1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
|
// Copyright 2015 The Chromium Authors
// 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 <string_view>
#include "base/base64.h"
#include "base/numerics/safe_math.h"
#include "base/strings/string_util.h"
#include "third_party/modp_b64/modp_b64.h"
namespace base {
namespace {
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[] = "-_";
class StringViewOrString {
public:
explicit StringViewOrString(std::string_view piece) : piece_(piece) {}
explicit StringViewOrString(std::string str) : str_(std::move(str)) {}
std::string_view get() const {
if (str_) {
return *str_;
}
return piece_;
}
private:
const std::optional<std::string> str_;
const std::string_view piece_;
};
// Converts the base64url `input` into a plain base64 string.
std::optional<StringViewOrString> Base64UrlToBase64(
std::string_view input,
Base64UrlDecodePolicy policy) {
// 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 std::nullopt;
}
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 std::nullopt;
}
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 std::nullopt;
}
break;
}
if (required_padding_characters == 0 && !needs_replacement) {
return StringViewOrString(input);
}
// 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.
CheckedNumeric<size_t> out_size = input.size();
if (required_padding_characters > 0) {
out_size += 4 - required_padding_characters;
}
std::string base64_input;
base64_input.reserve(out_size.ValueOrDie());
base64_input.append(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(out_size.ValueOrDie(), '=');
return StringViewOrString(std::move(base64_input));
}
} // namespace
void Base64UrlEncode(span<const uint8_t> input,
Base64UrlEncodePolicy policy,
std::string* output) {
*output = Base64Encode(input);
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;
}
}
void Base64UrlEncode(std::string_view input,
Base64UrlEncodePolicy policy,
std::string* output) {
Base64UrlEncode(base::as_byte_span(input), policy, output);
}
bool Base64UrlDecode(std::string_view input,
Base64UrlDecodePolicy policy,
std::string* output) {
std::optional<StringViewOrString> base64_input =
Base64UrlToBase64(input, policy);
if (!base64_input) {
return false;
}
return Base64Decode(base64_input->get(), output);
}
std::optional<std::vector<uint8_t>> Base64UrlDecode(
std::string_view input,
Base64UrlDecodePolicy policy) {
std::optional<StringViewOrString> base64_input =
Base64UrlToBase64(input, policy);
if (!base64_input) {
return std::nullopt;
}
return Base64Decode(base64_input->get());
}
} // namespace base
|
