drbg: add fork id to additional data on UNIX systems

Provides a little extra fork-safety on UNIX systems, adding to the
fact that all DRBGs reseed automatically when the fork_id changes.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9832)

diff --git a/crypto/rand/rand_unix.c b/crypto/rand/rand_unix.c
index 813964665f9b443e0203eee644ecf758416a2ede..8641badbff81ee6592afed516f03fdee9a098d1a 100644 (file)
--- a/crypto/rand/rand_unix.c
+++ b/crypto/rand/rand_unix.c
@@ -704,6 +704,7 @@ int rand_pool_add_nonce_data(RAND_POOL *pool)
 int rand_pool_add_additional_data(RAND_POOL *pool)
 {
     struct {
+        int fork_id;
         CRYPTO_THREAD_ID tid;
         uint64_t time;
     } data;
@@ -713,9 +714,11 @@ int rand_pool_add_additional_data(RAND_POOL *pool)
 
     /*
      * Add some noise from the thread id and a high resolution timer.
+     * The fork_id adds some extra fork-safety.
      * The thread id adds a little randomness if the drbg is accessed
      * concurrently (which is the case for the <master> drbg).
      */
+    data.fork_id = openssl_get_fork_id();
     data.tid = CRYPTO_THREAD_get_current_id();
     data.time = get_timer_bits();