Re: [PATCH] audit: add containerid support for IMA-audit

On 2018-05-18 07:49, Stefan Berger wrote: > On 05/17/2018 05:30 PM, Richard Guy Briggs wrote: >> On 2018-05-17 10:18, Stefan Berger wrote: >>> On 03/08/2018 06:21 AM, Richard Guy Briggs wrote: >>>> On 2018-03-05 09:24, Mimi Zohar wrote: >>>>> On Mon, 2018-03-05 at 08:50 -0500, Richard Guy Briggs wrote: >>>>>> On 2018-03-05 08:43, Mimi Zohar wrote: >>>>>>> Hi Richard, >>>>>>> >>>>>>> This patch has been compiled, but not runtime tested. >>>>>> Ok, great, thank you. I assume you are offering this patch to be >>>>>> included in this patchset? >>>>> Yes, thank you. >>>>> >>>>>> I'll have a look to see where it fits in the >>>>>> IMA record. It might be better if it were an AUDIT_CONTAINER_INFO >>>>>> auxiliary record, but I'll have a look at the circumstances of the >>>>>> event. >>>> I had a look at the context of this record to see if adding the contid >>>> field to it made sense. I think the only records for which the contid >>>> field makes sense are the two newly proposed records, AUDIT_CONTAINER >>>> which introduces the container ID and the and AUDIT_CONTAINER_INFO which >>>> documents the presence of the container ID in a process event (or >>>> process-less network event). All others should use the auxiliary record >>>> AUDIT_CONTAINER_INFO rather than include the contid field directly >>>> itself. There are several reasons for this including record length, the >>>> ability to filter unwanted records, the difficulty of changing the order >>>> of or removing fields in the future. >>>> >>>> Syscalls get this information automatically if the container ID is set >>>> for a task via the AUDIT_CONTAINER_INFO auxiliary record. Generally a >>>> syscall event is one that uses the task's audit_context while a >>>> standalone event uses NULL or builds a local audit_context that is >>>> discarded immediately after the local use. >>>> >>>> Looking at the two cases of AUDIT_INTEGRITY_RULE record generation, it >>>> appears that they should be split into two distinct audit record types. >>>> >>>> The record created in ima_audit_measurement() is a syscall record that >>>> could possibly stand on its own since the subject attributes are >>>> present. If it remains a syscall auxiliary record it will automatically >>>> have the AUDIT_CONTAINER_INFO record accompany it anyways. If it is >>>> decided to detach it (which would save cpu/netlink/disk bandwidth but is >>>> not recommended due to not wanting to throw away any other syscall >>>> information or other involved records (PATH, CWD, etc...) then a local >>>> audit_context would be created for the AUDIT_INTEGRITY_RULE and >>>> AUDIT_CONTAINERID_INFO records only and immediately discarded. >>> What does 'detach it' mean? Does it mean we're not using >>> current->audit_context? >> Exactly. >> >>>> The record created in ima_parse_rule() is not currently a syscall record >>>> since it is passed an audit_context of NULL and it has a very different >>>> format that does not include any subject attributes (except subj_*=). >>>> At first glance it appears this one should be a syscall accompanied >>>> auxiliary record. Either way it should have an AUDIT_CONTAINER_INFO >>> Do you have an example (pointer) to the format for a 'syscall accompanied >>> auxiliary record'? >> Any that uses current->audit_context (or recently proposed >> audit_context() function) will be a syscall auxiliary record. Well >> formed record formats are <fieldname>=<value> and named as listed: >> >> https://github.com/linux-audit/audit-documentation/wiki/SPEC-Writing-Good... >> https://github.com/linux-audit/audit-documentation/blob/master/specs/fiel... >> >>>> auxiliary record either by being converted to a syscall auxiliary record >>>> by using current->audit_context rather than NULL when calling >>>> audit_log_start(), or creating a local audit_context and calling >>> ima_parse_rule() is invoked when setting a policy by writing it into >>> /sys/kernel/security/ima/policy. We unfortunately don't have the >>> current->audit_context in this case. >> Sure you do. What process writes to that file? That's the one we care >> about, unless it is somehow handed off to a queue and processed later in >> a different context. > I just printk'd it again. current->audit_context is NULL in this case. Oops, that sounds like some of the netfilter empty table initializations, whereas usually rules have a user actor.

>>>> audit_log_container_info() then releasing the local context. This >>>> version of the record has additional concerns covered here: >>>> https://github.com/linux-audit/audit-kernel/issues/52 >>> Following the discussion there and the concern with breaking user space, how >>> can we split up the AUDIT_INTEGRITY_RULE that is used in >>> ima_audit_measurement() and ima_parse_rule(), without 'breaking user space'? >> Arguably userspace is already broken by this wildly diverging pair of >> formats for the same record. >> >>> A message produced by ima_parse_rule() looks like this here: >>> >>> type=INTEGRITY_RULE msg=audit(1526566213.870:305): action="dont_measure" >>> fsmagic="0x9fa0" res=1 >>> >>> in contrast to that an INTEGRITY_PCR record type: >>> >>> type=INTEGRITY_PCR msg=audit(1526566235.193:334): pid=1615 uid=0 auid=0 >>> ses=2 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 >>> op="invalid_pcr" cause="open_writers" comm="scp" >>> name="/var/log/audit/audit.log" dev="dm-0" ino=1962625 res=1 >>> >>> Should some of the fields from INTEGRITY_PCR also appear in INTEGRITY_RULE? >> Not necessarily. There are a number of records in the PCR record that >> would be redundant when connected to a syscall record, but removing them >> is discouraged to avoid breaking parsers that expect them. >> >> I don't see any need to touch the PCR record. > I wasn't going to touch the PCR record. > > >>> If so, which ones? We could probably refactor the current >>> integrity_audit_message() and have ima_parse_rule() call into it to get >>> those fields as well. I suppose adding new fields to it wouldn't be >>> considered breaking user space? >> Changing the order of existing fields or inserting fields could break >> stuff and is strongly discouraged without a good reason, but appending >> fields is usually the right way to add information. >> >> There are exceptions, and in this case, I'd pick the "more standard" of >> the formats for AUDIT_INTEGRITY_RULE (ima_audit_measurement?) and stick >> with that, abandoning the other format, renaming the less standard >> version of the record (ima_parse_rule?) and perhpas adopting that >> abandonned format for the new record type while using >> current->audit_context. > Since current->audit_context is NULL I built on your patch, but I am not > sure whether it is justifyable to use that before your container id series > is applied. > > This is what ima_parse_rule() produces now after having it call > audit_log_task_info() as well and by introducing 1806 for ima_parse_rule() > only ( https://lkml.org/lkml/2018/5/11/386 ): > > type=UNKNOWN[1806] msg=audit(1526643702.328:304): action="dont_measure" > fsmagic="0x9fa0" res=1 ppid=1563 pid=1595 auid=0 uid=0 gid=0 euid=0 suid=0 > fsuid=0 egid=0 sgid=0 fsgid=0 tty=tty2 ses=2 comm="cat" exe="/usr/bin/cat" > subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 > > [before: type=INTEGRITY_RULE msg=audit(1526566213.870:305): > action="dont_measure" fsmagic="0x9fa0" res=1] Since this appears to be a a user action, use current->audit_context to make it a syscall auxiliary record rather than adding all these redundant fields.

> For comparison the INTEGRITY_RULE: > > type=INTEGRITY_RULE msg=audit(1526642504.074:331): file="/usr/bin/ssh" hash="sha256:4abc2558424b9ca61c34af43169d9b9e174d7825bf60c9c76be377549081db5b" > ppid=1623 pid=1624 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 > fsgid=0 tty=tty2 ses=2 comm="scp" exe="/usr/bin/scp" > subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 > > > 1806 would be in sync with INTEGRITY_RULE now for process related info. If > this looks good, I'll remove the dependency on your local context creation > and post the series. What would be the macro name for 1806?

> The justification for the change is that the INTEGRITY_RULE, as produced by > ima_parse_rule(), is broken. > >     Stefan > > >> Does this help? >> >>>     Stefan >>> >>>> Can you briefly describe the circumstances under which these two >>>> different identically-numbered records are produced as a first step >>>> towards splitting them into two distict records? >>>> >>>> The four AUDIT_INTEGRITY _METADATA, _PCR, _DATA and _STATUS records >>>> appear to be already properly covered for AUDIT_CONTAINER_INFO records >>>> by being syscall auxiliary records. The AUDIT_INTEGRITY_HASH record >>>> appears to be unused. >>>> >>>>>> Can you suggest a procedure to test it? >>>>> Like IMA-measurement and IMA-appraisal, IMA-audit is enabled based on >>>>> policy. The example IMA policy, below, includes IMA-audit messages for >>>>> files executed. 'cat' the policy to /sys/kernel/security/ima/policy. >>>>> >>>>> /etc/ima/ima-policy: >>>>> audit func=BPRM_CHECK >>>>> >>>>> There's a FireEye blog titled "Extending Linux Executable Logging With >>>>> The Integrity Measurement Architecture"* that explains how to augment >>>>> their existing system security analytics with file hashes. >>>>> >>>>> * https://www.fireeye.com/blog/threat-research/2016/11/extending_linux >>>>> _exec.html >>>>> >>>>> >>>>> Mimi >>>>> >>>>>>> If the containerid is defined, include it in the IMA-audit record. >>>>>>> >>>>>>> Signed-off-by: Mimi Zohar <zohar(a)linux.vnet.ibm.com&gt; >>>>>>> --- >>>>>>> security/integrity/ima/ima_api.c | 3 +++ >>>>>>> 1 file changed, 3 insertions(+) >>>>>>> >>>>>>> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c >>>>>>> index 33b4458cdbef..41d29a06f28f 100644 >>>>>>> --- a/security/integrity/ima/ima_api.c >>>>>>> +++ b/security/integrity/ima/ima_api.c >>>>>>> @@ -335,6 +335,9 @@ void ima_audit_measurement(struct integrity_iint_cache *iint, >>>>>>> audit_log_untrustedstring(ab, algo_hash); >>>>>>> audit_log_task_info(ab, current); >>>>>>> + if (audit_containerid_set(current)) >>>>>>> + audit_log_format(ab, " contid=%llu", >>>>>>> + audit_get_containerid(current)); >>>>>>> audit_log_end(ab); >>>>>>> iint->flags |= IMA_AUDITED; >>>>>>> -- >>>>>>> 2.7.5 >>>>>>> >>>>>> - RGB >>>> - RGB >>>> >>>> -- >>>> Richard Guy Briggs <rgb(a)redhat.com&gt; >>>> Sr. S/W Engineer, Kernel Security, Base Operating Systems >>>> Remote, Ottawa, Red Hat Canada >>>> IRC: rgb, SunRaycer >>>> Voice: +1.647.777.2635, Internal: (81) 32635 >>>> >> - RGB >> >> -- >> Richard Guy Briggs <rgb(a)redhat.com&gt; >> Sr. S/W Engineer, Kernel Security, Base Operating Systems >> Remote, Ottawa, Red Hat Canada >> IRC: rgb, SunRaycer >> Voice: +1.647.777.2635, Internal: (81) 32635 >> - RGB -- Richard Guy Briggs <rgb(a)redhat.com&gt; Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada IRC: rgb, SunRaycer Voice: +1.647.777.2635, Internal: (81) 32635