Landlock ABI 4 restricts bind(2) and connect(2) on TCP port numbers. The intent is to bring the man pages mostly in line with the kernel documentation again. I intentionally did not add networking support to the usage example in landlock.7 - I feel that in the long run, we would be better advised to maintain longer example code in the kernel samples. Closes: https://github.com/landlock-lsm/linux/issues/32 Cc: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx> Reviewed-by: Mickaël Salaün <mic@xxxxxxxxxxx> Signed-off-by: Günther Noack <gnoack@xxxxxxxxxx> --- man/man2/landlock_add_rule.2 | 74 ++++++++++++++++++++++++++---- man/man2/landlock_create_ruleset.2 | 12 ++++- man/man7/landlock.7 | 23 ++++++++-- 3 files changed, 94 insertions(+), 15 deletions(-) diff --git a/man/man2/landlock_add_rule.2 b/man/man2/landlock_add_rule.2 index 530b45947..a0ab13419 100644 --- a/man/man2/landlock_add_rule.2 +++ b/man/man2/landlock_add_rule.2 @@ -20,15 +20,14 @@ Standard C library .BI " const void *" rule_attr ", uint32_t " flags ); .fi .SH DESCRIPTION -A Landlock rule describes an action on an object. -An object is currently a file hierarchy, -and the related filesystem actions -are defined with a set of access rights. -This +A Landlock rule describes an action on an object +which the process intends to perform. +A set of rules is aggregated in a ruleset, +which can then restrict the thread enforcing it, and its future children. +.P +The .BR landlock_add_rule () -system call enables adding a new Landlock rule to an existing ruleset -created with -.BR landlock_create_ruleset (2). +system call adds a new Landlock rule to an existing ruleset. See .BR landlock (7) for a global overview. @@ -42,10 +41,15 @@ identifies the structure type pointed to by .IR rule_attr . Currently, Linux supports the following .I rule_type -value: +values: .TP .B LANDLOCK_RULE_PATH_BENEATH -This defines the object type as a file hierarchy. +For these rules, +the object is a file hierarchy, +and the related filesystem actions +are defined with +.IR "filesystem access rights" . +.IP In this case, .I rule_attr points to the following structure: @@ -74,6 +78,45 @@ is an opened file descriptor, preferably with the flag, which identifies the parent directory of the file hierarchy or just a file. +.TP +.B LANDLOCK_RULE_NET_PORT +For these rules, +the object is a TCP port, +and the related actions are defined with +.IR "network access rights" . +.IP +In this case, +.I rule_attr +points to the following structure: +.IP +.in +4n +.EX +struct landlock_net_port_attr { + __u64 allowed_access; + __u64 port; +}; +.EE +.in +.IP +.i allowed_access +contains a bitmask of allowed network actions, +which can be applied on the given port. +.IP +.i port +is the network port in host endianness. +.IP +It should be noted that port 0 passed to +.BR bind (2) +will bind to an available port from the ephemeral port range. +This can be configured in the +.I /proc/sys/net/ipv4/ip_local_port_range +sysctl (also used for IPv6). +.IP +A Landlock rule with port 0 +and the +.B LANDLOCK_ACCESS_NET_BIND_TCP +right means that requesting to bind on port 0 is allowed +and it will automatically translate to binding on the related port range. .P .I flags must be 0. @@ -89,6 +132,12 @@ is set to indicate the error. .BR landlock_add_rule () can fail for the following reasons: .TP +.B EAFNOSUPPORT +.I rule_type +is +.BR LANDLOCK_RULE_NET_PORT , +but TCP is not supported by the running kernel. +.TP .B EOPNOTSUPP Landlock is supported by the kernel but disabled at boot time. .TP @@ -111,6 +160,11 @@ are only applicable to directories, but .I rule_attr\->parent_fd does not refer to a directory). .TP +.B EINVAL +In +.IR "struct landlock_net_port_attr" , +the port number is greater than 65535. +.TP .B ENOMSG Empty accesses (i.e., .I rule_attr\->allowed_access diff --git a/man/man2/landlock_create_ruleset.2 b/man/man2/landlock_create_ruleset.2 index 105e9b062..ca635ddbc 100644 --- a/man/man2/landlock_create_ruleset.2 +++ b/man/man2/landlock_create_ruleset.2 @@ -41,6 +41,7 @@ It points to the following structure: .EX struct landlock_ruleset_attr { __u64 handled_access_fs; + __u64 handled_access_net; }; .EE .in @@ -52,6 +53,13 @@ is a bitmask of handled filesystem actions in .BR landlock (7)). .IP +.I handled_access_net +is a bitmask of handled network actions +(see +.B Network actions +in +.BR landlock (7)). +.IP This structure defines a set of .IR "handled access rights" , a set of actions on different object types, @@ -143,8 +151,8 @@ was not a valid address. .TP .B ENOMSG Empty accesses (i.e., -.I attr\->handled_access_fs -is 0). +.I attr +did not specify any access rights to restrict). .SH STANDARDS Linux. .SH HISTORY diff --git a/man/man7/landlock.7 b/man/man7/landlock.7 index 652054f15..52876a3de 100644 --- a/man/man7/landlock.7 +++ b/man/man7/landlock.7 @@ -189,6 +189,19 @@ If multiple requirements are not met, the error code takes precedence over .BR EXDEV . .\" +.SS Network flags +These flags enable to restrict a sandboxed process +to a set of network actions. +This is supported since the Landlock ABI version 4. +.P +The following access rights apply to TCP port numbers: +.TP +.B LANDLOCK_ACCESS_NET_BIND_TCP +Bind a TCP socket to a local port. +.TP +.B LANDLOCK_ACCESS_NET_CONNECT_TCP +Connect an active TCP socket to a remote port. +.\" .SS Layers of file path access rights Each time a thread enforces a ruleset on itself, it updates its Landlock domain with a new layer of policy. @@ -339,6 +352,9 @@ _ _ _ 2 5.19 LANDLOCK_ACCESS_FS_REFER _ _ _ 3 6.2 LANDLOCK_ACCESS_FS_TRUNCATE +_ _ _ +4 6.7 LANDLOCK_ACCESS_NET_BIND_TCP +\^ \^ LANDLOCK_ACCESS_NET_CONNECT_TCP .TE .P Users should use the Landlock ABI version rather than the kernel version @@ -439,9 +455,10 @@ and only use the available subset of access rights: * numbers hardcoded to keep the example short. */ __u64 landlock_fs_access_rights[] = { - (LANDLOCK_ACCESS_FS_MAKE_SYM << 1) \- 1, /* v1 */ - (LANDLOCK_ACCESS_FS_REFER << 1) \- 1, /* v2: add "refer" */ - (LANDLOCK_ACCESS_FS_TRUNCATE << 1) \- 1, /* v3: add "truncate" */ + (LANDLOCK_ACCESS_FS_MAKE_SYM << 1) \- 1, /* v1 */ + (LANDLOCK_ACCESS_FS_REFER << 1) \- 1, /* v2: add "refer" */ + (LANDLOCK_ACCESS_FS_TRUNCATE << 1) \- 1, /* v3: add "truncate" */ + (LANDLOCK_ACCESS_FS_TRUNCATE << 1) \- 1, /* v4: TCP support */ }; \& int abi = landlock_create_ruleset(NULL, 0, -- 2.45.2.1089.g2a221341d9-goog
