* Adding support for MAC_TASK_CONTEXTS and MAC_OBJ_CONTEXTS to userspace. [not found] <e252b332-1a32-2103-f299-d0376b8a4615.ref@schaufler-ca.com> @ 2021-06-14 19:34 ` Casey Schaufler 2021-06-14 21:13 ` Steve Grubb 0 siblings, 1 reply; 4+ messages in thread From: Casey Schaufler @ 2021-06-14 19:34 UTC (permalink / raw) To: Steve Grubb; +Cc: linux-audit I'm looking at the audit userspace implications of adding two new kernel audit records. AUDIT_MAC_TASK_CONTEXTS and AUDIT_MAC_OBJ_CONTEXTS are used when there are multiple security modules with a "security context" active on the system. This design has been discussed here at length. The records will look like: AUDIT_MAC_TASK_CONTEXTS subj_<lsmname>=value subj_<lsmname>=value ... Looking at the audit user-space code I see several things that have me concerned. The first is the use of WITH_APPARMOR. Going forward what behavior would we want if subj_apparmor=something shows up on a system that has not got WITH_APPARMOR defined? The code is inconsistent in that it does not use WITH_SELINUX, but that's hardly a surprise given its origins. There is also no WITH_SMACK, but that's unlikely to be an issue since Smack's use of audit is very much like SELinux's. The question is what to do about filtering when subj=foo is specified. I suggest that if any of subj_selinux, subj_smack or subj_something is "foo", it is a match. But the SELinux components of a label (level, user, ...) are also available for filtering. If someone wrote a simple Bell & LaPadula LSM filtering by some of those fields could be useful there, too. I would like guidance on whether I ought to go the route of more extensive use of WITH_APPARMOR (and WITH_SMACK, WITH_MUMBLE) or take the path of greater generalization. Or, whether I should treat each case individually and give it my best whack. Thank you. -- Linux-audit mailing list Linux-audit@redhat.com https://listman.redhat.com/mailman/listinfo/linux-audit ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Adding support for MAC_TASK_CONTEXTS and MAC_OBJ_CONTEXTS to userspace. 2021-06-14 19:34 ` Adding support for MAC_TASK_CONTEXTS and MAC_OBJ_CONTEXTS to userspace Casey Schaufler @ 2021-06-14 21:13 ` Steve Grubb 2021-06-15 17:01 ` Casey Schaufler 0 siblings, 1 reply; 4+ messages in thread From: Steve Grubb @ 2021-06-14 21:13 UTC (permalink / raw) To: Casey Schaufler; +Cc: linux-audit Hello, On Monday, June 14, 2021 3:34:33 PM EDT Casey Schaufler wrote: > I'm looking at the audit userspace implications of adding two > new kernel audit records. AUDIT_MAC_TASK_CONTEXTS and > AUDIT_MAC_OBJ_CONTEXTS are used when there are multiple security > modules with a "security context" active on the system. This > design has been discussed here at length. The records will look > like: > > AUDIT_MAC_TASK_CONTEXTS > subj_<lsmname>=value > subj_<lsmname>=value > ... > > Looking at the audit user-space code I see several things > that have me concerned. The first is the use of WITH_APPARMOR. > Going forward what behavior would we want if subj_apparmor=something > shows up on a system that has not got WITH_APPARMOR defined? I think it should be ignored. > The code is inconsistent in that it does not use WITH_SELINUX, > but that's hardly a surprise given its origins. There is also no > WITH_SMACK, but that's unlikely to be an issue since Smack's use > of audit is very much like SELinux's. We can add those WITH_* if you like. > The question is what to > do about filtering when subj=foo is specified. I suggest that if > any of subj_selinux, subj_smack or subj_something is "foo", it is > a match. I think that's how we already treat things. There is a linked list for AVC's and we match on any of. > But the SELinux components of a label (level, user, ...) > are also available for filtering. If someone wrote a simple Bell & > LaPadula LSM filtering by some of those fields could be useful > there, too. > > I would like guidance on whether I ought to go the route of > more extensive use of WITH_APPARMOR (and WITH_SMACK, WITH_MUMBLE) > or take the path of greater generalization. Or, whether I should > treat each case individually and give it my best whack. To be honest, I have no idea how well the audit system works with any MAC system except SE Linux. I don't really know if its doing the right thing. Ausearch and report share a parser. It is time sensitive. I usually test it on 4 or 5 Gb of logs. We also have the ausearch-test program which can be used to test any changes to the parser. http://people.redhat.com/sgrubb/audit/ausearch-test-0.6.tar.gz Once that is squared away, there is the auparse library. It has a table that classifies a field name into what it is for interpretation purposes. You will find a #ifdef WITH_APPARMOR. I don't know if that table is complete or if it needs to be extended for any other MAC system. That then leads to the auparse normalizer. I don't know if we need to make any changes there. You can trigger its code with ausearch --format csv or -- format text. Also, we have some size limits in user space. How big can an event record be if the file is MAX_PATH name length and it has a space in its name or directory and each context is it's maximum size? We may need to think about how this might change the whole userspace ecosystem's size definition, MAX_AUDIT_MESSAGE_LENGTH, since this is part of the ABI. And the kernel also has AUDIT_MESSAGE_TEXT_MAX. What would you get with: # /usr/sbin/auditctl -m `perl -e 'print "A"x8880'` And last...what about auditctl? Is the syscall filter going to allow filtering on these other subject/object components? -Steve -- Linux-audit mailing list Linux-audit@redhat.com https://listman.redhat.com/mailman/listinfo/linux-audit ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Adding support for MAC_TASK_CONTEXTS and MAC_OBJ_CONTEXTS to userspace. 2021-06-14 21:13 ` Steve Grubb @ 2021-06-15 17:01 ` Casey Schaufler 2021-06-15 21:15 ` Steve Grubb 0 siblings, 1 reply; 4+ messages in thread From: Casey Schaufler @ 2021-06-15 17:01 UTC (permalink / raw) To: Steve Grubb; +Cc: linux-audit On 6/14/2021 2:13 PM, Steve Grubb wrote: > Hello, > > On Monday, June 14, 2021 3:34:33 PM EDT Casey Schaufler wrote: >> I'm looking at the audit userspace implications of adding two >> new kernel audit records. AUDIT_MAC_TASK_CONTEXTS and >> AUDIT_MAC_OBJ_CONTEXTS are used when there are multiple security >> modules with a "security context" active on the system. This >> design has been discussed here at length. The records will look >> like: >> >> AUDIT_MAC_TASK_CONTEXTS >> subj_<lsmname>=value >> subj_<lsmname>=value >> ... >> >> Looking at the audit user-space code I see several things >> that have me concerned. The first is the use of WITH_APPARMOR. >> Going forward what behavior would we want if subj_apparmor=something >> shows up on a system that has not got WITH_APPARMOR defined? > I think it should be ignored. > >> The code is inconsistent in that it does not use WITH_SELINUX, >> but that's hardly a surprise given its origins. There is also no >> WITH_SMACK, but that's unlikely to be an issue since Smack's use >> of audit is very much like SELinux's. > We can add those WITH_* if you like. > >> The question is what to >> do about filtering when subj=foo is specified. I suggest that if >> any of subj_selinux, subj_smack or subj_something is "foo", it is >> a match. > I think that's how we already treat things. There is a linked list for AVC's > and we match on any of. > >> But the SELinux components of a label (level, user, ...) >> are also available for filtering. If someone wrote a simple Bell & >> LaPadula LSM filtering by some of those fields could be useful >> there, too. >> >> I would like guidance on whether I ought to go the route of >> more extensive use of WITH_APPARMOR (and WITH_SMACK, WITH_MUMBLE) >> or take the path of greater generalization. Or, whether I should >> treat each case individually and give it my best whack. > To be honest, I have no idea how well the audit system works with any MAC > system except SE Linux. Understood. Part of what I'm looking at is ensuring that as multiple concurrent LSMs come in that the audit user-space isn't mucked up. ausearch has these options: -o,--object <SE Linux Object context> -se,--context <SE Linux context> -su,--subject <SE Linux context> Without multiple LSMs we can easily ignore "SE Linux" in these options and use whatever kind of "context" is available. If I have SELinux and AppArmor, the implication is that you can't search on AppArmor information. Should we be adding -aa,--apparmorcontext <AppArmor context> -as,--apparmorsubject <AppArmor subject context> or should we change -se to look at all "contexts", and change the description to reflect that? Basicaly, I'm asking whether you'd rather add options for other LSMs or remove descriptions that specify SELinux. > I don't really know if its doing the right thing. > Ausearch and report share a parser. It is time sensitive. I usually test it > on 4 or 5 Gb of logs. We also have the ausearch-test program which can be > used to test any changes to the parser. > > http://people.redhat.com/sgrubb/audit/ausearch-test-0.6.tar.gz > > Once that is squared away, there is the auparse library. It has a table that > classifies a field name into what it is for interpretation purposes. You will > find a #ifdef WITH_APPARMOR. I don't know if that table is complete or if it > needs to be extended for any other MAC system. > > That then leads to the auparse normalizer. I don't know if we need to make > any changes there. You can trigger its code with ausearch --format csv or -- > format text. > > Also, we have some size limits in user space. How big can an event record be > if the file is MAX_PATH name length and it has a space in its name or > directory and each context is it's maximum size? We may need to think about > how this might change the whole userspace ecosystem's size definition, > MAX_AUDIT_MESSAGE_LENGTH, since this is part of the ABI. And the kernel also > has AUDIT_MESSAGE_TEXT_MAX. What would you get with: > > # /usr/sbin/auditctl -m `perl -e 'print "A"x8880'` > > And last...what about auditctl? Is the syscall filter going to allow filtering > on these other subject/object components? > > -Steve > > -- Linux-audit mailing list Linux-audit@redhat.com https://listman.redhat.com/mailman/listinfo/linux-audit ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Adding support for MAC_TASK_CONTEXTS and MAC_OBJ_CONTEXTS to userspace. 2021-06-15 17:01 ` Casey Schaufler @ 2021-06-15 21:15 ` Steve Grubb 0 siblings, 0 replies; 4+ messages in thread From: Steve Grubb @ 2021-06-15 21:15 UTC (permalink / raw) To: Casey Schaufler; +Cc: linux-audit On Tuesday, June 15, 2021 1:01:18 PM EDT Casey Schaufler wrote: > On 6/14/2021 2:13 PM, Steve Grubb wrote: > > Hello, > > > > On Monday, June 14, 2021 3:34:33 PM EDT Casey Schaufler wrote: > >> I'm looking at the audit userspace implications of adding two > >> new kernel audit records. AUDIT_MAC_TASK_CONTEXTS and > >> AUDIT_MAC_OBJ_CONTEXTS are used when there are multiple security > >> modules with a "security context" active on the system. This > >> design has been discussed here at length. The records will look > >> > >> like: > >> AUDIT_MAC_TASK_CONTEXTS > >> subj_<lsmname>=value > >> subj_<lsmname>=value > >> ... > >> > >> Looking at the audit user-space code I see several things > >> that have me concerned. The first is the use of WITH_APPARMOR. > >> Going forward what behavior would we want if subj_apparmor=something > >> shows up on a system that has not got WITH_APPARMOR defined? > > > > I think it should be ignored. > > > >> The code is inconsistent in that it does not use WITH_SELINUX, > >> but that's hardly a surprise given its origins. There is also no > >> WITH_SMACK, but that's unlikely to be an issue since Smack's use > >> of audit is very much like SELinux's. > > > > We can add those WITH_* if you like. > > > >> The question is what to > >> do about filtering when subj=foo is specified. I suggest that if > >> any of subj_selinux, subj_smack or subj_something is "foo", it is > >> a match. > > > > I think that's how we already treat things. There is a linked list for > > AVC's and we match on any of. > > > >> But the SELinux components of a label (level, user, ...) > >> are also available for filtering. If someone wrote a simple Bell & > >> LaPadula LSM filtering by some of those fields could be useful > >> there, too. > >> > >> I would like guidance on whether I ought to go the route of > >> more extensive use of WITH_APPARMOR (and WITH_SMACK, WITH_MUMBLE) > >> or take the path of greater generalization. Or, whether I should > >> treat each case individually and give it my best whack. > > > > To be honest, I have no idea how well the audit system works with any MAC > > system except SE Linux. > > Understood. Part of what I'm looking at is ensuring that as multiple > concurrent LSMs come in that the audit user-space isn't mucked up. > ausearch has these options: > > -o,--object <SE Linux Object context> > -se,--context <SE Linux context> > -su,--subject <SE Linux context> > > Without multiple LSMs we can easily ignore "SE Linux" in these > options and use whatever kind of "context" is available. If I > have SELinux and AppArmor, the implication is that you can't > search on AppArmor information. Should we be adding > > -aa,--apparmorcontext <AppArmor context> > -as,--apparmorsubject <AppArmor subject context> > > or should we change -se to look at all "contexts", and change > the description to reflect that? Basicaly, I'm asking whether you'd > rather add options for other LSMs or remove descriptions that > specify SELinux. I'd say any/all contexts available by default. Then we can maybe make a restriction to specific LSM's later. -Steve > > I don't really know if its doing the right thing. > > > > Ausearch and report share a parser. It is time sensitive. I usually test > > it on 4 or 5 Gb of logs. We also have the ausearch-test program which > > can be used to test any changes to the parser. > > > > http://people.redhat.com/sgrubb/audit/ausearch-test-0.6.tar.gz > > > > Once that is squared away, there is the auparse library. It has a table > > that classifies a field name into what it is for interpretation > > purposes. You will find a #ifdef WITH_APPARMOR. I don't know if that > > table is complete or if it needs to be extended for any other MAC > > system. > > > > That then leads to the auparse normalizer. I don't know if we need to > > make > > any changes there. You can trigger its code with ausearch --format csv or > > -- format text. > > > > Also, we have some size limits in user space. How big can an event record > > be if the file is MAX_PATH name length and it has a space in its name or > > directory and each context is it's maximum size? We may need to think > > about how this might change the whole userspace ecosystem's size > > definition, MAX_AUDIT_MESSAGE_LENGTH, since this is part of the ABI. And > > the kernel also has AUDIT_MESSAGE_TEXT_MAX. What would you get with: > > > > # /usr/sbin/auditctl -m `perl -e 'print "A"x8880'` > > > > And last...what about auditctl? Is the syscall filter going to allow > > filtering on these other subject/object components? > > > > -Steve -- Linux-audit mailing list Linux-audit@redhat.com https://listman.redhat.com/mailman/listinfo/linux-audit ^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-06-14 19:34 ` Adding support for MAC_TASK_CONTEXTS and MAC_OBJ_CONTEXTS to userspace Casey Schaufler
2021-06-14 21:13 ` Steve Grubb
2021-06-15 17:01 ` Casey Schaufler
2021-06-15 21:15 ` Steve Grubb
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