From ef08b09c9459551aabbe7924fb176f1583053cdd Mon Sep 17 00:00:00 2001
From: Greg Hudson <ghudson@mit.edu>
Date: Wed, 21 Jun 2023 10:57:39 -0400
Subject: [PATCH] Ensure array count consistency in kadm5 RPC

In _xdr_kadm5_principal_ent_rec(), ensure that n_key_data matches the
key_data array count when decoding.  Otherwise when the structure is
later freed, xdr_array() could iterate over the wrong number of
elements, either leaking some memory or freeing uninitialized
pointers.  Reported by Robert Morris.

CVE-2023-36054:

An authenticated attacker can cause a kadmind process to crash by
freeing uninitialized pointers.  Remote code execution is unlikely.
An attacker with control of a kadmin server can cause a kadmin client
to crash by freeing uninitialized pointers.

ticket: 9099 (new)
tags: pullup
target_version: 1.21-next
target_version: 1.20-next
---
 src/lib/kadm5/kadm_rpc_xdr.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/lib/kadm5/kadm_rpc_xdr.c b/src/lib/kadm5/kadm_rpc_xdr.c
index 0411c3fd3..287cae750 100644
--- a/src/lib/kadm5/kadm_rpc_xdr.c
+++ b/src/lib/kadm5/kadm_rpc_xdr.c
@@ -390,6 +390,7 @@ _xdr_kadm5_principal_ent_rec(XDR *xdrs, kadm5_principal_ent_rec *objp,
 			     int v)
 {
 	unsigned int n;
+	bool_t r;
 
 	if (!xdr_krb5_principal(xdrs, &objp->principal)) {
 		return (FALSE);
@@ -443,6 +444,9 @@ _xdr_kadm5_principal_ent_rec(XDR *xdrs, kadm5_principal_ent_rec *objp,
 	if (!xdr_krb5_int16(xdrs, &objp->n_key_data)) {
 		return (FALSE);
 	}
+	if (xdrs->x_op == XDR_DECODE && objp->n_key_data < 0) {
+		return (FALSE);
+	}
 	if (!xdr_krb5_int16(xdrs, &objp->n_tl_data)) {
 		return (FALSE);
 	}
@@ -451,9 +455,10 @@ _xdr_kadm5_principal_ent_rec(XDR *xdrs, kadm5_principal_ent_rec *objp,
 		return FALSE;
 	}
 	n = objp->n_key_data;
-	if (!xdr_array(xdrs, (caddr_t *) &objp->key_data,
-		       &n, ~0, sizeof(krb5_key_data),
-		       xdr_krb5_key_data_nocontents)) {
+	r = xdr_array(xdrs, (caddr_t *) &objp->key_data, &n, objp->n_key_data,
+		      sizeof(krb5_key_data), xdr_krb5_key_data_nocontents);
+	objp->n_key_data = n;
+	if (!r) {
 		return (FALSE);
 	}
 
-- 
2.41.0.windows.3

