[PATCH] audit: unswing cap_* fields in PATH records

[Serge E. Hallyn]

Quoting Richard Guy Briggs (rgb at redhat.com):
> The cap_* fields swing in and out of PATH records.
> If no capabilities are set, the cap_* fields are completely missing and when
> one of the cap_fi or cap_fp values is empty, that field is omitted.
> 
> Original:
> type=PATH msg=audit(04/20/2017 12:17:11.222:193) : item=1 name=/lib64/ld-linux-x86-64.so.2 inode=787694 dev=08:03 mode=file,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:ld_so_t:s0 nametype=NORMAL
> type=PATH msg=audit(04/20/2017 12:17:11.222:193) : item=0 name=/home/sleep inode=1319469 dev=08:03 mode=file,suid,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:bin_t:s0 nametype=NORMAL cap_fp=sys_admin cap_fe=1 cap_fver=2
> 
> Normalize the PATH record by always printing all 4 cap_* fields.
> 
> Fixed:
> type=PATH msg=audit(04/20/2017 13:01:31.679:201) : item=1 name=/lib64/ld-linux-x86-64.so.2 inode=787694 dev=08:03 mode=file,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:ld_so_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0
> type=PATH msg=audit(04/20/2017 13:01:31.679:201) : item=0 name=/home/sleep inode=1319469 dev=08:03 mode=file,suid,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:bin_t:s0 nametype=NORMAL cap_fp=sys_admin cap_fi=none cap_fe=1 cap_fver=2
> 
> See: https://github.com/linux-audit/audit-kernel/issues/42
> 
> Signed-off-by: Richard Guy Briggs <rgb at redhat.com>

Is this a big problem for the audit daemon?  There's no actual incorrectness
here right?  I'm not completely opposed, but it does seem like a waste of
space in the (overwhelmingly) most common cases.

> ---
>  kernel/audit.c |   20 ++++----------------
>  1 files changed, 4 insertions(+), 16 deletions(-)
> 
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 10bc2ba..de264d1 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -1956,22 +1956,10 @@ void audit_log_cap(struct audit_buffer *ab, char *prefix, kernel_cap_t *cap)
>  
>  static void audit_log_fcaps(struct audit_buffer *ab, struct audit_names *name)
>  {
> -	kernel_cap_t *perm = &name->fcap.permitted;
> -	kernel_cap_t *inh = &name->fcap.inheritable;
> -	int log = 0;
> -
> -	if (!cap_isclear(*perm)) {
> -		audit_log_cap(ab, "cap_fp", perm);
> -		log = 1;
> -	}
> -	if (!cap_isclear(*inh)) {
> -		audit_log_cap(ab, "cap_fi", inh);
> -		log = 1;
> -	}
> -
> -	if (log)
> -		audit_log_format(ab, " cap_fe=%d cap_fver=%x",
> -				 name->fcap.fE, name->fcap_ver);
> +	audit_log_cap(ab, "cap_fp", &name->fcap.permitted);
> +	audit_log_cap(ab, "cap_fi", &name->fcap.inheritable);
> +	audit_log_format(ab, " cap_fe=%d cap_fver=%x",
> +			 name->fcap.fE, name->fcap_ver);
>  }
>  
>  static inline int audit_copy_fcaps(struct audit_names *name,
> -- 
> 1.7.1