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Win32: check for bcrypt.lib #6

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Win32: check for bcrypt.lib #6

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3797c6e
Win32: check for BCryptGenRandom
Coeur Nov 4, 2025
8c6f204
Condition is bcrypt.lib
Coeur Nov 9, 2025
97a86bf
Revert "Condition is bcrypt.lib"
Coeur Nov 19, 2025
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1 change: 1 addition & 0 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -533,6 +533,7 @@ if (WIN32)
list(APPEND SYMBOLS_TO_CHECK
_gmtime64
_gmtime64_s
BCryptGenRandom
)
else()
list(APPEND SYMBOLS_TO_CHECK
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20 changes: 20 additions & 0 deletions arc4random.c
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Expand Up @@ -52,7 +52,11 @@
#ifndef ARC4RANDOM_NO_INCLUDES
#include "evconfig-private.h"
#ifdef _WIN32
#ifndef EVENT__HAVE_BCRYPTGENRANDOM
#include <wincrypt.h>
#else
#include <bcrypt.h>
#endif
#include <process.h>
#include <winerror.h>
#else
Expand Down Expand Up @@ -153,9 +157,25 @@ static int
arc4_seed_win32(void)
{
unsigned char buf[ADD_ENTROPY];
#ifndef EVENT__HAVE_BCRYPTGENRANDOM
/* This is adapted from Tor's crypto_seed_rng() */
static int provider_set = 0;
static HCRYPTPROV provider;

if (!provider_set) {
if (!CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
CRYPT_VERIFYCONTEXT)) {
if (GetLastError() != (DWORD)NTE_BAD_KEYSET)
return -1;
}
provider_set = 1;
}
if (!CryptGenRandom(provider, sizeof(buf), buf))
#else

if (BCryptGenRandom(NULL, buf, sizeof(buf),
BCRYPT_USE_SYSTEM_PREFERRED_RNG))
#endif
return -1;
arc4_addrandom(buf, sizeof(buf));
evutil_memclear_(buf, sizeof(buf));
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3 changes: 3 additions & 0 deletions event-config.h.cmake
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Expand Up @@ -285,6 +285,9 @@
/* Define to 1 if you have the `_gmtime64' function. */
#cmakedefine EVENT__HAVE__GMTIME64 1

/* Define to 1 if you have the `BCryptGenRandom' function. */
#cmakedefine EVENT__HAVE_BCRYPTGENRANDOM 1

/* Define to 1 if the system has the type `struct addrinfo'. */
#cmakedefine EVENT__HAVE_STRUCT_ADDRINFO 1

Expand Down