# HG changeset patch
# User Martin Thomson <martin.thomson@gmail.com>
# Date 1523260140 -36000
#      Mon Apr 09 17:49:00 2018 +1000
# Node ID 350b7210e90758de454feb4339379ef7f6b9b470
# Parent  5db9e969c74a2a02c4b1d918792827014d1a9d5e
Bug 1452549 - Discard application data that arrives before DTLS handshake completes, r=ekr

diff --git a/gtests/ssl_gtest/ssl_drop_unittest.cc b/gtests/ssl_gtest/ssl_drop_unittest.cc
--- a/gtests/ssl_gtest/ssl_drop_unittest.cc
+++ b/gtests/ssl_gtest/ssl_drop_unittest.cc
@@ -884,6 +884,45 @@ TEST_P(TlsConnectDatagram12Plus, MissAWi
   SendReceive();
 }
 
+// This filter replaces the first record it sees with junk application data.
+class TlsReplaceFirstRecordWithJunk : public TlsRecordFilter {
+ public:
+  TlsReplaceFirstRecordWithJunk(const std::shared_ptr<TlsAgent>& a)
+      : TlsRecordFilter(a), replaced_(false) {}
+
+ protected:
+  PacketFilter::Action FilterRecord(const TlsRecordHeader& header,
+                                    const DataBuffer& record, size_t* offset,
+                                    DataBuffer* output) override {
+    if (replaced_) {
+      return KEEP;
+    }
+    replaced_ = true;
+    TlsRecordHeader out_header(header.variant(), header.version(),
+                               kTlsApplicationDataType,
+                               header.sequence_number());
+
+    static const uint8_t junk[] = {1, 2, 3, 4};
+    *offset = out_header.Write(output, *offset, DataBuffer(junk, sizeof(junk)));
+    return CHANGE;
+  }
+
+ private:
+  bool replaced_;
+};
+
+// DTLS needs to discard application_data that it receives prior to handshake
+// completion, not generate an error.
+TEST_P(TlsConnectDatagram, ReplaceFirstServerRecordWithApplicationData) {
+  MakeTlsFilter<TlsReplaceFirstRecordWithJunk>(server_);
+  Connect();
+}
+
+TEST_P(TlsConnectDatagram, ReplaceFirstClientRecordWithApplicationData) {
+  MakeTlsFilter<TlsReplaceFirstRecordWithJunk>(client_);
+  Connect();
+}
+
 INSTANTIATE_TEST_CASE_P(Datagram12Plus, TlsConnectDatagram12Plus,
                         TlsConnectTestBase::kTlsV12Plus);
 INSTANTIATE_TEST_CASE_P(DatagramPre13, TlsConnectDatagramPre13,
diff --git a/lib/ssl/ssl3con.c b/lib/ssl/ssl3con.c
--- a/lib/ssl/ssl3con.c
+++ b/lib/ssl/ssl3con.c
@@ -12216,23 +12216,33 @@ ssl3_HandleRecord(sslSocket *ss, SSL3Cip
         }
     }
 
-#ifdef UNSAFE_FUZZER_MODE
+    /* Most record types aside from protected TLS 1.3 records carry the content
+     * type in the first octet. TLS 1.3 will override this value later. */
     rType = cText->hdr[0];
-    rv = Null_Cipher(NULL, plaintext->buf, (int *)&plaintext->len,
-                     plaintext->space, cText->buf->buf, cText->buf->len);
+    /* Encrypted application data records could arrive before the handshake
+     * completes in DTLS 1.3. These can look like valid TLS 1.2 application_data
+     * records in epoch 0, which is never valid. Pretend they didn't decrypt. */
+    if (spec->epoch == 0 && rType == content_application_data) {
+        PORT_SetError(SSL_ERROR_RX_UNEXPECTED_APPLICATION_DATA);
+        alert = unexpected_message;
+        rv = SECFailure;
+    } else {
+#ifdef UNSAFE_FUZZER_MODE
+        rv = Null_Cipher(NULL, plaintext->buf, (int *)&plaintext->len,
+                         plaintext->space, cText->buf->buf, cText->buf->len);
 #else
-    /* IMPORTANT: Unprotect functions MUST NOT send alerts
-     * because we still hold the spec read lock. Instead, if they
-     * return SECFailure, they set *alert to the alert to be sent. */
-    if (spec->version < SSL_LIBRARY_VERSION_TLS_1_3 ||
-        spec->cipherDef->calg == ssl_calg_null) {
-        /* Unencrypted TLS 1.3 records use the pre-TLS 1.3 format. */
-        rType = cText->hdr[0];
-        rv = ssl3_UnprotectRecord(ss, spec, cText, plaintext, &alert);
-    } else {
-        rv = tls13_UnprotectRecord(ss, spec, cText, plaintext, &rType, &alert);
-    }
+        /* IMPORTANT: Unprotect functions MUST NOT send alerts
+         * because we still hold the spec read lock. Instead, if they
+         * return SECFailure, they set *alert to the alert to be sent. */
+        if (spec->version < SSL_LIBRARY_VERSION_TLS_1_3 ||
+            spec->epoch == 0) {
+            rv = ssl3_UnprotectRecord(ss, spec, cText, plaintext, &alert);
+        } else {
+            rv = tls13_UnprotectRecord(ss, spec, cText, plaintext, &rType,
+                                       &alert);
+        }
 #endif
+    }
 
     if (rv != SECSuccess) {
         ssl_ReleaseSpecReadLock(ss); /***************************/
@@ -12242,10 +12252,10 @@ ssl3_HandleRecord(sslSocket *ss, SSL3Cip
         /* Ensure that we don't process this data again. */
         plaintext->len = 0;
 
-        /* Ignore a CCS if the alternative handshake is negotiated.  Note that
-         * this will fail if the server fails to negotiate the alternative
-         * handshake type in a 0-RTT session that is resumed from a session that
-         * did negotiate it.  We don't care about that corner case right now. */
+        /* Ignore a CCS if compatibility mode is negotiated.  Note that this
+         * will fail if the server fails to negotiate compatibility mode in a
+         * 0-RTT session that is resumed from a session that did negotiate it.
+         * We don't care about that corner case right now. */
         if (ss->version >= SSL_LIBRARY_VERSION_TLS_1_3 &&
             cText->hdr[0] == content_change_cipher_spec &&
             ss->ssl3.hs.ws != idle_handshake &&
@@ -12254,19 +12264,20 @@ ssl3_HandleRecord(sslSocket *ss, SSL3Cip
             /* Ignore the CCS. */
             return SECSuccess;
         }
+
         if (IS_DTLS(ss) ||
             (ss->sec.isServer &&
              ss->ssl3.hs.zeroRttIgnore == ssl_0rtt_ignore_trial)) {
             /* Silently drop the packet */
             return SECSuccess;
-        } else {
-            int errCode = PORT_GetError();
-            SSL3_SendAlert(ss, alert_fatal, alert);
-            /* Reset the error code in case SSL3_SendAlert called
-             * PORT_SetError(). */
-            PORT_SetError(errCode);
-            return SECFailure;
-        }
+        }
+
+        int errCode = PORT_GetError();
+        SSL3_SendAlert(ss, alert_fatal, alert);
+        /* Reset the error code in case SSL3_SendAlert called
+         * PORT_SetError(). */
+        PORT_SetError(errCode);
+        return SECFailure;
     }
 
     /* SECSuccess */