diff options
Diffstat (limited to 'Documentation/security')
| -rw-r--r-- | Documentation/security/credentials.rst | 7 | ||||
| -rw-r--r-- | Documentation/security/landlock.rst | 27 | ||||
| -rw-r--r-- | Documentation/security/self-protection.rst | 2 | ||||
| -rw-r--r-- | Documentation/security/tpm/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/security/tpm/tpm_ffa_crb.rst | 65 |
5 files changed, 87 insertions, 15 deletions
diff --git a/Documentation/security/credentials.rst b/Documentation/security/credentials.rst index 357328d566c8..d0191c8b8060 100644 --- a/Documentation/security/credentials.rst +++ b/Documentation/security/credentials.rst @@ -527,11 +527,6 @@ There are some functions to help manage credentials: This gets a reference on a live set of credentials, returning a pointer to that set of credentials. - - ``struct cred *get_new_cred(struct cred *cred);`` - - This gets a reference on a set of credentials that is under construction - and is thus still mutable, returning a pointer to that set of credentials. - Open File Credentials ===================== @@ -560,5 +555,5 @@ the VFS, and that can be done by calling into such as ``vfs_mkdir()`` with a different set of credentials. This is done in the following places: * ``sys_faccessat()``. - * ``do_coredump()``. + * ``vfs_coredump()``. * nfs4recover.c. diff --git a/Documentation/security/landlock.rst b/Documentation/security/landlock.rst index 36f26501fd15..e0fc54aff09e 100644 --- a/Documentation/security/landlock.rst +++ b/Documentation/security/landlock.rst @@ -7,22 +7,22 @@ Landlock LSM: kernel documentation ================================== :Author: Mickaël Salaün -:Date: December 2022 +:Date: March 2025 Landlock's goal is to create scoped access-control (i.e. sandboxing). To harden a whole system, this feature should be available to any process, -including unprivileged ones. Because such process may be compromised or +including unprivileged ones. Because such a process may be compromised or backdoored (i.e. untrusted), Landlock's features must be safe to use from the kernel and other processes point of view. Landlock's interface must therefore expose a minimal attack surface. Landlock is designed to be usable by unprivileged processes while following the system security policy enforced by other access control mechanisms (e.g. DAC, -LSM). Indeed, a Landlock rule shall not interfere with other access-controls -enforced on the system, only add more restrictions. +LSM). A Landlock rule shall not interfere with other access-controls enforced +on the system, only add more restrictions. Any user can enforce Landlock rulesets on their processes. They are merged and -evaluated according to the inherited ones in a way that ensures that only more +evaluated against inherited rulesets in a way that ensures that only more constraints can be added. User space documentation can be found here: @@ -43,8 +43,12 @@ Guiding principles for safe access controls only impact the processes requesting them. * Resources (e.g. file descriptors) directly obtained from the kernel by a sandboxed process shall retain their scoped accesses (at the time of resource - acquisition) whatever process use them. + acquisition) whatever process uses them. Cf. `File descriptor access rights`_. +* Access denials shall be logged according to system and Landlock domain + configurations. Log entries must contain information about the cause of the + denial and the owner of the related security policy. Such log generation + should have a negligible performance and memory impact on allowed requests. Design choices ============== @@ -71,7 +75,7 @@ the same results, when they are executed under the same Landlock domain. Taking the ``LANDLOCK_ACCESS_FS_TRUNCATE`` right as an example, it may be allowed to open a file for writing without being allowed to :manpage:`ftruncate` the resulting file descriptor if the related file -hierarchy doesn't grant such access right. The following sequences of +hierarchy doesn't grant that access right. The following sequences of operations have the same semantic and should then have the same result: * ``truncate(path);`` @@ -81,7 +85,7 @@ Similarly to file access modes (e.g. ``O_RDWR``), Landlock access rights attached to file descriptors are retained even if they are passed between processes (e.g. through a Unix domain socket). Such access rights will then be enforced even if the receiving process is not sandboxed by Landlock. Indeed, -this is required to keep a consistent access control over the whole system, and +this is required to keep access controls consistent over the whole system, and this avoids unattended bypasses through file descriptor passing (i.e. confused deputy attack). @@ -124,6 +128,13 @@ makes the reasoning much easier and helps avoid pitfalls. .. kernel-doc:: security/landlock/ruleset.h :identifiers: +Additional documentation +======================== + +* Documentation/userspace-api/landlock.rst +* Documentation/admin-guide/LSM/landlock.rst +* https://landlock.io + .. Links .. _tools/testing/selftests/landlock/: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/tools/testing/selftests/landlock/ diff --git a/Documentation/security/self-protection.rst b/Documentation/security/self-protection.rst index 910668e665cb..a32ca23c21b0 100644 --- a/Documentation/security/self-protection.rst +++ b/Documentation/security/self-protection.rst @@ -303,7 +303,7 @@ Memory poisoning When releasing memory, it is best to poison the contents, to avoid reuse attacks that rely on the old contents of memory. E.g., clear stack on a -syscall return (``CONFIG_GCC_PLUGIN_STACKLEAK``), wipe heap memory on a +syscall return (``CONFIG_KSTACK_ERASE``), wipe heap memory on a free. This frustrates many uninitialized variable attacks, stack content exposures, heap content exposures, and use-after-free attacks. diff --git a/Documentation/security/tpm/index.rst b/Documentation/security/tpm/index.rst index fa593d960040..deda952eacbe 100644 --- a/Documentation/security/tpm/index.rst +++ b/Documentation/security/tpm/index.rst @@ -10,3 +10,4 @@ Trusted Platform Module documentation tpm_vtpm_proxy xen-tpmfront tpm_ftpm_tee + tpm_ffa_crb diff --git a/Documentation/security/tpm/tpm_ffa_crb.rst b/Documentation/security/tpm/tpm_ffa_crb.rst new file mode 100644 index 000000000000..0184193da3c7 --- /dev/null +++ b/Documentation/security/tpm/tpm_ffa_crb.rst @@ -0,0 +1,65 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================== +TPM CRB over FF-A Driver +======================== + +The TPM Command Response Buffer (CRB) interface is a standard TPM interface +defined in the TCG PC Client Platform TPM Profile (PTP) Specification [1]_. +The CRB provides a structured set of control registers a client uses when +interacting with a TPM as well as a data buffer for storing TPM commands and +responses. A CRB interface can be implemented in: + +- hardware registers in a discrete TPM chip + +- in memory for a TPM running in isolated environment where shared memory + allows a client to interact with the TPM + +The Firmware Framework for Arm A-profile (FF-A) [2]_ is a specification +that defines interfaces and protocols for the following purposes: + +- Compartmentalize firmware into software partitions that run in the Arm + Secure world environment (also know as TrustZone) + +- Provide a standard interface for software components in the Non-secure + state, for example OS and Hypervisors, to communicate with this firmware. + +A TPM can be implemented as an FF-A secure service. This could be a firmware +TPM or could potentially be a TPM service that acts as a proxy to a discrete +TPM chip. An FF-A based TPM abstracts hardware details (e.g. bus controller +and chip selects) away from the OS and can protect locality 4 from access +by an OS. The TCG-defined CRB interface is used by clients to interact +with the TPM service. + +The Arm TPM Service Command Response Buffer Interface Over FF-A [3]_ +specification defines FF-A messages that can be used by a client to signal +when updates have been made to the CRB. + +How the Linux CRB driver interacts with FF-A is summarized below: + +- The tpm_crb_ffa driver registers with the FF-A subsystem in the kernel + with an architected TPM service UUID defined in the CRB over FF-A spec. + +- If a TPM service is discovered by FF-A, the probe() function in the + tpm_crb_ffa driver runs, and the driver initializes. + +- The probing and initialization of the Linux CRB driver is triggered + by the discovery of a TPM advertised via ACPI. The CRB driver can + detect the type of TPM through the ACPI 'start' method. The start + method for Arm FF-A was defined in TCG ACPI v1.4 [4]_. + +- When the CRB driver performs its normal functions such as signaling 'start' + and locality request/relinquish it invokes the tpm_crb_ffa_start() funnction + in the tpm_crb_ffa driver which handles the FF-A messaging to the TPM. + +References +========== + +.. [1] **TCG PC Client Platform TPM Profile (PTP) Specification** + https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/ +.. [2] **Arm Firmware Framework for Arm A-profile (FF-A)** + https://developer.arm.com/documentation/den0077/latest/ +.. [3] **Arm TPM Service Command Response Buffer Interface Over FF-A** + https://developer.arm.com/documentation/den0138/latest/ +.. [4] **TCG ACPI Specification** + https://trustedcomputinggroup.org/resource/tcg-acpi-specification/ |