Fix dsa_pub_encode

The return value from ASN1_STRING_new() was not being checked which could
lead to a NULL deref in the event of a malloc failure. Also fixed a mem
leak in the error path.
Reviewed-by: NRich Salz <rsalz@openssl.org>

crypto/dsa/dsa_ameth.c

@@ -129,21 +129,23 @@ static int dsa_pub_decode(EVP_PKEY *pkey, X509_PUBKEY *pubkey)
 static int dsa_pub_encode(X509_PUBKEY *pk, const EVP_PKEY *pkey)
 {
     DSA *dsa;
-    void *pval = NULL;
     int ptype;
     unsigned char *penc = NULL;
     int penclen;
+    ASN1_STRING *str = NULL;
 
     dsa = pkey->pkey.dsa;
     if (pkey->save_parameters && dsa->p && dsa->q && dsa->g) {
-        ASN1_STRING *str;
         str = ASN1_STRING_new();
+        if (!str) {
+            DSAerr(DSA_F_DSA_PUB_ENCODE, ERR_R_MALLOC_FAILURE);
+            goto err;
+        }
         str->length = i2d_DSAparams(dsa, &str->data);
         if (str->length <= 0) {
             DSAerr(DSA_F_DSA_PUB_ENCODE, ERR_R_MALLOC_FAILURE);
             goto err;
         }
-        pval = str;
         ptype = V_ASN1_SEQUENCE;
     } else
         ptype = V_ASN1_UNDEF;
@@ -158,14 +160,14 @@ static int dsa_pub_encode(X509_PUBKEY *pk, const EVP_PKEY *pkey)
     }
 
     if (X509_PUBKEY_set0_param(pk, OBJ_nid2obj(EVP_PKEY_DSA),
-                               ptype, pval, penc, penclen))
+                               ptype, str, penc, penclen))
         return 1;
 
  err:
     if (penc)
         OPENSSL_free(penc);
-    if (pval)
-        ASN1_STRING_free(pval);
+    if (str)
+        ASN1_STRING_free(str);
 
     return 0;
 }