Fix a bundle of trailing spaces in several files
[openssl.git] / ssl / statem / extensions.c
index 898b9b9..b4d85d9 100644 (file)
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 2016-2017 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
  * https://www.openssl.org/source/license.html
  */
 
-#include <stdlib.h>
+#include <string.h>
 #include "../ssl_locl.h"
 #include "statem_locl.h"
 
-typedef struct {
-    /* The ID for the extension */
+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 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
+#ifndef OPENSSL_NO_NEXTPROTONEG
+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 EXT_RETURN 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
+#ifndef OPENSSL_NO_SRTP
+static int init_srtp(SSL *s, unsigned int context);
+#endif
+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);
+
+/* 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);
-    int (*server_construct)(SSL *s, WPACKET *pkt, int *al);
-    int (*client_construct)(SSL *s, WPACKET *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 */
+    EXT_RETURN (*construct_stoc)(SSL *s, WPACKET *pkt, unsigned int context,
+                                 X509 *x, size_t chainidx, int *al);
+    /* Construct extension sent from client to server */
+    EXT_RETURN (*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;
 
 /*
- * TODO(TLS1.3): Temporarily modified the definitions below to put all TLS1.3
- * extensions in the ServerHello for now. That needs to be put back to correct
- * setting once encrypted extensions is working properly.
+ * 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_client_renegotiate,
-        NULL,
-        tls_construct_server_renegotiate,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_SSL3_ALLOWED
-        | EXT_TLS1_2_AND_BELOW_ONLY
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO
+        | SSL_EXT_SSL3_ALLOWED | SSL_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_client_server_name,
-        NULL,
-        tls_construct_server_server_name,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO
-        | /*EXT_TLS1_3_ENCRYPTED_EXTENSIONS*/EXT_TLS1_3_SERVER_HELLO
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO
+        | SSL_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_client_srp,
-        NULL,
-        NULL,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        SSL_EXT_CLIENT_HELLO | SSL_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_client_ec_pt_formats,
-        NULL,
-        tls_construct_server_ec_pt_formats,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO
+        | SSL_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_client_supported_groups,
-        NULL,
-        NULL /* TODO(TLS1.3): Need to add this */,
-        NULL,
-        EXT_CLIENT_HELLO
-        | /*EXT_TLS1_3_ENCRYPTED_EXTENSIONS*/EXT_TLS1_3_SERVER_HELLO
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS,
+        NULL, tls_parse_ctos_supported_groups, NULL,
+        tls_construct_stoc_supported_groups,
+        tls_construct_ctos_supported_groups, NULL
     },
+#else
+    INVALID_EXTENSION,
+    INVALID_EXTENSION,
 #endif
     {
         TLSEXT_TYPE_session_ticket,
-        tls_parse_client_session_ticket,
-        NULL,
-        tls_construct_server_session_ticket,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO
+        | SSL_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_client_sig_algs,
-        NULL,
-        NULL,
-        NULL,
-        EXT_CLIENT_HELLO
+        SSL_EXT_CLIENT_HELLO | SSL_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_client_status_request,
-        NULL,
-        tls_construct_server_status_request,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO
-        | /*EXT_TLS1_3_CERTIFICATE*/EXT_TLS1_3_SERVER_HELLO
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO
+        | SSL_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_client_npn,
-        NULL,
-        tls_construct_server_next_proto_neg,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO
+        | SSL_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_client_alpn,
-        NULL,
-        tls_construct_server_alpn,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO
-        | /*EXT_TLS1_3_ENCRYPTED_EXTENSIONS*/EXT_TLS1_3_SERVER_HELLO
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO
+        | SSL_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_client_use_srtp,
-        NULL,
-        tls_construct_server_use_srtp,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO
-        | EXT_TLS1_3_ENCRYPTED_EXTENSIONS | EXT_DTLS_ONLY
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO
+        | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS | SSL_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_client_etm,
-        NULL,
-        tls_construct_server_etm,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO
+        | SSL_EXT_TLS1_2_AND_BELOW_ONLY,
+        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,
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO
+        | SSL_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,
-        NULL,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO
-        | /*EXT_TLS1_3_CERTIFICATE*/EXT_TLS1_3_SERVER_HELLO
+        NULL, tls_parse_stoc_sct, NULL, tls_construct_ctos_sct,  NULL
     },
+#else
+    INVALID_EXTENSION,
+#endif
     {
         TLSEXT_TYPE_extended_master_secret,
-        tls_parse_client_ems,
-        NULL,
-        tls_construct_server_ems,
-        NULL,
-        EXT_CLIENT_HELLO | EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO
+        | SSL_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,
-        NULL,
-        NULL,
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS_IMPLEMENTATION_ONLY
+        | SSL_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,
-        NULL,
-        NULL,
-        EXT_CLIENT_HELLO
+        TLSEXT_TYPE_psk_kex_modes,
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS_IMPLEMENTATION_ONLY
+        | SSL_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_client_key_share,
-        NULL,
-        tls_construct_server_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
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_3_SERVER_HELLO
+        | SSL_EXT_TLS1_3_HELLO_RETRY_REQUEST | SSL_EXT_TLS_IMPLEMENTATION_ONLY
+        | SSL_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,
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_3_HELLO_RETRY_REQUEST
+        | SSL_EXT_TLS_IMPLEMENTATION_ONLY | SSL_EXT_TLS1_3_ONLY,
+        NULL, NULL, tls_parse_stoc_cookie, NULL, tls_construct_ctos_cookie,
+        NULL
     },
     {
         /*
@@ -193,171 +293,253 @@ static const EXTENSION_DEFINITION ext_defs[] = {
          * SSL_OP_CRYPTOPRO_TLSEXT_BUG is set
          */
         TLSEXT_TYPE_cryptopro_bug,
+        SSL_EXT_TLS1_2_SERVER_HELLO | SSL_EXT_TLS1_2_AND_BELOW_ONLY,
+        NULL, NULL, NULL, tls_construct_stoc_cryptopro_bug, NULL, NULL
+    },
+    {
+        TLSEXT_TYPE_early_data,
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS
+        | SSL_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,
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_3_CERTIFICATE_REQUEST
+        | SSL_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,
+        SSL_EXT_CLIENT_HELLO,
         NULL,
-        NULL,
-        tls_construct_server_cryptopro_bug,
-        NULL,
-        EXT_TLS1_2_SERVER_HELLO | EXT_TLS1_2_AND_BELOW_ONLY
+        /* 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,
+        SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_3_SERVER_HELLO
+        | SSL_EXT_TLS_IMPLEMENTATION_ONLY | SSL_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)
+/* Check whether an extension's context matches the current context */
+static int validate_context(SSL *s, unsigned int extctx, unsigned int thisctx)
 {
-    const RAW_EXTENSION *e1 = (const RAW_EXTENSION *)p1;
-    const RAW_EXTENSION *e2 = (const RAW_EXTENSION *)p2;
+    /* Check we're allowed to use this extension in this context */
+    if ((thisctx & extctx) == 0)
+        return 0;
 
-    if (e1->type < e2->type)
-        return -1;
-    else if (e1->type > e2->type)
-        return 1;
+    if (SSL_IS_DTLS(s)) {
+        if ((extctx & SSL_EXT_TLS_ONLY) != 0)
+            return 0;
+    } else if ((extctx & SSL_EXT_DTLS_ONLY) != 0) {
+        return 0;
+    }
 
-    return 0;
+    return 1;
 }
 
 /*
  * 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
+ * the definition for the extension we found.
  */
-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) {
-            /* Check we're allowed to use this extension in this context */
-            if ((context & ext_defs[i].context) == 0)
+    for (i = 0, thisext = ext_defs; i < builtin_num; i++, thisext++) {
+        if (type == thisext->type) {
+            if (!validate_context(s, thisext->context, context))
                 return 0;
 
-            if (SSL_IS_DTLS(s)) {
-                if ((ext_defs[i].context & EXT_TLS_ONLY) != 0)
-                    return 0;
-            } else if ((ext_defs[i].context & EXT_DTLS_ONLY) != 0) {
-                    return 0;
-            }
+            *found = &rawexlist[i];
+            return 1;
+        }
+    }
+
+    /* Check the custom extensions */
+    if (meths != NULL) {
+        size_t offset = 0;
+        ENDPOINT role = ENDPOINT_BOTH;
+        custom_ext_method *meth = NULL;
 
+        if ((context & SSL_EXT_CLIENT_HELLO) != 0)
+            role = ENDPOINT_SERVER;
+        else if ((context & SSL_EXT_TLS1_2_SERVER_HELLO) != 0)
+            role = ENDPOINT_CLIENT;
+
+        meth = custom_ext_find(meths, role, type, &offset);
+        if (meth != NULL) {
+            if (!validate_context(s, meth->context, context))
+                return 0;
+            *found = &rawexlist[offset + builtin_num];
             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)
+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 & SSL_EXT_TLS_IMPLEMENTATION_ONLY) != 0)
+            || (s->version == SSL3_VERSION
+                    && (extctx & SSL_EXT_SSL3_ALLOWED) == 0)
+            || (SSL_IS_TLS13(s)
+                && (extctx & SSL_EXT_TLS1_2_AND_BELOW_ONLY) != 0)
+            || (!SSL_IS_TLS13(s) && (extctx & SSL_EXT_TLS1_3_ONLY) != 0)
+            || (s->hit && (extctx & SSL_EXT_IGNORE_ON_RESUMPTION) != 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 if |init| is nonzero (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,
+                           int init)
 {
     PACKET extensions = *packet;
-    size_t num_extensions = 0, i = 0;
+    size_t i = 0;
+    size_t num_exts;
+    custom_ext_methods *exts = &s->cert->custext;
     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 & SSL_EXT_CLIENT_HELLO) != 0)
+        custom_ext_init(&s->cert->custext);
+
+    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;
+        unsigned int type, idx;
         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 & SSL_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);
+        idx = thisex - raw_extensions;
+        /*-
+         * Check that we requested this extension (if appropriate). Requests can
+         * be sent in the ClientHello and CertificateRequest. Unsolicited
+         * extensions can be sent in the NewSessionTicket. We only do this for
+         * the built-in extensions. Custom extensions have a different but
+         * similar check elsewhere.
+         * Special cases:
+         * - The HRR cookie extension is unsolicited
+         * - The renegotiate extension is unsolicited (the client signals
+         *   support via an SCSV)
+         * - The signed_certificate_timestamp extension can be provided by a
+         * custom extension or by the built-in version. We let the extension
+         * itself handle unsolicited response checks.
+         */
+        if (idx < OSSL_NELEM(ext_defs)
+                && (context & (SSL_EXT_CLIENT_HELLO
+                               | SSL_EXT_TLS1_3_CERTIFICATE_REQUEST
+                               | SSL_EXT_TLS1_3_NEW_SESSION_TICKET)) == 0
+                && type != TLSEXT_TYPE_cookie
+                && type != TLSEXT_TYPE_renegotiate
+                && type != TLSEXT_TYPE_signed_certificate_timestamp
+                && (s->ext.extflags[idx] & SSL_EXT_FLAG_SENT) == 0) {
+            SSLerr(SSL_F_TLS_COLLECT_EXTENSIONS, SSL_R_UNSOLICITED_EXTENSION);
+            *al = SSL_AD_UNSUPPORTED_EXTENSION;
             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);
-            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;
+    if (init) {
+        /*
+         * 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;
             }
         }
     }
 
     *res = raw_extensions;
-    *numfound = num_extensions;
+    if (len != NULL)
+        *len = num_exts;
     return 1;
 
  err:
@@ -365,168 +547,840 @@ int tls_collect_extensions(SSL *s, PACKET *packet, unsigned int context,
     return 0;
 }
 
-int tls_parse_all_extensions(SSL *s, int context, 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;
-
-            /* Check if 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))
-                continue;
-        }
+    currext->parsed = 1;
 
-        if (parser == NULL) {
-            /*
-             * Could be a custom extension. We only allow this if it is a non
-             * resumed session on the server side.
-             * 
-             * 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;
+    if (idx < OSSL_NELEM(ext_defs)) {
+        /* We are handling a built-in extension */
+        const EXTENSION_DEFINITION *extdef = &ext_defs[idx];
 
-            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;
+
+        if (parser != NULL)
+            return parser(s, &currext->data, context, x, chainidx, al);
+
+        /*
+         * If the parser is NULL we fall through to the custom extension
+         * processing
+         */
     }
 
+    /* Parse custom extensions */
+    if (custom_ext_parse(s, context, currext->type,
+                         PACKET_data(&currext->data),
+                         PACKET_remaining(&currext->data),
+                         x, chainidx, al) <= 0)
+        return 0;
+
     return 1;
 }
 
 /*
- * 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.
+ * Parse all remaining extensions that have not yet been parsed. Also calls the
+ * finalisation for all extensions at the end if |fin| is nonzero, 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.
  */
-int tls_parse_extension(SSL *s, int type, int context, RAW_EXTENSION *exts,
-                        size_t numexts, int *al)
+int tls_parse_all_extensions(SSL *s, int context, RAW_EXTENSION *exts, X509 *x,
+                             size_t chainidx, int *al, int fin)
 {
-    RAW_EXTENSION *ext = tls_get_extension_by_type(exts, numexts, type);
+    size_t i, numexts = OSSL_NELEM(ext_defs);
+    const EXTENSION_DEFINITION *thisexd;
 
-    if (ext == NULL)
-        return 1;
+    /* Calculate the number of extensions in the extensions list */
+    numexts += s->cert->custext.meths_count;
+
+    /* 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 (fin) {
+        /*
+         * 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;
+        }
+    }
 
-    return tls_parse_all_extensions(s, context, ext, 1, al);
+    return 1;
 }
 
+int should_add_extension(SSL *s, unsigned int extctx, unsigned int thisctx,
+                         int max_version)
+{
+    /* Skip if not relevant for our context */
+    if ((extctx & thisctx) == 0)
+        return 0;
+
+    /* Check if this extension is defined for our protocol. If not, skip */
+    if ((SSL_IS_DTLS(s) && (extctx & SSL_EXT_TLS_IMPLEMENTATION_ONLY) != 0)
+            || (s->version == SSL3_VERSION
+                    && (extctx & SSL_EXT_SSL3_ALLOWED) == 0)
+            || (SSL_IS_TLS13(s)
+                && (extctx & SSL_EXT_TLS1_2_AND_BELOW_ONLY) != 0)
+            || (!SSL_IS_TLS13(s)
+                && (extctx & SSL_EXT_TLS1_3_ONLY) != 0
+                && (thisctx & SSL_EXT_CLIENT_HELLO) == 0)
+            || ((extctx & SSL_EXT_TLS1_3_ONLY) != 0
+                && (thisctx & SSL_EXT_CLIENT_HELLO) != 0
+                && (SSL_IS_DTLS(s) || max_version < TLS1_3_VERSION)))
+        return 0;
+
+    return 1;
+}
+
+/*
+ * 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,
-                             int *al)
+                             X509 *x, size_t chainidx, int *al)
 {
-    size_t loop;
-    int addcustom = 0;
+    size_t i;
+    int min_version, max_version = 0, reason, tmpal;
+    const EXTENSION_DEFINITION *thisexd;
 
     /*
-     * Normally if something goes wrong during construction its an internal
+     * Normally if something goes wrong during construction it's an internal
      * error. We can always override this later.
      */
-    *al = SSL_AD_INTERNAL_ERROR;
+    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,
+            || ((context &
+                 (SSL_EXT_CLIENT_HELLO | SSL_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);
-        return 0;
+        goto err;
+    }
+
+    if ((context & SSL_EXT_CLIENT_HELLO) != 0) {
+        reason = ssl_get_min_max_version(s, &min_version, &max_version);
+        if (reason != 0) {
+            SSLerr(SSL_F_TLS_CONSTRUCT_EXTENSIONS, reason);
+            goto err;
+        }
+    }
+
+    /* Add custom extensions first */
+    if ((context & SSL_EXT_CLIENT_HELLO) != 0) {
+        /* On the server side with initiase during ClientHello parsing */
+        custom_ext_init(&s->cert->custext);
+    }
+    if (!custom_ext_add(s, context, pkt, x, chainidx, max_version, &tmpal)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_EXTENSIONS, ERR_R_INTERNAL_ERROR);
+        goto err;
     }
 
-    for (loop = 0; loop < OSSL_NELEM(ext_defs); loop++) {
-        int (*construct)(SSL *s, WPACKET *pkt, int *al);
+    for (i = 0, thisexd = ext_defs; i < OSSL_NELEM(ext_defs); i++, thisexd++) {
+        EXT_RETURN (*construct)(SSL *s, WPACKET *pkt, unsigned int context,
+                                X509 *x, size_t chainidx, int *al);
+        EXT_RETURN ret;
 
         /* Skip if not relevant for our context */
-        if ((ext_defs[loop].context & context) == 0)
+        if (!should_add_extension(s, thisexd->context, context, max_version))
             continue;
 
-        construct = s->server ? ext_defs[loop].server_construct
-                              : ext_defs[loop].client_construct;
-
-        /* Check if this extension is defined for our protocol. If not, skip */
-        if ((SSL_IS_DTLS(s)
-                    && (ext_defs[loop].context & EXT_TLS_IMPLEMENTATION_ONLY)
-                       != 0)
-                || (s->version == SSL3_VERSION
-                        && (ext_defs[loop].context & EXT_SSL3_ALLOWED) == 0)
-                || (SSL_IS_TLS13(s)
-                    && (ext_defs[loop].context & EXT_TLS1_2_AND_BELOW_ONLY)
-                       != 0)
-                || (!SSL_IS_TLS13(s)
-                    && (ext_defs[loop].context & EXT_TLS1_3_ONLY) != 0
-                    && (context & EXT_CLIENT_HELLO) == 0)
-                || construct == NULL)
+        construct = s->server ? thisexd->construct_stoc
+                              : thisexd->construct_ctos;
+
+        if (construct == NULL)
             continue;
 
-        if (!construct(s, pkt, al))
+        ret = construct(s, pkt, context, x, chainidx, &tmpal);
+        if (ret == EXT_RETURN_FAIL)
+            goto err;
+        if (ret == EXT_RETURN_SENT
+                && (context & (SSL_EXT_CLIENT_HELLO
+                               | SSL_EXT_TLS1_3_CERTIFICATE_REQUEST
+                               | SSL_EXT_TLS1_3_NEW_SESSION_TICKET)) != 0)
+            s->ext.extflags[i] |= SSL_EXT_FLAG_SENT;
+    }
+
+    if (!WPACKET_close(pkt)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_EXTENSIONS, ERR_R_INTERNAL_ERROR);
+        goto err;
+    }
+
+    return 1;
+
+ err:
+    *al = tmpal;
+    return 0;
+}
+
+/*
+ * 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)
+{
+    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;
+        }
+
+        return 1;
     }
 
-    /* Add custom extensions */
-    if ((context & EXT_CLIENT_HELLO) != 0) {
-        custom_ext_init(&s->cert->cli_ext);
-        addcustom = 1;
-    } else if ((context & EXT_TLS1_2_SERVER_HELLO) != 0) {
+    /* 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;
+}
+
+static int init_server_name(SSL *s, unsigned int context)
+{
+    if (s->server)
+        s->servername_done = 0;
+
+    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;
+
+    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
+
+static int init_session_ticket(SSL *s, unsigned int context)
+{
+    if (!s->server)
+        s->ext.ticket_expected = 0;
+
+    return 1;
+}
+
+#ifndef OPENSSL_NO_OCSP
+static int init_status_request(SSL *s, unsigned int context)
+{
+    if (s->server) {
+        s->ext.status_type = TLSEXT_STATUSTYPE_nothing;
+    } else {
         /*
-         * 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.
+         * Ensure we get sensible values passed to tlsext_status_cb in the event
+         * that we don't receive a status message
          */
-        addcustom = 1;
+        OPENSSL_free(s->ext.ocsp.resp);
+        s->ext.ocsp.resp = NULL;
+        s->ext.ocsp.resp_len = 0;
     }
 
-    if (addcustom && !custom_ext_add(s, s->server, pkt, al)) {
-        SSLerr(SSL_F_TLS_CONSTRUCT_EXTENSIONS, ERR_R_INTERNAL_ERROR);
+    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 init_alpn(SSL *s, unsigned int context)
+{
+    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;
+    }
+    return 1;
+}
+
+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 if (r == SSL_TLSEXT_ERR_NOACK) {
+            /* Behave as if no callback was present. */
+            return 1;
+        } else {
+            *al = SSL_AD_NO_APPLICATION_PROTOCOL;
+            return 0;
+        }
+    }
+
+    return 1;
+}
+
+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;
+
+    return 1;
+}
+
+#ifndef OPENSSL_NO_SRP
+static int init_srp(SSL *s, unsigned int context)
+{
+    OPENSSL_free(s->srp_ctx.login);
+    s->srp_ctx.login = NULL;
+
+    return 1;
+}
+#endif
+
+static int init_etm(SSL *s, unsigned int context)
+{
+    s->ext.use_etm = 0;
+
+    return 1;
+}
+
+static int init_ems(SSL *s, unsigned int context)
+{
+    if (!s->server)
+        s->s3->flags &= ~TLS1_FLAGS_RECEIVED_EXTMS;
+
+    return 1;
+}
+
+static int final_ems(SSL *s, unsigned int context, int sent, int *al)
+{
+    if (!s->server && s->hit) {
+        /*
+         * Check extended master secret extension is consistent with
+         * original session.
+         */
+        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;
+}
+
+static int init_certificate_authorities(SSL *s, unsigned int context)
+{
+    sk_X509_NAME_pop_free(s->s3->tmp.peer_ca_names, X509_NAME_free);
+    s->s3->tmp.peer_ca_names = NULL;
+    return 1;
+}
+
+static EXT_RETURN tls_construct_certificate_authorities(SSL *s, WPACKET *pkt,
+                                                        unsigned int context,
+                                                        X509 *x,
+                                                        size_t chainidx,
+                                                        int *al)
+{
+    const STACK_OF(X509_NAME) *ca_sk = SSL_get0_CA_list(s);
+
+    if (ca_sk == NULL || sk_X509_NAME_num(ca_sk) == 0)
+        return EXT_RETURN_NOT_SENT;
+
+    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 EXT_RETURN_FAIL;
+    }
+
+    return EXT_RETURN_SENT;
+}
+
+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;
+}
 
-    if (!WPACKET_close(pkt)) {
-        SSLerr(SSL_F_TLS_CONSTRUCT_EXTENSIONS, ERR_R_INTERNAL_ERROR);
+#ifndef OPENSSL_NO_SRTP
+static int init_srtp(SSL *s, unsigned int context)
+{
+    if (s->server)
+        s->srtp_profile = NULL;
+
+    return 1;
+}
+#endif
+
+static int final_sig_algs(SSL *s, unsigned int context, int sent, int *al)
+{
+    if (!sent && SSL_IS_TLS13(s) && !s->hit) {
+        *al = TLS13_AD_MISSING_EXTENSION;
+        SSLerr(SSL_F_FINAL_SIG_ALGS, SSL_R_MISSING_SIGALGS_EXTENSION);
+        return 0;
+    }
+
+    return 1;
+}
+
+#ifndef OPENSSL_NO_EC
+static int final_key_share(SSL *s, unsigned int context, int sent, int *al)
+{
+    if (!SSL_IS_TLS13(s))
+        return 1;
+
+    /* Nothing to do for key_share in an HRR */
+    if ((context & SSL_EXT_TLS1_3_HELLO_RETRY_REQUEST) != 0)
+        return 1;
+
+    /*
+     * 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_MISSING_EXTENSION;
+        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;
+            }
+
+            /* 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);
+
+                if (check_in_list(s, group_id, clntcurves, clnt_num_curves, 1))
+                    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 */
+            if (!sent)
+                *al = SSL_AD_MISSING_EXTENSION;
+            else
+                *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;
+
+    /*
+     * 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 (!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;
+    }
+
+    return 1;
+}
+#endif
+
+static int init_psk_kex_modes(SSL *s, unsigned int context)
+{
+    s->ext.psk_kex_mode = TLSEXT_KEX_MODE_FLAG_NONE;
+    return 1;
+}
+
+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)
+{
+    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[] = "res binder";
+    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;
+    }
+
+    /*
+     * 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;
+    }
+
+    /* 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;
+    }
+
+    /* 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;
+    }
+
+    if (EVP_DigestInit_ex(mctx, md, NULL) <= 0) {
+        SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+        goto err;
+    }
+
+    /*
+     * 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;
+        }
+
+        /*
+         * 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 (s->server) {
+            PACKET hashprefix, msg;
+
+            /* Find how many bytes are left after the first two messages */
+            if (!PACKET_buf_init(&hashprefix, hdata, hdatalen)
+                    || !PACKET_forward(&hashprefix, 1)
+                    || !PACKET_get_length_prefixed_3(&hashprefix, &msg)
+                    || !PACKET_forward(&hashprefix, 1)
+                    || !PACKET_get_length_prefixed_3(&hashprefix, &msg)) {
+                SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+                goto err;
+            }
+            hdatalen -= PACKET_remaining(&hashprefix);
+        }
+
+        if (EVP_DigestUpdate(mctx, hdata, hdatalen) <= 0) {
+            SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+            goto err;
+        }
+    }
+
+    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;
+    }
+
+    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;
+    }
+
+    if (!sign)
+        binderout = tmpbinder;
+
+    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 (sign) {
+        ret = 1;
+    } else {
+        /* HMAC keys can't do EVP_DigestVerify* - use CRYPTO_memcmp instead */
+        ret = (CRYPTO_memcmp(binderin, binderout, hashsize) == 0);
+    }
+
+ err:
+    OPENSSL_cleanse(binderkey, sizeof(binderkey));
+    OPENSSL_cleanse(finishedkey, sizeof(finishedkey));
+    EVP_PKEY_free(mackey);
+    EVP_MD_CTX_free(mctx);
+
+    return ret;
+}
+
+static int final_early_data(SSL *s, unsigned int context, int sent, int *al)
+{
+    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;
+
+        if (!tls13_change_cipher_state(s,
+                    SSL3_CC_EARLY | SSL3_CHANGE_CIPHER_SERVER_READ)) {
+            *al = SSL_AD_INTERNAL_ERROR;
+            return 0;
+        }
+    }
 
     return 1;
 }