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-rw-r--r--srtp/CryptoContextCtrl.cpp408
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diff --git a/srtp/CryptoContextCtrl.cpp b/srtp/CryptoContextCtrl.cpp
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+/*
+ 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:
+ */
+
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