Test that warning alerts are ignored.

Partly inspired by the new state exposed in
dc3da93899, stress this codepath by spamming our
poor shim with warning alerts.

Change-Id: I876c6e52911b6eb57493cf3e1782b37ea96d01f8
Reviewed-on: https://boringssl-review.googlesource.com/4112
Reviewed-by: Adam Langley <agl@google.com>

ssl/test/runner/common.go

@@ -679,6 +679,10 @@ type ProtocolBugs struct {
 	// IgnorePeerSignatureAlgorithmPreferences, if true, causes the peer's
 	// signature algorithm preferences to be ignored.
 	IgnorePeerSignatureAlgorithmPreferences bool
+
+	// SendWarningAlerts, if non-zero, causes every record to be prefaced by
+	// a warning alert.
+	SendWarningAlerts alert
 }
 
 func (c *Config) serverInit() {

ssl/test/runner/conn.go

@@ -829,6 +829,13 @@ func (c *Conn) writeV2Record(data []byte) (n int, err error) {
 // to the connection and updates the record layer state.
 // c.out.Mutex <= L.
 func (c *Conn) writeRecord(typ recordType, data []byte) (n int, err error) {
+	if typ != recordTypeAlert && c.config.Bugs.SendWarningAlerts != 0 {
+		alert := make([]byte, 2)
+		alert[0] = alertLevelWarning
+		alert[1] = byte(c.config.Bugs.SendWarningAlerts)
+		c.writeRecord(recordTypeAlert, alert)
+	}
+
 	if c.isDTLS {
 		return c.dtlsWriteRecord(typ, data)
 	}

ssl/test/runner/runner.go

@@ -904,6 +904,23 @@ var testCases = []testCase{
 		shouldFail:    true,
 		expectedError: ":WRONG_CIPHER_RETURNED:",
 	},
+	{
+		name: "SendWarningAlerts",
+		config: Config{
+			Bugs: ProtocolBugs{
+				SendWarningAlerts: alertAccessDenied,
+			},
+		},
+	},
+	{
+		protocol: dtls,
+		name:     "SendWarningAlerts-DTLS",
+		config: Config{
+			Bugs: ProtocolBugs{
+				SendWarningAlerts: alertAccessDenied,
+			},
+		},
+	},
 }
 
 func doExchange(test *testCase, config *Config, conn net.Conn, messageLen int, isResume bool) error {