Add return value NULL checks that were missing

Issues located by Brian Carpenter of Geeknik's Farm.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17007)

(cherry picked from commit ed5b26ce0b34ec00bdd53d15854a22bccbb4d415)

1 files changed, 2 insertions, 0 deletions

diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 9345838f6a..fc32bb3556 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -1267,6 +1267,8 @@ static const SIGALG_LOOKUP *tls1_get_legacy_sigalg(const SSL *s, int idx)
             for (i = 0; i < SSL_PKEY_NUM; i++) {
                 const SSL_CERT_LOOKUP *clu = ssl_cert_lookup_by_idx(i);
 
+                if (clu == NULL)
+                    continue;
                 if (clu->amask & s->s3.tmp.new_cipher->algorithm_auth) {
                     idx = i;
                     break;