adduser: allow adding to group 0; don't _create_ /etc/shadow,

 only append data if it exists.

function                                             old     new   delta
adduser_main                                         642     667     +25

1 files changed, 15 insertions, 13 deletions

diff --git a/loginutils/adduser.c b/loginutils/adduser.c
index 3154806b6..d4b50130c 100644
--- a/loginutils/adduser.c
+++ b/loginutils/adduser.c
@@ -33,18 +33,17 @@ static void passwd_study(struct passwd *p)
         }
 
         /* check for a free uid (and maybe gid) */
-        while (getpwuid(p->pw_uid) || (!p->pw_gid && getgrgid(p->pw_uid)))
+        while (getpwuid(p->pw_uid) || (p->pw_gid == (gid_t)-1 && getgrgid(p->pw_uid))) {
                 p->pw_uid++;
+                if (p->pw_uid > max)
+                        bb_error_msg_and_die("no free uids left");
+        }
 
-        if (!p->pw_gid) {
-                /* new gid = uid */
-                p->pw_gid = p->pw_uid;
+        if (p->pw_gid == (gid_t)-1) {
+                p->pw_gid = p->pw_uid; /* new gid = uid */
                 if (getgrnam(p->pw_name))
                         bb_error_msg_and_die("group name '%s' is in use", p->pw_name);
         }
-
-        if (p->pw_uid > max)
-                bb_error_msg_and_die("no free uids left");
 }
 
 static void addgroup_wrapper(struct passwd *p)
@@ -90,6 +89,7 @@ int adduser_main(int argc UNUSED_PARAM, char **argv)
         struct passwd pw;
         const char *usegroup = NULL;
         FILE *file;
+        int fd;
 
 #if ENABLE_FEATURE_ADDUSER_LONG_OPTIONS
         applet_long_options = adduser_longopts;
@@ -117,7 +117,7 @@ int adduser_main(int argc UNUSED_PARAM, char **argv)
                 pw.pw_dir = xasprintf("/home/%s", argv[0]);
         }
         pw.pw_passwd = (char *)"x";
-        pw.pw_gid = usegroup ? xgroup2gid(usegroup) : 0; /* exits on failure */
+        pw.pw_gid = usegroup ? xgroup2gid(usegroup) : -1; /* exits on failure */
 
         /* make sure everything is kosher and setup uid && maybe gid */
         passwd_study(&pw);
@@ -134,17 +134,19 @@ int adduser_main(int argc UNUSED_PARAM, char **argv)
 
 #if ENABLE_FEATURE_SHADOWPASSWDS
         /* add to shadow if necessary */
-        file = fopen_or_warn(bb_path_shadow_file, "a");
-        if (file) {
-                //fseek(file, 0, SEEK_END);
-                fprintf(file, "%s:!:%u:0:99999:7:::\n",
+        /* fopen(..., "a"); would create shadow file, which is wrong.
+         * If shadow file doesn't exist, admin probably does not want it */
+        fd = open_or_warn(bb_path_shadow_file, O_WRONLY | O_APPEND);
+        if (fd >= 0) {
+                char *s = xasprintf("%s:!:%u:0:99999:7:::\n",
                                 pw.pw_name,             /* username */
                                 (unsigned)(time(NULL) / 86400) /* sp->sp_lstchg */
                                 /*0,*/                  /* sp->sp_min */
                                 /*99999,*/              /* sp->sp_max */
                                 /*7*/                   /* sp->sp_warn */
                 );
-                fclose(file);
+                xwrite(fd, s, strlen(s));
+                close(fd);
         }
 #endif