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.
+
+}
+
+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);
+    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 = ProcessResponse();
+    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 ProcessResponse() {
+    // Verify that we got a successful response.
+    int response = request_->GetResponseCode();
+    net::URLRequestStatus status = request_->GetStatus();
+    std::string data;
+    if (!status.is_success() || response != 200) {
+      LOG(ERROR)
+          << "Error " << response << " validating token: '" << data << "'";
+      return std::string();
+    }
+
+    // Decode the JSON data from the response.
+    request_->GetResponseAsString(&data);
+    scoped_ptr<base::Value> value(base::JSONReader::Read(data));
+    DictionaryValue* dict;
+    if (!value.get() || value->GetType() != base::Value::TYPE_DICTIONARY ||
+        !value->GetAsDictionary(&dict)) {
+      LOG(ERROR) << "Invalid token validation response: '" << data << "'";
+      return std::string();
+    }
+
+    std::string token_scope;
+    dict->GetStringWithoutPathExpansion("scope", &token_scope);
+    if (!IsValidScope(token_scope)) {
+      LOG(ERROR) << "Invalid scope: '" << token_scope
+          << "', expected: '" << token_scope_ <<"'.";
+      return std::string();
+    }
+
+    std::string 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(
+    const GURL& token_url,
+    const GURL& token_validation_url,
+    scoped_refptr<RsaKeyPair> key_pair,
+    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) {
+}
+
+UrlFetcherTokenValidatorFactory::~UrlFetcherTokenValidatorFactory() {
+}
+
+scoped_ptr<protocol::ThirdPartyHostAuthenticator::TokenValidator>
+UrlFetcherTokenValidatorFactory::CreateTokenValidator(
+    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_));
+}
+
+bool UrlFetcherTokenValidatorFactory::IsEnabled() const {
+  return token_url_.is_valid() && token_validation_url_.is_valid() && key_pair_;

[Sergey Ulanov, 2013/04/05 20:28:34]

If admin configured the policies but made a typo in one of the URL's then we'll
effectively disable third-party auth and use PIN auth instead. I don't think
it's the right thing to do here. When any of the policies is configured, but set
to invalid value we should treat this case as if third-party auth is enabled but
misconfigured. Obviously it will not be possible to connect to the host in that
case, so we should yell loudly about it in the logs.

[Wez, 2013/04/05 22:46:12]

Generally speaking we should disable the host entirely if any policy is
malformed, but leave it running & monitoring policy so it can be re-enabled by a
subsequent fix to policies.

[rmsousa, 2013/04/06 00:37:25]

I moved this logic to the host itself. At the time it's creating the
authenticator factory, the host knows exactly what kind of authentication it'll
use, so it might as well only create the validator if it's going to be used (and
explicitly create a rejecting factory if the policies are inconsistent).

+}
+
+
+}  // namespace remoting