1 // Copyright 2015 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 "base/base64url.h" 6 7 #include <stddef.h> 8 9 #include "base/base64.h" 10 #include "base/macros.h" 11 #include "base/numerics/safe_math.h" 12 #include "base/strings/string_util.h" 13 14 #include <modp_b64/modp_b64.h> 15 16 namespace base { 17 18 const char kPaddingChar = '='; 19 20 // Base64url maps {+, /} to {-, _} in order for the encoded content to be safe 21 // to use in a URL. These characters will be translated by this implementation. 22 const char kBase64Chars[] = "+/"; 23 const char kBase64UrlSafeChars[] = "-_"; 24 25 void Base64UrlEncode(const StringPiece& input, 26 Base64UrlEncodePolicy policy, 27 std::string* output) { 28 Base64Encode(input, output); 29 30 ReplaceChars(*output, "+", "-", output); 31 ReplaceChars(*output, "/", "_", output); 32 33 switch (policy) { 34 case Base64UrlEncodePolicy::INCLUDE_PADDING: 35 // The padding included in |*output| will not be amended. 36 break; 37 case Base64UrlEncodePolicy::OMIT_PADDING: 38 // The padding included in |*output| will be removed. 39 const size_t last_non_padding_pos = 40 output->find_last_not_of(kPaddingChar); 41 if (last_non_padding_pos != std::string::npos) 42 output->resize(last_non_padding_pos + 1); 43 44 break; 45 } 46 } 47 48 bool Base64UrlDecode(const StringPiece& input, 49 Base64UrlDecodePolicy policy, 50 std::string* output) { 51 // Characters outside of the base64url alphabet are disallowed, which includes 52 // the {+, /} characters found in the conventional base64 alphabet. 53 if (input.find_first_of(kBase64Chars) != std::string::npos) 54 return false; 55 56 const size_t required_padding_characters = input.size() % 4; 57 const bool needs_replacement = 58 input.find_first_of(kBase64UrlSafeChars) != std::string::npos; 59 60 switch (policy) { 61 case Base64UrlDecodePolicy::REQUIRE_PADDING: 62 // Fail if the required padding is not included in |input|. 63 if (required_padding_characters > 0) 64 return false; 65 break; 66 case Base64UrlDecodePolicy::IGNORE_PADDING: 67 // Missing padding will be silently appended. 68 break; 69 case Base64UrlDecodePolicy::DISALLOW_PADDING: 70 // Fail if padding characters are included in |input|. 71 if (input.find_first_of(kPaddingChar) != std::string::npos) 72 return false; 73 break; 74 } 75 76 // If the string either needs replacement of URL-safe characters to normal 77 // base64 ones, or additional padding, a copy of |input| needs to be made in 78 // order to make these adjustments without side effects. 79 if (required_padding_characters > 0 || needs_replacement) { 80 std::string base64_input; 81 82 CheckedNumeric<size_t> base64_input_size = input.size(); 83 if (required_padding_characters > 0) 84 base64_input_size += 4 - required_padding_characters; 85 86 base64_input.reserve(base64_input_size.ValueOrDie()); 87 input.AppendToString(&base64_input); 88 89 // Substitute the base64url URL-safe characters to their base64 equivalents. 90 ReplaceChars(base64_input, "-", "+", &base64_input); 91 ReplaceChars(base64_input, "_", "/", &base64_input); 92 93 // Append the necessary padding characters. 94 base64_input.resize(base64_input_size.ValueOrDie(), '='); 95 96 return Base64Decode(base64_input, output); 97 } 98 99 return Base64Decode(input, output); 100 } 101 102 } // namespace base 103
