avoid a NULL dereference when getting digest

Fixes #16961

Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/16969)

diff --git a/crypto/evp/evp_lib.c b/crypto/evp/evp_lib.c
index 64d7fb046de9c75d1f72ab0f01f6b0c8da89bbfb..24092cfd5be0599ca3fa12994125431ee560cfdc 100644 (file)
--- a/crypto/evp/evp_lib.c
+++ b/crypto/evp/evp_lib.c
@@ -999,7 +999,7 @@ EVP_MD *EVP_MD_CTX_get1_md(EVP_MD_CTX *ctx)
     if (ctx == NULL)
         return NULL;
     md = (EVP_MD *)ctx->reqdigest;
-    if (!EVP_MD_up_ref(md))
+    if (md == NULL || !EVP_MD_up_ref(md))
         return NULL;
     return md;
 }