Add parsers for the Encryption and Encryption-Key HTTP headers.

components/gcm_driver/crypto/encryption_header_parsers.cc

+// Copyright 2015 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 "components/gcm_driver/crypto/encryption_header_parsers.h"
+
+#include "base/base64.h"
+#include "base/numerics/safe_math.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "net/http/http_util.h"
+
+namespace gcm {
+
+namespace {
+
+// The default record size in bytes, as defined in section two of
+// https://tools.ietf.org/html/draft-thomson-http-encryption-01.
+const uint64_t kDefaultRecordSizeBytes = 4096;
+
+// TODO(peter): Unify the base64url implementations. https://crbug.com/536745
+bool Base64URLDecode(const base::StringPiece& input, std::string* output) {
+  // Bail on malformed strings, which already contain a '+' or a '/'. All valid
+  // strings should escape these special characters as '-' and '_',
+  // respectively.
+  if (input.find_first_of("+/") != std::string::npos)
+    return false;
+
+  base::CheckedNumeric<size_t> checked_padded_size = input.size();
+  if (input.size() % 4)
+    checked_padded_size += 4 - (input.size() % 4);
+
+  // Add padding to |input|.
+  std::string padded_input(input.begin(), input.end());
+  padded_input.resize(checked_padded_size.ValueOrDie(), '=');
+
+  // Convert to standard base64 alphabet.
+  base::ReplaceChars(padded_input, "-", "+", &padded_input);
+  base::ReplaceChars(padded_input, "_", "/", &padded_input);
+
+  return base::Base64Decode(padded_input, output);
+}
+
+// Decodes the string between |begin| and |end| using base64url, and writes the
+// decoded value to |*salt|. Returns whether the string could be decoded.
+bool ValueToDecodedString(const std::string::const_iterator& begin,
+                          const std::string::const_iterator& end,
+                          std::string* salt) {
+  const base::StringPiece value(begin, end);
+  if (value.empty())
+    return false;
+
+  return Base64URLDecode(value, salt);
+}
+
+// Parses the record size between |begin| and |end|, and writes the value to
+// |*rs|. The value must be an unsigned, 64-bit integer greater than zero that
+// does not start with a plus. Returns whether the record size was valid.
+bool RecordSizeToInt(const std::string::const_iterator& begin,
+                     const std::string::const_iterator& end,
+                     uint64_t* rs) {
+  const base::StringPiece value(begin, end);
+  if (value.empty())
+    return false;
+
+  // Parsing the "rs" parameter uses stricter semantics than parsing rules for
+  // normal integers, in that we want to reject values such as "+5" for
+  // compatibility with UAs that use other number parsing mechanisms.
+  if (value[0] == '+')
+    return false;
+
+  if (!base::StringToUint64(value, rs))
+    return false;
+
+  // The record size MUST be greater than 1.
+  return *rs > 1;
+}
+
+// Parses the string between |input_begin| and |input_end| according to the
+// extended ABNF syntax for the Encryption HTTP header, per the "parameter"
+// rule from RFC 7231 (https://tools.ietf.org/html/rfc7231).
+//
+// encryption_params = [ parameter *( ";" parameter ) ]
+//
+// This implementation applies the parameters defined in section 3.1 of the
+// HTTP encryption encoding document:
+//
+// https://tools.ietf.org/html/draft-thomson-http-encryption-01#section-3.1
+//
+// This means that the three supported parameters are:
+//
+//     [ "keyid" "=" string ]
+//     [ ";" "salt" "=" base64url ]
+//     [ ";" "rs" "=" octet-count ]
+bool ParseEncryptionHeaderValuesImpl(std::string::const_iterator input_begin,
+                                     std::string::const_iterator input_end,
+                                     EncryptionHeaderValues* values) {
+  net::HttpUtil::NameValuePairsIterator name_value_pairs(
+      input_begin, input_end, ';',
+      net::HttpUtil::NameValuePairsIterator::VALUES_NOT_OPTIONAL);
+
+  while (name_value_pairs.GetNext()) {
+    const base::StringPiece name(name_value_pairs.name_begin(),
+                                 name_value_pairs.name_end());
+
+    if (base::LowerCaseEqualsASCII(name, "keyid")) {
+      values->keyid.assign(name_value_pairs.value_begin(),
+                           name_value_pairs.value_end());
+    } else if (base::LowerCaseEqualsASCII(name, "salt")) {
+      if (!ValueToDecodedString(name_value_pairs.value_begin(),
+                                name_value_pairs.value_end(), &values->salt)) {
+        return false;
+      }
+    } else if (base::LowerCaseEqualsASCII(name, "rs")) {
+      if (!RecordSizeToInt(name_value_pairs.value_begin(),
+                           name_value_pairs.value_end(), &values->rs)) {
+        return false;
+      }
+    } else {
+      // Silently ignore unknown directives for forward compatibility.
+    }
+  }
+
+  return name_value_pairs.valid();
+}
+
+// Parses the string between |input_begin| and |input_end| according to the
+// extended ABNF syntax for the Encryption-Key HTTP header, per the "parameter"
+// rule from RFC 7231 (https://tools.ietf.org/html/rfc7231).
+//
+// encryption_params = [ parameter *( ";" parameter ) ]
+//
+// This implementation applies the parameters defined in section 4 of the
+// HTTP encryption encoding document:
+//
+//https://tools.ietf.org/html/draft-thomson-http-encryption-01#section-4
+//
+// This means that the three supported parameters are:
+//
+//     [ "keyid" "=" string ]
+//     [ ";" "key" "=" base64url ]
+//     [ ";" "dh" "=" base64url ]
+bool ParseEncryptionKeyHeaderValuesImpl(std::string::const_iterator input_begin,
+                                        std::string::const_iterator input_end,
+                                        EncryptionKeyHeaderValues* values) {
+  net::HttpUtil::NameValuePairsIterator name_value_pairs(
+      input_begin, input_end, ';',
+      net::HttpUtil::NameValuePairsIterator::VALUES_NOT_OPTIONAL);
+
+  while (name_value_pairs.GetNext()) {
+    const base::StringPiece name(name_value_pairs.name_begin(),
+                                 name_value_pairs.name_end());
+
+    if (base::LowerCaseEqualsASCII(name, "keyid")) {
+      values->keyid.assign(name_value_pairs.value_begin(),
+                           name_value_pairs.value_end());
+    } else if (base::LowerCaseEqualsASCII(name, "key")) {
+      if (!ValueToDecodedString(name_value_pairs.value_begin(),
+                                name_value_pairs.value_end(), &values->key)) {
+        return false;
+      }
+    } else if (base::LowerCaseEqualsASCII(name, "dh")) {
+      if (!ValueToDecodedString(name_value_pairs.value_begin(),
+                                name_value_pairs.value_end(), &values->dh)) {
+        return false;
+      }
+    } else {
+      // Silently ignore unknown directives for forward compatibility.
+    }
+  }
+
+  return name_value_pairs.valid();
+}
+
+}  // namespace
+
+bool ParseEncryptionHeader(const std::string& input,
+                           std::vector<EncryptionHeaderValues>* values) {
+  DCHECK(values);
+
+  std::vector<EncryptionHeaderValues> candidate_values;
+
+  net::HttpUtil::ValuesIterator value_iterator(input.begin(), input.end(), ',');
+  while (value_iterator.GetNext()) {
+    EncryptionHeaderValues candidate_value;
+    candidate_value.rs = kDefaultRecordSizeBytes;
+
+    if (!ParseEncryptionHeaderValuesImpl(value_iterator.value_begin(),
+                                         value_iterator.value_end(),
+                                         &candidate_value)) {
+      return false;
+    }
+
+    candidate_values.push_back(candidate_value);
+  }
+
+  values->swap(candidate_values);
+  return true;
+}
+
+bool ParseEncryptionKeyHeader(const std::string& input,
+                              std::vector<EncryptionKeyHeaderValues>* values) {
+  DCHECK(values);
+
+  std::vector<EncryptionKeyHeaderValues> candidate_values;
+
+  net::HttpUtil::ValuesIterator value_iterator(input.begin(), input.end(), ',');
+  while (value_iterator.GetNext()) {
+    EncryptionKeyHeaderValues candidate_value;
+    if (!ParseEncryptionKeyHeaderValuesImpl(value_iterator.value_begin(),
+                                            value_iterator.value_end(),
+                                            &candidate_value)) {
+      return false;
+    }
+
+    candidate_values.push_back(candidate_value);
+  }
+
+  values->swap(candidate_values);
+  return true;
+}
+
+}  // namespace gcm