Re: [PATCH 1/1] security: introduce file posix caps

From: Serge E. Hallyn
Date: Tue Nov 07 2006 - 10:11:31 EST


Quoting Stephen Smalley (sds@xxxxxxxxxxxxx):
> On Mon, 2006-11-06 at 21:45 -0600, Serge E. Hallyn wrote:
> > Implement file posix capabilities. This allows programs to be given
> > a subset of root's powers regardless of who runs them, without
> > having to use setuid and giving the binary all of root's powers.
>
> > diff --git a/include/linux/security.h b/include/linux/security.h
> > index b200b98..ea631ee 100644
> > --- a/include/linux/security.h
> > +++ b/include/linux/security.h
> > @@ -53,6 +53,10 @@ extern int cap_inode_setxattr(struct den
> > extern int cap_inode_removexattr(struct dentry *dentry, char *name);
> > extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags);
> > extern void cap_task_reparent_to_init (struct task_struct *p);
> > +extern int cap_task_kill(struct task_struct *p, struct siginfo *info, int sig, u32 secid);
> > +extern int cap_task_setscheduler (struct task_struct *p, int policy, struct sched_param *lp);
> > +extern int cap_task_setioprio (struct task_struct *p, int ioprio);
> > +extern int cap_task_setnice (struct task_struct *p, int nice);
> > extern int cap_syslog (int type);
> > extern int cap_vm_enough_memory (long pages);
> >
> > @@ -2594,12 +2598,12 @@ static inline int security_task_setgroup
> >
> > static inline int security_task_setnice (struct task_struct *p, int nice)
> > {
> > - return 0;
> > + return cap_task_setnice(p, nice);
> > }
> >
> > static inline int security_task_setioprio (struct task_struct *p, int ioprio)
> > {
> > - return 0;
> > + return cap_task_setioprio(p, ioprio);
> > }
> >
> > static inline int security_task_getioprio (struct task_struct *p)
>
> setscheduler change seems to be missing here.

I'm confused - my kernel version already had selinux_task_setscheduler()
calling a secondary_ops->task_setscheduler().

I don't know where that came from then.

> > @@ -2634,7 +2638,7 @@ static inline int security_task_kill (st
> > struct siginfo *info, int sig,
> > u32 secid)
> > {
> > - return 0;
> > + return cap_task_kill(p, info, sig, secid);
> > }
> >
> > static inline int security_task_wait (struct task_struct *p)
>
> > diff --git a/security/commoncap.c b/security/commoncap.c
> > index 5a5ef5c..0eae004 100644
> > --- a/security/commoncap.c
> > +++ b/security/commoncap.c
> > +int cap_task_kill(struct task_struct *p, struct siginfo *info,
> > + int sig, u32 secid)
> > +{
> > + if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info)))
> > + return 0;
> > +
> > + if (secid)
> > + /*
> > + * Signal sent as a particular user.
> > + * Capabilities are ignored. May be wrong, but it's the
> > + * only thing we can do at the moment.
> > + * Used only by usb drivers?
> > + */
> > + return 0;
> > + if (capable(CAP_KILL))
> > + return 0;
>
> This will trigger spurious audit messages; should only be checked if
> next test fails.
>

I see, will swap, thanks.

> > + if (cap_issubset(p->cap_permitted, current->cap_permitted))
> > + return 0;
> > +
> > + return -EPERM;
> > +}
> > +
> > void cap_task_reparent_to_init (struct task_struct *p)
> > {
> > p->cap_effective = CAP_INIT_EFF_SET;
>
> --
> Stephen Smalley
> National Security Agency
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