Source code
Revision control
Copy as Markdown
Other Tools
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This code is made available to you under your choice of the following sets
* of licensing terms:
*/
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
*/
/* Copyright 2013 Mozilla Contributors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef mozilla_pkix_Input_h
#define mozilla_pkix_Input_h
#include <algorithm>
#include "mozpkix/Result.h"
#include "stdint.h"
namespace mozilla {
namespace pkix {
class Reader;
// An Input is a safety-oriented immutable weak reference to a array of bytes
// of a known size. The data can only be legally accessed by constructing a
// Reader object, which guarantees all accesses to the data are memory safe.
// Neither Input not Reader provide any facilities for modifying the data
// they reference.
//
// Inputs are small and should usually be passed by value, not by reference,
// though for inline functions the distinction doesn't matter:
//
// Result GoodExample(Input input);
// Result BadExample(const Input& input);
// Result WorseExample(const uint8_t* input, size_t len);
//
// Note that in the example, GoodExample has the same performance
// characteristics as WorseExample, but with much better safety guarantees.
class Input final {
public:
typedef uint16_t size_type;
// This constructor is useful for inputs that are statically known to be of a
// fixed size, e.g.:
//
// static const uint8_t EXPECTED_BYTES[] = { 0x00, 0x01, 0x02 };
// const Input expected(EXPECTED_BYTES);
//
// This is equivalent to (and preferred over):
//
// static const uint8_t EXPECTED_BYTES[] = { 0x00, 0x01, 0x02 };
// Input expected;
// Result rv = expected.Init(EXPECTED_BYTES, sizeof EXPECTED_BYTES);
template <size_type N>
explicit Input(const uint8_t (&aData)[N]) : data(aData), len(N) {}
// Construct a valid, empty, Init-able Input.
Input() : data(nullptr), len(0u) {}
// This is intentionally not explicit in order to allow value semantics.
Input(const Input&) = default;
// Initialize the input. data must be non-null and len must be less than
// 65536. Init may not be called more than once.
Result Init(const uint8_t* aData, size_t aLen) {
if (this->data) {
// already initialized
return Result::FATAL_ERROR_INVALID_ARGS;
}
if (!aData || aLen > 0xffffu) {
// input too large
return Result::ERROR_BAD_DER;
}
this->data = aData;
this->len = aLen;
return Success;
}
// Initialize the input to be equivalent to the given input. Init may not be
// called more than once.
//
// This is basically operator=, but it wasn't given that name because
// normally callers do not check the result of operator=, and normally
// operator= can be used multiple times.
Result Init(Input other) { return Init(other.data, other.len); }
// Returns the length of the input.
//
// Having the return type be size_type instead of size_t avoids the need for
// callers to ensure that the result is small enough.
size_type GetLength() const { return static_cast<size_type>(len); }
// Don't use this. It is here because we have some "friend" functions that we
// don't want to declare in this header file.
const uint8_t* UnsafeGetData() const { return data; }
private:
const uint8_t* data;
size_t len;
void operator=(const Input&) = delete; // Use Init instead.
};
inline bool InputsAreEqual(const Input& a, const Input& b) {
return a.GetLength() == b.GetLength() &&
std::equal(a.UnsafeGetData(), a.UnsafeGetData() + a.GetLength(),
b.UnsafeGetData());
}
// An Reader is a cursor/iterator through the contents of an Input, designed to
// maximize safety during parsing while minimizing the performance cost of that
// safety. In particular, all methods do strict bounds checking to ensure
// buffer overflows are impossible, and they are all inline so that the
// compiler can coalesce as many of those checks together as possible.
//
// In general, Reader allows for one byte of lookahead and no backtracking.
// However, the Match* functions internally may have more lookahead.
class Reader final {
public:
Reader() : input(nullptr), end(nullptr) {}
explicit Reader(Input aInput)
: input(aInput.UnsafeGetData()),
end(aInput.UnsafeGetData() + aInput.GetLength()) {}
Result Init(Input aInput) {
if (this->input) {
return Result::FATAL_ERROR_INVALID_ARGS;
}
this->input = aInput.UnsafeGetData();
this->end = aInput.UnsafeGetData() + aInput.GetLength();
return Success;
}
bool Peek(uint8_t expectedByte) const {
return input < end && *input == expectedByte;
}
Result Read(uint8_t& out) {
Result rv = EnsureLength(1);
if (rv != Success) {
return rv;
}
out = *input++;
return Success;
}
Result Read(uint16_t& out) {
Result rv = EnsureLength(2);
if (rv != Success) {
return rv;
}
out = *input++;
out <<= 8u;
out |= *input++;
return Success;
}
template <Input::size_type N>
bool MatchRest(const uint8_t (&toMatch)[N]) {
// Normally we use EnsureLength which compares (input + len < end), but
// here we want to be sure that there is nothing following the matched
// bytes
if (static_cast<size_t>(end - input) != N) {
return false;
}
if (!std::equal(input, end, toMatch)) {
return false;
}
input = end;
return true;
}
bool MatchRest(Input toMatch) {
// Normally we use EnsureLength which compares (input + len < end), but
// here we want to be sure that there is nothing following the matched
// bytes
size_t remaining = static_cast<size_t>(end - input);
if (toMatch.GetLength() != remaining) {
return false;
}
if (!std::equal(input, end, toMatch.UnsafeGetData())) {
return false;
}
input = end;
return true;
}
Result Skip(Input::size_type len) {
Result rv = EnsureLength(len);
if (rv != Success) {
return rv;
}
input += len;
return Success;
}
Result Skip(Input::size_type len, Reader& skipped) {
Result rv = EnsureLength(len);
if (rv != Success) {
return rv;
}
rv = skipped.Init(input, len);
if (rv != Success) {
return rv;
}
input += len;
return Success;
}
Result Skip(Input::size_type len, /*out*/ Input& skipped) {
Result rv = EnsureLength(len);
if (rv != Success) {
return rv;
}
rv = skipped.Init(input, len);
if (rv != Success) {
return rv;
}
input += len;
return Success;
}
void SkipToEnd() { input = end; }
Result SkipToEnd(/*out*/ Input& skipped) {
return Skip(static_cast<Input::size_type>(end - input), skipped);
}
Result EnsureLength(Input::size_type len) {
if (static_cast<size_t>(end - input) < len) {
return Result::ERROR_BAD_DER;
}
return Success;
}
bool AtEnd() const { return input == end; }
class Mark final {
public:
Mark(const Mark&) = default; // Intentionally not explicit.
private:
friend class Reader;
Mark(const Reader& aInput, const uint8_t* aMark)
: input(aInput), mark(aMark) {}
const Reader& input;
const uint8_t* const mark;
void operator=(const Mark&) = delete;
};
Mark GetMark() const { return Mark(*this, input); }
Result GetInput(const Mark& mark, /*out*/ Input& item) {
if (&mark.input != this || mark.mark > input) {
return NotReached("invalid mark", Result::FATAL_ERROR_INVALID_ARGS);
}
return item.Init(mark.mark,
static_cast<Input::size_type>(input - mark.mark));
}
private:
Result Init(const uint8_t* data, Input::size_type len) {
if (input) {
// already initialized
return Result::FATAL_ERROR_INVALID_ARGS;
}
input = data;
end = data + len;
return Success;
}
const uint8_t* input;
const uint8_t* end;
Reader(const Reader&) = delete;
void operator=(const Reader&) = delete;
};
inline bool InputContains(const Input& input, uint8_t toFind) {
Reader reader(input);
for (;;) {
uint8_t b;
if (reader.Read(b) != Success) {
return false;
}
if (b == toFind) {
return true;
}
}
}
} // namespace pkix
} // namespace mozilla
#endif // mozilla_pkix_Input_h