482 lines
12 KiB
C
482 lines
12 KiB
C
/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <alloca.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <grp.h>
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#include <pwd.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "missing.h"
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#include "alloc-util.h"
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#include "fd-util.h"
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#include "formats-util.h"
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#include "macro.h"
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#include "parse-util.h"
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#include "path-util.h"
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#include "string-util.h"
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#include "user-util.h"
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bool uid_is_valid(uid_t uid) {
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/* Some libc APIs use UID_INVALID as special placeholder */
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if (uid == (uid_t) UINT32_C(0xFFFFFFFF))
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return false;
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/* A long time ago UIDs where 16bit, hence explicitly avoid the 16bit -1 too */
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if (uid == (uid_t) UINT32_C(0xFFFF))
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return false;
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return true;
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}
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int parse_uid(const char *s, uid_t *ret) {
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uint32_t uid = 0;
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int r;
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assert(s);
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assert_cc(sizeof(uid_t) == sizeof(uint32_t));
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r = safe_atou32(s, &uid);
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if (r < 0)
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return r;
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if (!uid_is_valid(uid))
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return -ENXIO; /* we return ENXIO instead of EINVAL
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* here, to make it easy to distuingish
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* invalid numeric uids from invalid
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* strings. */
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if (ret)
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*ret = uid;
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return 0;
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}
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char* getlogname_malloc(void) {
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uid_t uid;
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struct stat st;
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if (isatty(STDIN_FILENO) && fstat(STDIN_FILENO, &st) >= 0)
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uid = st.st_uid;
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else
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uid = getuid();
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return uid_to_name(uid);
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}
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char *getusername_malloc(void) {
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const char *e;
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e = getenv("USER");
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if (e)
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return strdup(e);
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return uid_to_name(getuid());
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}
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int get_user_creds(
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const char **username,
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uid_t *uid, gid_t *gid,
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const char **home,
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const char **shell) {
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struct passwd *p;
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uid_t u;
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assert(username);
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assert(*username);
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/* We enforce some special rules for uid=0: in order to avoid
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* NSS lookups for root we hardcode its data. */
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if (streq(*username, "root") || streq(*username, "0")) {
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*username = "root";
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if (uid)
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*uid = 0;
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if (gid)
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*gid = 0;
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if (home)
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*home = "/root";
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if (shell)
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*shell = "/bin/sh";
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return 0;
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}
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if (parse_uid(*username, &u) >= 0) {
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errno = 0;
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p = getpwuid(u);
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/* If there are multiple users with the same id, make
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* sure to leave $USER to the configured value instead
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* of the first occurrence in the database. However if
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* the uid was configured by a numeric uid, then let's
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* pick the real username from /etc/passwd. */
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if (p)
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*username = p->pw_name;
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} else {
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errno = 0;
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p = getpwnam(*username);
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}
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if (!p)
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return errno > 0 ? -errno : -ESRCH;
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if (uid) {
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if (!uid_is_valid(p->pw_uid))
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return -EBADMSG;
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*uid = p->pw_uid;
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}
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if (gid) {
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if (!gid_is_valid(p->pw_gid))
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return -EBADMSG;
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*gid = p->pw_gid;
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}
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if (home)
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*home = p->pw_dir;
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if (shell)
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*shell = p->pw_shell;
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return 0;
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}
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int get_group_creds(const char **groupname, gid_t *gid) {
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struct group *g;
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gid_t id;
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assert(groupname);
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/* We enforce some special rules for gid=0: in order to avoid
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* NSS lookups for root we hardcode its data. */
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if (streq(*groupname, "root") || streq(*groupname, "0")) {
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*groupname = "root";
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if (gid)
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*gid = 0;
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return 0;
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}
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if (parse_gid(*groupname, &id) >= 0) {
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errno = 0;
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g = getgrgid(id);
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if (g)
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*groupname = g->gr_name;
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} else {
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errno = 0;
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g = getgrnam(*groupname);
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}
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if (!g)
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return errno > 0 ? -errno : -ESRCH;
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if (gid) {
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if (!gid_is_valid(g->gr_gid))
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return -EBADMSG;
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*gid = g->gr_gid;
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}
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return 0;
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}
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char* uid_to_name(uid_t uid) {
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char *ret;
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int r;
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/* Shortcut things to avoid NSS lookups */
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if (uid == 0)
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return strdup("root");
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if (uid_is_valid(uid)) {
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long bufsize;
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bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
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if (bufsize <= 0)
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bufsize = 4096;
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for (;;) {
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struct passwd pwbuf, *pw = NULL;
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_cleanup_free_ char *buf = NULL;
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buf = malloc(bufsize);
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if (!buf)
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return NULL;
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r = getpwuid_r(uid, &pwbuf, buf, (size_t) bufsize, &pw);
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if (r == 0 && pw)
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return strdup(pw->pw_name);
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if (r != ERANGE)
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break;
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bufsize *= 2;
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}
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}
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if (asprintf(&ret, UID_FMT, uid) < 0)
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return NULL;
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return ret;
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}
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char* gid_to_name(gid_t gid) {
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char *ret;
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int r;
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if (gid == 0)
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return strdup("root");
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if (gid_is_valid(gid)) {
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long bufsize;
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bufsize = sysconf(_SC_GETGR_R_SIZE_MAX);
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if (bufsize <= 0)
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bufsize = 4096;
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for (;;) {
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struct group grbuf, *gr = NULL;
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_cleanup_free_ char *buf = NULL;
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buf = malloc(bufsize);
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if (!buf)
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return NULL;
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r = getgrgid_r(gid, &grbuf, buf, (size_t) bufsize, &gr);
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if (r == 0 && gr)
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return strdup(gr->gr_name);
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if (r != ERANGE)
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break;
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bufsize *= 2;
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}
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}
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if (asprintf(&ret, GID_FMT, gid) < 0)
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return NULL;
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return ret;
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}
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int in_gid(gid_t gid) {
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gid_t *gids;
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int ngroups_max, r, i;
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if (getgid() == gid)
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return 1;
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if (getegid() == gid)
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return 1;
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if (!gid_is_valid(gid))
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return -EINVAL;
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ngroups_max = sysconf(_SC_NGROUPS_MAX);
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assert(ngroups_max > 0);
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gids = alloca(sizeof(gid_t) * ngroups_max);
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r = getgroups(ngroups_max, gids);
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if (r < 0)
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return -errno;
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for (i = 0; i < r; i++)
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if (gids[i] == gid)
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return 1;
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return 0;
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}
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int in_group(const char *name) {
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int r;
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gid_t gid;
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r = get_group_creds(&name, &gid);
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if (r < 0)
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return r;
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return in_gid(gid);
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}
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int get_home_dir(char **_h) {
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struct passwd *p;
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const char *e;
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char *h;
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uid_t u;
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assert(_h);
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/* Take the user specified one */
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e = secure_getenv("HOME");
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if (e && path_is_absolute(e)) {
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h = strdup(e);
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if (!h)
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return -ENOMEM;
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*_h = h;
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return 0;
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}
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/* Hardcode home directory for root to avoid NSS */
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u = getuid();
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if (u == 0) {
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h = strdup("/root");
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if (!h)
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return -ENOMEM;
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*_h = h;
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return 0;
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}
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/* Check the database... */
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errno = 0;
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p = getpwuid(u);
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if (!p)
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return errno > 0 ? -errno : -ESRCH;
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if (!path_is_absolute(p->pw_dir))
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return -EINVAL;
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h = strdup(p->pw_dir);
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if (!h)
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return -ENOMEM;
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*_h = h;
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return 0;
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}
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int get_shell(char **_s) {
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struct passwd *p;
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const char *e;
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char *s;
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uid_t u;
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assert(_s);
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/* Take the user specified one */
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e = getenv("SHELL");
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if (e) {
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s = strdup(e);
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if (!s)
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return -ENOMEM;
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*_s = s;
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return 0;
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}
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/* Hardcode home directory for root to avoid NSS */
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u = getuid();
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if (u == 0) {
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s = strdup("/bin/sh");
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if (!s)
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return -ENOMEM;
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*_s = s;
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return 0;
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}
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/* Check the database... */
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errno = 0;
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p = getpwuid(u);
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if (!p)
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return errno > 0 ? -errno : -ESRCH;
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if (!path_is_absolute(p->pw_shell))
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return -EINVAL;
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s = strdup(p->pw_shell);
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if (!s)
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return -ENOMEM;
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*_s = s;
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return 0;
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}
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int reset_uid_gid(void) {
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if (setgroups(0, NULL) < 0)
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return -errno;
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if (setresgid(0, 0, 0) < 0)
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return -errno;
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if (setresuid(0, 0, 0) < 0)
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return -errno;
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return 0;
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}
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int take_etc_passwd_lock(const char *root) {
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struct flock flock = {
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.l_type = F_WRLCK,
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.l_whence = SEEK_SET,
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.l_start = 0,
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.l_len = 0,
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};
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const char *path;
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int fd, r;
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/* This is roughly the same as lckpwdf(), but not as awful. We
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* don't want to use alarm() and signals, hence we implement
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* our own trivial version of this.
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*
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* Note that shadow-utils also takes per-database locks in
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* addition to lckpwdf(). However, we don't given that they
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* are redundant as they invoke lckpwdf() first and keep
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* it during everything they do. The per-database locks are
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* awfully racy, and thus we just won't do them. */
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if (root)
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path = prefix_roota(root, "/etc/.pwd.lock");
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else
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path = "/etc/.pwd.lock";
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fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0600);
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if (fd < 0)
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return -errno;
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r = fcntl(fd, F_SETLKW, &flock);
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if (r < 0) {
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safe_close(fd);
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return -errno;
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}
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return fd;
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}
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