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/*
* Copyright (c) 2020, Ali Mohammad Pur <mpfard@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/BitmapView.h>
#include <AK/Result.h>
#include <AK/Types.h>
#include <LibCrypto/ASN1/ASN1.h>
#include <LibCrypto/BigInt/UnsignedBigInteger.h>
namespace Crypto::ASN1 {
class BitStringView {
public:
BitStringView(ReadonlyBytes data, size_t unused_bits)
: m_data(data)
, m_unused_bits(unused_bits)
{
}
ReadonlyBytes raw_bytes() const
{
VERIFY(m_unused_bits == 0);
return m_data;
}
bool get(size_t index)
{
if (index >= 8 * m_data.size() - m_unused_bits)
return false;
return 0 != (m_data[index / 8] & (1u << (7 - (index % 8))));
}
private:
ReadonlyBytes m_data;
size_t m_unused_bits;
};
class Decoder {
public:
Decoder(ReadonlyBytes data)
{
m_stack.append(data);
}
// Read a tag without consuming it (and its data).
ErrorOr<Tag> peek();
bool eof() const;
template<typename ValueType>
struct TaggedValue {
Tag tag;
ValueType value;
};
ErrorOr<void> drop()
{
if (m_stack.is_empty())
return Error::from_string_literal("ASN1::Decoder: Trying to drop using an empty stack");
if (eof())
return Error::from_string_literal("ASN1::Decoder: Trying to drop using a decoder that is EOF");
auto previous_position = m_stack;
auto tag_or_error = peek();
if (tag_or_error.is_error()) {
m_stack = move(previous_position);
return tag_or_error.release_error();
}
auto length_or_error = read_length();
if (length_or_error.is_error()) {
m_stack = move(previous_position);
return length_or_error.release_error();
}
auto length = length_or_error.value();
auto bytes_result = read_bytes(length);
if (bytes_result.is_error()) {
m_stack = move(previous_position);
return bytes_result.release_error();
}
m_current_tag.clear();
return {};
}
template<typename ValueType>
ErrorOr<ValueType> read(Optional<Class> class_override = {}, Optional<Kind> kind_override = {})
{
if (m_stack.is_empty())
return Error::from_string_literal("ASN1::Decoder: Trying to read using an empty stack");
if (eof())
return Error::from_string_literal("ASN1::Decoder: Trying to read using a decoder that is EOF");
auto previous_position = m_stack;
auto tag_or_error = peek();
if (tag_or_error.is_error()) {
m_stack = move(previous_position);
return tag_or_error.release_error();
}
auto length_or_error = read_length();
if (length_or_error.is_error()) {
m_stack = move(previous_position);
return length_or_error.release_error();
}
auto tag = tag_or_error.value();
auto length = length_or_error.value();
auto value_or_error = read_value<ValueType>(class_override.value_or(tag.class_), kind_override.value_or(tag.kind), length);
if (value_or_error.is_error()) {
m_stack = move(previous_position);
return value_or_error.release_error();
}
m_current_tag.clear();
return value_or_error.release_value();
}
ErrorOr<void> enter();
ErrorOr<void> leave();
private:
template<typename ValueType, typename DecodedType>
ErrorOr<ValueType> with_type_check(DecodedType&& value)
{
if constexpr (requires { ValueType { value }; })
return ValueType { value };
return Error::from_string_literal("ASN1::Decoder: Trying to decode a value from an incompatible type");
}
template<typename ValueType, typename DecodedType>
ErrorOr<ValueType> with_type_check(ErrorOr<DecodedType>&& value_or_error)
{
if (value_or_error.is_error())
return value_or_error.release_error();
if constexpr (IsSame<ValueType, bool> && !IsSame<DecodedType, bool>) {
return Error::from_string_literal("ASN1::Decoder: Trying to decode a boolean from a non-boolean type");
} else {
auto&& value = value_or_error.value();
if constexpr (requires { ValueType { value }; })
return ValueType { value };
}
return Error::from_string_literal("ASN1::Decoder: Trying to decode a value from an incompatible type");
}
template<typename ValueType>
ErrorOr<ValueType> read_value(Class klass, Kind kind, size_t length)
{
auto data = TRY(read_bytes(length));
if (klass != Class::Universal)
return with_type_check<ValueType>(data);
if (kind == Kind::Boolean)
return with_type_check<ValueType>(decode_boolean(data));
if (kind == Kind::Integer)
return with_type_check<ValueType>(decode_arbitrary_sized_integer(data));
if (kind == Kind::OctetString)
return with_type_check<ValueType>(decode_octet_string(data));
if (kind == Kind::Null)
return with_type_check<ValueType>(decode_null(data));
if (kind == Kind::ObjectIdentifier)
return with_type_check<ValueType>(decode_object_identifier(data));
if (kind == Kind::PrintableString || kind == Kind::IA5String || kind == Kind::UTCTime)
return with_type_check<ValueType>(decode_printable_string(data));
if (kind == Kind::Utf8String)
return with_type_check<ValueType>(StringView { data.data(), data.size() });
if (kind == Kind::BitString)
return with_type_check<ValueType>(decode_bit_string(data));
return with_type_check<ValueType>(data);
}
ErrorOr<Tag> read_tag();
ErrorOr<size_t> read_length();
ErrorOr<u8> read_byte();
ErrorOr<ReadonlyBytes> read_bytes(size_t length);
static ErrorOr<bool> decode_boolean(ReadonlyBytes);
static ErrorOr<UnsignedBigInteger> decode_arbitrary_sized_integer(ReadonlyBytes);
static ErrorOr<StringView> decode_octet_string(ReadonlyBytes);
static ErrorOr<nullptr_t> decode_null(ReadonlyBytes);
static ErrorOr<Vector<int>> decode_object_identifier(ReadonlyBytes);
static ErrorOr<StringView> decode_printable_string(ReadonlyBytes);
static ErrorOr<BitStringView> decode_bit_string(ReadonlyBytes);
Vector<ReadonlyBytes> m_stack;
Optional<Tag> m_current_tag;
};
ErrorOr<void> pretty_print(Decoder&, Stream&, int indent = 0);
}
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