Function openssl_HMACsha256

src/brpc/policy/rtmp_protocol.cpp:148–178

Modified from code in SRS2 (src/protocol/srs_rtmp_handshake.cpp:94)

// Modified from code in SRS2 (src/protocol/srs_rtmp_handshake.cpp:94)
int openssl_HMACsha256(const void* key, int key_size,
                       const void* data, int data_size, void* digest) {
    if (NULL == EVP_sha256) {
        LOG_ONCE(ERROR) << "Fail to find EVP_sha256, fall back to simple handshaking";
        return -1;
    }
    unsigned int digest_size = 0;
    unsigned char* temp_digest = (unsigned char*)digest;
    if (key == NULL) {
        // NOTE: first parameter of EVP_Digest in older openssl is void*.
        if (EVP_Digest(const_cast<void*>(data), data_size, temp_digest,
                       &digest_size, EVP_sha256(), NULL) < 0) {
            LOG(ERROR) << "Fail to EVP_Digest";
            return -1;
        }
    } else {
        // Note: following code uses HMAC_CTX previously which is ABI
        // inconsistent in different version of openssl.
        if (HMAC(EVP_sha256(), key, key_size,
                 (const unsigned char*) data, data_size,
                 temp_digest, &digest_size) == NULL) {
            LOG(ERROR) << "Fail to HMAC";
            return -1;
        }
    }
    if (digest_size != 32) {
        LOG(ERROR) << "digest_size=" << digest_size << " of sha256 is not 32";
        return -1;
    }
    return 0;
}

// 68bytes FMS key for signing the sever packets.
static const uint8_t GenuineFMSKey[] = {