On Thu, 2019-10-31 at 03:31:32 UTC, Mimi Zohar wrote: > From: Nayna Jain <nayna@xxxxxxxxxxxxx> > > Asymmetric private keys are used to sign multiple files. The kernel > currently supports checking against blacklisted keys. However, if the > public key is blacklisted, any file signed by the blacklisted key will > automatically fail signature verification. Blacklisting the public > key is not fine enough granularity, as we might want to only blacklist > a particular file. > > This patch adds support for checking against the blacklisted hash of > the file, without the appended signature, based on the IMA policy. It > defines a new policy option "appraise_flag=check_blacklist". > > In addition to the blacklisted binary hashes stored in the firmware "dbx" > variable, the Linux kernel may be configured to load blacklisted binary > hashes onto the .blacklist keyring as well. The following example shows > how to blacklist a specific kernel module hash. > > $ sha256sum kernel/kheaders.ko > 77fa889b35a05338ec52e51591c1b89d4c8d1c99a21251d7c22b1a8642a6bad3 > kernel/kheaders.ko > > $ grep BLACKLIST .config > CONFIG_SYSTEM_BLACKLIST_KEYRING=y > CONFIG_SYSTEM_BLACKLIST_HASH_LIST="blacklist-hash-list" > > $ cat certs/blacklist-hash-list > "bin:77fa889b35a05338ec52e51591c1b89d4c8d1c99a21251d7c22b1a8642a6bad3" > > Update the IMA custom measurement and appraisal policy rules > (/etc/ima-policy): > > measure func=MODULE_CHECK template=ima-modsig > appraise func=MODULE_CHECK appraise_flag=check_blacklist > appraise_type=imasig|modsig > > After building, installing, and rebooting the kernel: > > 545660333 ---lswrv 0 0 \_ blacklist: > bin:77fa889b35a05338ec52e51591c1b89d4c8d1c99a21251d7c22b1a8642a6bad3 > > measure func=MODULE_CHECK template=ima-modsig > appraise func=MODULE_CHECK appraise_flag=check_blacklist > appraise_type=imasig|modsig > > modprobe: ERROR: could not insert 'kheaders': Permission denied > > 10 0c9834db5a0182c1fb0cdc5d3adcf11a11fd83dd ima-sig > sha256:3bc6ed4f0b4d6e31bc1dbc9ef844605abc7afdc6d81a57d77a1ec9407997c40 > 2 /usr/lib/modules/5.4.0-rc3+/kernel/kernel/kheaders.ko > > 10 82aad2bcc3fa8ed94762356b5c14838f3bcfa6a0 ima-modsig > sha256:3bc6ed4f0b4d6e31bc1dbc9ef844605abc7afdc6d81a57d77a1ec9407997c40 > 2 /usr/lib/modules/5.4.0rc3+/kernel/kernel/kheaders.ko sha256:77fa889b3 > 5a05338ec52e51591c1b89d4c8d1c99a21251d7c22b1a8642a6bad3 > 3082029a06092a864886f70d010702a082028b30820287020101310d300b0609608648 > 016503040201300b06092a864886f70d01070131820264.... > > 10 25b72217cc1152b44b134ce2cd68f12dfb71acb3 ima-buf > sha256:8b58427fedcf8f4b20bc8dc007f2e232bf7285d7b93a66476321f9c2a3aa132 > b blacklisted-hash > 77fa889b35a05338ec52e51591c1b89d4c8d1c99a21251d7c22b1a8642a6bad3 > > Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxx> > Cc: Jessica Yu <jeyu@xxxxxxxxxx> > Cc: David Howells <dhowells@xxxxxxxxxx> > [zohar@xxxxxxxxxxxxx: updated patch description] > Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx> Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/273df864cf7466fb170b8dcc1abd672cd08ad8d3 cheers
