[Qemu-devel] [PATCH v2 1/3] qemu-bridge-helper: restrict interface name to IFNAMSIZ

[P J P <ppandit@redhat.com>]

From: Prasad J Pandit <pjp@fedoraproject.org>

The interface names in qemu-bridge-helper are defined to be
of size IFNAMSIZ(=16), including the terminating null('\0') byte.
The same is applied to interface names read from 'bridge.conf'
file to form ACLs rules. If user supplied '--br=bridge' name
is not restricted to the same length, it could lead to ACL bypass
issue. Restrict interface name to IFNAMSIZ, including null byte.

Reported-by: Riccardo Schirone <rschiron@redhat.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 qemu-bridge-helper.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

Update v2: report an error and exit
  -> https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg06239.html

diff --git a/qemu-bridge-helper.c b/qemu-bridge-helper.c
index f9940deefd..8ec0a65174 100644
--- a/qemu-bridge-helper.c
+++ b/qemu-bridge-helper.c
@@ -109,6 +109,13 @@ static int parse_acl_file(const char *filename, ACLList *acl_list)
         }
         *argend = 0;
 
+        if (strcmp(cmd, "include") && strlen(arg) >= IFNAMSIZ) {
+            fprintf(stderr, "name `%s' too long: %lu\n", arg, strlen(arg));
+            fclose(f);
+            errno = EINVAL;
+            return -1;
+        }
+
         if (strcmp(cmd, "deny") == 0) {
             acl_rule = g_malloc(sizeof(*acl_rule));
             if (strcmp(arg, "all") == 0) {
@@ -259,6 +266,10 @@ int main(int argc, char **argv)
         usage();
         return EXIT_FAILURE;
     }
+    if (strlen(bridge) >= IFNAMSIZ) {
+        fprintf(stderr, "name `%s' too long: %lu\n", bridge, strlen(bridge));
+        return EXIT_FAILURE;
+    }
 
     /* parse default acl file */
     QSIMPLEQ_INIT(&acl_list);
-- 
2.21.0