Description: sd-bus: enforce a size limit for dbus paths, and don't allocate
them on the stacka
Forwarded: no
Patch from: systemd_239-7ubuntu10.8
For information see:
https://usn.ubuntu.com/3891-1/
https://git.launchpad.net/ubuntu/+source/systemd/commit/?id=f8e75d5634904c8e672658856508c3a02f349adb
CVE: CVE-2019-6454
Upstream-Status: Backport
Signed-off-by: George McCollister <george.mccollister@gmail.com>
--- a/src/libsystemd/sd-bus/bus-internal.c
+++ b/src/libsystemd/sd-bus/bus-internal.c
@@ -45,7 +45,7 @@
if (slash)
return false;
- return true;
+ return (q - p) <= BUS_PATH_SIZE_MAX;
}
char* object_path_startswith(const char *a, const char *b) {
--- a/src/libsystemd/sd-bus/bus-internal.h
+++ b/src/libsystemd/sd-bus/bus-internal.h
@@ -333,6 +333,10 @@
#define BUS_MESSAGE_SIZE_MAX (128*1024*1024)
#define BUS_AUTH_SIZE_MAX (64*1024)
+/* Note that the D-Bus specification states that bus paths shall have no size limit. We enforce here one
+ * anyway, since truly unbounded strings are a security problem. The limit we pick is relatively large however,
+ * to not clash unnecessarily with real-life applications. */
+#define BUS_PATH_SIZE_MAX (64*1024)
#define BUS_CONTAINER_DEPTH 128
--- a/src/libsystemd/sd-bus/bus-objects.c
+++ b/src/libsystemd/sd-bus/bus-objects.c
@@ -1134,7 +1134,8 @@
const char *path,
sd_bus_error *error) {
- char *prefix;
+ _cleanup_free_ char *prefix = NULL;
+ size_t pl;
int r;
assert(bus);
@@ -1150,7 +1151,12 @@
return 0;
/* Second, add fallback vtables registered for any of the prefixes */
- prefix = alloca(strlen(path) + 1);
+ pl = strlen(path);
+ assert(pl <= BUS_PATH_SIZE_MAX);
+ prefix = new(char, pl + 1);
+ if (!prefix)
+ return -ENOMEM;
+
OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
r = object_manager_serialize_path(bus, reply, prefix, path, true, error);
if (r < 0)
@@ -1346,6 +1352,7 @@
}
int bus_process_object(sd_bus *bus, sd_bus_message *m) {
+ _cleanup_free_ char *prefix = NULL;
int r;
size_t pl;
bool found_object = false;
@@ -1370,9 +1377,12 @@
assert(m->member);
pl = strlen(m->path);
- do {
- char prefix[pl+1];
+ assert(pl <= BUS_PATH_SIZE_MAX);
+ prefix = new(char, pl + 1);
+ if (!prefix)
+ return -ENOMEM;
+ do {
bus->nodes_modified = false;
r = object_find_and_run(bus, m, m->path, false, &found_object);
@@ -1499,9 +1509,15 @@
n = hashmap_get(bus->nodes, path);
if (!n) {
- char *prefix;
+ _cleanup_free_ char *prefix = NULL;
+ size_t pl;
+
+ pl = strlen(path);
+ assert(pl <= BUS_PATH_SIZE_MAX);
+ prefix = new(char, pl + 1);
+ if (!prefix)
+ return -ENOMEM;
- prefix = alloca(strlen(path) + 1);
OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
n = hashmap_get(bus->nodes, prefix);
if (n)
@@ -2091,8 +2107,9 @@
char **names) {
BUS_DONT_DESTROY(bus);
+ _cleanup_free_ char *prefix = NULL;
bool found_interface = false;
- char *prefix;
+ size_t pl;
int r;
assert_return(bus, -EINVAL);
@@ -2111,6 +2128,12 @@
if (names && names[0] == NULL)
return 0;
+ pl = strlen(path);
+ assert(pl <= BUS_PATH_SIZE_MAX);
+ prefix = new(char, pl + 1);
+ if (!prefix)
+ return -ENOMEM;
+
do {
bus->nodes_modified = false;
@@ -2120,7 +2143,6 @@
if (bus->nodes_modified)
continue;
- prefix = alloca(strlen(path) + 1);
OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
r = emit_properties_changed_on_interface(bus, prefix, path, interface, true, &found_interface, names);
if (r != 0)
@@ -2252,7 +2274,8 @@
static int object_added_append_all(sd_bus *bus, sd_bus_message *m, const char *path) {
_cleanup_set_free_ Set *s = NULL;
- char *prefix;
+ _cleanup_free_ char *prefix = NULL;
+ size_t pl;
int r;
assert(bus);
@@ -2297,7 +2320,12 @@
if (bus->nodes_modified)
return 0;
- prefix = alloca(strlen(path) + 1);
+ pl = strlen(path);
+ assert(pl <= BUS_PATH_SIZE_MAX);
+ prefix = new(char, pl + 1);
+ if (!prefix)
+ return -ENOMEM;
+
OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
r = object_added_append_all_prefix(bus, m, s, prefix, path, true);
if (r < 0)
@@ -2436,7 +2464,8 @@
static int object_removed_append_all(sd_bus *bus, sd_bus_message *m, const char *path) {
_cleanup_set_free_ Set *s = NULL;
- char *prefix;
+ _cleanup_free_ char *prefix = NULL;
+ size_t pl;
int r;
assert(bus);
@@ -2468,7 +2497,12 @@
if (bus->nodes_modified)
return 0;
- prefix = alloca(strlen(path) + 1);
+ pl = strlen(path);
+ assert(pl <= BUS_PATH_SIZE_MAX);
+ prefix = new(char, pl + 1);
+ if (!prefix)
+ return -ENOMEM;
+
OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
r = object_removed_append_all_prefix(bus, m, s, prefix, path, true);
if (r < 0)
@@ -2618,7 +2652,8 @@
const char *path,
const char *interface) {
- char *prefix;
+ _cleanup_free_ char *prefix = NULL;
+ size_t pl;
int r;
assert(bus);
@@ -2632,7 +2667,12 @@
if (bus->nodes_modified)
return 0;
- prefix = alloca(strlen(path) + 1);
+ pl = strlen(path);
+ assert(pl <= BUS_PATH_SIZE_MAX);
+ prefix = new(char, pl + 1);
+ if (!prefix)
+ return -ENOMEM;
+
OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
r = interfaces_added_append_one_prefix(bus, m, prefix, path, interface, true);
if (r != 0)