Re: [PATCH v2 3/4] seccomp: Audit attempts to modify the actions_logged sysctl

On Thu, May 3, 2018 at 4:42 PM, Steve Grubb <sgrubb(a)redhat.com&gt; wrote: > On Thursday, May 3, 2018 4:18:26 PM EDT Paul Moore wrote: >> On Wed, May 2, 2018 at 2:18 PM, Steve Grubb <sgrubb(a)redhat.com&gt; wrote: >>> On Wednesday, May 2, 2018 11:53:19 AM EDT Tyler Hicks wrote: >>>> The decision to log a seccomp action will always be subject to the >>>> value of the kernel.seccomp.actions_logged sysctl, even for processes >>>> that are being inspected via the audit subsystem, in an upcoming patch. >>>> Therefore, we need to emit an audit record on attempts at writing to the >>>> actions_logged sysctl when auditing is enabled. >>>> >>>> This patch updates the write handler for the actions_logged sysctl to >>>> emit an audit record on attempts to write to the sysctl. Successful >>>> writes to the sysctl will result in a record that includes a normalized >>>> list of logged actions in the "actions" field and a "res" field equal to >>>> 0. Unsuccessful writes to the sysctl will result in a record that >>>> doesn't include the "actions" field and has a "res" field equal to 1. >>>> >>>> Not all unsuccessful writes to the sysctl are audited. For example, an >>>> audit record will not be emitted if an unprivileged process attempts to >>>> open the sysctl file for reading since that access control check is not >>>> part of the sysctl's write handler. >>>> >>>> Below are some example audit records when writing various strings to the >>>> actions_logged sysctl. >>>> >>>> Writing "not-a-real-action", when the kernel.seccomp.actions_logged >>>> sysctl previously was "kill_process kill_thread trap errno trace log", >>>> >>>> emits this audit record: >>>> type=CONFIG_CHANGE msg=audit(1525275273.537:130): op=seccomp-logging >>>> old-actions=kill_process,kill_thread,trap,errno,trace,log res=0 >>>> >>>> If you then write "kill_process kill_thread errno trace log", this audit >>>> >>>> record is emitted: >>>> type=CONFIG_CHANGE msg=audit(1525275310.208:136): op=seccomp-logging >>>> actions=kill_process,kill_thread,errno,trace,log >>>> old-actions=kill_process,kill_thread,trap,errno,trace,log res=1 >>>> >>>> If you then write the string "log log errno trace kill_process >>>> kill_thread", which is unordered and contains the log action twice, >>>> >>>> it results in the same actions value as the previous record: >>>> type=CONFIG_CHANGE msg=audit(1525275325.613:142): op=seccomp-logging >>>> actions=kill_process,kill_thread,errno,trace,log >>>> old-actions=kill_process,kill_thread,errno,trace,log res=1 >>>> >>>> No audit records are generated when reading the actions_logged sysctl. >>> >>> ACK for the format of the records. >> >> I just wanted to clarify the record format with you Steve ... the >> "actions" and "old-actions" fields may not be included in the record >> in cases where there is an error building the action value string, are >> you okay with that or would you prefer the fields to always be >> included but with a "?" for the value? > > A ? would be more in line with how other things are handled. That's what I thought. Would you mind putting together a v3 Tyler? :)