Index: talk/media/base/rtputils.cc |
diff --git a/talk/media/base/rtputils.cc b/talk/media/base/rtputils.cc |
index 400cc1d69b680bd806ac58d69b5a63189ffa4ed6..422a85884c5f4e164c0c1c404b99e73bb9f88af2 100644 |
--- a/talk/media/base/rtputils.cc |
+++ b/talk/media/base/rtputils.cc |
@@ -27,6 +27,13 @@ |
#include "talk/media/base/rtputils.h" |
+#include "talk/media/base/turnutils.h" |
+// PacketTimeUpdateParams is defined in asyncpacketsocket.h. |
+// TODO(sergeyu): Find more appropriate place for PacketTimeUpdateParams. |
+#include "webrtc/base/asyncpacketsocket.h" |
+#include "webrtc/base/checks.h" |
+#include "webrtc/base/messagedigest.h" |
+ |
namespace cricket { |
static const uint8_t kRtpVersion = 2; |
@@ -36,6 +43,95 @@ static const size_t kRtpSeqNumOffset = 2; |
static const size_t kRtpTimestampOffset = 4; |
static const size_t kRtpSsrcOffset = 8; |
static const size_t kRtcpPayloadTypeOffset = 1; |
+static const size_t kRtpExtensionHeaderLen = 4; |
+static const size_t kAbsSendTimeExtensionLen = 3; |
+static const size_t kOneByteExtensionHeaderLen = 1; |
+ |
+namespace { |
+ |
+// Fake auth tag written by the sender when external authentication is enabled. |
+// HMAC in packet will be compared against this value before updating packet |
+// with actual HMAC value. |
+static const uint8_t kFakeAuthTag[10] = { |
+ 0xba, 0xdd, 0xba, 0xdd, 0xba, 0xdd, 0xba, 0xdd, 0xba, 0xdd |
+}; |
+ |
+void UpdateAbsSendTimeExtensionValue(uint8_t* extension_data, |
+ size_t length, |
+ uint64_t time_us) { |
+ // Absolute send time in RTP streams. |
+ // |
+ // The absolute send time is signaled to the receiver in-band using the |
+ // general mechanism for RTP header extensions [RFC5285]. The payload |
+ // of this extension (the transmitted value) is a 24-bit unsigned integer |
+ // containing the sender's current time in seconds as a fixed point number |
+ // with 18 bits fractional part. |
+ // |
+ // The form of the absolute send time extension block: |
+ // |
+ // 0 1 2 3 |
+ // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 |
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+ // | ID | len=2 | absolute send time | |
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+ if (length != kAbsSendTimeExtensionLen) { |
+ RTC_NOTREACHED(); |
+ return; |
+ } |
+ |
+ // Convert microseconds to a 6.18 fixed point value in seconds. |
+ uint32_t send_time = ((time_us << 18) / 1000000) & 0x00FFFFFF; |
+ extension_data[0] = static_cast<uint8_t>(send_time >> 16); |
+ extension_data[1] = static_cast<uint8_t>(send_time >> 8); |
+ extension_data[2] = static_cast<uint8_t>(send_time); |
+} |
+ |
+// Assumes |length| is actual packet length + tag length. Updates HMAC at end of |
+// the RTP packet. |
+void UpdateRtpAuthTag(uint8_t* rtp, |
+ size_t length, |
+ const rtc::PacketTimeUpdateParams& packet_time_params) { |
+ // If there is no key, return. |
+ if (packet_time_params.srtp_auth_key.empty()) { |
+ return; |
+ } |
+ |
+ size_t tag_length = packet_time_params.srtp_auth_tag_len; |
+ |
+ // ROC (rollover counter) is at the beginning of the auth tag. |
+ const size_t kRocLength = 4; |
+ if (tag_length < kRocLength || tag_length > length) { |
+ RTC_NOTREACHED(); |
+ return; |
+ } |
+ |
+ uint8_t* auth_tag = rtp + (length - tag_length); |
+ |
+ // We should have a fake HMAC value @ auth_tag. |
+ RTC_DCHECK_EQ(0, memcmp(auth_tag, kFakeAuthTag, tag_length)); |
+ |
+ // Copy ROC after end of rtp packet. |
+ memcpy(auth_tag, &packet_time_params.srtp_packet_index, kRocLength); |
+ // Authentication of a RTP packet will have RTP packet + ROC size. |
+ size_t auth_required_length = length - tag_length + kRocLength; |
+ |
+ uint8_t output[64]; |
+ size_t result = rtc::ComputeHmac( |
+ rtc::DIGEST_SHA_1, &packet_time_params.srtp_auth_key[0], |
+ packet_time_params.srtp_auth_key.size(), rtp, |
+ auth_required_length, output, sizeof(output)); |
+ |
+ if (result < tag_length) { |
+ RTC_NOTREACHED(); |
+ return; |
+ } |
+ |
+ // Copy HMAC from output to packet. This is required as auth tag length |
+ // may not be equal to the actual HMAC length. |
+ memcpy(auth_tag, output, tag_length); |
+} |
+ |
+} |
bool GetUint8(const void* data, size_t offset, int* value) { |
if (!data || !value) { |
@@ -200,4 +296,186 @@ bool IsValidRtpPayloadType(int payload_type) { |
return payload_type >= 0 && payload_type <= 127; |
} |
+bool ValidateRtpHeader(const uint8_t* rtp, |
+ size_t length, |
+ size_t* header_length) { |
+ if (header_length) { |
+ *header_length = 0; |
+ } |
+ |
+ if (length < kMinRtpPacketLen) { |
+ return false; |
+ } |
+ |
+ size_t cc_count = rtp[0] & 0x0F; |
+ size_t header_length_without_extension = kMinRtpPacketLen + 4 * cc_count; |
+ if (header_length_without_extension > length) { |
+ return false; |
+ } |
+ |
+ // If extension bit is not set, we are done with header processing, as input |
+ // length is verified above. |
+ if (!(rtp[0] & 0x10)) { |
+ if (header_length) |
+ *header_length = header_length_without_extension; |
+ |
+ return true; |
+ } |
+ |
+ rtp += header_length_without_extension; |
+ |
+ if (header_length_without_extension + kRtpExtensionHeaderLen > length) { |
+ return false; |
+ } |
+ |
+ // Getting extension profile length. |
+ // Length is in 32 bit words. |
+ uint16_t extension_length_in_32bits = rtc::GetBE16(rtp + 2); |
+ size_t extension_length = extension_length_in_32bits * 4; |
+ |
+ size_t rtp_header_length = extension_length + |
+ header_length_without_extension + |
+ kRtpExtensionHeaderLen; |
+ |
+ // Verify input length against total header size. |
+ if (rtp_header_length > length) { |
+ return false; |
+ } |
+ |
+ if (header_length) { |
+ *header_length = rtp_header_length; |
+ } |
+ return true; |
+} |
+ |
+// ValidateRtpHeader() must be called before this method to make sure, we have |
+// a sane rtp packet. |
+bool UpdateRtpAbsSendTimeExtension(uint8_t* rtp, |
+ size_t length, |
+ int extension_id, |
+ uint64_t time_us) { |
+ // 0 1 2 3 |
+ // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 |
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+ // |V=2|P|X| CC |M| PT | sequence number | |
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+ // | timestamp | |
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+ // | synchronization source (SSRC) identifier | |
+ // +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ |
+ // | contributing source (CSRC) identifiers | |
+ // | .... | |
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+ |
+ // Return if extension bit is not set. |
+ if (!(rtp[0] & 0x10)) { |
+ return true; |
+ } |
+ |
+ size_t cc_count = rtp[0] & 0x0F; |
+ size_t header_length_without_extension = kMinRtpPacketLen + 4 * cc_count; |
+ |
+ rtp += header_length_without_extension; |
+ |
+ // Getting extension profile ID and length. |
+ uint16_t profile_id = rtc::GetBE16(rtp); |
+ // Length is in 32 bit words. |
+ uint16_t extension_length_in_32bits = rtc::GetBE16(rtp + 2); |
+ size_t extension_length = extension_length_in_32bits * 4; |
+ |
+ rtp += kRtpExtensionHeaderLen; // Moving past extension header. |
+ |
+ bool found = false; |
+ // WebRTC is using one byte header extension. |
+ // TODO(mallinath) - Handle two byte header extension. |
+ if (profile_id == 0xBEDE) { // OneByte extension header |
+ // 0 |
+ // 0 1 2 3 4 5 6 7 |
+ // +-+-+-+-+-+-+-+-+ |
+ // | ID |length | |
+ // +-+-+-+-+-+-+-+-+ |
+ |
+ // 0 1 2 3 |
+ // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 |
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+ // | 0xBE | 0xDE | length=3 | |
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+ // | ID | L=0 | data | ID | L=1 | data... |
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+ // ...data | 0 (pad) | 0 (pad) | ID | L=3 | |
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+ // | data | |
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+ const uint8_t* extension_start = rtp; |
+ const uint8_t* extension_end = extension_start + extension_length; |
+ |
+ while (rtp < extension_end) { |
+ const int id = (*rtp & 0xF0) >> 4; |
+ const size_t length = (*rtp & 0x0F) + 1; |
+ if (rtp + kOneByteExtensionHeaderLen + length > extension_end) { |
+ return false; |
+ } |
+ // The 4-bit length is the number minus one of data bytes of this header |
+ // extension element following the one-byte header. |
+ if (id == extension_id) { |
+ UpdateAbsSendTimeExtensionValue(rtp + kOneByteExtensionHeaderLen, |
+ length, time_us); |
+ found = true; |
+ break; |
+ } |
+ rtp += kOneByteExtensionHeaderLen + length; |
+ // Counting padding bytes. |
+ while ((rtp < extension_end) && (*rtp == 0)) { |
+ ++rtp; |
+ } |
+ } |
+ } |
+ return found; |
+} |
+ |
+bool ApplyPacketOptions(uint8_t* data, |
+ size_t length, |
+ const rtc::PacketTimeUpdateParams& packet_time_params, |
+ uint64_t time_us) { |
+ RTC_DCHECK(data); |
+ RTC_DCHECK(length); |
+ |
+ // if there is no valid |rtp_sendtime_extension_id| and |srtp_auth_key| in |
+ // PacketOptions, nothing to be updated in this packet. |
+ if (packet_time_params.rtp_sendtime_extension_id == -1 && |
+ packet_time_params.srtp_auth_key.empty()) { |
+ return true; |
+ } |
+ |
+ // If there is a srtp auth key present then the packet must be an RTP packet. |
+ // RTP packet may have been wrapped in a TURN Channel Data or TURN send |
+ // indication. |
+ size_t rtp_start_pos; |
+ size_t rtp_length; |
+ if (!UnwrapTurnPacket(data, length, &rtp_start_pos, &rtp_length)) { |
+ RTC_NOTREACHED(); |
+ return false; |
+ } |
+ |
+ // Making sure we have a valid RTP packet at the end. |
+ if (!IsRtpPacket(data + rtp_start_pos, rtp_length) || |
+ !ValidateRtpHeader(data + rtp_start_pos, rtp_length, nullptr)) { |
+ RTC_NOTREACHED(); |
+ return false; |
+ } |
+ |
+ uint8_t* start = data + rtp_start_pos; |
+ // If packet option has non default value (-1) for sendtime extension id, |
+ // then we should parse the rtp packet to update the timestamp. Otherwise |
+ // just calculate HMAC and update packet with it. |
+ if (packet_time_params.rtp_sendtime_extension_id != -1) { |
+ UpdateRtpAbsSendTimeExtension(start, rtp_length, |
+ packet_time_params.rtp_sendtime_extension_id, |
+ time_us); |
+ } |
+ |
+ UpdateRtpAuthTag(start, rtp_length, packet_time_params); |
+ return true; |
+} |
+ |
} // namespace cricket |