Host-side third party token validation

remoting/host/url_fetcher_token_validator_factory.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/host/url_fetcher_token_validator_factory.h"
+
+#include <set>
+
+#include "base/base64.h"
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/json/json_reader.h"
+#include "base/location.h"
+#include "base/logging.h"
+#include "base/single_thread_task_runner.h"
+#include "base/values.h"
+#include "crypto/random.h"
+#include "googleurl/src/gurl.h"
+#include "net/base/escape.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "net/url_request/url_request_status.h"
+#include "remoting/base/rsa_key_pair.h"
+
+namespace {
+
+  // Length in bytes of the cryptographic nonce used to salt the token scope.
+  const size_t kNonceLength = 16;  // 128 bits.

[Sergey Ulanov, 2013/03/28 22:34:54]

indentation

[rmsousa, 2013/04/04 22:13:43]

Done.

+
+}
+
+namespace remoting {
+
+class UrlFetcherTokenValidator
+    : public net::URLFetcherDelegate,
+      public protocol::ThirdPartyHostAuthenticator::TokenValidator {
+ public:
+  UrlFetcherTokenValidator(
+      const GURL& token_url,
+      const GURL& token_validation_url,
+      scoped_refptr<RsaKeyPair> key_pair,
+      const std::string& local_jid,
+      const std::string& remote_jid,
+      scoped_refptr<net::URLRequestContextGetter> request_context_getter)
+      : token_url_(token_url),
+        token_validation_url_(token_validation_url),
+        key_pair_(key_pair),
+        request_context_getter_(request_context_getter) {
+    DCHECK(token_url_.is_valid());
+    DCHECK(token_validation_url_.is_valid());
+    DCHECK(key_pair_);
+    token_scope_ = CreateScope(local_jid, remote_jid);
+  }
+
+  virtual ~UrlFetcherTokenValidator() {
+  }
+
+  // TokenValidator interface.
+  virtual void ValidateThirdPartyToken(
+      const std::string& token,
+      const base::Callback<void(
+          const std::string& shared_secret)>& on_token_validated) OVERRIDE {
+    DCHECK(!request_);
+    DCHECK(!on_token_validated.is_null());
+
+    on_token_validated_ = on_token_validated;
+
+    std::string post_body =
+        "code=" + net::EscapeUrlEncodedData(token, true) +
+        "&client_id=" + net::EscapeUrlEncodedData(
+            key_pair_->GetPublicKey(), true) +
+        "&client_secret=" + net::EscapeUrlEncodedData(
+            key_pair_->SignMessage(token), true) +
+        "&grant_type=authorization_code";
+    request_.reset(net::URLFetcher::Create(
+        token_validation_url_, net::URLFetcher::POST, this));
+    request_->SetUploadData("application/x-www-form-urlencoded", post_body);

[Sergey Ulanov, 2013/03/28 22:34:54]

Can we use json here instead of url-encoding the data?

[rmsousa, 2013/03/28 23:12:49]

I'm trying to follow the OAuth protocol, which uses an URL-encoded request here
(perhaps because, even if it's a bad idea, one could possibly use GET here).
It's kinda funny that the request is URL encoded and the response is in JSON,
but, well, that's the protocol...

[Sergey Ulanov, 2013/03/28 23:39:39]

I'm not sure why we need to worry about OAuth here. Will the protocol be
compatible with OAuth? I.e. is it possible to take existing OAuth provider and
use it for host authentication? If not, then I don't see why we need to worry
about protocol compatibility.

[rmsousa, 2013/04/04 22:13:43]

Yes, the protocol will be OAuth. It's possible to use an OAuth lib to write a
host auth server.

+    request_->SetRequestContext(request_context_getter_);
+    request_->Start();
+  }
+
+  virtual const GURL& token_url() const OVERRIDE {
+    return token_url_;
+  }
+
+  virtual const std::string& token_scope() const OVERRIDE {
+    return token_scope_;
+  }
+
+  // URLFetcherDelegate interface.
+  virtual void OnURLFetchComplete(const net::URLFetcher* source) OVERRIDE {
+    DCHECK_EQ(request_.get(), source);
+    std::string shared_token = GetSharedSecretFromResponse(source);
+    on_token_validated_.Run(shared_token);
+    request_.reset();
+  }
+
+ private:
+  bool IsValidScope(const std::string& token_scope) {
+    // TODO(rmsousa): Deal with reordering/subsets/supersets/aliases/etc.
+    return token_scope == token_scope_;
+  }
+
+  static std::string CreateScope(const std::string& local_jid,
+                                 const std::string& remote_jid) {
+    char nonce_bytes[kNonceLength];
+    crypto::RandBytes(nonce_bytes, kNonceLength);
+    std::string nonce;
+    bool success = base::Base64Encode(nonce_bytes, &nonce);
+    DCHECK(success);
+    return "client:" + remote_jid + " host:" + local_jid + " nonce:" + nonce;
+  }
+
+  std::string GetSharedSecretFromResponse(const net::URLFetcher* source) {

[Sergey Ulanov, 2013/03/28 22:34:54]

Maybe call it ProcessResponse?

[Sergey Ulanov, 2013/03/28 22:34:54]

|source| is a meaningless name in this context, but you don't need this argument
and can use |request_| instead

[rmsousa, 2013/04/04 22:13:43]

Done.

[rmsousa, 2013/04/04 22:13:43]

Done.

+    std::string shared_secret;
+
+    // Verify that we got a successful response.
+    int response = source->GetResponseCode();
+    net::URLRequestStatus status = source->GetStatus();
+    std::string data;
+    if (!status.is_success() || response != 200) {
+      LOG(ERROR) <<

[Sergey Ulanov, 2013/03/28 22:34:54]

nit: wrap << operator

[rmsousa, 2013/04/04 22:13:43]

Done.

+          "Error " << response << " validating token: '" << data << "'";
+      return shared_secret;

[Sergey Ulanov, 2013/03/28 22:34:54]

This is confusing. Maybe better to return std::string() here and move
shared_secret declaration to the end.

[rmsousa, 2013/04/04 22:13:43]

Done.

+    }
+
+    // Decode the JSON data from the response.
+    source->GetResponseAsString(&data);
+    scoped_ptr<base::Value> value(base::JSONReader::Read(data));
+    if (!value.get() || value->GetType() != base::Value::TYPE_DICTIONARY) {
+      LOG(ERROR) << "Invalid token validation response: '" << data << "'";
+      return shared_secret;
+    }
+
+    // Get the scope from the response, and verify that it is valid.
+    DictionaryValue* dict = static_cast<DictionaryValue*>(value.get());

[Sergey Ulanov, 2013/03/28 22:34:54]

Ouch. Instead of downcasting using static_cast<> use Value::GetAsDictionary().

[rmsousa, 2013/04/04 22:13:43]

Done.

+    std::string token_scope;
+    dict->GetStringWithoutPathExpansion("scope", &token_scope);
+    if (!IsValidScope(token_scope)) {
+      LOG(ERROR) << "Invalid scope: '" << token_scope
+          << "', expected: '" << token_scope_ <<"'.";
+      return shared_secret;
+    }
+
+    // Everything is valid, so return the shared secret to the caller.
+    dict->GetStringWithoutPathExpansion("access_token", &shared_secret);
+    return shared_secret;
+  }
+
+  scoped_ptr<net::URLFetcher> request_;
+  GURL token_url_;
+  GURL token_validation_url_;
+  scoped_refptr<RsaKeyPair> key_pair_;
+  std::string token_scope_;
+  scoped_refptr<net::URLRequestContextGetter> request_context_getter_;
+  base::Callback<void(const std::string& shared_secret)> on_token_validated_;
+
+  DISALLOW_COPY_AND_ASSIGN(UrlFetcherTokenValidator);
+};
+
+UrlFetcherTokenValidatorFactory::UrlFetcherTokenValidatorFactory(
+    scoped_refptr<net::URLRequestContextGetter> request_context_getter)
+    : request_context_getter_(request_context_getter) {
+}
+
+UrlFetcherTokenValidatorFactory::~UrlFetcherTokenValidatorFactory() {
+}
+
+scoped_ptr<protocol::ThirdPartyHostAuthenticator::TokenValidator>
+UrlFetcherTokenValidatorFactory::CreateTokenValidator(
+    const GURL& token_url,
+    const GURL& token_validation_url,
+    scoped_refptr<RsaKeyPair> key_pair,
+    const std::string& local_jid,
+    const std::string& remote_jid) {
+  return scoped_ptr<protocol::ThirdPartyHostAuthenticator::TokenValidator>(
+      new UrlFetcherTokenValidator(token_url, token_validation_url, key_pair,
+                             local_jid, remote_jid, request_context_getter_));

[Sergey Ulanov, 2013/03/28 22:34:54]

indentation

[rmsousa, 2013/04/04 22:13:43]

Done.

+}
+
+}  // namespace remoting