From f3b8788cde61b02f1e6c202f8fac4360e6adbafc Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Tue, 12 Sep 2023 13:56:46 -0700 Subject: LSM: Identify modules by more than name 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 Signed-off-by: Casey Schaufler Reviewed-by: Kees Cook Reviewed-by: Serge Hallyn Reviewed-by: Mickael Salaun Reviewed-by: John Johansen Signed-off-by: Kees Cook Nacked-by: Tetsuo Handa [PM: forward ported beyond v6.6 due merge window changes] Signed-off-by: Paul Moore --- Documentation/userspace-api/index.rst | 1 + 1 file changed, 1 insertion(+) (limited to 'Documentation/userspace-api') diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst index 031df47a7c19..8be8b1979194 100644 --- a/Documentation/userspace-api/index.rst +++ b/Documentation/userspace-api/index.rst @@ -33,6 +33,7 @@ place where this information is gathered. sysfs-platform_profile vduse futex2 + lsm .. only:: subproject and html -- cgit v1.2.3 From a04a1198088a1378d0389c250cc684f649bcc91e Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Tue, 12 Sep 2023 13:56:49 -0700 Subject: LSM: syscalls for current process attributes Create a system call lsm_get_self_attr() to provide the security module maintained attributes of the current process. Create a system call lsm_set_self_attr() to set a security module maintained attribute of the current process. Historically these attributes have been exposed to user space via entries in procfs under /proc/self/attr. The attribute value is provided in a lsm_ctx structure. The structure identifies the size of the attribute, and the attribute value. The format of the attribute value is defined by the security module. A flags field is included for LSM specific information. It is currently unused and must be 0. The total size of the data, including the lsm_ctx structure and any padding, is maintained as well. struct lsm_ctx { __u64 id; __u64 flags; __u64 len; __u64 ctx_len; __u8 ctx[]; }; Two new LSM hooks are used to interface with the LSMs. security_getselfattr() collects the lsm_ctx values from the LSMs that support the hook, accounting for space requirements. security_setselfattr() identifies which LSM the attribute is intended for and passes it along. Signed-off-by: Casey Schaufler Reviewed-by: Kees Cook Reviewed-by: Serge Hallyn Reviewed-by: John Johansen Signed-off-by: Paul Moore --- Documentation/userspace-api/lsm.rst | 70 +++++++++++++++++++++++++++++++++++++ 1 file changed, 70 insertions(+) create mode 100644 Documentation/userspace-api/lsm.rst (limited to 'Documentation/userspace-api') diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst new file mode 100644 index 000000000000..f8499f3e2826 --- /dev/null +++ b/Documentation/userspace-api/lsm.rst @@ -0,0 +1,70 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. Copyright (C) 2022 Casey Schaufler +.. Copyright (C) 2022 Intel Corporation + +===================================== +Linux Security Modules +===================================== + +:Author: Casey Schaufler +:Date: July 2023 + +Linux security modules (LSM) provide a mechanism to implement +additional access controls to the Linux security policies. + +The various security modules may support any of these attributes: + +``LSM_ATTR_CURRENT`` is the current, active security context of the +process. +The proc filesystem provides this value in ``/proc/self/attr/current``. +This is supported by the SELinux, Smack and AppArmor security modules. +Smack also provides this value in ``/proc/self/attr/smack/current``. +AppArmor also provides this value in ``/proc/self/attr/apparmor/current``. + +``LSM_ATTR_EXEC`` is the security context of the process at the time the +current image was executed. +The proc filesystem provides this value in ``/proc/self/attr/exec``. +This is supported by the SELinux and AppArmor security modules. +AppArmor also provides this value in ``/proc/self/attr/apparmor/exec``. + +``LSM_ATTR_FSCREATE`` is the security context of the process used when +creating file system objects. +The proc filesystem provides this value in ``/proc/self/attr/fscreate``. +This is supported by the SELinux security module. + +``LSM_ATTR_KEYCREATE`` is the security context of the process used when +creating key objects. +The proc filesystem provides this value in ``/proc/self/attr/keycreate``. +This is supported by the SELinux security module. + +``LSM_ATTR_PREV`` is the security context of the process at the time the +current security context was set. +The proc filesystem provides this value in ``/proc/self/attr/prev``. +This is supported by the SELinux and AppArmor security modules. +AppArmor also provides this value in ``/proc/self/attr/apparmor/prev``. + +``LSM_ATTR_SOCKCREATE`` is the security context of the process used when +creating socket objects. +The proc filesystem provides this value in ``/proc/self/attr/sockcreate``. +This is supported by the SELinux security module. + +Kernel interface +================ + +Set a security attribute of the current process +----------------------------------------------- + +.. kernel-doc:: security/lsm_syscalls.c + :identifiers: sys_lsm_set_self_attr + +Get the specified security attributes of the current process +------------------------------------------------------------ + +.. kernel-doc:: security/lsm_syscalls.c + :identifiers: sys_lsm_get_self_attr + +Additional documentation +======================== + +* Documentation/security/lsm.rst +* Documentation/security/lsm-development.rst -- cgit v1.2.3 From ad4aff9ec25f400608283c10d634cc4eeda83a02 Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Tue, 12 Sep 2023 13:56:50 -0700 Subject: LSM: Create lsm_list_modules system call MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Create a system call to report the list of Linux Security Modules that are active on the system. The list is provided as an array of LSM ID numbers. The calling application can use this list determine what LSM specific actions it might take. That might include choosing an output format, determining required privilege or bypassing security module specific behavior. Signed-off-by: Casey Schaufler Reviewed-by: Kees Cook Reviewed-by: Serge Hallyn Reviewed-by: John Johansen Reviewed-by: Mickaël Salaün Signed-off-by: Paul Moore --- Documentation/userspace-api/lsm.rst | 3 +++ 1 file changed, 3 insertions(+) (limited to 'Documentation/userspace-api') diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst index f8499f3e2826..a76da373841b 100644 --- a/Documentation/userspace-api/lsm.rst +++ b/Documentation/userspace-api/lsm.rst @@ -63,6 +63,9 @@ Get the specified security attributes of the current process .. kernel-doc:: security/lsm_syscalls.c :identifiers: sys_lsm_get_self_attr +.. kernel-doc:: security/lsm_syscalls.c + :identifiers: sys_lsm_list_modules + Additional documentation ======================== -- cgit v1.2.3