text: /*
   * Copyright 2016 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
   * in the file LICENSE in the source distribution or at
   * https://www.openssl.org/source/license.html
   */
  
  #include <stdlib.h>
  #include "ssl_locl.h"
  #include <openssl/evp.h>
  #include <openssl/kdf.h>
  
  #define TLS13_MAX_LABEL_LEN     246
  
  /* Always filled with zeros */
  static const unsigned char default_zeros[EVP_MAX_MD_SIZE];
  
  /*
   * Given a |secret|; a |label| of length |labellen|; and |data| of length
   * |datalen| (e.g. typically a hash of the handshake messages), derive a new
   * secret |outlen| bytes long and store it in the location pointed to be |out|.
   * The |data| value may be zero length. Returns 1 on success  0 on failure.
   */
  int tls13_hkdf_expand(SSL *s, const EVP_MD *md, const unsigned char *secret,
                               const unsigned char *label, size_t labellen,
                               const unsigned char *data, size_t datalen,
                               unsigned char *out, size_t outlen)
  {
      const unsigned char label_prefix[] = "tls13 ";
      EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
      int ret;
      size_t hkdflabellen;
      size_t hashlen;
      /*
       * 2 bytes for length of whole HkdfLabel + 1 byte for length of combined
       * prefix and label + bytes for the label itself + bytes for the hash
       */
      unsigned char hkdflabel[sizeof(uint16_t) + sizeof(uint8_t) +
                              + sizeof(label_prefix) + TLS13_MAX_LABEL_LEN
                              + EVP_MAX_MD_SIZE];
      WPACKET pkt;
  
      if (pctx == NULL)
          return 0;
  
      hashlen = EVP_MD_size(md);
  
      if (!WPACKET_init_static_len(&pkt, hkdflabel, sizeof(hkdflabel), 0)
              || !WPACKET_put_bytes_u16(&pkt, outlen)
              || !WPACKET_start_sub_packet_u8(&pkt)
              || !WPACKET_memcpy(&pkt, label_prefix, sizeof(label_prefix) - 1)
              || !WPACKET_memcpy(&pkt, label, labellen)
              || !WPACKET_close(&pkt)
              || !WPACKET_sub_memcpy_u8(&pkt, data, (data == NULL) ? 0 : datalen)
              || !WPACKET_get_total_written(&pkt, &hkdflabellen)
              || !WPACKET_finish(&pkt)) {
          EVP_PKEY_CTX_free(pctx);
          WPACKET_cleanup(&pkt);
          return 0;
      }
  
      ret = EVP_PKEY_derive_init(pctx) <= 0
              || EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXPAND_ONLY)
                 <= 0
              || EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0
              || EVP_PKEY_CTX_set1_hkdf_key(pctx, secret, hashlen) <= 0
              || EVP_PKEY_CTX_add1_hkdf_info(pctx, hkdflabel, hkdflabellen) <= 0
              || EVP_PKEY_derive(pctx, out, &outlen) <= 0;
  
      EVP_PKEY_CTX_free(pctx);
  
      return ret == 0;
  }
  
  /*
   * Given a |secret| generate a |key| of length |keylen| bytes. Returns 1 on
   * success  0 on failure.
   */
  int tls13_derive_key(SSL *s, const EVP_MD *md, const unsigned char *secret,
                       unsigned char *key, size_t keylen)
  {
      static const unsigned char keylabel[] = "key";
  
      return tls13_hkdf_expand(s, md, secret, keylabel, sizeof(keylabel) - 1,
                               NULL, 0, key, keylen);
  }
  
  /*
   * Given a |secret| generate an |iv| of length |ivlen| bytes. Returns 1 on
   * success  0 on failure.
   */
  int tls13_derive_iv(SSL *s, const EVP_MD *md, const unsigned char *secret,
                      unsigned char *iv, size_t ivlen)
  {
      static const unsigned char ivlabel[] = "iv";
  
      return tls13_hkdf_expand(s, md, secret, ivlabel, sizeof(ivlabel) - 1,
                               NULL, 0, iv, ivlen);
  }
  
  int tls13_derive_finishedkey(SSL *s, const EVP_MD *md,
                               const unsigned char *secret,
                               unsigned char *fin, size_t finlen)
  {
      static const unsigned char finishedlabel[] = "finished";
  
      return tls13_hkdf_expand(s, md, secret, finishedlabel,
                               sizeof(finishedlabel) - 1, NULL, 0, fin, finlen);
  }
  
  /*
   * Given the previous secret |prevsecret| and a new input secret |insecret| of
   * length |insecretlen|, generate a new secret and store it in the location
   * pointed to by |outsecret|. Returns 1 on success  0 on failure.
   */
  int tls13_generate_secret(SSL *s, const EVP_MD *md,
                            const unsigned char *prevsecret,
                            const unsigned char *insecret,
                            size_t insecretlen,
                            unsigned char *outsecret)
  {
      size_t mdlen, prevsecretlen;
      int ret;
      EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
      static const char derived_secret_label[] = "derived";
      unsigned char preextractsec[EVP_MAX_MD_SIZE];
  
      if (pctx == NULL)
          return 0;
  
      mdlen = EVP_MD_size(md);
  
      if (insecret == NULL) {
          insecret = default_zeros;
          insecretlen = mdlen;
      }
      if (prevsecret == NULL) {
          prevsecret = default_zeros;
          prevsecretlen = 0;
      } else {
          EVP_MD_CTX *mctx = EVP_MD_CTX_new();
          unsigned char hash[EVP_MAX_MD_SIZE];
  
          /* The pre-extract derive step uses a hash of no messages */
          if (mctx == NULL
                  || EVP_DigestInit_ex(mctx, md, NULL) <= 0
                  || EVP_DigestFinal_ex(mctx, hash, NULL) <= 0) {
              EVP_MD_CTX_free(mctx);
              EVP_PKEY_CTX_free(pctx);
              return 0;
          }
          EVP_MD_CTX_free(mctx);
  
          /* Generate the pre-extract secret */
          if (!tls13_hkdf_expand(s, md, prevsecret,
                                 (unsigned char *)derived_secret_label,
                                 sizeof(derived_secret_label) - 1, hash, mdlen,
                                 preextractsec, mdlen)) {
              EVP_PKEY_CTX_free(pctx);
              return 0;
          }
  
          prevsecret = preextractsec;
          prevsecretlen = mdlen;
      }
  
      ret = EVP_PKEY_derive_init(pctx) <= 0
              || EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY)
                 <= 0
              || EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0
              || EVP_PKEY_CTX_set1_hkdf_key(pctx, insecret, insecretlen) <= 0
              || EVP_PKEY_CTX_set1_hkdf_salt(pctx, prevsecret, prevsecretlen)
                 <= 0
              || EVP_PKEY_derive(pctx, outsecret, &mdlen)
                 <= 0;
  
      EVP_PKEY_CTX_free(pctx);
      if (prevsecret == preextractsec)
          OPENSSL_cleanse(preextractsec, mdlen);
      return ret == 0;
  }
  
  /*
   * Given an input secret |insecret| of length |insecretlen| generate the
   * handshake secret. This requires the early secret to already have been
   * generated. Returns 1 on success  0 on failure.
   */
  int tls13_generate_handshake_secret(SSL *s, const unsigned char *insecret,
                                  size_t insecretlen)
  {
      return tls13_generate_secret(s, ssl_handshake_md(s), s->early_secret,
                                   insecret, insecretlen,
                                   (unsigned char *)&s->handshake_secret);
  }
  
  /*
   * Given the handshake secret |prev| of length |prevlen| generate the master
   * secret and store its length in |*secret_size|. Returns 1 on success  0 on
   * failure.
   */
  int tls13_generate_master_secret(SSL *s, unsigned char *out,
                                   unsigned char *prev, size_t prevlen,
                                   size_t *secret_size)
  {
      const EVP_MD *md = ssl_handshake_md(s);
  
      *secret_size = EVP_MD_size(md);
      return tls13_generate_secret(s, md, prev, NULL, 0, out);
  }
  
  /*
   * Generates the mac for the Finished message. Returns the length of the MAC or
   * 0 on error.
   */
  size_t tls13_final_finish_mac(SSL *s, const char *str, size_t slen,
                               unsigned char *out)
  {
      const EVP_MD *md = ssl_handshake_md(s);
      unsigned char hash[EVP_MAX_MD_SIZE];
      size_t hashlen, ret = 0;
      EVP_PKEY *key = NULL;
      EVP_MD_CTX *ctx = EVP_MD_CTX_new();
  
      if (!ssl_handshake_hash(s, hash, sizeof(hash), &hashlen))
          goto err;
  
      if (str == s->method->ssl3_enc->server_finished_label)
          key = EVP_PKEY_new_mac_key(EVP_PKEY_HMAC, NULL,
                                     s->server_finished_secret, hashlen);
      else
          key = EVP_PKEY_new_mac_key(EVP_PKEY_HMAC, NULL,
                                     s->client_finished_secret, hashlen);
  
      if (key == NULL
              || ctx == NULL
              || EVP_DigestSignInit(ctx, NULL, md, NULL, key) <= 0
              || EVP_DigestSignUpdate(ctx, hash, hashlen) <= 0
              || EVP_DigestSignFinal(ctx, out, &hashlen) <= 0)
          goto err;
  
      ret = hashlen;
   err:
      EVP_PKEY_free(key);
      EVP_MD_CTX_free(ctx);
      return ret;
  }
  
  /*
   * There isn't really a key block in TLSv1.3, but we still need this function
   * for initialising the cipher and hash. Returns 1 on success or 0 on failure.
   */
  int tls13_setup_key_block(SSL *s)
  {
      const EVP_CIPHER *c;
      const EVP_MD *hash;
      int mac_type = NID_undef;
  
      s->session->cipher = s->s3->tmp.new_cipher;
      if (!ssl_cipher_get_evp
          (s->session, &c, &hash, &mac_type, NULL, NULL, 0)) {
          SSLerr(SSL_F_TLS13_SETUP_KEY_BLOCK, SSL_R_CIPHER_OR_HASH_UNAVAILABLE);
          return 0;
      }
  
      s->s3->tmp.new_sym_enc = c;
      s->s3->tmp.new_hash = hash;
  
      return 1;
  }
  
  static int derive_secret_key_and_iv(SSL *s, int sending, const EVP_MD *md,
                                      const EVP_CIPHER *ciph,
                                      const unsigned char *insecret,
                                      const unsigned char *hash,
                                      const unsigned char *label,
                                      size_t labellen, unsigned char *secret,
                                      unsigned char *iv, EVP_CIPHER_CTX *ciph_ctx)
  {
      unsigned char key[EVP_MAX_KEY_LENGTH];
      size_t ivlen, keylen, taglen;
      size_t hashlen = EVP_MD_size(md);
  
      if (!tls13_hkdf_expand(s, md, insecret, label, labellen, hash, hashlen,
                             secret, hashlen)) {
          SSLerr(SSL_F_DERIVE_SECRET_KEY_AND_IV, ERR_R_INTERNAL_ERROR);
          goto err;
      }
  
      /* TODO(size_t): convert me */
      keylen = EVP_CIPHER_key_length(ciph);
      if (EVP_CIPHER_mode(ciph) == EVP_CIPH_CCM_MODE) {
          uint32_t algenc;
  
          ivlen = EVP_CCM_TLS_IV_LEN;
          if (s->s3->tmp.new_cipher == NULL) {
              /* We've not selected a cipher yet - we must be doing early data */
              algenc = s->session->cipher->algorithm_enc;
          } else {
              algenc = s->s3->tmp.new_cipher->algorithm_enc;
          }
          if (algenc & (SSL_AES128CCM8 | SSL_AES256CCM8))
              taglen = EVP_CCM8_TLS_TAG_LEN;
           else
              taglen = EVP_CCM_TLS_TAG_LEN;
      } else {
          ivlen = EVP_CIPHER_iv_length(ciph);
          taglen = 0;
      }
  
      if (!tls13_derive_key(s, md, secret, key, keylen)
              || !tls13_derive_iv(s, md, secret, iv, ivlen)) {
          SSLerr(SSL_F_DERIVE_SECRET_KEY_AND_IV, ERR_R_INTERNAL_ERROR);
          goto err;
      }
  
      if (EVP_CipherInit_ex(ciph_ctx, ciph, NULL, NULL, NULL, sending) <= 0
          || !EVP_CIPHER_CTX_ctrl(ciph_ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
          || (taglen != 0 && !EVP_CIPHER_CTX_ctrl(ciph_ctx, EVP_CTRL_AEAD_SET_TAG,
                                                  taglen, NULL))
          || EVP_CipherInit_ex(ciph_ctx, NULL, NULL, key, NULL, -1) <= 0) {
          SSLerr(SSL_F_DERIVE_SECRET_KEY_AND_IV, ERR_R_EVP_LIB);
          goto err;
      }
  
      return 1;
   err:
      OPENSSL_cleanse(key, sizeof(key));
      return 0;
  }
  
  int tls13_change_cipher_state(SSL *s, int which)
  {
      static const unsigned char client_early_traffic[] = "c e traffic";
      static const unsigned char client_handshake_traffic[] = "c hs traffic";
      static const unsigned char client_application_traffic[] = "c ap traffic";
      static const unsigned char server_handshake_traffic[] = "s hs traffic";
      static const unsigned char server_application_traffic[] = "s ap traffic";
      static const unsigned char exporter_master_secret[] = "exp master";
      static const unsigned char resumption_master_secret[] = "res master";
      unsigned char *iv;
      unsigned char secret[EVP_MAX_MD_SIZE];
      unsigned char hashval[EVP_MAX_MD_SIZE];
      unsigned char *hash = hashval;
      unsigned char *insecret;
      unsigned char *finsecret = NULL;
      const char *log_label = NULL;
      EVP_CIPHER_CTX *ciph_ctx;
      size_t finsecretlen = 0;
      const unsigned char *label;
      size_t labellen, hashlen = 0;
      int ret = 0;
      const EVP_MD *md = NULL;
      const EVP_CIPHER *cipher = NULL;
  
      if (which & SSL3_CC_READ) {
          if (s->enc_read_ctx != NULL) {
              EVP_CIPHER_CTX_reset(s->enc_read_ctx);
          } else {
              s->enc_read_ctx = EVP_CIPHER_CTX_new();
              if (s->enc_read_ctx == NULL) {
                  SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_MALLOC_FAILURE);
                  goto err;
              }
          }
          ciph_ctx = s->enc_read_ctx;
          iv = s->read_iv;
  
          RECORD_LAYER_reset_read_sequence(&s->rlayer);
      } else {
          if (s->enc_write_ctx != NULL) {
              EVP_CIPHER_CTX_reset(s->enc_write_ctx);
          } else {
              s->enc_write_ctx = EVP_CIPHER_CTX_new();
              if (s->enc_write_ctx == NULL) {
                  SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_MALLOC_FAILURE);
                  goto err;
              }
          }
          ciph_ctx = s->enc_write_ctx;
          iv = s->write_iv;
  
          RECORD_LAYER_reset_write_sequence(&s->rlayer);
      }
  
      if (((which & SSL3_CC_CLIENT) && (which & SSL3_CC_WRITE))
              || ((which & SSL3_CC_SERVER) && (which & SSL3_CC_READ))) {
          if (which & SSL3_CC_EARLY) {
              EVP_MD_CTX *mdctx = NULL;
              long handlen;
              void *hdata;
              unsigned int hashlenui;
              const SSL_CIPHER *sslcipher = SSL_SESSION_get0_cipher(s->session);
  
              insecret = s->early_secret;
              label = client_early_traffic;
              labellen = sizeof(client_early_traffic) - 1;
              log_label = CLIENT_EARLY_LABEL;
  
              handlen = BIO_get_mem_data(s->s3->handshake_buffer, &hdata);
              if (handlen <= 0) {
                  SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE,
                         SSL_R_BAD_HANDSHAKE_LENGTH);
                  goto err;
              }
              if (sslcipher == NULL) {
                  SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
                  goto err;
              }
  
              /*
               * We need to calculate the handshake digest using the digest from
               * the session. We haven't yet selected our ciphersuite so we can't
               * use ssl_handshake_md().
               */
              mdctx = EVP_MD_CTX_new();
              if (mdctx == NULL) {
                  SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_MALLOC_FAILURE);
                  goto err;
              }
              cipher = EVP_get_cipherbynid(SSL_CIPHER_get_cipher_nid(sslcipher));
              md = ssl_md(sslcipher->algorithm2);
              if (md == NULL || !EVP_DigestInit_ex(mdctx, md, NULL)
                      || !EVP_DigestUpdate(mdctx, hdata, handlen)
                      || !EVP_DigestFinal_ex(mdctx, hashval, &hashlenui)) {
                  SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
                  EVP_MD_CTX_free(mdctx);
                  goto err;
              }
              hashlen = hashlenui;
              EVP_MD_CTX_free(mdctx);
          } else if (which & SSL3_CC_HANDSHAKE) {
              insecret = s->handshake_secret;
              finsecret = s->client_finished_secret;
              finsecretlen = EVP_MD_size(ssl_handshake_md(s));
              label = client_handshake_traffic;
              labellen = sizeof(client_handshake_traffic) - 1;
              log_label = CLIENT_HANDSHAKE_LABEL;
              /*
               * The handshake hash used for the server read/client write handshake
               * traffic secret is the same as the hash for the server
               * write/client read handshake traffic secret. However, if we
               * processed early data then we delay changing the server
               * read/client write cipher state until later, and the handshake
               * hashes have moved on. Therefore we use the value saved earlier
               * when we did the server write/client read change cipher state.
               */
              hash = s->handshake_traffic_hash;
          } else {
              insecret = s->master_secret;
              label = client_application_traffic;
              labellen = sizeof(client_application_traffic) - 1;
              log_label = CLIENT_APPLICATION_LABEL;
              /*
               * For this we only use the handshake hashes up until the server
               * Finished hash. We do not include the client's Finished, which is
               * what ssl_handshake_hash() would give us. Instead we use the
               * previously saved value.
               */
              hash = s->server_finished_hash;
          }
      } else {
          /* Early data never applies to client-read/server-write */
          if (which & SSL3_CC_HANDSHAKE) {
              insecret = s->handshake_secret;
              finsecret = s->server_finished_secret;
              finsecretlen = EVP_MD_size(ssl_handshake_md(s));
              label = server_handshake_traffic;
              labellen = sizeof(server_handshake_traffic) - 1;
              log_label = SERVER_HANDSHAKE_LABEL;
          } else {
              insecret = s->master_secret;
              label = server_application_traffic;
              labellen = sizeof(server_application_traffic) - 1;
              log_label = SERVER_APPLICATION_LABEL;
          }
      }
  
      if (!(which & SSL3_CC_EARLY)) {
          md = ssl_handshake_md(s);
          cipher = s->s3->tmp.new_sym_enc;
          if (!ssl3_digest_cached_records(s, 1)
                  || !ssl_handshake_hash(s, hashval, sizeof(hashval), &hashlen)) {
              SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
              goto err;
          }
      }
  
      /*
       * Save the hash of handshakes up to now for use when we calculate the
       * client application traffic secret
       */
      if (label == server_application_traffic)
          memcpy(s->server_finished_hash, hashval, hashlen);
  
      if (label == server_handshake_traffic)
          memcpy(s->handshake_traffic_hash, hashval, hashlen);
  
      if (label == client_application_traffic) {
          /*
           * We also create the resumption master secret, but this time use the
           * hash for the whole handshake including the Client Finished
           */
          if (!tls13_hkdf_expand(s, ssl_handshake_md(s), insecret,
                                 resumption_master_secret,
                                 sizeof(resumption_master_secret) - 1,
                                 hashval, hashlen, s->session->master_key,
                                 hashlen)) {
              SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
              goto err;
          }
          s->session->master_key_length = hashlen;
  
          /* Now we create the exporter master secret */
          if (!tls13_hkdf_expand(s, ssl_handshake_md(s), insecret,
                                 exporter_master_secret,
                                 sizeof(exporter_master_secret) - 1,
                                 hash, hashlen, s->exporter_master_secret,
                                 hashlen)) {
              SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
              goto err;
          }
      }
  
      if (!derive_secret_key_and_iv(s, which & SSL3_CC_WRITE, md, cipher,
                                    insecret, hash, label, labellen, secret, iv,
                                    ciph_ctx)) {
          goto err;
      }
  
      if (label == server_application_traffic)
          memcpy(s->server_app_traffic_secret, secret, hashlen);
      else if (label == client_application_traffic)
          memcpy(s->client_app_traffic_secret, secret, hashlen);
  
      if (!ssl_log_secret(s, log_label, secret, hashlen)) {
          SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
          goto err;
      }
  
      if (finsecret != NULL
              && !tls13_derive_finishedkey(s, ssl_handshake_md(s), secret,
                                           finsecret, finsecretlen)) {
          SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
          goto err;
      }
  
      ret = 1;
   err:
      OPENSSL_cleanse(secret, sizeof(secret));
      return ret;
  }
  
  int tls13_update_key(SSL *s, int sending)
  {
      static const unsigned char application_traffic[] = "traffic upd";
      const EVP_MD *md = ssl_handshake_md(s);
      size_t hashlen = EVP_MD_size(md);
      unsigned char *insecret, *iv;
      unsigned char secret[EVP_MAX_MD_SIZE];
      EVP_CIPHER_CTX *ciph_ctx;
      int ret = 0;
  
      if (s->server == sending)
          insecret = s->server_app_traffic_secret;
      else
          insecret = s->client_app_traffic_secret;
  
      if (sending) {
          iv = s->write_iv;
          ciph_ctx = s->enc_write_ctx;
          RECORD_LAYER_reset_write_sequence(&s->rlayer);
      } else {
          iv = s->read_iv;
          ciph_ctx = s->enc_read_ctx;
          RECORD_LAYER_reset_read_sequence(&s->rlayer);
      }
  
      if (!derive_secret_key_and_iv(s, sending, ssl_handshake_md(s),
                                    s->s3->tmp.new_sym_enc, insecret, NULL,
                                    application_traffic,
                                    sizeof(application_traffic) - 1, secret, iv,
                                    ciph_ctx))
          goto err;
  
      memcpy(insecret, secret, hashlen);
  
      ret = 1;
   err:
      OPENSSL_cleanse(secret, sizeof(secret));
      return ret;
  }
  
  int tls13_alert_code(int code)
  {
      if (code == SSL_AD_MISSING_EXTENSION)
          return code;
  
      return tls1_alert_code(code);
  }
  
  int tls13_export_keying_material(SSL *s, unsigned char *out, size_t olen,
                                   const char *label, size_t llen,
                                   const unsigned char *context,
                                   size_t contextlen, int use_context)
  {
      unsigned char exportsecret[EVP_MAX_MD_SIZE];
      static const unsigned char exporterlabel[] = "exporter";
      unsigned char hash[EVP_MAX_MD_SIZE];
      const EVP_MD *md = ssl_handshake_md(s);
      EVP_MD_CTX *ctx = EVP_MD_CTX_new();
      unsigned int hashsize;
      int ret = 0;
  
      if (ctx == NULL || !SSL_is_init_finished(s))
          goto err;
  
      if (!use_context)
          contextlen = 0;
  
      if (EVP_DigestInit_ex(ctx, md, NULL) <= 0
              || EVP_DigestUpdate(ctx, context, contextlen) <= 0
              || EVP_DigestFinal_ex(ctx, hash, &hashsize) <= 0
              || !tls13_hkdf_expand(s, md, s->exporter_master_secret,
                                    (const unsigned char *)label, llen, NULL, 0,
                                    exportsecret, hashsize)
              || !tls13_hkdf_expand(s, md, exportsecret, exporterlabel,
                                    sizeof(exporterlabel) - 1, hash, hashsize,
                                    out, olen))
          goto err;
  
      ret = 1;
   err:
      EVP_MD_CTX_free(ctx);
      return ret;
  }
  