*: unify concurrent-safe update of /etc/{passwd,group,[g]shadow}

 by Tito (farmatito AT tiscali.it)

function                                             old     new   delta
update_passwd                                        743    1171    +428
bb_perror_nomsg                                        -       9      +9
find_main                                            436     444      +8
passwd_main                                         1023    1027      +4
nameval                                              202     206      +4
chpasswd_main                                        315     319      +4
bb__parsespent                                       119     117      -2
adduser_main                                         654     650      -4
addgroup_main                                        345     341      -4
sv_main                                             1228    1222      -6
deluser_main                                         173     160     -13
bb_internal_putpwent                                  69       -     -69
add_user_to_group                                    231       -    -231
del_line_matching                                    460      31    -429
------------------------------------------------------------------------------
(add/remove: 1/2 grow/shrink: 5/6 up/down: 457/-758)         Total: -301 bytes

1 files changed, 32 insertions, 101 deletions

diff --git a/loginutils/deluser.c b/loginutils/deluser.c
index 5625371..293e324 100644
--- a/loginutils/deluser.c
+++ b/loginutils/deluser.c
@@ -9,117 +9,48 @@
  * Licensed under GPL version 2, see file LICENSE in this tarball for details.
  *
  */
-
 #include "libbb.h"
 
-/* Status */
-#define STATUS_OK            0
-#define NAME_NOT_FOUND       1
-#define MEMBER_NOT_FOUND     2
-
-static void del_line_matching(char **args,
-		const char *filename,
-		FILE* FAST_FUNC (*fopen_func)(const char *fileName, const char *mode))
+static int del_line_matching(char **args, const char *filename)
 {
-	FILE *passwd;
-	smallint error = NAME_NOT_FOUND;
-	char *name = (ENABLE_FEATURE_DEL_USER_FROM_GROUP && args[2]) ? args[2] : args[1];
-	char *line, *del;
-	char *new = xzalloc(1);
-
-	passwd = fopen_func(filename, "r");
-	if (passwd) {
-		while ((line = xmalloc_fgets(passwd))) {
-			int len = strlen(name);
-
-			if (strncmp(line, name, len) == 0
-			 && line[len] == ':'
-			) {
-				error = STATUS_OK;
-				if (ENABLE_FEATURE_DEL_USER_FROM_GROUP) {
-					struct group *gr;
-					char *p;
-					if (args[2]
-					 /* There were two args on commandline */
-					 && (gr = getgrnam(name))
-					 /* The group was not deleted in the meanwhile */
-					 && (p = strrchr(line, ':'))
-					 /* We can find a pointer to the last ':' */
-					) {
-						error = MEMBER_NOT_FOUND;
-						/* Move past ':' (worst case to '\0') and cut the line */
-						p[1] = '\0';
-						/* Reuse p */
-						for (p = xzalloc(1); *gr->gr_mem != NULL; gr->gr_mem++) {
-							/* Add all the other group members */
-							if (strcmp(args[1], *gr->gr_mem) != 0) {
-								del = p;
-								p = xasprintf("%s%s%s", p, p[0] ? "," : "", *gr->gr_mem);
-								free(del);
-							} else
-								error = STATUS_OK;
-						}
-						/* Recompose the line */
-						line = xasprintf("%s%s\n", line, p);
-						if (ENABLE_FEATURE_CLEAN_UP) free(p);
-					} else
-						goto skip;
-				}
-			}
-			del = new;
-			new = xasprintf("%s%s", new, line);
-			free(del);
- skip:
-			free(line);
-		}
-
-		if (ENABLE_FEATURE_CLEAN_UP) fclose(passwd);
-
-		if (error) {
-			if (ENABLE_FEATURE_DEL_USER_FROM_GROUP && error == MEMBER_NOT_FOUND) {
-				/* Set the correct values for error message */
-				filename = name;
-				name = args[1];
-			}
-			bb_error_msg("can't find %s in %s", name, filename);
-		} else {
-			passwd = fopen_func(filename, "w");
-			if (passwd) {
-				fputs(new, passwd);
-				if (ENABLE_FEATURE_CLEAN_UP) fclose(passwd);
-			}
-		}
+	if (ENABLE_FEATURE_DEL_USER_FROM_GROUP && args[2]) {
+		return update_passwd(filename, args[2], NULL, args[1]);
 	}
-	free(new);
+	return update_passwd(filename, args[1], NULL, NULL);
 }
 
 int deluser_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int deluser_main(int argc, char **argv)
 {
-	if (argc == 2
-	 || (ENABLE_FEATURE_DEL_USER_FROM_GROUP
-	    && (applet_name[3] == 'g' && argc == 3))
+	if (argc != 2
+	 && (!ENABLE_FEATURE_DEL_USER_FROM_GROUP
+	    || (applet_name[3] != 'g' || argc != 3))
 	) {
-		if (geteuid())
-			bb_error_msg_and_die(bb_msg_perm_denied_are_you_root);
+		bb_show_usage();
+	}
 
-		if ((ENABLE_FEATURE_DEL_USER_FROM_GROUP && argc != 3)
-		 || ENABLE_DELUSER
-		 || (ENABLE_DELGROUP && ENABLE_DESKTOP)
+	if (geteuid())
+		bb_error_msg_and_die(bb_msg_perm_denied_are_you_root);
+
+	if ((ENABLE_FEATURE_DEL_USER_FROM_GROUP && argc != 3)
+	 || ENABLE_DELUSER
+	 || (ENABLE_DELGROUP && ENABLE_DESKTOP)
+	) {
+		if (ENABLE_DELUSER
+		 && (!ENABLE_DELGROUP || applet_name[3] == 'u')
 		) {
-			if (ENABLE_DELUSER
-			 && (!ENABLE_DELGROUP || applet_name[3] == 'u')
-			) {
-				del_line_matching(argv, bb_path_passwd_file, xfopen);
-				if (ENABLE_FEATURE_SHADOWPASSWDS)
-					del_line_matching(argv, bb_path_shadow_file, fopen_or_warn);
-			} else if (ENABLE_DESKTOP && ENABLE_DELGROUP && getpwnam(argv[1]))
-				bb_error_msg_and_die("can't remove primary group of user %s", argv[1]);
-		}
-		del_line_matching(argv, bb_path_group_file, xfopen);
-		if (ENABLE_FEATURE_SHADOWPASSWDS)
-			del_line_matching(argv, bb_path_gshadow_file, fopen_or_warn);
-		return EXIT_SUCCESS;
-	} else
-		bb_show_usage();
+			if (del_line_matching(argv, bb_path_passwd_file) < 0)
+				return EXIT_FAILURE;
+			if (ENABLE_FEATURE_SHADOWPASSWDS) {
+				del_line_matching(argv, bb_path_shadow_file);
+			}
+		} else if (ENABLE_DESKTOP && ENABLE_DELGROUP && getpwnam(argv[1]))
+			bb_error_msg_and_die("can't remove primary group of user %s", argv[1]);
+	}
+	if (del_line_matching(argv, bb_path_group_file) < 0)
+		return EXIT_FAILURE;
+	if (ENABLE_FEATURE_SHADOWPASSWDS) {
+		del_line_matching(argv, bb_path_gshadow_file);
+	}
+	return EXIT_SUCCESS;
 }