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// 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 "base/base64url.h"
#include <stddef.h>
#include "base/base64.h"
#include "base/macros.h"
#include "base/numerics/safe_math.h"
#include "base/strings/string_util.h"
#include "third_party/modp_b64/modp_b64.h"
namespace base {
const char kPaddingChar = '=';
// Base64url maps {+, /} to {-, _} in order for the encoded content to be safe
// to use in a URL. These characters will be translated by this implementation.
const char kBase64Chars[] = "+/";
const char kBase64UrlSafeChars[] = "-_";
void Base64UrlEncode(const StringPiece& input,
Base64UrlEncodePolicy policy,
std::string* output) {
Base64Encode(input, output);
ReplaceChars(*output, "+", "-", output);
ReplaceChars(*output, "/", "_", output);
switch (policy) {
case Base64UrlEncodePolicy::INCLUDE_PADDING:
// The padding included in |*output| will not be amended.
break;
case Base64UrlEncodePolicy::OMIT_PADDING:
// The padding included in |*output| will be removed.
const size_t last_non_padding_pos =
output->find_last_not_of(kPaddingChar);
if (last_non_padding_pos != std::string::npos)
output->resize(last_non_padding_pos + 1);
break;
}
}
bool Base64UrlDecode(const StringPiece& input,
Base64UrlDecodePolicy policy,
std::string* output) {
// Characters outside of the base64url alphabet are disallowed, which includes
// the {+, /} characters found in the conventional base64 alphabet.
if (input.find_first_of(kBase64Chars) != std::string::npos)
return false;
const size_t required_padding_characters = input.size() % 4;
const bool needs_replacement =
input.find_first_of(kBase64UrlSafeChars) != std::string::npos;
switch (policy) {
case Base64UrlDecodePolicy::REQUIRE_PADDING:
// Fail if the required padding is not included in |input|.
if (required_padding_characters > 0)
return false;
break;
case Base64UrlDecodePolicy::IGNORE_PADDING:
// Missing padding will be silently appended.
break;
case Base64UrlDecodePolicy::DISALLOW_PADDING:
// Fail if padding characters are included in |input|.
if (input.find_first_of(kPaddingChar) != std::string::npos)
return false;
break;
}
// If the string either needs replacement of URL-safe characters to normal
// base64 ones, or additional padding, a copy of |input| needs to be made in
// order to make these adjustments without side effects.
if (required_padding_characters > 0 || needs_replacement) {
std::string base64_input;
CheckedNumeric<size_t> base64_input_size = input.size();
if (required_padding_characters > 0)
base64_input_size += 4 - required_padding_characters;
base64_input.reserve(base64_input_size.ValueOrDie());
input.AppendToString(&base64_input);
// Substitute the base64url URL-safe characters to their base64 equivalents.
ReplaceChars(base64_input, "-", "+", &base64_input);
ReplaceChars(base64_input, "_", "/", &base64_input);
// Append the necessary padding characters.
base64_input.resize(base64_input_size.ValueOrDie(), '=');
return Base64Decode(base64_input, output);
}
return Base64Decode(input, output);
}
} // namespace base
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