The documentation of the socket_connect() LSM hook states that it
controls connecting a socket to a remote address. It has not been the
case since the addition of TCP Fast Open (RFC 7413) support, which
allows opening a TCP connection (thus, setting a socket's destination
address) via the MSG_FASTOPEN flag passed to
sendto()/sendmsg()/sendmmsg(). The problem then got duplicated into
MPTCP.
Landlock did not take it into account when its TCP support was added,
leaving a bypass of TCP connect policy.
Ideally a call to the LSM hook would be added in the fastopen code path,
in order to fix this generically. But connect() hooks are designed to
run with the socket locked, unlike sendmsg() hooks.
Closes: https://github.com/landlock-lsm/linux/issues/41
Fixes: fff69fb03d ("landlock: Support network rules with TCP bind and connect")
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
Link: https://patch.msgid.link/20260701214628.33319-1-matthieu@buffet.re
Cc: stable@vger.kernel.org
[mic: Wrap commit message]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Adds the UAPI for the quiet flags feature (but not the implementation
yet).
Even though currently LANDLOCK_ADD_RULE_QUIET only affects audit
logging, in the future this can also be used as part of a supervisor
mechanism, where it will also suppress denial notifications on a
per-object basis. Thus the name is deliberately generic, as opposed to
e.g. LANDLOCK_ADD_RULE_LOG_QUIET.
According to pahole, even after adding the struct access_masks
quiet_masks in struct landlock_hierarchy, the u32 log_* bitfield still
only has a size of 2 bytes, so there's minimal wasted space.
Assisted-by: GitHub-Copilot:claude-opus-4.8
Signed-off-by: Tingmao Wang <m@maowtm.org>
[mic: Update date, fix comment formatting]
Link: https://patch.msgid.link/031184748a8e74c0bb02f1fa13d7a3f10918c627.1781228815.git.m@maowtm.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
To avoid unnecessarily increasing the size of struct landlock_layer, we
make the layer level a u8 and use the space to store the flags struct.
struct layer_access_masks is renamed to struct layer_masks, and a new
field is added to track whether a quiet flag rule is seen for each
layer. Through use of bitfields, this does not increase the size of the
struct.
Cc: Justin Suess <utilityemal77@gmail.com>
Assisted-by: GitHub-Copilot:claude-opus-4.8 copilot-review
Signed-off-by: Tingmao Wang <m@maowtm.org>
Co-developed-by: Justin Suess <utilityemal77@gmail.com>
Signed-off-by: Justin Suess <utilityemal77@gmail.com>
Tested-by: Justin Suess <utilityemal77@gmail.com>
Link: https://patch.msgid.link/be3fec3927bc9faaacd4ce0e7f0d1ff5474e2210.1781228815.git.m@maowtm.org
[mic: Fix comment formatting]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Add support for a second fine-grained UDP access right.
LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP controls the ability to set the
remote port of a socket (via connect()) and to specify an explicit
destination when sending a datagram, to override any remote peer set on
a UDP socket (e.g. in sendto() or sendmsg()). It will be useful for
applications that send datagrams, and for some servers too (those
creating per-client sockets, which want to receive traffic only from a
specific address).
Similarly as for bind(), this access control is performed when
configuring sockets, not in hot code paths.
Add detection of when autobind is about to be required, and deny the
operation if the process would not be allowed to call bind(0)
explicitly. Autobind can only be performed in udp_lib_get_port() from
code paths already controlled by LSM hooks: when connect()ing, sending a
first datagram, and in some splice() EOF edge case which, afaiu, can
only happen after a remote peer has been set. This invariant needs to be
preserved to keep bind policies actually enforced.
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
Link: https://patch.msgid.link/20260611162107.49278-3-matthieu@buffet.re
[mic: Add quick return for non-sandboxed tasks, fix sa_family
dereferencing, fix comment formatting]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Add support for a first fine-grained UDP access right.
LANDLOCK_ACCESS_NET_BIND_UDP controls the ability to set the local port
of a UDP socket (via bind()). It will be useful for servers (to start
receiving datagrams), and for some clients that need to use a specific
source port (e.g. mDNS requires to use port 5353)
For obvious performance concerns, access control is only enforced when
configuring sockets, not when using them for common send/recv
operations.
Bump ABI to allow userspace to detect and use this new right.
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
Link: https://patch.msgid.link/20260611162107.49278-2-matthieu@buffet.re
[mic: Fix comment formatting]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Socket family is read (twice) in a context where the socket is not
locked, so another thread can setsockopt(IPV6_ADDRFORM) to write it
concurrently. Add needed READ_ONCE() annotation.
Use the proper macro to access __sk_common.skc_family like everywhere
else.
Fixes: fff69fb03d ("landlock: Support network rules with TCP bind and connect")
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
Link: https://patch.msgid.link/20260609211511.85630-1-matthieu@buffet.re
Link: https://patch.msgid.link/20260609211511.85630-2-matthieu@buffet.re
[mic: Squash two patches, move variable to ease backport, fix comment
formatting]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Set audit_net.sk in current_check_access_socket() to provide the socket
object to audit_log_lsm_data(). This makes Landlock consistent with
AppArmor, which always sets .sk for socket operations, and with
SELinux's generic socket permission checks.
The socket's local and foreign address information (laddr, lport, faddr,
fport) is logged by the shared lsm_audit.c infrastructure when the
socket has bound or connected state. Fields with zero values are
suppressed by print_ipv4_addr()/print_ipv6_addr(), so the audit output
is unchanged for the common case of bind denials on unbound sockets.
For connect denials after a prior bind, the bound local address (laddr,
lport) appears before the existing sockaddr fields (daddr, dest).
No existing fields are removed or reordered, and the new field names
(laddr, lport, faddr, fport) are standard audit fields already emitted
by other LSMs through the same lsm_audit.c code path.
Add a connect_tcp_bound audit test that binds to an allowed port and
then connects to a denied one, verifying that the denial record reports
laddr/lport from the bound socket in addition to the connect
destination.
Cc: Günther Noack <gnoack@google.com>
Cc: Tingmao Wang <m@maowtm.org>
Cc: stable@vger.kernel.org
Fixes: 9f74411a40 ("landlock: Log TCP bind and connect denials")
Link: https://patch.msgid.link/20260612172757.1003481-1-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
The layer masks data structure tracks the requested but unfulfilled
access rights during an operation's security check. It stores one bit
for each combination of access right and layer index. If the bit is
set, that access right is not granted (yet) in the given layer and we
have to traverse the path further upwards to grant it.
Previously, the layer masks were stored as arrays mapping from access
right indices to layer_mask_t. The layer_mask_t value then indicates
all layers in which the given access right is still (tentatively)
denied.
This patch introduces struct layer_access_masks instead: This struct
contains an array with the access_mask_t of each (tentatively) denied
access right in that layer.
The hypothesis of this patch is that this simplifies the code enough
so that the resulting code will run faster:
* We can use bitwise operations in multiple places where we previously
looped over bits individually with macros. (Should require less
branch speculation and lends itself to better loop unrolling.)
* Code is ~75 lines smaller.
Other noteworthy changes:
* In no_more_access(), call a new helper function may_refer(), which
only solves the asymmetric case. Previously, the code interleaved
the checks for the two symmetric cases in RENAME_EXCHANGE. It feels
that the code is clearer when renames without RENAME_EXCHANGE are
more obviously the normal case.
Tradeoffs:
This change improves performance, at a slight size increase to the
layer masks data structure.
This fixes the size of the data structure at 32 bytes for all types of
access rights. (64, once we introduce a 17th filesystem access right).
For filesystem access rights, at the moment, the data structure has
the same size as before, but once we introduce the 17th filesystem
access right, it will double in size (from 32 to 64 bytes), as
access_mask_t grows from 16 to 32 bit [1].
Link: https://lore.kernel.org/all/20260120.haeCh4li9Vae@digikod.net/ [1]
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20260206151154.97915-5-gnoack3000@gmail.com
[mic: Cosmetic fixes, moved struct layer_access_masks definition]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Move the socket type check earlier, so that we will later be able to add
elseifs for other types. Ordering of checks (socket is of a type we
enforce restrictions on) / (current creds have Landlock restrictions)
should not change anything.
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
Link: https://lore.kernel.org/r/20251212163704.142301-3-matthieu@buffet.re
Signed-off-by: Mickaël Salaün <mic@digikod.net>
current_check_access_socket() treats AF_UNSPEC addresses as
AF_INET ones, and only later adds special case handling to
allow connect(AF_UNSPEC), and on IPv4 sockets
bind(AF_UNSPEC+INADDR_ANY).
This would be fine except AF_UNSPEC addresses can be as
short as a bare AF_UNSPEC sa_family_t field, and nothing
more. The AF_INET code path incorrectly enforces a length of
sizeof(struct sockaddr_in) instead.
Move AF_UNSPEC edge case handling up inside the switch-case,
before the address is (potentially incorrectly) treated as
AF_INET.
Fixes: fff69fb03d ("landlock: Support network rules with TCP bind and connect")
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
Link: https://lore.kernel.org/r/20251027190726.626244-4-matthieu@buffet.re
Signed-off-by: Mickaël Salaün <mic@digikod.net>
This cosmetic change that is needed for audit support, specifically to
be able to filter according to cross-execution boundaries.
Optimize current_check_access_socket() to only handle the access
request.
Remove explicit domain->num_layers check which is now part of the
landlock_get_applicable_subject() call.
Cc: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-6-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Use sk_is_tcp() to check if socket is TCP in bind(2) and connect(2)
hooks.
SMC, MPTCP, SCTP protocols are currently restricted by TCP access
rights. The purpose of TCP access rights is to provide control over
ports that can be used by userland to establish a TCP connection.
Therefore, it is incorrect to deny bind(2) and connect(2) requests for a
socket of another protocol.
However, SMC, MPTCP and RDS implementations use TCP internal sockets to
establish communication or even to exchange packets over a TCP
connection [1]. Landlock rules that configure bind(2) and connect(2)
usage for TCP sockets should not cover requests for sockets of such
protocols. These protocols have different set of security issues and
security properties, therefore, it is necessary to provide the userland
with the ability to distinguish between them (eg. [2]).
Control over TCP connection used by other protocols can be achieved with
upcoming support of socket creation control [3].
[1] https://lore.kernel.org/all/62336067-18c2-3493-d0ec-6dd6a6d3a1b5@huawei-partners.com/
[2] https://lore.kernel.org/all/20241204.fahVio7eicim@digikod.net/
[3] https://lore.kernel.org/all/20240904104824.1844082-1-ivanov.mikhail1@huawei-partners.com/
Closes: https://github.com/landlock-lsm/linux/issues/40
Fixes: fff69fb03d ("landlock: Support network rules with TCP bind and connect")
Signed-off-by: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
Link: https://lore.kernel.org/r/20250205093651.1424339-2-ivanov.mikhail1@huawei-partners.com
[mic: Format commit message to 72 columns]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Remove the handled_access variable in current_check_access_socket() and
update access_request instead. One up-to-date variable avoids picking
the wrong one.
Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20240307093923.1466071-1-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Create a struct lsm_id to contain identifying information about Linux
Security Modules (LSMs). At inception this contains the name of the
module and an identifier associated with the security module. Change
the security_add_hooks() interface to use this structure. Change the
individual modules to maintain their own struct lsm_id and pass it to
security_add_hooks().
The values are for LSM identifiers are defined in a new UAPI
header file linux/lsm.h. Each existing LSM has been updated to
include it's LSMID in the lsm_id.
The LSM ID values are sequential, with the oldest module
LSM_ID_CAPABILITY being the lowest value and the existing modules
numbered in the order they were included in the main line kernel.
This is an arbitrary convention for assigning the values, but
none better presents itself. The value 0 is defined as being invalid.
The values 1-99 are reserved for any special case uses which may
arise in the future. This may include attributes of the LSM
infrastructure itself, possibly related to namespacing or network
attribute management. A special range is identified for such attributes
to help reduce confusion for developers unfamiliar with LSMs.
LSM attribute values are defined for the attributes presented by
modules that are available today. As with the LSM IDs, The value 0
is defined as being invalid. The values 1-99 are reserved for any
special case uses which may arise in the future.
Cc: linux-security-module <linux-security-module@vger.kernel.org>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: Mickael Salaun <mic@digikod.net>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Nacked-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
[PM: forward ported beyond v6.6 due merge window changes]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Add network rules support in the ruleset management helpers and the
landlock_create_ruleset() syscall. Extend user space API to support
network actions:
* Add new network access rights: LANDLOCK_ACCESS_NET_BIND_TCP and
LANDLOCK_ACCESS_NET_CONNECT_TCP.
* Add a new network rule type: LANDLOCK_RULE_NET_PORT tied to struct
landlock_net_port_attr. The allowed_access field contains the network
access rights, and the port field contains the port value according to
the controlled protocol. This field can take up to a 64-bit value
but the maximum value depends on the related protocol (e.g. 16-bit
value for TCP). Network port is in host endianness [1].
* Add a new handled_access_net field to struct landlock_ruleset_attr
that contains network access rights.
* Increment the Landlock ABI version to 4.
Implement socket_bind() and socket_connect() LSM hooks, which enable
to control TCP socket binding and connection to specific ports.
Expand access_masks_t from u16 to u32 to be able to store network access
rights alongside filesystem access rights for rulesets' handled access
rights.
Access rights are not tied to socket file descriptors but checked at
bind() or connect() call time against the caller's Landlock domain. For
the filesystem, a file descriptor is a direct access to a file/data.
However, for network sockets, we cannot identify for which data or peer
a newly created socket will give access to. Indeed, we need to wait for
a connect or bind request to identify the use case for this socket.
Likewise a directory file descriptor may enable to open another file
(i.e. a new data item), but this opening is also restricted by the
caller's domain, not the file descriptor's access rights [2].
[1] https://lore.kernel.org/r/278ab07f-7583-a4e0-3d37-1bacd091531d@digikod.net
[2] https://lore.kernel.org/r/263c1eb3-602f-57fe-8450-3f138581bee7@digikod.net
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-9-konstantin.meskhidze@huawei.com
[mic: Extend commit message, fix typo in comments, and specify
endianness in the documentation]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
