Simplify BIGNUM handling in dsa_builtin_keygen().

Rather than having complicated "attempt to reuse" dances, always allocate
priv_key/pub_key, then free and assign on success.

ok tb@

1 files changed, 17 insertions, 18 deletions

diff --git a/src/lib/libcrypto/dsa/dsa_key.c b/src/lib/libcrypto/dsa/dsa_key.c
index 051c812781..890f991df9 100644
--- a/src/lib/libcrypto/dsa/dsa_key.c
+++ b/src/lib/libcrypto/dsa/dsa_key.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: dsa_key.c,v 1.32 2022/11/26 16:08:52 tb Exp $ */
+/* $OpenBSD: dsa_key.c,v 1.33 2023/01/11 04:35:26 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -82,39 +82,38 @@ DSA_generate_key(DSA *dsa)
 static int
 dsa_builtin_keygen(DSA *dsa)
 {
-        int ok = 0;
-        BN_CTX *ctx = NULL;
         BIGNUM *pub_key = NULL, *priv_key = NULL;
+        BN_CTX *ctx = NULL;
+        int ok = 0;
 
-        if ((ctx = BN_CTX_new()) == NULL)
+        if ((priv_key = BN_new()) == NULL)
+                goto err;
+        if ((pub_key = BN_new()) == NULL)
                 goto err;
 
-        if ((priv_key = dsa->priv_key) == NULL) {
-                if ((priv_key = BN_new()) == NULL)
-                        goto err;
-        }
+        if ((ctx = BN_CTX_new()) == NULL)
+                goto err;
 
         if (!bn_rand_interval(priv_key, BN_value_one(), dsa->q))
                 goto err;
-
-        if ((pub_key = dsa->pub_key) == NULL) {
-                if ((pub_key = BN_new()) == NULL)
-                        goto err;
-        }
-
         if (!BN_mod_exp_ct(pub_key, dsa->g, priv_key, dsa->p, ctx))
                 goto err;
 
+        BN_free(dsa->priv_key);
         dsa->priv_key = priv_key;
+        priv_key = NULL;
+
+        BN_free(dsa->pub_key);
         dsa->pub_key = pub_key;
+        pub_key = NULL;
+
         ok = 1;
 
  err:
-        if (dsa->pub_key == NULL)
-                BN_free(pub_key);
-        if (dsa->priv_key == NULL)
-                BN_free(priv_key);
+        BN_free(pub_key);
+        BN_free(priv_key);
         BN_CTX_free(ctx);
+
         return ok;
 }
 #endif