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Add the newgrp(1) utility, which changes groups. This is required by

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the POSIX.2 UPE.

PR:		36190
Reviewed by:	-standards, silence on -audit
This commit is contained in:
Tim J. Robbins 2002-05-28 05:05:28 +00:00
parent b0694f6170
commit 29f48d6256
3 changed files with 411 additions and 0 deletions
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12
usr.bin/newgrp/Makefile Normal file
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# $FreeBSD$
PROG= newgrp
DPADD= ${LIBCRYPT} ${LIBUTIL}
LDADD= -lcrypt -lutil
.if defined(ENABLE_SUID_NEWGRP) && ${ENABLE_SUID_NEWGRP} == "true"
BINMODE= 4555
INSTALLFLAGS= -fschg
.endif
.include <bsd.prog.mk>

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usr.bin/newgrp/newgrp.1 Normal file
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.\" 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.
.\"
.\" $FreeBSD$
.\"
.Dd May 23, 2002
.Dt NEWGRP 1
.Os
.Sh NAME
.Nm newgrp
.Nd change to a new group
.Sh SYNOPSIS
.Nm
.Op Fl l
.Op Ar group
.Sh DESCRIPTION
The
.Nm
utility creates a new shell execution environment with modified
real and effective group IDs.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl l
Simulate a full login.
The environment and umask are set to what would be expected if the user
actually logged in again.
.El
.Pp
If the
.Ar group
operand is present, a new shell is started with the specified effective
and real group IDs.
The user will be prompted for a password if they are not a member of the
specified group.
.Pp
Otherwise, the real, effective and supplementary group IDs are restored to
those from the current user's password database entry.
.Sh DIAGNOSTICS
The
.Nm
utility attempts to start the shell regardless of whether group ID's
were successfully changed.
.Pp
If an error occurs and the shell cannot be started,
.Nm
exits >0.
Otherwise, the exit status of
.Nm
is the exit status of the shell.
.Sh SEE ALSO
.Xr csh 1 ,
.Xr groups 1 ,
.Xr login 1 ,
.Xr sh 1 ,
.Xr su 1 ,
.Xr umask 1 ,
.Xr group 5 ,
.Xr passwd 5 ,
.Xr environ 7
.Sh STANDARDS
The
.Nm
utility conforms to
.St -p1003.1-2001 .
.Sh HISTORY
A
.Nm
utility appeared in
.At v6 .
.Sh BUGS
Group passwords are inherently insecure as there is no way to stop
users obtaining the crypted passwords from the group database.
Their use is discouraged.

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usr.bin/newgrp/newgrp.c Normal file
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/*-
* 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;
euid = geteuid();
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("setgroups");
}
static void
addgroup(const char *grpname)
{
gid_t grps[NGROUPS_MAX];
long lgid;
int dbmember, i, ngrps;
gid_t egid;
struct group *grp;
char *ep, *pass;
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 ||
strcmp(grp->gr_passwd, crypt(pass, grp->gr_passwd)) != 0) {
fprintf(stderr, "Sorry\n");
return;
}
}
if ((ngrps = getgroups(NGROUPS_MAX, (gid_t *)grps)) < 0) {
warn("getgroups");
return;
}
/* 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");
return;
}
PRIV_END;
}
PRIV_START;
if (setgid(grp->gr_gid)) {
PRIV_END;
warn("setgid");
return;
}
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 == NGROUPS_MAX)
warnx("too many groups");
else {
grps[ngrps++] = egid;
PRIV_START;
if (setgroups(ngrps, (const gid_t *)grps)) {
PRIV_END;
warn("setgroups");
return;
}
PRIV_END;
}
}
}
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), NULL);
err(1, "%s", shell);
}