net/cert/pem_tokenizer.cc

   1 // Copyright (c) 2010 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/cert/pem_tokenizer.h"
   6
   7 #include "base/base64.h"
   8 #include "base/strings/string_util.h"
   9 #include "base/strings/stringprintf.h"
  10
  11 namespace {
  12
  13 const char kPEMSearchBlock[] = "-----BEGIN ";
  14 const char kPEMBeginBlock[] = "-----BEGIN %s-----";
  15 const char kPEMEndBlock[] = "-----END %s-----";
  16
  17 }  // namespace
  18
  19 namespace net {
  20
  21 using base::StringPiece;
  22
  23 struct PEMTokenizer::PEMType {
  24   std::string type;
  25   std::string header;
  26   std::string footer;
  27 };
  28
  29 PEMTokenizer::PEMTokenizer(
  30     const StringPiece& str,
  31     const std::vector<std::string>& allowed_block_types) {
  32   Init(str, allowed_block_types);
  33 }
  34
  35 PEMTokenizer::~PEMTokenizer() {
  36 }
  37
  38 bool PEMTokenizer::GetNext() {
  39   while (pos_ != StringPiece::npos) {
  40     // Scan for the beginning of the next PEM encoded block.
  41     pos_ = str_.find(kPEMSearchBlock, pos_);
  42     if (pos_ == StringPiece::npos)
  43       return false;  // No more PEM blocks
  44
  45     std::vector<PEMType>::const_iterator it;
  46     // Check to see if it is of an acceptable block type.
  47     for (it = block_types_.begin(); it != block_types_.end(); ++it) {
  48       if (!str_.substr(pos_).starts_with(it->header))
  49         continue;
  50
  51       // Look for a footer matching the header. If none is found, then all
  52       // data following this point is invalid and should not be parsed.
  53       StringPiece::size_type footer_pos = str_.find(it->footer, pos_);
  54       if (footer_pos == StringPiece::npos) {
  55         pos_ = StringPiece::npos;
  56         return false;
  57       }
  58
  59       // Chop off the header and footer and parse the data in between.
  60       StringPiece::size_type data_begin = pos_ + it->header.size();
  61       pos_ = footer_pos + it->footer.size();
  62       block_type_ = it->type;
  63
  64       StringPiece encoded = str_.substr(data_begin,
  65                                         footer_pos - data_begin);
  66       if (!base::Base64Decode(base::CollapseWhitespaceASCII(encoded.as_string(),
  67                                                             true), &data_)) {
  68         // The most likely cause for a decode failure is a datatype that
  69         // includes PEM headers, which are not supported.
  70         break;
  71       }
  72
  73       return true;
  74     }
  75
  76     // If the block did not match any acceptable type, move past it and
  77     // continue the search. Otherwise, |pos_| has been updated to the most
  78     // appropriate search position to continue searching from and should not
  79     // be adjusted.
  80     if (it == block_types_.end())
  81       pos_ += sizeof(kPEMSearchBlock);
  82   }
  83
  84   return false;
  85 }
  86
  87 void PEMTokenizer::Init(
  88     const StringPiece& str,
  89     const std::vector<std::string>& allowed_block_types) {
  90   str_ = str;
  91   pos_ = 0;
  92
  93   // Construct PEM header/footer strings for all the accepted types, to
  94   // reduce parsing later.
  95   for (std::vector<std::string>::const_iterator it =
  96        allowed_block_types.begin(); it != allowed_block_types.end(); ++it) {
  97     PEMType allowed_type;
  98     allowed_type.type = *it;
  99     allowed_type.header = base::StringPrintf(kPEMBeginBlock, it->c_str());
 100     allowed_type.footer = base::StringPrintf(kPEMEndBlock, it->c_str());
 101     block_types_.push_back(allowed_type);
 102   }
 103 }
 104
 105 }  // namespace net