Add read-only access to POST data for webRequest's onBeforeRequest

chrome/browser/extensions/api/web_request/form_data_parser.cc

+// Copyright (c) 2012 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 "chrome/browser/extensions/api/web_request/form_data_parser.h"
+
+#include "base/string_util.h"
+#include "base/values.h"
+#include "net/base/escape.h"
+#include "net/url_request/url_request.h"
+
+using base::DictionaryValue;
+using base::ListValue;
+using base::StringPiece;
+
+namespace extensions {
+
+// Implementation of FormDataParser and FormDataParser::Result .
+
+FormDataParser::Result::Result() {}
+FormDataParser::Result::~Result() {}
+
+void FormDataParser::Result::Reset() {
+  name_.erase();
+  value_.erase();
+}
+
+FormDataParser::~FormDataParser() {}
+
+// static
+scoped_ptr<FormDataParser> FormDataParser::Create(
+    const net::URLRequest* request) {
+  std::string value;
+  const bool found = request->extra_request_headers().GetHeader(
+      net::HttpRequestHeaders::kContentType, &value);
+  return Create(found ? &value : NULL);
+}
+
+// static
+scoped_ptr<FormDataParser> FormDataParser::Create(
+    const std::string* content_type_header) {
+  enum ParserChoice {kUrlEncoded, kMultipart, kError};
+  ParserChoice choice = kError;
+  std::string boundary;
+
+  if (content_type_header == NULL) {
+    choice = kUrlEncoded;
+  } else {
+    const std::string content_type(
+        content_type_header->substr(0, content_type_header->find(';')));
+
+    if (base::strcasecmp(
+        content_type.c_str(), "application/x-www-form-urlencoded") == 0) {
+      choice = kUrlEncoded;
+    } else if (base::strcasecmp(
+        content_type.c_str(), "multipart/form-data") == 0) {
+      static const char kBoundaryString[] = "boundary=";
+      size_t offset = content_type_header->find(kBoundaryString);
+      if (offset == std::string::npos) {
+        // Malformed header.
+        return scoped_ptr<FormDataParser>();
+      }
+      offset += strlen(kBoundaryString);
+      boundary = content_type_header->substr(
+          offset, content_type_header->find(';', offset));
+      if (!boundary.empty())
+        choice = kMultipart;
+    }
+  }
+  // Other cases are unparseable, including when |content_type| is "text/plain".
+
+  switch (choice) {
+    case kUrlEncoded:
+      return scoped_ptr<FormDataParser>(new FormDataParserUrlEncoded());
+    case kMultipart:
+      return scoped_ptr<FormDataParser>(new FormDataParserMultipart(boundary));
+    default:  // In other words, case kError:
+      return scoped_ptr<FormDataParser>();
+  }
+}
+
+FormDataParser::FormDataParser() {}
+
+// Implementation of FormDataParserUrlEncoded.
+
+FormDataParserUrlEncoded::FormDataParserUrlEncoded()
+    : source_(NULL),
+      aborted_(false),
+      equality_signs_(0),
+      amp_signs_(0),
+      expect_equality_(true) {
+}
+
+FormDataParserUrlEncoded::~FormDataParserUrlEncoded() {}
+
+bool FormDataParserUrlEncoded::AllDataReadOK() {
+  return source_ != NULL &&
+         !aborted_ &&
+         offset_ == source_->end() &&
+         equality_signs_ == amp_signs_ + 1;
+}
+
+bool FormDataParserUrlEncoded::GetNextNameValue(Result* result) {
+  result->Reset();
+  if (source_ == NULL || aborted_)
+    return false;
+  if (offset_ == source_->end())
+    return false;
+  const char* const name_start = &(*offset_);
+  char c;
+  bool last_read_success = GetNextChar(&c);
+  while (last_read_success && c != '=')
+    last_read_success = GetNextChar(&c);
+  if (!last_read_success) {  // This means the data is malformed.
+    Abort();
+    return false;
+  }
+  const char* const name_end = &(*(offset_ - 1));
+  const std::string encoded_name(name_start, name_end - name_start);
+  const net::UnescapeRule::Type unescape_rules =
+      net::UnescapeRule::URL_SPECIAL_CHARS | net::UnescapeRule::CONTROL_CHARS |
+      net::UnescapeRule::SPACES | net::UnescapeRule::REPLACE_PLUS_WITH_SPACE;
+  result->set_name(net::UnescapeURLComponent(encoded_name, unescape_rules));
+
+  const char* const value_start = &(*offset_);
+  last_read_success = GetNextChar(&c);
+  while (last_read_success && c != '&')
+    last_read_success = GetNextChar(&c);
+  const char* const value_end =
+      last_read_success ? &(*(offset_ - 1)) : &(*offset_);
+  const std::string encoded_value(value_start, value_end - value_start);
+  result->set_value(net::UnescapeURLComponent(encoded_value, unescape_rules));
+  return true;
+}
+
+bool FormDataParserUrlEncoded::SetSource(const std::vector<char>* source) {
+  if (source_ != NULL || source == NULL || aborted_)
+    return false;
+  source_ = source;
+  offset_ = source_->begin();
+  return true;
+}
+
+bool FormDataParserUrlEncoded::GetNextChar(char* c) {
+  if (offset_ == source_->end() || aborted_)
+    return false;
+  *c = *offset_;
+  ++offset_;
+
+  if (*c == '=') {
+    if (expect_equality_) {
+      ++equality_signs_;
+      expect_equality_ = false;
+    } else {
+      Abort();
+      return false;
+    }
+  }
+  if (*c == '&' && offset_ != source_->end()) {
+    if (!expect_equality_) {
+      ++amp_signs_;
+      expect_equality_ = true;
+    } else {
+      Abort();
+      return false;
+    }
+  }
+
+  return true;
+}
+
+void FormDataParserUrlEncoded::Abort() {
+  aborted_ = true;
+}
+
+// Implementation of FormDataParserMultipart.
+
+FormDataParserMultipart::FormDataParserMultipart(
+    const std::string& boundary_separator)
+    : source_(NULL),
+      dash_boundary_("--" + boundary_separator),
+      state_(kStart),
+      value_name_present_(false) {
+}
+
+FormDataParserMultipart::~FormDataParserMultipart() {}
+
+bool FormDataParserMultipart::AllDataReadOK() {
+  return source_ != NULL && InFinalState();
+}
+
+bool FormDataParserMultipart::GetNextNameValue(Result* result) {
+  if (!value_name_present_ || state_ == kError)
+    return false;
+  result->set_name(next_name_);
+  result->set_value(next_value_);
+  next_name_.clear();
+  next_value_.clear();
+  value_name_present_ = ReadNextNameValue();
+  return true;
+}
+
+bool FormDataParserMultipart::SetSource(const std::vector<char>* source) {
+  if (state_ == kError ||
+      source == NULL ||
+      // Message part across a source split is also an error.
+      next_name_.data() != NULL || next_value_.data() != NULL)
+    return false;
+  if (source_ != NULL && offset_ != source_->end()){
+    // Try to seek until the end. If no name-value pair is found, this is OK.
+    value_name_present_ = ReadNextNameValue();
+    if (!value_name_present_ || offset_ != source_->end())
+      return false;
+  }
+  source_ = source;
+  offset_ = source_->begin();
+  value_name_present_ = ReadNextNameValue();
+  return true;
+}
+
+// static
+char FormDataParserMultipart::kTransitionToChar[] = {
+  '\n',   // For kLF.
+  '\r',   // For kCR.
+  0,      // For kAscii.
+  0,      // For kLwsp.
+  0,      // For kDashBoundary.
+  ':',    // For kColonT.
+  '-',    // For kDash.
+  0,      // For kAny.
+};
+
+// static
+FormDataParserMultipart::Transition
+    FormDataParserMultipart::kAvailableTransitions[] = {
+  kDashBoundary, kCR, kAny,     // For kStart.
+  kLF, kAny,                    // For kCR1.
+  kCR, kAny,                    // For kIgnorePreamble.
+  kLwsp, kCR, kAny,             // For kDB1.
+  kLF, kAny,                    // For kCR2.
+  kAscii, kCR, kAny,            // For kPart.
+  kAscii, kColonT, kAny,        // For kName.
+  kLF, kCR, kAny,               // For kColonS.
+  kCR, kAscii, kAny,            // For kEnd1.
+  kLF, kCR, kAscii, kAny,       // For kEnd2.
+  kLwsp, kCR, kAscii, kAny,     // For kEnd3.
+  kLF, kAny,                    // For kCR3.
+  kDashBoundary, kCR, kAny,     // For kPreData.
+  kLF, kAny,                    // For kCR4.
+  kCR, kAny,                    // For kData.
+  kDashBoundary, kAny,          // For kData2.
+  kLwsp, kCR, kDash, kAny,      // For kDB2.
+  kDash, kAny,                  // For kD.
+  kLwsp, kCR, kAny,             // For kEnd.
+  kLF, kAny,                    // For kCR5.
+  kAny,                         // For kIgnoreEpilogue.
+  kAny                          // For kError.
+};
+
+// static
+FormDataParserMultipart::State FormDataParserMultipart::kNextState[] = {
+  kDB1, kCR1, kIgnorePreamble,   // For kStart;         size so far:    03.
+  kStart, kIgnorePreamble,       // For kCR1;                           05.
+  kCR1, kIgnorePreamble,         // For kIgnorePreamble;                07.
+  kDB1, kCR2, kError,            // For kDB1;                           10.
+  kPart, kError,                 // For kCR2;                           12.
+  kName, kCR3, kError,           // For kPart;                          15.
+  kName, kColonS, kError,        // For kName;                          18.
+  kEnd1, kEnd2, kColonS,         // For kColonS;                        21.
+  kCR3, kName, kError,           // For kEnd1;                          24.
+  kEnd3, kCR3, kName, kError,    // For kEnd2;                          28.
+  kColonS, kCR3, kName, kError,  // For kEnd3;                          32.
+  kPreData, kError,              // For kCR3;                           34.
+  kDB2, kCR3, kData,             // For kPreData;                       37.
+  kData2, kData,                 // For kCR4;                           39.
+  kCR4, kData,                   // For kData;                          41.
+  kDB2, kCR4,                    // For kData2;                         43.
+  kDB1, kCR2, kD, kError,        // For kDB2;                           47.
+  kEnd, kError,                  // For kD;                             49.
+  kEnd, kCR5, kError,            // For kEnd;                           52.
+  kIgnoreEpilogue, kError,       // For kCR5;                           54.
+  kIgnoreEpilogue,               // For kIgnoreEpilogue;                55.
+  kError                         // For kError;                         56.
+};
+
+// static
+size_t FormDataParserMultipart::kStateToTransition[] = {
+  0u,  // For kStart
+  3u,  // For kCR1
+  5u,  // For kIgnorePreamble
+  7u,  // For kDB1
+  10u, // For kCR2
+  12u, // For kPart
+  15u, // For kName
+  18u, // For kColonS
+  21u, // For kEnd1
+  24u, // For kEnd2
+  28u, // For kEnd3
+  32u, // For kCR3
+  34u, // For kPreData
+  37u, // For kCR4
+  39u, // For kData
+  41u, // For kData2
+  43u, // For kDB2
+  47u, // For kD
+  49u, // For kEnd
+  52u, // For kCR5
+  54u, // For kIgnoreEpilogue
+  55u, // For kError
+};
+
+bool FormDataParserMultipart::ReadNextNameValue() {
+  if (state_ == kError || source_ == NULL ||
+      next_name_.data() != NULL || next_value_.data() != NULL)
+    return false;
+
+  // Seek to the next part's headers.
+  while (state_ != kPart) {
+    if (!DoStep())
+      return false;
+  }
+  while (state_ != kPreData) {
+    const char* header = &(*offset_);
+    while (state_ != kColonS) {
+      if (!DoStep())
+        return false;
+    }
+    size_t header_length = 0u;
+    while (state_ != kPreData && state_ != kName) {
+      if (state_ == kEnd1 || state_ == kEnd2 || state_ == kEnd3) {
+        // The cast is safe, we know that offset only moves forward.
+        header_length = static_cast<size_t>(&(*offset_) - header);
+      }
+      if (!DoStep())
+        return false;
+    }
+    if (ParseHeader(base::StringPiece(header, header_length))) {
+      // Found what we were looking for, just skip to the part's body.
+      while (state_ != kPreData) {
+        if (!DoStep())
+          return false;
+      }
+    }
+  }
+
+  const char* body = &(*offset_);
+  size_t body_length = 0;
+  while (state_ != kDB2 && offset_ != source_->end()) {
+    if (!DoStep())
+      return false;
+    if (state_ == kCR4) {
+      // We are in the middle of which might be the CRLF starting the part
+      // separator (see the "delimiter" non-terminal from the grammar given
+      // in the header file). The cast is safe, we know that offset only moves
+      // forward and body was assigned at least 1 transition ago.
+      body_length = static_cast<size_t>(&(*offset_) - body - 1);
+    }
+  }
+  if (body_length > 0)
+    next_value_.set(body, body_length);
+  return true;
+}
+
+bool FormDataParserMultipart::DoStep() {
+  if (state_ == kError || source_ == NULL || offset_ == source_->end())
+    return false;
+  size_t transition_index = kStateToTransition[state_];
+  Transition t = kAvailableTransitions[transition_index];
+  while (t != kAny) {
+    const State s = kNextState[transition_index];
+    const size_t length = LookUp(t);
+    if (length > 0) {
+      offset_ += length;
+      state_ = s;
+      return true;
+    }
+    t = kAvailableTransitions[++transition_index];
+  }
+  // We have kAny, the default choice. Seek by one and switch the state.
+  ++offset_;
+  state_ = kNextState[transition_index];
+  return true;
+}
+
+// Contract -- the following must be true:
+//   source_ != NULL && offset_ != source.end()
+// The idea is to check this only once in the caller (DoStep()), and do not
+// repeat it here every time, as this can be called many times from one call
+// to DoStep().
+size_t FormDataParserMultipart::LookUp(FormDataParserMultipart::Transition t) {
+  const char ahead = *offset_;
+  const char first_char = kTransitionToChar[t];
+
+  // Easy case: labels corresponding to a single char.
+  if (first_char != 0)
+    return ahead == first_char ? 1u : 0u;
+
+  // Harder cases.
+  switch (t) {
+    // Multiple alternatives, 1-char long: return immediately.
+    case kAscii:
+      return (ahead >= 33 && ahead <= 126 && ahead != ':') ? 1u : 0u;
+    case kLwsp:
+      return (ahead == ' ' || ahead == '\t') ? 1u : 0u;
+
+    // Longer than 1 char: prepare work for later.
+    case kDashBoundary: {
+      const size_t length = dash_boundary_.size();
+      // The cast below is safe, we know that the difference is not negative.
+      if (static_cast<size_t>(source_->end() - offset_) < length ||
+          memcmp(dash_boundary_.c_str(), &(*offset_), length) != 0)
+        return 0u;
+      return length;
+    }
+    case kAny:
+      // We are not supposed to be asked for kAny, but this is the right answer:
+      return 1u;
+    default:  // We never get here -- the rest has already been handled above.
+      NOTREACHED();
+      return 0u;
+  }
+}
+
+bool FormDataParserMultipart::ParseHeader(const base::StringPiece& header) {
+  static const char kContentDisposition[] = "Content-Disposition:";
+  if (memcmp(header.data(), kContentDisposition,
+             strlen(kContentDisposition) != 0))
+    return false;
+  static const char kNameEquals[] = " name=\"";
+  static const char kFilenameEquals[] = " filename=\"";
+
+  // Mandatory part: find the name and set it as |next_name_|.
+  StringPiece::size_type field_offset = header.find(kNameEquals);
+  if (field_offset == StringPiece::npos)
+    return false;
+  field_offset += strlen(kNameEquals);
+  StringPiece::size_type field_end = header.find('"', field_offset);
+  if (field_end == StringPiece::npos)
+    return false;
+  next_name_.set(header.data() + field_offset, field_end - field_offset);
+
+  // Optional part: find the filename and set it as |next_value_|.
+  field_offset = header.find(kFilenameEquals);
+  if (field_offset == StringPiece::npos)
+    return true;  // This was only optional
+  field_offset += strlen(kFilenameEquals);
+  field_end = header.find('"', field_offset);
+  if (field_end == StringPiece::npos)
+    return false;  // This is a malformed header.
+  next_value_.set(header.data() + field_offset, field_end - field_offset);
+  return true;
+}
+
+}  // namespace extensions