[systemd-devel] [PATCH 1/2] Add switch_apparmor_profile helper, to switch the profile of the next command to run. This can be used to load a custom apparmor profile for a unit.

[Zbigniew Jędrzejewski-Szmek]

On Fri, Jan 03, 2014 at 05:22:42PM +0100, misc at zarb.org wrote:
> From: Michael Scherer <misc at zarb.org>
> 
> ---
>  src/shared/apparmor-util.c | 15 +++++++++++++++
>  src/shared/apparmor-util.h |  1 +
>  2 files changed, 16 insertions(+)
> 
> diff --git a/src/shared/apparmor-util.c b/src/shared/apparmor-util.c
> index 2b85da1..a75bec4 100644
> --- a/src/shared/apparmor-util.c
> +++ b/src/shared/apparmor-util.c
> @@ -39,3 +39,18 @@ bool use_apparmor(void) {
>  
>          return use_apparmor_cached;
>  }
> +
> +int switch_apparmor_profile(const char * profile) {
> +        _cleanup_free_ char *filename = NULL;
> +        _cleanup_fclose_ FILE *proc = NULL;
> +
> +        if (asprintf (&filename, "/proc/%d/attr/exec", getpid()) <0)
> +                return -ENOMEM;
> +
> +        proc = fopen (filename, "w");
> +        if (! proc)
> +                return -errno;
> +
> +        fprintf (proc, "exec %s\n", profile);
> +        return 0;
> +}
This should be something like

int apparmor_switch_profile(const char *profile) {
        char *p, *t;

        p = procfs_file_alloca(0, "attr/exec");
	t = strappenda("exec ", profile);

	return write_string_file(p, t);
}

Totally untested, but there's no unnecessary malloc, and there's
a meaningful error returned if the thing most likely to fail, i.e. the
write, actually fails.
	
> diff --git a/src/shared/apparmor-util.h b/src/shared/apparmor-util.h
> index 4b056a1..f27608d 100644
> --- a/src/shared/apparmor-util.h
> +++ b/src/shared/apparmor-util.h
> @@ -24,3 +24,4 @@
>  #include <stdbool.h>
>  
>  bool use_apparmor(void);
> +int switch_apparmor_profile(const char * profile);
                               const char *profile

Zbyszek