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#pike __REAL_VERSION__ 
#pragma strict_types 
#require constant(SSL.Cipher) 
 
//! The most important information in a session object is a 
//! choice of encryption algorithms and a "master secret" created by 
//! keyexchange with a client. Each connection can either do a full key 
//! exchange to established a new session, or reuse a previously 
//! established session. That is why we have the session abstraction and 
//! the session cache. Each session is used by one or more connections, in 
//! sequence or simultaneously. 
//! 
//! It is also possible to change to a new session in the middle of a 
//! connection. 
 
#include "tls.h" 
 
import "."; 
import Constants; 
 
//! When this session object was used last. 
int last_activity = time(); 
 
//! Identifies the session to the server 
string(8bit) identity; 
 
//! Alternative identification of the session to the server. 
//! @seealso 
//!   @rfc{4507@}, @rfc{5077@} 
string(8bit) ticket; 
 
//! Expiry time for @[ticket]. 
int ticket_expiry_time; 
 
//! Always COMPRESSION_null. 
int compression_algorithm; 
 
//! Constant defining a choice of keyexchange, encryption and mac 
//! algorithm. 
int cipher_suite; 
 
//! Information about the encryption method derived from the 
//! cipher_suite. 
Cipher.CipherSpec cipher_spec; 
 
//! 48 byte secret shared between the client and the server. Used for 
//! deriving the actual keys. 
string(8bit) master_secret; 
 
//! Information about the certificate in use by the peer, such as 
//! issuing authority, and verification status. 
mapping cert_data; 
 
//! Negotiated protocol version. 
ProtocolVersion version; 
 
//! The peer certificate chain 
array(string(8bit)) peer_certificate_chain; 
 
//! Our certificate chain 
array(string(8bit)) certificate_chain; 
 
//! Our private key. 
Crypto.Sign.State private_key; 
 
//! The peer's public key (from the certificate). 
Crypto.Sign.State peer_public_key; 
 
//! The max fragment size requested by the client. 
int max_packet_size = PACKET_MAX_SIZE; 
 
//! Indicates that the packet HMACs should be truncated 
//! to the first 10 bytes (80 bits). Cf @rfc{3546:3.5@}. 
int(0..1) truncated_hmac; 
 
//! Indicates that the connection uses the Extended Master Secret method 
//! of deriving the master secret. 
//! 
//! This setting is only relevant for TLS 1.2 and earlier. 
int(0..1) extended_master_secret; 
 
protected void create(string(8bit)|void id) 
{ 
  identity = id; 
} 
 
/* 
 * Extensions provided by the peer. 
 */ 
 
//! @rfc{6066:3.1@} (SNI) 
string(8bit) server_name; 
 
//! The set of <hash, signature> combinations supported by the peer. 
//! 
//! Only used with TLS 1.2 and later. 
//! 
//! Defaults to the settings from @rfc{5246:7.4.1.4.1@}. 
array(array(int)) signature_algorithms = ({ 
  // RFC 5246 7.4.1.4.1: 
  // Note: this is a change from TLS 1.1 where there are no explicit 
  // rules, but as a practical matter one can assume that the peer 
  // supports MD5 and SHA-1. 
  ({ HASH_sha1, SIGNATURE_rsa }), 
  ({ HASH_sha1, SIGNATURE_dsa }), 
  ({ HASH_sha1, SIGNATURE_ecdsa }), 
}); 
 
//! Supported finite field diffie-hellman groups in order of preference. 
//! 
//! @mixed 
//!   @type int(0..0) 
//!     Zero indicates that none have been specified. 
//!   @type array(zero) 
//!     The empty array indicates that none are supported. 
//!   @type array(int) 
//!     List of supported groups, with the most preferred first. 
//! @endmixed 
array(int) ffdhe_groups; 
 
//! Supported elliptical curve cipher curves in order of preference. 
array(int) ecc_curves = ({}); 
 
//! The selected elliptical curve point format. 
//! 
//! @note 
//!   May be @expr{-1@} to indicate that there's no supported overlap 
//!   between the server and client. 
int ecc_point_format = POINT_uncompressed; 
 
//! Negotiated encrypt-then-mac mode. 
int encrypt_then_mac = 0; 
 
/* 
 * End of extensions. 
 */ 
 
#if constant(Crypto.ECC.Curve) 
//! The ECC curve selected by the key exchange. 
//! 
//! @int 
//!   @value KE_ecdh_ecdsa 
//!   @value KE_ecdh_rsa 
//!     The curve from the server certificate. 
//! 
//!   @value KE_ecdhe_ecdsa 
//!   @value KE_ecdhe_rsa 
//!   @value KE_ecdh_anon 
//!     The curve selected for the ECDHE key exchange 
//!     (typically the largest curve supported by both 
//!     the client and the server). 
//! @endint 
Crypto.ECC.Curve curve; 
#endif /* Crypto.ECC.Curve */ 
 
//! Heartbeat mode. 
HeartBeatModeType heartbeat_mode = HEARTBEAT_MODE_disabled; 
 
//! Indicates if this session has the required server certificate keys 
//! set. No means that no or the wrong type of certificate was sent 
//! from the server. 
int(0..1) has_required_certificates() 
{ 
  if (!peer_public_key) 
    return (cipher_spec->signature_alg == SIGNATURE_anonymous); 
  return 1; 
} 
 
//! Used to filter certificates not supported by the peer. 
//! 
//! @param cp 
//!   Candidate @[CertificatePair]. 
//! 
//! @param version 
//!   Negotiated version of SSL. 
//! 
//! @param ecc_curves 
//!   The set of ecc_curves supported by the peer. 
protected int(0..1) is_supported_cert(CertificatePair cp, 
                                      int ke_mask, 
                                      int h_max, 
                                      ProtocolVersion version, 
                                      array(int) ecc_curves) 
{ 
  // Check if the certificate is useful for any of the 
  // key exchange algorithms that the peer supports. 
  if (version >= PROTOCOL_TLS_1_2) { 
    // In TLS 1.2 and later DH_DSS/DH_RSA and ECDH_ECDSA/ECDH_RSA 
    // have been unified, so use the invariant ke_mask. 
    // They have been unified, since the signature_algorithms 
    // extension allows the peer to specify exactly which 
    // combinations it supports, cf below. 
    if (!(ke_mask & cp->ke_mask_invariant)) return 0; 
 
    // Check that all sign_algs in the cert chain are supported by the peer. 
    foreach(cp->sign_algs, array(int) sign_alg) { 
      int found; 
      foreach(signature_algorithms, array(int) sup_alg) { 
        if (found = equal(sign_alg, sup_alg)) break; 
      } 
      if (!found) return 0; 
    } 
  } else if (!(ke_mask & cp->ke_mask)) 
    return 0; 
 
#if constant(Crypto.ECC.Curve) 
  if (cp->key->get_curve) { 
    // Is the ECC curve supported by the client? 
    Crypto.ECC.Curve c = 
      ([object(Crypto.ECC.Curve.ECDSA)]cp->key)->get_curve(); 
    SSL3_DEBUG_MSG("Curve: %O (%O)\n", 
                   c, ECC_NAME_TO_CURVE[c->name()]); 
    return has_value(ecc_curves, ECC_NAME_TO_CURVE[c->name()]); 
  } 
#endif 
  return 1; 
} 
 
//! Used to filter the set of cipher suites suggested by the peer 
//! based on our available certificates. 
//! 
//! @param suite 
//!   Candidate cipher suite. 
//! 
//! @param ke_mask 
//!   The bit mask of the key exchange algorithms supported by 
//!   the set of available certificates. 
//! 
//! @param version 
//!   The negotiated version of SSL/TLS. 
int(0..1) is_supported_suite(int suite, int ke_mask, ProtocolVersion version) 
{ 
  array(int) suite_info = [array(int)]CIPHER_SUITES[suite]; 
  if (!suite_info) { 
    SSL3_DEBUG_MSG("Suite %s is not supported.\n", fmt_cipher_suite(suite)); 
    return 0; 
  } 
 
  KeyExchangeType ke = [int(0..0)|KeyExchangeType]suite_info[0]; 
  if (!(ke_mask & (1<<ke))) return 0; 
 
  if (version < PROTOCOL_TLS_1_2) { 
    if (sizeof(suite_info) >= 4) { 
      // AEAD protocols are not supported prior to TLS 1.2. 
      // Variant cipher-suite dependent prfs are not supported prior to TLS 1.2. 
      return 0; 
    } 
    if (suite_info[2] > HASH_sha1) { 
      // Hash algorithms other than md5 and sha1 are not supported 
      // prior to TLS 1.2. 
      return 0; 
    } 
    // FIXME: Check hash size >= cert hash size. 
  } 
 
  if (version >= PROTOCOL_TLS_1_1) 
  { 
    if (suite == SSL_null_with_null_null) 
    { 
      // This suite is not allowed to be negotiated in TLS 1.1. 
      return 0; 
    } 
 
    if ( (< CIPHER_rc4_40, CIPHER_rc2_40, CIPHER_des40 >)[suite_info[1]]) { 
      // RFC 4346 A.5: Export suites 
      // TLS 1.1 implementations MUST NOT negotiate 
      // these cipher suites in TLS 1.1 mode. 
      // ... 
      // TLS 1.1 clients MUST check that the server 
      // did not choose one of these cipher suites 
      // during the handshake. 
      return 0; 
    } 
  } 
 
  return 1; 
} 
 
private array(CertificatePair) 
  select_certificates(array(CertificatePair) certs, 
                      array(int) cipher_suites, 
                      ProtocolVersion version) 
{ 
  SSL3_DEBUG_MSG("Candidate certificates: %O\n", certs); 
 
  // Find the set of key exchange and hash algorithms supported by the 
  // client. 
  int ke_mask = 0; 
  int h_max = 0; 
  foreach(cipher_suites, int suite) { 
    if (CIPHER_SUITES[suite]) { 
      ke_mask |= 1 << [int(0..22)](CIPHER_SUITES[suite][0]); 
      Crypto.Hash hash = 
        [object(Crypto.Hash)]HASH_lookup[CIPHER_SUITES[suite][2]]; 
      if (hash && (hash->digest_size() > h_max)) { 
        h_max = hash->digest_size(); 
      } 
    } 
  } 
 
#if constant(Crypto.ECC.Curve) 
  if (!sizeof(ecc_curves) || ecc_point_format==-1) { 
    // Client and server have no common curves, so remove ECC from KE 
    // mask. This would be caught anyway in the curve check in 
    // is_supported_cert, but this gives the code an earlier out. 
    ke_mask &= ~KE_ecc_mask; 
  } 
#endif 
 
  // Filter any certs that the client doesn't support. 
  certs = [array(CertificatePair)] 
    filter(certs, is_supported_cert, ke_mask, h_max, version, ecc_curves); 
 
  if( version<PROTOCOL_TLS_1_2 && sizeof(certs)>1 ) 
  { 
    // GNU-TLS doesn't like eg SHA being used with SHA256 certs. 
    // FIXME: Can this be made more narrow? 
    array(CertificatePair) c = [array(CertificatePair)] 
      filter(certs, lambda(CertificatePair cp) 
        { 
          Crypto.Hash hash = [object(Crypto.Hash)] 
            HASH_lookup[cp->sign_algs[0][0]]; 
          return hash->digest_size() <= h_max; 
        }); 
    // Don't clear out the entire list though, as that makes all peers 
    // fail. 
    if( sizeof(c) ) 
      certs = c; 
  } 
 
  SSL3_DEBUG_MSG("Client supported certificates: %O\n", certs); 
  return certs; 
} 
 
//! Selects an apropriate certificate, authentication method 
//! and cipher suite for the parameters provided by the client. 
//! 
//! @param certs 
//!   The list of @[CertificatePair]s that are applicable to the 
//!   @[server_name] of this session. 
//! 
//! @param cipher_suites 
//!   The set of cipher suites that the client and server have in 
//!   common. 
//! 
//! @param version 
//!   The SSL protocol version to use. 
//! 
//! Typical client extensions that also are used: 
//! @dl 
//!   @item @[signature_algorithms] 
//!     The set of signature algorithm tuples that 
//!     the client claims to support. 
//! @enddl 
int select_cipher_suite(array(CertificatePair) certs, 
                        array(int) cipher_suites, 
                        ProtocolVersion version) 
{ 
  if (!sizeof(cipher_suites)) return 0; 
 
  if (!certs || !sizeof(certs)) 
  { 
    SSL3_DEBUG_MSG("No certificates.\n"); 
 
    foreach(cipher_suites, int suite) 
      if (KE_Anonymous[CIPHER_SUITES[suite][0]]) 
        return set_cipher_suite(suite, version, 0, 0); 
 
    return 0; 
  } 
 
  certs = select_certificates(certs, cipher_suites, version); 
 
  // Find the set of key exchange algorithms supported by 
  // the remaining certs. 
  int ke_mask = (1<<KE_null)|(1<<KE_dh_anon)|(1<<KE_psk)|(1<<KE_dhe_psk) 
#if constant(Crypto.ECC.Curve) 
    |(1<<KE_ecdh_anon)|(1<<KE_ecdhe_psk) 
#endif 
    ; 
  if (version >= PROTOCOL_TLS_1_2) { 
    ke_mask = `|(ke_mask, @certs->ke_mask_invariant); 
  } else { 
    ke_mask = `|(ke_mask, @certs->ke_mask); 
  } 
 
#if constant(Crypto.ECC.Curve) 
  if (!sizeof(ecc_curves) || ecc_point_format==-1) { 
    // The client may claim to support ECC, but hasn't sent the 
    // required extension or any curves that we support, so 
    // remove ECC from KE mask. 
    ke_mask &= ~KE_ecc_mask; 
  } 
#endif 
 
  if (!sizeof(ffdhe_groups)) { 
    // The client doesn't support the same set of Finite Field 
    // Diffie-Hellman groups as we do, so filter DHE. 
    ke_mask &= ~((1<<KE_dhe_dss)|(1<<KE_dhe_rsa)| 
                 (1<<KE_dh_anon)|(1<<KE_dhe_psk)); 
  } 
 
  if (version >= PROTOCOL_TLS_1_3) { 
    // TLS 1.3 and later only support ephemeral keyexchanges. 
    ke_mask &= ((1<<KE_dhe_dss)|(1<<KE_dhe_rsa)|(1<<KE_dh_anon)| 
                (1<<KE_ecdhe_ecdsa)|(1<<KE_ecdhe_rsa)|(1<<KE_ecdh_anon)); 
  } 
 
  // Given the set of certs, filter the set of client_suites, 
  // to find the best. 
  int suite = -1; 
  foreach(cipher_suites, int s) 
    if( is_supported_suite(s, ke_mask, version) ) { 
      suite = s; 
      break; 
    } 
 
  if (suite==-1) { 
    SSL3_DEBUG_MSG("No suites left after certificate filtering.\n"); 
    return 0; 
  } 
 
  SSL3_DEBUG_MSG("selected suite:\n%s\n", fmt_cipher_suite(suite)); 
 
  int ke_method = [int]CIPHER_SUITES[suite][0]; 
 
  SSL3_DEBUG_MSG("Selecting server key and certificate.\n"); 
 
  int max_hash_size = 512; 
 
  // Now we can select the actual cert to use. 
  if ( !KE_Anonymous[ke_method] ) { 
    CertificatePair cert; 
 
    if (version >= PROTOCOL_TLS_1_2) { 
      foreach(certs, CertificatePair cp) { 
        if (is_supported_suite(suite, cp->ke_mask_invariant, version)) { 
          cert = cp; 
          break; 
        } 
      } 
    } else { 
      foreach(certs, CertificatePair cp) { 
        if (is_supported_suite(suite, cp->ke_mask, version)) { 
          cert = cp; 
          break; 
        } 
      } 
    } 
 
    if (!cert) { 
      error("No suitable certificate for selected cipher suite: %s.\n", 
            fmt_cipher_suite(suite)); 
    } 
 
    private_key = cert->key; 
    SSL3_DEBUG_MSG("Selected server key: %O\n", private_key); 
 
    certificate_chain = cert->certs; 
#if constant(Crypto.ECC.Curve) 
    if (private_key->get_curve) { 
      curve = [object(Crypto.ECC.Curve)]private_key->get_curve(); 
    } 
#endif /* Crypto.ECC.Curve */ 
 
    if (private_key->block_size) { 
      // FIXME: The maximum allowable hash size depends on the size of the 
      //        RSA key when RSA is in use. With a 64 byte (512 bit) key, 
      //        the block size is 61 bytes, allow for 23 bytes of overhead. 
      max_hash_size = [int]private_key->block_size() - 23; 
    } 
  } 
 
  return set_cipher_suite(suite, version, signature_algorithms, 
                          max_hash_size); 
} 
 
//! Sets the proper authentication method and cipher specification 
//! for the given parameters. 
//! 
//! @param suite 
//!   The cipher suite to use, selected from the set that the client 
//!   claims to support. 
//! 
//! @param version 
//!   The SSL protocol version to use. 
//! 
//! @param signature_algorithms 
//!   The set of signature algorithms tuples that the client claims to 
//!   support. 
//! 
//! @param max_hash_size 
//! 
int set_cipher_suite(int suite, ProtocolVersion version, 
                     array(array(int)) signature_algorithms, 
                     int max_hash_size) 
{ 
  this::version = version; 
 
  cipher_spec = Cipher.lookup(suite, version, signature_algorithms, 
                            truncated_hmac?512:max_hash_size); 
  if (!cipher_spec) return 0; 
 
  cipher_suite = suite; 
  SSL3_DEBUG_MSG("SSL.Session: cipher_spec %O\n", 
                 mkmapping(indices(cipher_spec), values(cipher_spec))); 
 
  if (encrypt_then_mac) { 
    // Check if enrypt-then-mac is valid for the suite. 
    if (((sizeof(CIPHER_SUITES[suite]) == 3) && 
         ((< CIPHER_rc4, CIPHER_rc4_40 >)[CIPHER_SUITES[suite][1]])) || 
        ((sizeof(CIPHER_SUITES[suite]) == 4) && 
         (CIPHER_SUITES[suite][3] != MODE_cbc))) { 
      // Encrypt-then-MAC not allowed with non-CBC suites. 
      encrypt_then_mac = 0; 
      SSL3_DEBUG_MSG("Encrypt-then-MAC: Disabled (not valid for suite).\n"); 
    } else { 
      SSL3_DEBUG_MSG("Encrypt-then-MAC: Enabled.\n"); 
    } 
  } 
 
  return 1; 
} 
 
//! Sets the compression method. Currently only @[COMPRESSION_null] 
//! and @[COMPRESSION_deflate] are supported. 
void set_compression_method(int compr) 
{ 
  if( !(< COMPRESSION_null, COMPRESSION_deflate >)[ compr ] ) 
    error( "Method not supported\n" ); 
 
  compression_algorithm = compr; 
} 
 
protected string(8bit) generate_key_block(string(8bit) client_random, 
                                          string(8bit) server_random, 
                                          ProtocolVersion version) 
{ 
  int required = 2 * ( 
    cipher_spec->is_exportable ? 
    (5 + cipher_spec->hash_size) 
    : ( cipher_spec->key_material + 
        cipher_spec->hash_size + 
        cipher_spec->iv_size) 
  ); 
  string(8bit) key = ""; 
 
  key = cipher_spec->prf(master_secret, "key expansion", 
                         server_random + client_random, required); 
 
  SSL3_DEBUG_MSG("key_block: %O\n", key); 
  return key; 
} 
 
#ifdef SSL3_DEBUG 
protected void printKey(string name, string(8bit) key) 
{ 
  werror("%s:  len:%d \t\t%x\n", name, sizeof(key), key); 
} 
#endif 
 
//! Generates keys appropriate for the SSL version given in @[version], 
//! based on the @[client_random] and @[server_random]. 
//! @returns 
//!   @array 
//!     @elem string 0 
//!       Client write MAC secret 
//!     @elem string 1 
//!       Server write MAC secret 
//!     @elem string 2 
//!       Client write key 
//!     @elem string 3 
//!       Server write key 
//!     @elem string 4 
//!       Client write IV 
//!     @elem string 5 
//!       Server write IV 
//!  @endarray 
array(string(8bit)) generate_keys(string(8bit) client_random, 
                                  string(8bit) server_random, 
                                  ProtocolVersion version) 
{ 
  Stdio.Buffer key_data = Stdio.Buffer(generate_key_block(client_random, 
                                                          server_random, 
                                                          version)); 
  array(string(8bit)) keys = allocate(6); 
 
  SSL3_DEBUG_MSG("client_random: %s\nserver_random: %s\nversion: %d.%d\n", 
                 client_random?String.string2hex(client_random):"NULL", 
                 server_random?String.string2hex(server_random):"NULL", 
                 version>>8, version & 0xff); 
 
  // client_write_MAC_secret 
  keys[0] = key_data->read(cipher_spec->hash_size); 
  // server_write_MAC_secret 
  keys[1] = key_data->read(cipher_spec->hash_size); 
 
  if (cipher_spec->is_exportable) 
  { 
    // Exportable (ie weak) crypto. 
    if(version == PROTOCOL_SSL_3_0) { 
      // SSL 3.0 
      keys[2] = Crypto.MD5.hash(key_data->read(5) + 
                                client_random + server_random) 
        [..cipher_spec->key_material-1]; 
      keys[3] = Crypto.MD5.hash(key_data->read(5) + 
                                server_random + client_random) 
        [..cipher_spec->key_material-1]; 
      if (cipher_spec->iv_size) 
        { 
          keys[4] = Crypto.MD5.hash(client_random + 
                                    server_random)[..cipher_spec->iv_size-1]; 
          keys[5] = Crypto.MD5.hash(server_random + 
                                    client_random)[..cipher_spec->iv_size-1]; 
        } 
 
    } else if(version >= PROTOCOL_TLS_1_0) { 
      // TLS 1.0 or later. 
      string(8bit) client_wkey = key_data->read(5); 
      string(8bit) server_wkey = key_data->read(5); 
      keys[2] = cipher_spec->prf(client_wkey, "client write key", 
                                 client_random + server_random, 
                                 cipher_spec->key_material); 
      keys[3] = cipher_spec->prf(server_wkey, "server write key", 
                                 client_random + server_random, 
                                 cipher_spec->key_material); 
      if(cipher_spec->iv_size) { 
        string(8bit) iv_block = 
          cipher_spec->prf("", "IV block", 
                           client_random + server_random, 
                           2 * cipher_spec->iv_size); 
        keys[4]=iv_block[..cipher_spec->iv_size-1]; 
        keys[5]=iv_block[cipher_spec->iv_size..]; 
        SSL3_DEBUG_MSG("sizeof(keys[4]):%d  sizeof(keys[5]):%d\n", 
                       sizeof(keys[4]), sizeof(keys[4])); 
      } 
 
    } 
 
  } 
  else { 
    keys[2] = key_data->read(cipher_spec->key_material); 
    keys[3] = key_data->read(cipher_spec->key_material); 
    if (cipher_spec->iv_size) 
      { 
        keys[4] = key_data->read(cipher_spec->iv_size); 
        keys[5] = key_data->read(cipher_spec->iv_size); 
      } 
  } 
 
#ifdef SSL3_DEBUG 
  printKey( "client_write_MAC_secret",keys[0]); 
  printKey( "server_write_MAC_secret",keys[1]); 
  printKey( "client_write_key", keys[2]); 
  printKey( "server_write_key", keys[3]); 
 
  if(cipher_spec->iv_size) { 
    printKey( "client_IV", keys[4]); 
    printKey( "server_IV", keys[5]); 
  } else { 
    werror("No IVs!!\n"); 
  } 
#endif 
 
  return keys; 
} 
 
//! Computes a new set of encryption states, derived from the 
//! client_random, server_random and master_secret strings. 
//! 
//! @returns 
//!   @array 
//!     @elem SSL.State read_state 
//!       Read state 
//!     @elem SSL.State write_state 
//!       Write state 
//!   @endarray 
array(State) new_server_states(.Connection con, 
                                string(8bit) client_random, 
                                string(8bit) server_random, 
                                ProtocolVersion version) 
{ 
  State write_state = State(con); 
  State read_state = State(con); 
  array(string) keys = generate_keys(client_random, server_random, version); 
 
  if (cipher_spec->mac_algorithm) 
  { 
    SSL3_DEBUG_CRYPT_MSG("MAC algorithm: %O\n", cipher_spec->mac_algorithm); 
    read_state->mac = cipher_spec->mac_algorithm(keys[0]); 
    write_state->mac = cipher_spec->mac_algorithm(keys[1]); 
  } 
  if (cipher_spec->bulk_cipher_algorithm) 
  { 
    SSL3_DEBUG_CRYPT_MSG("Bulk cipher algorithm: %O\n", 
                         cipher_spec->bulk_cipher_algorithm); 
    read_state->crypt = cipher_spec->bulk_cipher_algorithm(); 
    read_state->crypt->set_decrypt_key(keys[2]); 
    write_state->crypt = cipher_spec->bulk_cipher_algorithm(); 
    write_state->crypt->set_encrypt_key(keys[3]); 
    if (cipher_spec->cipher_type == CIPHER_aead) { 
      // AEAD algorithms use other iv methods. 
      read_state->tls_iv = write_state->tls_iv = 0; 
      read_state->salt = keys[4] || ""; 
      write_state->salt = keys[5] || ""; 
    } else if (cipher_spec->iv_size) { 
      if (version >= PROTOCOL_TLS_1_1) { 
        // TLS 1.1 and later have an explicit IV. 
        read_state->tls_iv = write_state->tls_iv = cipher_spec->iv_size; 
      } 
      read_state->crypt->set_iv(keys[4]); 
      write_state->crypt->set_iv(keys[5]); 
    } 
  } 
 
  switch(compression_algorithm) { 
  case COMPRESSION_deflate: 
#if constant(Gz) 
    read_state->compress = Gz.inflate()->inflate; 
    write_state->compress = 
      class(function(string(8bit), int:string(8bit)) _deflate) { 
        string(8bit) deflate(string(8bit) s) { 
          // RFC 3749 2: 
          //   All data that was submitted for compression MUST be 
          //   included in the compressed output, with no data 
          //   retained to be included in a later output payload. 
          //   Flushing ensures that each compressed packet payload 
          //   can be decompressed completely. 
          return _deflate(s, Gz.SYNC_FLUSH); 
        } 
      }(Gz.deflate()->deflate)->deflate; 
#endif 
    break; 
  } 
  return ({ read_state, write_state }); 
} 
 
//! Computes a new set of encryption states, derived from the 
//! client_random, server_random and master_secret strings. 
//! 
//! @returns 
//!   @array 
//!     @elem SSL.State read_state 
//!       Read state 
//!     @elem SSL.State write_state 
//!       Write state 
//!   @endarray 
array(State) new_client_states(.Connection con, 
                                string(8bit) client_random, 
                                string(8bit) server_random, 
                                ProtocolVersion version) 
{ 
  State write_state = State(con); 
  State read_state = State(con); 
  array(string) keys = generate_keys(client_random, server_random, version); 
 
  if (cipher_spec->mac_algorithm) 
  { 
    read_state->mac = cipher_spec->mac_algorithm(keys[1]); 
    write_state->mac = cipher_spec->mac_algorithm(keys[0]); 
  } 
  if (cipher_spec->bulk_cipher_algorithm) 
  { 
    read_state->crypt = cipher_spec->bulk_cipher_algorithm(); 
    read_state->crypt->set_decrypt_key(keys[3]); 
    write_state->crypt = cipher_spec->bulk_cipher_algorithm(); 
    write_state->crypt->set_encrypt_key(keys[2]); 
    if (cipher_spec->cipher_type == CIPHER_aead) { 
      // AEAD algorithms use other iv methods. 
      read_state->tls_iv = write_state->tls_iv = 0; 
      read_state->salt = keys[5] || ""; 
      write_state->salt = keys[4] || ""; 
    } else if (cipher_spec->iv_size) { 
      if (version >= PROTOCOL_TLS_1_1) { 
        // TLS 1.1 and later have an explicit IV. 
        read_state->tls_iv = write_state->tls_iv = cipher_spec->iv_size; 
      } 
      read_state->crypt->set_iv(keys[5]); 
      write_state->crypt->set_iv(keys[4]); 
    } 
  } 
 
  switch(compression_algorithm) { 
  case COMPRESSION_deflate: 
#if constant(Gz) 
    read_state->compress = Gz.inflate()->inflate; 
    write_state->compress = 
      class(function(string(8bit), int:string(8bit)) _deflate) { 
        string(8bit) deflate(string(8bit) s) { 
          // RFC 3749 2: 
          //   All data that was submitted for compression MUST be 
          //   included in the compressed output, with no data 
          //   retained to be included in a later output payload. 
          //   Flushing ensures that each compressed packet payload 
          //   can be decompressed completely. 
          return _deflate(s, Gz.SYNC_FLUSH); 
        } 
      }(Gz.deflate()->deflate)->deflate; 
#endif 
    break; 
  } 
  return ({ read_state, write_state }); 
} 
 
//! Returns true if this session object can be used in place of the 
//! session object @[other]. 
int(0..1) reusable_as(Session other) 
{ 
  // SSL3 5.6.1.2: 
  // If the session_id field is not empty (implying a session 
  // resumption request) this vector [cipher_suites] must 
  // include at least the cipher_suite from that session. 
  // ... 
  // If the session_id field is not empty (implying a session 
  // resumption request) this vector [compression_methods] 
  // must include at least the compression_method from 
  // that session. 
 
  // We use a *much* stricter test, and only reuse the old session 
  // if it has the same parameters as the new session. 
  return cipher_suite == other->cipher_suite && 
    version == other->version && 
    certificate_chain == other->certificate_chain && 
    compression_algorithm == other->compression_algorithm && 
    max_packet_size == other->max_packet_size && 
    truncated_hmac == other->truncated_hmac && 
    server_name == other->server_name && 
    ecc_point_format == other->ecc_point_format && 
    encrypt_then_mac == other->encrypt_then_mac && 
    equal(signature_algorithms, other->signature_algorithms) && 
    equal(ecc_curves, other->ecc_curves) && 
    equal(ffdhe_groups, other->ffdhe_groups); 
}