tls: show human-readable error messages

Before this commit, verification exceptions had err.message set to the
OpenSSL error code (e.g. 'UNABLE_TO_VERIFY_LEAF_SIGNATURE').

This commit moves the error code to err.code and replaces err.message
with a human-readable error.  Example:

    // before
    {
      message: 'UNABLE_TO_VERIFY_LEAF_SIGNATURE'
    }

    // after
    {
      code: 'UNABLE_TO_VERIFY_LEAF_SIGNATURE',
      message: 'unable to verify the first certificate'
    }

UNABLE_TO_VERIFY_LEAF_SIGNATURE is a good example of why you want this:
the error code suggests that it's the last certificate that fails to
validate while it's actually the first certificate in the chain.

Going by the number of mailing list posts and StackOverflow questions,
it's a source of confusion to many people.

4 files changed, 72 insertions, 28 deletions

diff --git a/doc/api/tls.markdown b/doc/api/tls.markdown
index a0fbe9a12..ceb1304a7 100644
--- a/doc/api/tls.markdown
+++ b/doc/api/tls.markdown
@@ -294,7 +294,7 @@ Creates a new client connection to the given `port` and `host` (old API) or
 
   - `rejectUnauthorized`: If `true`, the server certificate is verified against
     the list of supplied CAs. An `'error'` event is emitted if verification
-    fails. Default: `true`.
+    fails; `err.code` contains the OpenSSL error code. Default: `true`.
 
   - `NPNProtocols`: An array of strings or `Buffer`s containing supported NPN
     protocols. `Buffer`s should have following format: `0x05hello0x05world`,
diff --git a/lib/_tls_wrap.js b/lib/_tls_wrap.js
index 861508b9d..80887771b 100644
--- a/lib/_tls_wrap.js
+++ b/lib/_tls_wrap.js
@@ -526,7 +526,7 @@ function Server(/* [options], listener */) {
       if (socket._requestCert) {
         var verifyError = socket.ssl.verifyError();
         if (verifyError) {
-          socket.authorizationError = verifyError.message;
+          socket.authorizationError = verifyError.code;
 
           if (socket._rejectUnauthorized)
             socket.destroy();
@@ -788,7 +788,7 @@ exports.connect = function(/* [port, host], options, cb */) {
 
       if (verifyError) {
         result.authorized = false;
-        result.authorizationError = verifyError.message;
+        result.authorizationError = verifyError.code || verifyError.message;
 
         if (options.rejectUnauthorized) {
           result.emit('error', verifyError);
diff --git a/src/node_crypto.cc b/src/node_crypto.cc
index 6b6beb40b..936f3a903 100644
--- a/src/node_crypto.cc
+++ b/src/node_crypto.cc
@@ -83,6 +83,7 @@ using v8::FunctionTemplate;
 using v8::Handle;
 using v8::HandleScope;
 using v8::Integer;
+using v8::Isolate;
 using v8::Local;
 using v8::Null;
 using v8::Object;
@@ -1248,32 +1249,31 @@ void SSLWrap<Base>::IsInitFinished(const FunctionCallbackInfo<Value>& args) {
 }
 
 
-#define CASE_X509_ERR(CODE) case X509_V_ERR_##CODE: reason = #CODE; break;
 template <class Base>
 void SSLWrap<Base>::VerifyError(const FunctionCallbackInfo<Value>& args) {
   HandleScope scope(node_isolate);
 
   Base* w = Unwrap<Base>(args.This());
 
-  // XXX(indutny) Do this check in JS land?
-  X509* peer_cert = SSL_get_peer_certificate(w->ssl_);
-  if (peer_cert == NULL) {
-    // We requested a certificate and they did not send us one.
-    // Definitely an error.
-    // XXX(indutny) is this the right error message?
-    Local<String> s =
-        FIXED_ONE_BYTE_STRING(node_isolate, "UNABLE_TO_GET_ISSUER_CERT");
-    return args.GetReturnValue().Set(Exception::Error(s));
+  // XXX(bnoordhuis) The UNABLE_TO_GET_ISSUER_CERT error when there is no
+  // peer certificate is questionable but it's compatible with what was
+  // here before.
+  long x509_verify_error = X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT;
+  if (X509* peer_cert = SSL_get_peer_certificate(w->ssl_)) {
+    X509_free(peer_cert);
+    x509_verify_error = SSL_get_verify_result(w->ssl_);
   }
-  X509_free(peer_cert);
 
-  long x509_verify_error = SSL_get_verify_result(w->ssl_);
+  if (x509_verify_error == X509_V_OK)
+    return args.GetReturnValue().SetNull();
 
-  const char* reason = NULL;
-  Local<String> s;
+  // XXX(bnoordhuis) X509_verify_cert_error_string() is not actually thread-safe
+  // in the presence of invalid error codes.  Probably academical but something
+  // to keep in mind if/when node ever grows multi-isolate capabilities.
+  const char* reason = X509_verify_cert_error_string(x509_verify_error);
+  const char* code = reason;
+#define CASE_X509_ERR(CODE) case X509_V_ERR_##CODE: code = #CODE; break;
   switch (x509_verify_error) {
-    case X509_V_OK:
-      return args.GetReturnValue().SetNull();
     CASE_X509_ERR(UNABLE_TO_GET_ISSUER_CERT)
     CASE_X509_ERR(UNABLE_TO_GET_CRL)
     CASE_X509_ERR(UNABLE_TO_DECRYPT_CERT_SIGNATURE)
@@ -1301,18 +1301,17 @@ void SSLWrap<Base>::VerifyError(const FunctionCallbackInfo<Value>& args) {
     CASE_X509_ERR(INVALID_PURPOSE)
     CASE_X509_ERR(CERT_UNTRUSTED)
     CASE_X509_ERR(CERT_REJECTED)
-    default:
-      s = OneByteString(node_isolate,
-                        X509_verify_cert_error_string(x509_verify_error));
-      break;
   }
+#undef CASE_X509_ERR
 
-  if (s.IsEmpty())
-    s = OneByteString(node_isolate, reason);
-
-  args.GetReturnValue().Set(Exception::Error(s));
+  Isolate* isolate = args.GetIsolate();
+  Local<String> reason_string = OneByteString(isolate, reason);
+  Local<Value> exception_value = Exception::Error(reason_string);
+  Local<Object> exception_object = exception_value->ToObject();
+  exception_object->Set(FIXED_ONE_BYTE_STRING(isolate, "code"),
+                        OneByteString(isolate, code));
+  args.GetReturnValue().Set(exception_object);
 }
-#undef CASE_X509_ERR
 
 
 template <class Base>
diff --git a/test/simple/test-tls-friendly-error-message.js b/test/simple/test-tls-friendly-error-message.js
new file mode 100644
index 000000000..39fb30231
--- /dev/null
+++ b/test/simple/test-tls-friendly-error-message.js
@@ -0,0 +1,45 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+if (!process.versions.openssl) {
+  console.error('Skipping because node compiled without OpenSSL.');
+  process.exit(0);
+}
+
+var common = require('../common');
+var assert = require('assert');
+var fs = require('fs');
+var tls = require('tls');
+
+var key = fs.readFileSync(common.fixturesDir + '/keys/agent1-key.pem');
+var cert = fs.readFileSync(common.fixturesDir + '/keys/agent1-cert.pem');
+
+tls.createServer({ key: key, cert: cert }, function(conn) {
+  conn.end();
+  this.close();
+}).listen(0, function() {
+  var options = { port: this.address().port, rejectUnauthorized: true };
+  tls.connect(options).on('error', common.mustCall(function(err) {
+    assert.equal(err.code, 'UNABLE_TO_VERIFY_LEAF_SIGNATURE');
+    assert.equal(err.message, 'unable to verify the first certificate');
+    this.destroy();
+  }));
+});