*: 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, 13 insertions, 62 deletions

diff --git a/loginutils/addgroup.c b/loginutils/addgroup.c
index 5032d7b99..5a0cf3fff 100644
--- a/loginutils/addgroup.c
+++ b/loginutils/addgroup.c
@@ -9,7 +9,6 @@
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  *
  */
-
 #include "libbb.h"
 
 static void xgroup_study(struct group *g)
@@ -45,8 +44,8 @@ static void xgroup_study(struct group *g)
 /* append a new user to the passwd file */
 static void new_group(char *group, gid_t gid)
 {
-        FILE *file;
         struct group gr;
+        char *p;
 
         /* make sure gid and group haven't already been allocated */
         gr.gr_gid = gid;
@@ -54,67 +53,17 @@ static void new_group(char *group, gid_t gid)
         xgroup_study(&gr);
 
         /* add entry to group */
-        file = xfopen(bb_path_group_file, "a");
-        /* group:passwd:gid:userlist */
-        fprintf(file, "%s:x:%u:\n", group, (unsigned)gr.gr_gid);
+        p = xasprintf("x:%u:", gr.gr_gid);
+        if (update_passwd(bb_path_group_file, group, p, NULL) < 0)
+                exit(EXIT_FAILURE);
         if (ENABLE_FEATURE_CLEAN_UP)
-                fclose(file);
+                free(p);
 #if ENABLE_FEATURE_SHADOWPASSWDS
-        file = fopen_or_warn(bb_path_gshadow_file, "a");
-        if (file) {
-                fprintf(file, "%s:!::\n", group);
-                if (ENABLE_FEATURE_CLEAN_UP)
-                        fclose(file);
-        }
+        /* Ignore errors: if file is missing we suppose admin doesn't want it */
+        update_passwd(bb_path_gshadow_file, group, "!::", NULL);
 #endif
 }
 
-#if ENABLE_FEATURE_ADDUSER_TO_GROUP
-static void add_user_to_group(char **args,
-                const char *path,
-                FILE* FAST_FUNC (*fopen_func)(const char *fileName, const char *mode))
-{
-        char *line;
-        int len = strlen(args[1]);
-        llist_t *plist = NULL;
-        FILE *group_file;
-
-        group_file = fopen_func(path, "r");
-
-        if (!group_file) return;
-
-        while ((line = xmalloc_fgetline(group_file)) != NULL) {
-                /* Find the group */
-                if (!strncmp(line, args[1], len)
-                 && line[len] == ':'
-                ) {
-                        /* Add the new user */
-                        line = xasprintf("%s%s%s", line,
-                                                last_char_is(line, ':') ? "" : ",",
-                                                args[0]);
-                }
-                llist_add_to_end(&plist, line);
-        }
-
-        if (ENABLE_FEATURE_CLEAN_UP) {
-                fclose(group_file);
-                group_file = fopen_func(path, "w");
-                while ((line = llist_pop(&plist))) {
-                        if (group_file)
-                                fprintf(group_file, "%s\n", line);
-                        free(line);
-                }
-                if (group_file)
-                        fclose(group_file);
-        } else {
-                group_file = fopen_func(path, "w");
-                if (group_file)
-                        while ((line = llist_pop(&plist)))
-                                fprintf(group_file, "%s\n", line);
-        }
-}
-#endif
-
 /*
  * addgroup will take a login_name as its first parameter.
  *
@@ -166,10 +115,12 @@ int addgroup_main(int argc UNUSED_PARAM, char **argv)
                                 return EXIT_SUCCESS;
                         }
                 }
-                add_user_to_group(argv, bb_path_group_file, xfopen);
-#if ENABLE_FEATURE_SHADOWPASSWDS
-                add_user_to_group(argv, bb_path_gshadow_file, fopen_or_warn);
-#endif
+                if (update_passwd(bb_path_group_file, argv[1], NULL, argv[0]) < 0) {
+                        return EXIT_FAILURE;
+                }
+# if ENABLE_FEATURE_SHADOWPASSWDS
+                update_passwd(bb_path_gshadow_file, argv[1], NULL, argv[0]);
+# endif
         } else
 #endif /* ENABLE_FEATURE_ADDUSER_TO_GROUP */
         {