On Mon, Jan 30, 2023 at 02:57:31PM -0800, Fan Wu wrote: > diff --git a/Documentation/admin-guide/LSM/ipe.rst b/Documentation/admin-guide/LSM/ipe.rst > new file mode 100644 > index 000000000000..b676cea62b2e > --- /dev/null > +++ b/Documentation/admin-guide/LSM/ipe.rst > @@ -0,0 +1,729 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +Integrity Policy Enforcement (IPE) > +================================== > + > +.. NOTE:: > + > + This is the documentation for admins, system builders, or individuals > + attempting to use IPE. If you're looking for more developer-focused > + documentation about IPE please see `Documentation/security/ipe.rst` > + > +Overview > +-------- > + > +IPE is a Linux Security Module which takes a complimentary approach to > +access control. Whereas existing mandatory access control mechanisms > +base their decisions on labels and paths, IPE instead determines > +whether or not an operation should be allowed based on immutable > +security properties of the system component the operation is being > +performed on. > + > +IPE itself does not mandate how the security property should be > +evaluated, but relies on an extensible set of external property providers > +to evaluate the component. IPE makes its decision based on reference > +values for the selected properties, specified in the IPE policy. > + > +The reference values represent the value that the policy writer and the > +local system administrator (based on the policy signature) trust for the > +system to accomplish the desired tasks. > + > +One such provider is for example dm-verity, which is able to represent > +the integrity property of a partition (its immutable state) with a digest. > + > +IPE is compiled under ``CONFIG_SECURITY_IPE`` (Security -> Integrity Policy Enforcement (IPE)). > + > +Use Cases > +--------- > + > +IPE works best in fixed-function devices: devices in which their purpose > +is clearly defined and not supposed to be changed (e.g. network firewall > +device in a data center, an IoT device, etcetera), where all software and > +configuration is built and provisioned by the system owner. > + > +IPE is a long-way off for use in general-purpose computing: the Linux > +community as a whole tends to follow a decentralized trust model, > +known as the web of trust, which IPE has no support for as of yet. > + > +IPE, instead of supporting web of trust, supports PKI, which generally > +designates a set of entities that provide a measure of absolute trust. > + > +Additionally, while most packages are signed today, the files inside > +the packages (for instance, the executables), tend to be unsigned. This > +makes it difficult to utilize IPE in systems where a package manager is > +expected to be functional, without major changes to the package manager > +and ecosystem behind it. > + > +DIGLIM [#diglim]_ is a system that when combined with IPE, could be used to > +enable general purpose computing scenarios. > + > +Known Gaps > +---------- > + > +IPE cannot verify the integrity of anonymous executable memory, such as > +the trampolines created by gcc closures and libffi (<3.4.2), or JIT'd code. > +Unfortunately, as this is dynamically generated code, there is no way > +for IPE to ensure the integrity of this code to form a trust basis. In all > +cases, the return result for these operations will be whatever the admin > +configures as the ``DEFAULT`` action for ``EXECUTE``. > + > +IPE cannot verify the integrity of interpreted languages' programs when > +these scripts are invoked via ``<interpreter> <file>``. This is because > +the way interpreters execute these files, the scripts themselves are not > +evaluated as executable code through one of IPE's hooks, as they are merely > +files that are read (as opposed to executable code) [#interpreters]_. > + > +Threat Model > +------------ > + > +The threat type addressed by IPE is tampering of executable userspace > +code beyond the initially booted kernel, and the initial verification of > +kernel modules that are loaded in userspace through ``modprobe`` or > +``insmod``. > + > +A bare-minimum example of a threat that should be mitigated by IPE, is > +a hostile binary is downloaded with all required binaries (including > +a loader, libc, etc). With IPE, this hostile binary should not able to > +be executed, nor any of the downloaded binaries. > + > +Tampering violates integrity, and being unable to verify the integrity, > +results in a lack of trust. IPE's role in mitigating this threat is to > +verify the integrity (and authenticity) of all executable code and to > +deny their use if they cannot be trusted (as integrity verification fails, > +or the authorization check fails against the reference value in the policy). > +IPE generates audit logs which may be utilized to detect failures resulting > +from failure to pass policy. > + > +Tampering threat scenarios include modification or replacement of > +executable code by a range of actors including: > + > +- Actors with physical access to the hardware > +- Actors with local network access to the system > +- Actors with access to the deployment system > +- Compromised internal systems under external control > +- Malicious end users of the system > +- Compromised end users of the system > +- Remote (external) compromise of the system > + > +IPE does not mitigate threats arising from malicious authorized > +developers (with access to a signing certificate), or compromised > +developer tools used by authorized developers (i.e. Return Oriented > +Programming attacks). Additionally, IPE draws hard security boundary > +between userspace and kernelspace. As a result, IPE does not provide > +any protections against a kernel level exploit, and a kernel-level > +exploit can disable or tamper with IPE's protections. > + > +Policy > +------ > + > +IPE policy is a plain-text [#devdoc]_ policy composed of multiple statements > +over several lines. There is one required line, at the top of the > +policy, indicating the policy name, and the policy version, for > +instance:: > + > + policy_name=Ex_Policy policy_version=0.0.0 > + > +The policy name is a unique key identifying this policy in a human > +readable name. This is used to create nodes under securityfs as well as > +uniquely identify policies to deploy new policies vs update existing > +policies. > + > +The policy version indicates the current version of the policy (NOT the > +policy syntax version). This is used to prevent rollback of policy to > +potentially insecure previous versions of the policy. > + > +The next portion of IPE policy are rules. Rules are formed by key=value > +pairs, known as properties. IPE rules require two properties: "action", > +which determines what IPE does when it encounters a match against the > +rule, and "op", which determines when that rule should be evaluated. > +The ordering is significant, a rule must start with "op", and end with > +"action". Thus, a minimal rule is:: > + > + op=EXECUTE action=ALLOW > + > +This example will allow any execution. Additional properties are used to > +restrict attributes about the files being evaluated. These properties > +are intended to be descriptions of systems within the kernel that can > +provide a measure of integrity verification, such that IPE can determine > +the trust of the resource based on the "value" half of the property. > + > +Rules are evaluated top-to-bottom. As a result, any revocation rules, > +or denies should be placed early in the file to ensure that these rules > +are evaluated before a rule with "action=ALLOW" is hit. > + > +IPE policy supports comments. The character '#' will function as a > +comment, ignoring all characters to the right of '#' until the newline. > + > +The default behavior of IPE evaluations can also be expressed in policy, > +through the ``DEFAULT`` statement. This can be done at a global level, > +or a per-operation level:: > + > + # Global > + DEFAULT action=ALLOW > + > + # Operation Specific > + DEFAULT op=EXECUTE action=ALLOW > + > +A default must be set for all known operations in IPE. If you want to > +preserve older policies being compatible with newer kernels that can introduce > +new operations, please set a global default of 'ALLOW', and override the > +defaults on a per-operation basis. > + > +With configurable policy-based LSMs, there's several issues with > +enforcing the configurable policies at startup, around reading and > +parsing the policy: > + > +1. The kernel *should* not read files from userspace, so directly reading > + the policy file is prohibited. > +2. The kernel command line has a character limit, and one kernel module > + should not reserve the entire character limit for its own > + configuration. > +3. There are various boot loaders in the kernel ecosystem, so handing > + off a memory block would be costly to maintain. > + > +As a result, IPE has addressed this problem through a concept of a "boot > +policy". A boot policy is a minimal policy, compiled into the kernel. > +This policy is intended to get the system to a state where userspace is > +set up and ready to receive commands, at which point a more complex > +policy can be deployed via securityfs. The boot policy can be specified > +via the Kconfig, ``SECURITY_IPE_BOOT_POLICY``, which accepts a path to > +a plain-text version of the IPE policy to apply. This policy will be > +compiled into the kernel. If not specified, IPE will be disabled until > +a policy is deployed and activated through securityfs. > + > +Deploying Policies > +~~~~~~~~~~~~~~~~~~ > + > +Policies can be deployed from userspace through securityfs. These policies > +are signed through the PKCS#7 message format to enforce some level of > +authorization of the policies (prohibiting an attacker from gaining > +unconstrained root, and deploying an "allow all" policy). These > +policies must be signed by a certificate that chains to the > +``SYSTEM_TRUSTED_KEYRING``. Through openssl, the signing can be done via:: > + > + openssl smime -sign \ > + -in "$MY_POLICY" \ > + -signer "$MY_CERTIFICATE" \ > + -inkey "$MY_PRIVATE_KEY" \ > + -noattr \ > + -nodetach \ > + -nosmimecap \ > + -outform der \ > + -out "$MY_POLICY.p7b" > + > +Deploying the policies is done through securityfs, through the > +``new_policy`` node. To deploy a policy, simply cat the file into the > +securityfs node:: > + > + cat "$MY_POLICY.p7b" > /sys/kernel/security/ipe/new_policy > + > +Upon success, this will create one subdirectory under > +``/sys/kernel/security/ipe/policies/``. The subdirectory will be the > +``policy_name`` field of the policy deployed, so for the example above, > +the directory will be ``/sys/kernel/security/ipe/policies/Ex_Policy``. > +Within this directory, there will be five files: ``pkcs7``, ``policy``, > +``active``, ``update``, and ``delete``. > + > +The ``pkcs7`` file is read only. Reading will provide the raw PKCS#7 data > +that was provided to the kernel, representing the policy. Writing, will > +deploy an in-place policy update.If the policy being read is the boot > +policy, when read, this will return ENOENT, as this policy is not signed. > + > +The ``policy`` file is read only. Reading will provide the PKCS#7 inner > +content of the policy, which will be the plain text policy. > + > +The ``active`` file is used to set a policy as the currently active policy. > +This file is rw, and accepts a value of ``"1"`` to set the policy as active. > +Since only a single policy can be active at one time, all other policies > +will be marked inactive. The policy being marked active must have a policy > +version greater or equal to the currently-running version. > + > +The ``update`` file is used to update a policy that is already present in > +the kernel. This file is write-only and accepts a PKCS#7 signed policy. > +One check will always be performed on this policy: the policy_names must > +match with the updated version and the existing version. One additional check > +may be made: If the policy being updated is the active policy, the updated > +policy must have a policy version greater than or equal to the currently-running > +version; This is to prevent rollback attacks. > + > +The ``delete`` file is used to remove a policy that is no longer needed. > +This file is write-only and accepts a value of ``1`` to delete the policy. > +On deletion, the securityfs node representing the policy will be removed. > +The policy that is currently active cannot be deleted. > + > +Similarly, the writes to both ``update`` and ``new_policy`` above will > +result in an error upon syntactically invalid or untrusted policies. > +In the case of ``new_policy``, it will also error if a policy already > +exists with the same ``policy_name``. > + > +Deploying these policies will *not* cause IPE to start enforcing this > +policy. Once deployment is successful, a policy can be marked as active, > +via ``/sys/kernel/security/ipe/$policy_name/active``. IPE will enforce > +whatever policy is marked as active. For our example, we can activate > +the ``Ex_Policy`` via:: > + > + echo 1 > "/sys/kernel/security/ipe/Ex_Policy/active" > + > +At which point, ``Ex_Policy`` will now be the enforced policy on the > +system. > + > +IPE also provides a way to delete policies. This can be done via the > +``delete`` securityfs node, ``/sys/kernel/security/ipe/$policy_name/delete``. > +Writing ``1`` to that file will delete that node:: > + > + echo 1 > "/sys/kernel/security/ipe/$policy_name/delete" > + > +There is only one requirement to delete a policy: > + > +1. The policy being deleted must not be the active policy. > + > +.. NOTE:: > + > + If a traditional MAC system is enabled (SELinux, apparmor, smack), all > + writes to ipe's securityfs nodes require ``CAP_MAC_ADMIN``. > + > +Modes > +~~~~~ > + > +IPE supports two modes of operation: permissive (similar to SELinux's > +permissive mode) and enforce. Permissive mode performs the same checks > +as enforce mode, and logs policy violations, but will not enforce the > +policy. This allows users to test policies before enforcing them. > + > +The default mode is enforce, and can be changed via the kernel command > +line parameter ``ipe.enforce=(0|1)``, or the securityfs node > +``/sys/kernel/security/ipe/enforce``. > + > +.. NOTE:: > + > + If a traditional MAC system is enabled (SELinux, apparmor, smack, etcetera), > + all writes to ipe's securityfs nodes require ``CAP_MAC_ADMIN``. > + > +Audit Events > +~~~~~~~~~~~~ > + > +1420 AUDIT_IPE_ACCESS > +^^^^^^^^^^^^^^^^^^^^^ > +Event Examples:: > + > + type=1420 audit(1653364370.067:61): path="/root/fs/rw/plain/execve" dev="vdc1" ino=16 rule="DEFAULT op=EXECUTE action=DENY" > + type=1300 audit(1653364370.067:61): arch=c000003e syscall=10 success=no exit=-13 a0=7f0bf0644000 a1=4f80 a2=5 a3=7f0bf043d300 items=0 ppid=455 pid=737 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=ttyS0 ses=3 comm="mprotect" exe="/root/host/mprotect" subj=kernel key=(null) > + type=1327 audit(1653364370.067:61): proctitle=686F73742F6D70726F7465637400534800527C5700527C5800706C61696E2F657865637665 > + > + type=1420 audit(1653364735.161:64): rule="DEFAULT op=EXECUTE action=DENY" > + type=1300 audit(1653364735.161:64): arch=c000003e syscall=9 success=no exit=-13 a0=0 a1=1000 a2=4 a3=20 items=0 ppid=455 pid=774 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=ttyS0 ses=3 comm="mmap" exe="/root/host/mmap" subj=kernel key=(null) > + type=1327 audit(1653364735.161:64): proctitle=686F73742F6D6D617000410058⏎ > + > +This event indicates that IPE made an access control decision; the IPE specific > +record (1420) will always be emitted in conjunction with a ``AUDITSYSCALL`` record. > + > +Determining whether IPE is in permissive can be derived from the success and exit > +field of the AUDITSYSCALL record > + > + > + > +Field descriptions: > + > ++---------------+------------+-----------+-------------------------------------------------------------------------+ > +| Field | Value Type | Optional? | Description of Value | > ++===============+============+===========+=========================================================================+ > +| path | string | Yes | The absolute path to the file that was the subject of the evaluation | > ++---------------+------------+-----------+-------------------------------------------------------------------------+ > +| ino | integer | Yes | The inode number of the file that was the subject of the evaluation | > ++---------------+------------+-----------+-------------------------------------------------------------------------+ > +| dev | string | Yes | The device name that the file under evaluation belongs to, e.g. vda | > ++---------------+------------+-----------+-------------------------------------------------------------------------+ > +| rule | string | No | The exact rule in IPE's policy that the evaluation matched | > ++---------------+------------+-----------+-------------------------------------------------------------------------+ > + > +1403 AUDIT_MAC_POLICY_LOAD > +^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > +Event Example:: > + > + type=1403 audit(1653425529.927:53): policy_name="dmverity_roothash" policy_version=0.0.0 sha256=DC67AC19E05894EFB3170A8E55DE529794E248C2 auid=4294967295 ses=4294967295 lsm=ipe res=1 > + type=1300 audit(1653425529.927:53): arch=c000003e syscall=1 success=yes exit=2567 a0=3 a1=5596fcae1fb0 a2=a07 a3=2 items=0 ppid=184 pid=229 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 ses=4294967295 comm="python3" exe="/usr/bin/python3.10" key=(null) > + type=1327 audit(1653425529.927:53): PROCTITLE proctitle=707974686F6E3300746573742F6D61696E2E7079002D66002E2E > + > +This record will always be emitted in conjunction with a ``AUDITSYSCALL`` record for the ``write`` syscall. > + > ++----------------+------------+-----------+--------------------------------------------------------------+ > +| Field | Value Type | Optional? | Description of Value | > ++================+============+===========+==============================================================+ > +| policy_name | string | No | The policy_name field of the policy. | > ++----------------+------------+-----------+--------------------------------------------------------------+ > +| policy_version | string | No | The policy_version field of the policy | > ++----------------+------------+-----------+--------------------------------------------------------------+ > +| sha256 | string | Yes* | A flat hash of the policy. Can be used to identify a policy. | > ++----------------+------------+-----------+--------------------------------------------------------------+ > +| auid | integer | No | The audit user ID. | > ++----------------+------------+-----------+--------------------------------------------------------------+ > +| ses | integer | No | The session ID. | > ++----------------+------------+-----------+--------------------------------------------------------------+ > +| lsm | string | No | The lsm name associated with the event. | > ++----------------+------------+-----------+--------------------------------------------------------------+ > +| res | integer | No | The operation result. | > ++----------------+------------+-----------+--------------------------------------------------------------+ > + > +1405 AUDIT_MAC_CONFIG_CHANGE > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > +Event Example:: > + > + type=1405 audit(1653425583.136:54): old_active_pol_name="Allow_All" old_active_pol_version=0.0.0 old_sha256=DA39A3EE5E6B4B0D3255BFEF95601890AFD80709 new_active_pol_name="dmverity_roothash" new_active_pol_version=0.0.0 new_sha256=DC67AC19E05894EFB3170A8E55DE529794E248C2 auid=4294967295 ses=4294967295 lsm=ipe res=1 > + type=1300 audit(1653425583.136:54): SYSCALL arch=c000003e syscall=1 success=yes exit=2 a0=3 a1=5596fcae1fb0 a2=2 a3=2 items=0 ppid=184 pid=229 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 ses=4294967295 comm="python3" exe="/usr/bin/python3.10" key=(null) > + type=1327 audit(1653425583.136:54): PROCTITLE proctitle=707974686F6E3300746573742F6D61696E2E7079002D66002E2 > + > +This record will always be emitted in conjunction with a ``AUDITSYSCALL`` record for the ``write`` syscall. > + > ++------------------------+------------+-----------+----------------------------------------------------+ > +| Field | Value Type | Optional? | Description of Value | > ++========================+============+===========+====================================================+ > +| old_active_pol_name | string | No | The policy_name field of the old active policy. | > ++------------------------+------------+-----------+----------------------------------------------------+ > +| old_active_pol_version | string | No | The policy_version field of the old active policy. | > ++------------------------+------------+-----------+----------------------------------------------------+ > +| old_sha256 | string | Yes* | A flat hash of the old active policy. | > ++------------------------+------------+-----------+----------------------------------------------------+ > +| new_active_pol_name | string | No | The policy_name field of the new active policy. | > ++------------------------+------------+-----------+----------------------------------------------------+ > +| new_active_pol_version | string | No | The policy_version field of the new active policy. | > ++------------------------+------------+-----------+----------------------------------------------------+ > +| new_sha256 | string | Yes* | A flat hash of the new active policy. | > ++------------------------+------------+-----------+----------------------------------------------------+ > +| auid | integer | No | The audit user ID. | > ++------------------------+------------+-----------+----------------------------------------------------+ > +| ses | integer | No | The session ID. | > ++------------------------+------------+-----------+----------------------------------------------------+ > +| lsm | string | No | The lsm name associated with the event. | > ++------------------------+------------+-----------+----------------------------------------------------+ > +| res | integer | No | The operation result. | > ++------------------------+------------+-----------+----------------------------------------------------+ > + > +1404 AUDIT_MAC_STATUS > +^^^^^^^^^^^^^^^^^^^^^ > + > +Event Examples:: > + > + type=1404 audit(1653425689.008:55): permissive=1 auid=0 ses=4294967295 lsm=ipe res=1 > + type=1300 audit(1653425689.008:55): arch=c000003e syscall=1 success=yes exit=2 a0=1 a1=55c1065e5c60 a2=2 a3=0 items=0 ppid=405 pid=441 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=) > + type=1327 audit(1653425689.008:55): proctitle="-bash" > + > + type=1404 audit(1653425689.008:55): permissive=0 auid=0 ses=4294967295 lsm=ipe res=1 > + type=1300 audit(1653425689.008:55): arch=c000003e syscall=1 success=yes exit=2 a0=1 a1=55c1065e5c60 a2=2 a3=0 items=0 ppid=405 pid=441 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=) > + type=1327 audit(1653425689.008:55): proctitle="-bash" > + > +This record will always be emitted in conjunction with a ``AUDITSYSCALL`` record for the ``write`` syscall. > + > ++------------+------------+-----------+-------------------------------------------------------------------+ > +| Field | Value Type | Optional? | Description of Value | > ++============+============+===========+===================================================================+ > +| permissive | integer | No | The state IPE is being switched to. 1 is permissive, 0 is enforce | > ++------------+------------+-----------+-------------------------------------------------------------------+ > +| auid | integer | No | The audit user ID. | > ++------------+------------+-----------+-------------------------------------------------------------------+ > +| ses | integer | No | The session ID. | > ++------------+------------+-----------+-------------------------------------------------------------------+ > +| lsm | string | No | The lsm name associated with the event. | > ++------------+------------+-----------+-------------------------------------------------------------------+ > +| res | integer | No | The operation result. | > ++------------+------------+-----------+-------------------------------------------------------------------+ > + > +Success Auditing > +^^^^^^^^^^^^^^^^ > + > +IPE supports success auditing. When enabled, all events that pass IPE > +policy and are not blocked will emit an audit event. This is disabled by > +default, and can be enabled via the kernel command line > +``ipe.success_audit=(0|1)`` or the securityfs node, > +``/sys/kernel/security/ipe/success_audit``. > + > +This is *very* noisy, as IPE will check every userspace binary on the > +system, but is useful for debugging policies. > + > +.. NOTE:: > + > + If a traditional MAC system is enabled (SELinux, apparmor, smack, etcetera), > + all writes to ipe's securityfs nodes require ``CAP_MAC_ADMIN``. > + > +Properties > +---------- > + > +As explained above, IPE properties are ``key=value`` pairs expressed in > +IPE policy. Two properties are built-into the policy parser: 'op' and > +'action'. The other properties are determinstic attributes to express > +across files. Currently those properties are: '``boot_verified``', > +'``dmverity_signature``', '``dmverity_roothash``', '``fsverity_signature``', > +'``fsverity_digest``'. A description of all properties supported by IPE > +are listed below: > + > +op > +~~ > + > +Indicates the operation for a rule to apply to. Must be in every rule, > +as the first token. IPE supports the following operations: > + > + ``EXECUTE`` > + > + Pertains to any file attempting to be executed, or loaded as an > + executable. > + > + ``FIRMWARE``: > + > + Pertains to firmware being loaded via the firmware_class interface. > + This covers both the preallocated buffer and the firmware file > + itself. > + > + ``KMODULE``: > + > + Pertains to loading kernel modules via ``modprobe`` or ``insmod``. > + > + ``KEXEC_IMAGE``: > + > + Pertains to kernel images loading via ``kexec``. > + > + ``KEXEC_INITRAMFS`` > + > + Pertains to initrd images loading via ``kexec --initrd``. > + > + ``POLICY``: > + > + Controls loading polcies via reading a kernel-space initiated read. > + > + An example of such is loading IMA policies by writing the path > + to the policy file to ``$securityfs/ima/policy`` > + > + ``X509_CERT``: > + > + Controls loading IMA certificates through the Kconfigs, > + ``CONFIG_IMA_X509_PATH`` and ``CONFIG_EVM_X509_PATH``. > + > +action > +~~~~~~ > + > + Determines what IPE should do when a rule matches. Must be in every > + rule, as the final clause. Can be one of: > + > + ``ALLOW``: > + > + If the rule matches, explicitly allow access to the resource to proceed > + without executing any more rules. > + > + ``DENY``: > + > + If the rule matches, explicitly prohibit access to the resource to > + proceed without executing any more rules. > + > +boot_verified > +~~~~~~~~~~~~~ > + > + This property can be utilized for authorization of the first super-block > + that executes a file. This is almost always init. Typically this is used > + for systems with an initramfs or other initial disk, where this is unmounted > + before the system becomes available, and is not covered by any other property. > + The format of this property is:: > + > + boot_verified=(TRUE|FALSE) > + > + > + .. WARNING:: > + > + This property will trust any disk where the first execution evaluation > + occurs. If you do *NOT* have a startup disk that is unpacked and unmounted > + (like initramfs), then it will automatically trust the root filesystem and > + potentially overauthorize the entire disk. > + > +dmverity_roothash > +~~~~~~~~~~~~~~~~~ > + > + This property can be utilized for authorization or revocation of > + specific dm-verity volumes, identified via root hash. It has a > + dependency on the DM_VERITY module. This property is controlled by the > + Kconfig ``CONFIG_IPE_PROP_DM_VERITY``. The format of this property > + is:: > + > + dmverity_roothash=DigestName:HexadecimalString > + > + The supported DigestNames for dmverity_roothash are [#dmveritydigests]_ [#securedigest]_ : > + > + + blake2b-512 > + + blake2s-256 > + + sha1 > + + sha256 > + + sha384 > + + sha512 > + + sha3-224 > + + sha3-256 > + + sha3-384 > + + sha3-512 > + + md4 > + + md5 > + + sm3 > + + rmd160 > + > +dmverity_signature > +~~~~~~~~~~~~~~~~~~ > + > + This property can be utilized for authorization of all dm-verity volumes > + that have a signed roothash that chains to a keyring specified by dm-verity's > + configuration, either the system trusted keyring, or the secondary keyring. > + It has an additional dependency on the ``DM_VERITY_VERIFY_ROOTHASH_SIG`` > + Kconfig. This property is controlled by the Kconfig > + ``CONFIG_IPE_PROP_DM_VERITY``. The format of this property is:: > + > + dmverity_signature=(TRUE|FALSE) > + > +fsverity_digest > +~~~~~~~~~~~~~~~ > + > + This property can be utilized for authorization or revocation of > + specific fsverity enabled file, identified via its fsverity digest. > + It has a dependency on the FS_VERITY module. This property is > + controlled by the Kconfig ``CONFIG_IPE_PROP_FS_VERITY``. > + The format of this property is:: > + > + fsverity_digest=DigestName:HexadecimalString > + > + The supported DigestNames for dmverity_roothash are [#fsveritydigest] [#securedigest]_ : > + > + + sha256 > + + sha512 > + > +fsverity_signature > +~~~~~~~~~~~~~~~~~~ > + > +Version 1 > + > + This property can be utilized for authorization of all fsverity enabled > + files that is verified by fsverity. The keyring that the signature is > + verified against is subject to fsverity's configuration, typically the fsverity > + keyring. It has a dependency on the ``CONFIG_FS_VERITY_BUILTIN_SIGNATURES`` > + Kconfig. This property is controlled by the Kconfig > + ``CONFIG_IPE_PROP_FS_VERITY``. The format of this property is:: > + > + fsverity_signature=(TRUE|FALSE) > + > +Policy Examples > +--------------- > + > +Allow all > +~~~~~~~~~ > + > +:: > + > + policy_name=Allow_All policy_version=0.0.0 > + DEFAULT action=ALLOW > + > +Allow only initial superblock > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + > +:: > + > + policy_name=Allow_All_Initial_SB policy_version=0.0.0 > + DEFAULT action=DENY > + > + op=EXECUTE boot_verified=TRUE action=ALLOW > + > +Allow any signed dm-verity volume and the initial superblock > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + > +:: > + > + policy_name=AllowSignedAndInitial policy_version=0.0.0 > + DEFAULT action=DENY > + > + op=EXECUTE boot_verified=TRUE action=ALLOW > + op=EXECUTE dmverity_signature=TRUE action=ALLOW > + > +Prohibit execution from a specific dm-verity volume > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + > +:: > + > + policy_name=AllowSignedAndInitial policy_version=0.0.0 > + DEFAULT action=DENY > + > + op=EXECUTE dmverity_roothash=sha256:cd2c5bae7c6c579edaae4353049d58eb5f2e8be0244bf05345bc8e5ed257baff action=DENY > + > + op=EXECUTE boot_verified=TRUE action=ALLOW > + op=EXECUTE dmverity_signature=TRUE action=ALLOW > + > +Allow only a specific dm-verity volume > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + > +:: > + > + policy_name=AllowSignedAndInitial policy_version=0.0.0 > + DEFAULT action=DENY > + > + op=EXECUTE dmverity_roothash=sha256:401fcec5944823ae12f62726e8184407a5fa9599783f030dec146938 action=ALLOW > + > +Allow any signed fs-verity file > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + > +:: > + > + policy_name=AllowSignedFSVerity policy_version=0.0.0 > + DEFAULT action=DENY > + > + op=EXECUTE fsverity_signature=TRUE action=ALLOW > + > +Prohibit execution of a specific fs-verity file > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + > +:: > + > + policy_name=ProhibitSpecificFSVF policy_version=0.0.0 > + DEFAULT action=DENY > + > + op=EXECUTE fsverity_digest=sha256:fd88f2b8824e197f850bf4c5109bea5cf0ee38104f710843bb72da796ba5af9e action=DENY > + op=EXECUTE boot_verified=TRUE action=ALLOW > + op=EXECUTE dmverity_signature=TRUE action=ALLOW > + > +Additional Information > +---------------------- > + > +- `Github Repository <https://github.com/microsoft/ipe>`_ > +- `Design Documentation </security/ipe>`_ > + > +FAQ > +--- > + > +Q: > + What's the difference between other LSMs which provide a measure of > + trust-based access control? > + > +A: > + > + In general, there's two other LSMs that can provide similar functionality: > + IMA, and Loadpin. > + > + IMA and IPE are functionally very similar. The significant difference between > + the two is the policy. [#devdoc]_ > + > + Loadpin and IPE differ fairly dramatically, as Loadpin controls only the IPE > + equivalent of ``KERNEL_READ``, whereas IPE is capable of controlling execution, > + on top of ``KERNEL_READ``. The trust model is also different; Loadpin roots its > + trust in the initial super-block, instead, IPE roots its trust in the kernel > + itself (via ``SYSTEM_TRUSTED_KEYS``). > + > +----------- > + > +.. [#diglim] 1: https://lore.kernel.org/bpf/4d6932e96d774227b42721d9f645ba51@xxxxxxxxxx/T/ > + > +.. [#interpreters] There is `some interest in solving this issue <https://lore.kernel.org/lkml/20220321161557.495388-1-mic@xxxxxxxxxxx/>`_. > + > +.. [#devdoc] Please see `Documentation/security/ipe.rst` for more on this topic. > + > +.. [#fsveritydigest] These hash algorithms are based on values accepted by fsverity-utils; > + IPE does not impose any restrictions on the digest algorithm itself; > + thus, this list may be out of date. > + > +.. [#dmveritydigests] These hash algorithms are based on values accepted by dm-verity, > + specifically ``crypto_alloc_ahash`` in ``verity_ctr``; ``veritysetup`` > + does support more algorithms than the list above. IPE does not impose > + any restrictions on the digest algorithm itself; thus, this list > + may be out of date. > + > +.. [#securedigest] Please ensure you are using cryptographically secure hash functions; > + just because something is *supported* does not mean it is *secure*. What about wordings below instead? ---- >8 ---- diff --git a/Documentation/admin-guide/LSM/ipe.rst b/Documentation/admin-guide/LSM/ipe.rst index b676cea62b2e74..8b1d4eb0ebf19f 100644 --- a/Documentation/admin-guide/LSM/ipe.rst +++ b/Documentation/admin-guide/LSM/ipe.rst @@ -31,7 +31,9 @@ system to accomplish the desired tasks. One such provider is for example dm-verity, which is able to represent the integrity property of a partition (its immutable state) with a digest. -IPE is compiled under ``CONFIG_SECURITY_IPE`` (Security -> Integrity Policy Enforcement (IPE)). +To enable IPE, ensure that ``CONFIG_SECURITY_IPE`` (under +:menuselection:`Security -> Integrity Policy Enforcement (IPE)`) config +option is enabled. Use Cases --------- @@ -42,11 +44,10 @@ device in a data center, an IoT device, etcetera), where all software and configuration is built and provisioned by the system owner. IPE is a long-way off for use in general-purpose computing: the Linux -community as a whole tends to follow a decentralized trust model, -known as the web of trust, which IPE has no support for as of yet. - -IPE, instead of supporting web of trust, supports PKI, which generally -designates a set of entities that provide a measure of absolute trust. +community as a whole tends to follow a decentralized trust model (known as +the web of trust), which IPE has no support for it yet. Instead, IPE +supports PKI (public key infrastructure), which generally designates a +set of trusted entities that provide a measure of absolute trust. Additionally, while most packages are signed today, the files inside the packages (for instance, the executables), tend to be unsigned. This @@ -55,10 +56,10 @@ expected to be functional, without major changes to the package manager and ecosystem behind it. DIGLIM [#diglim]_ is a system that when combined with IPE, could be used to -enable general purpose computing scenarios. +enable and support general-purpose computing use cases. -Known Gaps ----------- +Known Limitations +----------------- IPE cannot verify the integrity of anonymous executable memory, such as the trampolines created by gcc closures and libffi (<3.4.2), or JIT'd code. @@ -67,11 +68,12 @@ for IPE to ensure the integrity of this code to form a trust basis. In all cases, the return result for these operations will be whatever the admin configures as the ``DEFAULT`` action for ``EXECUTE``. -IPE cannot verify the integrity of interpreted languages' programs when -these scripts are invoked via ``<interpreter> <file>``. This is because -the way interpreters execute these files, the scripts themselves are not -evaluated as executable code through one of IPE's hooks, as they are merely -files that are read (as opposed to executable code) [#interpreters]_. +IPE cannot verify the integrity of programs written in interpreted +languages when these scripts are invoked by passing these program files +to the interpreter. This is because the way interpreters execute these +files; the scripts themselves are not evaluated as executable code +through one of IPE's hooks, but they are merely text files that are read +(as opposed to compiled executables) [#interpreters]_. Threat Model ------------ @@ -82,17 +84,19 @@ kernel modules that are loaded in userspace through ``modprobe`` or ``insmod``. A bare-minimum example of a threat that should be mitigated by IPE, is -a hostile binary is downloaded with all required binaries (including -a loader, libc, etc). With IPE, this hostile binary should not able to -be executed, nor any of the downloaded binaries. +an untrusted (potentially malicious) binary that is downloaded and +bundled with all required dependencies (including a loader, libc, etc). +With IPE, this binary should not be allowed to be executed, not even any +of its dependencies. -Tampering violates integrity, and being unable to verify the integrity, -results in a lack of trust. IPE's role in mitigating this threat is to -verify the integrity (and authenticity) of all executable code and to -deny their use if they cannot be trusted (as integrity verification fails, -or the authorization check fails against the reference value in the policy). -IPE generates audit logs which may be utilized to detect failures resulting -from failure to pass policy. +Tampering violates integrity, yet lack of trust is caused by being +unable to detect tampering (and by extent verifying the integrity). +IPE's role in mitigating this threat is to verify the integrity (and +authenticity) of all executable code and to deny their use if they +cannot be trusted (as integrity verification fails, or the authorization +check fails against the reference value in the policy). IPE generates +audit logs which may be utilized to detect and analyze failures +resulting from policy violation. Tampering threat scenarios include modification or replacement of executable code by a range of actors including: @@ -105,13 +109,13 @@ executable code by a range of actors including: - Compromised end users of the system - Remote (external) compromise of the system -IPE does not mitigate threats arising from malicious authorized +IPE does not mitigate threats arising from malicious but authorized developers (with access to a signing certificate), or compromised -developer tools used by authorized developers (i.e. Return Oriented -Programming attacks). Additionally, IPE draws hard security boundary -between userspace and kernelspace. As a result, IPE does not provide -any protections against a kernel level exploit, and a kernel-level -exploit can disable or tamper with IPE's protections. +developer tools used by them (i.e. return-oriented programming attacks). +Additionally, IPE draws hard security boundary between userspace and +kernelspace. As a result, IPE does not provide any protections against a +kernel level exploit, and a kernel-level exploit can disable or tamper +with IPE's protections. Policy ------ @@ -133,11 +137,11 @@ policy syntax version). This is used to prevent rollback of policy to potentially insecure previous versions of the policy. The next portion of IPE policy are rules. Rules are formed by key=value -pairs, known as properties. IPE rules require two properties: "action", +pairs, known as properties. IPE rules require two properties: ``action``, which determines what IPE does when it encounters a match against the -rule, and "op", which determines when that rule should be evaluated. -The ordering is significant, a rule must start with "op", and end with -"action". Thus, a minimal rule is:: +rule, and ``op``, which determines when the rule should be evaluated. +The ordering is significant, a rule must start with ``op``, and end with +``action``. Thus, a minimal rule is:: op=EXECUTE action=ALLOW @@ -145,14 +149,14 @@ This example will allow any execution. Additional properties are used to restrict attributes about the files being evaluated. These properties are intended to be descriptions of systems within the kernel that can provide a measure of integrity verification, such that IPE can determine -the trust of the resource based on the "value" half of the property. +the trust of the resource based on the value of the property. Rules are evaluated top-to-bottom. As a result, any revocation rules, or denies should be placed early in the file to ensure that these rules -are evaluated before a rule with "action=ALLOW" is hit. +are evaluated before a rule with ``action=ALLOW``. -IPE policy supports comments. The character '#' will function as a -comment, ignoring all characters to the right of '#' until the newline. +IPE policy supports comments. Any line which is prefixed with ``#`` will +be ignored. The default behavior of IPE evaluations can also be expressed in policy, through the ``DEFAULT`` statement. This can be done at a global level, @@ -166,8 +170,8 @@ or a per-operation level:: A default must be set for all known operations in IPE. If you want to preserve older policies being compatible with newer kernels that can introduce -new operations, please set a global default of 'ALLOW', and override the -defaults on a per-operation basis. +new operations, set a global default of ``ALLOW``, then override the +defaults on a per-operation basis (as above). With configurable policy-based LSMs, there's several issues with enforcing the configurable policies at startup, around reading and @@ -182,14 +186,14 @@ parsing the policy: off a memory block would be costly to maintain. As a result, IPE has addressed this problem through a concept of a "boot -policy". A boot policy is a minimal policy, compiled into the kernel. -This policy is intended to get the system to a state where userspace is -set up and ready to receive commands, at which point a more complex -policy can be deployed via securityfs. The boot policy can be specified -via the Kconfig, ``SECURITY_IPE_BOOT_POLICY``, which accepts a path to -a plain-text version of the IPE policy to apply. This policy will be -compiled into the kernel. If not specified, IPE will be disabled until -a policy is deployed and activated through securityfs. +policy". A boot policy is a minimal policy which is compiled into the +kernel. This policy is intended to get the system to a state where +userspace is set up and ready to receive commands, at which point a more +complex policy can be deployed via securityfs. The boot policy can be +specified via ``SECURITY_IPE_BOOT_POLICY`` config option, which accepts +a path to a plain-text version of the IPE policy to apply. This policy +will be compiled into the kernel. If not specified, IPE will be disabled +until a policy is deployed and activated through securityfs. Deploying Policies ~~~~~~~~~~~~~~~~~~ @@ -199,7 +203,7 @@ are signed through the PKCS#7 message format to enforce some level of authorization of the policies (prohibiting an attacker from gaining unconstrained root, and deploying an "allow all" policy). These policies must be signed by a certificate that chains to the -``SYSTEM_TRUSTED_KEYRING``. Through openssl, the signing can be done via:: +``SYSTEM_TRUSTED_KEYRING``. With openssl, the policy can be signed by:: openssl smime -sign \ -in "$MY_POLICY" \ @@ -224,12 +228,12 @@ the directory will be ``/sys/kernel/security/ipe/policies/Ex_Policy``. Within this directory, there will be five files: ``pkcs7``, ``policy``, ``active``, ``update``, and ``delete``. -The ``pkcs7`` file is read only. Reading will provide the raw PKCS#7 data +The ``pkcs7`` file is read-only. Reading it returns the raw PKCS#7 data that was provided to the kernel, representing the policy. Writing, will -deploy an in-place policy update.If the policy being read is the boot -policy, when read, this will return ENOENT, as this policy is not signed. +deploy an in-place policy update. If the policy being read is the boot +policy, this will return ``ENOENT``, as it is is not signed. -The ``policy`` file is read only. Reading will provide the PKCS#7 inner +The ``policy`` file is read-only. Reading it returns the PKCS#7 inner content of the policy, which will be the plain text policy. The ``active`` file is used to set a policy as the currently active policy. @@ -238,44 +242,42 @@ Since only a single policy can be active at one time, all other policies will be marked inactive. The policy being marked active must have a policy version greater or equal to the currently-running version. -The ``update`` file is used to update a policy that is already present in -the kernel. This file is write-only and accepts a PKCS#7 signed policy. -One check will always be performed on this policy: the policy_names must -match with the updated version and the existing version. One additional check -may be made: If the policy being updated is the active policy, the updated -policy must have a policy version greater than or equal to the currently-running -version; This is to prevent rollback attacks. +The ``update`` file is used to update a policy that is already present +in the kernel. This file is write-only and accepts a PKCS#7 signed +policy. One check will always be performed on this policy: the +``policy_names`` must match with the updated version and the existing +version. There is also an additional check: if the policy being updated +is the active policy, the updated policy must have a policy version +greater than or equal to the currently-running version. This is to +prevent rollback attacks. The ``delete`` file is used to remove a policy that is no longer needed. This file is write-only and accepts a value of ``1`` to delete the policy. On deletion, the securityfs node representing the policy will be removed. The policy that is currently active cannot be deleted. -Similarly, the writes to both ``update`` and ``new_policy`` above will -result in an error upon syntactically invalid or untrusted policies. -In the case of ``new_policy``, it will also error if a policy already -exists with the same ``policy_name``. +Similarly, writing to both ``update`` and ``new_policy`` results in +syntax or untrusted policy error. In the case of the latter, it will +also error out if a policy already exists with the same ``policy_name``. Deploying these policies will *not* cause IPE to start enforcing this -policy. Once deployment is successful, a policy can be marked as active, -via ``/sys/kernel/security/ipe/$policy_name/active``. IPE will enforce -whatever policy is marked as active. For our example, we can activate -the ``Ex_Policy`` via:: +policy. Once deployment is successful, a policy can be activated, by +``/sys/kernel/security/ipe/$policy_name/active``. IPE will enforce +active policies. For example, the ``Ex_Policy`` can be activated by:: echo 1 > "/sys/kernel/security/ipe/Ex_Policy/active" -At which point, ``Ex_Policy`` will now be the enforced policy on the +From above point on, ``Ex_Policy`` is now the enforced policy on the system. IPE also provides a way to delete policies. This can be done via the ``delete`` securityfs node, ``/sys/kernel/security/ipe/$policy_name/delete``. -Writing ``1`` to that file will delete that node:: +Writing ``1`` to that file deletes the policy:: echo 1 > "/sys/kernel/security/ipe/$policy_name/delete" -There is only one requirement to delete a policy: - -1. The policy being deleted must not be the active policy. +There is only one requirement to delete a policy: the policy being deleted +must be inactive. .. NOTE:: @@ -286,9 +288,9 @@ Modes ~~~~~ IPE supports two modes of operation: permissive (similar to SELinux's -permissive mode) and enforce. Permissive mode performs the same checks -as enforce mode, and logs policy violations, but will not enforce the -policy. This allows users to test policies before enforcing them. +permissive mode) and enforced. In permissive mode, all events are +checked and policy violations are logged, but the policy is not really +enforced. This allows users to test policies before enforcing them. The default mode is enforce, and can be changed via the kernel command line parameter ``ipe.enforce=(0|1)``, or the securityfs node @@ -314,11 +316,12 @@ Event Examples:: type=1300 audit(1653364735.161:64): arch=c000003e syscall=9 success=no exit=-13 a0=0 a1=1000 a2=4 a3=20 items=0 ppid=455 pid=774 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=ttyS0 ses=3 comm="mmap" exe="/root/host/mmap" subj=kernel key=(null) type=1327 audit(1653364735.161:64): proctitle=686F73742F6D6D617000410058⏎ -This event indicates that IPE made an access control decision; the IPE specific -record (1420) will always be emitted in conjunction with a ``AUDITSYSCALL`` record. +This event indicates that IPE made an access control decision; the IPE +specific record (1420) is always emitted in conjunction with a +``AUDITSYSCALL`` record. -Determining whether IPE is in permissive can be derived from the success and exit -field of the AUDITSYSCALL record +Determining whether IPE is in permissive or enforced mode can be derived +from ``success`` property and exit code of the ``AUDITSYSCALL`` record. @@ -327,13 +330,13 @@ Field descriptions: +---------------+------------+-----------+-------------------------------------------------------------------------+ | Field | Value Type | Optional? | Description of Value | +===============+============+===========+=========================================================================+ -| path | string | Yes | The absolute path to the file that was the subject of the evaluation | +| path | string | Yes | The absolute path to the evaluated file | +---------------+------------+-----------+-------------------------------------------------------------------------+ -| ino | integer | Yes | The inode number of the file that was the subject of the evaluation | +| ino | integer | Yes | The inode number of the evaluated file | +---------------+------------+-----------+-------------------------------------------------------------------------+ -| dev | string | Yes | The device name that the file under evaluation belongs to, e.g. vda | +| dev | string | Yes | The device name of the evaluated file, e.g. vda | +---------------+------------+-----------+-------------------------------------------------------------------------+ -| rule | string | No | The exact rule in IPE's policy that the evaluation matched | +| rule | string | No | The matched policy rule | +---------------+------------+-----------+-------------------------------------------------------------------------+ 1403 AUDIT_MAC_POLICY_LOAD @@ -350,11 +353,11 @@ This record will always be emitted in conjunction with a ``AUDITSYSCALL`` record +----------------+------------+-----------+--------------------------------------------------------------+ | Field | Value Type | Optional? | Description of Value | +================+============+===========+==============================================================+ -| policy_name | string | No | The policy_name field of the policy. | +| policy_name | string | No | The policy name | +----------------+------------+-----------+--------------------------------------------------------------+ -| policy_version | string | No | The policy_version field of the policy | +| policy_version | string | No | The policy version | +----------------+------------+-----------+--------------------------------------------------------------+ -| sha256 | string | Yes* | A flat hash of the policy. Can be used to identify a policy. | +| sha256 | string | Yes* | The policy hash | +----------------+------------+-----------+--------------------------------------------------------------+ | auid | integer | No | The audit user ID. | +----------------+------------+-----------+--------------------------------------------------------------+ @@ -379,17 +382,17 @@ This record will always be emitted in conjunction with a ``AUDITSYSCALL`` record +------------------------+------------+-----------+----------------------------------------------------+ | Field | Value Type | Optional? | Description of Value | +========================+============+===========+====================================================+ -| old_active_pol_name | string | No | The policy_name field of the old active policy. | +| old_active_pol_name | string | No | The name of previous active policy | +------------------------+------------+-----------+----------------------------------------------------+ -| old_active_pol_version | string | No | The policy_version field of the old active policy. | +| old_active_pol_version | string | No | The version of previous active policy | +------------------------+------------+-----------+----------------------------------------------------+ -| old_sha256 | string | Yes* | A flat hash of the old active policy. | +| old_sha256 | string | Yes* | The hash of previous active policy | +------------------------+------------+-----------+----------------------------------------------------+ -| new_active_pol_name | string | No | The policy_name field of the new active policy. | +| new_active_pol_name | string | No | The name of current active policy | +------------------------+------------+-----------+----------------------------------------------------+ -| new_active_pol_version | string | No | The policy_version field of the new active policy. | +| new_active_pol_version | string | No | The version of current active policy | +------------------------+------------+-----------+----------------------------------------------------+ -| new_sha256 | string | Yes* | A flat hash of the new active policy. | +| new_sha256 | string | Yes* | The hash of current active policy | +------------------------+------------+-----------+----------------------------------------------------+ | auid | integer | No | The audit user ID. | +------------------------+------------+-----------+----------------------------------------------------+ @@ -415,19 +418,19 @@ Event Examples:: This record will always be emitted in conjunction with a ``AUDITSYSCALL`` record for the ``write`` syscall. -+------------+------------+-----------+-------------------------------------------------------------------+ -| Field | Value Type | Optional? | Description of Value | -+============+============+===========+===================================================================+ -| permissive | integer | No | The state IPE is being switched to. 1 is permissive, 0 is enforce | -+------------+------------+-----------+-------------------------------------------------------------------+ -| auid | integer | No | The audit user ID. | -+------------+------------+-----------+-------------------------------------------------------------------+ -| ses | integer | No | The session ID. | -+------------+------------+-----------+-------------------------------------------------------------------+ -| lsm | string | No | The lsm name associated with the event. | -+------------+------------+-----------+-------------------------------------------------------------------+ -| res | integer | No | The operation result. | -+------------+------------+-----------+-------------------------------------------------------------------+ ++------------+------------+-----------+-------------------------------------------------------------------------------------+ +| Field | Value Type | Optional? | Description of Value | ++============+============+===========+=====================================================================================+ +| permissive | integer | No | The state IPE is being switched to. 1 is in permissive mode; 0 is in enforced mode. | ++------------+------------+-----------+-------------------------------------------------------------------------------------+ +| auid | integer | No | The audit user ID. | ++------------+------------+-----------+-------------------------------------------------------------------------------------+ +| ses | integer | No | The session ID. | ++------------+------------+-----------+-------------------------------------------------------------------------------------+ +| lsm | string | No | The lsm name associated with the event. | ++------------+------------+-----------+-------------------------------------------------------------------------------------+ +| res | integer | No | The operation result. | ++------------+------------+-----------+-------------------------------------------------------------------------------------+ Success Auditing ^^^^^^^^^^^^^^^^ @@ -435,8 +438,8 @@ Success Auditing IPE supports success auditing. When enabled, all events that pass IPE policy and are not blocked will emit an audit event. This is disabled by default, and can be enabled via the kernel command line -``ipe.success_audit=(0|1)`` or the securityfs node, -``/sys/kernel/security/ipe/success_audit``. +``ipe.success_audit=(0|1)`` or +``/sys/kernel/security/ipe/success_audit`` securityfs file. This is *very* noisy, as IPE will check every userspace binary on the system, but is useful for debugging policies. @@ -538,9 +541,9 @@ dmverity_roothash This property can be utilized for authorization or revocation of specific dm-verity volumes, identified via root hash. It has a - dependency on the DM_VERITY module. This property is controlled by the - Kconfig ``CONFIG_IPE_PROP_DM_VERITY``. The format of this property - is:: + dependency on the DM_VERITY module. This property is controlled by + the ``CONFIG_IPE_PROP_DM_VERITY`` config option. The format of this + property is:: dmverity_roothash=DigestName:HexadecimalString @@ -564,11 +567,11 @@ dmverity_roothash dmverity_signature ~~~~~~~~~~~~~~~~~~ - This property can be utilized for authorization of all dm-verity volumes - that have a signed roothash that chains to a keyring specified by dm-verity's - configuration, either the system trusted keyring, or the secondary keyring. - It has an additional dependency on the ``DM_VERITY_VERIFY_ROOTHASH_SIG`` - Kconfig. This property is controlled by the Kconfig + This property can be utilized for authorization of all dm-verity + volumes that have a signed roothash that chains to a keyring + specified by dm-verity's configuration, either the system trusted + keyring, or the secondary keyring. It depends on + ``DM_VERITY_VERIFY_ROOTHASH_SIG`` config option and is controlled by ``CONFIG_IPE_PROP_DM_VERITY``. The format of this property is:: dmverity_signature=(TRUE|FALSE) @@ -578,9 +581,8 @@ fsverity_digest This property can be utilized for authorization or revocation of specific fsverity enabled file, identified via its fsverity digest. - It has a dependency on the FS_VERITY module. This property is - controlled by the Kconfig ``CONFIG_IPE_PROP_FS_VERITY``. - The format of this property is:: + It depends on ``FS_VERITY`` config option and is controlled by + ``CONFIG_IPE_PROP_FS_VERITY``. The format of this property is:: fsverity_digest=DigestName:HexadecimalString @@ -594,12 +596,13 @@ fsverity_signature Version 1 - This property can be utilized for authorization of all fsverity enabled - files that is verified by fsverity. The keyring that the signature is - verified against is subject to fsverity's configuration, typically the fsverity - keyring. It has a dependency on the ``CONFIG_FS_VERITY_BUILTIN_SIGNATURES`` - Kconfig. This property is controlled by the Kconfig - ``CONFIG_IPE_PROP_FS_VERITY``. The format of this property is:: + This property can be utilized for authorization of all fsverity + enabled files that is verified by fsverity. The keyring that the + signature is verified against is subject to fsverity's configuration, + typically the fsverity keyring. It depends on + ``CONFIG_FS_VERITY_BUILTIN_SIGNATURES`` is controlled controlled by + the Kconfig ``CONFIG_IPE_PROP_FS_VERITY``. The format of this + property is:: fsverity_signature=(TRUE|FALSE) @@ -704,7 +707,7 @@ A: Loadpin and IPE differ fairly dramatically, as Loadpin controls only the IPE equivalent of ``KERNEL_READ``, whereas IPE is capable of controlling execution, on top of ``KERNEL_READ``. The trust model is also different; Loadpin roots its - trust in the initial super-block, instead, IPE roots its trust in the kernel + trust in the initial super-block, whereas trust in IPE is stemmed from kernel itself (via ``SYSTEM_TRUSTED_KEYS``). ----------- Thanks. -- An old man doll... just what I always wanted! - Clara
Attachment:
signature.asc
Description: PGP signature
