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 <vector>
+
+#include "base/string_util.h"
+#include "base/values.h"
+#include "net/base/escape.h"
+#include "net/url_request/url_request.h"
+#include "third_party/re2/re2/re2.h"
+
+using base::DictionaryValue;
+using base::ListValue;
+using base::StringPiece;
+using re2::RE2;
+
+namespace extensions {
+
+// Parses URLencoded forms, see
+// http://www.w3.org/TR/REC-html40-971218/interact/forms.html#h-17.13.4.1 .
+class FormDataParserUrlEncoded : public FormDataParser {
+ public:
+  FormDataParserUrlEncoded();
+  virtual ~FormDataParserUrlEncoded();
+
+  // Implementation of FormDataParser.
+  virtual bool AllDataReadOK() OVERRIDE;
+  virtual bool GetNextNameValue(Result* result) OVERRIDE;
+  virtual bool SetSource(const base::StringPiece& source) OVERRIDE;
+
+ private:
+  // The pattern to match a single name-value pair. Ideally this should be
+  // static, so that it is constructed only once, independently on how many
+  // parser instances we have. However, then we would run into exit-time
+  // destructors problems.
+  const RE2 pattern_;
+
+  static const size_t args_size_ = 2u;  // Auxiliary constant for using RE2.
+  static const net::UnescapeRule::Type unescape_rules_;
+
+  re2::StringPiece source_;
+  bool source_set_;
+
+  // Auxiliary store for using RE2.
+  std::string name_;
+  std::string value_;
+  const RE2::Arg arg_name_;
+  const RE2::Arg arg_value_;
+  const RE2::Arg* args_[args_size_];
+
+  DISALLOW_COPY_AND_ASSIGN(FormDataParserUrlEncoded);
+};
+
+// The following class, FormDataParserMultipart, parses forms encoded as
+// multipart, defined in RFCs 2388 (specific to forms), 2046 (multipart
+// encoding) and 5322 (MIME-headers).
+//
+// Implementation details
+//
+// The original grammar from RFC 2046 is this, "multipart-body" being the root
+// non-terminal:
+//
+// boundary := 0*69<bchars> bcharsnospace
+// bchars := bcharsnospace / " "
+// bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" / "+" / "_" / ","
+//                  / "-" / "." / "/" / ":" / "=" / "?"
+// dash-boundary := "--" boundary
+// multipart-body := [preamble CRLF]
+//                        dash-boundary transport-padding CRLF
+//                        body-part *encapsulation
+//                        close-delimiter transport-padding
+//                        [CRLF epilogue]
+// transport-padding := *LWSP-char
+// encapsulation := delimiter transport-padding CRLF body-part
+// delimiter := CRLF dash-boundary
+// close-delimiter := delimiter "--"
+// preamble := discard-text
+// epilogue := discard-text
+// discard-text := *(*text CRLF) *text
+// body-part := MIME-part-headers [CRLF *OCTET]
+// OCTET := <any 0-255 octet value>
+//
+// Uppercase non-terminals are defined in RFC 5234, Appendix B.1; i.e. CRLF,
+// DIGIT, and ALPHA stand for "\r\n", '0'-'9' and the set of letters of the
+// English alphabet, respectively.
+// The non-terminal "text" is presumably just any text, excluding line breaks.
+// The non-terminal "LWSP-char" is not directly defined in the original grammar
+// but it means "linear whitespace", which is a space or a horizontal tab.
+// The non-terminal "MIME-part-headers" is not discussed in RFC 2046, so we use
+// the syntax for "optional fields" from Section 3.6.8 of RFC 5322:
+//
+// MIME-part-headers := field-name ":" unstructured CRLF
+// field-name := 1*ftext
+// ftext := %d33-57 /          ; Printable US-ASCII
+//          %d59-126           ;  characters not including ":".
+// Based on Section 2.2.1 of RFC 5322, "unstructured" matches any string which
+// does not contain a CRLF sub-string, except for substrings "CRLF<space>" and
+// "CRLF<horizontal tab>", which serve for "folding".
+//
+// The FormDataParseMultipart class reads the input source and tries to parse it
+// according to the grammar above, rooted at the "multipart-body" non-terminal.
+// This happens in stages:
+//
+// 1. The optional preamble and the initial dash-boundary with transport padding
+// and a CRLF are read and ignored.
+//
+// 2. Repeatedly each body part is read. The body parts can either serve to
+//    upload a file, or just a string of bytes.
+// 2.a. The headers of that part are searched for the "content-disposition"
+//      header, which contains the name of the value represented by that body
+//      part. If the body-part is for file upload, that header also contains a
+//      filename.
+// 2.b. The "*OCTET" part of the body part is then read and passed as the value
+//      of the name-value pair for body parts representing a string of bytes.
+//      For body parts for uploading a file the "*OCTET" part is just ignored
+//      and the filename is used for value instead.
+//
+// 3. The final close-delimiter and epilogue are read and ignored.
+//
+// IMPORTANT NOTE
+// This parser supports multiple sources, i.e., SetSource can be called multiple
+// times if the input is spread over several byte blocks. However, the split
+// may only occur inside a body part, right after the trailing CRLF of headers.
+class FormDataParserMultipart : public FormDataParser {
+ public:
+  explicit FormDataParserMultipart(const std::string& boundary_separator);
+  virtual ~FormDataParserMultipart();
+
+  // Implementation of FormDataParser.
+  virtual bool AllDataReadOK() OVERRIDE;
+  virtual bool GetNextNameValue(Result* result) OVERRIDE;
+  virtual bool SetSource(const base::StringPiece& source) OVERRIDE;
+
+ private:
+  enum State {
+    STATE_INIT,      // No input read yet.
+    STATE_READY,     // Ready to call GetNextNameValue.
+    STATE_FINISHED,  // Read the input until the end.
+    STATE_SUSPEND,   // Waiting until a new |source_| is set.
+    STATE_ERROR
+  };
+
+  // Produces a regexp to match the |boundary| string.
+  static std::string GetDashBoundaryPattern(const std::string& boundary);
+
+  // Tests whether |input| has a prefix matching |pattern|.
+  static bool LookAhead(const RE2& pattern, const re2::StringPiece& input);
+
+  // If source_ starts with a header, consumes it. If the header is
+  // Content-Disposition, it also extracts |name| from "name=" and possibly
+  // |value| from "filename=" fields of that header. It only touches |name| or
+  // |value| if it finds the respective fields for them. Returns true if it
+  // consumed a header, false if it did not. Sets |value_assigned| to true if it
+  // has assigned to value, otherwise it sets it to false.
+  bool TryReadHeader(base::StringPiece* name,
+                     base::StringPiece* value,
+                     bool* value_assigned);
+
+  // Helper to GetNextNameValue. Attempts to read the data portion of a body
+  // part. If |value| is not NULL but empty, it sets it to contain the data
+  // portion. Returns true when the reading was successful.
+  bool GetNextNameValueContinue(base::StringPiece* value);
+
+  // Ideally those should be static, so that they are constructed only once,
+  // independently on how many parser instances we have. However, then we would
+  // run into exit-time destructors problems.
+  const RE2 transfer_padding_pattern_;
+  const RE2 crlf_pattern_;
+  const RE2 closing_pattern_;
+  const RE2 epilogue_pattern_;
+  const RE2 crlf_free_pattern_;
+  const RE2 preamble_pattern_;
+  const RE2 header_pattern_;
+  const RE2 content_disposition_pattern_;
+  const RE2 name_pattern_;
+  const RE2 value_pattern_;
+
+  const RE2 dash_boundary_pattern_;
+
+  // Because of initialisation dependency, |state_| needs to be declared after
+  // |dash_boundary_pattern_|.
+  State state_;
+
+  // The parsed message can be split into multiple sources which we read
+  // sequentially.
+  re2::StringPiece source_;
+
+  DISALLOW_COPY_AND_ASSIGN(FormDataParserMultipart);
+};
+
+// 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 {URL_ENCODED, MULTIPART, ERROR_CHOICE};
+  ParserChoice choice = ERROR_CHOICE;
+  std::string boundary;
+
+  if (content_type_header == NULL) {
+    choice = URL_ENCODED;
+  } 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 = URL_ENCODED;
+    } 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 += sizeof(kBoundaryString) - 1;
+      boundary = content_type_header->substr(
+          offset, content_type_header->find(';', offset));
+      if (!boundary.empty())
+        choice = MULTIPART;
+    }
+  }
+  // Other cases are unparseable, including when |content_type| is "text/plain".
+
+  switch (choice) {
+    case URL_ENCODED:
+      return scoped_ptr<FormDataParser>(new FormDataParserUrlEncoded());
+    case MULTIPART:
+      return scoped_ptr<FormDataParser>(new FormDataParserMultipart(boundary));
+    default:  // In other words, case ERROR_CHOICE:
+      return scoped_ptr<FormDataParser>();
+  }
+}
+
+FormDataParser::FormDataParser() {}
+
+// Implementation of FormDataParserUrlEncoded.
+
+const net::UnescapeRule::Type FormDataParserUrlEncoded::unescape_rules_ =
+    net::UnescapeRule::URL_SPECIAL_CHARS | net::UnescapeRule::CONTROL_CHARS |
+    net::UnescapeRule::SPACES | net::UnescapeRule::REPLACE_PLUS_WITH_SPACE;
+
+FormDataParserUrlEncoded::FormDataParserUrlEncoded()
+    : pattern_("([^=]*)=([^&]*)&?"),
+      source_(NULL),
+      source_set_(false),
+      arg_name_(&name_),
+      arg_value_(&value_) {
+  args_[0] = &arg_name_;
+  args_[1] = &arg_value_;
+}
+
+FormDataParserUrlEncoded::~FormDataParserUrlEncoded() {}
+
+bool FormDataParserUrlEncoded::AllDataReadOK() {
+  // All OK means we read the whole source.
+  return source_set_ && source_.size() == 0;
+}
+
+bool FormDataParserUrlEncoded::GetNextNameValue(Result* result) {
+  if (!source_set_)
+    return false;
+
+  bool success = RE2::ConsumeN(&source_, pattern_, args_, args_size_);
+  if (success) {
+    result->set_name(net::UnescapeURLComponent(name_, unescape_rules_));
+    result->set_value(net::UnescapeURLComponent(value_, unescape_rules_));
+  }
+  return success;
+}
+
+bool FormDataParserUrlEncoded::SetSource(const base::StringPiece& source) {
+  if (source_set_)
+    return false;  // We do not allow multiple sources for this parser.
+  source_.set(source.data(), source.size());
+  source_set_ = true;
+  return true;
+}
+
+// Implementation of FormDataParserMultipart.
+
+// static
+std::string FormDataParserMultipart::GetDashBoundaryPattern(
+    const std::string& boundary) {
+  static const char escape_closing_quote[] = "\\\\E";
+  static const RE2 unquote_pattern(escape_closing_quote);

[vabr (Chromium), 2012/08/30 12:26:48]

Note to myself -- make this a non-static data member.
(This instance slipped through during the recent removal of static data-members
with non-trivial destructors.)

+#define OPEN_QUOTE "\\Q"
+  static const char opening_quote[] = OPEN_QUOTE;
+  static const char closing_quote[] = "\\E";
+
+  std::string output(OPEN_QUOTE "--");  // Let us start with the "--".
+#undef OPEN_QUOTE
+  re2::StringPiece seek_unquote(boundary);
+  const char* copy_start = boundary.data();
+  size_t copy_length = boundary.size();
+  while (RE2::FindAndConsume(&seek_unquote, unquote_pattern)) {
+    copy_length = seek_unquote.data() - copy_start;
+    output.append(copy_start, copy_length);
+    output.append(escape_closing_quote);
+    output.append(opening_quote);
+    copy_start = seek_unquote.data();
+  }
+  copy_length = (boundary.data() + boundary.size()) - copy_start;
+  output.append(copy_start, copy_length);
+  output.append(closing_quote);
+  return output;
+}
+
+// static
+bool FormDataParserMultipart::LookAhead(const RE2& pattern,
+                                        const re2::StringPiece& input) {
+  return pattern.Match(input, 0, input.size(), RE2::ANCHOR_START, NULL, 0);
+}
+
+#define CONTENT_DISPOSITION "content-disposition:"
+FormDataParserMultipart::FormDataParserMultipart(
+    const std::string& boundary_separator)
+    : transfer_padding_pattern_("[ \\t]*\\r\\n"),
+      crlf_pattern_("\\r\\n"),
+      closing_pattern_("--[ \\t]*"),
+      epilogue_pattern_("|\\r\\n(?s:.)*"),
+      crlf_free_pattern_("(?:[^\\r]|\\r+[^\\r\\n])*"),
+      preamble_pattern_(".*?"),
+      header_pattern_("[!-9;-~]+:(.|\\r\\n[\\t ])*\\r\\n"),
+      content_disposition_pattern_("(?i:" CONTENT_DISPOSITION ")"),
+      name_pattern_("\\bname=\"([^\"]*)\""),
+      value_pattern_("\\bfilename=\"([^\"]*)\""),
+      dash_boundary_pattern_(GetDashBoundaryPattern(boundary_separator)),
+      state_(dash_boundary_pattern_.ok() ? STATE_INIT : STATE_ERROR) {}
+
+FormDataParserMultipart::~FormDataParserMultipart() {}
+
+bool FormDataParserMultipart::AllDataReadOK() {
+  return state_ == STATE_FINISHED;
+}
+
+bool FormDataParserMultipart::GetNextNameValueContinue(
+    base::StringPiece* value) {
+  const char* data_start = source_.data();
+  while (!LookAhead(dash_boundary_pattern_, source_)) {
+    if (!RE2::Consume(&source_, crlf_free_pattern_) ||
+        !RE2::Consume(&source_, crlf_pattern_)) {
+      state_ = STATE_ERROR;
+      return false;
+    }
+  }
+  if (value != NULL) {
+    if (source_.data() == data_start) {
+      // No data in this body part.
+      state_ = STATE_ERROR;
+      return false;
+    }
+    // Subtract 2u for the trailing "\r\n".
+    value->set(data_start, source_.data() - data_start - 2u);
+  }
+
+  // Finally, read the dash-boundary and either skip to the next body part, or
+  // finish reading the source.
+  CHECK(RE2::Consume(&source_, dash_boundary_pattern_));
+  if (LookAhead(closing_pattern_, source_)) {
+    CHECK(RE2::Consume(&source_, closing_pattern_));
+    if (RE2::Consume(&source_, epilogue_pattern_))
+      state_ = STATE_FINISHED;
+    else
+      state_ = STATE_ERROR;
+  } else {  // Next body part ahead.
+    if (!RE2::Consume(&source_, transfer_padding_pattern_))
+      state_ = STATE_ERROR;
+  }
+  return state_ != STATE_ERROR;
+}
+
+bool FormDataParserMultipart::GetNextNameValue(Result* result) {
+  if (source_.size() == 0 || state_ != STATE_READY)
+    return false;
+
+  // 1. Read body-part headers.
+  base::StringPiece name;
+  base::StringPiece value;
+  bool value_assigned = false;
+  bool value_assigned_temp;
+  while (TryReadHeader(&name, &value, &value_assigned_temp))
+    value_assigned |= value_assigned_temp;
+  if (name.size() == 0) {
+    state_ = STATE_ERROR;
+    return false;
+  }
+
+  // 2. Read the trailing CRLF after headers.
+  if (!RE2::Consume(&source_, crlf_pattern_)) {
+    state_ = STATE_ERROR;
+    return false;
+  }
+
+  // 3. Read the data of this body part, i.e., everything until the first
+  // dash-boundary.
+  bool return_value = true;
+  if (value_assigned && source_.size() == 0)  // Wait for a new source?
+    state_ = STATE_SUSPEND;
+  else
+    return_value = GetNextNameValueContinue(value_assigned ? NULL : &value);
+
+  result->set_name(name);
+  result->set_value(value);
+
+  return return_value;
+}
+
+bool FormDataParserMultipart::SetSource(const base::StringPiece& source) {
+  if (source.data() == NULL || source_.size() != 0)
+    return false;
+  source_.set(source.data(), source.size());
+
+  switch (state_) {
+    case STATE_INIT:
+      // Seek behind the preamble.
+      while (!LookAhead(dash_boundary_pattern_, source_)) {
+        if (!RE2::Consume(&source_, preamble_pattern_)) {
+          state_ = STATE_ERROR;
+          break;
+        }
+      }
+      // Read dash-boundary, transfer padding, and CRLF.
+      if (state_ != STATE_ERROR) {
+        if (!RE2::Consume(&source_, dash_boundary_pattern_) ||
+            !RE2::Consume(&source_, transfer_padding_pattern_))
+          state_ = STATE_ERROR;
+        else
+          state_ = STATE_READY;
+      }
+      break;
+    case STATE_READY:  // Nothing to do.
+      break;
+    case STATE_SUSPEND:
+      state_ = GetNextNameValueContinue(NULL) ? STATE_READY : STATE_ERROR;
+      break;
+    default:
+      state_ = STATE_ERROR;
+  }
+  return state_ != STATE_ERROR;
+}
+
+bool FormDataParserMultipart::TryReadHeader(base::StringPiece* name,
+                                            base::StringPiece* value,
+                                            bool* value_assigned) {
+  static const size_t content_disposition_value_offset =
+      sizeof(CONTENT_DISPOSITION) - 1;
+#undef CONTENT_DISPOSITION
+
+  *value_assigned = false;
+  const char* header_start = source_.data();
+  if (!RE2::Consume(&source_, header_pattern_))
+    return false;
+  // (*) After this point we must return true, because we consumed one header.
+
+  // Subtract 2u for the trailing "\r\n".
+  re2::StringPiece header(header_start, source_.data() - header_start - 2u);
+
+  // Now we check whether |header| is a Content-Disposition header, and try
+  // to extract name and possibly value from it.
+  if (LookAhead(content_disposition_pattern_, header)) {
+    re2::StringPiece groups[2u];
+
+    if (!name_pattern_.Match(header,
+                            content_disposition_value_offset, header.size(),
+                            RE2::UNANCHORED, groups, 2)) {
+      state_ = STATE_ERROR;
+      return true;  // See (*) for why true.
+    }
+    name->set(groups[1].data(), groups[1].size());
+
+    if (!value_pattern_.Match(header,
+                             content_disposition_value_offset, header.size(),
+                             RE2::UNANCHORED, groups, 2))
+      return true;  // See (*) for why true.
+    value->set(groups[1].data(), groups[1].size());
+    *value_assigned = true;
+  }
+  return true;
+}
+
+}  // namespace extensions