busybox.conf: USER.GROUP is _optional_

function                                             old     new   delta
main                                                 785     809     +24

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 16 insertions, 14 deletions

diff --git a/Config.in b/Config.in
index b65fe4530..8f4d64274 100644
--- a/Config.in
+++ b/Config.in
@@ -350,15 +350,17 @@ config FEATURE_SUID_CONFIG
 	  by checking /etc/busybox.conf. (This is sort of a poor man's sudo.)
 	  The format of this file is as follows:
 
-	  APPLET = [Ssx-][Ssx-][x-] USER.GROUP
+	  APPLET = [Ssx-][Ssx-][x-] [USER.GROUP]
 
-	  s: This user/group are allowed to execute APPLET.
+	  s: USER or GROUP is allowed to execute APPLET.
+	     APPLET will run under USER or GROUP
+	     (reagardless of who's running it).
+	  S: USER or GROUP is NOT allowed to execute APPLET.
 	     APPLET will run under USER or GROUP.
-	  x: User/group/others are allowed to execute APPLET.
+	     This option is not very sensical.
+	  x: USER/GROUP/others are allowed to execute APPLET.
 	     No UID/GID change will be done when it is run.
-	  S: This user/group are NOT allowed to execute APPLET.
-	     APPLET will run under USER or GROUP.
-	  -: User/group/others are not allowed to execute APPLET.
+	  -: USER/GROUP/others are not allowed to execute APPLET.
 
 	  An example might help:
 
@@ -368,7 +370,8 @@ config FEATURE_SUID_CONFIG
 	  su = ssx        # exactly the same
 
 	  mount = sx- root.disk # applet mount can be run by root and members
-	                        # of group disk and runs with euid=0
+	                        # of group disk (but not anyone else)
+	                        # and runs with euid=0 (egid is not changed)
 
 	  cp = --- # disable applet cp for everyone
 
diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index ed60a1a0a..86b5cd381 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -261,9 +261,7 @@ static int ingroup(uid_t u, gid_t g)
 	return 0;
 }
 
-/* This should probably be a libbb routine.  In that case,
- * I'd probably rename it to something like bb_trimmed_slice.
- */
+/* libbb candidate */
 static char *get_trimmed_slice(char *s, char *e)
 {
 	/* First, consider the value at e to be nul and back up until we
@@ -442,15 +440,16 @@ static void parse_config_file(void)
 				/* Now get the user/group info. */
 
 				s = skip_whitespace(e);
+				if (*s == '\0')
+					s = strcpy(buffer, "0.0");
 
-				/* Note: we require whitespace between the mode and the
-				 * user/group info. */
+				/* We require whitespace between mode and USER.GROUP */
 				if ((s == e) || !(e = strchr(s, '.'))) {
 					errmsg = "uid.gid";
 					goto pe_label;
 				}
 
-				*e = ':'; /* get_uidgid doesn't understand user.group */
+				*e = ':'; /* get_uidgid needs USER:GROUP syntax */
 				if (get_uidgid(&sct->m_ugid, s, /*allow_numeric:*/ 1) == 0) {
 					errmsg = "unknown user/group";
 					goto pe_label;
@@ -518,7 +517,7 @@ static void check_suid(int applet_no)
 			/* same group / in group */
 			m >>= 3;
 		if (!(m & S_IXOTH)) /* is x bit not set? */
-			bb_error_msg_and_die("you have no permission to run this applet!");
+			bb_error_msg_and_die("you have no permission to run this applet");
 
 		/* We set effective AND saved ids. If saved-id is not set
 		 * like we do below, seteuid(0) can still later succeed! */