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rand_unix.c: don't discard entropy bytes from syscall_random()

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Fixes #6978

Don't discard partial reads from syscall_random() and retry instead.

Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6990)
This commit is contained in:
Dr. Matthias St. Pierre 2018-08-16 21:05:47 +02:00
parent 9b5f1c8fd8
commit 630ce41e83
1 changed files with 17 additions and 9 deletions
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26
crypto/rand/rand_unix.c
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@ -458,17 +458,25 @@ size_t rand_pool_acquire_entropy(RAND_POOL *pool)
unsigned char *buffer;
# ifdef OPENSSL_RAND_SEED_GETRANDOM
bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
buffer = rand_pool_add_begin(pool, bytes_needed);
if (buffer != NULL) {
size_t bytes = 0;
{
ssize_t bytes;
/* Maximum allowed number of consecutive unsuccessful attempts */
int attempts = 3;
if (syscall_random(buffer, bytes_needed) == (int)bytes_needed)
bytes = bytes_needed;
rand_pool_add_end(pool, bytes, 8 * bytes);
entropy_available = rand_pool_entropy_available(pool);
bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
while (bytes_needed != 0 && attempts-- > 0) {
buffer = rand_pool_add_begin(pool, bytes_needed);
bytes = syscall_random(buffer, bytes_needed);
if (bytes > 0) {
rand_pool_add_end(pool, bytes, 8 * bytes);
bytes_needed -= bytes;
attempts = 3; /* reset counter after successful attempt */
} else if (bytes < 0 && errno != EINTR) {
break;
}
}
}
entropy_available = rand_pool_entropy_available(pool);
if (entropy_available > 0)
return entropy_available;
# endif