net/proxy/proxy_script_decider.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "net/proxy/proxy_script_decider.h"
   6
   7 #include "base/bind.h"
   8 #include "base/bind_helpers.h"
   9 #include "base/compiler_specific.h"
  10 #include "base/format_macros.h"
  11 #include "base/logging.h"
  12 #include "base/metrics/histogram_macros.h"
  13 #include "base/strings/string_util.h"
  14 #include "base/strings/utf_string_conversions.h"
  15 #include "base/values.h"
  16 #include "net/base/net_errors.h"
  17 #include "net/proxy/dhcp_proxy_script_fetcher.h"
  18 #include "net/proxy/dhcp_proxy_script_fetcher_factory.h"
  19 #include "net/proxy/proxy_script_fetcher.h"
  20 #include "net/url_request/url_request_context.h"
  21
  22 namespace net {
  23
  24 namespace {
  25
  26 bool LooksLikePacScript(const base::string16& script) {
  27   // Note: this is only an approximation! It may not always work correctly,
  28   // however it is very likely that legitimate scripts have this exact string,
  29   // since they must minimally define a function of this name. Conversely, a
  30   // file not containing the string is not likely to be a PAC script.
  31   //
  32   // An exact test would have to load the script in a javascript evaluator.
  33   return script.find(base::ASCIIToUTF16("FindProxyForURL")) !=
  34              base::string16::npos;
  35 }
  36
  37 }
  38
  39 // This is the hard-coded location used by the DNS portion of web proxy
  40 // auto-discovery.
  41 //
  42 // Note that we not use DNS devolution to find the WPAD host, since that could
  43 // be dangerous should our top level domain registry  become out of date.
  44 //
  45 // Instead we directly resolve "wpad", and let the operating system apply the
  46 // DNS suffix search paths. This is the same approach taken by Firefox, and
  47 // compatibility hasn't been an issue.
  48 //
  49 // For more details, also check out this comment:
  50 // http://code.google.com/p/chromium/issues/detail?id=18575#c20
  51 namespace {
  52 const char kWpadUrl[] = "http://wpad/wpad.dat";
  53 const int kQuickCheckDelayMs = 1000;
  54 };
  55
  56 scoped_ptr<base::Value> ProxyScriptDecider::PacSource::NetLogCallback(
  57     const GURL* effective_pac_url,
  58     NetLogCaptureMode /* capture_mode */) const {
  59   scoped_ptr<base::DictionaryValue> dict(new base::DictionaryValue());
  60   std::string source;
  61   switch (type) {
  62     case PacSource::WPAD_DHCP:
  63       source = "WPAD DHCP";
  64       break;
  65     case PacSource::WPAD_DNS:
  66       source = "WPAD DNS: ";
  67       source += effective_pac_url->possibly_invalid_spec();
  68       break;
  69     case PacSource::CUSTOM:
  70       source = "Custom PAC URL: ";
  71       source += effective_pac_url->possibly_invalid_spec();
  72       break;
  73   }
  74   dict->SetString("source", source);
  75   return dict.Pass();
  76 }
  77
  78 ProxyScriptDecider::ProxyScriptDecider(
  79     ProxyScriptFetcher* proxy_script_fetcher,
  80     DhcpProxyScriptFetcher* dhcp_proxy_script_fetcher,
  81     NetLog* net_log)
  82     : proxy_script_fetcher_(proxy_script_fetcher),
  83       dhcp_proxy_script_fetcher_(dhcp_proxy_script_fetcher),
  84       current_pac_source_index_(0u),
  85       pac_mandatory_(false),
  86       next_state_(STATE_NONE),
  87       net_log_(BoundNetLog::Make(net_log, NetLog::SOURCE_PROXY_SCRIPT_DECIDER)),
  88       fetch_pac_bytes_(false),
  89       quick_check_enabled_(true) {
  90   if (proxy_script_fetcher &&
  91       proxy_script_fetcher->GetRequestContext() &&
  92       proxy_script_fetcher->GetRequestContext()->host_resolver()) {
  93       host_resolver_.reset(new SingleRequestHostResolver(
  94           proxy_script_fetcher->GetRequestContext()->host_resolver()));
  95   }
  96 }
  97
  98 ProxyScriptDecider::~ProxyScriptDecider() {
  99   if (next_state_ != STATE_NONE)
 100     Cancel();
 101 }
 102
 103 int ProxyScriptDecider::Start(
 104     const ProxyConfig& config, const base::TimeDelta wait_delay,
 105     bool fetch_pac_bytes, const CompletionCallback& callback) {
 106   DCHECK_EQ(STATE_NONE, next_state_);
 107   DCHECK(!callback.is_null());
 108   DCHECK(config.HasAutomaticSettings());
 109
 110   net_log_.BeginEvent(NetLog::TYPE_PROXY_SCRIPT_DECIDER);
 111
 112   fetch_pac_bytes_ = fetch_pac_bytes;
 113
 114   // Save the |wait_delay| as a non-negative value.
 115   wait_delay_ = wait_delay;
 116   if (wait_delay_ < base::TimeDelta())
 117     wait_delay_ = base::TimeDelta();
 118
 119   pac_mandatory_ = config.pac_mandatory();
 120   have_custom_pac_url_ = config.has_pac_url();
 121
 122   pac_sources_ = BuildPacSourcesFallbackList(config);
 123   DCHECK(!pac_sources_.empty());
 124
 125   next_state_ = STATE_WAIT;
 126
 127   int rv = DoLoop(OK);
 128   if (rv == ERR_IO_PENDING)
 129     callback_ = callback;
 130   else
 131     DidComplete();
 132
 133   return rv;
 134 }
 135
 136 const ProxyConfig& ProxyScriptDecider::effective_config() const {
 137   DCHECK_EQ(STATE_NONE, next_state_);
 138   return effective_config_;
 139 }
 140
 141 // TODO(eroman): Return a const-pointer.
 142 ProxyResolverScriptData* ProxyScriptDecider::script_data() const {
 143   DCHECK_EQ(STATE_NONE, next_state_);
 144   return script_data_.get();
 145 }
 146
 147 // Initialize the fallback rules.
 148 // (1) WPAD (DHCP).
 149 // (2) WPAD (DNS).
 150 // (3) Custom PAC URL.
 151 ProxyScriptDecider::PacSourceList ProxyScriptDecider::
 152     BuildPacSourcesFallbackList(
 153     const ProxyConfig& config) const {
 154   PacSourceList pac_sources;
 155   if (config.auto_detect()) {
 156     pac_sources.push_back(PacSource(PacSource::WPAD_DHCP, GURL(kWpadUrl)));
 157     pac_sources.push_back(PacSource(PacSource::WPAD_DNS, GURL(kWpadUrl)));
 158   }
 159   if (config.has_pac_url())
 160     pac_sources.push_back(PacSource(PacSource::CUSTOM, config.pac_url()));
 161   return pac_sources;
 162 }
 163
 164 void ProxyScriptDecider::OnIOCompletion(int result) {
 165   DCHECK_NE(STATE_NONE, next_state_);
 166   int rv = DoLoop(result);
 167   if (rv != ERR_IO_PENDING) {
 168     DidComplete();
 169     DoCallback(rv);
 170   }
 171 }
 172
 173 int ProxyScriptDecider::DoLoop(int result) {
 174   DCHECK_NE(next_state_, STATE_NONE);
 175   int rv = result;
 176   do {
 177     State state = next_state_;
 178     next_state_ = STATE_NONE;
 179     switch (state) {
 180       case STATE_WAIT:
 181         DCHECK_EQ(OK, rv);
 182         rv = DoWait();
 183         break;
 184       case STATE_WAIT_COMPLETE:
 185         rv = DoWaitComplete(rv);
 186         break;
 187       case STATE_QUICK_CHECK:
 188         DCHECK_EQ(OK, rv);
 189         rv = DoQuickCheck();
 190         break;
 191       case STATE_QUICK_CHECK_COMPLETE:
 192         rv = DoQuickCheckComplete(rv);
 193         break;
 194       case STATE_FETCH_PAC_SCRIPT:
 195         DCHECK_EQ(OK, rv);
 196         rv = DoFetchPacScript();
 197         break;
 198       case STATE_FETCH_PAC_SCRIPT_COMPLETE:
 199         rv = DoFetchPacScriptComplete(rv);
 200         break;
 201       case STATE_VERIFY_PAC_SCRIPT:
 202         DCHECK_EQ(OK, rv);
 203         rv = DoVerifyPacScript();
 204         break;
 205       case STATE_VERIFY_PAC_SCRIPT_COMPLETE:
 206         rv = DoVerifyPacScriptComplete(rv);
 207         break;
 208       default:
 209         NOTREACHED() << "bad state";
 210         rv = ERR_UNEXPECTED;
 211         break;
 212     }
 213   } while (rv != ERR_IO_PENDING && next_state_ != STATE_NONE);
 214   return rv;
 215 }
 216
 217 void ProxyScriptDecider::DoCallback(int result) {
 218   DCHECK_NE(ERR_IO_PENDING, result);
 219   DCHECK(!callback_.is_null());
 220   callback_.Run(result);
 221 }
 222
 223 int ProxyScriptDecider::DoWait() {
 224   next_state_ = STATE_WAIT_COMPLETE;
 225
 226   // If no waiting is required, continue on to the next state.
 227   if (wait_delay_.ToInternalValue() == 0)
 228     return OK;
 229
 230   // Otherwise wait the specified amount of time.
 231   wait_timer_.Start(FROM_HERE, wait_delay_, this,
 232                     &ProxyScriptDecider::OnWaitTimerFired);
 233   net_log_.BeginEvent(NetLog::TYPE_PROXY_SCRIPT_DECIDER_WAIT);
 234   return ERR_IO_PENDING;
 235 }
 236
 237 int ProxyScriptDecider::DoWaitComplete(int result) {
 238   DCHECK_EQ(OK, result);
 239   if (wait_delay_.ToInternalValue() != 0) {
 240     net_log_.EndEventWithNetErrorCode(NetLog::TYPE_PROXY_SCRIPT_DECIDER_WAIT,
 241                                       result);
 242   }
 243   if (quick_check_enabled_ && current_pac_source().type == PacSource::WPAD_DNS)
 244     next_state_ = STATE_QUICK_CHECK;
 245   else
 246     next_state_ = GetStartState();
 247   return OK;
 248 }
 249
 250 int ProxyScriptDecider::DoQuickCheck() {
 251   DCHECK(quick_check_enabled_);
 252   if (host_resolver_.get() == NULL) {
 253     // If we have no resolver, skip QuickCheck altogether.
 254     next_state_ = GetStartState();
 255     return OK;
 256   }
 257
 258   quick_check_start_time_ = base::Time::Now();
 259   std::string host = current_pac_source().url.host();
 260   HostResolver::RequestInfo reqinfo(HostPortPair(host, 80));
 261   reqinfo.set_host_resolver_flags(HOST_RESOLVER_SYSTEM_ONLY);
 262   CompletionCallback callback = base::Bind(
 263       &ProxyScriptDecider::OnIOCompletion,
 264       base::Unretained(this));
 265
 266   next_state_ = STATE_QUICK_CHECK_COMPLETE;
 267   quick_check_timer_.Start(FROM_HERE,
 268                            base::TimeDelta::FromMilliseconds(
 269                               kQuickCheckDelayMs),
 270                            base::Bind(callback, ERR_NAME_NOT_RESOLVED));
 271
 272   // We use HIGHEST here because proxy decision blocks doing any other requests.
 273   return host_resolver_->Resolve(reqinfo, HIGHEST, &wpad_addresses_,
 274                                  callback, net_log_);
 275 }
 276
 277 int ProxyScriptDecider::DoQuickCheckComplete(int result) {
 278   DCHECK(quick_check_enabled_);
 279   base::TimeDelta delta = base::Time::Now() - quick_check_start_time_;
 280   if (result == OK)
 281     UMA_HISTOGRAM_TIMES("Net.WpadQuickCheckSuccess", delta);
 282   else
 283     UMA_HISTOGRAM_TIMES("Net.WpadQuickCheckFailure", delta);
 284   host_resolver_->Cancel();
 285   quick_check_timer_.Stop();
 286   if (result != OK)
 287     return TryToFallbackPacSource(result);
 288   next_state_ = GetStartState();
 289   return result;
 290 }
 291
 292 int ProxyScriptDecider::DoFetchPacScript() {
 293   DCHECK(fetch_pac_bytes_);
 294
 295   next_state_ = STATE_FETCH_PAC_SCRIPT_COMPLETE;
 296
 297   const PacSource& pac_source = current_pac_source();
 298
 299   GURL effective_pac_url;
 300   DetermineURL(pac_source, &effective_pac_url);
 301
 302   net_log_.BeginEvent(NetLog::TYPE_PROXY_SCRIPT_DECIDER_FETCH_PAC_SCRIPT,
 303                       base::Bind(&PacSource::NetLogCallback,
 304                                  base::Unretained(&pac_source),
 305                                  &effective_pac_url));
 306
 307   if (pac_source.type == PacSource::WPAD_DHCP) {
 308     if (!dhcp_proxy_script_fetcher_) {
 309       net_log_.AddEvent(NetLog::TYPE_PROXY_SCRIPT_DECIDER_HAS_NO_FETCHER);
 310       return ERR_UNEXPECTED;
 311     }
 312
 313     return dhcp_proxy_script_fetcher_->Fetch(
 314         &pac_script_, base::Bind(&ProxyScriptDecider::OnIOCompletion,
 315                                  base::Unretained(this)));
 316   }
 317
 318   if (!proxy_script_fetcher_) {
 319     net_log_.AddEvent(NetLog::TYPE_PROXY_SCRIPT_DECIDER_HAS_NO_FETCHER);
 320     return ERR_UNEXPECTED;
 321   }
 322
 323   return proxy_script_fetcher_->Fetch(
 324       effective_pac_url, &pac_script_,
 325       base::Bind(&ProxyScriptDecider::OnIOCompletion, base::Unretained(this)));
 326 }
 327
 328 int ProxyScriptDecider::DoFetchPacScriptComplete(int result) {
 329   DCHECK(fetch_pac_bytes_);
 330
 331   net_log_.EndEventWithNetErrorCode(
 332       NetLog::TYPE_PROXY_SCRIPT_DECIDER_FETCH_PAC_SCRIPT, result);
 333   if (result != OK)
 334     return TryToFallbackPacSource(result);
 335
 336   next_state_ = STATE_VERIFY_PAC_SCRIPT;
 337   return result;
 338 }
 339
 340 int ProxyScriptDecider::DoVerifyPacScript() {
 341   next_state_ = STATE_VERIFY_PAC_SCRIPT_COMPLETE;
 342
 343   // This is just a heuristic. Ideally we would try to parse the script.
 344   if (fetch_pac_bytes_ && !LooksLikePacScript(pac_script_))
 345     return ERR_PAC_SCRIPT_FAILED;
 346
 347   return OK;
 348 }
 349
 350 int ProxyScriptDecider::DoVerifyPacScriptComplete(int result) {
 351   if (result != OK)
 352     return TryToFallbackPacSource(result);
 353
 354   const PacSource& pac_source = current_pac_source();
 355
 356   // Extract the current script data.
 357   if (fetch_pac_bytes_) {
 358     script_data_ = ProxyResolverScriptData::FromUTF16(pac_script_);
 359   } else {
 360     script_data_ = pac_source.type == PacSource::CUSTOM ?
 361         ProxyResolverScriptData::FromURL(pac_source.url) :
 362         ProxyResolverScriptData::ForAutoDetect();
 363   }
 364
 365   // Let the caller know which automatic setting we ended up initializing the
 366   // resolver for (there may have been multiple fallbacks to choose from.)
 367   if (current_pac_source().type == PacSource::CUSTOM) {
 368     effective_config_ =
 369         ProxyConfig::CreateFromCustomPacURL(current_pac_source().url);
 370     effective_config_.set_pac_mandatory(pac_mandatory_);
 371   } else {
 372     if (fetch_pac_bytes_) {
 373       GURL auto_detected_url;
 374
 375       switch (current_pac_source().type) {
 376         case PacSource::WPAD_DHCP:
 377           auto_detected_url = dhcp_proxy_script_fetcher_->GetPacURL();
 378           break;
 379
 380         case PacSource::WPAD_DNS:
 381           auto_detected_url = GURL(kWpadUrl);
 382           break;
 383
 384         default:
 385           NOTREACHED();
 386       }
 387
 388       effective_config_ =
 389           ProxyConfig::CreateFromCustomPacURL(auto_detected_url);
 390     } else {
 391       // The resolver does its own resolution so we cannot know the
 392       // URL. Just do the best we can and state that the configuration
 393       // is to auto-detect proxy settings.
 394       effective_config_ = ProxyConfig::CreateAutoDetect();
 395     }
 396   }
 397
 398   return OK;
 399 }
 400
 401 int ProxyScriptDecider::TryToFallbackPacSource(int error) {
 402   DCHECK_LT(error, 0);
 403
 404   if (current_pac_source_index_ + 1 >= pac_sources_.size()) {
 405     // Nothing left to fall back to.
 406     return error;
 407   }
 408
 409   // Advance to next URL in our list.
 410   ++current_pac_source_index_;
 411
 412   net_log_.AddEvent(
 413       NetLog::TYPE_PROXY_SCRIPT_DECIDER_FALLING_BACK_TO_NEXT_PAC_SOURCE);
 414   if (quick_check_enabled_ && current_pac_source().type == PacSource::WPAD_DNS)
 415     next_state_ = STATE_QUICK_CHECK;
 416   else
 417     next_state_ = GetStartState();
 418
 419   return OK;
 420 }
 421
 422 ProxyScriptDecider::State ProxyScriptDecider::GetStartState() const {
 423   return fetch_pac_bytes_ ?  STATE_FETCH_PAC_SCRIPT : STATE_VERIFY_PAC_SCRIPT;
 424 }
 425
 426 void ProxyScriptDecider::DetermineURL(const PacSource& pac_source,
 427                                       GURL* effective_pac_url) {
 428   DCHECK(effective_pac_url);
 429
 430   switch (pac_source.type) {
 431     case PacSource::WPAD_DHCP:
 432       break;
 433     case PacSource::WPAD_DNS:
 434       *effective_pac_url = GURL(kWpadUrl);
 435       break;
 436     case PacSource::CUSTOM:
 437       *effective_pac_url = pac_source.url;
 438       break;
 439   }
 440 }
 441
 442 const ProxyScriptDecider::PacSource&
 443     ProxyScriptDecider::current_pac_source() const {
 444   DCHECK_LT(current_pac_source_index_, pac_sources_.size());
 445   return pac_sources_[current_pac_source_index_];
 446 }
 447
 448 void ProxyScriptDecider::OnWaitTimerFired() {
 449   OnIOCompletion(OK);
 450 }
 451
 452 void ProxyScriptDecider::DidComplete() {
 453   net_log_.EndEvent(NetLog::TYPE_PROXY_SCRIPT_DECIDER);
 454 }
 455
 456 void ProxyScriptDecider::Cancel() {
 457   DCHECK_NE(STATE_NONE, next_state_);
 458
 459   net_log_.AddEvent(NetLog::TYPE_CANCELLED);
 460
 461   switch (next_state_) {
 462     case STATE_WAIT_COMPLETE:
 463       wait_timer_.Stop();
 464       break;
 465     case STATE_FETCH_PAC_SCRIPT_COMPLETE:
 466       proxy_script_fetcher_->Cancel();
 467       break;
 468     default:
 469       break;
 470   }
 471
 472   // This is safe to call in any state.
 473   if (dhcp_proxy_script_fetcher_)
 474     dhcp_proxy_script_fetcher_->Cancel();
 475
 476   DidComplete();
 477 }
 478
 479 }  // namespace net