Backport a patch from upstream [1] to fix CVE-2022-42012 dbus-marshal-byteswap: Byte-swap Unix fd indexes if needed
[1] https://gitlab.freedesktop.org/dbus/dbus/-/commit/3fb065b0752db1e298e4ada52cf4adc414f5e946 Signed-off-by: Xiangyu Chen <[email protected]> --- ...eswap-Byte-swap-Unix-fd-indexes-if-n.patch | 76 +++++++++++++++++++ meta/recipes-core/dbus/dbus_1.14.0.bb | 1 + 2 files changed, 77 insertions(+) create mode 100644 meta/recipes-core/dbus/dbus/0001-dbus-marshal-byteswap-Byte-swap-Unix-fd-indexes-if-n.patch diff --git a/meta/recipes-core/dbus/dbus/0001-dbus-marshal-byteswap-Byte-swap-Unix-fd-indexes-if-n.patch b/meta/recipes-core/dbus/dbus/0001-dbus-marshal-byteswap-Byte-swap-Unix-fd-indexes-if-n.patch new file mode 100644 index 0000000000..47f4f1e0d3 --- /dev/null +++ b/meta/recipes-core/dbus/dbus/0001-dbus-marshal-byteswap-Byte-swap-Unix-fd-indexes-if-n.patch @@ -0,0 +1,76 @@ +From 3fb065b0752db1e298e4ada52cf4adc414f5e946 Mon Sep 17 00:00:00 2001 +From: Simon McVittie <[email protected]> +Date: Fri, 30 Sep 2022 13:46:31 +0100 +Subject: [PATCH] dbus-marshal-byteswap: Byte-swap Unix fd indexes if needed + +When a D-Bus message includes attached file descriptors, the body of the +message contains unsigned 32-bit indexes pointing into an out-of-band +array of file descriptors. Some D-Bus APIs like GLib's GDBus refer to +these indexes as "handles" for the associated fds (not to be confused +with a Windows HANDLE, which is a kernel object). + +The assertion message removed by this commit is arguably correct up to +a point: fd-passing is only reasonable on a local machine, and no known +operating system allows processes of differing endianness even on a +multi-endian ARM or PowerPC CPU, so it makes little sense for the sender +to specify a byte-order that differs from the byte-order of the recipient. + +However, this doesn't account for the fact that a malicious sender +doesn't have to restrict itself to only doing things that make sense. +On a system with untrusted local users, a message sender could crash +the system dbus-daemon (a denial of service) by sending a message in +the opposite endianness that contains handles to file descriptors. + +Before this commit, if assertions are enabled, attempting to byteswap +a fd index would cleanly crash the message recipient with an assertion +failure. If assertions are disabled, attempting to byteswap a fd index +would silently do nothing without advancing the pointer p, causing the +message's type and the pointer into its contents to go out of sync, which +can result in a subsequent crash (the crash demonstrated by fuzzing was +a use-after-free, but other failure modes might be possible). + +In principle we could resolve this by rejecting wrong-endianness messages +from a local sender, but it's actually simpler and less code to treat +wrong-endianness messages as valid and byteswap them. + +Thanks: Evgeny Vereshchagin +Fixes: ba7daa60 "unix-fd: add basic marshalling code for unix fds" +Resolves: https://gitlab.freedesktop.org/dbus/dbus/-/issues/417 +Resolves: CVE-2022-42012 + +Upstream-Status: Backport from [https://gitlab.freedesktop.org/dbus/dbus/-/commit/3fb065b0752db1e298e4ada52cf4adc414f5e946] + +Signed-off-by: Simon McVittie <[email protected]> +(cherry picked from commit 236f16e444e88a984cf12b09225e0f8efa6c5b44) +Signed-off-by: Xiangyu Chen <[email protected]> +--- + dbus/dbus-marshal-byteswap.c | 6 +----- + 1 file changed, 1 insertion(+), 5 deletions(-) + +diff --git a/dbus/dbus-marshal-byteswap.c b/dbus/dbus-marshal-byteswap.c +index 27695aaf..7104e9c6 100644 +--- a/dbus/dbus-marshal-byteswap.c ++++ b/dbus/dbus-marshal-byteswap.c +@@ -61,6 +61,7 @@ byteswap_body_helper (DBusTypeReader *reader, + case DBUS_TYPE_BOOLEAN: + case DBUS_TYPE_INT32: + case DBUS_TYPE_UINT32: ++ case DBUS_TYPE_UNIX_FD: + { + p = _DBUS_ALIGN_ADDRESS (p, 4); + *((dbus_uint32_t*)p) = DBUS_UINT32_SWAP_LE_BE (*((dbus_uint32_t*)p)); +@@ -188,11 +189,6 @@ byteswap_body_helper (DBusTypeReader *reader, + } + break; + +- case DBUS_TYPE_UNIX_FD: +- /* fds can only be passed on a local machine, so byte order must always match */ +- _dbus_assert_not_reached("attempted to byteswap unix fds which makes no sense"); +- break; +- + default: + _dbus_assert_not_reached ("invalid typecode in supposedly-validated signature"); + break; +-- +2.34.1 + diff --git a/meta/recipes-core/dbus/dbus_1.14.0.bb b/meta/recipes-core/dbus/dbus_1.14.0.bb index e1efa9e058..484629e987 100644 --- a/meta/recipes-core/dbus/dbus_1.14.0.bb +++ b/meta/recipes-core/dbus/dbus_1.14.0.bb @@ -15,6 +15,7 @@ SRC_URI = "https://dbus.freedesktop.org/releases/dbus/dbus-${PV}.tar.xz \ file://dbus-1.init \ file://0001-dbus-marshal-validate-Check-brackets-in-signature-ne.patch \ file://0001-dbus-marshal-validate-Validate-length-of-arrays-of-f.patch \ + file://0001-dbus-marshal-byteswap-Byte-swap-Unix-fd-indexes-if-n.patch \ " SRC_URI[sha256sum] = "ccd7cce37596e0a19558fd6648d1272ab43f011d80c8635aea8fd0bad58aebd4" -- 2.34.1
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