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Implement tagging memory with MAP_INHERIT_ZERO on FreeBSD and OpenBSD
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@torben-hansen
torben-hansen committed Dec 31, 2024
1 parent 2459c63 commit 45cc105
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Showing 2 changed files with 121 additions and 40 deletions.
151 changes: 111 additions & 40 deletions crypto/ube/fork_detect.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -12,29 +12,30 @@
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#if !defined(_GNU_SOURCE)
#define _GNU_SOURCE // needed for madvise() and MAP_ANONYMOUS on Linux.
#endif

#include <openssl/base.h>

#include "fork_detect.h"
#include <openssl/target.h>

#if defined(OPENSSL_LINUX)
#include <sys/mman.h>
#include <unistd.h>
#include <stdlib.h>
#define AWSLC_FORK_DETECTION_SUPPORTED
#if !defined(_GNU_SOURCE)
#define _GNU_SOURCE // needed for madvise() and MAP_ANONYMOUS.
#endif
#elif defined(OPENSSL_FREEBSD) || defined(OPENSSL_OPENBSD)
/* FreeBSD requires POSIX compatibility off for its syscalls (enables __BSD_VISIBLE)
* Without the below line, <sys/mman.h> cannot be imported (it requires __BSD_VISIBLE) */
#undef _POSIX_C_SOURCE
#elif defined(OPENSSL_WINDOWS) || defined(OPENSSL_TRUSTY)
#define AWSLC_PLATFORM_DOES_NOT_FORK
#endif

#if defined(AWSLC_FORK_DETECTION_SUPPORTED)

#include <openssl/base.h>
#include <openssl/type_check.h>

#include "fork_detect.h"
#include "../internal.h"


#if defined(MADV_WIPEONFORK)
OPENSSL_STATIC_ASSERT(MADV_WIPEONFORK == 18, MADV_WIPEONFORK_is_not_18)
#else
#define MADV_WIPEONFORK 18
#endif
#include <stdlib.h>

static CRYPTO_once_t fork_detect_once = CRYPTO_ONCE_INIT;
static struct CRYPTO_STATIC_MUTEX fork_detect_lock = CRYPTO_STATIC_MUTEX_INIT;
Expand All @@ -45,24 +46,30 @@ static struct CRYPTO_STATIC_MUTEX fork_detect_lock = CRYPTO_STATIC_MUTEX_INIT;
static volatile char *fork_detect_addr = NULL;
static uint64_t fork_generation = 0;
static int ignore_madv_wipeonfork = 0;
static int ignore_madv_inheritzero = 0;

static int ignore_all_fork_detection(void) {
if (ignore_madv_wipeonfork == 1 &&
ignore_madv_inheritzero == 1) {
return 1;
}
return 0;
}

static int init_fork_detect_madv_wipeonfork(void **addr_out) {
#if defined(OPENSSL_LINUX)

void *addr = MAP_FAILED;
long page_size = 0;
#include <sys/mman.h>
#include <unistd.h>

GUARD_PTR(addr_out);
#if defined(MADV_WIPEONFORK)
OPENSSL_STATIC_ASSERT(MADV_WIPEONFORK == 18, MADV_WIPEONFORK_is_not_18)
#else
#define MADV_WIPEONFORK 18
#endif

page_size = sysconf(_SC_PAGESIZE);
if (page_size <= 0) {
return 0;
}
static int init_fork_detect_madv_wipeonfork(void *addr, long page_size) {

addr = mmap(NULL, (size_t)page_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (addr == MAP_FAILED) {
return 0;
}
GUARD_PTR(addr);

// Some versions of qemu (up to at least 5.0.0-rc4, see linux-user/syscall.c)
// ignore |madvise| calls and just return zero (i.e. success). But we need to
Expand All @@ -71,26 +78,86 @@ static int init_fork_detect_madv_wipeonfork(void **addr_out) {
// unknown |advice| values.
if (madvise(addr, (size_t)page_size, -1) == 0 ||
madvise(addr, (size_t)page_size, MADV_WIPEONFORK) != 0) {
// The mapping |addr| points to is unmapped by caller.
munmap(addr, (size_t)page_size);
return 0;
}

*addr_out = addr;
return 1;
}

#else // defined(OPENSSL_LINUX)

static int init_fork_detect_madv_wipeonfork(void *addr, long page_size) {
return 0;
}

#endif // defined(OPENSSL_LINUX)


#if defined(OPENSSL_FREEBSD) || defined(OPENSSL_OPENBSD)

#include <sys/mman.h>
#include <unistd.h>

static int init_fork_detect_madv_inheritzero(void *addr, long page_size) {

GUARD_PTR(addr);

if (minherit(addr, page_size, MAP_INHERIT_ZERO) != 0) {
return 0;
}

return 1;
}

#else // defined(OPENSSL_FREEBSD) || defined(OPENSSL_OPENBSD)

static int init_fork_detect_madv_inheritzero(void *addr, long page_size) {
return 0;
}

#endif // defined(OPENSSL_FREEBSD) || defined(OPENSSL_OPENBSD)


static int init_fork_detect_methods(void *addr, long page_size) {

if (ignore_madv_wipeonfork != 1 &&
init_fork_detect_madv_wipeonfork(addr, page_size) == 1) {
return 1;
}

if (ignore_madv_inheritzero != 1 &&
init_fork_detect_madv_inheritzero(addr, page_size) == 1) {
return 1;
}

return 0;
}

static void init_fork_detect(void) {

void *addr = NULL;
void *addr = MAP_FAILED;
long page_size = 0;

if (ignore_all_fork_detection() == 1) {
return;
}

page_size = sysconf(_SC_PAGESIZE);
if (page_size <= 0) {
return;
}

// Check whether we are completely ignoring fork detection. This is only done
// during testing.
if (ignore_madv_wipeonfork == 1) {
addr = mmap(NULL, (size_t)page_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (addr == MAP_FAILED) {
return;
}

if (init_fork_detect_madv_wipeonfork(&addr) != 1) {
if (init_fork_detect_methods(addr, page_size) != 1) {
// No reason to verify return value of munmap() since we can't use that
// information for anything anyway.
munmap(addr, (size_t) page_size);
addr = NULL;
return;
}

Expand All @@ -115,7 +182,7 @@ uint64_t CRYPTO_get_fork_generation(void) {

volatile char *const flag_ptr = fork_detect_addr;
if (flag_ptr == NULL) {
// Our kernel is too old to support |MADV_WIPEONFORK|.
// Our kernel does not support fork detection.
return 0;
}

Expand Down Expand Up @@ -150,7 +217,11 @@ void CRYPTO_fork_detect_ignore_madv_wipeonfork_FOR_TESTING(void) {
ignore_madv_wipeonfork = 1;
}

#elif defined(OPENSSL_WINDOWS) || defined(OPENSSL_TRUSTY)
void CRYPTO_fork_detect_ignore_madv_inheritzero_FOR_TESTING(void) {
ignore_madv_inheritzero = 1;
}

#elif defined(AWSLC_PLATFORM_DOES_NOT_FORK)

// These platforms are guaranteed not to fork, and therefore do not require
// fork detection support. Returning a constant non zero value makes BoringSSL
Expand All @@ -166,4 +237,4 @@ uint64_t CRYPTO_get_fork_generation(void) { return 0xc0ffee; }
// every RAND_bytes call.
uint64_t CRYPTO_get_fork_generation(void) { return 0; }

#endif
#endif // defined(AWSLC_FORK_DETECTION_SUPPORTED)
10 changes: 10 additions & 0 deletions crypto/ube/fork_detect.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,11 @@
extern "C" {
#endif

#if defined(OPENSSL_LINUX) || defined(OPENSSL_FREEBSD) || defined(OPENSSL_OPENBSD)
#define AWSLC_FORK_DETECTION_SUPPORTED
#elif defined(OPENSSL_WINDOWS) || defined(OPENSSL_TRUSTY)
#define AWSLC_PLATFORM_DOES_NOT_FORK
#endif

// crypto_get_fork_generation returns the fork generation number for the current
// process, or zero if not supported on the platform. The fork generation number
Expand All @@ -42,6 +47,11 @@ OPENSSL_EXPORT uint64_t CRYPTO_get_fork_generation(void);
// used for testing purposes.
OPENSSL_EXPORT void CRYPTO_fork_detect_ignore_madv_wipeonfork_FOR_TESTING(void);

// CRYPTO_fork_detect_ignore_madv_inheritzero_FOR_TESTING is an internal detail
// used for testing purposes.
OPENSSL_EXPORT void CRYPTO_fork_detect_ignore_madv_inheritzero_FOR_TESTING(void);


#if defined(__cplusplus)
} // extern C
#endif
Expand Down

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