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

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.