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// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/web_package/input_reader.h"
#include "base/containers/contains.h"
#include "base/numerics/checked_math.h"
#include "base/strings/string_util.h"
#include "base/strings/string_view_util.h"
#include "base/types/cxx23_to_underlying.h"
#include "components/cbor/constants.h"
#include "components/cbor/values.h"
namespace web_package {
namespace {
// This array must be kept in sync with the `CBORType` enum.
constexpr std::array kAcceptedCBORTypes = {
// clang-format off
CBORType::kUnsignedInt,
CBORType::kNegativeInt,
CBORType::kByteString,
CBORType::kTextString,
CBORType::kArray,
CBORType::kMap,
CBORType::kSimpleValue,
// clang-format on
};
std::optional<int64_t> DecodeValueToNegative(uint64_t value) {
auto negative_value = -base::CheckedNumeric<int64_t>(value) - 1;
if (!negative_value.IsValid()) {
return std::nullopt;
}
return static_cast<int64_t>(negative_value.ValueOrDie());
}
std::optional<int64_t> DecodeValueToUnsigned(uint64_t value) {
auto unsigned_value = base::CheckedNumeric<int64_t>(value);
if (!unsigned_value.IsValid()) {
return std::nullopt;
}
return static_cast<int64_t>(unsigned_value.ValueOrDie());
}
} // namespace
InputReader::InputReader(base::span<const uint8_t> buf) : buf_(buf) {}
InputReader::~InputReader() = default;
std::optional<uint8_t> InputReader::ReadByte() {
uint8_t b;
if (!buf_.ReadU8BigEndian(b)) {
return std::nullopt;
}
return {b};
}
std::optional<base::span<const uint8_t>> InputReader::ReadBytes(size_t n) {
return buf_.Read(n);
}
std::optional<std::string_view> InputReader::ReadString(size_t n) {
auto bytes = buf_.Read(n);
if (!bytes) {
return std::nullopt;
}
if (!base::IsStringUTF8(base::as_string_view(*bytes))) {
return std::nullopt;
}
return base::as_string_view(*bytes);
}
std::optional<uint64_t> InputReader::ReadCBORHeader(CBORType expected_type) {
auto pair = ReadTypeAndArgument();
if (!pair || pair->first != expected_type) {
return std::nullopt;
}
return pair->second;
}
std::optional<CBORHeader> InputReader::ReadCBORHeader() {
auto pair = ReadTypeAndArgument();
if (!pair) {
return std::nullopt;
}
const auto& [type, additional_info] = *pair;
switch (type) {
case CBORType::kSimpleValue: {
using SimpleValue = cbor::Value::SimpleValue;
if (additional_info == base::to_underlying(SimpleValue::TRUE_VALUE)) {
return {{true}};
} else if (additional_info ==
base::to_underlying(SimpleValue::FALSE_VALUE)) {
return {{false}};
} else {
return std::nullopt;
}
}
case CBORType::kUnsignedInt:
case CBORType::kNegativeInt: {
std::optional<int64_t> value =
type == CBORType::kUnsignedInt
? DecodeValueToUnsigned(additional_info)
: DecodeValueToNegative(additional_info);
if (!value) {
return std::nullopt;
}
return {{*value}};
}
case CBORType::kByteString:
case CBORType::kTextString: {
using StringInfo = CBORHeader::StringInfo;
using StringType = CBORHeader::StringInfo::StringType;
return {{StringInfo{.type = type == CBORType::kByteString
? StringType::kByteString
: StringType::kTextString,
.byte_length = additional_info}}};
}
case CBORType::kArray:
case CBORType::kMap: {
using ContainerInfo = CBORHeader::ContainerInfo;
using ContainerType = CBORHeader::ContainerInfo::ContainerType;
return {{ContainerInfo{.type = type == CBORType::kArray
? ContainerType::kArray
: ContainerType::kMap,
.size = additional_info}}};
}
}
}
// https://datatracker.ietf.org/doc/html/rfc8949.html#section-3
std::optional<std::pair<CBORType, uint64_t>>
InputReader::ReadTypeAndArgument() {
std::optional<uint8_t> first_byte = ReadByte();
if (!first_byte) {
return std::nullopt;
}
// There are more CBOR types in the standard than we accept. To avoid mishits
// during `static_cast<CBORType>`, it's safer to validate the type beforehand.
uint8_t type_byte = (*first_byte & cbor::constants::kMajorTypeMask) >>
cbor::constants::kMajorTypeBitShift;
if (!base::Contains(kAcceptedCBORTypes, type_byte,
&base::to_underlying<CBORType>)) {
return std::nullopt;
}
CBORType type = static_cast<CBORType>(type_byte);
uint8_t b = *first_byte & cbor::constants::kAdditionalInformationMask;
if (b <= 23) {
return std::make_pair(type, b);
}
if (b == 24) {
auto content = ReadByte();
if (!content || *content < 24) {
return std::nullopt;
}
return std::make_pair(type, *content);
}
if (b == 25) {
uint16_t content;
if (!ReadBigEndian(&content) || content >> 8 == 0) {
return std::nullopt;
}
return std::make_pair(type, content);
}
if (b == 26) {
uint32_t content;
if (!ReadBigEndian(&content) || content >> 16 == 0) {
return std::nullopt;
}
return std::make_pair(type, content);
}
if (b == 27) {
uint64_t content;
if (!ReadBigEndian(&content) || content >> 32 == 0) {
return std::nullopt;
}
return std::make_pair(type, content);
}
return std::nullopt;
}
} // namespace web_package
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