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LibCrypto: Add a minimal DER encoder

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Progress towards #23562.
This commit is contained in:
Ali Mohammad Pur 2024-03-13 01:48:01 +01:00 • committed by Andrew Kaster
parent 6574e60805
commit d451f84f31
4 changed files with 406 additions and 32 deletions
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207
Userland/Libraries/LibCrypto/ASN1/DER.cpp
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@ -4,6 +4,7 @@
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/IntegralMath.h>
#include <AK/Stream.h>
#include <AK/Try.h>
#include <AK/Utf8View.h>
@ -234,6 +235,206 @@ ErrorOr<void> Decoder::leave()
return {};
}
ErrorOr<void> Encoder::write_tag(Class class_, Type type, Kind kind)
{
auto class_byte = to_underlying(class_);
auto type_byte = to_underlying(type);
auto kind_byte = to_underlying(kind);
auto byte = class_byte | type_byte | kind_byte;
if (kind_byte > 0x1f) {
auto high = kind_byte >> 7;
byte = class_byte | type_byte | 0x1f;
TRY(write_byte(byte));
byte = (kind_byte & 0x7f) | high;
}
return write_byte(byte);
}
ErrorOr<void> Encoder::write_byte(u8 byte)
{
return write_bytes({ &byte, 1 });
}
ErrorOr<void> Encoder::write_length(size_t value)
{
if (value < 0x80)
return write_byte(value);
size_t size = ceil_div(AK::ceil_log2(value), 3ul);
TRY(write_byte(0x80 | size));
for (size_t i = 0; i < size; i++) {
auto shift = (size - i - 1) * 8;
auto byte = (value >> shift) & 0xff;
TRY(write_byte(byte));
}
return {};
}
ErrorOr<void> Encoder::write_bytes(ReadonlyBytes bytes)
{
auto output = TRY(m_buffer_stack.last().get_bytes_for_writing(bytes.size()));
bytes.copy_to(output);
return {};
}
ErrorOr<void> Encoder::write_boolean(bool value, Optional<Class> class_override, Optional<Kind> kind_override)
{
auto class_ = class_override.value_or(Class::Universal);
auto type = Type::Primitive;
auto kind = kind_override.value_or(Kind::Boolean);
TRY(write_tag(class_, type, kind));
TRY(write_length(1));
return write_byte(value ? 0xff : 0x00);
}
ErrorOr<void> Encoder::write_arbitrary_sized_integer(UnsignedBigInteger const& value, Optional<Class> class_override, Optional<Kind> kind_override)
{
auto class_ = class_override.value_or(Class::Universal);
auto type = Type::Primitive;
auto kind = kind_override.value_or(Kind::Integer);
TRY(write_tag(class_, type, kind));
auto max_byte_size = max(1ull, value.length() * UnsignedBigInteger::BITS_IN_WORD / 8); // At minimum, we need one byte to encode 0.
ByteBuffer buffer;
auto output = TRY(buffer.get_bytes_for_writing(max_byte_size));
auto size = value.export_data(output);
// DER does not allow empty integers, encode a zero if the exported size is zero.
if (size == 0) {
output[0] = 0;
size = 1;
}
// Chop off the leading zeros
if constexpr (AK::HostIsLittleEndian) {
while (size > 1 && output[0] == 0) {
size--;
output = output.slice(1);
}
} else {
while (size > 1 && output[size - 1] == 0)
size--;
}
// If the MSB is set, we need to add a leading zero to indicate a positive number.
if ((output[0] & 0x80) != 0) {
TRY(write_length(size + 1));
TRY(write_byte(0));
} else {
TRY(write_length(size));
}
return write_bytes(output.slice(0, size));
}
ErrorOr<void> Encoder::write_printable_string(StringView string, Optional<Class> class_override, Optional<Kind> kind_override)
{
Utf8View view { string };
if (!view.validate())
return Error::from_string_literal("ASN1::Encoder: Invalid UTF-8 in printable string");
auto class_ = class_override.value_or(Class::Universal);
auto type = Type::Primitive;
auto kind = kind_override.value_or(Kind::PrintableString);
TRY(write_tag(class_, type, kind));
TRY(write_length(string.length()));
return write_bytes(string.bytes());
}
ErrorOr<void> Encoder::write_octet_string(ReadonlyBytes bytes, Optional<Class> class_override, Optional<Kind> kind_override)
{
auto class_ = class_override.value_or(Class::Universal);
auto type = Type::Primitive;
auto kind = kind_override.value_or(Kind::OctetString);
TRY(write_tag(class_, type, kind));
TRY(write_length(bytes.size()));
return write_bytes(bytes);
}
ErrorOr<void> Encoder::write_null(Optional<Class> class_override, Optional<Kind> kind_override)
{
auto class_ = class_override.value_or(Class::Universal);
auto type = Type::Primitive;
auto kind = kind_override.value_or(Kind::Null);
TRY(write_tag(class_, type, kind));
TRY(write_length(0));
return {};
}
ErrorOr<void> Encoder::write_object_identifier(Span<int const> segments, Optional<Class> class_override, Optional<Kind> kind_override)
{
auto class_ = class_override.value_or(Class::Universal);
auto type = Type::Primitive;
auto kind = kind_override.value_or(Kind::ObjectIdentifier);
if (segments.size() < 2)
return Error::from_string_literal("ASN1::Encoder: Object identifier must have at least two segments");
TRY(write_tag(class_, type, kind));
size_t length = 1;
for (size_t i = 2; i < segments.size(); i++) {
auto segment = segments[i];
if (segment < 0)
return Error::from_string_literal("ASN1::Encoder: Object identifier segments must be non-negative");
if (segment < 0x80)
length += 1;
else if (segment < 0x4000)
length += 2;
else if (segment < 0x200000)
length += 3;
else
length += 4;
}
TRY(write_length(length));
auto first_byte = (segments[0] * 40) + segments[1];
TRY(write_byte(first_byte));
for (size_t i = 2; i < segments.size(); i++) {
auto segment = segments[i];
if (segment < 0x80) {
TRY(write_byte(segment));
} else if (segment < 0x4000) {
TRY(write_byte((segment >> 7) | 0x80));
TRY(write_byte(segment & 0x7f));
} else if (segment < 0x200000) {
TRY(write_byte((segment >> 14) | 0x80));
TRY(write_byte(((segment >> 7) & 0x7f) | 0x80));
TRY(write_byte(segment & 0x7f));
} else {
TRY(write_byte((segment >> 21) | 0x80));
TRY(write_byte(((segment >> 14) & 0x7f) | 0x80));
TRY(write_byte(((segment >> 7) & 0x7f) | 0x80));
TRY(write_byte(segment & 0x7f));
}
}
return {};
}
ErrorOr<void> Encoder::write_bit_string(BitStringView view, Optional<Class> class_override, Optional<Kind> kind_override)
{
auto class_ = class_override.value_or(Class::Universal);
auto type = Type::Primitive;
auto kind = kind_override.value_or(Kind::BitString);
auto unused_bits = view.unused_bits();
auto total_size_in_bits = view.byte_length() * 8 - unused_bits;
TRY(write_tag(class_, type, kind));
TRY(write_length(ceil_div(total_size_in_bits, 8ul) + 1));
TRY(write_byte(unused_bits));
return write_bytes(view.underlying_bytes());
}
ErrorOr<void> pretty_print(Decoder& decoder, Stream& stream, int indent)
{
while (!decoder.eof()) {
@ -244,7 +445,7 @@ ErrorOr<void> pretty_print(Decoder& decoder, Stream& stream, int indent)
builder.append(' ');
builder.appendff("<{}> ", class_name(tag.class_));
if (tag.type == Type::Constructed) {
builder.appendff("[{}] {} ({})", type_name(tag.type), static_cast<u8>(tag.kind), kind_name(tag.kind));
builder.appendff("[{}] {} ({})", type_name(tag.type), to_underlying(tag.kind), kind_name(tag.kind));
TRY(decoder.enter());
builder.append('\n');
@ -257,7 +458,7 @@ ErrorOr<void> pretty_print(Decoder& decoder, Stream& stream, int indent)
continue;
} else {
if (tag.class_ != Class::Universal)
builder.appendff("[{}] {} {}", type_name(tag.type), static_cast<u8>(tag.kind), kind_name(tag.kind));
builder.appendff("[{}] {} {}", type_name(tag.type), to_underlying(tag.kind), kind_name(tag.kind));
else
builder.appendff("[{}] {}", type_name(tag.type), kind_name(tag.kind));
switch (tag.kind) {
@ -323,7 +524,7 @@ ErrorOr<void> pretty_print(Decoder& decoder, Stream& stream, int indent)
case Kind::Set:
return Error::from_string_literal("ASN1::Decoder: Unexpected Primitive");
default: {
dbgln("PrettyPrint error: Unhandled kind {}", static_cast<u8>(tag.kind));
dbgln("PrettyPrint error: Unhandled kind {}", to_underlying(tag.kind));
}
}
}