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NetBSD/usr.bin/su/su_pam.c

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/* $NetBSD: su_pam.c,v 1.21 2018/02/26 00:05:05 htodd Exp $ */
/*
* Copyright (c) 1988 The Regents of the University of California.
* 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.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*/
#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1988\
The Regents of the University of California. All rights reserved.");
#endif /* not lint */
#ifndef lint
#if 0
static char sccsid[] = "@(#)su.c 8.3 (Berkeley) 4/2/94";*/
#else
__RCSID("$NetBSD: su_pam.c,v 1.21 2018/02/26 00:05:05 htodd Exp $");
#endif
#endif /* not lint */
#include <sys/param.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/wait.h>
#include <err.h>
#include <errno.h>
#include <grp.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <time.h>
#include <tzfile.h>
#include <unistd.h>
#include <util.h>
#include <login_cap.h>
#include <security/pam_appl.h>
#include <security/openpam.h> /* for openpam_ttyconv() */
#ifdef ALLOW_GROUP_CHANGE
#include "grutil.h"
#endif
#include "suutil.h"
static const struct pam_conv pamc = { &openpam_ttyconv, NULL };
#define ARGSTRX "-dflm"
#ifdef LOGIN_CAP
#define ARGSTR ARGSTRX "c:"
#else
#define ARGSTR ARGSTRX
#endif
static void logit(const char *, ...) __printflike(1, 2);
static const char *
safe_pam_strerror(pam_handle_t *pamh, int pam_err) {
const char *msg;
if ((msg = pam_strerror(pamh, pam_err)) != NULL)
return msg;
static char buf[1024];
snprintf(buf, sizeof(buf), "Unknown pam error %d", pam_err);
return buf;
}
int
main(int argc, char **argv)
{
extern char **environ;
struct passwd *pwd, pwres;
char *p;
uid_t ruid;
int asme, ch, asthem, fastlogin, prio, gohome;
u_int setwhat;
enum { UNSET, YES, NO } iscsh = UNSET;
const char *user, *shell, *avshell;
char *username, *class;
char **np;
char shellbuf[MAXPATHLEN], avshellbuf[MAXPATHLEN];
int pam_err;
char hostname[MAXHOSTNAMELEN];
char *tty;
const char *func;
const void *newuser;
login_cap_t *lc;
pam_handle_t *pamh = NULL;
char pwbuf[1024];
#ifdef PAM_DEBUG
extern int _openpam_debug;
_openpam_debug = 1;
#endif
#ifdef ALLOW_GROUP_CHANGE
char *gname;
#endif
(void)setprogname(argv[0]);
asme = asthem = fastlogin = 0;
gohome = 1;
shell = class = NULL;
while ((ch = getopt(argc, argv, ARGSTR)) != -1)
switch((char)ch) {
case 'c':
class = optarg;
break;
case 'd':
asme = 0;
asthem = 1;
gohome = 0;
break;
case 'f':
fastlogin = 1;
break;
case '-':
case 'l':
asme = 0;
asthem = 1;
break;
case 'm':
asme = 1;
asthem = 0;
break;
case '?':
default:
(void)fprintf(stderr,
#ifdef ALLOW_GROUP_CHANGE
"Usage: %s [%s] [login[:group] [shell arguments]]\n",
#else
"Usage: %s [%s] [login [shell arguments]]\n",
#endif
getprogname(), ARGSTR);
exit(EXIT_FAILURE);
}
argv += optind;
/* Lower the priority so su runs faster */
errno = 0;
prio = getpriority(PRIO_PROCESS, 0);
if (errno)
prio = 0;
if (prio > -2)
(void)setpriority(PRIO_PROCESS, 0, -2);
openlog("su", 0, LOG_AUTH);
/* get current login name and shell */
ruid = getuid();
username = getlogin();
if (username == NULL ||
getpwnam_r(username, &pwres, pwbuf, sizeof(pwbuf), &pwd) != 0 ||
pwd == NULL || pwd->pw_uid != ruid) {
if (getpwuid_r(ruid, &pwres, pwbuf, sizeof(pwbuf), &pwd) != 0)
pwd = NULL;
}
if (pwd == NULL)
errx(EXIT_FAILURE, "who are you?");
username = estrdup(pwd->pw_name);
if (asme) {
if (pwd->pw_shell && *pwd->pw_shell) {
(void)estrlcpy(shellbuf, pwd->pw_shell, sizeof(shellbuf));
shell = shellbuf;
} else {
shell = _PATH_BSHELL;
iscsh = NO;
}
}
/* get target login information, default to root */
user = *argv ? *argv : "root";
np = *argv ? argv : argv - 1;
#ifdef ALLOW_GROUP_CHANGE
if ((p = strchr(user, ':')) != NULL) {
*p = '\0';
gname = ++p;
}
else
gname = NULL;
#ifdef ALLOW_EMPTY_USER
if (user[0] == '\0')
user = username;
#endif
#endif
if (getpwnam_r(user, &pwres, pwbuf, sizeof(pwbuf), &pwd) != 0 ||
pwd == NULL)
errx(EXIT_FAILURE, "unknown login %s", user);
/*
* PAM initialization
*/
#define PAM_END(msg) do { func = msg; goto done;} /* NOTREACHED */ while (/*CONSTCOND*/0)
if ((pam_err = pam_start("su", user, &pamc, &pamh)) != PAM_SUCCESS) {
if (pamh != NULL)
PAM_END("pam_start");
/* Things went really bad... */
syslog(LOG_ERR, "pam_start failed: %s",
safe_pam_strerror(pamh, pam_err));
errx(EXIT_FAILURE, "pam_start failed");
}
#define PAM_END_ITEM(item) PAM_END("pam_set_item(" # item ")")
#define PAM_SET_ITEM(item, var) \
if ((pam_err = pam_set_item(pamh, (item), (var))) != PAM_SUCCESS) \
PAM_END_ITEM(item)
/*
* Fill hostname, username and tty
*/
PAM_SET_ITEM(PAM_RUSER, username);
if (gethostname(hostname, sizeof(hostname)) != -1)
PAM_SET_ITEM(PAM_RHOST, hostname);
if ((tty = ttyname(STDERR_FILENO)) != NULL)
PAM_SET_ITEM(PAM_TTY, tty);
/*
* Authentication
*/
if ((pam_err = pam_authenticate(pamh, 0)) != PAM_SUCCESS) {
syslog(LOG_WARNING, "BAD SU %s to %s%s: %s",
username, user, ontty(), safe_pam_strerror(pamh, pam_err));
(void)pam_end(pamh, pam_err);
errx(EXIT_FAILURE, "Sorry: %s", safe_pam_strerror(NULL, pam_err));
}
/*
* Authorization
*/
switch(pam_err = pam_acct_mgmt(pamh, 0)) {
case PAM_NEW_AUTHTOK_REQD:
pam_err = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
if (pam_err != PAM_SUCCESS)
PAM_END("pam_chauthok");
break;
case PAM_SUCCESS:
break;
default:
PAM_END("pam_acct_mgmt");
break;
}
/*
* pam_authenticate might have changed the target user.
* refresh pwd and user
*/
pam_err = pam_get_item(pamh, PAM_USER, &newuser);
if (pam_err != PAM_SUCCESS) {
syslog(LOG_WARNING,
"pam_get_item(PAM_USER): %s", safe_pam_strerror(pamh, pam_err));
} else {
user = (char *)__UNCONST(newuser);
if (getpwnam_r(user, &pwres, pwbuf, sizeof(pwbuf), &pwd) != 0 ||
pwd == NULL) {
(void)pam_end(pamh, pam_err);
syslog(LOG_ERR, "unknown login: %s", username);
errx(EXIT_FAILURE, "unknown login: %s", username);
}
}
#define ERRX_PAM_END(args) do { \
(void)pam_end(pamh, pam_err); \
errx args; \
} while (/* CONSTCOND */0)
#define ERR_PAM_END(args) do { \
(void)pam_end(pamh, pam_err); \
err args; \
} while (/* CONSTCOND */0)
/* force the usage of specified class */
if (class) {
if (ruid)
ERRX_PAM_END((EXIT_FAILURE, "Only root may use -c"));
pwd->pw_class = class;
}
if ((lc = login_getclass(pwd->pw_class)) == NULL)
ERRX_PAM_END((EXIT_FAILURE,
"Unknown class %s\n", pwd->pw_class));
if (asme) {
/* if asme and non-standard target shell, must be root */
if (chshell(pwd->pw_shell) == 0 && ruid)
ERRX_PAM_END((EXIT_FAILURE,
"permission denied (shell)."));
} else if (pwd->pw_shell && *pwd->pw_shell) {
shell = pwd->pw_shell;
iscsh = UNSET;
} else {
shell = _PATH_BSHELL;
iscsh = NO;
}
if ((p = strrchr(shell, '/')) != NULL)
avshell = p + 1;
else
avshell = shell;
/* if we're forking a csh, we want to slightly muck the args */
if (iscsh == UNSET)
iscsh = strstr(avshell, "csh") ? YES : NO;
/*
* Initialize the supplemental groups before pam gets to them,
* so that other pam modules get a chance to add more when
* we do setcred. Note, we don't relinquish our set-userid yet
*/
/* if we aren't changing users, keep the current group members */
if (ruid != pwd->pw_uid &&
setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) == -1)
ERR_PAM_END((EXIT_FAILURE, "setting user context"));
#ifdef ALLOW_GROUP_CHANGE
addgroup(lc, gname, pwd, ruid, "Group Password:");
#endif
if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS)
PAM_END("pam_setcred");
/*
* Manage session.
*/
if (asthem) {
pid_t pid, xpid;
int status = 1;
struct sigaction sa, sa_int, sa_pipe, sa_quit;
int fds[2];
if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS)
PAM_END("pam_open_session");
/*
* In order to call pam_close_session after the
* command terminates, we need to fork.
*/
sa.sa_flags = SA_RESTART;
sa.sa_handler = SIG_IGN;
(void)sigemptyset(&sa.sa_mask);
(void)sigaction(SIGINT, &sa, &sa_int);
(void)sigaction(SIGQUIT, &sa, &sa_quit);
(void)sigaction(SIGPIPE, &sa, &sa_pipe);
sa.sa_handler = SIG_DFL;
(void)sigaction(SIGTSTP, &sa, NULL);
/*
* Use a pipe to guarantee the order of execution of
* the parent and the child.
*/
if (pipe(fds) == -1) {
warn("pipe failed");
goto out;
}
switch (pid = fork()) {
case -1:
logit("fork failed (%s)", strerror(errno));
goto out;
case 0: /* Child */
(void)close(fds[1]);
(void)read(fds[0], &status, 1);
(void)close(fds[0]);
(void)sigaction(SIGINT, &sa_int, NULL);
(void)sigaction(SIGQUIT, &sa_quit, NULL);
(void)sigaction(SIGPIPE, &sa_pipe, NULL);
break;
default:
sa.sa_handler = SIG_IGN;
(void)sigaction(SIGTTOU, &sa, NULL);
(void)close(fds[0]);
(void)setpgid(pid, pid);
(void)tcsetpgrp(STDERR_FILENO, pid);
(void)close(fds[1]);
(void)sigaction(SIGPIPE, &sa_pipe, NULL);
/*
* Parent: wait for the child to terminate
* and call pam_close_session.
*/
while ((xpid = waitpid(pid, &status, WUNTRACED))
== pid) {
if (WIFSTOPPED(status)) {
(void)kill(getpid(), SIGSTOP);
(void)tcsetpgrp(STDERR_FILENO,
getpgid(pid));
(void)kill(pid, SIGCONT);
status = 1;
continue;
}
break;
}
(void)tcsetpgrp(STDERR_FILENO, getpgid(0));
if (xpid == -1) {
logit("Error waiting for pid %d (%s)", pid,
strerror(errno));
} else if (xpid != pid) {
/* Can't happen. */
logit("Wrong PID: %d != %d", pid, xpid);
}
out:
pam_err = pam_setcred(pamh, PAM_DELETE_CRED);
if (pam_err != PAM_SUCCESS)
logit("pam_setcred: %s",
safe_pam_strerror(pamh, pam_err));
pam_err = pam_close_session(pamh, 0);
if (pam_err != PAM_SUCCESS)
logit("pam_close_session: %s",
safe_pam_strerror(pamh, pam_err));
(void)pam_end(pamh, pam_err);
exit(WEXITSTATUS(status));
break;
}
}
/*
* The child: starting here, we don't have to care about
* handling PAM issues if we exit, the parent will do the
* job when we exit.
*/
#undef PAM_END
#undef ERR_PAM_END
#undef ERRX_PAM_END
if (!asme) {
if (asthem) {
char **pamenv;
p = getenv("TERM");
/*
* Create an empty environment
*/
environ = emalloc(sizeof(char *));
environ[0] = NULL;
/*
* Add PAM environement, before the LOGIN_CAP stuff:
* if the login class is unspecified, we'll get the
* same data from PAM, if -c was used, the specified
* class must override PAM.
*/
if ((pamenv = pam_getenvlist(pamh)) != NULL) {
char **envitem;
/*
* XXX Here FreeBSD filters out
* SHELL, LOGNAME, MAIL, CDPATH, IFS, PATH
* how could we get untrusted data here?
*/
for (envitem = pamenv; *envitem; envitem++) {
if (putenv(*envitem) == -1)
free(*envitem);
}
free(pamenv);
}
if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETPATH |
LOGIN_SETENV | LOGIN_SETUMASK) == -1)
err(EXIT_FAILURE, "setting user context");
if (p)
(void)setenv("TERM", p, 1);
}
if (asthem || pwd->pw_uid) {
(void)setenv("LOGNAME", pwd->pw_name, 1);
(void)setenv("USER", pwd->pw_name, 1);
}
(void)setenv("HOME", pwd->pw_dir, 1);
(void)setenv("SHELL", shell, 1);
}
(void)setenv("SU_FROM", username, 1);
if (iscsh == YES) {
if (fastlogin)
*np-- = __UNCONST("-f");
if (asme)
*np-- = __UNCONST("-m");
} else {
if (fastlogin)
(void)unsetenv("ENV");
}
if (asthem) {
avshellbuf[0] = '-';
(void)estrlcpy(avshellbuf + 1, avshell, sizeof(avshellbuf) - 1);
avshell = avshellbuf;
} else if (iscsh == YES) {
/* csh strips the first character... */
avshellbuf[0] = '_';
(void)estrlcpy(avshellbuf + 1, avshell, sizeof(avshellbuf) - 1);
avshell = avshellbuf;
}
*np = __UNCONST(avshell);
if (ruid != 0)
syslog(LOG_NOTICE, "%s to %s%s",
username, pwd->pw_name, ontty());
/* Raise our priority back to what we had before */
(void)setpriority(PRIO_PROCESS, 0, prio);
/*
* Set user context, except for umask, and the stuff
* we have done before.
*/
setwhat = LOGIN_SETALL & ~(LOGIN_SETENV | LOGIN_SETUMASK |
LOGIN_SETLOGIN | LOGIN_SETPATH | LOGIN_SETGROUP);
/*
* Don't touch resource/priority settings if -m has been used
* or -l and -c hasn't, and we're not su'ing to root.
*/
if ((asme || (!asthem && class == NULL)) && pwd->pw_uid)
setwhat &= ~(LOGIN_SETPRIORITY | LOGIN_SETRESOURCES);
if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) == -1)
err(EXIT_FAILURE, "setusercontext");
if (!asme) {
if (asthem) {
if (gohome && chdir(pwd->pw_dir) == -1)
errx(EXIT_FAILURE, "no directory");
}
}
(void)execv(shell, np);
err(EXIT_FAILURE, "%s", shell);
done:
logit("%s: %s", func, safe_pam_strerror(pamh, pam_err));
(void)pam_end(pamh, pam_err);
return EXIT_FAILURE;
}
static void
logit(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
vwarnx(fmt, ap);
va_end(ap);
va_start(ap, fmt);
vsyslog(LOG_ERR, fmt, ap);
va_end(ap);
}
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