Add a InvalidChannelIDSignature test.

Apparently we never wrote one of those. Also send a decrypt_error alert
to be consistent with all the other signature checks.

Change-Id: Ib5624d098d1e3086245192cdce92f5df26005064
Reviewed-on: https://boringssl-review.googlesource.com/11180
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/ssl/test/runner/runner.go b/ssl/test/runner/runner.go
index 01de14f..ba337d2 100644
--- a/ssl/test/runner/runner.go
+++ b/ssl/test/runner/runner.go
@@ -5010,6 +5010,22 @@
 		},
 		flags: []string{"-advertise-npn", "\x03foo\x03bar\x03baz"},
 	})
+
+	testCases = append(testCases, testCase{
+		testType: serverTest,
+		name:     "InvalidChannelIDSignature",
+		config: Config{
+			MaxVersion: VersionTLS12,
+			ChannelID:  channelIDKey,
+			Bugs: ProtocolBugs{
+				InvalidChannelIDSignature: true,
+			},
+		},
+		flags:              []string{"-enable-channel-id"},
+		shouldFail:         true,
+		expectedError:      ":CHANNEL_ID_SIGNATURE_INVALID:",
+		expectedLocalError: "remote error: error decrypting message",
+	})
 }
 
 func addResumptionVersionTests() {