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shorten comments for pr #390

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Daan 2021-12-15 17:06:09 -08:00
parent 48996ff449
commit 0e851de2ba
1 changed files with 13 additions and 25 deletions
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38
src/random.c
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@ -160,7 +160,7 @@ uintptr_t _mi_random_next(mi_random_ctx_t* ctx) {
/* ---------------------------------------------------------------------------- /* ----------------------------------------------------------------------------
To initialize a fresh random context we rely on the OS: To initialize a fresh random context we rely on the OS:
- Windows : BCryptGenRandom (or RtlGenRandom) - Windows : BCryptGenRandom (or RtlGenRandom)
- macOS : CCRandomGenerateBytes - macOS : CCRandomGenerateBytes, arc4random_buf
- bsd,wasi : arc4random_buf - bsd,wasi : arc4random_buf
- Linux : getrandom,/dev/urandom - Linux : getrandom,/dev/urandom
If we cannot get good randomness, we fall back to weak randomness based on a timer and ASLR. If we cannot get good randomness, we fall back to weak randomness based on a timer and ASLR.
@ -194,34 +194,22 @@ static bool os_random_buf(void* buf, size_t buf_len) {
#elif defined(__APPLE__) #elif defined(__APPLE__)
#include <AvailabilityMacros.h> #include <AvailabilityMacros.h>
#if defined(MAC_OS_X_VERSION_10_10) && \ #if defined(MAC_OS_X_VERSION_10_10) && MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_10
MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_10
#include <CommonCrypto/CommonRandom.h> #include <CommonCrypto/CommonRandom.h>
#endif #endif
static bool os_random_buf(void* buf, size_t buf_len) { static bool os_random_buf(void* buf, size_t buf_len) {
/* The implementation of arc4random_buf(3) differs from its documentation. #if defined(MAC_OS_X_VERSION_10_15) && MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_15
* It is documented as "always successful, and no return value is reserved // We prefere CCRandomGenerateBytes as it returns an error code while arc4random_buf
* to indicate an error." However, the actual implementation invokes the // may fail silently on macOS. See PR #390, and <https://opensource.apple.com/source/Libc/Libc-1439.40.11/gen/FreeBSD/arc4random.c.auto.html>
* function "ccrng_generate" without validating the error cases. It might return (CCRandomGenerateBytes(buf, buf_len) == kCCSuccess);
* fail silently, which leads to unexpected source of entropy. #else
* See: // fall back on older macOS
* https://opensource.apple.com/source/Libc/Libc-1439.40.11/gen/FreeBSD/arc4random.c.auto.html arc4random_buf(buf, buf_len);
* return true;
* CCRandomGenerateBytes(), on the contrary, returns cryptographically strong #endif
* random bits with explicit status code.
*/
#if defined(MAC_OS_X_VERSION_10_15) && \
MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_15
return CCRandomGenerateBytes(buf, buf_len) == kCCSuccess;
#else
/* Prior to macOS 10.15, CCRandomGenerateBytes() might take a bit longer time
* to complete, so failback to arc4random_buf().
*/
arc4random_buf(buf, buf_len);
return true;
#endif
} }
#elif defined(ANDROID) || defined(__DragonFly__) || \
#elif defined(__ANDROID__) || defined(__DragonFly__) || \
defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || \ defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || \
defined(__sun) // todo: what to use with __wasi__? defined(__sun) // todo: what to use with __wasi__?
#include <stdlib.h> #include <stdlib.h>