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Tighten up getrandom handling.

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While I don't believe EINTR can occur with a non-blocking getrandom call
when talking to the kernel directly, that may not be true when certain
sandboxing systems are being used.

Additionally, with this change we will no longer silently ignore errors
other than ENOSYS.

Update-Note: update internal bug 115344138.

Change-Id: I952c132cf325dcc17dc38e68f054abc41de1f8b0
Reviewed-on: https://boringssl-review.googlesource.com/32006
Reviewed-by: David Benjamin <davidben@google.com>
This commit is contained in:
Adam Langley 2018-09-17 15:15:02 -07:00
parent 4902598935
commit 5ede28c8a4
1 changed files with 38 additions and 30 deletions
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58
crypto/fipsmodule/rand/urandom.c
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@ -73,6 +73,27 @@
#endif // __NR_getrandom
#if defined(OPENSSL_MSAN)
void __msan_unpoison(void *, size_t);
#endif
static ssize_t boringssl_getrandom(void *buf, size_t buf_len, unsigned flags) {
ssize_t ret;
do {
ret = syscall(__NR_getrandom, buf, buf_len, flags);
} while (ret == -1 && errno == EINTR);
#if defined(OPENSSL_MSAN)
if (ret > 0) {
// MSAN doesn't recognise |syscall| and thus doesn't notice that we have
// initialised the output buffer.
__msan_unpoison(buf, ret);
}
#endif // OPENSSL_MSAN
return ret;
}
#endif // EXPECTED_NR_getrandom
#if !defined(GRND_NONBLOCK)
@ -108,28 +129,30 @@ static void init_once(void) {
#if defined(USE_NR_getrandom)
uint8_t dummy;
long getrandom_ret =
syscall(__NR_getrandom, &dummy, sizeof(dummy), GRND_NONBLOCK);
ssize_t getrandom_ret =
boringssl_getrandom(&dummy, sizeof(dummy), GRND_NONBLOCK);
if (getrandom_ret == 1) {
*urandom_fd_bss_get() = kHaveGetrandom;
return;
} else if (getrandom_ret == -1 && errno == EAGAIN) {
if (getrandom_ret == -1 && errno == EAGAIN) {
fprintf(
stderr,
"getrandom indicates that the entropy pool has not been initialized. "
"Rather than continue with poor entropy, this process will block until "
"entropy is available.\n");
do {
getrandom_ret =
syscall(__NR_getrandom, &dummy, sizeof(dummy), 0 /* no flags */);
} while (getrandom_ret == -1 && errno == EINTR);
boringssl_getrandom(&dummy, sizeof(dummy), 0 /* no flags */);
}
if (getrandom_ret == 1) {
*urandom_fd_bss_get() = kHaveGetrandom;
return;
}
// Ignore ENOSYS and fallthrough to using /dev/urandom, below. Otherwise it's
// a fatal error.
if (getrandom_ret != -1 || errno != ENOSYS) {
perror("getrandom");
abort();
}
#endif // USE_NR_getrandom
@ -232,10 +255,6 @@ void RAND_set_urandom_fd(int fd) {
}
}
#if defined(USE_NR_getrandom) && defined(OPENSSL_MSAN)
void __msan_unpoison(void *, size_t);
#endif
// fill_with_entropy writes |len| bytes of entropy into |out|. It returns one
// on success and zero on error.
static char fill_with_entropy(uint8_t *out, size_t len) {
@ -244,18 +263,7 @@ static char fill_with_entropy(uint8_t *out, size_t len) {
if (*urandom_fd_bss_get() == kHaveGetrandom) {
#if defined(USE_NR_getrandom)
do {
r = syscall(__NR_getrandom, out, len, 0 /* no flags */);
} while (r == -1 && errno == EINTR);
#if defined(OPENSSL_MSAN)
if (r > 0) {
// MSAN doesn't recognise |syscall| and thus doesn't notice that we
// have initialised the output buffer.
__msan_unpoison(out, r);
}
#endif // OPENSSL_MSAN
r = boringssl_getrandom(out, len, 0 /* no flags */);
#else // USE_NR_getrandom
fprintf(stderr, "urandom fd corrupt.\n");
abort();