Test the client rejects invalid compression methods from the server.

Change-Id: I90286da596d5822d4cfedf40995d80cf76adaf97
Reviewed-on: https://boringssl-review.googlesource.com/17536
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>

ssl/test/runner/common.go

@@ -1279,6 +1279,10 @@ type ProtocolBugs struct {
 	// send in the ClientHello.
 	SendCompressionMethods []byte
 
+	// SendCompressionMethod is the compression method to send in the
+	// ServerHello.
+	SendCompressionMethod byte
+
 	// AlwaysSendPreSharedKeyIdentityHint, if true, causes the server to
 	// always send a ServerKeyExchange for PSK ciphers, even if the identity
 	// hint is empty.

ssl/test/runner/handshake_server.go

@@ -1044,7 +1044,7 @@ func (hs *serverHandshakeState) processClientHello() (isResume bool, err error)
 		isDTLS:            c.isDTLS,
 		vers:              c.wireVersion,
 		versOverride:      config.Bugs.SendServerHelloVersion,
-		compressionMethod: compressionNone,
+		compressionMethod: config.Bugs.SendCompressionMethod,
 	}
 
 	hs.hello.random = make([]byte, 32)

ssl/test/runner/runner.go

@@ -2508,6 +2508,21 @@ func addBasicTests() {
 			expectedError:      ":INVALID_COMPRESSION_LIST:",
 			expectedLocalError: "remote error: illegal parameter",
 		},
+		// Test that the client rejects invalid compression methods
+		// from the server.
+		{
+			testType: clientTest,
+			name:     "InvalidCompressionMethod",
+			config: Config{
+				MaxVersion: VersionTLS12,
+				Bugs: ProtocolBugs{
+					SendCompressionMethod: 1,
+				},
+			},
+			shouldFail:         true,
+			expectedError:      ":UNSUPPORTED_COMPRESSION_ALGORITHM:",
+			expectedLocalError: "remote error: illegal parameter",
+		},
 		{
 			name: "GREASE-Client-TLS12",
 			config: Config{