/src/libressl/ssl/tls13_client.c

Source (jump to first uncovered line)
/* $OpenBSD: tls13_client.c,v 1.97 2022/07/24 14:16:29 jsing Exp $ */
/*
 * Copyright (c) 2018, 2019 Joel Sing <jsing@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <openssl/ssl3.h>

#include "bytestring.h"
#include "ssl_locl.h"
#include "ssl_sigalgs.h"
#include "ssl_tlsext.h"
#include "tls13_handshake.h"
#include "tls13_internal.h"

int
tls13_client_init(struct tls13_ctx *ctx)
{
  const uint16_t *groups;
  size_t groups_len;
  SSL *s = ctx->ssl;

  if (!ssl_supported_tls_version_range(s, &ctx->hs->our_min_tls_version,
      &ctx->hs->our_max_tls_version)) {
    SSLerror(s, SSL_R_NO_PROTOCOLS_AVAILABLE);
    return 0;
  }
  s->version = ctx->hs->our_max_tls_version;

  tls13_record_layer_set_retry_after_phh(ctx->rl,
      (s->internal->mode & SSL_MODE_AUTO_RETRY) != 0);

  if (!ssl_get_new_session(s, 0)) /* XXX */
    return 0;

  if (!tls1_transcript_init(s))
    return 0;

  /* Generate a key share using our preferred group. */
  tls1_get_group_list(s, 0, &groups, &groups_len);
  if (groups_len < 1)
    return 0;
  if ((ctx->hs->key_share = tls_key_share_new(groups[0])) == NULL)
    return 0;
  if (!tls_key_share_generate(ctx->hs->key_share))
    return 0;

  arc4random_buf(s->s3->client_random, SSL3_RANDOM_SIZE);

  /*
   * The legacy session identifier should either be set to an
   * unpredictable 32-byte value or zero length... a non-zero length
   * legacy session identifier triggers compatibility mode (see RFC 8446
   * Appendix D.4). In the pre-TLSv1.3 case a zero length value is used.
   */
  if (ctx->middlebox_compat &&
      ctx->hs->our_max_tls_version >= TLS1_3_VERSION) {
    arc4random_buf(ctx->hs->tls13.legacy_session_id,
        sizeof(ctx->hs->tls13.legacy_session_id));
    ctx->hs->tls13.legacy_session_id_len =
        sizeof(ctx->hs->tls13.legacy_session_id);
  }

  return 1;
}

int
tls13_client_connect(struct tls13_ctx *ctx)
{
  if (ctx->mode != TLS13_HS_CLIENT)
    return TLS13_IO_FAILURE;

  return tls13_handshake_perform(ctx);
}

static int
tls13_client_hello_build(struct tls13_ctx *ctx, CBB *cbb)
{
  CBB cipher_suites, compression_methods, session_id;
  uint16_t client_version;
  SSL *s = ctx->ssl;

  /* Legacy client version is capped at TLS 1.2. */
  if (!ssl_max_legacy_version(s, &client_version))
    goto err;

  if (!CBB_add_u16(cbb, client_version))
    goto err;
  if (!CBB_add_bytes(cbb, s->s3->client_random, SSL3_RANDOM_SIZE))
    goto err;

  if (!CBB_add_u8_length_prefixed(cbb, &session_id))
    goto err;
  if (!CBB_add_bytes(&session_id, ctx->hs->tls13.legacy_session_id,
      ctx->hs->tls13.legacy_session_id_len))
    goto err;

  if (!CBB_add_u16_length_prefixed(cbb, &cipher_suites))
    goto err;
  if (!ssl_cipher_list_to_bytes(s, SSL_get_ciphers(s), &cipher_suites)) {
    SSLerror(s, SSL_R_NO_CIPHERS_AVAILABLE);
    goto err;
  }

  if (!CBB_add_u8_length_prefixed(cbb, &compression_methods))
    goto err;
  if (!CBB_add_u8(&compression_methods, 0))
    goto err;

  if (!tlsext_client_build(s, SSL_TLSEXT_MSG_CH, cbb))
    goto err;

  if (!CBB_flush(cbb))
    goto err;

  return 1;

 err:
  return 0;
}

int
tls13_client_hello_send(struct tls13_ctx *ctx, CBB *cbb)
{
  if (ctx->hs->our_min_tls_version < TLS1_2_VERSION)
    tls13_record_layer_set_legacy_version(ctx->rl, TLS1_VERSION);

  /* We may receive a pre-TLSv1.3 alert in response to the client hello. */
  tls13_record_layer_allow_legacy_alerts(ctx->rl, 1);

  if (!tls13_client_hello_build(ctx, cbb))
    return 0;

  return 1;
}

int
tls13_client_hello_sent(struct tls13_ctx *ctx)
{
  tls13_record_layer_allow_ccs(ctx->rl, 1);

  tls1_transcript_freeze(ctx->ssl);

  if (ctx->middlebox_compat)
    ctx->send_dummy_ccs = 1;

  return 1;
}

static int
tls13_server_hello_is_legacy(CBS *cbs)
{
  CBS extensions_block, extensions, extension_data;
  uint16_t selected_version = 0;
  uint16_t type;

  CBS_dup(cbs, &extensions_block);

  if (!CBS_get_u16_length_prefixed(&extensions_block, &extensions))
    return 1;

  while (CBS_len(&extensions) > 0) {
    if (!CBS_get_u16(&extensions, &type))
      return 1;
    if (!CBS_get_u16_length_prefixed(&extensions, &extension_data))
      return 1;

    if (type != TLSEXT_TYPE_supported_versions)
      continue;
    if (!CBS_get_u16(&extension_data, &selected_version))
      return 1;
    if (CBS_len(&extension_data) != 0)
      return 1;
  }

  return (selected_version < TLS1_3_VERSION);
}

static int
tls13_server_hello_is_retry(CBS *cbs)
{
  CBS server_hello, server_random;
  uint16_t legacy_version;

  CBS_dup(cbs, &server_hello);

  if (!CBS_get_u16(&server_hello, &legacy_version))
    return 0;
  if (!CBS_get_bytes(&server_hello, &server_random, SSL3_RANDOM_SIZE))
    return 0;

  /* See if this is a HelloRetryRequest. */
  return CBS_mem_equal(&server_random, tls13_hello_retry_request_hash,
      sizeof(tls13_hello_retry_request_hash));
}

static int
tls13_server_hello_process(struct tls13_ctx *ctx, CBS *cbs)
{
  CBS server_random, session_id;
  uint16_t tlsext_msg_type = SSL_TLSEXT_MSG_SH;
  uint16_t cipher_suite, legacy_version;
  uint8_t compression_method;
  const SSL_CIPHER *cipher;
  int alert_desc;
  SSL *s = ctx->ssl;

  if (!CBS_get_u16(cbs, &legacy_version))
    goto err;
  if (!CBS_get_bytes(cbs, &server_random, SSL3_RANDOM_SIZE))
    goto err;
  if (!CBS_get_u8_length_prefixed(cbs, &session_id))
    goto err;
  if (!CBS_get_u16(cbs, &cipher_suite))
    goto err;
  if (!CBS_get_u8(cbs, &compression_method))
    goto err;

  if (tls13_server_hello_is_legacy(cbs)) {
    if (ctx->hs->our_max_tls_version >= TLS1_3_VERSION) {
      /*
       * RFC 8446 section 4.1.3: we must not downgrade if
       * the server random value contains the TLS 1.2 or 1.1
       * magical value.
       */
      if (!CBS_skip(&server_random, CBS_len(&server_random) -
          sizeof(tls13_downgrade_12)))
        goto err;
      if (CBS_mem_equal(&server_random, tls13_downgrade_12,
          sizeof(tls13_downgrade_12)) ||
          CBS_mem_equal(&server_random, tls13_downgrade_11,
          sizeof(tls13_downgrade_11))) {
        ctx->alert = TLS13_ALERT_ILLEGAL_PARAMETER;
        goto err;
      }
    }

    if (!CBS_skip(cbs, CBS_len(cbs)))
      goto err;

    ctx->hs->tls13.use_legacy = 1;
    return 1;
  }

  /* From here on in we know we are doing TLSv1.3. */
  tls13_record_layer_set_legacy_version(ctx->rl, TLS1_2_VERSION);
  tls13_record_layer_allow_legacy_alerts(ctx->rl, 0);

  /* See if this is a HelloRetryRequest. */
  /* XXX - see if we can avoid doing this twice. */
  if (CBS_mem_equal(&server_random, tls13_hello_retry_request_hash,
      sizeof(tls13_hello_retry_request_hash))) {
    tlsext_msg_type = SSL_TLSEXT_MSG_HRR;
    ctx->hs->tls13.hrr = 1;
  }

  if (!tlsext_client_parse(s, tlsext_msg_type, cbs, &alert_desc)) {
    ctx->alert = alert_desc;
    goto err;
  }

  /*
   * The supported versions extension indicated 0x0304 or greater.
   * Ensure that it was 0x0304 and that legacy version is set to 0x0303
   * (RFC 8446 section 4.2.1).
   */
  if (ctx->hs->tls13.server_version != TLS1_3_VERSION ||
      legacy_version != TLS1_2_VERSION) {
    ctx->alert = TLS13_ALERT_PROTOCOL_VERSION;
    goto err;
  }
  ctx->hs->negotiated_tls_version = ctx->hs->tls13.server_version;
  ctx->hs->peer_legacy_version = legacy_version;

  /* The session_id must match. */
  if (!CBS_mem_equal(&session_id, ctx->hs->tls13.legacy_session_id,
      ctx->hs->tls13.legacy_session_id_len)) {
    ctx->alert = TLS13_ALERT_ILLEGAL_PARAMETER;
    goto err;
  }

  /*
   * Ensure that the cipher suite is one that we offered in the client
   * hello and that it is a TLSv1.3 cipher suite.
   */
  cipher = ssl3_get_cipher_by_value(cipher_suite);
  if (cipher == NULL || !ssl_cipher_in_list(SSL_get_ciphers(s), cipher)) {
    ctx->alert = TLS13_ALERT_ILLEGAL_PARAMETER;
    goto err;
  }
  if (cipher->algorithm_ssl != SSL_TLSV1_3) {
    ctx->alert = TLS13_ALERT_ILLEGAL_PARAMETER;
    goto err;
  }
  if (!(ctx->handshake_stage.hs_type & WITHOUT_HRR) && !ctx->hs->tls13.hrr) {
    /*
     * A ServerHello following a HelloRetryRequest MUST use the same
     * cipher suite (RFC 8446 section 4.1.4).
     */
    if (ctx->hs->cipher != cipher) {
      ctx->alert = TLS13_ALERT_ILLEGAL_PARAMETER;
      goto err;
    }
  }
  ctx->hs->cipher = cipher;

  if (compression_method != 0) {
    ctx->alert = TLS13_ALERT_ILLEGAL_PARAMETER;
    goto err;
  }

  return 1;

 err:
  if (ctx->alert == 0)
    ctx->alert = TLS13_ALERT_DECODE_ERROR;

  return 0;
}

static int
tls13_client_engage_record_protection(struct tls13_ctx *ctx)
{
  struct tls13_secrets *secrets;
  struct tls13_secret context;
  unsigned char buf[EVP_MAX_MD_SIZE];
  uint8_t *shared_key = NULL;
  size_t shared_key_len = 0;
  size_t hash_len;
  SSL *s = ctx->ssl;
  int ret = 0;

  /* Derive the shared key and engage record protection. */

  if (!tls_key_share_derive(ctx->hs->key_share, &shared_key,
      &shared_key_len))
    goto err;

  s->session->cipher = ctx->hs->cipher;
  s->session->ssl_version = ctx->hs->tls13.server_version;

  if ((ctx->aead = tls13_cipher_aead(ctx->hs->cipher)) == NULL)
    goto err;
  if ((ctx->hash = tls13_cipher_hash(ctx->hs->cipher)) == NULL)
    goto err;

  if ((secrets = tls13_secrets_create(ctx->hash, 0)) == NULL)
    goto err;
  ctx->hs->tls13.secrets = secrets;

  /* XXX - pass in hash. */
  if (!tls1_transcript_hash_init(s))
    goto err;
  tls1_transcript_free(s);
  if (!tls1_transcript_hash_value(s, buf, sizeof(buf), &hash_len))
    goto err;
  context.data = buf;
  context.len = hash_len;

  /* Early secrets. */
  if (!tls13_derive_early_secrets(secrets, secrets->zeros.data,
      secrets->zeros.len, &context))
    goto err;

  /* Handshake secrets. */
  if (!tls13_derive_handshake_secrets(ctx->hs->tls13.secrets, shared_key,
      shared_key_len, &context))
    goto err;

  tls13_record_layer_set_aead(ctx->rl, ctx->aead);
  tls13_record_layer_set_hash(ctx->rl, ctx->hash);

  if (!tls13_record_layer_set_read_traffic_key(ctx->rl,
      &secrets->server_handshake_traffic, ssl_encryption_handshake))
    goto err;
  if (!tls13_record_layer_set_write_traffic_key(ctx->rl,
      &secrets->client_handshake_traffic, ssl_encryption_handshake))
    goto err;

  ret = 1;

 err:
  freezero(shared_key, shared_key_len);

  return ret;
}

int
tls13_server_hello_retry_request_recv(struct tls13_ctx *ctx, CBS *cbs)
{
  /*
   * The state machine has no way of knowing if we're going to receive a
   * HelloRetryRequest or a ServerHello. As such, we have to handle
   * this case here and hand off to the appropriate function.
   */
  if (!tls13_server_hello_is_retry(cbs)) {
    ctx->handshake_stage.hs_type |= WITHOUT_HRR;
    return tls13_server_hello_recv(ctx, cbs);
  }

  if (!tls13_server_hello_process(ctx, cbs))
    return 0;

  /*
   * This may have been a TLSv1.2 or earlier ServerHello that just
   * happened to have matching server random...
   */
  if (ctx->hs->tls13.use_legacy)
    return tls13_use_legacy_client(ctx);

  if (!ctx->hs->tls13.hrr)
    return 0;

  if (!tls13_synthetic_handshake_message(ctx))
    return 0;
  if (!tls13_handshake_msg_record(ctx))
    return 0;

  ctx->hs->tls13.hrr = 0;

  return 1;
}

int
tls13_client_hello_retry_send(struct tls13_ctx *ctx, CBB *cbb)
{
  /*
   * Ensure that the server supported group is one that we listed in our
   * supported groups and is not the same as the key share we previously
   * offered.
   */
  if (!tls1_check_group(ctx->ssl, ctx->hs->tls13.server_group))
    return 0; /* XXX alert */
  if (ctx->hs->tls13.server_group == tls_key_share_group(ctx->hs->key_share))
    return 0; /* XXX alert */

  /* Switch to new key share. */
  tls_key_share_free(ctx->hs->key_share);
  if ((ctx->hs->key_share =
      tls_key_share_new(ctx->hs->tls13.server_group)) == NULL)
    return 0;
  if (!tls_key_share_generate(ctx->hs->key_share))
    return 0;

  if (!tls13_client_hello_build(ctx, cbb))
    return 0;

  return 1;
}

int
tls13_server_hello_recv(struct tls13_ctx *ctx, CBS *cbs)
{
  SSL *s = ctx->ssl;

  /*
   * We may have received a legacy (pre-TLSv1.3) ServerHello or a TLSv1.3
   * ServerHello. HelloRetryRequests have already been handled.
   */
  if (!tls13_server_hello_process(ctx, cbs))
    return 0;

  if (ctx->handshake_stage.hs_type & WITHOUT_HRR) {
    tls1_transcript_unfreeze(s);
    if (!tls13_handshake_msg_record(ctx))
      return 0;
  }

  if (ctx->hs->tls13.use_legacy) {
    if (!(ctx->handshake_stage.hs_type & WITHOUT_HRR))
      return 0;
    return tls13_use_legacy_client(ctx);
  }

  if (ctx->hs->tls13.hrr) {
    /* The server has sent two HelloRetryRequests. */
    ctx->alert = TLS13_ALERT_ILLEGAL_PARAMETER;
    return 0;
  }

  if (!tls13_client_engage_record_protection(ctx))
    return 0;

  ctx->handshake_stage.hs_type |= NEGOTIATED;

  return 1;
}

int
tls13_server_encrypted_extensions_recv(struct tls13_ctx *ctx, CBS *cbs)
{
  int alert_desc;

  if (!tlsext_client_parse(ctx->ssl, SSL_TLSEXT_MSG_EE, cbs, &alert_desc)) {
    ctx->alert = alert_desc;
    return 0;
  }

  return 1;
}

int
tls13_server_certificate_request_recv(struct tls13_ctx *ctx, CBS *cbs)
{
  CBS cert_request_context;
  int alert_desc;

  /*
   * Thanks to poor state design in the RFC, this function can be called
   * when we actually have a certificate message instead of a certificate
   * request... in that case we call the certificate handler after
   * switching state, to avoid advancing state.
   */
  if (tls13_handshake_msg_type(ctx->hs_msg) == TLS13_MT_CERTIFICATE) {
    ctx->handshake_stage.hs_type |= WITHOUT_CR;
    return tls13_server_certificate_recv(ctx, cbs);
  }

  if (!CBS_get_u8_length_prefixed(cbs, &cert_request_context))
    goto err;
  if (CBS_len(&cert_request_context) != 0)
    goto err;

  if (!tlsext_client_parse(ctx->ssl, SSL_TLSEXT_MSG_CR, cbs, &alert_desc)) {
    ctx->alert = alert_desc;
    goto err;
  }

  return 1;

 err:
  if (ctx->alert == 0)
    ctx->alert = TLS13_ALERT_DECODE_ERROR;

  return 0;
}

int
tls13_server_certificate_recv(struct tls13_ctx *ctx, CBS *cbs)
{
  CBS cert_request_context, cert_list, cert_data;
  struct stack_st_X509 *certs = NULL;
  SSL *s = ctx->ssl;
  X509 *cert = NULL;
  EVP_PKEY *pkey;
  const uint8_t *p;
  int alert_desc, cert_type;
  int ret = 0;

  if ((certs = sk_X509_new_null()) == NULL)
    goto err;

  if (!CBS_get_u8_length_prefixed(cbs, &cert_request_context))
    goto err;
  if (CBS_len(&cert_request_context) != 0)
    goto err;
  if (!CBS_get_u24_length_prefixed(cbs, &cert_list))
    goto err;

  while (CBS_len(&cert_list) > 0) {
    if (!CBS_get_u24_length_prefixed(&cert_list, &cert_data))
      goto err;

    if (!tlsext_client_parse(ctx->ssl, SSL_TLSEXT_MSG_CT,
        &cert_list, &alert_desc)) {
      ctx->alert = alert_desc;
      goto err;
    }

    p = CBS_data(&cert_data);
    if ((cert = d2i_X509(NULL, &p, CBS_len(&cert_data))) == NULL)
      goto err;
    if (p != CBS_data(&cert_data) + CBS_len(&cert_data))
      goto err;

    if (!sk_X509_push(certs, cert))
      goto err;

    cert = NULL;
  }

  /* A server must always provide a non-empty certificate list. */
  if (sk_X509_num(certs) < 1) {
    ctx->alert = TLS13_ALERT_DECODE_ERROR;
    tls13_set_errorx(ctx, TLS13_ERR_NO_PEER_CERTIFICATE, 0,
        "peer failed to provide a certificate", NULL);
    goto err;
  }

  /*
   * At this stage we still have no proof of possession. As such, it would
   * be preferable to keep the chain and verify once we have successfully
   * processed the CertificateVerify message.
   */
  if (ssl_verify_cert_chain(s, certs) <= 0 &&
      s->verify_mode != SSL_VERIFY_NONE) {
    ctx->alert = ssl_verify_alarm_type(s->verify_result);
    tls13_set_errorx(ctx, TLS13_ERR_VERIFY_FAILED, 0,
        "failed to verify peer certificate", NULL);
    goto err;
  }
  ERR_clear_error();

  cert = sk_X509_value(certs, 0);
  X509_up_ref(cert);

  if ((pkey = X509_get0_pubkey(cert)) == NULL)
    goto err;
  if (EVP_PKEY_missing_parameters(pkey))
    goto err;
  if ((cert_type = ssl_cert_type(pkey)) < 0)
    goto err;

  X509_up_ref(cert);
  X509_free(s->session->peer_cert);
  s->session->peer_cert = cert;
  s->session->peer_cert_type = cert_type;

  s->session->verify_result = s->verify_result;

  sk_X509_pop_free(s->session->cert_chain, X509_free);
  s->session->cert_chain = certs;
  certs = NULL;

  if (ctx->ocsp_status_recv_cb != NULL &&
      !ctx->ocsp_status_recv_cb(ctx))
    goto err;

  ret = 1;

 err:
  sk_X509_pop_free(certs, X509_free);
  X509_free(cert);

  return ret;
}

int
tls13_server_certificate_verify_recv(struct tls13_ctx *ctx, CBS *cbs)
{
  const struct ssl_sigalg *sigalg;
  uint16_t signature_scheme;
  uint8_t *sig_content = NULL;
  size_t sig_content_len;
  EVP_MD_CTX *mdctx = NULL;
  EVP_PKEY_CTX *pctx;
  EVP_PKEY *pkey;
  X509 *cert;
  CBS signature;
  CBB cbb;
  int ret = 0;

  memset(&cbb, 0, sizeof(cbb));

  if (!CBS_get_u16(cbs, &signature_scheme))
    goto err;
  if (!CBS_get_u16_length_prefixed(cbs, &signature))
    goto err;

  if (!CBB_init(&cbb, 0))
    goto err;
  if (!CBB_add_bytes(&cbb, tls13_cert_verify_pad,
      sizeof(tls13_cert_verify_pad)))
    goto err;
  if (!CBB_add_bytes(&cbb, tls13_cert_server_verify_context,
      strlen(tls13_cert_server_verify_context)))
    goto err;
  if (!CBB_add_u8(&cbb, 0))
    goto err;
  if (!CBB_add_bytes(&cbb, ctx->hs->tls13.transcript_hash,
      ctx->hs->tls13.transcript_hash_len))
    goto err;
  if (!CBB_finish(&cbb, &sig_content, &sig_content_len))
    goto err;

  if ((cert = ctx->ssl->session->peer_cert) == NULL)
    goto err;
  if ((pkey = X509_get0_pubkey(cert)) == NULL)
    goto err;
  if ((sigalg = ssl_sigalg_for_peer(ctx->ssl, pkey,
      signature_scheme)) == NULL)
    goto err;
  ctx->hs->peer_sigalg = sigalg;

  if (CBS_len(&signature) > EVP_PKEY_size(pkey))
    goto err;

  if ((mdctx = EVP_MD_CTX_new()) == NULL)
    goto err;
  if (!EVP_DigestVerifyInit(mdctx, &pctx, sigalg->md(), NULL, pkey))
    goto err;
  if (sigalg->flags & SIGALG_FLAG_RSA_PSS) {
    if (!EVP_PKEY_CTX_set_rsa_padding(pctx, RSA_PKCS1_PSS_PADDING))
      goto err;
    if (!EVP_PKEY_CTX_set_rsa_pss_saltlen(pctx, -1))
      goto err;
  }
  if (!EVP_DigestVerifyUpdate(mdctx, sig_content, sig_content_len)) {
    ctx->alert = TLS13_ALERT_DECRYPT_ERROR;
    goto err;
  }
  if (EVP_DigestVerifyFinal(mdctx, CBS_data(&signature),
      CBS_len(&signature)) <= 0) {
    ctx->alert = TLS13_ALERT_DECRYPT_ERROR;
    goto err;
  }

  ret = 1;

 err:
  if (!ret && ctx->alert == 0)
    ctx->alert = TLS13_ALERT_DECODE_ERROR;
  CBB_cleanup(&cbb);
  EVP_MD_CTX_free(mdctx);
  free(sig_content);

  return ret;
}

int
tls13_server_finished_recv(struct tls13_ctx *ctx, CBS *cbs)
{
  struct tls13_secrets *secrets = ctx->hs->tls13.secrets;
  struct tls13_secret context = { .data = "", .len = 0 };
  struct tls13_secret finished_key;
  uint8_t transcript_hash[EVP_MAX_MD_SIZE];
  size_t transcript_hash_len;
  uint8_t *verify_data = NULL;
  size_t verify_data_len;
  uint8_t key[EVP_MAX_MD_SIZE];
  HMAC_CTX *hmac_ctx = NULL;
  unsigned int hlen;
  int ret = 0;

  /*
   * Verify server finished.
   */
  finished_key.data = key;
  finished_key.len = EVP_MD_size(ctx->hash);

  if (!tls13_hkdf_expand_label(&finished_key, ctx->hash,
      &secrets->server_handshake_traffic, "finished",
      &context))
    goto err;

  if ((hmac_ctx = HMAC_CTX_new()) == NULL)
    goto err;
  if (!HMAC_Init_ex(hmac_ctx, finished_key.data, finished_key.len,
      ctx->hash, NULL))
    goto err;
  if (!HMAC_Update(hmac_ctx, ctx->hs->tls13.transcript_hash,
      ctx->hs->tls13.transcript_hash_len))
    goto err;
  verify_data_len = HMAC_size(hmac_ctx);
  if ((verify_data = calloc(1, verify_data_len)) == NULL)
    goto err;
  if (!HMAC_Final(hmac_ctx, verify_data, &hlen))
    goto err;
  if (hlen != verify_data_len)
    goto err;

  if (!CBS_mem_equal(cbs, verify_data, verify_data_len)) {
    ctx->alert = TLS13_ALERT_DECRYPT_ERROR;
    goto err;
  }

  if (!CBS_write_bytes(cbs, ctx->hs->peer_finished,
      sizeof(ctx->hs->peer_finished),
      &ctx->hs->peer_finished_len))
    goto err;

  if (!CBS_skip(cbs, verify_data_len))
    goto err;

  /*
   * Derive application traffic keys.
   */
  if (!tls1_transcript_hash_value(ctx->ssl, transcript_hash,
      sizeof(transcript_hash), &transcript_hash_len))
    goto err;

  context.data = transcript_hash;
  context.len = transcript_hash_len;

  if (!tls13_derive_application_secrets(secrets, &context))
    goto err;

  /*
   * Any records following the server finished message must be encrypted
   * using the server application traffic keys.
   */
  if (!tls13_record_layer_set_read_traffic_key(ctx->rl,
      &secrets->server_application_traffic, ssl_encryption_application))
    goto err;

  tls13_record_layer_allow_ccs(ctx->rl, 0);

  ret = 1;

 err:
  HMAC_CTX_free(hmac_ctx);
  free(verify_data);

  return ret;
}

static int
tls13_client_check_certificate(struct tls13_ctx *ctx, SSL_CERT_PKEY *cpk,
    int *ok, const struct ssl_sigalg **out_sigalg)
{
  const struct ssl_sigalg *sigalg;
  SSL *s = ctx->ssl;

  *ok = 0;
  *out_sigalg = NULL;

  if (cpk->x509 == NULL || cpk->privatekey == NULL)
    goto done;

  if ((sigalg = ssl_sigalg_select(s, cpk->privatekey)) == NULL)
    goto done;

  *ok = 1;
  *out_sigalg = sigalg;

 done:
  return 1;
}

static int
tls13_client_select_certificate(struct tls13_ctx *ctx, SSL_CERT_PKEY **out_cpk,
    const struct ssl_sigalg **out_sigalg)
{
  SSL *s = ctx->ssl;
  const struct ssl_sigalg *sigalg;
  SSL_CERT_PKEY *cpk;
  int cert_ok;

  *out_cpk = NULL;
  *out_sigalg = NULL;

  /*
   * XXX - RFC 8446, 4.4.2.3: the server can communicate preferences
   * with the certificate_authorities (4.2.4) and oid_filters (4.2.5)
   * extensions. We should honor the former and must apply the latter.
   */

  cpk = &s->cert->pkeys[SSL_PKEY_ECC];
  if (!tls13_client_check_certificate(ctx, cpk, &cert_ok, &sigalg))
    return 0;
  if (cert_ok)
    goto done;

  cpk = &s->cert->pkeys[SSL_PKEY_RSA];
  if (!tls13_client_check_certificate(ctx, cpk, &cert_ok, &sigalg))
    return 0;
  if (cert_ok)
    goto done;

  cpk = NULL;
  sigalg = NULL;

 done:
  *out_cpk = cpk;
  *out_sigalg = sigalg;

  return 1;
}

int
tls13_client_certificate_send(struct tls13_ctx *ctx, CBB *cbb)
{
  SSL *s = ctx->ssl;
  CBB cert_request_context, cert_list;
  const struct ssl_sigalg *sigalg;
  STACK_OF(X509) *chain;
  SSL_CERT_PKEY *cpk;
  X509 *cert;
  int i, ret = 0;

  if (!tls13_client_select_certificate(ctx, &cpk, &sigalg))
    goto err;

  ctx->hs->tls13.cpk = cpk;
  ctx->hs->our_sigalg = sigalg;

  if (!CBB_add_u8_length_prefixed(cbb, &cert_request_context))
    goto err;
  if (!CBB_add_u24_length_prefixed(cbb, &cert_list))
    goto err;

  /* No certificate selected. */
  if (cpk == NULL)
    goto done;

  if ((chain = cpk->chain) == NULL)
         chain = s->ctx->extra_certs;

  if (!tls13_cert_add(ctx, &cert_list, cpk->x509, tlsext_client_build))
    goto err;

  for (i = 0; i < sk_X509_num(chain); i++) {
    cert = sk_X509_value(chain, i);
    if (!tls13_cert_add(ctx, &cert_list, cert, tlsext_client_build))
      goto err;
  }

  ctx->handshake_stage.hs_type |= WITH_CCV;
 done:
  if (!CBB_flush(cbb))
    goto err;

  ret = 1;

 err:
  return ret;
}

int
tls13_client_certificate_verify_send(struct tls13_ctx *ctx, CBB *cbb)
{
  const struct ssl_sigalg *sigalg;
  uint8_t *sig = NULL, *sig_content = NULL;
  size_t sig_len, sig_content_len;
  EVP_MD_CTX *mdctx = NULL;
  EVP_PKEY_CTX *pctx;
  EVP_PKEY *pkey;
  const SSL_CERT_PKEY *cpk;
  CBB sig_cbb;
  int ret = 0;

  memset(&sig_cbb, 0, sizeof(sig_cbb));

  if ((cpk = ctx->hs->tls13.cpk) == NULL)
    goto err;
  if ((sigalg = ctx->hs->our_sigalg) == NULL)
    goto err;
  pkey = cpk->privatekey;

  if (!CBB_init(&sig_cbb, 0))
    goto err;
  if (!CBB_add_bytes(&sig_cbb, tls13_cert_verify_pad,
      sizeof(tls13_cert_verify_pad)))
    goto err;
  if (!CBB_add_bytes(&sig_cbb, tls13_cert_client_verify_context,
      strlen(tls13_cert_client_verify_context)))
    goto err;
  if (!CBB_add_u8(&sig_cbb, 0))
    goto err;
  if (!CBB_add_bytes(&sig_cbb, ctx->hs->tls13.transcript_hash,
      ctx->hs->tls13.transcript_hash_len))
    goto err;
  if (!CBB_finish(&sig_cbb, &sig_content, &sig_content_len))
    goto err;

  if ((mdctx = EVP_MD_CTX_new()) == NULL)
    goto err;
  if (!EVP_DigestSignInit(mdctx, &pctx, sigalg->md(), NULL, pkey))
    goto err;
  if (sigalg->flags & SIGALG_FLAG_RSA_PSS) {
    if (!EVP_PKEY_CTX_set_rsa_padding(pctx, RSA_PKCS1_PSS_PADDING))
      goto err;
    if (!EVP_PKEY_CTX_set_rsa_pss_saltlen(pctx, -1))
      goto err;
  }
  if (!EVP_DigestSignUpdate(mdctx, sig_content, sig_content_len))
    goto err;
  if (EVP_DigestSignFinal(mdctx, NULL, &sig_len) <= 0)
    goto err;
  if ((sig = calloc(1, sig_len)) == NULL)
    goto err;
  if (EVP_DigestSignFinal(mdctx, sig, &sig_len) <= 0)
    goto err;

  if (!CBB_add_u16(cbb, sigalg->value))
    goto err;
  if (!CBB_add_u16_length_prefixed(cbb, &sig_cbb))
    goto err;
  if (!CBB_add_bytes(&sig_cbb, sig, sig_len))
    goto err;

  if (!CBB_flush(cbb))
    goto err;

  ret = 1;

 err:
  if (!ret && ctx->alert == 0)
    ctx->alert = TLS13_ALERT_INTERNAL_ERROR;

  CBB_cleanup(&sig_cbb);
  EVP_MD_CTX_free(mdctx);
  free(sig_content);
  free(sig);

  return ret;
}

int
tls13_client_end_of_early_data_send(struct tls13_ctx *ctx, CBB *cbb)
{
  return 0;
}

int
tls13_client_finished_send(struct tls13_ctx *ctx, CBB *cbb)
{
  struct tls13_secrets *secrets = ctx->hs->tls13.secrets;
  struct tls13_secret context = { .data = "", .len = 0 };
  struct tls13_secret finished_key = { .data = NULL, .len = 0 };
  uint8_t transcript_hash[EVP_MAX_MD_SIZE];
  size_t transcript_hash_len;
  uint8_t *verify_data;
  size_t verify_data_len;
  unsigned int hlen;
  HMAC_CTX *hmac_ctx = NULL;
  CBS cbs;
  int ret = 0;

  if (!tls13_secret_init(&finished_key, EVP_MD_size(ctx->hash)))
    goto err;

  if (!tls13_hkdf_expand_label(&finished_key, ctx->hash,
      &secrets->client_handshake_traffic, "finished",
      &context))
    goto err;

  if (!tls1_transcript_hash_value(ctx->ssl, transcript_hash,
      sizeof(transcript_hash), &transcript_hash_len))
    goto err;

  if ((hmac_ctx = HMAC_CTX_new()) == NULL)
    goto err;
  if (!HMAC_Init_ex(hmac_ctx, finished_key.data, finished_key.len,
      ctx->hash, NULL))
    goto err;
  if (!HMAC_Update(hmac_ctx, transcript_hash, transcript_hash_len))
    goto err;

  verify_data_len = HMAC_size(hmac_ctx);
  if (!CBB_add_space(cbb, &verify_data, verify_data_len))
    goto err;
  if (!HMAC_Final(hmac_ctx, verify_data, &hlen))
    goto err;
  if (hlen != verify_data_len)
    goto err;

  CBS_init(&cbs, verify_data, verify_data_len);
  if (!CBS_write_bytes(&cbs, ctx->hs->finished,
      sizeof(ctx->hs->finished), &ctx->hs->finished_len))
    goto err;

  ret = 1;

 err:
  tls13_secret_cleanup(&finished_key);
  HMAC_CTX_free(hmac_ctx);

  return ret;
}

int
tls13_client_finished_sent(struct tls13_ctx *ctx)
{
  struct tls13_secrets *secrets = ctx->hs->tls13.secrets;

  /*
   * Any records following the client finished message must be encrypted
   * using the client application traffic keys.
   */
  return tls13_record_layer_set_write_traffic_key(ctx->rl,
      &secrets->client_application_traffic, ssl_encryption_application);
}

Coverage Report

Created: 2022-08-24 06:31