Various fixes in {dh,dsa}_priv_encode()

Avoid creating an ASN1_STRING with negative length, set type, data
and length via ASN1_STRING_type_new() and ASN1_STRING_set0() instead
of doing this manually. Check return value for i2d_ASN1_INTEGER()
and use an intermediate ASN1_OBJECT instead of nested function calls.
Finally, clear sensitive data with freezero().

ok jsing

1 files changed, 24 insertions, 19 deletions

diff --git a/src/lib/libcrypto/dsa/dsa_ameth.c b/src/lib/libcrypto/dsa/dsa_ameth.c
index 5a0c3116aa..ad5aa09cd0 100644
--- a/src/lib/libcrypto/dsa/dsa_ameth.c
+++ b/src/lib/libcrypto/dsa/dsa_ameth.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: dsa_ameth.c,v 1.43 2023/07/07 06:59:18 tb Exp $ */
+/* $OpenBSD: dsa_ameth.c,v 1.44 2023/08/10 09:43:51 tb Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project 2006.
  */
@@ -265,46 +265,51 @@ done:
 static int
 dsa_priv_encode(PKCS8_PRIV_KEY_INFO *p8, const EVP_PKEY *pkey)
 {
+        const DSA *dsa = pkey->pkey.dsa;
         ASN1_STRING *params = NULL;
         ASN1_INTEGER *prkey = NULL;
-        unsigned char *dp = NULL;
-        int dplen;
+        ASN1_OBJECT *aobj;
+        unsigned char *data = NULL, *dp = NULL;
+        int datalen = 0, dplen = 0;
 
-        params = ASN1_STRING_new();
-        if (!params) {
+        if ((datalen = i2d_DSAparams(dsa, &data)) <= 0) {
                 DSAerror(ERR_R_MALLOC_FAILURE);
+                datalen = 0;
                 goto err;
         }
-
-        params->length = i2d_DSAparams(pkey->pkey.dsa, &params->data);
-        if (params->length <= 0) {
+        if ((params = ASN1_STRING_type_new(V_ASN1_SEQUENCE)) == NULL) {
                 DSAerror(ERR_R_MALLOC_FAILURE);
                 goto err;
         }
-        params->type = V_ASN1_SEQUENCE;
+        ASN1_STRING_set0(params, data, datalen);
+        data = NULL;
+        datalen = 0;
 
-        /* Get private key into integer */
-        prkey = BN_to_ASN1_INTEGER(pkey->pkey.dsa->priv_key, NULL);
-        if (!prkey) {
+        if ((prkey = BN_to_ASN1_INTEGER(dsa->priv_key, NULL)) == NULL) {
                 DSAerror(DSA_R_BN_ERROR);
                 goto err;
         }
-
-        dplen = i2d_ASN1_INTEGER(prkey, &dp);
-
+        if ((dplen = i2d_ASN1_INTEGER(prkey, &dp)) <= 0) {
+                DSAerror(ERR_R_MALLOC_FAILURE);
+                dplen = 0;
+                goto err;
+        }
         ASN1_INTEGER_free(prkey);
         prkey = NULL;
 
-        if (!PKCS8_pkey_set0(p8, OBJ_nid2obj(NID_dsa), 0, V_ASN1_SEQUENCE,
-            params, dp, dplen))
+        if ((aobj = OBJ_nid2obj(NID_dsa)) == NULL)
+                goto err;
+        if (!PKCS8_pkey_set0(p8, aobj, 0, V_ASN1_SEQUENCE, params, dp, dplen))
                 goto err;
 
         return 1;
 
-err:
-        free(dp);
+ err:
         ASN1_STRING_free(params);
         ASN1_INTEGER_free(prkey);
+        freezero(data, datalen);
+        freezero(dp, dplen);
+
         return 0;
 }