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c2b6c8aa16
__swift_size_t on Windows is a size_t, which makes it potentially a 64-bit integer. ULONG, however, is always a 32-bit integer, and so this cast risks shrinking the apparent size of the cbBuffer argument to BCryptGenRandom. The effect of that will be to underfill the buffer, leaving it full of uninitialized memory that we would treat as random. The actual risk from this in the current implementation is basically zero, as user code can only ever invoke this with an argument size of 8. There's no good reason to leave this sharp edge on the API though.
122 lines
3.6 KiB
C++
122 lines
3.6 KiB
C++
//===--- Random.cpp -------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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// swift_stdlib_random
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//
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// Should the implementation of this function add a new platform/change for a
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// platform, make sure to also update the documentation regarding platform
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// implementation of this function.
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// This can be found at: /docs/Random.md
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#if defined(_WIN32) && !defined(__CYGWIN__)
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#define WIN32_LEAN_AND_MEAN
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#include <Windows.h>
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#include <Bcrypt.h>
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#pragma comment(lib, "bcrypt.lib")
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#else
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#include <errno.h>
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#include <fcntl.h>
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#include <unistd.h>
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#endif
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#if __has_include(<sys/random.h>)
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#include <sys/random.h>
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#endif
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#include <sys/stat.h>
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#if __has_include(<sys/syscall.h>)
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#include <sys/syscall.h>
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#endif
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#include <stdlib.h>
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#include "swift/Runtime/Debug.h"
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#include "swift/Runtime/Mutex.h"
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#include "../SwiftShims/Random.h"
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#if defined(__APPLE__)
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SWIFT_RUNTIME_STDLIB_API
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void swift::swift_stdlib_random(void *buf, __swift_size_t nbytes) {
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arc4random_buf(buf, nbytes);
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}
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#elif defined(_WIN32) && !defined(__CYGWIN__)
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#warning TODO: Test swift_stdlib_random on Windows
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SWIFT_RUNTIME_STDLIB_API
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void swift::swift_stdlib_random(void *buf, __swift_size_t nbytes) {
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if (nbytes > ULONG_MAX) {
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fatalError(0, "Fatal error: %zd exceeds ULONG_MAX\n", nbytes);
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}
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NTSTATUS status = BCryptGenRandom(nullptr,
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static_cast<PUCHAR>(buf),
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static_cast<ULONG>(nbytes),
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BCRYPT_USE_SYSTEM_PREFERRED_RNG);
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if (!BCRYPT_SUCCESS(status)) {
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fatalError(0, "Fatal error: 0x%.8X in '%s'\n", status, __func__);
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}
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}
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#else
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#undef WHILE_EINTR
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#define WHILE_EINTR(expression) ({ \
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decltype(expression) result = -1; \
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do { result = (expression); } while (result == -1 && errno == EINTR); \
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result; \
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})
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SWIFT_RUNTIME_STDLIB_API
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void swift::swift_stdlib_random(void *buf, __swift_size_t nbytes) {
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while (nbytes > 0) {
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__swift_ssize_t actual_nbytes = -1;
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#if defined(__NR_getrandom)
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static const bool getrandom_available =
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!(syscall(__NR_getrandom, nullptr, 0, 0) == -1 && errno == ENOSYS);
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if (getrandom_available) {
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actual_nbytes = WHILE_EINTR(syscall(__NR_getrandom, buf, nbytes, 0));
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}
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#elif __has_include(<sys/random.h>) && (defined(__CYGWIN__) || defined(__Fuchsia__))
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__swift_size_t getentropy_nbytes = std::min(nbytes, __swift_size_t{256});
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if (0 == getentropy(buf, getentropy_nbytes)) {
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actual_nbytes = getentropy_nbytes;
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}
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#endif
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if (actual_nbytes == -1) {
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static const int fd =
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WHILE_EINTR(open("/dev/urandom", O_RDONLY | O_CLOEXEC, 0));
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if (fd != -1) {
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static StaticMutex mutex;
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mutex.withLock([&] {
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actual_nbytes = WHILE_EINTR(read(fd, buf, nbytes));
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});
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}
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}
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if (actual_nbytes == -1) {
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fatalError(0, "Fatal error: %d in '%s'\n", errno, __func__);
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}
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buf = static_cast<uint8_t *>(buf) + actual_nbytes;
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nbytes -= actual_nbytes;
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}
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}
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#endif
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