348 lines
8.8 KiB
C++
348 lines
8.8 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This code is made available to you under your choice of the following sets
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* of licensing terms:
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*/
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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/* Copyright 2013 Mozilla Contributors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef mozilla_pkix_Input_h
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#define mozilla_pkix_Input_h
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#include <algorithm>
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#include "pkix/Result.h"
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#include "stdint.h"
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namespace mozilla { namespace pkix {
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class Reader;
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// An Input is a safety-oriented immutable weak reference to a array of bytes
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// of a known size. The data can only be legally accessed by constructing a
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// Reader object, which guarantees all accesses to the data are memory safe.
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// Neither Input not Reader provide any facilities for modifying the data
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// they reference.
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//
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// Inputs are small and should usually be passed by value, not by reference,
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// though for inline functions the distinction doesn't matter:
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//
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// Result GoodExample(Input input);
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// Result BadExample(const Input& input);
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// Result WorseExample(const uint8_t* input, size_t len);
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//
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// Note that in the example, GoodExample has the same performance
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// characteristics as WorseExample, but with much better safety guarantees.
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class Input final
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{
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public:
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typedef uint16_t size_type;
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// This constructor is useful for inputs that are statically known to be of a
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// fixed size, e.g.:
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//
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// static const uint8_t EXPECTED_BYTES[] = { 0x00, 0x01, 0x02 };
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// const Input expected(EXPECTED_BYTES);
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//
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// This is equivalent to (and preferred over):
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//
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// static const uint8_t EXPECTED_BYTES[] = { 0x00, 0x01, 0x02 };
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// Input expected;
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// Result rv = expected.Init(EXPECTED_BYTES, sizeof EXPECTED_BYTES);
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template <size_type N>
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explicit Input(const uint8_t (&data)[N])
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: data(data)
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, len(N)
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{
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}
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// Construct a valid, empty, Init-able Input.
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Input()
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: data(nullptr)
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, len(0u)
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{
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}
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// This is intentionally not explicit in order to allow value semantics.
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Input(const Input&) = default;
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// Initialize the input. data must be non-null and len must be less than
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// 65536. Init may not be called more than once.
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Result Init(const uint8_t* data, size_t len)
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{
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if (this->data) {
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// already initialized
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return Result::FATAL_ERROR_INVALID_ARGS;
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}
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if (!data || len > 0xffffu) {
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// input too large
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return Result::ERROR_BAD_DER;
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}
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this->data = data;
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this->len = len;
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return Success;
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}
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// Initialize the input to be equivalent to the given input. Init may not be
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// called more than once.
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//
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// This is basically operator=, but it wasn't given that name because
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// normally callers do not check the result of operator=, and normally
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// operator= can be used multiple times.
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Result Init(Input other)
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{
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return Init(other.data, other.len);
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}
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// Returns the length of the input.
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//
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// Having the return type be size_type instead of size_t avoids the need for
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// callers to ensure that the result is small enough.
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size_type GetLength() const { return static_cast<size_type>(len); }
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// Don't use this. It is here because we have some "friend" functions that we
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// don't want to declare in this header file.
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const uint8_t* UnsafeGetData() const { return data; }
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private:
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const uint8_t* data;
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size_t len;
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void operator=(const Input&) = delete; // Use Init instead.
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};
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inline bool
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InputsAreEqual(const Input& a, const Input& b)
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{
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return a.GetLength() == b.GetLength() &&
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std::equal(a.UnsafeGetData(), a.UnsafeGetData() + a.GetLength(), b.UnsafeGetData());
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}
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// An Reader is a cursor/iterator through the contents of an Input, designed to
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// maximize safety during parsing while minimizing the performance cost of that
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// safety. In particular, all methods do strict bounds checking to ensure
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// buffer overflows are impossible, and they are all inline so that the
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// compiler can coalesce as many of those checks together as possible.
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//
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// In general, Reader allows for one byte of lookahead and no backtracking.
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// However, the Match* functions internally may have more lookahead.
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class Reader final
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{
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public:
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Reader()
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: input(nullptr)
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, end(nullptr)
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{
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}
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explicit Reader(Input input)
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: input(input.UnsafeGetData())
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, end(input.UnsafeGetData() + input.GetLength())
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{
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}
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Result Init(Input input)
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{
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if (this->input) {
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return Result::FATAL_ERROR_INVALID_ARGS;
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}
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this->input = input.UnsafeGetData();
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this->end = input.UnsafeGetData() + input.GetLength();
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return Success;
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}
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bool Peek(uint8_t expectedByte) const
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{
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return input < end && *input == expectedByte;
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}
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Result Read(uint8_t& out)
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{
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Result rv = EnsureLength(1);
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if (rv != Success) {
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return rv;
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}
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out = *input++;
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return Success;
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}
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Result Read(uint16_t& out)
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{
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Result rv = EnsureLength(2);
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if (rv != Success) {
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return rv;
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}
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out = *input++;
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out <<= 8u;
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out |= *input++;
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return Success;
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}
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template <Input::size_type N>
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bool MatchRest(const uint8_t (&toMatch)[N])
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{
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// Normally we use EnsureLength which compares (input + len < end), but
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// here we want to be sure that there is nothing following the matched
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// bytes
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if (static_cast<size_t>(end - input) != N) {
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return false;
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}
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if (!std::equal(input, end, toMatch)) {
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return false;
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}
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input = end;
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return true;
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}
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bool MatchRest(Input toMatch)
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{
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// Normally we use EnsureLength which compares (input + len < end), but
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// here we want to be sure that there is nothing following the matched
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// bytes
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size_t remaining = static_cast<size_t>(end - input);
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if (toMatch.GetLength() != remaining) {
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return false;
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}
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if (!std::equal(input, end, toMatch.UnsafeGetData())) {
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return false;
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}
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input = end;
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return true;
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}
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Result Skip(Input::size_type len)
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{
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Result rv = EnsureLength(len);
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if (rv != Success) {
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return rv;
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}
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input += len;
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return Success;
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}
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Result Skip(Input::size_type len, Reader& skipped)
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{
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Result rv = EnsureLength(len);
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if (rv != Success) {
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return rv;
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}
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rv = skipped.Init(input, len);
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if (rv != Success) {
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return rv;
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}
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input += len;
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return Success;
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}
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Result Skip(Input::size_type len, /*out*/ Input& skipped)
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{
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Result rv = EnsureLength(len);
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if (rv != Success) {
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return rv;
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}
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rv = skipped.Init(input, len);
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if (rv != Success) {
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return rv;
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}
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input += len;
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return Success;
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}
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void SkipToEnd()
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{
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input = end;
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}
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Result SkipToEnd(/*out*/ Input& skipped)
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{
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return Skip(static_cast<Input::size_type>(end - input), skipped);
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}
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Result EnsureLength(Input::size_type len)
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{
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if (static_cast<size_t>(end - input) < len) {
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return Result::ERROR_BAD_DER;
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}
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return Success;
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}
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bool AtEnd() const { return input == end; }
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class Mark final
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{
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public:
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Mark(const Mark&) = default; // Intentionally not explicit.
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private:
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friend class Reader;
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Mark(const Reader& input, const uint8_t* mark) : input(input), mark(mark) { }
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const Reader& input;
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const uint8_t* const mark;
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void operator=(const Mark&) = delete;
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};
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Mark GetMark() const { return Mark(*this, input); }
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Result GetInput(const Mark& mark, /*out*/ Input& item)
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{
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if (&mark.input != this || mark.mark > input) {
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return NotReached("invalid mark", Result::FATAL_ERROR_INVALID_ARGS);
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}
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return item.Init(mark.mark,
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static_cast<Input::size_type>(input - mark.mark));
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}
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private:
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Result Init(const uint8_t* data, Input::size_type len)
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{
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if (input) {
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// already initialized
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return Result::FATAL_ERROR_INVALID_ARGS;
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}
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input = data;
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end = data + len;
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return Success;
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}
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const uint8_t* input;
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const uint8_t* end;
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Reader(const Reader&) = delete;
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void operator=(const Reader&) = delete;
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};
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inline bool
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InputContains(const Input& input, uint8_t toFind)
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{
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Reader reader(input);
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for (;;) {
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uint8_t b;
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if (reader.Read(b) != Success) {
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return false;
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}
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if (b == toFind) {
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return true;
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}
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}
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}
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} } // namespace mozilla::pkix
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#endif // mozilla_pkix_Input_h
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