su.c revision 120945 
1/*
2 * Copyright (c) 1999 - 2003 Kungliga Tekniska H�gskolan
3 * (Royal Institute of Technology, Stockholm, Sweden).
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * 3. Neither the name of KTH nor the names of its contributors may be
18 *    used to endorse or promote products derived from this software without
19 *    specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY KTH AND ITS CONTRIBUTORS ``AS IS'' AND ANY
22 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
24 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL KTH OR ITS CONTRIBUTORS BE
25 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
26 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
27 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
28 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
29 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
30 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
31 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
32
33#include <config.h>
34
35RCSID("$Id: su.c,v 1.26.2.1 2003/05/06 12:06:44 joda Exp $");
36
37#include <stdio.h>
38#include <stdlib.h>
39#include <string.h>
40
41#include <syslog.h>
42
43#ifdef HAVE_PATHS_H
44#include <paths.h>
45#endif
46
47#ifdef HAVE_SHADOW_H
48#include <shadow.h>
49#endif
50
51#include <pwd.h>
52
53#include "crypto-headers.h"
54#ifdef KRB5
55#include <krb5.h>
56#endif
57#ifdef KRB4
58#include <krb.h>
59#endif
60#include <kafs.h>
61#include <err.h>
62#include <roken.h>
63#include <getarg.h>
64
65#ifndef _PATH_DEFPATH
66#define _PATH_DEFPATH "/usr/bin:/bin"
67#endif
68
69#ifndef _PATH_BSHELL
70#define _PATH_BSHELL "/bin/sh"
71#endif
72
73int kerberos_flag = 1;
74int csh_f_flag;
75int full_login;
76int env_flag;
77char *kerberos_instance = "root";
78int help_flag;
79int version_flag;
80char *cmd;
81char tkfile[256];
82
83struct getargs args[] = {
84    { "kerberos", 'K', arg_negative_flag, &kerberos_flag,
85      "don't use kerberos" },
86    { NULL,	  'f', arg_flag,	  &csh_f_flag,
87      "don't read .cshrc" },
88    { "full",	  'l', arg_flag,          &full_login,
89      "simulate full login" },
90    { NULL,	  'm', arg_flag,          &env_flag,
91      "leave environment unmodified" },
92    { "instance", 'i', arg_string,        &kerberos_instance,
93      "root instance to use" },
94    { "command",  'c', arg_string,        &cmd,
95      "command to execute" },
96    { "help", 	  'h', arg_flag,          &help_flag },
97    { "version",  0,   arg_flag,          &version_flag },
98};
99
100
101static void
102usage (int ret)
103{
104    arg_printusage (args,
105		    sizeof(args)/sizeof(*args),
106		    NULL,
107		    "[login [shell arguments]]");
108    exit (ret);
109}
110
111static void
112free_info(struct passwd *p)
113{
114    free (p->pw_name);
115    free (p->pw_passwd);
116    free (p->pw_dir);
117    free (p->pw_shell);
118    free (p);
119}
120
121static struct passwd*
122dup_info(const struct passwd *pwd)
123{
124    struct passwd *info;
125
126    info = malloc(sizeof(*info));
127    if(info == NULL)
128	return NULL;
129    info->pw_name = strdup(pwd->pw_name);
130    info->pw_passwd = strdup(pwd->pw_passwd);
131    info->pw_uid = pwd->pw_uid;
132    info->pw_gid = pwd->pw_gid;
133    info->pw_dir = strdup(pwd->pw_dir);
134    info->pw_shell = strdup(pwd->pw_shell);
135    if(info->pw_name == NULL || info->pw_passwd == NULL ||
136       info->pw_dir == NULL || info->pw_shell == NULL) {
137	free_info (info);
138	return NULL;
139    }
140    return info;
141}
142
143#if defined(KRB4) || defined(KRB5)
144static void
145set_tkfile()
146{
147#ifndef TKT_ROOT
148#define TKT_ROOT "/tmp/tkt"
149#endif
150    int fd;
151    if(*tkfile != '\0')
152	return;
153    snprintf(tkfile, sizeof(tkfile), "%s_XXXXXX", TKT_ROOT);
154    fd = mkstemp(tkfile);
155    if(fd >= 0)
156	close(fd);
157#ifdef KRB4
158    krb_set_tkt_string(tkfile);
159#endif
160}
161#endif
162
163#ifdef KRB5
164static krb5_context context;
165static krb5_ccache ccache;
166
167static int
168krb5_verify(const struct passwd *login_info,
169	    const struct passwd *su_info,
170	    const char *kerberos_instance)
171{
172    krb5_error_code ret;
173    krb5_principal p;
174    char *login_name = NULL;
175
176#if defined(HAVE_GETLOGIN) && !defined(POSIX_GETLOGIN)
177    login_name = getlogin();
178#endif
179    ret = krb5_init_context (&context);
180    if (ret) {
181#if 0
182	warnx("krb5_init_context failed: %d", ret);
183#endif
184	return 1;
185    }
186
187    if (login_name == NULL || strcmp (login_name, "root") == 0)
188	login_name = login_info->pw_name;
189    if (strcmp (su_info->pw_name, "root") == 0)
190	ret = krb5_make_principal(context, &p, NULL,
191				  login_name,
192				  kerberos_instance,
193				  NULL);
194    else
195	ret = krb5_make_principal(context, &p, NULL,
196				  su_info->pw_name,
197				  NULL);
198    if(ret)
199	return 1;
200
201    if(su_info->pw_uid != 0 || krb5_kuserok(context, p, su_info->pw_name)) {
202	ret = krb5_cc_gen_new(context, &krb5_mcc_ops, &ccache);
203	if(ret) {
204#if 1
205	    krb5_warn(context, ret, "krb5_cc_gen_new");
206#endif
207	    krb5_free_principal (context, p);
208	    return 1;
209	}
210	ret = krb5_verify_user_lrealm(context, p, ccache, NULL, TRUE, NULL);
211	krb5_free_principal (context, p);
212	if(ret) {
213	    krb5_cc_destroy(context, ccache);
214	    switch (ret) {
215	    case KRB5_LIBOS_PWDINTR :
216		break;
217	    case KRB5KRB_AP_ERR_BAD_INTEGRITY:
218	    case KRB5KRB_AP_ERR_MODIFIED:
219		krb5_warnx(context, "Password incorrect");
220		break;
221	    default :
222		krb5_warn(context, ret, "krb5_verify_user");
223		break;
224	    }
225	    return 1;
226	}
227	return 0;
228    }
229    krb5_free_principal (context, p);
230    return 1;
231}
232
233static int
234krb5_start_session(void)
235{
236    krb5_ccache ccache2;
237    char *cc_name;
238    int ret;
239
240    ret = krb5_cc_gen_new(context, &krb5_fcc_ops, &ccache2);
241    if (ret) {
242	krb5_cc_destroy(context, ccache);
243	return 1;
244    }
245
246    ret = krb5_cc_copy_cache(context, ccache, ccache2);
247
248    asprintf(&cc_name, "%s:%s", krb5_cc_get_type(context, ccache2),
249	     krb5_cc_get_name(context, ccache2));
250    esetenv("KRB5CCNAME", cc_name, 1);
251
252    /* we want to export this even if we don't directly support KRB4 */
253    set_tkfile();
254    esetenv("KRBTKFILE", tkfile, 1);
255
256    /* convert creds? */
257    if(k_hasafs()) {
258	if (k_setpag() == 0)
259	    krb5_afslog(context, ccache2, NULL, NULL);
260    }
261
262    krb5_cc_close(context, ccache2);
263    krb5_cc_destroy(context, ccache);
264    return 0;
265}
266#endif
267
268#ifdef KRB4
269
270static int
271krb_verify(const struct passwd *login_info,
272	   const struct passwd *su_info,
273	   const char *kerberos_instance)
274{
275    int ret;
276    char *login_name = NULL;
277    char *name, *instance, realm[REALM_SZ];
278
279#if defined(HAVE_GETLOGIN) && !defined(POSIX_GETLOGIN)
280    login_name = getlogin();
281#endif
282
283    ret = krb_get_lrealm(realm, 1);
284
285    if (login_name == NULL || strcmp (login_name, "root") == 0)
286	login_name = login_info->pw_name;
287    if (strcmp (su_info->pw_name, "root") == 0) {
288	name = login_name;
289	instance = (char*)kerberos_instance;
290    } else {
291	name = su_info->pw_name;
292	instance = "";
293    }
294
295    if(su_info->pw_uid != 0 ||
296       krb_kuserok(name, instance, realm, su_info->pw_name) == 0) {
297	char password[128];
298	char *prompt;
299	asprintf (&prompt,
300		  "%s's Password: ",
301		  krb_unparse_name_long (name, instance, realm));
302	if (des_read_pw_string (password, sizeof (password), prompt, 0)) {
303	    memset (password, 0, sizeof (password));
304	    free(prompt);
305	    return (1);
306	}
307	free(prompt);
308	if (strlen(password) == 0)
309	    return (1);		/* Empty passwords are not allowed */
310	set_tkfile();
311	setuid(geteuid()); /* need to run as root here */
312	ret = krb_verify_user(name, instance, realm, password,
313			      KRB_VERIFY_SECURE, NULL);
314	memset(password, 0, sizeof(password));
315
316	if(ret) {
317	    warnx("%s", krb_get_err_text(ret));
318	    return 1;
319	}
320	chown (tkt_string(), su_info->pw_uid, su_info->pw_gid);
321	return 0;
322    }
323    return 1;
324}
325
326
327static int
328krb_start_session(void)
329{
330    esetenv("KRBTKFILE", tkfile, 1);
331
332    /* convert creds? */
333    if(k_hasafs() && k_setpag() == 0)
334	krb_afslog(NULL, NULL);
335
336    return 0;
337}
338#endif
339
340static int
341verify_unix(struct passwd *su)
342{
343    char prompt[128];
344    char pw_buf[1024];
345    char *pw;
346    int r;
347    if(su->pw_passwd != NULL && *su->pw_passwd != '\0') {
348	snprintf(prompt, sizeof(prompt), "%s's password: ", su->pw_name);
349	r = des_read_pw_string(pw_buf, sizeof(pw_buf), prompt, 0);
350	if(r != 0)
351	    exit(0);
352	pw = crypt(pw_buf, su->pw_passwd);
353	memset(pw_buf, 0, sizeof(pw_buf));
354	if(strcmp(pw, su->pw_passwd) != 0)
355	    return 1;
356    }
357    return 0;
358}
359
360int
361main(int argc, char **argv)
362{
363    int i, optind = 0;
364    char *su_user;
365    struct passwd *su_info;
366    struct passwd *login_info;
367
368    struct passwd *pwd;
369
370    char *shell;
371
372    int ok = 0;
373    int kerberos_error=1;
374
375    setprogname (argv[0]);
376
377    if(getarg(args, sizeof(args) / sizeof(args[0]), argc, argv, &optind))
378	usage(1);
379
380    for (i=0; i < optind; i++)
381      if (strcmp(argv[i], "-") == 0) {
382	 full_login = 1;
383	 break;
384      }
385
386    if(help_flag)
387	usage(0);
388    if(version_flag) {
389	print_version(NULL);
390	exit(0);
391    }
392    if(optind >= argc)
393	su_user = "root";
394    else
395	su_user = argv[optind++];
396
397    pwd = k_getpwnam(su_user);
398    if(pwd == NULL)
399	errx (1, "unknown login %s", su_user);
400    if (pwd->pw_uid == 0 && strcmp ("root", su_user) != 0) {
401	syslog (LOG_ALERT, "NIS attack, user %s has uid 0", su_user);
402	errx (1, "unknown login %s", su_user);
403    }
404    su_info = dup_info(pwd);
405    if (su_info == NULL)
406	errx (1, "malloc: out of memory");
407
408	pwd = getpwuid(getuid());
409    if(pwd == NULL)
410	errx(1, "who are you?");
411    login_info = dup_info(pwd);
412    if (login_info == NULL)
413	errx (1, "malloc: out of memory");
414    if(env_flag)
415	shell = login_info->pw_shell;
416    else
417	shell = su_info->pw_shell;
418    if(shell == NULL || *shell == '\0')
419	shell = _PATH_BSHELL;
420
421
422#ifdef KRB5
423    if(kerberos_flag && ok == 0 &&
424      (kerberos_error=krb5_verify(login_info, su_info, kerberos_instance)) == 0)
425	ok = 5;
426#endif
427#ifdef KRB4
428    if(kerberos_flag && ok == 0 &&
429       (kerberos_error = krb_verify(login_info, su_info, kerberos_instance)) == 0)
430	ok = 4;
431#endif
432
433    if(ok == 0 && login_info->pw_uid && verify_unix(su_info) != 0) {
434	printf("Sorry!\n");
435	exit(1);
436    }
437
438#ifdef HAVE_GETSPNAM
439   {  struct spwd *sp;
440      long    today;
441
442    sp = getspnam(su_info->pw_name);
443    if (sp != NULL) {
444	today = time(0)/(24L * 60 * 60);
445	if (sp->sp_expire > 0) {
446	    if (today >= sp->sp_expire) {
447		if (login_info->pw_uid)
448		    errx(1,"Your account has expired.");
449		else
450		    printf("Your account has expired.");
451            }
452            else if (sp->sp_expire - today < 14)
453                printf("Your account will expire in %d days.\n",
454		       (int)(sp->sp_expire - today));
455	}
456	if (sp->sp_max > 0) {
457	    if (today >= sp->sp_lstchg + sp->sp_max) {
458		if (login_info->pw_uid)
459		    errx(1,"Your password has expired. Choose a new one.");
460		else
461		    printf("Your password has expired. Choose a new one.");
462	    }
463	    else if (today >= sp->sp_lstchg + sp->sp_max - sp->sp_warn)
464		printf("Your account will expire in %d days.\n",
465		       (int)(sp->sp_lstchg + sp->sp_max -today));
466	}
467    }
468    }
469#endif
470    {
471	char *tty = ttyname (STDERR_FILENO);
472	syslog (LOG_NOTICE | LOG_AUTH, tty ? "%s to %s" : "%s to %s on %s",
473		login_info->pw_name, su_info->pw_name, tty);
474    }
475
476
477    if(!env_flag) {
478	if(full_login) {
479	    char *t = getenv ("TERM");
480
481	    environ = malloc (10 * sizeof (char *));
482	    if (environ == NULL)
483		err (1, "malloc");
484	    environ[0] = NULL;
485	    esetenv ("PATH", _PATH_DEFPATH, 1);
486	    if (t)
487		esetenv ("TERM", t, 1);
488	    if (chdir (su_info->pw_dir) < 0)
489		errx (1, "no directory");
490	}
491	if (full_login || su_info->pw_uid)
492	    esetenv ("USER", su_info->pw_name, 1);
493	esetenv("HOME", su_info->pw_dir, 1);
494	esetenv("SHELL", shell, 1);
495    }
496
497    {
498	int i;
499	char **args;
500	char *p;
501
502	p = strrchr(shell, '/');
503	if(p)
504	    p++;
505	else
506	    p = shell;
507
508	if (strcmp(p, "csh") != 0)
509	    csh_f_flag = 0;
510
511        args = malloc(((cmd ? 2 : 0) + 1 + argc - optind + 1 + csh_f_flag) * sizeof(*args));
512	if (args == NULL)
513	    err (1, "malloc");
514	i = 0;
515	if(full_login)
516	    asprintf(&args[i++], "-%s", p);
517	else
518	    args[i++] = p;
519	if (cmd) {
520	   args[i++] = "-c";
521	   args[i++] = cmd;
522	}
523
524	if (csh_f_flag)
525	    args[i++] = "-f";
526
527	for (argv += optind; *argv; ++argv)
528	   args[i++] = *argv;
529	args[i] = NULL;
530
531	if(setgid(su_info->pw_gid) < 0)
532	    err(1, "setgid");
533	if (initgroups (su_info->pw_name, su_info->pw_gid) < 0)
534	    err (1, "initgroups");
535	if(setuid(su_info->pw_uid) < 0
536	   || (su_info->pw_uid != 0 && setuid(0) == 0))
537	    err(1, "setuid");
538
539#ifdef KRB5
540        if (ok == 5)
541           krb5_start_session();
542#endif
543#ifdef KRB4
544	if (ok == 4)
545	    krb_start_session();
546#endif
547	execv(shell, args);
548    }
549
550    exit(1);
551}
552