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

diff --git a/lib/libcrypto/dsa/dsa_asn1.c b/lib/libcrypto/dsa/dsa_asn1.c
index b6482e5..87b930d 100644 (file)
--- a/lib/libcrypto/dsa/dsa_asn1.c
+++ b/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;
 }