appletlib.c: make it actally follow _BB_SUID_ALWAYS rules

adduser: implement -S and code shrink / fix uid selection
*: sanitize getspnam_r use

   text    data     bss     dec     hex filename
 777042     974    9676  787692   c04ec busybox_old
 776883     974    9676  787533   c044d busybox_unstripped

7 files changed, 116 insertions, 148 deletions

diff --git a/include/usage.h b/include/usage.h
index 682b4d760..5307d98d0 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -27,7 +27,7 @@
        "        -g GECOS        GECOS field\n" \
        "        -s SHELL        Login shell\n" \
        "        -G GROUP        Add user to existing group\n" \
-       "        -S              Create a system user (ignored)\n" \
+       "        -S              Create a system user\n" \
        "        -D              Do not assign a password\n" \
        "        -H              Do not create home directory"
 
diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index 8b1ed8000..4bd60d049 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -459,10 +459,7 @@ static void check_suid(const struct bb_applet *applet)
                         if (sct->m_applet == applet)
                                 goto found;
                 }
-                /* default: drop all privileges */
-                xsetgid(rgid);
-                xsetuid(ruid);
-                return;
+                goto check_need_suid;
  found:
                 m = sct->m_mode;
                 if (sct->m_uid == ruid)
@@ -505,13 +502,13 @@ static void check_suid(const struct bb_applet *applet)
                 }
         }
 #endif
+ check_need_suid:
 #endif
-
         if (applet->need_suid == _BB_SUID_ALWAYS) {
                 /* Real uid is not 0. If euid isn't 0 too, suid bit
                  * is most probably not set on our executable */
                 if (geteuid())
-                        bb_error_msg_and_die("applet requires root privileges!");
+                        bb_error_msg_and_die("must be suid to work properly");
         } else if (applet->need_suid == _BB_SUID_NEVER) {
                 xsetgid(rgid);  /* drop all privileges */
                 xsetuid(ruid);
diff --git a/libbb/correct_password.c b/libbb/correct_password.c
index f1793cd17..96bb10e0b 100644
--- a/libbb/correct_password.c
+++ b/libbb/correct_password.c
@@ -40,6 +40,11 @@ int correct_password(const struct passwd *pw)
 {
         char *unencrypted, *encrypted;
         const char *correct;
+#if ENABLE_FEATURE_SHADOWPASSWDS
+        /* Using _r function to avoid pulling in static buffers */
+        struct spwd spw;
+        char buffer[256];
+#endif
 
         /* fake salt. crypt() can choke otherwise. */
         correct = "aa";
@@ -50,11 +55,11 @@ int correct_password(const struct passwd *pw)
         correct = pw->pw_passwd;
 #if ENABLE_FEATURE_SHADOWPASSWDS
         if ((correct[0] == 'x' || correct[0] == '*') && !correct[1]) {
-                /* Using _r function to avoid pulling in static buffers */
-                struct spwd spw;
-                struct spwd *result;
-                char buffer[256];
-                correct = (getspnam_r(pw->pw_name, &spw, buffer, sizeof(buffer), &result)) ? "aa" : spw.sp_pwdp;
+                /* getspnam_r may return 0 yet set result to NULL.
+                 * At least glibc 2.4 does this. Be extra paranoid here. */
+                struct spwd *result = NULL;
+                int r = getspnam_r(pw->pw_name, &spw, buffer, sizeof(buffer), &result);
+                correct = (r || !result) ? "aa" : result->sp_pwdp;
         }
 #endif
 
diff --git a/loginutils/addgroup.c b/loginutils/addgroup.c
index 9b2c6790f..31e507045 100644
--- a/loginutils/addgroup.c
+++ b/loginutils/addgroup.c
@@ -56,7 +56,7 @@ static void new_group(char *group, gid_t gid)
         /* add entry to group */
         file = xfopen(bb_path_group_file, "a");
         /* group:passwd:gid:userlist */
-        fprintf(file, "%s:x:%d:\n", group, gr.gr_gid);
+        fprintf(file, "%s:x:%u:\n", group, (unsigned)gr.gr_gid);
         if (ENABLE_FEATURE_CLEAN_UP)
                 fclose(file);
 #if ENABLE_FEATURE_SHADOWPASSWDS
diff --git a/loginutils/adduser.c b/loginutils/adduser.c
index 5c624285f..e91417ad5 100644
--- a/loginutils/adduser.c
+++ b/loginutils/adduser.c
@@ -11,68 +11,47 @@
 #include "libbb.h"
 
 #define OPT_DONT_SET_PASS  (1 << 4)
+#define OPT_SYSTEM_ACCOUNT (1 << 5)
 #define OPT_DONT_MAKE_HOME (1 << 6)
 
 
 /* remix */
-/* EDR recoded such that the uid may be passed in *p */
-static int passwd_study(const char *filename, struct passwd *p)
+/* recoded such that the uid may be passed in *p */
+static void passwd_study(struct passwd *p)
 {
-        enum { min = 500, max = 65000 };
-        FILE *passwd;
-        /* We are using reentrant fgetpwent_r() in order to avoid
-         * pulling in static buffers from libc (think static build here) */
-        char buffer[256];
-        struct passwd pw;
-        struct passwd *result;
-
-        passwd = xfopen(filename, "r");
-
-        /* EDR if uid is out of bounds, set to min */
-        if ((p->pw_uid > max) || (p->pw_uid < min))
-                p->pw_uid = min;
-
-        /* stuff to do:
-         * make sure login isn't taken;
-         * find free uid and gid;
-         */
-        while (!fgetpwent_r(passwd, &pw, buffer, sizeof(buffer), &result)) {
-                if (strcmp(pw.pw_name, p->pw_name) == 0) {
-                        /* return 0; */
-                        return 1;
-                }
-                if ((pw.pw_uid >= p->pw_uid) && (pw.pw_uid < max)
-                        && (pw.pw_uid >= min)) {
-                        p->pw_uid = pw.pw_uid + 1;
-                }
-        }
+        int max;
 
-        if (p->pw_gid == 0) {
-                /* EDR check for an already existing gid */
-                while (getgrgid(p->pw_uid) != NULL)
-                        p->pw_uid++;
+        if (getpwnam(p->pw_name))
+                bb_error_msg_and_die("login '%s' is in use", p->pw_name);
 
-                /* EDR also check for an existing group definition */
-                if (getgrnam(p->pw_name) != NULL)
-                        return 3;
+        if (option_mask32 & OPT_SYSTEM_ACCOUNT) {
+                p->pw_uid = 0;
+                max = 999;
+        } else {
+                p->pw_uid = 1000;
+                max = 64999;
+        }
 
-                /* EDR create new gid always = uid */
+        /* check for a free uid (and maybe gid) */
+        while (getpwuid(p->pw_uid) || (!p->pw_gid && getgrgid(p->pw_uid)))
+                p->pw_uid++;
+        
+        if (!p->pw_gid) {
+                /* new gid = uid */
                 p->pw_gid = p->pw_uid;
+                if (getgrnam(p->pw_name))
+                        bb_error_msg_and_die("group name '%s' is in use", p->pw_name);
         }
 
-        /* EDR bounds check */
-        if ((p->pw_uid > max) || (p->pw_uid < min))
-                return 2;
-
-        /* return 1; */
-        return 0;
+        if (p->pw_uid > max)
+                bb_error_msg_and_die("no free uids left");
 }
 
 static void addgroup_wrapper(struct passwd *p)
 {
         char *cmd;
 
-        cmd = xasprintf("addgroup -g %d \"%s\"", p->pw_gid, p->pw_name);
+        cmd = xasprintf("addgroup -g %u '%s'", (unsigned)p->pw_gid, p->pw_name);
         system(cmd);
         free(cmd);
 }
@@ -84,33 +63,54 @@ static void passwd_wrapper(const char *login)
         static const char prog[] ALIGN1 = "passwd";
 
         BB_EXECLP(prog, prog, login, NULL);
-        bb_error_msg_and_die("failed to execute '%s', you must set the password for '%s' manually", prog, login);
+        bb_error_msg_and_die("cannot execute %s, you must set password manually", prog);
 }
 
-/* putpwent(3) remix */
-static int adduser(struct passwd *p)
+/*
+ * adduser will take a login_name as its first parameter.
+ * home, shell, gecos:
+ * can be customized via command-line parameters.
+ */
+int adduser_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int adduser_main(int argc, char **argv)
 {
+        struct passwd pw;
+        const char *usegroup = NULL;
         FILE *file;
-        int addgroup = !p->pw_gid;
 
-        /* make sure everything is kosher and setup uid && gid */
-        file = xfopen(bb_path_passwd_file, "a");
-        fseek(file, 0, SEEK_END);
-
-        switch (passwd_study(bb_path_passwd_file, p)) {
-                case 1:
-                        bb_error_msg_and_die("%s: login already in use", p->pw_name);
-                case 2:
-                        bb_error_msg_and_die("illegal uid or no uids left");
-                case 3:
-                        bb_error_msg_and_die("%s: group name already in use", p->pw_name);
+        /* got root? */
+        if (geteuid()) {
+                bb_error_msg_and_die(bb_msg_perm_denied_are_you_root);
         }
 
+        pw.pw_gecos = (char *)"Linux User,,,";
+        pw.pw_shell = (char *)DEFAULT_SHELL;
+        pw.pw_dir = NULL;
+
+        /* exactly one non-option arg */
+        opt_complementary = "=1";
+        getopt32(argv, "h:g:s:G:DSH", &pw.pw_dir, &pw.pw_gecos, &pw.pw_shell, &usegroup);
+        argv += optind;
+
+        /* fill in the passwd struct */
+        pw.pw_name = argv[0];
+        if (!pw.pw_dir) {
+                /* create string for $HOME if not specified already */
+                pw.pw_dir = xasprintf("/home/%s", argv[0]);
+        }
+        pw.pw_passwd = (char *)"x";
+        pw.pw_gid = usegroup ? xgroup2gid(usegroup) : 0; /* exits on failure */
+
+        /* make sure everything is kosher and setup uid && maybe gid */
+        passwd_study(&pw);
+
         /* add to passwd */
-        if (putpwent(p, file) == -1) {
+        file = xfopen(bb_path_passwd_file, "a");
+        //fseek(file, 0, SEEK_END); /* paranoia, "a" should ensure that anyway */
+        if (putpwent(&pw, file) != 0) {
                 bb_perror_nomsg_and_die();
         }
-        /* Do fclose even if !ENABLE_FEATURE_CLEAN_UP.
+        /* do fclose even if !ENABLE_FEATURE_CLEAN_UP.
          * We will exec passwd, files must be flushed & closed before that! */
         fclose(file);
 
@@ -118,13 +118,14 @@ static int adduser(struct passwd *p)
         /* add to shadow if necessary */
         file = fopen_or_warn(bb_path_shadow_file, "a");
         if (file) {
-                fseek(file, 0, SEEK_END);
-                fprintf(file, "%s:!:%ld:%d:%d:%d:::\n",
-                                p->pw_name,             /* username */
-                                time(NULL) / 86400,     /* sp->sp_lstchg */
-                                0,                      /* sp->sp_min */
-                                99999,                  /* sp->sp_max */
-                                7);                     /* sp->sp_warn */
+                //fseek(file, 0, SEEK_END);
+                fprintf(file, "%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);
         }
 #endif
@@ -132,7 +133,8 @@ static int adduser(struct passwd *p)
         /* add to group */
         /* addgroup should be responsible for dealing w/ gshadow */
         /* if using a pre-existing group, don't create one */
-        if (addgroup) addgroup_wrapper(p);
+        if (!usegroup)
+                addgroup_wrapper(&pw);
 
         /* Clear the umask for this process so it doesn't
          * screw up the permissions on the mkdir and chown. */
@@ -141,60 +143,18 @@ static int adduser(struct passwd *p)
                 /* Set the owner and group so it is owned by the new user,
                    then fix up the permissions to 2755. Can't do it before
                    since chown will clear the setgid bit */
-                if (mkdir(p->pw_dir, 0755)
-                || chown(p->pw_dir, p->pw_uid, p->pw_gid)
-                || chmod(p->pw_dir, 02755)) {
-                        bb_simple_perror_msg(p->pw_dir);
+                if (mkdir(pw.pw_dir, 0755)
+                 || chown(pw.pw_dir, pw.pw_uid, pw.pw_gid)
+                 || chmod(pw.pw_dir, 02755) /* set setgid bit on homedir */
+                ) { 
+                        bb_simple_perror_msg(pw.pw_dir);
                 }
         }
 
         if (!(option_mask32 & OPT_DONT_SET_PASS)) {
                 /* interactively set passwd */
-                passwd_wrapper(p->pw_name);
+                passwd_wrapper(pw.pw_name);
         }
 
         return 0;
 }
-
-/*
- * adduser will take a login_name as its first parameter.
- *
- * home
- * shell
- * gecos
- *
- * can be customized via command-line parameters.
- */
-int adduser_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-int adduser_main(int argc, char **argv)
-{
-        struct passwd pw;
-        const char *usegroup = NULL;
-
-        /* got root? */
-        if (geteuid()) {
-                bb_error_msg_and_die(bb_msg_perm_denied_are_you_root);
-        }
-
-        pw.pw_gecos = (char *)"Linux User,,,";
-        pw.pw_shell = (char *)DEFAULT_SHELL;
-        pw.pw_dir = NULL;
-
-        /* exactly one non-option arg */
-        opt_complementary = "=1";
-        getopt32(argv, "h:g:s:G:DSH", &pw.pw_dir, &pw.pw_gecos, &pw.pw_shell, &usegroup);
-        argv += optind;
-
-        /* create a passwd struct */
-        pw.pw_name = argv[0];
-        if (!pw.pw_dir) {
-                /* create string for $HOME if not specified already */
-                pw.pw_dir = xasprintf("/home/%s", argv[0]);
-        }
-        pw.pw_passwd = (char *)"x";
-        pw.pw_uid = 0;
-        pw.pw_gid = usegroup ? xgroup2gid(usegroup) : 0; /* exits on failure */
-
-        /* grand finale */
-        return adduser(&pw);
-}
diff --git a/loginutils/passwd.c b/loginutils/passwd.c
index 99afde223..0842b71bf 100644
--- a/loginutils/passwd.c
+++ b/loginutils/passwd.c
@@ -93,11 +93,9 @@ int passwd_main(int argc, char **argv)
         uid_t myuid;
         struct rlimit rlimit_fsize;
         char c;
-
 #if ENABLE_FEATURE_SHADOWPASSWDS
         /* Using _r function to avoid pulling in static buffers */
         struct spwd spw;
-        struct spwd *result;
         char buffer[256];
 #endif
 
@@ -128,16 +126,19 @@ int passwd_main(int argc, char **argv)
         }
 
 #if ENABLE_FEATURE_SHADOWPASSWDS
-        /* getspnam_r() can lie! Even if user isn't in shadow, it can
-         * return success (pwd field was seen set to "!" in this case) */
-        if (getspnam_r(pw->pw_name, &spw, buffer, sizeof(buffer), &result)
-         || LONE_CHAR(spw.sp_pwdp, '!')) {
-                /* LOGMODE_BOTH */
-                bb_error_msg("no record of %s in %s, using %s",
-                                name, bb_path_shadow_file,
-                                bb_path_passwd_file);
-        } else {
-                pw->pw_passwd = spw.sp_pwdp;
+        {
+                /* getspnam_r may return 0 yet set result to NULL.
+                 * At least glibc 2.4 does this. Be extra paranoid here. */
+                struct spwd *result = NULL;
+                if (getspnam_r(pw->pw_name, &spw, buffer, sizeof(buffer), &result)
+                 || !result || strcmp(result->sp_namp, pw->pw_name) != 0) {
+                        /* LOGMODE_BOTH */
+                        bb_error_msg("no record of %s in %s, using %s",
+                                        name, bb_path_shadow_file,
+                                        bb_path_passwd_file);
+                } else {
+                        pw->pw_passwd = result->sp_pwdp;
+                }
         }
 #endif
 
@@ -161,7 +162,7 @@ int passwd_main(int argc, char **argv)
                 newp = xasprintf("!%s", pw->pw_passwd);
         } else if (opt & OPT_unlock) {
                 if (c) goto skip; /* not '!' */
-                /* pw->pw_passwd pints to static storage,
+                /* pw->pw_passwd points to static storage,
                  * strdup'ing to avoid nasty surprizes */
                 newp = xstrdup(&pw->pw_passwd[1]);
         } else if (opt & OPT_delete) {
diff --git a/loginutils/sulogin.c b/loginutils/sulogin.c
index f633fbbf1..f1545b78f 100644
--- a/loginutils/sulogin.c
+++ b/loginutils/sulogin.c
@@ -44,7 +44,6 @@ int sulogin_main(int argc, char **argv)
         /* Using _r function to avoid pulling in static buffers */
         char buffer[256];
         struct spwd spw;
-        struct spwd *result;
 #endif
 
         logmode = LOGMODE_BOTH;
@@ -83,10 +82,16 @@ int sulogin_main(int argc, char **argv)
         }
 
 #if ENABLE_FEATURE_SHADOWPASSWDS
-        if (getspnam_r(pwd->pw_name, &spw, buffer, sizeof(buffer), &result)) {
-                goto auth_error;
+        {
+                /* getspnam_r may return 0 yet set result to NULL.
+                 * At least glibc 2.4 does this. Be extra paranoid here. */
+                struct spwd *result = NULL;
+                int r = getspnam_r(pwd->pw_name, &spw, buffer, sizeof(buffer), &result);
+                if (r || !result) {
+                        goto auth_error;
+                }
+                pwd->pw_passwd = result->sp_pwdp;
         }
-        pwd->pw_passwd = spw.sp_pwdp;
 #endif
 
         while (1) {