Fix a NULL ptr deref in error path in tls_process_cke_dhe()

Fixes #6574

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6594)

diff --git a/ssl/statem/statem_srvr.c b/ssl/statem/statem_srvr.c
index 5591e1e584280d9988c8359af930f1c2d5e7b034..10301f1643897e501fd55b393568898c7dffea52 100644 (file)
--- a/ssl/statem/statem_srvr.c
+++ b/ssl/statem/statem_srvr.c
@@ -2324,13 +2324,12 @@ static int tls_process_cke_dhe(SSL *s, PACKET *pkt, int *al)
         SSLerr(SSL_F_TLS_PROCESS_CKE_DHE, SSL_R_BN_LIB);
         goto err;
     }
+
     cdh = EVP_PKEY_get0_DH(ckey);
     pub_key = BN_bin2bn(data, i, NULL);
-
-    if (pub_key == NULL || !DH_set0_key(cdh, pub_key, NULL)) {
+    if (pub_key == NULL || cdh == NULL || !DH_set0_key(cdh, pub_key, NULL)) {
         SSLerr(SSL_F_TLS_PROCESS_CKE_DHE, ERR_R_INTERNAL_ERROR);
-        if (pub_key != NULL)
-            BN_free(pub_key);
+        BN_free(pub_key);
         goto err;
     }