f7ed43a656
Document the need for the setuid bit and how to set it. Explain why it isn't set by default, and suggest simply adding users to groups instead. PR: docs/167741 MFC after: 3 weeks
312 lines
6.7 KiB
C
312 lines
6.7 KiB
C
/*-
|
|
* Copyright (c) 2002 Tim J. Robbins.
|
|
* All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*/
|
|
|
|
/*
|
|
* newgrp -- change to a new group
|
|
*/
|
|
|
|
#include <sys/cdefs.h>
|
|
__FBSDID("$FreeBSD$");
|
|
|
|
#include <sys/types.h>
|
|
|
|
#include <err.h>
|
|
#include <errno.h>
|
|
#include <grp.h>
|
|
#include <libgen.h>
|
|
#include <limits.h>
|
|
#include <login_cap.h>
|
|
#include <paths.h>
|
|
#include <pwd.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <unistd.h>
|
|
|
|
static void addgroup(const char *grpname);
|
|
static void doshell(void);
|
|
static int inarray(gid_t, const gid_t[], int);
|
|
static void loginshell(void);
|
|
static void restoregrps(void);
|
|
static void usage(void);
|
|
|
|
static struct passwd *pwd;
|
|
static uid_t euid;
|
|
|
|
extern char **environ;
|
|
|
|
/* Manipulate effective user ID. */
|
|
#define PRIV_START do { \
|
|
if (seteuid(euid) < 0) \
|
|
err(1, "seteuid"); \
|
|
} while (0)
|
|
#define PRIV_END do { \
|
|
if (seteuid(getuid()) < 0) \
|
|
err(1, "seteuid"); \
|
|
} while (0)
|
|
|
|
int
|
|
main(int argc, char *argv[])
|
|
{
|
|
int ch, login;
|
|
|
|
if ((euid = geteuid()) != 0)
|
|
warnx("need root permissions to function properly, check setuid bit");
|
|
if (seteuid(getuid()) < 0)
|
|
err(1, "seteuid");
|
|
|
|
if ((pwd = getpwuid(getuid())) == NULL)
|
|
errx(1, "unknown user");
|
|
|
|
login = 0;
|
|
while ((ch = getopt(argc, argv, "-l")) != -1) {
|
|
switch (ch) {
|
|
case '-': /* Obsolescent */
|
|
case 'l':
|
|
login = 1;
|
|
break;
|
|
default:
|
|
usage();
|
|
}
|
|
}
|
|
argc -= optind;
|
|
argv += optind;
|
|
|
|
switch (argc) {
|
|
case 0:
|
|
restoregrps();
|
|
break;
|
|
case 1:
|
|
addgroup(*argv);
|
|
break;
|
|
default:
|
|
usage();
|
|
}
|
|
|
|
if (seteuid(euid) < 0)
|
|
err(1, "seteuid");
|
|
if (setuid(getuid()) < 0)
|
|
err(1, "setuid");
|
|
|
|
if (login)
|
|
loginshell();
|
|
else
|
|
doshell();
|
|
|
|
/*NOTREACHED*/
|
|
exit(1);
|
|
}
|
|
|
|
static void
|
|
usage(void)
|
|
{
|
|
|
|
fprintf(stderr, "usage: newgrp [-l] [group]\n");
|
|
exit(1);
|
|
}
|
|
|
|
static void
|
|
restoregrps(void)
|
|
{
|
|
int initres, setres;
|
|
|
|
PRIV_START;
|
|
initres = initgroups(pwd->pw_name, pwd->pw_gid);
|
|
setres = setgid(pwd->pw_gid);
|
|
PRIV_END;
|
|
|
|
if (initres < 0)
|
|
warn("initgroups");
|
|
if (setres < 0)
|
|
warn("setgid");
|
|
}
|
|
|
|
static void
|
|
addgroup(const char *grpname)
|
|
{
|
|
gid_t *grps;
|
|
long lgid, ngrps_max;
|
|
int dbmember, i, ngrps;
|
|
gid_t egid;
|
|
struct group *grp;
|
|
char *ep, *pass, *cryptpw;
|
|
char **p;
|
|
|
|
egid = getegid();
|
|
|
|
/* Try it as a group name, then a group id. */
|
|
if ((grp = getgrnam(grpname)) == NULL)
|
|
if ((lgid = strtol(grpname, &ep, 10)) <= 0 || *ep != '\0' ||
|
|
(grp = getgrgid((gid_t)lgid)) == NULL ) {
|
|
warnx("%s: bad group name", grpname);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* If the user is not a member of the requested group and the group
|
|
* has a password, prompt and check it.
|
|
*/
|
|
dbmember = 0;
|
|
if (pwd->pw_gid == grp->gr_gid)
|
|
dbmember = 1;
|
|
for (p = grp->gr_mem; *p != NULL; p++)
|
|
if (strcmp(*p, pwd->pw_name) == 0) {
|
|
dbmember = 1;
|
|
break;
|
|
}
|
|
if (!dbmember && *grp->gr_passwd != '\0' && getuid() != 0) {
|
|
pass = getpass("Password:");
|
|
if (pass == NULL)
|
|
return;
|
|
cryptpw = crypt(pass, grp->gr_passwd);
|
|
if (cryptpw == NULL || strcmp(grp->gr_passwd, cryptpw) != 0) {
|
|
fprintf(stderr, "Sorry\n");
|
|
return;
|
|
}
|
|
}
|
|
|
|
ngrps_max = sysconf(_SC_NGROUPS_MAX) + 1;
|
|
if ((grps = malloc(sizeof(gid_t) * ngrps_max)) == NULL)
|
|
err(1, "malloc");
|
|
if ((ngrps = getgroups(ngrps_max, (gid_t *)grps)) < 0) {
|
|
warn("getgroups");
|
|
goto end;
|
|
}
|
|
|
|
/* Remove requested gid from supp. list if it exists. */
|
|
if (grp->gr_gid != egid && inarray(grp->gr_gid, grps, ngrps)) {
|
|
for (i = 0; i < ngrps; i++)
|
|
if (grps[i] == grp->gr_gid)
|
|
break;
|
|
ngrps--;
|
|
memmove(&grps[i], &grps[i + 1], (ngrps - i) * sizeof(gid_t));
|
|
PRIV_START;
|
|
if (setgroups(ngrps, (const gid_t *)grps) < 0) {
|
|
PRIV_END;
|
|
warn("setgroups");
|
|
goto end;
|
|
}
|
|
PRIV_END;
|
|
}
|
|
|
|
PRIV_START;
|
|
if (setgid(grp->gr_gid)) {
|
|
PRIV_END;
|
|
warn("setgid");
|
|
goto end;
|
|
}
|
|
PRIV_END;
|
|
grps[0] = grp->gr_gid;
|
|
|
|
/* Add old effective gid to supp. list if it does not exist. */
|
|
if (egid != grp->gr_gid && !inarray(egid, grps, ngrps)) {
|
|
if (ngrps == ngrps_max)
|
|
warnx("too many groups");
|
|
else {
|
|
grps[ngrps++] = egid;
|
|
PRIV_START;
|
|
if (setgroups(ngrps, (const gid_t *)grps)) {
|
|
PRIV_END;
|
|
warn("setgroups");
|
|
goto end;
|
|
}
|
|
PRIV_END;
|
|
}
|
|
}
|
|
end:
|
|
free(grps);
|
|
}
|
|
|
|
static int
|
|
inarray(gid_t gid, const gid_t grps[], int ngrps)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < ngrps; i++)
|
|
if (grps[i] == gid)
|
|
return (1);
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Set the environment to what would be expected if the user logged in
|
|
* again; this performs the same steps as su(1)'s -l option.
|
|
*/
|
|
static void
|
|
loginshell(void)
|
|
{
|
|
char *args[2], **cleanenv, *term, *ticket;
|
|
const char *shell;
|
|
login_cap_t *lc;
|
|
|
|
shell = pwd->pw_shell;
|
|
if (*shell == '\0')
|
|
shell = _PATH_BSHELL;
|
|
if (chdir(pwd->pw_dir) < 0) {
|
|
warn("%s", pwd->pw_dir);
|
|
chdir("/");
|
|
}
|
|
|
|
term = getenv("TERM");
|
|
ticket = getenv("KRBTKFILE");
|
|
|
|
if ((cleanenv = calloc(20, sizeof(char *))) == NULL)
|
|
err(1, "calloc");
|
|
*cleanenv = NULL;
|
|
environ = cleanenv;
|
|
|
|
lc = login_getpwclass(pwd);
|
|
setusercontext(lc, pwd, pwd->pw_uid,
|
|
LOGIN_SETPATH|LOGIN_SETUMASK|LOGIN_SETENV);
|
|
login_close(lc);
|
|
setenv("USER", pwd->pw_name, 1);
|
|
setenv("SHELL", shell, 1);
|
|
setenv("HOME", pwd->pw_dir, 1);
|
|
if (term != NULL)
|
|
setenv("TERM", term, 1);
|
|
if (ticket != NULL)
|
|
setenv("KRBTKFILE", ticket, 1);
|
|
|
|
if (asprintf(args, "-%s", basename(shell)) < 0)
|
|
err(1, "asprintf");
|
|
args[1] = NULL;
|
|
|
|
execv(shell, args);
|
|
err(1, "%s", shell);
|
|
}
|
|
|
|
static void
|
|
doshell(void)
|
|
{
|
|
const char *shell;
|
|
|
|
shell = pwd->pw_shell;
|
|
if (*shell == '\0')
|
|
shell = _PATH_BSHELL;
|
|
execl(shell, basename(shell), (char *)NULL);
|
|
err(1, "%s", shell);
|
|
}
|