On 2017-03-02 21:50, Richard Guy Briggs wrote: > On 2017-03-02 20:07, Serge E. Hallyn wrote: > > On Thu, Mar 02, 2017 at 08:10:29PM -0500, Richard Guy Briggs wrote: > > > The audit subsystem is adding a BPRM_FCAPS record when auditing setuid > > > application execution (SYSCALL execve). This is not expected as it was > > > supposed to be limited to when the file system actually had capabilities > > > in an extended attribute. It lists all capabilities making the event > > > really ugly to parse what is happening. The PATH record correctly > > > records the setuid bit and owner. Suppress the BPRM_FCAPS record on > > > set*id. > > > > > > See: https://github.com/linux-audit/audit-kernel/issues/16 > > > > Hey Richard, > > Hi Serge, > > > one possibly audit-worth case which (if I read correctly) this will > > skip is where a setuid-root binary has filecaps which *limit* its privs. > > Does that matter? > > I hadn't thought of that case, but I did consider in the setuid case > comparing before and after without setuid forcing the drop of all > capabilities via "ambient". Mind you, this bug has been around before > Luto's patch that adds the ambient capabilities set.
Can you suggest a scenario where that might happen? Can you come up with an idea for a test case? At first I figured I could simply go from root and su to an unprivileged user, but that doesn't trigger it and then naively thought I could strace both directions to find out the difference and su or sudo to root really doesn't like being straced. > Paul? > > > > Signed-off-by: Richard Guy Briggs <[email protected]> > > > --- > > > security/commoncap.c | 5 +++-- > > > 1 files changed, 3 insertions(+), 2 deletions(-) > > > > > > diff --git a/security/commoncap.c b/security/commoncap.c > > > index 14540bd..8f6bedf 100644 > > > --- a/security/commoncap.c > > > +++ b/security/commoncap.c > > > @@ -594,16 +594,17 @@ skip: > > > /* > > > * Audit candidate if current->cap_effective is set > > > * > > > - * We do not bother to audit if 3 things are true: > > > + * We do not bother to audit if 4 things are true: > > > * 1) cap_effective has all caps > > > * 2) we are root > > > * 3) root is supposed to have all caps (SECURE_NOROOT) > > > + * 4) we are running a set*id binary > > > * Since this is just a normal root execing a process. > > > * > > > * Number 1 above might fail if you don't have a full bset, but I think > > > * that is interesting information to audit. > > > */ > > > - if (!cap_issubset(new->cap_effective, new->cap_ambient)) { > > > + if (!is_setid && !cap_issubset(new->cap_effective, new->cap_ambient)) { > > > if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || > > > !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) > > > || > > > issecure(SECURE_NOROOT)) { > > > -- > > > 1.7.1 > > - RGB - RGB -- Richard Guy Briggs <[email protected]> Kernel Security Engineering, Base Operating Systems, Red Hat Remote, Ottawa, Canada Voice: +1.647.777.2635, Internal: (81) 32635 -- Linux-audit mailing list [email protected] https://www.redhat.com/mailman/listinfo/linux-audit
