Plug leaks due to misuse of PKCS7_add_signed_attribute()

set0/add0 functions that can fail are the worst. Without fail this trips
up both users and authors (by and large these are two identical groups
consisting of a single person), resulting in leaks and double frees.

In today's episode of spelunking in the gruesome gore provided by the
PKCS#7 and Time-Stamp protocol "implementations", we fix a couple of
leaks in PKCS7_add_attrib_smimecap() and ESS_add_signing_cert().

We do so by recalling that there is i2d_X509_ALGORS(), so we might
as well put it to use instead of inlining it poorly (aka, without
error checking). Normalize said error checking and ensure ownership
is handled correctly in the usual single-exit idiom.

ESS_add_signing_cert() can also make use of proper i2d handling, so
it's simpler and correct and in the end looks pretty much the same
as PKCS7_add_attrib_smimecap().

ok kenjiro

1 files changed, 22 insertions, 18 deletions

diff --git a/src/lib/libcrypto/ts/ts_rsp_sign.c b/src/lib/libcrypto/ts/ts_rsp_sign.c
index d35f6a7c94..b8cc7e2baf 100644
--- a/src/lib/libcrypto/ts/ts_rsp_sign.c
+++ b/src/lib/libcrypto/ts/ts_rsp_sign.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ts_rsp_sign.c,v 1.36 2025/05/10 05:54:39 tb Exp $ */
+/* $OpenBSD: ts_rsp_sign.c,v 1.37 2025/07/31 02:02:35 tb Exp $ */
 /* Written by Zoltan Glozik (zglozik@stones.com) for the OpenSSL
  * project 2002.
  */
@@ -955,28 +955,32 @@ static int
 ESS_add_signing_cert(PKCS7_SIGNER_INFO *si, ESS_SIGNING_CERT *sc)
 {
         ASN1_STRING *seq = NULL;
-        unsigned char *p, *pp = NULL;
-        int len;
+        unsigned char *data = NULL;
+        int len = 0;
+        int ret = 0;
 
-        len = i2d_ESS_SIGNING_CERT(sc, NULL);
-        if (!(pp = malloc(len))) {
-                TSerror(ERR_R_MALLOC_FAILURE);
+        if ((len = i2d_ESS_SIGNING_CERT(sc, &data)) <= 0) {
+                len = 0;
                 goto err;
         }
-        p = pp;
-        i2d_ESS_SIGNING_CERT(sc, &p);
-        if (!(seq = ASN1_STRING_new()) || !ASN1_STRING_set(seq, pp, len)) {
-                TSerror(ERR_R_MALLOC_FAILURE);
+
+        if ((seq = ASN1_STRING_new()) == NULL)
                 goto err;
-        }
-        free(pp);
-        pp = NULL;
-        return PKCS7_add_signed_attribute(si,
-            NID_id_smime_aa_signingCertificate, V_ASN1_SEQUENCE, seq);
 
-err:
+        ASN1_STRING_set0(seq, data, len);
+        data = NULL;
+        len = 0;
+
+        if (!PKCS7_add_signed_attribute(si, NID_id_smime_aa_signingCertificate,
+            V_ASN1_SEQUENCE, seq))
+                goto err;
+        seq = NULL;
+
+        ret = 1;
+
+ err:
         ASN1_STRING_free(seq);
-        free(pp);
+        freezero(data, len);
 
-        return 0;
+        return ret;
 }