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
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
content / browser / web_package / signed_exchange_prologue.cc [blame]
// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "content/browser/web_package/signed_exchange_prologue.h"
#include <string_view>
#include "base/strings/string_util.h"
#include "base/strings/stringprintf.h"
#include "base/trace_event/trace_event.h"
#include "content/browser/web_package/signed_exchange_utils.h"
namespace content {
namespace {
constexpr char kSignedExchangeMagic[] = "sxg1-b3";
// size of `fallbackUrlLength` field in number of bytes.
constexpr size_t kFallbackUrlLengthFieldSizeInBytes = 2;
// size of `sigLength` field in number of bytes.
constexpr size_t kSigLengthFieldLengthInBytes = 3;
// size of `headerLength` field in number of bytes.
constexpr size_t kHeaderLengthFieldLengthInBytes = 3;
constexpr size_t kMaximumSignatureHeaderFieldLength = 16 * 1024;
constexpr size_t kMaximumCBORHeaderLength = 512 * 1024;
} // namespace
namespace signed_exchange_prologue {
const size_t BeforeFallbackUrl::kEncodedSizeInBytes =
sizeof(kSignedExchangeMagic) + kFallbackUrlLengthFieldSizeInBytes;
size_t Parse2BytesEncodedLength(base::span<const uint8_t> input) {
DCHECK_EQ(input.size(), 2u);
return static_cast<size_t>(input[0]) << 8 | static_cast<size_t>(input[1]);
}
size_t Parse3BytesEncodedLength(base::span<const uint8_t> input) {
DCHECK_EQ(input.size(), 3u);
return static_cast<size_t>(input[0]) << 16 |
static_cast<size_t>(input[1]) << 8 | static_cast<size_t>(input[2]);
}
// static
BeforeFallbackUrl BeforeFallbackUrl::Parse(
base::span<const uint8_t> input,
SignedExchangeDevToolsProxy* devtools_proxy) {
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("loading"),
"signed_exchange_prologue::BeforeFallbackUrl::Parse");
CHECK_EQ(input.size(), kEncodedSizeInBytes);
const auto magic_string = input.first(sizeof(kSignedExchangeMagic));
const auto encoded_fallback_url_length_field = input.subspan(
sizeof(kSignedExchangeMagic), kFallbackUrlLengthFieldSizeInBytes);
bool is_valid = true;
if (memcmp(magic_string.data(), kSignedExchangeMagic,
sizeof(kSignedExchangeMagic)) != 0) {
signed_exchange_utils::ReportErrorAndTraceEvent(devtools_proxy,
"Wrong magic string");
is_valid = false;
}
size_t fallback_url_length =
Parse2BytesEncodedLength(encoded_fallback_url_length_field);
return BeforeFallbackUrl(is_valid, fallback_url_length);
}
size_t BeforeFallbackUrl::ComputeFallbackUrlAndAfterLength() const {
return fallback_url_length_ + kSigLengthFieldLengthInBytes +
kHeaderLengthFieldLengthInBytes;
}
// static
FallbackUrlAndAfter FallbackUrlAndAfter::ParseFailedButFallbackUrlAvailable(
const signed_exchange_utils::URLWithRawString& fallback_url) {
return FallbackUrlAndAfter(/*is_valid=*/false, fallback_url,
/*signature_header_field_length=*/0,
/*cbor_header_length=*/0);
}
// static
FallbackUrlAndAfter FallbackUrlAndAfter::Parse(
base::span<const uint8_t> input,
const BeforeFallbackUrl& before_fallback_url,
SignedExchangeDevToolsProxy* devtools_proxy) {
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("loading"),
"signed_exchange_prologue::FallbackUrlAndAfter::Parse");
if (input.size() < before_fallback_url.fallback_url_length()) {
signed_exchange_utils::ReportErrorAndTraceEvent(
devtools_proxy,
"End of stream reached before reading the entire `fallbackUrl`.");
return FallbackUrlAndAfter();
}
std::string_view fallback_url_str(reinterpret_cast<const char*>(input.data()),
before_fallback_url.fallback_url_length());
if (!base::IsStringUTF8(fallback_url_str)) {
signed_exchange_utils::ReportErrorAndTraceEvent(
devtools_proxy, "`fallbackUrl` is not a valid UTF-8 sequence.");
return FallbackUrlAndAfter();
}
signed_exchange_utils::URLWithRawString fallback_url(fallback_url_str);
if (!fallback_url.url.is_valid()) {
signed_exchange_utils::ReportErrorAndTraceEvent(
devtools_proxy, "Failed to parse `fallbackUrl`.");
return FallbackUrlAndAfter();
}
if (!fallback_url.url.SchemeIs(url::kHttpsScheme)) {
signed_exchange_utils::ReportErrorAndTraceEvent(
devtools_proxy, "`fallbackUrl` in non-https scheme.");
return FallbackUrlAndAfter();
}
if (fallback_url.url.has_ref()) {
signed_exchange_utils::ReportErrorAndTraceEvent(
devtools_proxy, "`fallbackUrl` can't have a fragment.");
return FallbackUrlAndAfter();
}
// Note: For the code path after this comment, if parsing failed but
// the `fallbackUrl` parse had succeed, the return value can still be
// used for fallback redirect.
if (!before_fallback_url.is_valid())
return ParseFailedButFallbackUrlAvailable(fallback_url);
if (input.size() < before_fallback_url.ComputeFallbackUrlAndAfterLength()) {
signed_exchange_utils::ReportErrorAndTraceEvent(
devtools_proxy,
"End of stream reached before reading `sigLength` and `headerLength` "
"fields.");
return ParseFailedButFallbackUrlAvailable(fallback_url);
}
const auto encoded_signature_header_field_length = input.subspan(
before_fallback_url.fallback_url_length(), kSigLengthFieldLengthInBytes);
const auto encoded_cbor_header_length = input.subspan(
before_fallback_url.fallback_url_length() + kSigLengthFieldLengthInBytes,
kHeaderLengthFieldLengthInBytes);
size_t signature_header_field_length =
Parse3BytesEncodedLength(encoded_signature_header_field_length);
size_t cbor_header_length =
Parse3BytesEncodedLength(encoded_cbor_header_length);
if (signature_header_field_length > kMaximumSignatureHeaderFieldLength) {
signed_exchange_utils::ReportErrorAndTraceEvent(
devtools_proxy,
base::StringPrintf("Signature header field too long: %zu",
signature_header_field_length));
return ParseFailedButFallbackUrlAvailable(fallback_url);
}
if (cbor_header_length > kMaximumCBORHeaderLength) {
signed_exchange_utils::ReportErrorAndTraceEvent(
devtools_proxy,
base::StringPrintf("CBOR header too long: %zu", cbor_header_length));
return ParseFailedButFallbackUrlAvailable(fallback_url);
}
return FallbackUrlAndAfter(true, fallback_url, signature_header_field_length,
cbor_header_length);
}
size_t FallbackUrlAndAfter::signature_header_field_length() const {
DCHECK(is_valid());
return signature_header_field_length_;
}
size_t FallbackUrlAndAfter::cbor_header_length() const {
DCHECK(is_valid());
return cbor_header_length_;
}
size_t FallbackUrlAndAfter::ComputeFollowingSectionsLength() const {
DCHECK(is_valid());
return signature_header_field_length_ + cbor_header_length_;
}
} // namespace signed_exchange_prologue
} // namespace content