| /* |
| Copyright (C) 2004-2006 the Minisip Team |
| |
| This library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| This library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with this library; if not, write to the Free Software |
| Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| */ |
| |
| /* Copyright (C) 2004-2012 |
| * |
| * Authors: Israel Abad <i_abad@terra.es> |
| * Erik Eliasson <eliasson@it.kth.se> |
| * Johan Bilien <jobi@via.ecp.fr> |
| * Joachim Orrblad <joachim@orrblad.com> |
| * Werner Dittmann <Werner.Dittmann@t-online.de> |
| */ |
| |
| #include <string.h> |
| #include <arpa/inet.h> |
| #include <stdio.h> |
| |
| #include <CryptoContextCtrl.h> |
| #include <CryptoContext.h> |
| |
| #include <crypto/hmac.h> |
| #include <crypto/macSkein.h> |
| |
| |
| CryptoContextCtrl::CryptoContextCtrl(uint32_t ssrc, |
| const int32_t ealg, |
| const int32_t aalg, |
| uint8_t* master_key, |
| int32_t master_key_length, |
| uint8_t* master_salt, |
| int32_t master_salt_length, |
| int32_t ekeyl, |
| int32_t akeyl, |
| int32_t skeyl, |
| int32_t tagLength): |
| ssrcCtx(ssrc),using_mki(false),mkiLength(0),mki(NULL), |
| replay_window(0), macCtx(NULL), cipher(NULL), f8Cipher(NULL) |
| { |
| this->ealg = ealg; |
| this->aalg = aalg; |
| this->ekeyl = ekeyl; |
| this->akeyl = akeyl; |
| this->skeyl = skeyl; |
| |
| this->master_key_length = master_key_length; |
| this->master_key = new uint8_t[master_key_length]; |
| memcpy(this->master_key, master_key, master_key_length); |
| |
| this->master_salt_length = master_salt_length; |
| this->master_salt = new uint8_t[master_salt_length]; |
| memcpy(this->master_salt, master_salt, master_salt_length); |
| |
| switch (ealg) { |
| case SrtpEncryptionNull: |
| n_e = 0; |
| k_e = NULL; |
| n_s = 0; |
| k_s = NULL; |
| break; |
| |
| case SrtpEncryptionTWOF8: |
| f8Cipher = new SrtpSymCrypto(SrtpEncryptionTWOF8); |
| |
| case SrtpEncryptionTWOCM: |
| n_e = ekeyl; |
| k_e = new uint8_t[n_e]; |
| n_s = skeyl; |
| k_s = new uint8_t[n_s]; |
| cipher = new SrtpSymCrypto(SrtpEncryptionTWOCM); |
| break; |
| |
| case SrtpEncryptionAESF8: |
| f8Cipher = new SrtpSymCrypto(SrtpEncryptionAESF8); |
| |
| case SrtpEncryptionAESCM: |
| n_e = ekeyl; |
| k_e = new uint8_t[n_e]; |
| n_s = skeyl; |
| k_s = new uint8_t[n_s]; |
| cipher = new SrtpSymCrypto(SrtpEncryptionAESCM); |
| break; |
| } |
| |
| switch (aalg) { |
| case SrtpAuthenticationNull: |
| n_a = 0; |
| k_a = NULL; |
| this->tagLength = 0; |
| break; |
| |
| case SrtpAuthenticationSha1Hmac: |
| case SrtpAuthenticationSkeinHmac: |
| n_a = akeyl; |
| k_a = new uint8_t[n_a]; |
| this->tagLength = tagLength; |
| break; |
| } |
| } |
| |
| CryptoContextCtrl::~CryptoContextCtrl(){ |
| |
| if (mki) |
| delete [] mki; |
| |
| if (master_key_length > 0) { |
| memset(master_key, 0, master_key_length); |
| master_key_length = 0; |
| delete [] master_key; |
| } |
| if (master_salt_length > 0) { |
| memset(master_salt, 0, master_salt_length); |
| master_salt_length = 0; |
| delete [] master_salt; |
| } |
| if (n_e > 0) { |
| memset(k_e, 0, n_e); |
| n_e = 0; |
| delete [] k_e; |
| } |
| if (n_s > 0) { |
| memset(k_s, 0, n_s); |
| n_s = 0; |
| delete [] k_s; |
| } |
| if (n_a > 0) { |
| n_a = 0; |
| memset(k_a, 0, n_a); |
| delete [] k_a; |
| } |
| if (cipher != NULL) { |
| delete cipher; |
| cipher = NULL; |
| } |
| if (f8Cipher != NULL) { |
| delete f8Cipher; |
| f8Cipher = NULL; |
| } |
| if (macCtx != NULL) { |
| switch(aalg) { |
| case SrtpAuthenticationSha1Hmac: |
| freeSha1HmacContext(macCtx); |
| break; |
| |
| case SrtpAuthenticationSkeinHmac: |
| freeSkeinMacContext(macCtx); |
| break; |
| } |
| } |
| ealg = SrtpEncryptionNull; |
| aalg = SrtpAuthenticationNull; |
| } |
| |
| void CryptoContextCtrl::srtcpEncrypt( uint8_t* rtp, int32_t len, uint64_t index, uint32_t ssrc ) |
| { |
| if (ealg == SrtpEncryptionNull) { |
| return; |
| } |
| if (ealg == SrtpEncryptionAESCM || ealg == SrtpEncryptionTWOCM) { |
| |
| /* Compute the CM IV (refer to chapter 4.1.1 in RFC 3711): |
| * |
| * k_s XX XX XX XX XX XX XX XX XX XX XX XX XX XX |
| * SSRC XX XX XX XX |
| * index XX XX XX XX |
| * ------------------------------------------------------XOR |
| * IV XX XX XX XX XX XX XX XX XX XX XX XX XX XX 00 00 |
| * 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 |
| */ |
| unsigned char iv[16]; |
| |
| iv[0] = k_s[0]; |
| iv[1] = k_s[1]; |
| iv[2] = k_s[2]; |
| iv[3] = k_s[3]; |
| |
| // The shifts transform the ssrc and index into network order |
| iv[4] = ((ssrc >> 24) & 0xff) ^ k_s[4]; |
| iv[5] = ((ssrc >> 16) & 0xff) ^ k_s[5]; |
| iv[6] = ((ssrc >> 8) & 0xff) ^ k_s[6]; |
| iv[7] = (ssrc & 0xff) ^ k_s[7]; |
| |
| iv[8] = k_s[8]; |
| iv[9] = k_s[9]; |
| |
| iv[10] = ((index >> 24) & 0xff) ^ k_s[10]; |
| iv[11] = ((index >> 16) & 0xff) ^ k_s[11]; |
| iv[12] = ((index >> 8) & 0xff) ^ k_s[12]; |
| iv[13] = (index & 0xff) ^ k_s[13]; |
| |
| iv[14] = iv[15] = 0; |
| |
| cipher->ctr_encrypt(rtp, len, iv); |
| } |
| |
| if (ealg == SrtpEncryptionAESF8 || ealg == SrtpEncryptionTWOF8) { |
| |
| unsigned char iv[16]; |
| |
| // 4 bytes of the iv are zero |
| // the first byte of the RTP header is not used. |
| iv[0] = 0; |
| iv[1] = 0; |
| iv[2] = 0; |
| iv[3] = 0; |
| |
| // Need the encryption flag |
| index = index | 0x80000000; |
| |
| // set the index and the encrypt flag in network order into IV |
| iv[4] = index >> 24; |
| iv[5] = index >> 16; |
| iv[6] = index >> 8; |
| iv[7] = index; |
| |
| // The fixed header follows and fills the rest of the IV |
| memcpy(iv+8, rtp, 8); |
| |
| cipher->f8_encrypt(rtp, len, iv, f8Cipher); |
| } |
| } |
| |
| /* Warning: tag must have been initialized */ |
| void CryptoContextCtrl::srtcpAuthenticate(uint8_t* rtp, int32_t len, uint32_t index, uint8_t* tag ) |
| { |
| if (aalg == SrtpAuthenticationNull) { |
| return; |
| } |
| int32_t macL; |
| |
| unsigned char temp[20]; |
| const unsigned char* chunks[3]; |
| unsigned int chunkLength[3]; |
| uint32_t beIndex = htonl(index); |
| |
| chunks[0] = rtp; |
| chunkLength[0] = len; |
| |
| chunks[1] = (unsigned char *)&beIndex; |
| chunkLength[1] = 4; |
| chunks[2] = NULL; |
| |
| switch (aalg) { |
| case SrtpAuthenticationSha1Hmac: |
| hmacSha1Ctx(macCtx, |
| chunks, // data chunks to hash |
| chunkLength, // length of the data to hash |
| temp, &macL); |
| /* truncate the result */ |
| memcpy(tag, temp, getTagLength()); |
| break; |
| case SrtpAuthenticationSkeinHmac: |
| macSkeinCtx(macCtx, |
| chunks, // data chunks to hash |
| chunkLength, // length of the data to hash |
| temp); |
| /* truncate the result */ |
| memcpy(tag, temp, getTagLength()); |
| break; |
| } |
| } |
| |
| /* used by the key derivation method */ |
| static void computeIv(unsigned char* iv, uint8_t label, uint8_t* master_salt) |
| { |
| //printf( "Key_ID: %llx\n", key_id ); |
| |
| /* compute the IV |
| key_id: XX XX XX XX XX XX XX |
| master_salt: XX XX XX XX XX XX XX XX XX XX XX XX XX XX |
| ------------------------------------------------------------ XOR |
| IV: XX XX XX XX XX XX XX XX XX XX XX XX XX XX 00 00 |
| */ |
| |
| memcpy(iv, master_salt, 14); |
| iv[7] ^= label; |
| |
| iv[14] = iv[15] = 0; |
| } |
| |
| /* Derives the srtp session keys from the master key */ |
| void CryptoContextCtrl::deriveSrtcpKeys() |
| { |
| uint8_t iv[16]; |
| |
| // prepare AES cipher to compute derived keys. |
| cipher->setNewKey(master_key, master_key_length); |
| memset(master_key, 0, master_key_length); |
| |
| // compute the session encryption key |
| uint8_t label = 3; |
| computeIv(iv, label, master_salt); |
| cipher->get_ctr_cipher_stream(k_e, n_e, iv); |
| |
| // compute the session authentication key |
| label = 4; |
| computeIv(iv, label, master_salt); |
| cipher->get_ctr_cipher_stream(k_a, n_a, iv); |
| |
| // Initialize MAC context with the derived key |
| switch (aalg) { |
| case SrtpAuthenticationSha1Hmac: |
| macCtx = createSha1HmacContext(k_a, n_a); |
| break; |
| case SrtpAuthenticationSkeinHmac: |
| // Skein MAC uses number of bits as MAC size, not just bytes |
| macCtx = createSkeinMacContext(k_a, n_a, tagLength*8, Skein512); |
| break; |
| } |
| memset(k_a, 0, n_a); |
| |
| // compute the session salt |
| label = 5; |
| computeIv(iv, label, master_salt); |
| cipher->get_ctr_cipher_stream(k_s, n_s, iv); |
| memset(master_salt, 0, master_salt_length); |
| |
| // as last step prepare AES cipher with derived key. |
| cipher->setNewKey(k_e, n_e); |
| if (f8Cipher != NULL) |
| cipher->f8_deriveForIV(f8Cipher, k_e, n_e, k_s, n_s); |
| memset(k_e, 0, n_e); |
| } |
| |
| bool CryptoContextCtrl::checkReplay( uint32_t index ) |
| { |
| if ( aalg == SrtpAuthenticationNull && ealg == SrtpEncryptionNull ) { |
| /* No security policy, don't use the replay protection */ |
| return true; |
| } |
| |
| int64_t delta = s_l - index; |
| if (delta > 0) { |
| /* Packet not yet received*/ |
| return true; |
| } |
| else { |
| if( -delta > REPLAY_WINDOW_SIZE ) { |
| /* Packet too old */ |
| return false; |
| } |
| else { |
| if((replay_window >> (-delta)) & 0x1) { |
| /* Packet already received ! */ |
| return false; |
| } |
| else { |
| /* Packet not yet received */ |
| return true; |
| } |
| } |
| } |
| } |
| |
| void CryptoContextCtrl::update(uint32_t index) |
| { |
| int64_t delta = index - s_l; |
| |
| /* update the replay bitmask */ |
| if( delta > 0 ){ |
| replay_window = replay_window << delta; |
| replay_window |= 1; |
| } |
| else { |
| replay_window |= ( 1 << delta ); |
| } |
| s_l = index; |
| } |
| |
| CryptoContextCtrl* CryptoContextCtrl::newCryptoContextForSSRC(uint32_t ssrc) |
| { |
| CryptoContextCtrl* pcc = new CryptoContextCtrl( |
| ssrc, |
| this->ealg, // encryption algo |
| this->aalg, // authentication algo |
| this->master_key, // Master Key |
| this->master_key_length, // Master Key length |
| this->master_salt, // Master Salt |
| this->master_salt_length, // Master Salt length |
| this->ekeyl, // encryption keyl |
| this->akeyl, // authentication key len |
| this->skeyl, // session salt len |
| this->tagLength); // authentication tag len |
| |
| return pcc; |
| } |
| |
| /** EMACS ** |
| * Local variables: |
| * mode: c++ |
| * c-default-style: ellemtel |
| * c-basic-offset: 4 |
| * End: |
| */ |
| |