systemd: fix CVE-2019-6454

Apply patches from systemd_237-3ubuntu10.13 to fix CVE-2019-6454.
CVE-2019-6454 is an issue in which systemd (PID1) can be crashed
with a specially formed D-Bus message.

For information see:
https://usn.ubuntu.com/3891-1/
https://git.launchpad.net/ubuntu/+source/systemd/commit/?h=applied/ubuntu/bionic-updates&id=d7584b894afcaa8a4a1abb69db2a9c81a6276e80

(From OE-Core rev: 342157b135e7493e5965b706ede93bee190fbe32)

Signed-off-by: George McCollister <george.mccollister@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

3 files changed, 273 insertions, 0 deletions

diff --git a/meta/recipes-core/systemd/systemd/CVE-2019-6454.patch b/meta/recipes-core/systemd/systemd/CVE-2019-6454.patch
new file mode 100644
index 0000000000..e3c67c166c
--- /dev/null
+++ b/meta/recipes-core/systemd/systemd/CVE-2019-6454.patch
@@ -0,0 +1,210 @@
+Description: sd-bus: enforce a size limit for dbus paths, and don't allocate
+ them on the stacka
+Forwarded: no
+
+Patch from: systemd_237-3ubuntu10.13
+
+For information see:
+https://usn.ubuntu.com/3891-1/
+https://git.launchpad.net/ubuntu/+source/systemd/commit/?h=applied/ubuntu/bionic-updates&id=d7584b894afcaa8a4a1abb69db2a9c81a6276e80
+
+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
+@@ -61,7 +61,7 @@
+         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
+@@ -339,6 +339,10 @@
+ 
+ #define BUS_MESSAGE_SIZE_MAX (64*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
+@@ -1150,7 +1150,8 @@
+                 const char *path,
+                 sd_bus_error *error) {
+ 
+-        char *prefix;
++        _cleanup_free_ char *prefix = NULL;
++        size_t pl;
+         int r;
+ 
+         assert(bus);
+@@ -1166,7 +1167,12 @@
+                 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)
+@@ -1362,6 +1368,7 @@
+ }
+ 
+ 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;
+@@ -1386,9 +1393,12 @@
+         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);
+@@ -1516,9 +1526,15 @@
+ 
+         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)
+@@ -2108,8 +2124,9 @@
+                 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);
+@@ -2128,6 +2145,12 @@
+         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;
+ 
+@@ -2137,7 +2160,6 @@
+                 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)
+@@ -2269,7 +2291,8 @@
+ 
+ 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);
+@@ -2314,7 +2337,12 @@
+         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)
+@@ -2453,7 +2481,8 @@
+ 
+ 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);
+@@ -2485,7 +2514,12 @@
+         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)
+@@ -2635,7 +2669,8 @@
+                 const char *path,
+                 const char *interface) {
+ 
+-        char *prefix;
++        _cleanup_free_ char *prefix = NULL;
++        size_t pl;
+         int r;
+ 
+         assert(bus);
+@@ -2649,7 +2684,12 @@
+         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)
diff --git a/meta/recipes-core/systemd/systemd/sd-bus-if-we-receive-an-invalid-dbus-message-ignore-.patch b/meta/recipes-core/systemd/systemd/sd-bus-if-we-receive-an-invalid-dbus-message-ignore-.patch
new file mode 100644
index 0000000000..4ffa739145
--- /dev/null
+++ b/meta/recipes-core/systemd/systemd/sd-bus-if-we-receive-an-invalid-dbus-message-ignore-.patch
@@ -0,0 +1,61 @@
+Description: sd-bus: if we receive an invalid dbus message, ignore and
+ proceeed
+ .
+ dbus-daemon might have a slightly different idea of what a valid msg is
+ than us (for example regarding valid msg and field sizes). Let's hence
+ try to proceed if we can and thus drop messages rather than fail the
+ connection if we fail to validate a message.
+ .
+ Hopefully the differences in what is considered valid are not visible
+ for real-life usecases, but are specific to exploit attempts only.
+Author: Lennart Poettering <lennart@poettering.net>
+Forwarded: other,https://github.com/systemd/systemd/pull/11708/
+
+Patch from: systemd_237-3ubuntu10.13
+
+For information see:
+https://usn.ubuntu.com/3891-1/
+https://git.launchpad.net/ubuntu/+source/systemd/commit/?h=applied/ubuntu/bionic-updates&id=d7584b894afcaa8a4a1abb69db2a9c81a6276e80
+
+CVE: CVE-2019-6454
+Upstream-Status: Backport
+
+Signed-off-by: George McCollister <george.mccollister@gmail.com>
+
+diff --git a/src/libsystemd/sd-bus/bus-socket.c b/src/libsystemd/sd-bus/bus-socket.c
+index 30d6455b6f..441b4a816f 100644
+--- a/src/libsystemd/sd-bus/bus-socket.c
++++ b/src/libsystemd/sd-bus/bus-socket.c
+@@ -1072,7 +1072,7 @@ static int bus_socket_read_message_need(sd_bus *bus, size_t *need) {
+ }
+
+ static int bus_socket_make_message(sd_bus *bus, size_t size) {
+-        sd_bus_message *t;
++        sd_bus_message *t = NULL;
+         void *b;
+         int r;
+
+@@ -1097,7 +1097,9 @@ static int bus_socket_make_message(sd_bus *bus, size_t size) {
+                                     bus->fds, bus->n_fds,
+                                     NULL,
+                                     &t);
+-        if (r < 0) {
++        if (r == -EBADMSG)
++                log_debug_errno(r, "Received invalid message from connection %s, dropping.", strna(bus->description));
++        else if (r < 0) {
+                 free(b);
+                 return r;
+         }
+@@ -1108,7 +1110,8 @@ static int bus_socket_make_message(sd_bus *bus, size_t size) {
+         bus->fds = NULL;
+         bus->n_fds = 0;
+
+-        bus->rqueue[bus->rqueue_size++] = t;
++        if (t)
++                bus->rqueue[bus->rqueue_size++] = t;
+
+         return 1;
+ }
+--
+2.17.1
+
diff --git a/meta/recipes-core/systemd/systemd_237.bb b/meta/recipes-core/systemd/systemd_237.bb
index bc33fbebdc..a0e5d512e0 100644
--- a/meta/recipes-core/systemd/systemd_237.bb
+++ b/meta/recipes-core/systemd/systemd_237.bb
@@ -63,6 +63,8 @@ SRC_URI += "file://touchscreen.rules \
            file://0027-journal-fix-out-of-bounds-read-CVE-2018-16866.patch \
            file://0001-tmpfiles-don-t-resolve-pathnames-when-traversing-rec.patch \
            file://0002-Make-tmpfiles-safe.patch \
+           file://CVE-2019-6454.patch \
+           file://sd-bus-if-we-receive-an-invalid-dbus-message-ignore-.patch \
            "
 SRC_URI_append_qemuall = " file://0001-core-device.c-Change-the-default-device-timeout-to-2.patch"