Rework DSA_sign() and DSA_verify()

Change DSA_sign() to single exit and check the signed i2d_DSA_SIG() return
value before assigning it to an unsigned int.

In DSA_verify() let d2i_DSA_SIG() handle the allocation, split error check
of i2d_DSA_SIG() from signature check and change an unnecessary freezero()
to free.

ok jsing

1 files changed, 31 insertions, 20 deletions

diff --git a/src/lib/libcrypto/dsa/dsa_asn1.c b/src/lib/libcrypto/dsa/dsa_asn1.c
index b6482e5064..87b930d5ad 100644
--- a/src/lib/libcrypto/dsa/dsa_asn1.c
+++ b/src/lib/libcrypto/dsa/dsa_asn1.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: dsa_asn1.c,v 1.26 2022/11/19 06:33:00 tb Exp $ */
+/* $OpenBSD: dsa_asn1.c,v 1.27 2022/11/19 11:48:24 tb Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project 2000.
  */
@@ -399,18 +399,27 @@ DSAparams_dup(DSA *dsa)
 
 int
 DSA_sign(int type, const unsigned char *dgst, int dlen, unsigned char *sig,
-    unsigned int *siglen, DSA *dsa)
+    unsigned int *out_siglen, DSA *dsa)
 {
         DSA_SIG *s;
+        int siglen;
+        int ret = 0;
 
-        s = DSA_do_sign(dgst, dlen, dsa);
-        if (s == NULL) {
-                *siglen = 0;
-                return 0;
-        }
-        *siglen = i2d_DSA_SIG(s,&sig);
+        *out_siglen = 0;
+
+        if ((s = DSA_do_sign(dgst, dlen, dsa)) == NULL)
+                goto err;
+
+        if ((siglen = i2d_DSA_SIG(s, &sig)) < 0)
+                goto err;
+
+        *out_siglen = siglen;
+
+        ret = 1;
+ err:
         DSA_SIG_free(s);
-        return 1;
+
+        return ret;
 }
 
 /*
@@ -424,24 +433,26 @@ int
 DSA_verify(int type, const unsigned char *dgst, int dgst_len,
     const unsigned char *sigbuf, int siglen, DSA *dsa)
 {
-        DSA_SIG *s;
+        DSA_SIG *s = NULL;
         unsigned char *der = NULL;
-        const unsigned char *p = sigbuf;
-        int derlen = -1;
+        const unsigned char *p;
         int ret = -1;
 
-        s = DSA_SIG_new();
-        if (s == NULL)
-                return ret;
-        if (d2i_DSA_SIG(&s, &p, siglen) == NULL)
+        p = sigbuf;
+        if ((s = d2i_DSA_SIG(NULL, &p, siglen)) == NULL)
                 goto err;
+
         /* Ensure signature uses DER and doesn't have trailing garbage */
-        derlen = i2d_DSA_SIG(s, &der);
-        if (derlen != siglen || memcmp(sigbuf, der, derlen))
+        if (i2d_DSA_SIG(s, &der) != siglen)
                 goto err;
+
+        if (memcmp(der, sigbuf, siglen) != 0)
+                goto err;
+
         ret = DSA_do_verify(dgst, dgst_len, s, dsa);
-err:
-        freezero(der, derlen);
+ err:
+        free(der);
         DSA_SIG_free(s);
+
         return ret;
 }