#include "SrtpStream.h" #include <android/log.h> #include <unistd.h> #define AES_BLOCK_SIZE 16 #define TAG "SrtpStream" SrtpStream::SrtpStream(SrtpStreamParameters *parameters) : parameters(parameters) {} SrtpStream::~SrtpStream() { if (parameters != NULL) { delete parameters; } } int SrtpStream::init() { if (AES_set_encrypt_key(parameters->cipherKey, SRTP_AES_KEY_SIZE * 8, &key) != 0) { __android_log_print(ANDROID_LOG_WARN, TAG, "Failed to set AES key!"); return -1; } return 0; } void SrtpStream::setIv(int64_t logicalSequence, uint32_t ssrc, uint8_t *salt, uint8_t *iv) { memset(iv, 0, AES_BLOCK_SIZE); memcpy(iv, salt, SRTP_SALT_SIZE); iv[6] ^= (uint8_t)(ssrc >> 8); iv[7] ^= (uint8_t)(ssrc); iv[8] ^= (uint8_t)(logicalSequence >> 40); iv[9] ^= (uint8_t)(logicalSequence >> 32); iv[10] ^= (uint8_t)(logicalSequence >> 24); iv[11] ^= (uint8_t)(logicalSequence >> 16); iv[12] ^= (uint8_t)(logicalSequence >> 8); iv[13] ^= (uint8_t)(logicalSequence); } int SrtpStream::decrypt(RtpPacket &packet, int64_t logicalSequence) { uint8_t iv[AES_BLOCK_SIZE]; uint8_t ecount[AES_BLOCK_SIZE]; uint8_t ourMac[SRTP_MAC_SIZE]; uint32_t num = 0; uint32_t digest = 0; setIv(logicalSequence, packet.getSsrc(), parameters->salt, iv); memset(ecount, 0, sizeof(ecount)); if (packet.getPayloadLen() < (SRTP_MAC_SIZE + 1)) { __android_log_print(ANDROID_LOG_WARN, TAG, "Packet shorter than MAC!"); return -1; } HMAC(EVP_sha1(), parameters->macKey, SRTP_MAC_KEY_SIZE, (uint8_t*)packet.getSerializedPacket(), packet.getSerializedPacketLen() - SRTP_MAC_SIZE, ourMac, &digest); if (memcmp(ourMac, packet.getSerializedPacket() + packet.getSerializedPacketLen() - SRTP_MAC_SIZE, SRTP_MAC_SIZE) != 0) { __android_log_print(ANDROID_LOG_WARN, TAG, "MAC comparison failed!"); return -1; } packet.setPayloadLen(packet.getPayloadLen() - SRTP_MAC_SIZE); AES_ctr128_encrypt((uint8_t*)packet.getPayload(), (uint8_t*)packet.getPayload(), packet.getPayloadLen(), &key, iv, ecount, &num); return 0; } int SrtpStream::encrypt(RtpPacket &packet, int64_t logicalSequence) { uint8_t iv[AES_BLOCK_SIZE]; uint8_t ecount[AES_BLOCK_SIZE]; uint32_t num = 0; uint32_t digest = 0; setIv(logicalSequence, packet.getSsrc(), parameters->salt, iv); memset(ecount, 0, sizeof(ecount)); AES_ctr128_encrypt((uint8_t*)packet.getPayload(), (uint8_t*)packet.getPayload(), packet.getPayloadLen(), &key, iv, ecount, &num); HMAC(EVP_sha1(), parameters->macKey, SRTP_MAC_KEY_SIZE, (uint8_t*)packet.getSerializedPacket(), packet.getSerializedPacketLen(), (uint8_t*)packet.getSerializedPacket() + packet.getSerializedPacketLen(), &digest); packet.setPayloadLen(packet.getPayloadLen() + SRTP_MAC_SIZE); return 0; }