[PATCH v2 3/9] setpriv: dump user and group info

[Tito]

Hi,
just a few hints (untested).

Ciao,
Tito

On 07/02/2017 03:42 PM, Patrick Steinhardt wrote:
> setpriv from util-linux has an option to dump the current state
> regarding privilege settings via `--dump`. It prints out information on
> the real and effective user and group IDs, supplementary groups, the
> no-new-privs flag, the capability sets as well as secure bits.
> 
> This patch is the start of supporting this mode. To make introduction of
> the `--dump` easier to reason about, its introduction has been split
> into multiple patches. This particular one introduces the ability to
> print out user and group information of the current process.
> ---
>  util-linux/setpriv.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 69 insertions(+), 2 deletions(-)
> 
> diff --git a/util-linux/setpriv.c b/util-linux/setpriv.c
> index d586f4bef..dabc6d355 100644
> --- a/util-linux/setpriv.c
> +++ b/util-linux/setpriv.c
> @@ -15,6 +15,14 @@
>  //config:	help
>  //config:	  Run a program with different Linux privilege settings.
>  //config:	  Requires kernel >= 3.5
> +//config:
> +//config:config FEATURE_SETPRIV_DUMP
> +//config:	bool "Support dumping current privilege state"
> +//config:	default y
> +//config:	depends on SETPRIV
> +//config:	help
> +//config:		Enables the "--dump" switch to print out the current privilege
> +//config:		state. This is helpful for diagnosing problems.
>  
>  //applet:IF_SETPRIV(APPLET(setpriv, BB_DIR_BIN, BB_SUID_DROP))
>  
> @@ -24,6 +32,9 @@
>  //usage:	"[OPTIONS] PROG [ARGS]"
>  //usage:#define setpriv_full_usage "\n\n"
>  //usage:       "Run PROG with different privilege settings\n"
> +//usage:	IF_FEATURE_SETPRIV_DUMP(
> +//usage:     "\n-d,--dump		Show current capabilities"
> +//usage:	)
>  //usage:     "\n--nnp,--no-new-privs	Ignore setuid/setgid bits and file capabilities"
>  
>  //setpriv from util-linux 2.28:
> @@ -45,6 +56,7 @@
>  // --apparmor-profile <pr>  set AppArmor profile
>  
>  #include <sys/prctl.h>
> +#include <unistd.h>
>  #include "libbb.h"
>  
>  #ifndef PR_SET_NO_NEW_PRIVS
> @@ -52,15 +64,61 @@
>  #endif
>  
>  enum {
> +	IF_FEATURE_SETPRIV_DUMP(OPTBIT_DUMP,)
>  	OPTBIT_NNP,
>  
> -	OPT_NNP = (1 << OPTBIT_NNP),
> +	IF_FEATURE_SETPRIV_DUMP(OPT_DUMP = (1 << OPTBIT_DUMP),)
> +	OPT_NNP  = (1 << OPTBIT_NNP),
>  };
>  
> +#if ENABLE_FEATURE_SETPRIV_DUMP
> +static int dump(void)
> +{
> +	uid_t ruid, euid, suid;
> +	gid_t rgid, egid, sgid;
> +	gid_t *gids;
> +	int ngids;
> +
> +	if (getresuid(&ruid, &euid, &suid) < 0)
> +		bb_simple_perror_msg_and_die("getresgid");
> +
> +	if (getresgid(&rgid, &egid, &sgid) < 0)
> +		bb_simple_perror_msg_and_die("getresgid");
> +
> +	if ((ngids = getgroups(0, NULL)) < 0)
> +		bb_simple_perror_msg_and_die("getgroups");

	Getgroups is expensive, maybe try to run  it only once? see id.c and test.c
        (eventually common code for a libbb function?)

	n = 32;
	*n = getgroups(*n, groups);
	if (*n >= 0)
		return *n;
	/* Error */
	if (errno == EINVAL) /* *n is too small? */
		*n = getgroups(0, groups); /* get needed *n */
	/* if *n >= 0, return -1 (got new *n), else return 0 (error): */
	return -(*n >= 0);

> +	gids = xmalloc(ngids * sizeof(*gids));
> +	if ((ngids = getgroups(ngids, gids)) < 0)
> +		bb_simple_perror_msg_and_die("getgroups");
> +
> +	printf("uid: %d\n", ruid);
> +	printf("euid: %d\n", euid);
> +	printf("gid: %d\n", rgid);
> +	printf("egid: %d\n", egid);
> +
> +	printf("Supplementary groups: ");
> +	
        just ne  line, more code fits on the screen.
	printf("uid: %d\neuid: %d\ngid: %d\negid: %d\nSupplementary groups: ", ruid, euid, rgid, egid);
         
> +     if (ngids == 0) {
> +		printf("[none]");
> +	} else {
> +		int i;
> +		for (i = 0; i < ngids; i++) {
> +			if (i)
> +				putchar(',');
> +			printf("%d", gids[i]);
> +		}
> +	}
> +	putchar('\n');
> +
> +	free(gids);
> +	return 0;
> +}
> +#endif /* FEATURE_SETPRIV_DUMP */
> +
>  int setpriv_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
>  int setpriv_main(int argc UNUSED_PARAM, char **argv)
>  {
>  	static const char setpriv_longopts[] ALIGN1 =
> +		IF_FEATURE_SETPRIV_DUMP("dump\0"         No_argument	"d")
>  		"nnp\0"          No_argument	"\xff"
>  		"no-new-privs\0" No_argument	"\xff"
>  		;
> @@ -68,11 +126,20 @@ int setpriv_main(int argc UNUSED_PARAM, char **argv)
>  
>  	opt_complementary = "";
>  	applet_long_options = setpriv_longopts;
> -	opts = getopt32(argv, "+");
> +	opts = getopt32(argv, "+" IF_FEATURE_SETPRIV_DUMP("d"));
>  
>  	argc -= optind;
>  	argv += optind;
>  
> +#if ENABLE_FEATURE_SETPRIV_DUMP
> +	if (opts & OPT_DUMP) {
> +		if ((opts & ~OPT_DUMP) || argc)
			applet name is not needed as it is added by bb_error_msg_and_die, shorter error message
                        would be nice.
> +			bb_error_msg_and_die("setpriv: --dump is incompatible with all other options");
> +
> +		return dump();
> +	}
> +#endif
> +
>  	if (!argc)
>  		bb_error_msg_and_die("no program specified");
>  
>