transmission/libtransmission/crypto-utils.cc

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// This file Copyright © 2007-2023 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#include <algorithm>
#include <array>
#include <cctype>
#include <iterator>
#include <random>
#include <string>
#include <string_view>
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#include <vector>
extern "C"
{
#include <b64/cdecode.h>
#include <b64/cencode.h>
}
#include <fmt/core.h>
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#include "libtransmission/crypto-utils.h"
#include "libtransmission/tr-assert.h"
#include "libtransmission/utils.h"
using namespace std::literals;
// ---
namespace
{
constexpr auto TrSha1DigestStrlen = size_t{ 40 };
constexpr auto TrSha256DigestStrlen = size_t{ 64 };
namespace ssha1_impl
{
auto constexpr DigestStringSize = TrSha1DigestStrlen;
auto constexpr SaltedPrefix = "{"sv;
std::string tr_salt(std::string_view plaintext, std::string_view salt)
{
static_assert(DigestStringSize == 40);
// build a sha1 digest of the original content and the salt
auto const digest = tr_sha1::digest(plaintext, salt);
// convert it to a string. string holds three parts:
// DigestPrefix, stringified digest of plaintext + salt, and the salt.
return fmt::format(FMT_STRING("{:s}{:s}{:s}"), SaltedPrefix, tr_sha1_to_string(digest), salt);
}
} // namespace ssha1_impl
} // namespace
std::string tr_ssha1(std::string_view plaintext)
{
using namespace ssha1_impl;
// build an array of random Salter chars
auto constexpr Salter = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ./"sv;
static_assert(std::size(Salter) == 64);
auto constexpr SaltSize = size_t{ 8 };
auto salt = tr_rand_obj<std::array<char, SaltSize>>();
std::transform(
std::begin(salt),
std::end(salt),
std::begin(salt),
[&Salter](auto ch) { return Salter[ch % std::size(Salter)]; });
return tr_salt(plaintext, std::string_view{ std::data(salt), std::size(salt) });
}
bool tr_ssha1_test(std::string_view text)
{
using namespace ssha1_impl;
return tr_strv_starts_with(text, SaltedPrefix) && std::size(text) >= std::size(SaltedPrefix) + DigestStringSize;
}
bool tr_ssha1_matches(std::string_view ssha1, std::string_view plaintext)
{
using namespace ssha1_impl;
if (!tr_ssha1_test(ssha1))
{
return false;
}
auto const salt = ssha1.substr(std::size(SaltedPrefix) + DigestStringSize);
return tr_salt(plaintext, salt) == ssha1;
}
// ---
namespace
{
namespace base64_impl
{
constexpr size_t base64AllocSize(std::string_view input)
{
size_t ret_length = 4 * ((std::size(input) + 2) / 3); // NOLINT misc-const-correctness
#ifdef USE_SYSTEM_B64
// Additional space is needed for newlines if we're using unpatched libb64
ret_length += ret_length / 72 + 1;
#endif
return ret_length * 8;
}
} // namespace base64_impl
} // namespace
std::string tr_base64_encode(std::string_view input)
{
using namespace base64_impl;
auto buf = std::vector<char>(base64AllocSize(input));
auto state = base64_encodestate{};
base64_init_encodestate(&state);
size_t len = base64_encode_block(std::data(input), std::size(input), std::data(buf), &state);
len += base64_encode_blockend(std::data(buf) + len, &state);
auto str = std::string{};
std::copy_if(
std::data(buf),
std::data(buf) + len,
std::back_inserter(str),
[](auto ch) { return !tr_strv_contains("\r\n"sv, ch); });
return str;
}
std::string tr_base64_decode(std::string_view input)
{
auto buf = std::vector<char>(std::size(input) + 8);
auto state = base64_decodestate{};
base64_init_decodestate(&state);
size_t const len = base64_decode_block(std::data(input), std::size(input), std::data(buf), &state);
return std::string{ std::data(buf), len };
}
// ---
namespace
{
namespace hex_impl
{
template<typename InIt, typename OutIt>
constexpr void tr_binary_to_hex(InIt begin, InIt end, OutIt out)
{
auto constexpr Hex = "0123456789abcdef"sv;
while (begin != end)
{
auto const val = static_cast<unsigned int>(*begin++);
*out++ = Hex[val >> 4];
*out++ = Hex[val & 0xF];
}
}
constexpr void tr_hex_to_binary(char const* input, void* voutput, size_t byte_length)
{
auto constexpr Hex = "0123456789abcdef"sv;
auto* output = static_cast<uint8_t*>(voutput);
for (size_t i = 0; i < byte_length; ++i)
{
auto const upper_nibble = Hex.find(std::tolower(*input++));
auto const lower_nibble = Hex.find(std::tolower(*input++));
*output++ = (uint8_t)((upper_nibble << 4) | lower_nibble);
}
}
} // namespace hex_impl
} // namespace
tr_sha1_string tr_sha1_to_string(tr_sha1_digest_t const& digest)
{
using namespace hex_impl;
auto str = tr_sha1_string{};
tr_binary_to_hex(std::begin(digest), std::end(digest), std::back_inserter(str));
TR_ASSERT(std::size(str) == TrSha1DigestStrlen);
return str;
}
tr_sha256_string tr_sha256_to_string(tr_sha256_digest_t const& digest)
{
using namespace hex_impl;
auto str = tr_sha256_string{};
tr_binary_to_hex(std::begin(digest), std::end(digest), std::back_inserter(str));
TR_ASSERT(std::size(str) == TrSha256DigestStrlen);
return str;
}
std::optional<tr_sha1_digest_t> tr_sha1_from_string(std::string_view hex)
{
using namespace hex_impl;
if (std::size(hex) != TrSha1DigestStrlen)
{
return {};
}
if (!std::all_of(std::begin(hex), std::end(hex), [](unsigned char ch) { return isxdigit(ch); }))
{
return {};
}
auto digest = tr_sha1_digest_t{};
tr_hex_to_binary(std::data(hex), std::data(digest), std::size(digest));
return digest;
}
std::optional<tr_sha256_digest_t> tr_sha256_from_string(std::string_view hex)
{
using namespace hex_impl;
if (std::size(hex) != TrSha256DigestStrlen)
{
return {};
}
if (!std::all_of(std::begin(hex), std::end(hex), [](unsigned char ch) { return isxdigit(ch); }))
{
return {};
}
auto digest = tr_sha256_digest_t{};
tr_hex_to_binary(std::data(hex), std::data(digest), std::size(digest));
return digest;
}
// fallback implementation in case the system crypto library's RNG fails
void tr_rand_buffer_std(void* buffer, size_t length)
{
thread_local auto gen = std::mt19937{ std::random_device{}() };
thread_local auto dist = std::uniform_int_distribution<unsigned long long>{};
for (auto *walk = static_cast<uint8_t*>(buffer), *end = walk + length; walk < end;)
{
auto const tmp = dist(gen);
auto const step = std::min(sizeof(tmp), static_cast<size_t>(end - walk));
walk = std::copy_n(reinterpret_cast<uint8_t const*>(&tmp), step, walk);
}
}
void tr_rand_buffer(void* buffer, size_t length)
{
if (!tr_rand_buffer_crypto(buffer, length))
{
tr_rand_buffer_std(buffer, length);
}
}