Use X509_ALGOR_get0() in ecdh_cms_set_shared_info()

This makes things slightly less gross since it involves less reaching
into nested ASN.1 structures.  But don't get the idea that this means
the code is now clean.

ok jsing

1 files changed, 14 insertions, 6 deletions

diff --git a/src/lib/libcrypto/ec/ec_ameth.c b/src/lib/libcrypto/ec/ec_ameth.c
index 883832ff7d..313d21823d 100644
--- a/src/lib/libcrypto/ec/ec_ameth.c
+++ b/src/lib/libcrypto/ec/ec_ameth.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ec_ameth.c,v 1.65 2024/04/18 11:51:53 tb Exp $ */
+/* $OpenBSD: ec_ameth.c,v 1.66 2024/04/18 11:53:40 tb Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project 2006.
  */
@@ -820,6 +820,10 @@ static int
 ecdh_cms_set_shared_info(EVP_PKEY_CTX *pctx, CMS_RecipientInfo *ri)
 {
         X509_ALGOR *alg, *kekalg = NULL;
+        const ASN1_OBJECT *obj;
+        int nid;
+        const void *parameter;
+        int parameter_type;
         ASN1_OCTET_STRING *ukm;
         const unsigned char *p;
         unsigned char *der = NULL;
@@ -831,16 +835,20 @@ ecdh_cms_set_shared_info(EVP_PKEY_CTX *pctx, CMS_RecipientInfo *ri)
         if (!CMS_RecipientInfo_kari_get0_alg(ri, &alg, &ukm))
                 goto err;
 
-        if (!ecdh_cms_set_kdf_param(pctx, OBJ_obj2nid(alg->algorithm))) {
+        X509_ALGOR_get0(&obj, &parameter_type, &parameter, alg);
+
+        if ((nid = OBJ_obj2nid(obj)) == NID_undef)
+                goto err;
+        if (!ecdh_cms_set_kdf_param(pctx, nid)) {
                 ECerror(EC_R_KDF_PARAMETER_ERROR);
                 goto err;
         }
 
-        if (alg->parameter->type != V_ASN1_SEQUENCE)
+        if (parameter_type != V_ASN1_SEQUENCE)
                 goto err;
-
-        p = alg->parameter->value.sequence->data;
-        plen = alg->parameter->value.sequence->length;
+        if ((p = ASN1_STRING_get0_data(parameter)) == NULL)
+                goto err;
+        plen = ASN1_STRING_length(parameter);
         if ((kekalg = d2i_X509_ALGOR(NULL, &p, plen)) == NULL)
                 goto err;
         if ((kekctx = CMS_RecipientInfo_kari_get0_ctx(ri)) == NULL)