Test unknown TLS 1.3 ServerHello extensions.

These too must be rejected. Test both unknown extensions and extensions
in the wrong context.

Change-Id: I54d5a5060f9efc26e5e4d23a0bde3c0d4d302d09
Reviewed-on: https://boringssl-review.googlesource.com/11501
Reviewed-by: Steven Valdez <svaldez@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/ssl/test/runner/handshake_server.go b/ssl/test/runner/handshake_server.go
index abadf3a..59b34fa 100644
--- a/ssl/test/runner/handshake_server.go
+++ b/ssl/test/runner/handshake_server.go
@@ -359,9 +359,11 @@
 	config := c.config
 
 	hs.hello = &serverHelloMsg{
-		isDTLS:       c.isDTLS,
-		vers:         versionToWire(c.vers, c.isDTLS),
-		versOverride: config.Bugs.SendServerHelloVersion,
+		isDTLS:          c.isDTLS,
+		vers:            versionToWire(c.vers, c.isDTLS),
+		versOverride:    config.Bugs.SendServerHelloVersion,
+		customExtension: config.Bugs.CustomUnencryptedExtension,
+		unencryptedALPN: config.Bugs.SendUnencryptedALPN,
 	}
 
 	hs.hello.random = make([]byte, 32)