CVE-2023-51384 (C, published 2023-12-18T19:15Z)
Description: value: In ssh-agent in OpenSSH before 9.6, certain destination constraints can be incompletely applied. When destination constraints are specified during addition of PKCS#11-hosted private keys, these constraints are only applied to the first key, even if a PKCS#11 token returns multiple keys.
Severity: nan (CVSS v3 base score: 5.5)
Weakness: NVD-CWE-noinfo \u2014 Insufficient Information
There is insufficient information about the issue to classify it; details are unkown or unspecified.
Repository: https://github.com/openssh/openssh-portable
Files changed:
ssh-agent.c
Commit message: upstream: apply destination constraints to all p11 keys

Previously applied only to the first key returned from each token.

ok markus@

OpenBSD-Commit-ID: 36df3afb8eb94eec6b2541f063d0d164ef8b488d


Vulnerable code:
/* $OpenBSD: ssh-agent.c,v 1.300 2023/07/19 13:56:33 djm Exp $ */
	u_int nentries = 0;
			id->dest_constraints = dest_constraints;
			dest_constraints = NULL; /* transferred */
			ndest_constraints = 0;

Fixed code:
/* $OpenBSD: ssh-agent.c,v 1.301 2023/12/18 14:46:12 djm Exp $ */
static void
dup_dest_constraint_hop(const struct dest_constraint_hop *dch,
    struct dest_constraint_hop *out)
{
	u_int i;
	int r;

	out->user = dch->user == NULL ? NULL : xstrdup(dch->user);
	out->hostname = dch->hostname == NULL ? NULL : xstrdup(dch->hostname);
	out->is_ca = dch->is_ca;
	out->nkeys = dch->nkeys;
	out->keys = out->nkeys == 0 ? NULL :
	    xcalloc(out->nkeys, sizeof(*out->keys));
	out->key_is_ca = out->nkeys == 0 ? NULL :
	    xcalloc(out->nkeys, sizeof(*out->key_is_ca));
	for (i = 0; i < dch->nkeys; i++) {
		if (dch->keys[i] != NULL &&
		    (r = sshkey_from_private(dch->keys[i],
		    &(out->keys[i]))) != 0)
			fatal_fr(r, "copy key");
		out->key_is_ca[i] = dch->key_is_ca[i];
	}
}

static struct dest_constraint *
dup_dest_constraints(const struct dest_constraint *dcs, size_t ndcs)
{
	size_t i;
	struct dest_constraint *ret;

	if (ndcs == 0)
		return NULL;
	ret = xcalloc(ndcs, sizeof(*ret));
	for (i = 0; i < ndcs; i++) {
		dup_dest_constraint_hop(&dcs[i].from, &ret[i].from);
		dup_dest_constraint_hop(&dcs[i].to, &ret[i].to);
	}
	return ret;
}

#ifdef DEBUG_CONSTRAINTS
static void
dump_dest_constraint_hop(const struct dest_constraint_hop *dch)
{
	u_int i;
	char *fp;

	debug_f("user %s hostname %s is_ca %d nkeys %u",
	    dch->user == NULL ? "(null)" : dch->user,
	    dch->hostname == NULL ? "(null)" : dch->hostname,
	    dch->is_ca, dch->nkeys);
	for (i = 0; i < dch->nkeys; i++) {
		fp = NULL;
		if (dch->keys[i] != NULL &&
		    (fp = sshkey_fingerprint(dch->keys[i],
		    SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL)
			fatal_f("fingerprint failed");
		debug_f("key %u/%u: %s%s%s key_is_ca %d", i, dch->nkeys,
		    dch->keys[i] == NULL ? "" : sshkey_ssh_name(dch->keys[i]),
		    dch->keys[i] == NULL ? "" : " ",
		    dch->keys[i] == NULL ? "none" : fp,
		    dch->key_is_ca[i]);
		free(fp);
	}
}
#endif /* DEBUG_CONSTRAINTS */

static void
dump_dest_constraints(const char *context,
    const struct dest_constraint *dcs, size_t ndcs)
{
#ifdef DEBUG_CONSTRAINTS
	size_t i;

	debug_f("%s: %zu constraints", context, ndcs);
	for (i = 0; i < ndcs; i++) {
		debug_f("constraint %zu / %zu: from: ", i, ndcs);
		dump_dest_constraint_hop(&dcs[i].from);
		debug_f("constraint %zu / %zu: to: ", i, ndcs);
		dump_dest_constraint_hop(&dcs[i].to);
	}
	debug_f("done for %s", context);
#endif /* DEBUG_CONSTRAINTS */
}

	u_int i = 0, nentries = 0;
	char *fp;
		if ((fp = sshkey_fingerprint(id->key, SSH_FP_HASH_DEFAULT,
		    SSH_FP_DEFAULT)) == NULL)
			fatal_f("fingerprint failed");
		debug_f("key %u / %u: %s %s", i++, idtab->nentries,
		    sshkey_ssh_name(id->key), fp);
		dump_dest_constraints(__func__,
		    id->dest_constraints, id->ndest_constraints);
		free(fp);
	dump_dest_constraints(__func__, dest_constraints, ndest_constraints);
	dump_dest_constraints(__func__, dest_constraints, ndest_constraints);
			id->dest_constraints = dup_dest_constraints(
			    dest_constraints, ndest_constraints);