mirror of https://github.com/OpenTTD/OpenTTD.git
Change: use a stronger hash and actual random information to generate Uids
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@ -448,6 +448,7 @@ if(WIN32)
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usp10
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psapi
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winhttp
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bcrypt
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)
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endif()
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@ -10,6 +10,7 @@
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#include "../stdafx.h"
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#include "random_func.hpp"
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#include "bitmath_func.hpp"
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#include "../debug.h"
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#ifdef RANDOM_DEBUG
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#include "../network/network.h"
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@ -20,6 +21,15 @@
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#include "../timer/timer_game_calendar.h"
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#endif /* RANDOM_DEBUG */
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#if defined(_WIN32)
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# include <windows.h>
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# include <bcrypt.h>
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#elif defined(__EMSCRIPTEN__)
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# include <emscripten.h>
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#elif !defined(__APPLE__) && !defined(__NetBSD__) && !defined(__FreeBSD__)
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# include <sys/random.h>
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#endif
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#include "../safeguards.h"
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Randomizer _random, _interactive_random;
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@ -83,3 +93,53 @@ uint32_t DoRandomRange(uint32_t limit, int line, const char *file)
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return ((uint64_t)DoRandom(line, file) * (uint64_t)limit) >> 32;
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}
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#endif /* RANDOM_DEBUG */
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/**
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* Fill the given buffer with random bytes.
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*
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* This function will attempt to use a cryptographically-strong random
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* generator, but will fall back to a weaker random generator if none is
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* available.
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*
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* In the end, the buffer will always be filled with some form of random
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* bytes when this function returns.
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*
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* @param buf The buffer to fill with random bytes.
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*/
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void RandomBytesWithFallback(std::span<uint8_t> buf)
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{
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#if defined(_WIN32)
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auto res = BCryptGenRandom(nullptr, static_cast<PUCHAR>(buf.data()), static_cast<ULONG>(buf.size()), BCRYPT_USE_SYSTEM_PREFERRED_RNG);
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if (res >= 0) return;
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#elif defined(__APPLE__) || defined(__NetBSD__) || defined(__FreeBSD__)
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arc4random_buf(buf.data(), buf.size());
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return;
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#elif defined(__GLIBC__) && ((__GLIBC__ > 2) || ((__GLIBC__ == 2) && (__GLIBC_MINOR__ >= 25)))
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auto res = getrandom(buf.data(), buf.size(), 0);
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if (res > 0 && static_cast<size_t>(res) == buf.size()) return;
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#elif defined(__EMSCRIPTEN__)
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auto res = EM_ASM_INT({
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var buf = $0;
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var bytes = $1;
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var crypto = window.crypto;
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if (crypto === undefined || crypto.getRandomValues === undefined) {
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return -1;
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}
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crypto.getRandomValues(Module.HEAPU8.subarray(buf, buf + bytes));
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return 1;
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}, buf.data(), buf.size());
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if (res > 0) return;
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#else
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# warning "No cryptographically-strong random generator available; using a fallback instead"
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#endif
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static bool warned_once = false;
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Debug(misc, warned_once ? 1 : 0, "Cryptographically-strong random generator unavailable; using fallback");
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warned_once = true;
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for (uint i = 0; i < buf.size(); i++) {
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buf[i] = static_cast<uint8_t>(InteractiveRandom());
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}
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}
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@ -159,4 +159,6 @@ inline bool Chance16R(const uint a, const uint b, uint32_t &r)
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}
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#endif /* RANDOM_DEBUG */
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void RandomBytesWithFallback(std::span<uint8_t> buf);
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#endif /* RANDOM_FUNC_HPP */
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31
src/misc.cpp
31
src/misc.cpp
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@ -31,7 +31,7 @@
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#include "town_kdtree.h"
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#include "viewport_kdtree.h"
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#include "newgrf_profiling.h"
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#include "3rdparty/md5/md5.h"
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#include "3rdparty/monocypher/monocypher.h"
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#include "safeguards.h"
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@ -61,25 +61,24 @@ void InitializeOldNames();
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/**
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* Generate an unique ID.
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*
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* It isn't as much of an unique ID as we would like, but our random generator
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* can only produce 32bit random numbers.
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* That is why we combine InteractiveRandom with the current (steady) clock.
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* The first to add a bit of randomness, the second to ensure you can't get
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* the same unique ID when you run it twice from the same state at different
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* times.
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*
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* This makes it unlikely that two users generate the same ID for different
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* subjects. But as this is not an UUID, so it can't be ruled out either.
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* It isn't as much of an unique ID but more a hashed digest of a random
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* string and a time. It is very likely to be unique, but it does not follow
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* any UUID standard.
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*/
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std::string GenerateUid(std::string_view subject)
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{
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auto current_time = std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::steady_clock::now().time_since_epoch()).count();
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std::string coding_string = fmt::format("{}{}{}", InteractiveRandom(), current_time, subject);
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std::array<uint8_t, 32> random_bytes;
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RandomBytesWithFallback(random_bytes);
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Md5 checksum;
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MD5Hash digest;
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checksum.Append(coding_string.c_str(), coding_string.length());
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checksum.Finish(digest);
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auto current_time = std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::steady_clock::now().time_since_epoch()).count();
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std::string coding_string = fmt::format("{}{}", current_time, subject);
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std::array<uint8_t, 16> digest;
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crypto_blake2b_ctx ctx;
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crypto_blake2b_init(&ctx, digest.size());
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crypto_blake2b_update(&ctx, random_bytes.data(), random_bytes.size());
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crypto_blake2b_update(&ctx, reinterpret_cast<const uint8_t *>(coding_string.data()), coding_string.size());
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crypto_blake2b_final(&ctx, digest.data());
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return FormatArrayAsHex(digest);
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}
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