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#pike __REAL_VERSION__ 
// #pragma strict_types 
#require constant(SSL.Cipher) 
#include "tls.h" 
 
//! The state object handles a one-way stream of packets, and operates 
//! in either decryption or encryption mode. A connection switches 
//! from one set of state objects to another, one or more times during 
//! its lifetime. 
 
import "."; 
import Constants; 
 
function(int, int, string|void: Alert) alert; 
 
protected void create(Connection con) 
{ 
  session = con->session; 
  alert = con->alert; 
} 
 
//! Information about the used algorithms. 
Session session; 
 
//! Message Authentication Code 
Cipher.MACAlgorithm mac; 
 
//! Encryption or decryption object. 
Cipher.CipherAlgorithm crypt; 
 
function(string(8bit),int(1bit)|void:string(8bit)) compress; 
 
//! 64-bit sequence number. 
int seq_num = 0;    /* Bignum, values 0, .. 2^64-1 are valid */ 
 
//! TLS IV prefix length. 
int tls_iv; 
 
//! TLS 1.2 IV salt. 
//! This is used as a prefix for the IV for the AEAD cipher algorithms. 
string salt; 
 
//! Destructively decrypts a packet (including inflating and MAC-verification, 
//! if needed). On success, returns the decrypted packet. On failure, 
//! returns an alert packet. These cases are distinguished by looking 
//! at the is_alert attribute of the returned packet. 
Alert|Packet decrypt_packet(Packet packet) 
{ 
  /* NOTE: TLS 1.1 recommends performing the hash check before 
   *       sending the alerts to protect against timing attacks. 
   * 
   *       This is also needed to alleviate the "Lucky Thirteen" attack. 
   * 
   *       We thus delay sending of any alerts to the end of the 
   *       function, and attempt to make the same amount of work 
   *       even if we have already detected a failure. 
   */ 
  Alert fail; 
  ProtocolVersion version = packet->protocol_version; 
  string data = packet->fragment; 
 
  if (!data) 
  { 
    // packet->fragment is zero when the packet format is illegal, 
    // so returning early is safe. We should never get to this 
    // though, as decrypt_packet isn't called from connection if the 
    // fragment isn't successfully parsed. 
    return alert(ALERT_fatal, ALERT_unexpected_message, 
                 "SSL.State: Failed to get fragment.\n"); 
  } 
 
  SSL3_DEBUG_CRYPT_MSG("SSL.State->decrypt_packet " 
                       "(3.%d, type: %d, seq_num: %d): data = %O\n", 
                       version & 0xff, packet->content_type, seq_num, data); 
 
  int hmac_size = mac && (session->truncated_hmac ? 10 : 
                          session->cipher_spec?->hash_size); 
  int padding; 
 
  if (hmac_size && session->encrypt_then_mac) { 
    string(8bit) digest = data[<hmac_size-1..]; 
    data = data[..<hmac_size]; 
 
    // Set data without HMAC. This never returns an Alert as the data 
    // is smaller. 
    packet->set_encrypted(data); 
 
    if (mac->hash_packet(packet, seq_num)[..hmac_size-1] != 
        digest) { 
      // Bad digest. 
      SSL3_DEBUG_MSG("Failed MAC-verification!!\n"); 
      SSL3_DEBUG_CRYPT_MSG("Expected digest: %O\n" 
                           "Calculated digest: %O\n" 
                           "Seqence number: %O\n", 
                           digest, 
                           mac->hash_packet(packet, seq_num)[..hmac_size-1], 
                           seq_num); 
      return alert(ALERT_fatal, ALERT_bad_record_mac, 
                   "Bad MAC-verification.\n"); 
    } 
    seq_num++; 
    hmac_size = 0; 
  } 
 
  if (crypt) 
  { 
    SSL3_DEBUG_CRYPT_MSG("SSL.State: Trying decrypt...\n"); 
    SSL3_DEBUG_CRYPT_MSG("encrypted packet size is %d\n", sizeof(data)); 
 
    string msg = data; 
 
    switch(session->cipher_spec->cipher_type) { 
    case CIPHER_stream: 
 
      // If data is too small, we can safely abort early. 
      if( sizeof(msg) < hmac_size+1 ) 
        return alert(ALERT_fatal, ALERT_unexpected_message, 
                     "SSL.State: Too short message.\n"); 
 
      msg = crypt->crypt(msg); 
      break; 
 
    case CIPHER_block: 
 
      // If data is too small or doesn't match block size, we can 
      // safely abort early. 
      if( sizeof(msg) < hmac_size+1 || sizeof(msg) % crypt->block_size() ) 
        return alert(ALERT_fatal, ALERT_unexpected_message, 
                     "SSL.State: Too short message.\n"); 
 
      if(version == PROTOCOL_SSL_3_0) { 
        // crypt->unpad() performs decrypt. 
        if (catch { msg = crypt->unpad(msg, Crypto.PAD_SSL); }) 
          fail = alert(ALERT_fatal, ALERT_unexpected_message, 
                       "SSL.State: Invalid padding.\n"); 
      } else if (version >= PROTOCOL_TLS_1_0) { 
 
        SSL3_DEBUG_CRYPT_MSG("SSL.State: Decrypted message: %O.\n", msg); 
        if (catch { msg = crypt->unpad(msg, Crypto.PAD_TLS); }) { 
          fail = alert(ALERT_fatal, ALERT_unexpected_message, 
                       "SSL.State: Invalid padding.\n"); 
        } else if (!msg) { 
          // TLS 1.1 requires a bad_record_mac alert on invalid padding. 
          // Note that mac will still be calculated below even if 
          // padding was wrong, to mitigate Lucky Thirteen attacks. 
          fail = alert(ALERT_fatal, ALERT_bad_record_mac, 
                       "SSL.State: Invalid padding.\n"); 
        } 
      } 
      break; 
 
    case CIPHER_aead: 
 
      // NB: Only valid in TLS 1.2 and later. 
      string iv; 
      if (session->cipher_spec->explicit_iv_size) { 
        // The message consists of explicit_iv + crypted-msg + digest. 
        iv = salt + msg[..session->cipher_spec->explicit_iv_size-1]; 
      } else { 
        // ChaCha20-POLY1305 uses an implicit iv, and no salt, 
        // but we've generalized it here to allow for ciphers 
        // using salt and implicit iv. 
        iv = sprintf("%s%*c", salt, crypt->iv_size() - sizeof(salt), seq_num); 
      } 
      SSL3_DEBUG_CRYPT_MSG("SSL.State: AEAD IV: %O.\n", iv); 
 
      int digest_size = crypt->digest_size(); 
      string digest = msg[<digest_size-1..]; 
      crypt->set_iv(iv); 
      string auth_data; 
      if (version >= PROTOCOL_TLS_1_3) { 
        auth_data = sprintf("%8c%c%2c", 
                            seq_num, packet->content_type, version); 
      } else { 
        auth_data = sprintf("%8c%c%2c%2c", 
                            seq_num, packet->content_type, version, 
                            sizeof(msg) - 
                            (session->cipher_spec->explicit_iv_size + 
                             digest_size)); 
      } 
      SSL3_DEBUG_CRYPT_MSG("SSL.State: AEAD Auth data: %O.\n", auth_data); 
 
      crypt->update(auth_data); 
      msg = crypt->crypt(msg[session->cipher_spec->explicit_iv_size.. 
                             <digest_size]); 
      SSL3_DEBUG_CRYPT_MSG("SSL.State: Decrypted message: %O.\n", msg); 
      seq_num++; 
      if (digest != crypt->digest()) { 
        // Bad digest. 
        fail = alert(ALERT_fatal, ALERT_bad_record_mac, 
                     "Failed AEAD-verification!!\n"); 
      } 
      break; 
    } 
 
    if (!msg) msg = data; 
    padding = sizeof(data) - sizeof(msg); 
    data = msg; 
  } 
 
  SSL3_DEBUG_CRYPT_MSG("SSL.State: Decrypted_packet %O\n", data); 
 
  if (tls_iv) { 
    // TLS 1.1 IV. RFC 4346 6.2.3.2: 
    // The decryption operation for all three alternatives is the same. 
    // The receiver decrypts the entire GenericBlockCipher structure and 
    // then discards the first cipher block, corresponding to the IV 
    // component. 
    data = data[tls_iv..]; 
  } 
 
  if (hmac_size) 
  { 
    SSL3_DEBUG_CRYPT_MSG("SSL.State: Trying mac verification...\n"); 
    int length = sizeof(data) - hmac_size; 
    string digest = data[length ..]; 
    data = data[.. length - 1]; 
 
   /* NOTE: Perform some extra MAC operations, to avoid timing 
    *       attacks on the length of the padding. 
    * 
    *       This is to alleviate the "Lucky Thirteen" attack: 
    *       http://www.isg.rhul.ac.uk/tls/TLStiming.pdf 
    * 
    * NB: This is not needed in encrypt-then-mac mode, since we 
    *     always MAC the entire block. 
    */ 
    int block_size = mac->block_size(); 
    string pad_string = "\0"*block_size; 
    string junk = pad_string[<padding-1..]; 
    if (!((sizeof(data) + 
           mac->hash_header_size - session->cipher_spec->hash_size) % 
          block_size ) || 
        !(padding % block_size)) { 
      // We're at the edge of a MAC block, so we need to 
      // pad junk with an extra MAC block of data. 
      junk += pad_string; 
    } 
    junk = mac->hash_raw(junk); 
 
    // Set decrypted data without HMAC. 
    fail = fail || [object(Alert)]packet->set_compressed(data); 
 
    if (digest != mac->hash_packet(packet, seq_num)[..hmac_size-1]) 
      { 
        SSL3_DEBUG_MSG("Failed MAC-verification!!\n"); 
        SSL3_DEBUG_CRYPT_MSG("Expected digest: %O\n" 
                             "Calculated digest: %O\n" 
                             "Seqence number: %O\n", 
                             digest, mac->hash_packet(packet, seq_num), 
                             seq_num); 
        fail = fail || alert(ALERT_fatal, ALERT_bad_record_mac, 
                             "Bad MAC.\n"); 
      } 
    seq_num++; 
  } 
  else 
  { 
    // Set decrypted data. 
    fail = fail || [object(Alert)]packet->set_compressed(data); 
  } 
 
  if (compress) 
  { 
    SSL3_DEBUG_CRYPT_MSG("SSL.State: Trying decompression...\n"); 
    data = compress(data); 
    if (!data) 
      fail = fail || alert(ALERT_fatal, ALERT_unexpected_message, 
                           "Invalid compression.\n"); 
 
    // Set uncompressed data 
    fail = fail || [object(Alert)]packet->set_plaintext(data); 
  } 
 
  return fail || packet; 
} 
 
//! Encrypts a packet (including deflating and MAC-generation). 
Alert|Packet encrypt_packet(Packet packet, Context ctx) 
{ 
  ProtocolVersion version = packet->protocol_version; 
  string data = packet->fragment; 
  string digest; 
  Alert res; 
 
  if (compress) 
  { 
    // RFC 5246 6.2.2. states that data growth must be at most 1024 
    // bytes. Since zlib doesn't do that, and no other implementation 
    // is defined, don't bother checking. 
    data = compress(data); 
 
    // Set compressed data. 
    res = [object(Alert)]packet->set_compressed(data); 
    if(res) return res; 
  } 
 
  int hmac_size = mac && (session->truncated_hmac ? 10 : 
                          session->cipher_spec?->hash_size); 
 
  if (mac && !session->encrypt_then_mac) { 
    digest = mac->hash_packet(packet, seq_num)[..hmac_size-1]; 
    hmac_size = 0; 
  } else 
    digest = ""; 
 
  if (crypt) 
  { 
    SSL3_DEBUG_CRYPT_MSG("SSL.State: Encrypting message #%d: %O.\n", 
                         seq_num, data); 
 
    switch(session->cipher_spec->cipher_type) { 
    case CIPHER_stream: 
      data = crypt->crypt(data + digest); 
      break; 
    case CIPHER_block: 
      if(version == PROTOCOL_SSL_3_0) { 
        data = crypt->crypt(data + digest); 
        data += crypt->pad(Crypto.PAD_SSL); 
      } else if (version >= PROTOCOL_TLS_1_0) { 
        if (tls_iv) { 
          // RFC 4346 6.2.3.2.2: 
          // Generate a cryptographically strong random number R of length 
          // CipherSpec.block_length and prepend it to the plaintext prior 
          // to encryption. 
          string iv = ctx->random(tls_iv); 
          crypt->set_iv(iv); 
          data = iv + crypt->crypt(data) + crypt->crypt(digest) + crypt->pad(Crypto.PAD_TLS); 
        } else { 
          data = crypt->crypt(data) + crypt->crypt(digest) + crypt->pad(Crypto.PAD_TLS); 
        } 
      } 
      break; 
    case CIPHER_aead: 
      // FIXME: Do we need to pay attention to threads here? 
      string explicit_iv = ""; 
      string iv; 
      if (session->cipher_spec->explicit_iv_size) { 
        // RFC 5288 3: 
        // The nonce_explicit MAY be the 64-bit sequence number. 
        // 
        explicit_iv = sprintf("%*c", session->cipher_spec->explicit_iv_size, 
                              seq_num); 
        iv = salt + explicit_iv; 
      } else { 
        // Draft ChaCha20-Poly1305 5: 
        //   When used in TLS, the "record_iv_length" is zero and the nonce is 
        //   the sequence number for the record, as an 8-byte, big-endian 
        //   number. 
        iv = sprintf("%s%*c", salt, crypt->iv_size() - sizeof(salt), seq_num); 
      } 
      SSL3_DEBUG_CRYPT_MSG("SSL.State: AEAD IV: %O.\n", iv); 
      crypt->set_iv(iv); 
      string auth_data; 
      if (version >= PROTOCOL_TLS_1_3) { 
        auth_data = sprintf("%8c%c%2c", 
                            seq_num, packet->content_type, version); 
      } else { 
        auth_data = sprintf("%8c%c%2c%2c", 
                            seq_num, packet->content_type, 
                            version, sizeof(data)); 
      } 
 
      SSL3_DEBUG_CRYPT_MSG("SSL.State: AEAD auth data: %O.\n", auth_data); 
      crypt->update(auth_data); 
      data = explicit_iv + crypt->crypt(data) + crypt->digest(); 
      break; 
    } 
  } 
  else 
    data += digest; 
 
  // Set encrypted data. 
  res = [object(Alert)]packet->set_encrypted(data); 
  if(res) return res; 
 
  if (hmac_size) { 
    // Encrypt-then-MAC mode. 
    data += mac->hash_packet(packet, seq_num)[..hmac_size-1]; 
 
    // Set HMAC protected data. 
    res = [object(Alert)]packet->set_encrypted(data); 
    if(res) return res; 
  } 
 
  seq_num++; 
  return packet; 
}