Pull vfs acl updates from Christian Brauner:
"These are general fixes and preparatory changes related to the ongoing
posix acl rework. The actual rework where we build a type safe posix
acl api wasn't ready for this merge window but we're hopeful for the
next merge window.
General fixes:
- Some filesystems like 9p and cifs have to implement custom posix
acl handlers because they require access to the dentry in order to
set and get posix acls while the set and get inode operations
currently don't. But the ntfs3 filesystem has no such requirement
and thus implemented custom posix acl xattr handlers when it really
didn't have to. So this pr contains patch that just implements set
and get inode operations for ntfs3 and switches it to rely on the
generic posix acl xattr handlers. (We would've appreciated reviews
from the ntfs3 maintainers but we didn't get any. But hey, if we
really broke it we'll fix it. But fstests for ntfs3 said it's
fine.)
- The posix_acl_fix_xattr_common() helper has been adapted so it can
be used by a few more callers and avoiding open-coding the same
checks over and over.
Other than the two general fixes this series introduces a new helper
vfs_set_acl_prepare(). The reason for this helper is so that we can
mitigate one of the source that change {g,u}id values directly in the
uapi struct. With the vfs_set_acl_prepare() helper we can move the
idmapped mount fixup into the generic posix acl set handler.
The advantage of this is that it allows us to remove the
posix_acl_setxattr_idmapped_mnt() helper which so far we had to call
in vfs_setxattr() to account for idmapped mounts. While semantically
correct the problem with this approach was that we had to keep the
value parameter of the generic vfs_setxattr() call as non-const. This
is rectified in this series.
Ultimately, we will get rid of all the extreme kludges and type
unsafety once we have merged the posix api - hopefully during the next
merge window - built solely around get and set inode operations. Which
incidentally will also improve handling of posix acls in security and
especially in integrity modesl. While this will come with temporarily
having two inode operation for posix acls that is nothing compared to
the problems we have right now and so well worth it. We'll end up with
something that we can actually reason about instead of needing to
write novels to explain what's going on"
* tag 'fs.acl.rework.prep.v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping:
xattr: always us is_posix_acl_xattr() helper
acl: fix the comments of posix_acl_xattr_set
xattr: constify value argument in vfs_setxattr()
ovl: use vfs_set_acl_prepare()
acl: move idmapping handling into posix_acl_xattr_set()
acl: add vfs_set_acl_prepare()
acl: return EOPNOTSUPP in posix_acl_fix_xattr_common()
ntfs3: rework xattr handlers and switch to POSIX ACL VFS helpers
It turns out Apple doesn't capitalise the "mini" in "Macmini" in DMI, which
is inconsistent with other model line names.
Correct the capitalisation of Macmini in the quirk for skipping loading
platform certs on T2 Macs.
Currently users get:
------------[ cut here ]------------
[Firmware Bug]: Page fault caused by firmware at PA: 0xffffa30640054000
WARNING: CPU: 1 PID: 8 at arch/x86/platform/efi/quirks.c:735 efi_crash_gracefully_on_page_fault+0x55/0xe0
Modules linked in:
CPU: 1 PID: 8 Comm: kworker/u12:0 Not tainted 5.18.14-arch1-2-t2 #1 4535eb3fc40fd08edab32a509fbf4c9bc52d111e
Hardware name: Apple Inc. Macmini8,1/Mac-7BA5B2DFE22DDD8C, BIOS 1731.120.10.0.0 (iBridge: 19.16.15071.0.0,0) 04/24/2022
Workqueue: efi_rts_wq efi_call_rts
...
---[ end trace 0000000000000000 ]---
efi: Froze efi_rts_wq and disabled EFI Runtime Services
integrity: Couldn't get size: 0x8000000000000015
integrity: MODSIGN: Couldn't get UEFI db list
efi: EFI Runtime Services are disabled!
integrity: Couldn't get size: 0x8000000000000015
integrity: Couldn't get UEFI dbx list
Fixes: 155ca952c7 ("efi: Do not import certificates from UEFI Secure Boot for T2 Macs")
Cc: stable@vger.kernel.org
Cc: Aditya Garg <gargaditya08@live.com>
Tested-by: Samuel Jiang <chyishian.jiang@gmail.com>
Signed-off-by: Orlando Chamberlain <redecorating@protonmail.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
The uapi POSIX ACL struct passed through the value argument during
setxattr() contains {g,u}id values encoded via ACL_{GROUP,USER} entries
that should actually be stored in the form of k{g,u}id_t (See [1] for a
long explanation of the issue.).
In 0c5fd887d2 ("acl: move idmapped mount fixup into vfs_{g,s}etxattr()")
we took the mount's idmapping into account in order to let overlayfs
handle POSIX ACLs on idmapped layers correctly. The fixup is currently
performed directly in vfs_setxattr() which piles on top of the earlier
hackiness by handling the mount's idmapping and stuff the vfs{g,u}id_t
values into the uapi struct as well. While that is all correct and works
fine it's just ugly.
Now that we have introduced vfs_make_posix_acl() earlier move handling
idmapped mounts out of vfs_setxattr() and into the POSIX ACL handler
where it belongs.
Note that we also need to call vfs_make_posix_acl() for EVM which
interpretes POSIX ACLs during security_inode_setxattr(). Leave them a
longer comment for future reference.
All filesystems that support idmapped mounts via FS_ALLOW_IDMAP use the
standard POSIX ACL xattr handlers and are covered by this change. This
includes overlayfs which simply calls vfs_{g,s}etxattr().
The following filesystems use custom POSIX ACL xattr handlers: 9p, cifs,
ecryptfs, and ntfs3 (and overlayfs but we've covered that in the paragraph
above) and none of them support idmapped mounts yet.
Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org/ [1]
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Reviewed-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org>
Limit validating the hash algorithm to just security.ima xattr, not
the security.evm xattr or any of the protected EVM security xattrs,
nor posix acls.
Fixes: 50f742dd91 ("IMA: block writes of the security.ima xattr with unsupported algorithms")
Reported-by: Christian Brauner <brauner@kernel.org>
Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Pull integrity updates from Mimi Zohar:
"Aside from the one EVM cleanup patch, all the other changes are kexec
related.
On different architectures different keyrings are used to verify the
kexec'ed kernel image signature. Here are a number of preparatory
cleanup patches and the patches themselves for making the keyrings -
builtin_trusted_keyring, .machine, .secondary_trusted_keyring, and
.platform - consistent across the different architectures"
* tag 'integrity-v6.0' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity:
kexec, KEYS, s390: Make use of built-in and secondary keyring for signature verification
arm64: kexec_file: use more system keyrings to verify kernel image signature
kexec, KEYS: make the code in bzImage64_verify_sig generic
kexec: clean up arch_kexec_kernel_verify_sig
kexec: drop weak attribute from functions
kexec_file: drop weak attribute from functions
evm: Use IS_ENABLED to initialize .enabled
Pull x86 kdump updates from Borislav Petkov:
- Add the ability to pass early an RNG seed to the kernel from the boot
loader
- Add the ability to pass the IMA measurement of kernel and bootloader
to the kexec-ed kernel
* tag 'x86_kdump_for_v6.0_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/setup: Use rng seeds from setup_data
x86/kexec: Carry forward IMA measurement log on kexec
Pull fs idmapping updates from Christian Brauner:
"This introduces the new vfs{g,u}id_t types we agreed on. Similar to
k{g,u}id_t the new types are just simple wrapper structs around
regular {g,u}id_t types.
They allow to establish a type safety boundary in the VFS for idmapped
mounts preventing confusion betwen {g,u}ids mapped into an idmapped
mount and {g,u}ids mapped into the caller's or the filesystem's
idmapping.
An initial set of helpers is introduced that allows to operate on
vfs{g,u}id_t types. We will remove all references to non-type safe
idmapped mounts helpers in the very near future. The patches do
already exist.
This converts the core attribute changing codepaths which become
significantly easier to reason about because of this change.
Just a few highlights here as the patches give detailed overviews of
what is happening in the commit messages:
- The kernel internal struct iattr contains type safe vfs{g,u}id_t
values clearly communicating that these values have to take a given
mount's idmapping into account.
- The ownership values placed in struct iattr to change ownership are
identical for idmapped and non-idmapped mounts going forward. This
also allows to simplify stacking filesystems such as overlayfs that
change attributes In other words, they always represent the values.
- Instead of open coding checks for whether ownership changes have
been requested and an actual update of the inode is required we now
have small static inline wrappers that abstract this logic away
removing a lot of code duplication from individual filesystems that
all open-coded the same checks"
* tag 'fs.idmapped.vfsuid.v5.20' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
mnt_idmapping: align kernel doc and parameter order
mnt_idmapping: use new helpers in mapped_fs{g,u}id()
fs: port HAS_UNMAPPED_ID() to vfs{g,u}id_t
mnt_idmapping: return false when comparing two invalid ids
attr: fix kernel doc
attr: port attribute changes to new types
security: pass down mount idmapping to setattr hook
quota: port quota helpers mount ids
fs: port to iattr ownership update helpers
fs: introduce tiny iattr ownership update helpers
fs: use mount types in iattr
fs: add two type safe mapping helpers
mnt_idmapping: add vfs{g,u}id_t
The lockdown LSM is primarily used in conjunction with UEFI Secure Boot.
This LSM may also be used on machines without UEFI. It can also be
enabled when UEFI Secure Boot is disabled. One of lockdown's features
is to prevent kexec from loading untrusted kernels. Lockdown can be
enabled through a bootparam or after the kernel has booted through
securityfs.
If IMA appraisal is used with the "ima_appraise=log" boot param,
lockdown can be defeated with kexec on any machine when Secure Boot is
disabled or unavailable. IMA prevents setting "ima_appraise=log" from
the boot param when Secure Boot is enabled, but this does not cover
cases where lockdown is used without Secure Boot.
To defeat lockdown, boot without Secure Boot and add ima_appraise=log to
the kernel command line; then:
$ echo "integrity" > /sys/kernel/security/lockdown
$ echo "appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig" > \
/sys/kernel/security/ima/policy
$ kexec -ls unsigned-kernel
Add a call to verify ima appraisal is set to "enforce" whenever lockdown
is enabled. This fixes CVE-2022-21505.
Cc: stable@vger.kernel.org
Fixes: 29d3c1c8df ("kexec: Allow kexec_file() with appropriate IMA policy when locked down")
Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
Acked-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use IS_ENABLED(CONFIG_XXX) instead of #ifdef/#endif statements to
initialize .enabled, minor simplicity improvement.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
On failure to allocate the SHA1 tfm, IMA fails to initialize and exits
without freeing the ima_algo_array. Add the missing kfree() for
ima_algo_array to avoid the potential memory leak.
Signed-off-by: Jianglei Nie <niejianglei2021@163.com>
Fixes: 6d94809af6 ("ima: Allocate and initialize tfm for each PCR bank")
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Currently, an unsigned kernel could be kexec'ed when IMA arch specific
policy is configured unless lockdown is enabled. Enforce kernel
signature verification check in the kexec_file_load syscall when IMA
arch specific policy is configured.
Fixes: 99d5cadfde ("kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE")
Reported-and-suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Coiby Xu <coxu@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
When the ima-modsig is enabled, the rc passed to evm_verifyxattr() may be
negative, which may cause the integer overflow problem.
Fixes: 39b0709636 ("ima: Implement support for module-style appended signatures")
Signed-off-by: Huaxin Lu <luhuaxin1@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Although the violation digest in the IMA measurement list is always
zeroes, the size of the digest should be based on the hash algorithm.
Until recently the hash algorithm was hard coded to sha1. Fix the
violation digest size included in the IMA measurement list.
This is just a cosmetic change which should not affect attestation.
Reported-by: Stefan Berger <stefanb@linux.ibm.com>
Fixes: 09091c44cb ("ima: use IMA default hash algorithm for integrity violations")
Tested-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
On kexec file load, the Integrity Measurement Architecture (IMA)
subsystem may verify the IMA signature of the kernel and initramfs, and
measure it. The command line parameters passed to the kernel in the
kexec call may also be measured by IMA.
A remote attestation service can verify a TPM quote based on the TPM
event log, the IMA measurement list and the TPM PCR data. This can
be achieved only if the IMA measurement log is carried over from the
current kernel to the next kernel across the kexec call.
PowerPC and ARM64 both achieve this using device tree with a
"linux,ima-kexec-buffer" node. x86 platforms generally don't make use of
device tree, so use the setup_data mechanism to pass the IMA buffer to
the new kernel.
Signed-off-by: Jonathan McDowell <noodles@fb.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> # IMA function definitions
Link: https://lore.kernel.org/r/YmKyvlF3my1yWTvK@noodles-fedora-PC23Y6EG
Now that we introduced new infrastructure to increase the type safety
for filesystems supporting idmapped mounts port the first part of the
vfs over to them.
This ports the attribute changes codepaths to rely on the new better
helpers using a dedicated type.
Before this change we used to take a shortcut and place the actual
values that would be written to inode->i_{g,u}id into struct iattr. This
had the advantage that we moved idmappings mostly out of the picture
early on but it made reasoning about changes more difficult than it
should be.
The filesystem was never explicitly told that it dealt with an idmapped
mount. The transition to the value that needed to be stored in
inode->i_{g,u}id appeared way too early and increased the probability of
bugs in various codepaths.
We know place the same value in struct iattr no matter if this is an
idmapped mount or not. The vfs will only deal with type safe
vfs{g,u}id_t. This makes it massively safer to perform permission checks
as the type will tell us what checks we need to perform and what helpers
we need to use.
Fileystems raising FS_ALLOW_IDMAP can't simply write ia_vfs{g,u}id to
inode->i_{g,u}id since they are different types. Instead they need to
use the dedicated vfs{g,u}id_to_k{g,u}id() helpers that map the
vfs{g,u}id into the filesystem.
The other nice effect is that filesystems like overlayfs don't need to
care about idmappings explicitly anymore and can simply set up struct
iattr accordingly directly.
Link: https://lore.kernel.org/lkml/CAHk-=win6+ahs1EwLkcq8apqLi_1wXFWbrPf340zYEhObpz4jA@mail.gmail.com [1]
Link: https://lore.kernel.org/r/20220621141454.2914719-9-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Before this change we used to take a shortcut and place the actual
values that would be written to inode->i_{g,u}id into struct iattr. This
had the advantage that we moved idmappings mostly out of the picture
early on but it made reasoning about changes more difficult than it
should be.
The filesystem was never explicitly told that it dealt with an idmapped
mount. The transition to the value that needed to be stored in
inode->i_{g,u}id appeared way too early and increased the probability of
bugs in various codepaths.
We know place the same value in struct iattr no matter if this is an
idmapped mount or not. The vfs will only deal with type safe
vfs{g,u}id_t. This makes it massively safer to perform permission checks
as the type will tell us what checks we need to perform and what helpers
we need to use.
Adapt the security_inode_setattr() helper to pass down the mount's
idmapping to account for that change.
Link: https://lore.kernel.org/r/20220621141454.2914719-8-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Earlier we introduced new helpers to abstract ownership update and
remove code duplication. This converts all filesystems supporting
idmapped mounts to make use of these new helpers.
For now we always pass the initial idmapping which makes the idmapping
functions these helpers call nops.
This is done because we currently always pass the actual value to be
written to i_{g,u}id via struct iattr. While this allowed us to treat
the {g,u}id values in struct iattr as values that can be directly
written to inode->i_{g,u}id it also increases the potential for
confusion for filesystems.
Now that we are have dedicated types to prevent this confusion we will
ultimately only map the value from the idmapped mount into a filesystem
value that can be written to inode->i_{g,u}id when the filesystem
actually updates the inode. So pass down the initial idmapping until we
finished that conversion at which point we pass down the mount's
idmapping.
No functional changes intended.
Link: https://lore.kernel.org/r/20220621141454.2914719-6-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
This reverts commit ccf11dbaa0.
Commit ccf11dbaa0 ("evm: Fix memleak in init_desc") said there is
memleak in init_desc. That may be incorrect, as we can see, tmp_tfm is
saved in one of the two global variables hmac_tfm or evm_tfm[hash_algo],
then if init_desc is called next time, there is no need to alloc tfm
again, so in the error path of kmalloc desc or crypto_shash_init(desc),
It is not a problem without freeing tmp_tfm.
And also that commit did not reset the global variable to NULL after
freeing tmp_tfm and this makes *tfm a dangling pointer which may cause a
UAF issue.
Reported-by: Guozihua (Scott) <guozihua@huawei.com>
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Pull IMA updates from Mimi Zohar:
"New is IMA support for including fs-verity file digests and signatures
in the IMA measurement list as well as verifying the fs-verity file
digest based signatures, both based on policy.
In addition, are two bug fixes:
- avoid reading UEFI variables, which cause a page fault, on Apple
Macs with T2 chips.
- remove the original "ima" template Kconfig option to address a boot
command line ordering issue.
The rest is a mixture of code/documentation cleanup"
* tag 'integrity-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity:
integrity: Fix sparse warnings in keyring_handler
evm: Clean up some variables
evm: Return INTEGRITY_PASS for enum integrity_status value '0'
efi: Do not import certificates from UEFI Secure Boot for T2 Macs
fsverity: update the documentation
ima: support fs-verity file digest based version 3 signatures
ima: permit fsverity's file digests in the IMA measurement list
ima: define a new template field named 'd-ngv2' and templates
fs-verity: define a function to return the integrity protected file digest
ima: use IMA default hash algorithm for integrity violations
ima: fix 'd-ng' comments and documentation
ima: remove the IMA_TEMPLATE Kconfig option
ima: remove redundant initialization of pointer 'file'.
Fix the following sparse warnings:
CHECK security/integrity/platform_certs/keyring_handler.c
security/integrity/platform_certs/keyring_handler.c:76:16: warning: Using plain integer as NULL pointer
security/integrity/platform_certs/keyring_handler.c:91:16: warning: Using plain integer as NULL pointer
security/integrity/platform_certs/keyring_handler.c:106:16: warning: Using plain integer as NULL pointer
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Make hmac_tfm static since it's not used anywhere else besides the file
it is in.
Remove declaration of hash_tfm since it doesn't exist.
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Return INTEGRITY_PASS for the enum integrity_status rather than 0.
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
On Apple T2 Macs, when Linux attempts to read the db and dbx efi variables
at early boot to load UEFI Secure Boot certificates, a page fault occurs
in Apple firmware code and EFI runtime services are disabled with the
following logs:
[Firmware Bug]: Page fault caused by firmware at PA: 0xffffb1edc0068000
WARNING: CPU: 3 PID: 104 at arch/x86/platform/efi/quirks.c:735 efi_crash_gracefully_on_page_fault+0x50/0xf0
(Removed some logs from here)
Call Trace:
<TASK>
page_fault_oops+0x4f/0x2c0
? search_bpf_extables+0x6b/0x80
? search_module_extables+0x50/0x80
? search_exception_tables+0x5b/0x60
kernelmode_fixup_or_oops+0x9e/0x110
__bad_area_nosemaphore+0x155/0x190
bad_area_nosemaphore+0x16/0x20
do_kern_addr_fault+0x8c/0xa0
exc_page_fault+0xd8/0x180
asm_exc_page_fault+0x1e/0x30
(Removed some logs from here)
? __efi_call+0x28/0x30
? switch_mm+0x20/0x30
? efi_call_rts+0x19a/0x8e0
? process_one_work+0x222/0x3f0
? worker_thread+0x4a/0x3d0
? kthread+0x17a/0x1a0
? process_one_work+0x3f0/0x3f0
? set_kthread_struct+0x40/0x40
? ret_from_fork+0x22/0x30
</TASK>
---[ end trace 1f82023595a5927f ]---
efi: Froze efi_rts_wq and disabled EFI Runtime Services
integrity: Couldn't get size: 0x8000000000000015
integrity: MODSIGN: Couldn't get UEFI db list
efi: EFI Runtime Services are disabled!
integrity: Couldn't get size: 0x8000000000000015
integrity: Couldn't get UEFI dbx list
integrity: Couldn't get size: 0x8000000000000015
integrity: Couldn't get mokx list
integrity: Couldn't get size: 0x80000000
So we avoid reading these UEFI variables and thus prevent the crash.
Cc: stable@vger.kernel.org
Signed-off-by: Aditya Garg <gargaditya08@live.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
IMA may verify a file's integrity against a "good" value stored in the
'security.ima' xattr or as an appended signature, based on policy. When
the "good value" is stored in the xattr, the xattr may contain a file
hash or signature. In either case, the "good" value is preceded by a
header. The first byte of the xattr header indicates the type of data
- hash, signature - stored in the xattr. To support storing fs-verity
signatures in the 'security.ima' xattr requires further differentiating
the fs-verity signature from the existing IMA signature.
In addition the signatures stored in 'security.ima' xattr, need to be
disambiguated. Instead of directly signing the fs-verity digest, a new
signature format version 3 is defined as the hash of the ima_file_id
structure, which identifies the type of signature and the digest.
The IMA policy defines "which" files are to be measured, verified, and/or
audited. For those files being verified, the policy rules indicate "how"
the file should be verified. For example to require a file be signed,
the appraise policy rule must include the 'appraise_type' option.
appraise_type:= [imasig] | [imasig|modsig] | [sigv3]
where 'imasig' is the original or signature format v2 (default),
where 'modsig' is an appended signature,
where 'sigv3' is the signature format v3.
The policy rule must also indicate the type of digest, if not the IMA
default, by first specifying the digest type:
digest_type:= [verity]
The following policy rule requires fsverity signatures. The rule may be
constrained, for example based on a fsuuid or LSM label.
appraise func=BPRM_CHECK digest_type=verity appraise_type=sigv3
Acked-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
