENSSL_NO_SRTP
+static int init_srtp(SSL *s, unsigned int context)
+{
+    if (s->server)
+        s->srtp_profile = NULL;
 
-    if (!PACKET_memdup(&save_protocol_list,
-                       &s->s3->alpn_proposed, &s->s3->alpn_proposed_len)) {
-        *al = TLS1_AD_INTERNAL_ERROR;
+    return 1;
+}
+#endif
+
+static int final_sig_algs(SSL *s, unsigned int context, int sent, int *al)
+{
+    if (!sent && SSL_IS_TLS13(s)) {
+        *al = TLS13_AD_MISSING_EXTENSION;
+        SSLerr(SSL_F_FINAL_SIG_ALGS, SSL_R_MISSING_SIGALGS_EXTENSION);
         return 0;
     }
 
     return 1;
 }
 
-#ifndef OPENSSL_NO_SRTP
-static int tls_parse_clienthello_use_srtp(SSL *s, PACKET *pkt, int *al)
+#ifndef OPENSSL_NO_EC
+static int final_key_share(SSL *s, unsigned int context, int sent, int *al)
 {
-    SRTP_PROTECTION_PROFILE *sprof;
-    STACK_OF(SRTP_PROTECTION_PROFILE) *srvr;
-    unsigned int ct, mki_len, id;
-    int i, srtp_pref;
-    PACKET subpkt;
-
-    /* Ignore this if we have no SRTP profiles */
-    if (SSL_get_srtp_profiles(s) == NULL)
+    if (!SSL_IS_TLS13(s))
         return 1;
 
-    /* Pull off the length of the cipher suite list  and check it is even */
-    if (!PACKET_get_net_2(pkt, &ct)
-        || (ct & 1) != 0 || !PACKET_get_sub_packet(pkt, &subpkt, ct)) {
-        SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_USE_SRTP,
-               SSL_R_BAD_SRTP_PROTECTION_PROFILE_LIST);
-        *al = SSL_AD_DECODE_ERROR;
+    /*
+     * If
+     *     we are a client
+     *     AND
+     *     we have no key_share
+     *     AND
+     *     (we are not resuming
+     *      OR the kex_mode doesn't allow non key_share resumes)
+     * THEN
+     *     fail;
+     */
+    if (!s->server
+            && !sent
+            && (!s->hit
+                || (s->ext.psk_kex_mode & TLSEXT_KEX_MODE_FLAG_KE) == 0)) {
+        /* Nothing left we can do - just fail */
+        *al = SSL_AD_HANDSHAKE_FAILURE;
+        SSLerr(SSL_F_FINAL_KEY_SHARE, SSL_R_NO_SUITABLE_KEY_SHARE);
         return 0;
     }
+    /*
+     * If
+     *     we are a server
+     *     AND
+     *     we have no key_share
+     * THEN
+     *     If
+     *         we didn't already send a HelloRetryRequest
+     *         AND
+     *         the client sent a key_share extension
+     *         AND
+     *         (we are not resuming
+     *          OR the kex_mode allows key_share resumes)
+     *         AND
+     *         a shared group exists
+     *     THEN
+     *         send a HelloRetryRequest
+     *     ELSE If
+     *         we are not resuming
+     *         OR
+     *         the kex_mode doesn't allow non key_share resumes
+     *     THEN
+     *         fail;
+     */
+    if (s->server && s->s3->peer_tmp == NULL) {
+        /* No suitable share */
+        if (s->hello_retry_request == 0 && sent
+                && (!s->hit
+                    || (s->ext.psk_kex_mode & TLSEXT_KEX_MODE_FLAG_KE_DHE)
+                       != 0)) {
+            const unsigned char *pcurves, *pcurvestmp, *clntcurves;
+            size_t num_curves, clnt_num_curves, i;
+            unsigned int group_id = 0;
+
+            /* Check if a shared group exists */
+
+            /* Get the clients list of supported groups. */
+            if (!tls1_get_curvelist(s, 1, &clntcurves, &clnt_num_curves)) {
+                *al = SSL_AD_INTERNAL_ERROR;
+                SSLerr(SSL_F_FINAL_KEY_SHARE, ERR_R_INTERNAL_ERROR);
+                return 0;
+            }
+
+            /* Get our list of available groups */
+            if (!tls1_get_curvelist(s, 0, &pcurves, &num_curves)) {
+                *al = SSL_AD_INTERNAL_ERROR;
+                SSLerr(SSL_F_FINAL_KEY_SHARE, ERR_R_INTERNAL_ERROR);
+                return 0;
+            }
 
-    srvr = SSL_get_srtp_profiles(s);
-    s->srtp_profile = NULL;
-    /* Search all profiles for a match initially */
-    srtp_pref = sk_SRTP_PROTECTION_PROFILE_num(srvr);
+            /* Find the first group we allow that is also in client's list */
+            for (i = 0, pcurvestmp = pcurves; i < num_curves;
+                 i++, pcurvestmp += 2) {
+                group_id = bytestogroup(pcurvestmp);
 
-    while (PACKET_remaining(&subpkt)) {
-        if (!PACKET_get_net_2(&subpkt, &id)) {
-            SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_USE_SRTP,
-                   SSL_R_BAD_SRTP_PROTECTION_PROFILE_LIST);
-            *al = SSL_AD_DECODE_ERROR;
-            return 0;
-        }
+                if (check_in_list(s, group_id, clntcurves, clnt_num_curves, 1))
+                    break;
+            }
 
-        /*
-         * Only look for match in profiles of higher preference than
-         * current match.
-         * If no profiles have been have been configured then this
-         * does nothing.
-         */
-        for (i = 0; i < srtp_pref; i++) {
-            sprof = sk_SRTP_PROTECTION_PROFILE_value(srvr, i);
-            if (sprof->id == id) {
-                s->srtp_profile = sprof;
-                srtp_pref = i;
-                break;
+            if (i < num_curves) {
+                /* A shared group exists so send a HelloRetryRequest */
+                s->s3->group_id = group_id;
+                s->hello_retry_request = 1;
+                return 1;
             }
         }
+        if (!s->hit
+                || (s->ext.psk_kex_mode & TLSEXT_KEX_MODE_FLAG_KE) == 0) {
+            /* Nothing left we can do - just fail */
+            *al = SSL_AD_HANDSHAKE_FAILURE;
+            SSLerr(SSL_F_FINAL_KEY_SHARE, SSL_R_NO_SUITABLE_KEY_SHARE);
+            return 0;
+        }
     }
 
+    /* We have a key_share so don't send any more HelloRetryRequest messages */
+    if (s->server)
+        s->hello_retry_request = 0;
+
     /*
-     * Now extract the MKI value as a sanity check, but discard it for now
+     * For a client side resumption with no key_share we need to generate
+     * the handshake secret (otherwise this is done during key_share
+     * processing).
      */
-    if (!PACKET_get_1(pkt, &mki_len)) {
-        SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_USE_SRTP,
-               SSL_R_BAD_SRTP_PROTECTION_PROFILE_LIST);
-        *al = SSL_AD_DECODE_ERROR;
-        return 0;
-    }
-
-    if (!PACKET_forward(pkt, mki_len)
-        || PACKET_remaining(pkt)) {
-        SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_USE_SRTP, SSL_R_BAD_SRTP_MKI_VALUE);
-        *al = SSL_AD_DECODE_ERROR;
+    if (!sent && !s->server && !tls13_generate_handshake_secret(s, NULL, 0)) {
+        *al = SSL_AD_INTERNAL_ERROR;
+        SSLerr(SSL_F_FINAL_KEY_SHARE, ERR_R_INTERNAL_ERROR);
         return 0;
     }
 
@@ -846,203 +1163,163 @@ static int tls_parse_clienthello_use_srtp(SSL *s, PACKET *pkt, int *al)
 }
 #endif
 
-static int tls_parse_clienthello_etm(SSL *s, PACKET *pkt, int *al)
+static int init_psk_kex_modes(SSL *s, unsigned int context)
 {
-    if (!(s->options & SSL_OP_NO_ENCRYPT_THEN_MAC))
-        s->s3->flags |= TLS1_FLAGS_ENCRYPT_THEN_MAC;
-
+    s->ext.psk_kex_mode = TLSEXT_KEX_MODE_FLAG_NONE;
     return 1;
 }
 
-/*
- * Checks a list of |groups| to determine if the |group_id| is in it. If it is
- * and |checkallow| is 1 then additionally check if the group is allowed to be
- * used. Returns 1 if the group is in the list (and allowed if |checkallow| is
- * 1) or 0 otherwise.
- */
-static int check_in_list(SSL *s, unsigned int group_id,
-                         const unsigned char *groups, size_t num_groups,
-                         int checkallow)
+int tls_psk_do_binder(SSL *s, const EVP_MD *md, const unsigned char *msgstart,
+                      size_t binderoffset, const unsigned char *binderin,
+                      unsigned char *binderout,
+                      SSL_SESSION *sess, int sign)
 {
-    size_t i;
-
-    if (groups == NULL || num_groups == 0)
-        return 0;
-
-    for (i = 0; i < num_groups; i++, groups += 2) {
-        unsigned int share_id = (groups[0] << 8) | (groups[1]);
-
-        if (group_id == share_id
-                && (!checkallow || tls_curve_allowed(s, groups,
-                                                     SSL_SECOP_CURVE_CHECK))) {
-            break;
-        }
+    EVP_PKEY *mackey = NULL;
+    EVP_MD_CTX *mctx = NULL;
+    unsigned char hash[EVP_MAX_MD_SIZE], binderkey[EVP_MAX_MD_SIZE];
+    unsigned char finishedkey[EVP_MAX_MD_SIZE], tmpbinder[EVP_MAX_MD_SIZE];
+    const char resumption_label[] = "resumption psk binder key";
+    size_t bindersize, hashsize = EVP_MD_size(md);
+    int ret = -1;
+
+    /* Generate the early_secret */
+    if (!tls13_generate_secret(s, md, NULL, sess->master_key,
+                               sess->master_key_length,
+                               (unsigned char *)&s->early_secret)) {
+        SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+        goto err;
     }
 
-    /* If i == num_groups then not in the list */
-    return i < num_groups;
-}
-
-/*
- * Process a key_share extension received in the ClientHello. |pkt| contains
- * the raw PACKET data for the extension. Returns 1 on success or 0 on failure.
- * If a failure occurs then |*al| is set to an appropriate alert value.
- */
-static int tls_parse_clienthello_key_share(SSL *s, PACKET *pkt, int *al)
-{
-    unsigned int group_id;
-    PACKET key_share_list, encoded_pt;
-    const unsigned char *clntcurves, *srvrcurves;
-    size_t clnt_num_curves, srvr_num_curves;
-    int group_nid, found = 0;
-    unsigned int curve_flags;
-
-    if (s->hit)
-        return 1;
-
-    /* Sanity check */
-    if (s->s3->peer_tmp != NULL) {
-        *al = SSL_AD_INTERNAL_ERROR;
-        SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_KEY_SHARE, ERR_R_INTERNAL_ERROR);
-        return 0;
+    /*
+     * Create the handshake hash for the binder key...the messages so far are
+     * empty!
+     */
+    mctx = EVP_MD_CTX_new();
+    if (mctx == NULL
+            || EVP_DigestInit_ex(mctx, md, NULL) <= 0
+            || EVP_DigestFinal_ex(mctx, hash, NULL) <= 0) {
+        SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+        goto err;
     }
 
-    if (!PACKET_as_length_prefixed_2(pkt, &key_share_list)) {
-        *al = SSL_AD_HANDSHAKE_FAILURE;
-        SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_KEY_SHARE, SSL_R_LENGTH_MISMATCH);
-        return 0;
+    /* Generate the binder key */
+    if (!tls13_hkdf_expand(s, md, s->early_secret,
+                           (unsigned char *)resumption_label,
+                           sizeof(resumption_label) - 1, hash, binderkey,
+                           hashsize)) {
+        SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+        goto err;
     }
 
-    /* Get our list of supported curves */
-    if (!tls1_get_curvelist(s, 0, &srvrcurves, &srvr_num_curves)) {
-        *al = SSL_AD_INTERNAL_ERROR;
-        SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_KEY_SHARE, ERR_R_INTERNAL_ERROR);
-        return 0;
+    /* Generate the finished key */
+    if (!tls13_derive_finishedkey(s, md, binderkey, finishedkey, hashsize)) {
+        SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+        goto err;
     }
 
-    /* Get the clients list of supported curves */
-    if (!tls1_get_curvelist(s, 1, &clntcurves, &clnt_num_curves)) {
-        *al = SSL_AD_INTERNAL_ERROR;
-        SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_KEY_SHARE, ERR_R_INTERNAL_ERROR);
-        return 0;
+    if (EVP_DigestInit_ex(mctx, md, NULL) <= 0) {
+        SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+        goto err;
     }
 
-    while (PACKET_remaining(&key_share_list) > 0) {
-        if (!PACKET_get_net_2(&key_share_list, &group_id)
-                || !PACKET_get_length_prefixed_2(&key_share_list, &encoded_pt)
-                || PACKET_remaining(&encoded_pt) == 0) {
-            *al = SSL_AD_HANDSHAKE_FAILURE;
-            SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_KEY_SHARE,
-                   SSL_R_LENGTH_MISMATCH);
-            return 0;
+    /*
+     * Get a hash of the ClientHello up to the start of the binders. If we are
+     * following a HelloRetryRequest then this includes the hash of the first
+     * ClientHello and the HelloRetryRequest itself.
+     */
+    if (s->hello_retry_request) {
+        size_t hdatalen;
+        void *hdata;
+
+        hdatalen = BIO_get_mem_data(s->s3->handshake_buffer, &hdata);
+        if (hdatalen <= 0) {
+            SSLerr(SSL_F_TLS_PSK_DO_BINDER, SSL_R_BAD_HANDSHAKE_LENGTH);
+            goto err;
         }
 
         /*
-         * If we already found a suitable key_share we loop through the
-         * rest to verify the structure, but don't process them.
+         * For servers the handshake buffer data will include the second
+         * ClientHello - which we don't want - so we need to take that bit off.
          */
-        if (found)
-            continue;
-
-        /* Check if this share is in supported_groups sent from client */
-        if (!check_in_list(s, group_id, clntcurves, clnt_num_curves, 0)) {
-            *al = SSL_AD_HANDSHAKE_FAILURE;
-            SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_KEY_SHARE, SSL_R_BAD_KEY_SHARE);
-            return 0;
-        }
-
-        /* Check if this share is for a group we can use */
-        if (!check_in_list(s, group_id, srvrcurves, srvr_num_curves, 1)) {
-            /* Share not suitable */
-            continue;
-        }
-
-        group_nid = tls1_ec_curve_id2nid(group_id, &curve_flags);
-
-        if (group_nid == 0) {
-            *al = SSL_AD_INTERNAL_ERROR;
-            SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_KEY_SHARE,
-                   SSL_R_UNABLE_TO_FIND_ECDH_PARAMETERS);
-            return 0;
-        }
-
-        if ((curve_flags & TLS_CURVE_TYPE) == TLS_CURVE_CUSTOM) {
-            /* Can happen for some curves, e.g. X25519 */
-            EVP_PKEY *key = EVP_PKEY_new();
-
-            if (key == NULL || !EVP_PKEY_set_type(key, group_nid)) {
-                *al = SSL_AD_INTERNAL_ERROR;
-                SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_KEY_SHARE, ERR_R_EVP_LIB);
-                EVP_PKEY_free(key);
-                return 0;
-            }
-            s->s3->peer_tmp = key;
-        } else {
-            /* Set up EVP_PKEY with named curve as parameters */
-            EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_EC, NULL);
-            if (pctx == NULL
-                    || EVP_PKEY_paramgen_init(pctx) <= 0
-                    || EVP_PKEY_CTX_set_ec_paramgen_curve_nid(pctx,
-                                                              group_nid) <= 0
-                    || EVP_PKEY_paramgen(pctx, &s->s3->peer_tmp) <= 0) {
-                *al = SSL_AD_INTERNAL_ERROR;
-                SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_KEY_SHARE, ERR_R_EVP_LIB);
-                EVP_PKEY_CTX_free(pctx);
-                return 0;
+        if (s->server) {
+            if (hdatalen < s->init_num + SSL3_HM_HEADER_LENGTH) {
+                SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+                goto err;
             }
-            EVP_PKEY_CTX_free(pctx);
-            pctx = NULL;
+            hdatalen -= s->init_num + SSL3_HM_HEADER_LENGTH;
         }
-        s->s3->group_id = group_id;
 
-        if (!EVP_PKEY_set1_tls_encodedpoint(s->s3->peer_tmp,
-                PACKET_data(&encoded_pt),
-                PACKET_remaining(&encoded_pt))) {
-            *al = SSL_AD_DECODE_ERROR;
-            SSLerr(SSL_F_TLS_PARSE_CLIENTHELLO_KEY_SHARE, SSL_R_BAD_ECPOINT);
-            return 0;
+        if (EVP_DigestUpdate(mctx, hdata, hdatalen) <= 0) {
+            SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+            goto err;
         }
+    }
 
-        found = 1;
+    if (EVP_DigestUpdate(mctx, msgstart, binderoffset) <= 0
+            || EVP_DigestFinal_ex(mctx, hash, NULL) <= 0) {
+        SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+        goto err;
     }
 
-    return 1;
-}
+    mackey = EVP_PKEY_new_mac_key(EVP_PKEY_HMAC, NULL, finishedkey, hashsize);
+    if (mackey == NULL) {
+        SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+        goto err;
+    }
 
-#ifndef OPENSSL_NO_EC
-static int tls_parse_clienthello_supported_groups(SSL *s, PACKET *pkt, int *al)
-{
-    PACKET supported_groups_list;
+    if (!sign)
+        binderout = tmpbinder;
 
-    /* Each group is 2 bytes and we must have at least 1. */
-    if (!PACKET_as_length_prefixed_2(pkt, &supported_groups_list)
-            || PACKET_remaining(&supported_groups_list) == 0
-            || (PACKET_remaining(&supported_groups_list) % 2) != 0) {
-        *al = SSL_AD_DECODE_ERROR;
-        return 0;
+    bindersize = hashsize;
+    if (EVP_DigestSignInit(mctx, NULL, md, NULL, mackey) <= 0
+            || EVP_DigestSignUpdate(mctx, hash, hashsize) <= 0
+            || EVP_DigestSignFinal(mctx, binderout, &bindersize) <= 0
+            || bindersize != hashsize) {
+        SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+        goto err;
     }
 
-    if (!s->hit
-            && !PACKET_memdup(&supported_groups_list,
-                              &s->session->tlsext_supportedgroupslist,
-                              &s->session->tlsext_supportedgroupslist_length)) {
-        *al = SSL_AD_DECODE_ERROR;
-        return 0;
+    if (sign) {
+        ret = 1;
+    } else {
+        /* HMAC keys can't do EVP_DigestVerify* - use CRYPTO_memcmp instead */
+        ret = (CRYPTO_memcmp(binderin, binderout, hashsize) == 0);
     }
 
-    return 1;
+ err:
+    OPENSSL_cleanse(binderkey, sizeof(binderkey));
+    OPENSSL_cleanse(finishedkey, sizeof(finishedkey));
+    EVP_PKEY_free(mackey);
+    EVP_MD_CTX_free(mctx);
+
+    return ret;
 }
-#endif
 
-static int tls_parse_clienthello_ems(SSL *s, PACKET *pkt, int *al)
+static int final_early_data(SSL *s, unsigned int context, int sent, int *al)
 {
-    /* The extension must always be empty */
-    if (PACKET_remaining(pkt) != 0) {
-        *al = SSL_AD_DECODE_ERROR;
-        return 0;
-    }
+    if (!s->server || !sent)
+        return 1;
+
+    if (s->max_early_data == 0
+            || !s->hit
+            || s->session->ext.tick_identity != 0
+            || s->early_data_state != SSL_EARLY_DATA_ACCEPTING
+            || !s->ext.early_data_ok
+            || s->hello_retry_request
+            || s->s3->alpn_selected_len != s->session->ext.alpn_selected_len
+            || (s->s3->alpn_selected_len > 0
+                && memcmp(s->s3->alpn_selected, s->session->ext.alpn_selected,
+                          s->s3->alpn_selected_len) != 0)) {
+        s->ext.early_data = SSL_EARLY_DATA_REJECTED;
+    } else {
+        s->ext.early_data = SSL_EARLY_DATA_ACCEPTED;
 
-    s->s3->flags |= TLS1_FLAGS_RECEIVED_EXTMS;
+        if (!tls13_change_cipher_state(s,
+                    SSL3_CC_EARLY | SSL3_CHANGE_CIPHER_SERVER_READ)) {
+            *al = SSL_AD_INTERNAL_ERROR;
+            return 0;
+        }
+    }
 
     return 1;
 }