Messages in this thread | | | Subject | Re: [PATCH 0/2] support to read and tune appraise mode in runtime | From | Tianjia Zhang <> | Date | Tue, 14 Apr 2020 11:36:20 +0800 |
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On 2020/4/14 5:55, Mimi Zohar wrote: > On Thu, 2020-04-09 at 11:39 +0800, Tianjia Zhang wrote: >> Support the read and write operations of ima_appraise by adding a >> securifyfs file 'appraise_mode'. >> >> In order to tune appraise mode in runtime, writing a PKCS#7 signature >> corresponding the signed content is required. The content should be off, >> enforce, log or fix. Given a simple way to archive this: >> >> $ echo -n off > mode >> $ openssl smime -sign -nocerts -noattr -binary \ >> -in mode -inkey <system_trusted_key> \ >> -signer <cert> -outform der -out mode.p7s >> $ sudo cat mode.p7s \ >> > /sys/kernel/security/ima/appraise_mode >> >> Note that the signing key must be a trust key located in >> system trusted keyring. So even the root privilege cannot >> simply disable the enforcement. > > There are major problems with disabling IMA appraisal. This patch set > proposes disabling IMA appraisal without even providing the motivation > for such support. > > A lot of effort went into preventing custom IMA policies from > disabling appraising the kexec or kernel module signatures. In > addition, the "lockdown" patch set was upstreamed permitting IMA > signature verification. This patch set would break both of these > features. > > IMA relies on its own keyring for verifying file signatures, not the > builtin or secondary trusted kernel keyrings. > > Two methods already exist - xattr and appended signatures - for > verifying file signatures. This patch set assumes creating and > signing a file, which is then written to a securityfs file. Like for > loading a custom IMA policy, instead of cat'ing the file, write the > pathname to the securityfs file. > > If you must define a new IMA method for verifying file signatures, > then it needs to be generic and added to ima_appraise_measurement(). > (Refer to the new IMA appended signature support.) > > Mimi > >> >> Tianjia Zhang (2): >> ima: support to read appraise mode >> ima: support to tune appraise mode in runtime >> >> security/integrity/ima/ima_fs.c | 134 +++++++++++++++++++++++++++++++- >> 1 file changed, 133 insertions(+), 1 deletion(-) >>
Thanks for your suggestion, the way to close the appraise mode here is indeed a bit rude, I will reconsider again according to your suggestions.
In addition, [PATCH 1/2] ima: support to read appraise mode, by the way, see if this patch is acceptable.
Thanks and best, Tianjia
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