PairingAuthenticator implementation and plumbing.

remoting/protocol/pairing_host_authenticator.cc

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/protocol/pairing_host_authenticator.h"
+
+#include "base/logging.h"
+#include "remoting/base/constants.h"
+#include "remoting/base/rsa_key_pair.h"
+#include "remoting/protocol/channel_authenticator.h"
+#include "remoting/protocol/pairing_registry.h"
+#include "remoting/protocol/v2_authenticator.h"
+#include "third_party/libjingle/source/talk/xmllite/xmlelement.h"
+
+namespace remoting {
+namespace protocol {
+
+namespace {
+// These definitions must be kept in sync with pairing_client_authenticator.cc.
+const buzz::StaticQName kPairingInfoTag =
+    { kChromotingXmlNamespace, "pairing-info" };
+const buzz::StaticQName kClientIdAttribute =
+    { "", "client-id" };
+const buzz::StaticQName kPairingFailedTag =
+    { kChromotingXmlNamespace, "pairing-failed" };
+const buzz::StaticQName kPairingErrorAttribute =
+    { "", "error" };
+}
+
+PairingHostAuthenticator::PairingHostAuthenticator(
+    scoped_refptr<PairingRegistry> pairing_registry,
+    const std::string& local_cert,
+    scoped_refptr<RsaKeyPair> key_pair,
+    const std::string& shared_secret,
+    State initial_state)
+    : pairing_registry_(pairing_registry),
+      local_cert_(local_cert),
+      key_pair_(key_pair),
+      shared_secret_(shared_secret),
+      protocol_error_(false) {
+  // If the client didn't specify an initial message, use the PIN as the shared
+  // secret. If it did, the authenticator will be created in ProcessMessage with
+  // the appropriate secret from the pairing registry.
+  if (initial_state != WAITING_MESSAGE) {
+    DCHECK_EQ(initial_state, MESSAGE_READY);
+    CreateV2AuthenticatorWithPIN(initial_state);
+  }
+}
+
+Authenticator::State PairingHostAuthenticator::state() const {
+  if (protocol_error_) {
+    return REJECTED;
+  } else if (!error_message_.empty()) {
+    return MESSAGE_READY;
+  } else if (v2_authenticator_) {
+    return v2_authenticator_->state();
+  } else {
+    return WAITING_MESSAGE;
+  }
+}
+
+Authenticator::RejectionReason
+PairingHostAuthenticator::rejection_reason() const {
+  DCHECK(v2_authenticator_);

[rmsousa, 2013/05/16 00:46:25]

if (!v2_authenticator_) return PROTOCOL_ERROR

[rmsousa, 2013/05/16 20:11:02]

Did you miss this one?

[Jamie, 2013/05/16 21:09:10]

I did, but looking at it, it seems redundant given the DCHECK. I appreciate that
the DCHECK doesn't do anything in release mode, but I'd prefer not to mask a
coding error with a silent failure. A crash with a stack trace is easier for us
to fix.

I did need to modify it so that if we've flagged an explicit protocol error,
then we return it here, but I think that's better than treating absence of the
v2_authenticator when this function is called as a protocol error.

[rmsousa, 2013/05/16 22:16:37]

Yes, that's what I meant - you needed to handle the protocol_error_ case here,
and that happens if and only if v2_authenticator_ is null (this function is only
called when state() == REJECTED). You can either implicitly check
v2_authenticator_ and do away with the protocol_error_ attribute, or have a
separate protocol_error_ boolean and test it explicitly (in which case I agree
that you should keep the DCHECK).

+  return v2_authenticator_->rejection_reason();
+}
+
+void PairingHostAuthenticator::ProcessMessage(
+    const buzz::XmlElement* message,
+    const base::Closure& resume_callback) {
+  DCHECK_EQ(state(), WAITING_MESSAGE);
+
+  // If there's already an underlying authenticator, defer to it.
+  if (v2_authenticator_) {
+    DCHECK_EQ(v2_authenticator_->state(), WAITING_MESSAGE);
+    v2_authenticator_->ProcessMessage(message, resume_callback);
+    return;
+  }
+
+  // If not, then create one based on the contents of the first message.
+  std::string client_id;
+  const buzz::XmlElement* pairing_tag = message->FirstNamed(kPairingInfoTag);
+  if (pairing_tag) {

[rmsousa, 2013/05/16 00:46:25]

Lack of pairing tag should be an error as well.

[rmsousa, 2013/05/16 20:11:02]

Did you miss this one?

[Jamie, 2013/05/16 21:09:10]

Sorry, yes. Done.

+    client_id = pairing_tag->Attr(kClientIdAttribute);
+    if (client_id.empty()) {
+      LOG(ERROR) << "No client id specified.";
+      protocol_error_ = true;
+      resume_callback.Run();
+      return;
+    }
+  }
+
+  std::string paired_secret = pairing_registry_->GetSecret(client_id);
+
+  if (paired_secret.empty()) {
+    LOG(INFO) << "Unknown client id";
+    error_message_ = "unknown-client-id";
+    CreateV2AuthenticatorWithPIN(WAITING_MESSAGE);
+    resume_callback.Run();
+    return;
+  }
+
+  v2_authenticator_ = V2Authenticator::CreateForHost(
+      local_cert_, key_pair_, paired_secret, MESSAGE_READY);
+  resume_callback.Run();
+}
+
+scoped_ptr<buzz::XmlElement> PairingHostAuthenticator::GetNextMessage() {
+  DCHECK_EQ(state(), MESSAGE_READY);
+
+  if (!error_message_.empty()) {
+    scoped_ptr<buzz::XmlElement> result = CreateEmptyAuthenticatorMessage();
+    buzz::XmlElement* pairing_failed_tag =
+        new buzz::XmlElement(kPairingFailedTag);
+    pairing_failed_tag->AddAttr(kPairingErrorAttribute, error_message_);
+    result->AddElement(pairing_failed_tag);
+    error_message_.clear();
+    return result.Pass();
+
+  } else {
+    DCHECK(v2_authenticator_);
+    return v2_authenticator_->GetNextMessage();
+  }
+}
+
+scoped_ptr<ChannelAuthenticator>
+PairingHostAuthenticator::CreateChannelAuthenticator() const {
+  DCHECK(v2_authenticator_);
+  return v2_authenticator_->CreateChannelAuthenticator();
+}
+
+void PairingHostAuthenticator::CreateV2AuthenticatorWithPIN(
+    State initial_state) {
+  DCHECK(!v2_authenticator_);
+  v2_authenticator_ = V2Authenticator::CreateForHost(
+      local_cert_, key_pair_, shared_secret_, initial_state);
+}
+
+}  // namespace protocol
+}  // namespace remoting