mediaSoup 源码分析-srtp操作

srtp操作还是比较简单的

#srtp sesssion创建

	SrtpSession::SrtpSession(Type type, Profile profile, uint8_t* key, size_t keyLen)
	{
		MS_TRACE();

		srtp_policy_t policy; // NOLINT(cppcoreguidelines-pro-type-member-init)

		// Set all policy fields to 0.
		std::memset(&policy, 0, sizeof(srtp_policy_t));

		switch (profile)
		{
			case Profile::AES_CM_128_HMAC_SHA1_80:
			{
				srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(&policy.rtp);
				srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(&policy.rtcp);

				break;
			}

			case Profile::AES_CM_128_HMAC_SHA1_32:
			{
				srtp_crypto_policy_set_aes_cm_128_hmac_sha1_32(&policy.rtp);
				// NOTE: Must be 80 for RTCP.
				srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(&policy.rtcp);

				break;
			}

			case Profile::AEAD_AES_256_GCM:
			{
				srtp_crypto_policy_set_aes_gcm_256_16_auth(&policy.rtp);
				srtp_crypto_policy_set_aes_gcm_256_16_auth(&policy.rtcp);

				break;
			}

			case Profile::AEAD_AES_128_GCM:
			{
				srtp_crypto_policy_set_aes_gcm_128_16_auth(&policy.rtp);
				srtp_crypto_policy_set_aes_gcm_128_16_auth(&policy.rtcp);

				break;
			}

			default:
			{
				MS_ABORT("unknown SRTP profile");
			}
		}

		MS_ASSERT(
		  (int)keyLen == policy.rtp.cipher_key_len,
		  "given keyLen does not match policy.rtp.cipher_keyLen");

		switch (type)
		{
			case Type::INBOUND:
				policy.ssrc.type = ssrc_any_inbound;
				break;

			case Type::OUTBOUND:
				policy.ssrc.type = ssrc_any_outbound;
				break;
		}

		policy.ssrc.value = 0;
		policy.key        = key;
		// Required for sending RTP retransmission without RTX.
		policy.allow_repeat_tx = 1;
		policy.window_size     = 1024;
		policy.next            = nullptr;

		// Set the SRTP session.
		srtp_err_status_t err = srtp_create(&this->session, &policy);

		if (DepLibSRTP::IsError(err))
			MS_THROW_ERROR("srtp_create() failed: %s", DepLibSRTP::GetErrorString(err));
	}

#加解密rtp

bool SrtpSession::EncryptRtp(const uint8_t** data, size_t* len)
	{
		MS_TRACE();

		// Ensure that the resulting SRTP packet fits into the encrypt buffer.
		if (*len + SRTP_MAX_TRAILER_LEN > EncryptBufferSize)
		{
			MS_WARN_TAG(srtp, "cannot encrypt RTP packet, size too big (%zu bytes)", *len);

			return false;
		}

		std::memcpy(EncryptBuffer, *data, *len);

		srtp_err_status_t err =
		  srtp_protect(this->session, (void*)EncryptBuffer, reinterpret_cast(len));

		if (DepLibSRTP::IsError(err))
		{
			MS_WARN_TAG(srtp, "srtp_protect() failed: %s", DepLibSRTP::GetErrorString(err));

			return false;
		}

		// Update the given data pointer.
		*data = (const uint8_t*)EncryptBuffer;

		return true;
	}

	bool SrtpSession::DecryptSrtp(const uint8_t* data, size_t* len)
	{
		MS_TRACE();

		srtp_err_status_t err = srtp_unprotect(this->session, (void*)data, reinterpret_cast(len));

		if (DepLibSRTP::IsError(err))
		{
			MS_DEBUG_TAG(srtp, "srtp_unprotect() failed: %s", DepLibSRTP::GetErrorString(err));

			return false;
		}

		return true;
	}

#加解密rtcp

	bool SrtpSession::EncryptRtcp(const uint8_t** data, size_t* len)
	{
		MS_TRACE();

		// Ensure that the resulting SRTCP packet fits into the encrypt buffer.
		if (*len + SRTP_MAX_TRAILER_LEN > EncryptBufferSize)
		{
			MS_WARN_TAG(srtp, "cannot encrypt RTCP packet, size too big (%zu bytes)", *len);

			return false;
		}

		std::memcpy(EncryptBuffer, *data, *len);

		srtp_err_status_t err =
		  srtp_protect_rtcp(this->session, (void*)EncryptBuffer, reinterpret_cast(len));

		if (DepLibSRTP::IsError(err))
		{
			MS_WARN_TAG(srtp, "srtp_protect_rtcp() failed: %s", DepLibSRTP::GetErrorString(err));

			return false;
		}

		// Update the given data pointer.
		*data = (const uint8_t*)EncryptBuffer;

		return true;
	}

	bool SrtpSession::DecryptSrtcp(const uint8_t* data, size_t* len)
	{
		MS_TRACE();

		srtp_err_status_t err =
		  srtp_unprotect_rtcp(this->session, (void*)data, reinterpret_cast(len));

		if (DepLibSRTP::IsError(err))
		{
			MS_DEBUG_TAG(srtp, "srtp_unprotect_rtcp() failed: %s", DepLibSRTP::GetErrorString(err));

			return false;
		}

		return true;
	}