Any time fcaps or a setuid app under SECURE_NOROOT is used to result in a

non-zero pE we will crate a new audit record which contains the entire set
of known information about the executable in question, fP, fI, fE, fversion
and includes the process's pE, pI, pP.  Before and after the bprm capability
are applied.  This record type will only be emitted from execve syscalls.

an example of making ping use fcaps instead of setuid:

setcap "cat_net_raw+pe" /bin/ping

type=SYSCALL msg=audit(1225742021.015:236): arch=c000003e syscall=59 success=yes exit=0 a0=1457f30 a1=14606b0 a2=1463940 a3=321b770a70 items=2 ppid=2929 pid=2963 auid=0 uid=500 gid=500 euid=500 suid=500 fsuid=500 egid=500 sgid=500 fsgid=500 tty=pts0 ses=3 comm="ping" exe="/bin/ping" subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
type=UNKNOWN[1321] msg=audit(1225742021.015:236): fver=2 fp=0000000000002000 fi=0000000000000000 fe=1 old_pp=0000000000000000 old_pi=0000000000000000 old_pe=0000000000000000 new_pp=0000000000002000 new_pi=0000000000000000 new_pe=0000000000002000
type=EXECVE msg=audit(1225742021.015:236): argc=2 a0="ping" a1="127.0.0.1"
type=CWD msg=audit(1225742021.015:236):  cwd="/home/test"
type=PATH msg=audit(1225742021.015:236): item=0 name="/bin/ping" inode=49256 dev=fd:00 mode=0100755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:ping_exec_t:s0 cap_fp=0000000000002000 cap_fe=1 cap_fver=2
type=PATH msg=audit(1225742021.015:236): item=1 name=(null) inode=507915 dev=fd:00 mode=0100755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:ld_so_t:s0

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 22 insertions, 1 deletions

diff --git a/security/commoncap.c b/security/commoncap.c
index d7eff5797b91..d45393380997 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/capability.h>
+#include <linux/audit.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -376,6 +377,9 @@ int cap_bprm_set_security (struct linux_binprm *bprm)
 
 void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
 {
+        kernel_cap_t pP = current->cap_permitted;
+        kernel_cap_t pE = current->cap_effective;
+
         if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
             !cap_issubset(bprm->cap_post_exec_permitted,
                           current->cap_permitted)) {
@@ -409,7 +413,24 @@ void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
                         cap_clear(current->cap_effective);
         }
 
-        /* AUD: Audit candidate if current->cap_effective is set */
+        /*
+         * Audit candidate if current->cap_effective is set
+         *
+         * We do not bother to audit if 3 things are true:
+         *   1) cap_effective has all caps
+         *   2) we are root
+         *   3) root is supposed to have all caps (SECURE_NOROOT)
+         * 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_isclear(current->cap_effective)) {
+                if (!cap_issubset(CAP_FULL_SET, current->cap_effective) ||
+                    (bprm->e_uid != 0) || (current->uid != 0) ||
+                    issecure(SECURE_NOROOT))
+                        audit_log_bprm_fcaps(bprm, &pP, &pE);
+        }
 
         current->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
 }