ssl/t1_ext.c

   1 /*
   2  * Copyright 2014-2016 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the OpenSSL license (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 /* Custom extension utility functions */
  11
  12 #include <openssl/ct.h>
  13 #include "ssl_locl.h"
  14
  15 /* Find a custom extension from the list. */
  16 static custom_ext_method *custom_ext_find(const custom_ext_methods *exts,
  17                                           unsigned int ext_type)
  18 {
  19     size_t i;
  20     custom_ext_method *meth = exts->meths;
  21     for (i = 0; i < exts->meths_count; i++, meth++) {
  22         if (ext_type == meth->ext_type)
  23             return meth;
  24     }
  25     return NULL;
  26 }
  27
  28 /*
  29  * Initialise custom extensions flags to indicate neither sent nor received.
  30  */
  31 void custom_ext_init(custom_ext_methods *exts)
  32 {
  33     size_t i;
  34     custom_ext_method *meth = exts->meths;
  35     for (i = 0; i < exts->meths_count; i++, meth++)
  36         meth->ext_flags = 0;
  37 }
  38
  39 /* Pass received custom extension data to the application for parsing. */
  40 int custom_ext_parse(SSL *s, int server,
  41                      unsigned int ext_type,
  42                      const unsigned char *ext_data, size_t ext_size, int *al)
  43 {
  44     custom_ext_methods *exts = server ? &s->cert->srv_ext : &s->cert->cli_ext;
  45     custom_ext_method *meth;
  46     meth = custom_ext_find(exts, ext_type);
  47     /* If not found return success */
  48     if (!meth)
  49         return 1;
  50     if (!server) {
  51         /*
  52          * If it's ServerHello we can't have any extensions not sent in
  53          * ClientHello.
  54          */
  55         if (!(meth->ext_flags & SSL_EXT_FLAG_SENT)) {
  56             *al = TLS1_AD_UNSUPPORTED_EXTENSION;
  57             return 0;
  58         }
  59     }
  60     /* If already present it's a duplicate */
  61     if (meth->ext_flags & SSL_EXT_FLAG_RECEIVED) {
  62         *al = TLS1_AD_DECODE_ERROR;
  63         return 0;
  64     }
  65     meth->ext_flags |= SSL_EXT_FLAG_RECEIVED;
  66     /* If no parse function set return success */
  67     if (!meth->parse_cb)
  68         return 1;
  69
  70     return meth->parse_cb(s, ext_type, ext_data, ext_size, al, meth->parse_arg);
  71 }
  72
  73 /*
  74  * Request custom extension data from the application and add to the return
  75  * buffer.
  76  */
  77 int custom_ext_add(SSL *s, int server, WPACKET *pkt, int *al)
  78 {
  79     custom_ext_methods *exts = server ? &s->cert->srv_ext : &s->cert->cli_ext;
  80     custom_ext_method *meth;
  81     size_t i;
  82
  83     for (i = 0; i < exts->meths_count; i++) {
  84         const unsigned char *out = NULL;
  85         size_t outlen = 0;
  86
  87         meth = exts->meths + i;
  88
  89         if (server) {
  90             /*
  91              * For ServerHello only send extensions present in ClientHello.
  92              */
  93             if (!(meth->ext_flags & SSL_EXT_FLAG_RECEIVED))
  94                 continue;
  95             /* If callback absent for server skip it */
  96             if (!meth->add_cb)
  97                 continue;
  98         }
  99         if (meth->add_cb) {
 100             int cb_retval = 0;
 101             cb_retval = meth->add_cb(s, meth->ext_type,
 102                                      &out, &outlen, al, meth->add_arg);
 103             if (cb_retval < 0)
 104                 return 0;       /* error */
 105             if (cb_retval == 0)
 106                 continue;       /* skip this extension */
 107         }
 108
 109         if (!WPACKET_put_bytes_u16(pkt, meth->ext_type)
 110                 || !WPACKET_start_sub_packet_u16(pkt)
 111                 || (outlen > 0 && !WPACKET_memcpy(pkt, out, outlen))
 112                 || !WPACKET_close(pkt)) {
 113             *al = SSL_AD_INTERNAL_ERROR;
 114             return 0;
 115         }
 116         /*
 117          * We can't send duplicates: code logic should prevent this.
 118          */
 119         OPENSSL_assert(!(meth->ext_flags & SSL_EXT_FLAG_SENT));
 120         /*
 121          * Indicate extension has been sent: this is both a sanity check to
 122          * ensure we don't send duplicate extensions and indicates that it is
 123          * not an error if the extension is present in ServerHello.
 124          */
 125         meth->ext_flags |= SSL_EXT_FLAG_SENT;
 126         if (meth->free_cb)
 127             meth->free_cb(s, meth->ext_type, out, meth->add_arg);
 128     }
 129     return 1;
 130 }
 131
 132 /* Copy table of custom extensions */
 133 int custom_exts_copy(custom_ext_methods *dst, const custom_ext_methods *src)
 134 {
 135     if (src->meths_count) {
 136         dst->meths =
 137             OPENSSL_memdup(src->meths,
 138                            sizeof(custom_ext_method) * src->meths_count);
 139         if (dst->meths == NULL)
 140             return 0;
 141         dst->meths_count = src->meths_count;
 142     }
 143     return 1;
 144 }
 145
 146 void custom_exts_free(custom_ext_methods *exts)
 147 {
 148     OPENSSL_free(exts->meths);
 149 }
 150
 151 /* Set callbacks for a custom extension. */
 152 static int custom_ext_meth_add(custom_ext_methods *exts,
 153                                unsigned int ext_type,
 154                                custom_ext_add_cb add_cb,
 155                                custom_ext_free_cb free_cb,
 156                                void *add_arg,
 157                                custom_ext_parse_cb parse_cb, void *parse_arg)
 158 {
 159     custom_ext_method *meth, *tmp;
 160     /*
 161      * Check application error: if add_cb is not set free_cb will never be
 162      * called.
 163      */
 164     if (!add_cb && free_cb)
 165         return 0;
 166     /*
 167      * Don't add if extension supported internally, but make exception
 168      * for extension types that previously were not supported, but now are.
 169      */
 170     if (SSL_extension_supported(ext_type) &&
 171         ext_type != TLSEXT_TYPE_signed_certificate_timestamp)
 172         return 0;
 173     /* Extension type must fit in 16 bits */
 174     if (ext_type > 0xffff)
 175         return 0;
 176     /* Search for duplicate */
 177     if (custom_ext_find(exts, ext_type))
 178         return 0;
 179     tmp = OPENSSL_realloc(exts->meths,
 180                           (exts->meths_count + 1) * sizeof(custom_ext_method));
 181
 182     if (tmp == NULL) {
 183         OPENSSL_free(exts->meths);
 184         exts->meths = NULL;
 185         exts->meths_count = 0;
 186         return 0;
 187     }
 188
 189     exts->meths = tmp;
 190     meth = exts->meths + exts->meths_count;
 191     memset(meth, 0, sizeof(*meth));
 192     meth->parse_cb = parse_cb;
 193     meth->add_cb = add_cb;
 194     meth->free_cb = free_cb;
 195     meth->ext_type = ext_type;
 196     meth->add_arg = add_arg;
 197     meth->parse_arg = parse_arg;
 198     exts->meths_count++;
 199     return 1;
 200 }
 201
 202 /* Return true if a client custom extension exists, false otherwise */
 203 int SSL_CTX_has_client_custom_ext(const SSL_CTX *ctx, unsigned int ext_type)
 204 {
 205     return custom_ext_find(&ctx->cert->cli_ext, ext_type) != NULL;
 206 }
 207
 208 /* Application level functions to add custom extension callbacks */
 209 int SSL_CTX_add_client_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
 210                                   custom_ext_add_cb add_cb,
 211                                   custom_ext_free_cb free_cb,
 212                                   void *add_arg,
 213                                   custom_ext_parse_cb parse_cb, void *parse_arg)
 214 {
 215 #ifndef OPENSSL_NO_CT
 216     /*
 217      * We don't want applications registering callbacks for SCT extensions
 218      * whilst simultaneously using the built-in SCT validation features, as
 219      * these two things may not play well together.
 220      */
 221     if (ext_type == TLSEXT_TYPE_signed_certificate_timestamp &&
 222         SSL_CTX_ct_is_enabled(ctx))
 223         return 0;
 224 #endif
 225     return custom_ext_meth_add(&ctx->cert->cli_ext, ext_type, add_cb,
 226                                free_cb, add_arg, parse_cb, parse_arg);
 227 }
 228
 229 int SSL_CTX_add_server_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
 230                                   custom_ext_add_cb add_cb,
 231                                   custom_ext_free_cb free_cb,
 232                                   void *add_arg,
 233                                   custom_ext_parse_cb parse_cb, void *parse_arg)
 234 {
 235     return custom_ext_meth_add(&ctx->cert->srv_ext, ext_type,
 236                                add_cb, free_cb, add_arg, parse_cb, parse_arg);
 237 }
 238
 239 int SSL_extension_supported(unsigned int ext_type)
 240 {
 241     switch (ext_type) {
 242         /* Internally supported extensions. */
 243     case TLSEXT_TYPE_application_layer_protocol_negotiation:
 244     case TLSEXT_TYPE_ec_point_formats:
 245     case TLSEXT_TYPE_supported_groups:
 246 #ifndef OPENSSL_NO_NEXTPROTONEG
 247     case TLSEXT_TYPE_next_proto_neg:
 248 #endif
 249     case TLSEXT_TYPE_padding:
 250     case TLSEXT_TYPE_renegotiate:
 251     case TLSEXT_TYPE_server_name:
 252     case TLSEXT_TYPE_session_ticket:
 253     case TLSEXT_TYPE_signature_algorithms:
 254     case TLSEXT_TYPE_srp:
 255     case TLSEXT_TYPE_status_request:
 256     case TLSEXT_TYPE_signed_certificate_timestamp:
 257     case TLSEXT_TYPE_use_srtp:
 258 #ifdef TLSEXT_TYPE_encrypt_then_mac
 259     case TLSEXT_TYPE_encrypt_then_mac:
 260 #endif
 261     case TLSEXT_TYPE_key_share:
 262     case TLSEXT_TYPE_supported_versions:
 263     case TLSEXT_TYPE_extended_master_secret:
 264         return 1;
 265     default:
 266         return 0;
 267     }
 268 }