drbg_lib: avoid NULL pointer dereference in drbg_add

Found by Coverity Scan

Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7511)

diff --git a/crypto/rand/drbg_lib.c b/crypto/rand/drbg_lib.c
index ec4aa69db50a3a57690770fbc4596e08f7b182f2..796ab67fda67a4820d0b3dc174a583f36d39da48 100644 (file)
--- a/crypto/rand/drbg_lib.c
+++ b/crypto/rand/drbg_lib.c
@@ -1086,7 +1086,7 @@ static int drbg_add(const void *buf, int num, double randomness)
     int ret = 0;
     RAND_DRBG *drbg = RAND_DRBG_get0_master();
     size_t buflen;
-    size_t seedlen = rand_drbg_seedlen(drbg);
+    size_t seedlen;
 
     if (drbg == NULL)
         return 0;
@@ -1094,6 +1094,8 @@ static int drbg_add(const void *buf, int num, double randomness)
     if (num < 0 || randomness < 0.0)
         return 0;
 
+    seedlen = rand_drbg_seedlen(drbg);
+
     buflen = (size_t)num;
 
     if (buflen < seedlen || randomness < (double) seedlen) {