The Tor Browser: security/nss/lib/ssl/dtlscon.c@b8a032363ba2 (annotated)

security/nss/lib/ssl/dtlscon.c@b8a032363ba2 (annotated)

security/nss/lib/ssl/dtlscon.c

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 /*
  * DTLS Protocol
  */
 #include "ssl.h"
 #include "sslimpl.h"
 #include "sslproto.h"
 #ifndef PR_ARRAY_SIZE
 #define PR_ARRAY_SIZE(a) (sizeof(a)/sizeof((a)[0]))
 #endif
 static SECStatus dtls_TransmitMessageFlight(sslSocket *ss);
 static void dtls_RetransmitTimerExpiredCb(sslSocket *ss);
 static SECStatus dtls_SendSavedWriteData(sslSocket *ss);
 /* -28 adjusts for the IP/UDP header */
 static const PRUint16 COMMON_MTU_VALUES[] = {
 - 28,  /* Ethernet MTU */
 - 28,  /* IPv6 minimum MTU */
 - 28,   /* Common assumption */
 - 28    /* We're in serious trouble now */
 };
 #define DTLS_COOKIE_BYTES 32
 /* List copied from ssl3con.c:cipherSuites */
 static const ssl3CipherSuite nonDTLSSuites[] = {
 #ifndef NSS_DISABLE_ECC
     TLS_ECDHE_ECDSA_WITH_RC4_128_SHA,
     TLS_ECDHE_RSA_WITH_RC4_128_SHA,
 #endif /* NSS_DISABLE_ECC */
     TLS_DHE_DSS_WITH_RC4_128_SHA,
 #ifndef NSS_DISABLE_ECC
     TLS_ECDH_RSA_WITH_RC4_128_SHA,
     TLS_ECDH_ECDSA_WITH_RC4_128_SHA,
 #endif /* NSS_DISABLE_ECC */
     TLS_RSA_WITH_RC4_128_MD5,
     TLS_RSA_WITH_RC4_128_SHA,
     TLS_RSA_EXPORT1024_WITH_RC4_56_SHA,
     TLS_RSA_EXPORT_WITH_RC4_40_MD5,
 /* End of list marker */
 };
 /* Map back and forth between TLS and DTLS versions in wire format.
  * Mapping table is:
  *
  * TLS             DTLS
  * 1.1 (0302)      1.0 (feff)
  * 1.2 (0303)      1.2 (fefd)
  */
 SSL3ProtocolVersion
 dtls_TLSVersionToDTLSVersion(SSL3ProtocolVersion tlsv)
 {
     if (tlsv == SSL_LIBRARY_VERSION_TLS_1_1) {
         return SSL_LIBRARY_VERSION_DTLS_1_0_WIRE;
     }
     if (tlsv == SSL_LIBRARY_VERSION_TLS_1_2) {
         return SSL_LIBRARY_VERSION_DTLS_1_2_WIRE;
     }
     /* Anything other than TLS 1.1 or 1.2 is an error, so return
      * the invalid version 0xffff. */
     return 0xffff;
 }
 /* Map known DTLS versions to known TLS versions.
  * - Invalid versions (< 1.0) return a version of 0
  * - Versions > known return a version one higher than we know of
  * to accomodate a theoretically newer version */
 SSL3ProtocolVersion
 dtls_DTLSVersionToTLSVersion(SSL3ProtocolVersion dtlsv)
 {
     if (MSB(dtlsv) == 0xff) {
         return 0;
     }
     if (dtlsv == SSL_LIBRARY_VERSION_DTLS_1_0_WIRE) {
         return SSL_LIBRARY_VERSION_TLS_1_1;
     }
     if (dtlsv == SSL_LIBRARY_VERSION_DTLS_1_2_WIRE) {
         return SSL_LIBRARY_VERSION_TLS_1_2;
     }
     /* Return a fictional higher version than we know of */
     return SSL_LIBRARY_VERSION_TLS_1_2 + 1;
 }
 /* On this socket, Disable non-DTLS cipher suites in the argument's list */
 SECStatus
 ssl3_DisableNonDTLSSuites(sslSocket * ss)
 {
     const ssl3CipherSuite * suite;
     for (suite = nonDTLSSuites; *suite; ++suite) {
         SECStatus rv = ssl3_CipherPrefSet(ss, *suite, PR_FALSE);
         PORT_Assert(rv == SECSuccess); /* else is coding error */
     }
     return SECSuccess;
 }
 /* Allocate a DTLSQueuedMessage.
  *
  * Called from dtls_QueueMessage()
  */
 static DTLSQueuedMessage *
 dtls_AllocQueuedMessage(PRUint16 epoch, SSL3ContentType type,
                         const unsigned char *data, PRUint32 len)
 {
     DTLSQueuedMessage *msg = NULL;
     msg = PORT_ZAlloc(sizeof(DTLSQueuedMessage));
     if (!msg)
         return NULL;
     msg->data = PORT_Alloc(len);
     if (!msg->data) {
         PORT_Free(msg);
         return NULL;
     }
     PORT_Memcpy(msg->data, data, len);
     msg->len = len;
     msg->epoch = epoch;
     msg->type = type;
     return msg;
 }
 /*
  * Free a handshake message
  *
  * Called from dtls_FreeHandshakeMessages()
  */
 static void
 dtls_FreeHandshakeMessage(DTLSQueuedMessage *msg)
 {
     if (!msg)
         return;
     PORT_ZFree(msg->data, msg->len);
     PORT_Free(msg);
 }
 /*
  * Free a list of handshake messages
  *
  * Called from:
  *              dtls_HandleHandshake()
  *              ssl3_DestroySSL3Info()
  */
 void
 dtls_FreeHandshakeMessages(PRCList *list)
 {
     PRCList *cur_p;
     while (!PR_CLIST_IS_EMPTY(list)) {
         cur_p = PR_LIST_TAIL(list);
         PR_REMOVE_LINK(cur_p);
         dtls_FreeHandshakeMessage((DTLSQueuedMessage *)cur_p);
     }
 }
 /* Called only from ssl3_HandleRecord, for each (deciphered) DTLS record.
  * origBuf is the decrypted ssl record content and is expected to contain
  * complete handshake records
  * Caller must hold the handshake and RecvBuf locks.
  *
  * Note that this code uses msg_len for two purposes:
  *
  * (1) To pass the length to ssl3_HandleHandshakeMessage()
  * (2) To carry the length of a message currently being reassembled
  *
  * However, unlike ssl3_HandleHandshake(), it is not used to carry
  * the state of reassembly (i.e., whether one is in progress). That
  * is carried in recvdHighWater and recvdFragments.
  */
 #define OFFSET_BYTE(o) (o/8)
 #define OFFSET_MASK(o) (1 << (o%8))
 SECStatus
 dtls_HandleHandshake(sslSocket *ss, sslBuffer *origBuf)
 {
     /* XXX OK for now.
      * This doesn't work properly with asynchronous certificate validation.
      * because that returns a WOULDBLOCK error. The current DTLS
      * applications do not need asynchronous validation, but in the
      * future we will need to add this.
      */
     sslBuffer buf = *origBuf;
     SECStatus rv = SECSuccess;
     PORT_Assert(ss->opt.noLocks || ssl_HaveRecvBufLock(ss));
     PORT_Assert(ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss));
     while (buf.len > 0) {
         PRUint8 type;
         PRUint32 message_length;
         PRUint16 message_seq;
         PRUint32 fragment_offset;
         PRUint32 fragment_length;
         PRUint32 offset;
         if (buf.len < 12) {
             PORT_SetError(SSL_ERROR_RX_MALFORMED_HANDSHAKE);
             rv = SECFailure;
             break;
         }
         /* Parse the header */
         type = buf.buf[0];
         message_length = (buf.buf[1] << 16) | (buf.buf[2] << 8) | buf.buf[3];
         message_seq = (buf.buf[4] << 8) | buf.buf[5];
         fragment_offset = (buf.buf[6] << 16) | (buf.buf[7] << 8) | buf.buf[8];
         fragment_length = (buf.buf[9] << 16) | (buf.buf[10] << 8) | buf.buf[11];
 #define MAX_HANDSHAKE_MSG_LEN 0x1ffff   /* 128k - 1 */
         if (message_length > MAX_HANDSHAKE_MSG_LEN) {
             (void)ssl3_DecodeError(ss);
             PORT_SetError(SSL_ERROR_RX_RECORD_TOO_LONG);
             return SECFailure;
         }
 #undef MAX_HANDSHAKE_MSG_LEN
         buf.buf += 12;
         buf.len -= 12;
         /* This fragment must be complete */
         if (buf.len < fragment_length) {
             PORT_SetError(SSL_ERROR_RX_MALFORMED_HANDSHAKE);
             rv = SECFailure;
             break;
         }
         /* Sanity check the packet contents */
         if ((fragment_length + fragment_offset) > message_length) {
             PORT_SetError(SSL_ERROR_RX_MALFORMED_HANDSHAKE);
             rv = SECFailure;
             break;
         }
         /* There are three ways we could not be ready for this packet.
          *
          * 1. It's a partial next message.
          * 2. It's a partial or complete message beyond the next
          * 3. It's a message we've already seen
          *
          * If it's the complete next message we accept it right away.
          * This is the common case for short messages
          */
         if ((message_seq == ss->ssl3.hs.recvMessageSeq)
             && (fragment_offset == 0)
             && (fragment_length == message_length)) {
             /* Complete next message. Process immediately */
             ss->ssl3.hs.msg_type = (SSL3HandshakeType)type;
             ss->ssl3.hs.msg_len = message_length;
             /* At this point we are advancing our state machine, so
              * we can free our last flight of messages */
             dtls_FreeHandshakeMessages(&ss->ssl3.hs.lastMessageFlight);
             ss->ssl3.hs.recvdHighWater = -1;
             dtls_CancelTimer(ss);
             /* Reset the timer to the initial value if the retry counter
              * is 0, per Sec. 4.2.4.1 */
             if (ss->ssl3.hs.rtRetries == 0) {
                 ss->ssl3.hs.rtTimeoutMs = INITIAL_DTLS_TIMEOUT_MS;
             }
             rv = ssl3_HandleHandshakeMessage(ss, buf.buf, ss->ssl3.hs.msg_len);
             if (rv == SECFailure) {
                 /* Do not attempt to process rest of messages in this record */
                 break;
             }
         } else {
             if (message_seq < ss->ssl3.hs.recvMessageSeq) {
                 /* Case 3: we do an immediate retransmit if we're
                  * in a waiting state*/
                 if (ss->ssl3.hs.rtTimerCb == NULL) {
                     /* Ignore */
                 } else if (ss->ssl3.hs.rtTimerCb ==
                          dtls_RetransmitTimerExpiredCb) {
                     SSL_TRC(30, ("%d: SSL3[%d]: Retransmit detected",
                                  SSL_GETPID(), ss->fd));
                     /* Check to see if we retransmitted recently. If so,
                      * suppress the triggered retransmit. This avoids
                      * retransmit wars after packet loss.
                      * This is not in RFC 5346 but should be
                      */
                     if ((PR_IntervalNow() - ss->ssl3.hs.rtTimerStarted) >
                         (ss->ssl3.hs.rtTimeoutMs / 4)) {
                             SSL_TRC(30,
                             ("%d: SSL3[%d]: Shortcutting retransmit timer",
                             SSL_GETPID(), ss->fd));
                             /* Cancel the timer and call the CB,
                              * which re-arms the timer */
                             dtls_CancelTimer(ss);
                             dtls_RetransmitTimerExpiredCb(ss);
                             rv = SECSuccess;
                             break;
                         } else {
                             SSL_TRC(30,
                             ("%d: SSL3[%d]: We just retransmitted. Ignoring.",
                             SSL_GETPID(), ss->fd));
                             rv = SECSuccess;
                             break;
                         }
                 } else if (ss->ssl3.hs.rtTimerCb == dtls_FinishedTimerCb) {
                     /* Retransmit the messages and re-arm the timer
                      * Note that we are not backing off the timer here.
                      * The spec isn't clear and my reasoning is that this
                      * may be a re-ordered packet rather than slowness,
                      * so let's be aggressive. */
                     dtls_CancelTimer(ss);
                     rv = dtls_TransmitMessageFlight(ss);
                     if (rv == SECSuccess) {
                         rv = dtls_StartTimer(ss, dtls_FinishedTimerCb);
                     }
                     if (rv != SECSuccess)
                         return rv;
                     break;
                 }
             } else if (message_seq > ss->ssl3.hs.recvMessageSeq) {
                 /* Case 2
                  *
                  * Ignore this message. This means we don't handle out of
                  * order complete messages that well, but we're still
                  * compliant and this probably does not happen often
                  *
                  * XXX OK for now. Maybe do something smarter at some point?
                  */
             } else {
                 /* Case 1
                  *
                  * Buffer the fragment for reassembly
                  */
                 /* Make room for the message */
                 if (ss->ssl3.hs.recvdHighWater == -1) {
                     PRUint32 map_length = OFFSET_BYTE(message_length) + 1;
                     rv = sslBuffer_Grow(&ss->ssl3.hs.msg_body, message_length);
                     if (rv != SECSuccess)
                         break;
                     /* Make room for the fragment map */
                     rv = sslBuffer_Grow(&ss->ssl3.hs.recvdFragments,
                                         map_length);
                     if (rv != SECSuccess)
                         break;
                     /* Reset the reassembly map */
                     ss->ssl3.hs.recvdHighWater = 0;
                     PORT_Memset(ss->ssl3.hs.recvdFragments.buf, 0,
                                 ss->ssl3.hs.recvdFragments.space);
                     ss->ssl3.hs.msg_type = (SSL3HandshakeType)type;
                     ss->ssl3.hs.msg_len = message_length;
                 }
                 /* If we have a message length mismatch, abandon the reassembly
                  * in progress and hope that the next retransmit will give us
                  * something sane
                  */
                 if (message_length != ss->ssl3.hs.msg_len) {
                     ss->ssl3.hs.recvdHighWater = -1;
                     PORT_SetError(SSL_ERROR_RX_MALFORMED_HANDSHAKE);
                     rv = SECFailure;
                     break;
                 }
                 /* Now copy this fragment into the buffer */
                 PORT_Assert((fragment_offset + fragment_length) <=
                             ss->ssl3.hs.msg_body.space);
                 PORT_Memcpy(ss->ssl3.hs.msg_body.buf + fragment_offset,
                             buf.buf, fragment_length);
                 /* This logic is a bit tricky. We have two values for
                  * reassembly state:
                  *
                  * - recvdHighWater contains the highest contiguous number of
                  *   bytes received
                  * - recvdFragments contains a bitmask of packets received
                  *   above recvdHighWater
                  *
                  * This avoids having to fill in the bitmask in the common
                  * case of adjacent fragments received in sequence
                  */
                 if (fragment_offset <= ss->ssl3.hs.recvdHighWater) {
                     /* Either this is the adjacent fragment or an overlapping
                      * fragment */
                     ss->ssl3.hs.recvdHighWater = fragment_offset +
                                                  fragment_length;
                 } else {
                     for (offset = fragment_offset;
                          offset < fragment_offset + fragment_length;
                          offset++) {
                         ss->ssl3.hs.recvdFragments.buf[OFFSET_BYTE(offset)] |=
                             OFFSET_MASK(offset);
                     }
                 }
                 /* Now figure out the new high water mark if appropriate */
                 for (offset = ss->ssl3.hs.recvdHighWater;
                      offset < ss->ssl3.hs.msg_len; offset++) {
                     /* Note that this loop is not efficient, since it counts
                      * bit by bit. If we have a lot of out-of-order packets,
                      * we should optimize this */
                     if (ss->ssl3.hs.recvdFragments.buf[OFFSET_BYTE(offset)] &
                         OFFSET_MASK(offset)) {
                         ss->ssl3.hs.recvdHighWater++;
                     } else {
                         break;
                     }
                 }
                 /* If we have all the bytes, then we are good to go */
                 if (ss->ssl3.hs.recvdHighWater == ss->ssl3.hs.msg_len) {
                     ss->ssl3.hs.recvdHighWater = -1;
                     rv = ssl3_HandleHandshakeMessage(ss,
                                                      ss->ssl3.hs.msg_body.buf,
                                                      ss->ssl3.hs.msg_len);
                     if (rv == SECFailure)
                         break; /* Skip rest of record */
                     /* At this point we are advancing our state machine, so
                      * we can free our last flight of messages */
                     dtls_FreeHandshakeMessages(&ss->ssl3.hs.lastMessageFlight);
                     dtls_CancelTimer(ss);
                     /* If there have been no retries this time, reset the
                      * timer value to the default per Section 4.2.4.1 */
                     if (ss->ssl3.hs.rtRetries == 0) {
                         ss->ssl3.hs.rtTimeoutMs = INITIAL_DTLS_TIMEOUT_MS;
                     }
                 }
             }
         }
         buf.buf += fragment_length;
         buf.len -= fragment_length;
     }
     origBuf->len = 0;   /* So ssl3_GatherAppDataRecord will keep looping. */
     /* XXX OK for now. In future handle rv == SECWouldBlock safely in order
      * to deal with asynchronous certificate verification */
     return rv;
 }
 /* Enqueue a message (either handshake or CCS)
  *
  * Called from:
  *              dtls_StageHandshakeMessage()
  *              ssl3_SendChangeCipherSpecs()
  */
 SECStatus dtls_QueueMessage(sslSocket *ss, SSL3ContentType type,
     const SSL3Opaque *pIn, PRInt32 nIn)
 {
     SECStatus rv = SECSuccess;
     DTLSQueuedMessage *msg = NULL;
     PORT_Assert(ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss));
     PORT_Assert(ss->opt.noLocks || ssl_HaveXmitBufLock(ss));
     msg = dtls_AllocQueuedMessage(ss->ssl3.cwSpec->epoch, type, pIn, nIn);
     if (!msg) {
         PORT_SetError(SEC_ERROR_NO_MEMORY);
         rv = SECFailure;
     } else {
         PR_APPEND_LINK(&msg->link, &ss->ssl3.hs.lastMessageFlight);
     }
     return rv;
 }
 /* Add DTLS handshake message to the pending queue
  * Empty the sendBuf buffer.
  * This function returns SECSuccess or SECFailure, never SECWouldBlock.
  * Always set sendBuf.len to 0, even when returning SECFailure.
  *
  * Called from:
  *              ssl3_AppendHandshakeHeader()
  *              dtls_FlushHandshake()
  */
 SECStatus
 dtls_StageHandshakeMessage(sslSocket *ss)
 {
     SECStatus rv = SECSuccess;
     PORT_Assert(ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss));
     PORT_Assert(ss->opt.noLocks || ssl_HaveXmitBufLock(ss));
     /* This function is sometimes called when no data is actually to
      * be staged, so just return SECSuccess. */
     if (!ss->sec.ci.sendBuf.buf || !ss->sec.ci.sendBuf.len)
         return rv;
     rv = dtls_QueueMessage(ss, content_handshake,
                            ss->sec.ci.sendBuf.buf, ss->sec.ci.sendBuf.len);
     /* Whether we succeeded or failed, toss the old handshake data. */
     ss->sec.ci.sendBuf.len = 0;
     return rv;
 }
 /* Enqueue the handshake message in sendBuf (if any) and then
  * transmit the resulting flight of handshake messages.
  *
  * Called from:
  *              ssl3_FlushHandshake()
  */
 SECStatus
 dtls_FlushHandshakeMessages(sslSocket *ss, PRInt32 flags)
 {
     SECStatus rv = SECSuccess;
     PORT_Assert(ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss));
     PORT_Assert(ss->opt.noLocks || ssl_HaveXmitBufLock(ss));
     rv = dtls_StageHandshakeMessage(ss);
     if (rv != SECSuccess)
         return rv;
     if (!(flags & ssl_SEND_FLAG_FORCE_INTO_BUFFER)) {
         rv = dtls_TransmitMessageFlight(ss);
         if (rv != SECSuccess)
             return rv;
         if (!(flags & ssl_SEND_FLAG_NO_RETRANSMIT)) {
             ss->ssl3.hs.rtRetries = 0;
             rv = dtls_StartTimer(ss, dtls_RetransmitTimerExpiredCb);
         }
     }
     return rv;
 }
 /* The callback for when the retransmit timer expires
  *
  * Called from:
  *              dtls_CheckTimer()
  *              dtls_HandleHandshake()
  */
 static void
 dtls_RetransmitTimerExpiredCb(sslSocket *ss)
 {
     SECStatus rv = SECFailure;
     ss->ssl3.hs.rtRetries++;
     if (!(ss->ssl3.hs.rtRetries % 3)) {
         /* If one of the messages was potentially greater than > MTU,
          * then downgrade. Do this every time we have retransmitted a
          * message twice, per RFC 6347 Sec. 4.1.1 */
         dtls_SetMTU(ss, ss->ssl3.hs.maxMessageSent - 1);
     }
     rv = dtls_TransmitMessageFlight(ss);
     if (rv == SECSuccess) {
         /* Re-arm the timer */
         rv = dtls_RestartTimer(ss, PR_TRUE, dtls_RetransmitTimerExpiredCb);
     }
     if (rv == SECFailure) {
         /* XXX OK for now. In future maybe signal the stack that we couldn't
          * transmit. For now, let the read handle any real network errors */
     }
 }
 /* Transmit a flight of handshake messages, stuffing them
  * into as few records as seems reasonable
  *
  * Called from:
  *             dtls_FlushHandshake()
  *             dtls_RetransmitTimerExpiredCb()
  */
 static SECStatus
 dtls_TransmitMessageFlight(sslSocket *ss)
 {
     SECStatus rv = SECSuccess;
     PRCList *msg_p;
     PRUint16 room_left = ss->ssl3.mtu;
     PRInt32 sent;
     ssl_GetXmitBufLock(ss);
     ssl_GetSpecReadLock(ss);
     /* DTLS does not buffer its handshake messages in
      * ss->pendingBuf, but rather in the lastMessageFlight
      * structure. This is just a sanity check that
      * some programming error hasn't inadvertantly
      * stuffed something in ss->pendingBuf
      */
     PORT_Assert(!ss->pendingBuf.len);
     for (msg_p = PR_LIST_HEAD(&ss->ssl3.hs.lastMessageFlight);
          msg_p != &ss->ssl3.hs.lastMessageFlight;
          msg_p = PR_NEXT_LINK(msg_p)) {
         DTLSQueuedMessage *msg = (DTLSQueuedMessage *)msg_p;
         /* The logic here is:
          *
          * 1. If this is a message that will not fit into the remaining
          *    space, then flush.
          * 2. If the message will now fit into the remaining space,
          *    encrypt, buffer, and loop.
          * 3. If the message will not fit, then fragment.
          *
          * At the end of the function, flush.
          */
         if ((msg->len + SSL3_BUFFER_FUDGE) > room_left) {
             /* The message will not fit into the remaining space, so flush */
             rv = dtls_SendSavedWriteData(ss);
             if (rv != SECSuccess)
                 break;
             room_left = ss->ssl3.mtu;
         }
         if ((msg->len + SSL3_BUFFER_FUDGE) <= room_left) {
             /* The message will fit, so encrypt and then continue with the
              * next packet */
             sent = ssl3_SendRecord(ss, msg->epoch, msg->type,
                                    msg->data, msg->len,
                                    ssl_SEND_FLAG_FORCE_INTO_BUFFER |
                                    ssl_SEND_FLAG_USE_EPOCH);
             if (sent != msg->len) {
                 rv = SECFailure;
                 if (sent != -1) {
                     PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
                 }
                 break;
             }
             room_left = ss->ssl3.mtu - ss->pendingBuf.len;
         } else {
             /* The message will not fit, so fragment.
              *
              * XXX OK for now. Arrange to coalesce the last fragment
              * of this message with the next message if possible.
              * That would be more efficient.
              */
             PRUint32 fragment_offset = 0;
             unsigned char fragment[DTLS_MAX_MTU]; /* >= than largest
                                                    * plausible MTU */
             /* Assert that we have already flushed */
             PORT_Assert(room_left == ss->ssl3.mtu);
             /* Case 3: We now need to fragment this message
              * DTLS only supports fragmenting handshaking messages */
             PORT_Assert(msg->type == content_handshake);
             /* The headers consume 12 bytes so the smalles possible
              *  message (i.e., an empty one) is 12 bytes
              */
             PORT_Assert(msg->len >= 12);
             while ((fragment_offset + 12) < msg->len) {
                 PRUint32 fragment_len;
                 const unsigned char *content = msg->data + 12;
                 PRUint32 content_len = msg->len - 12;
                 /* The reason we use 8 here is that that's the length of
                  * the new DTLS data that we add to the header */
                 fragment_len = PR_MIN(room_left - (SSL3_BUFFER_FUDGE + 8),
                                       content_len - fragment_offset);
                 PORT_Assert(fragment_len < DTLS_MAX_MTU - 12);
                 /* Make totally sure that we are within the buffer.
                  * Note that the only way that fragment len could get
                  * adjusted here is if
                  *
                  * (a) we are in release mode so the PORT_Assert is compiled out
                  * (b) either the MTU table is inconsistent with DTLS_MAX_MTU
                  * or ss->ssl3.mtu has become corrupt.
                  */
                 fragment_len = PR_MIN(fragment_len, DTLS_MAX_MTU - 12);
                 /* Construct an appropriate-sized fragment */
                 /* Type, length, sequence */
                 PORT_Memcpy(fragment, msg->data, 6);
                 /* Offset */
                 fragment[6] = (fragment_offset >> 16) & 0xff;
                 fragment[7] = (fragment_offset >> 8) & 0xff;
                 fragment[8] = (fragment_offset) & 0xff;
                 /* Fragment length */
                 fragment[9] = (fragment_len >> 16) & 0xff;
                 fragment[10] = (fragment_len >> 8) & 0xff;
                 fragment[11] = (fragment_len) & 0xff;
                 PORT_Memcpy(fragment + 12, content + fragment_offset,
                             fragment_len);
                 /*
                  *  Send the record. We do this in two stages
                  * 1. Encrypt
                  */
                 sent = ssl3_SendRecord(ss, msg->epoch, msg->type,
                                        fragment, fragment_len + 12,
                                        ssl_SEND_FLAG_FORCE_INTO_BUFFER |
                                        ssl_SEND_FLAG_USE_EPOCH);
                 if (sent != (fragment_len + 12)) {
                     rv = SECFailure;
                     if (sent != -1) {
                         PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
                     }
                     break;
                 }
                 /* 2. Flush */
                 rv = dtls_SendSavedWriteData(ss);
                 if (rv != SECSuccess)
                     break;
                 fragment_offset += fragment_len;
             }
         }
     }
     /* Finally, we need to flush */
     if (rv == SECSuccess)
         rv = dtls_SendSavedWriteData(ss);
     /* Give up the locks */
     ssl_ReleaseSpecReadLock(ss);
     ssl_ReleaseXmitBufLock(ss);
     return rv;
 }
 /* Flush the data in the pendingBuf and update the max message sent
  * so we can adjust the MTU estimate if we need to.
  * Wrapper for ssl_SendSavedWriteData.
  *
  * Called from dtls_TransmitMessageFlight()
  */
 static
 SECStatus dtls_SendSavedWriteData(sslSocket *ss)
 {
     PRInt32 sent;
     sent = ssl_SendSavedWriteData(ss);
     if (sent < 0)
         return SECFailure;
     /* We should always have complete writes b/c datagram sockets
      * don't really block */
     if (ss->pendingBuf.len > 0) {
         ssl_MapLowLevelError(SSL_ERROR_SOCKET_WRITE_FAILURE);
         return SECFailure;
     }
     /* Update the largest message sent so we can adjust the MTU
      * estimate if necessary */
     if (sent > ss->ssl3.hs.maxMessageSent)
         ss->ssl3.hs.maxMessageSent = sent;
     return SECSuccess;
 }
 /* Compress, MAC, encrypt a DTLS record. Allows specification of
  * the epoch using epoch value. If use_epoch is PR_TRUE then
  * we use the provided epoch. If use_epoch is PR_FALSE then
  * whatever the current value is in effect is used.
  *
  * Called from ssl3_SendRecord()
  */
 SECStatus
 dtls_CompressMACEncryptRecord(sslSocket *        ss,
                               DTLSEpoch          epoch,
                               PRBool             use_epoch,
                               SSL3ContentType    type,
                               const SSL3Opaque * pIn,
                               PRUint32           contentLen,
                               sslBuffer        * wrBuf)
 {
     SECStatus rv = SECFailure;
     ssl3CipherSpec *          cwSpec;
     ssl_GetSpecReadLock(ss);    /********************************/
     /* The reason for this switch-hitting code is that we might have
      * a flight of records spanning an epoch boundary, e.g.,
      *
      * ClientKeyExchange (epoch = 0)
      * ChangeCipherSpec (epoch = 0)
      * Finished (epoch = 1)
      *
      * Thus, each record needs a different cipher spec. The information
      * about which epoch to use is carried with the record.
      */
     if (use_epoch) {
         if (ss->ssl3.cwSpec->epoch == epoch)
             cwSpec = ss->ssl3.cwSpec;
         else if (ss->ssl3.pwSpec->epoch == epoch)
             cwSpec = ss->ssl3.pwSpec;
         else
             cwSpec = NULL;
     } else {
         cwSpec = ss->ssl3.cwSpec;
     }
     if (cwSpec) {
         rv = ssl3_CompressMACEncryptRecord(cwSpec, ss->sec.isServer, PR_TRUE,
                                            PR_FALSE, type, pIn, contentLen,
                                            wrBuf);
     } else {
         PR_NOT_REACHED("Couldn't find a cipher spec matching epoch");
         PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
     }
     ssl_ReleaseSpecReadLock(ss); /************************************/
     return rv;
 }
 /* Start a timer
  *
  * Called from:
  *             dtls_HandleHandshake()
  *             dtls_FlushHAndshake()
  *             dtls_RestartTimer()
  */
 SECStatus
 dtls_StartTimer(sslSocket *ss, DTLSTimerCb cb)
 {
     PORT_Assert(ss->ssl3.hs.rtTimerCb == NULL);
     ss->ssl3.hs.rtTimerStarted = PR_IntervalNow();
     ss->ssl3.hs.rtTimerCb = cb;
     return SECSuccess;
 }
 /* Restart a timer with optional backoff
  *
  * Called from dtls_RetransmitTimerExpiredCb()
  */
 SECStatus
 dtls_RestartTimer(sslSocket *ss, PRBool backoff, DTLSTimerCb cb)
 {
     if (backoff) {
         ss->ssl3.hs.rtTimeoutMs *= 2;
         if (ss->ssl3.hs.rtTimeoutMs > MAX_DTLS_TIMEOUT_MS)
             ss->ssl3.hs.rtTimeoutMs = MAX_DTLS_TIMEOUT_MS;
     }
     return dtls_StartTimer(ss, cb);
 }
 /* Cancel a pending timer
  *
  * Called from:
  *              dtls_HandleHandshake()
  *              dtls_CheckTimer()
  */
 void
 dtls_CancelTimer(sslSocket *ss)
 {
     PORT_Assert(ss->opt.noLocks || ssl_HaveRecvBufLock(ss));
     ss->ssl3.hs.rtTimerCb = NULL;
 }
 /* Check the pending timer and fire the callback if it expired
  *
  * Called from ssl3_GatherCompleteHandshake()
  */
 void
 dtls_CheckTimer(sslSocket *ss)
 {
     if (!ss->ssl3.hs.rtTimerCb)
         return;
     if ((PR_IntervalNow() - ss->ssl3.hs.rtTimerStarted) >
         PR_MillisecondsToInterval(ss->ssl3.hs.rtTimeoutMs)) {
         /* Timer has expired */
         DTLSTimerCb cb = ss->ssl3.hs.rtTimerCb;
         /* Cancel the timer so that we can call the CB safely */
         dtls_CancelTimer(ss);
         /* Now call the CB */
         cb(ss);
     }
 }
 /* The callback to fire when the holddown timer for the Finished
  * message expires and we can delete it
  *
  * Called from dtls_CheckTimer()
  */
 void
 dtls_FinishedTimerCb(sslSocket *ss)
 {
     ssl3_DestroyCipherSpec(ss->ssl3.pwSpec, PR_FALSE);
 }
 /* Cancel the Finished hold-down timer and destroy the
  * pending cipher spec. Note that this means that
  * successive rehandshakes will fail if the Finished is
  * lost.
  *
  * XXX OK for now. Figure out how to handle the combination
  * of Finished lost and rehandshake
  */
 void
 dtls_RehandshakeCleanup(sslSocket *ss)
 {
     dtls_CancelTimer(ss);
     ssl3_DestroyCipherSpec(ss->ssl3.pwSpec, PR_FALSE);
     ss->ssl3.hs.sendMessageSeq = 0;
     ss->ssl3.hs.recvMessageSeq = 0;
 }
 /* Set the MTU to the next step less than or equal to the
  * advertised value. Also used to downgrade the MTU by
  * doing dtls_SetMTU(ss, biggest packet set).
  *
  * Passing 0 means set this to the largest MTU known
  * (effectively resetting the PMTU backoff value).
  *
  * Called by:
  *            ssl3_InitState()
  *            dtls_RetransmitTimerExpiredCb()
  */
 void
 dtls_SetMTU(sslSocket *ss, PRUint16 advertised)
 {
     int i;
     if (advertised == 0) {
         ss->ssl3.mtu = COMMON_MTU_VALUES[0];
         SSL_TRC(30, ("Resetting MTU to %d", ss->ssl3.mtu));
         return;
     }
     for (i = 0; i < PR_ARRAY_SIZE(COMMON_MTU_VALUES); i++) {
         if (COMMON_MTU_VALUES[i] <= advertised) {
             ss->ssl3.mtu = COMMON_MTU_VALUES[i];
             SSL_TRC(30, ("Resetting MTU to %d", ss->ssl3.mtu));
             return;
         }
     }
     /* Fallback */
     ss->ssl3.mtu = COMMON_MTU_VALUES[PR_ARRAY_SIZE(COMMON_MTU_VALUES)-1];
     SSL_TRC(30, ("Resetting MTU to %d", ss->ssl3.mtu));
 }
 /* Called from ssl3_HandleHandshakeMessage() when it has deciphered a
  * DTLS hello_verify_request
  * Caller must hold Handshake and RecvBuf locks.
  */
 SECStatus
 dtls_HandleHelloVerifyRequest(sslSocket *ss, SSL3Opaque *b, PRUint32 length)
 {
     int                 errCode = SSL_ERROR_RX_MALFORMED_HELLO_VERIFY_REQUEST;
     SECStatus           rv;
     PRInt32             temp;
     SECItem             cookie = {siBuffer, NULL, 0};
     SSL3AlertDescription desc   = illegal_parameter;
     SSL_TRC(3, ("%d: SSL3[%d]: handle hello_verify_request handshake",
         SSL_GETPID(), ss->fd));
     PORT_Assert(ss->opt.noLocks || ssl_HaveRecvBufLock(ss));
     PORT_Assert(ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss));
     if (ss->ssl3.hs.ws != wait_server_hello) {
         errCode = SSL_ERROR_RX_UNEXPECTED_HELLO_VERIFY_REQUEST;
         desc    = unexpected_message;
         goto alert_loser;
     }
     /* The version */
     temp = ssl3_ConsumeHandshakeNumber(ss, 2, &b, &length);
     if (temp < 0) {
         goto loser;     /* alert has been sent */
     }
     if (temp != SSL_LIBRARY_VERSION_DTLS_1_0_WIRE &&
         temp != SSL_LIBRARY_VERSION_DTLS_1_2_WIRE) {
         goto alert_loser;
     }
     /* The cookie */
     rv = ssl3_ConsumeHandshakeVariable(ss, &cookie, 1, &b, &length);
     if (rv != SECSuccess) {
         goto loser;     /* alert has been sent */
     }
     if (cookie.len > DTLS_COOKIE_BYTES) {
         desc = decode_error;
         goto alert_loser;       /* malformed. */
     }
     PORT_Memcpy(ss->ssl3.hs.cookie, cookie.data, cookie.len);
     ss->ssl3.hs.cookieLen = cookie.len;
     ssl_GetXmitBufLock(ss);             /*******************************/
     /* Now re-send the client hello */
     rv = ssl3_SendClientHello(ss, PR_TRUE);
     ssl_ReleaseXmitBufLock(ss);         /*******************************/
     if (rv == SECSuccess)
         return rv;
 alert_loser:
     (void)SSL3_SendAlert(ss, alert_fatal, desc);
 loser:
     errCode = ssl_MapLowLevelError(errCode);
     return SECFailure;
 }
 /* Initialize the DTLS anti-replay window
  *
  * Called from:
  *              ssl3_SetupPendingCipherSpec()
  *              ssl3_InitCipherSpec()
  */
 void
 dtls_InitRecvdRecords(DTLSRecvdRecords *records)
 {
     PORT_Memset(records->data, 0, sizeof(records->data));
     records->left = 0;
     records->right = DTLS_RECVD_RECORDS_WINDOW - 1;
 }
 /*
  * Has this DTLS record been received? Return values are:
  * -1 -- out of range to the left
  *  0 -- not received yet
  *  1 -- replay
  *
  *  Called from: dtls_HandleRecord()
  */
 int
 dtls_RecordGetRecvd(DTLSRecvdRecords *records, PRUint64 seq)
 {
     PRUint64 offset;
     /* Out of range to the left */
     if (seq < records->left) {
         return -1;
     }
     /* Out of range to the right; since we advance the window on
      * receipt, that means that this packet has not been received
      * yet */
     if (seq > records->right)
         return 0;
     offset = seq % DTLS_RECVD_RECORDS_WINDOW;
     return !!(records->data[offset / 8] & (1 << (offset % 8)));
 }
 /* Update the DTLS anti-replay window
  *
  * Called from ssl3_HandleRecord()
  */
 void
 dtls_RecordSetRecvd(DTLSRecvdRecords *records, PRUint64 seq)
 {
     PRUint64 offset;
     if (seq < records->left)
         return;
     if (seq > records->right) {
         PRUint64 new_left;
         PRUint64 new_right;
         PRUint64 right;
         /* Slide to the right; this is the tricky part
          *
          * 1. new_top is set to have room for seq, on the
          *    next byte boundary by setting the right 8
          *    bits of seq
          * 2. new_left is set to compensate.
          * 3. Zero all bits between top and new_top. Since
          *    this is a ring, this zeroes everything as-yet
          *    unseen. Because we always operate on byte
          *    boundaries, we can zero one byte at a time
          */
         new_right = seq | 0x07;
         new_left = (new_right - DTLS_RECVD_RECORDS_WINDOW) + 1;
         for (right = records->right + 8; right <= new_right; right += 8) {
             offset = right % DTLS_RECVD_RECORDS_WINDOW;
             records->data[offset / 8] = 0;
         }
         records->right = new_right;
         records->left = new_left;
     }
     offset = seq % DTLS_RECVD_RECORDS_WINDOW;
     records->data[offset / 8] |= (1 << (offset % 8));
 }
 SECStatus
 DTLS_GetHandshakeTimeout(PRFileDesc *socket, PRIntervalTime *timeout)
 {
     sslSocket * ss = NULL;
     PRIntervalTime elapsed;
     PRIntervalTime desired;
     ss = ssl_FindSocket(socket);
     if (!ss)
         return SECFailure;
     if (!IS_DTLS(ss))
         return SECFailure;
     if (!ss->ssl3.hs.rtTimerCb)
         return SECFailure;
     elapsed = PR_IntervalNow() - ss->ssl3.hs.rtTimerStarted;
     desired = PR_MillisecondsToInterval(ss->ssl3.hs.rtTimeoutMs);
     if (elapsed > desired) {
         /* Timer expired */
         *timeout = PR_INTERVAL_NO_WAIT;
     } else {
         *timeout = desired - elapsed;
     }
     return SECSuccess;
 }

The Tor Browser / annotate

security/nss/lib/ssl/dtlscon.c@b8a032363ba2 (annotated)

security/nss/lib/ssl/dtlscon.c