test-container: unshare hints and su mode

  Adding "su" to your <test>.script causes the test to run with uid/gid
0/0 instead of the user's uid/gid.

Also a repeat of the unshare hints patch, with all corrections as
requested.

	* support/test-container.c (check_for_unshare_hints): New.
	(main): Call it if unshare fails.  Add support for "su" scriptlet
	command.
  

On 12/3/18 3:05 PM, DJ Delorie wrote:
> Adding "su" to your <test>.script causes the test to run with uid/gid
> 0/0 instead of the user's uid/gid.

This is exactly what I need for my tst-localedef-hardlinks test which
exercises the --no-hard-link option.

OK with additional documentation requested below:

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> Also a repeat of the unshare hints patch, with all corrections as
> requested.
> 
> 	* support/test-container.c (check_for_unshare_hints): New.
> 	(main): Call it if unshare fails.  Add support for "su" scriptlet
> 	command.
> 
> diff --git a/support/test-container.c b/support/test-container.c
> index b58f0f7b3d..52ee787544 100644
> --- a/support/test-container.c
> +++ b/support/test-container.c
> @@ -91,6 +91,7 @@ int verbose = 0;
>     * mytest.root/mytset.script has a list of "commands" to run:
>         syntax:
>           # comment
> +         su

OK.

>           mv FILE FILE
>  	 cp FILE FILE
>  	 rm FILE

Underneth "syntax:" and nested at the same level I think we should
write:

 91    * mytest.root/mytset.script has a list of "commands" to run:
 92        syntax:
 93          # comment
 94          mv FILE FILE
 95          cp FILE FILE
 96          rm FILE
 97          FILE must start with $B/, $S/, $I/, $L/, or /
 98           (expands to build dir, source dir, install dir, library dir
 99            (in container), or container's root)
           details:
             - '#': A comment.
	     - 'mv': A minimal move files command.
             - 'cp': A minimal copy files command.
             - 'rm': A minimal remove files command.
             - 'su': Enables running test as root in the container.

These lines describe what we have above.

> @@ -610,6 +611,47 @@ rsync (char *src, char *dest, int and_delete)
>  }
>  
>  
> +
> +/* See if we can detect what the user needs to do to get unshare
> +   support working for us.  */
> +void
> +check_for_unshare_hints (void)
> +{
> +  FILE *f;
> +  int i;
> +
> +  /* Default Debian Linux disables user namespaces, but allows a way
> +     to enable them.  */
> +  f = fopen ("/proc/sys/kernel/unprivileged_userns_clone", "r");

OK.

> +  if (f != NULL)
> +    {
> +      i = 99; /* Sentinel.  */
> +      fscanf (f, "%d", &i);
> +      if (i == 0)
> +	{
> +	  printf ("To enable test-container, please run this as root:\n");
> +	  printf ("  echo 1 > /proc/sys/kernel/unprivileged_userns_clone\n");
> +	}
> +      fclose (f);
> +      return;
> +    }
> +
> +  /* ALT Linux has an alternate way of doing the same.  */
> +  f = fopen ("/proc/sys/kernel/userns_restrict", "r");
> +  if (f != NULL)
> +    {
> +      i = 99; /* Sentinel.  */
> +      fscanf (f, "%d", &i);
> +      if (i == 1)
> +	{
> +	  printf ("To enable test-container, please run this as root:\n");
> +	  printf ("  echo 0 > /proc/sys/kernel/userns_restrict\n");
> +	}
> +      fclose (f);
> +      return;
> +    }
> +}

OK.

> +
>  int
>  main (int argc, char **argv)
>  {
> @@ -628,6 +670,8 @@ main (int argc, char **argv)
>  
>    uid_t original_uid;
>    gid_t original_gid;
> +  /* If set, the test runs as root instead of the user running the testsuite.  */
> +  int be_su = 0;

OK.

>    int UMAP;
>    int GMAP;
>    /* Used for "%lld %lld 1" so need not be large.  */
> @@ -857,6 +901,10 @@ main (int argc, char **argv)
>  	      {
>  		maybe_xunlink (the_words[1]);
>  	      }
> +	    else if (nt == 1 && strcmp (the_words[0], "su") == 0)
> +	      {
> +		be_su = 1;
> +	      }

OK.

>  	    else if (nt > 0 && the_words[0][0] != '#')
>  	      {
>  		printf ("\033[31minvalid [%s]\033[0m\n", the_words[0]);
> @@ -873,7 +921,12 @@ main (int argc, char **argv)
>        /* Older kernels may not support all the options, or security
>  	 policy may block this call.  */
>        if (errno == EINVAL || errno == EPERM)
> -	FAIL_UNSUPPORTED ("unable to unshare user/fs: %s", strerror (errno));
> +	{
> +	  int saved_errno = errno;
> +	  if (errno == EPERM)
> +	    check_for_unshare_hints ();
> +	  FAIL_UNSUPPORTED ("unable to unshare user/fs: %s", strerror (saved_errno));
> +	}

OK.

>        else
>  	FAIL_EXIT1 ("unable to unshare user/fs: %s", strerror (errno));
>      }
> @@ -952,7 +1005,7 @@ main (int argc, char **argv)
>      FAIL_EXIT1 ("can't write to /proc/self/uid_map\n");
>  
>    sprintf (tmp, "%lld %lld 1\n",
> -	   (long long) original_uid, (long long) original_uid);
> +	   (long long) (be_su ? 0 : original_uid), (long long) original_uid);

OK.

>    write (UMAP, tmp, strlen (tmp));
>    xclose (UMAP);
>  
> @@ -973,7 +1026,7 @@ main (int argc, char **argv)
>      FAIL_EXIT1 ("can't write to /proc/self/gid_map\n");
>  
>    sprintf (tmp, "%lld %lld 1\n",
> -	   (long long) original_gid, (long long) original_gid);
> +	   (long long) (be_su ? 0 : original_gid), (long long) original_gid);

OK.

>    write (GMAP, tmp, strlen (tmp));
>    xclose (GMAP);
>  
>