su.c revision 103423 
1/*
2 * Copyright (c) 1999 - 2002 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 1.25 2002/09/10 20:03:47 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#include <kafs.h>
60#endif
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#ifdef KRB4
257    /* convert creds? */
258    if(k_hasafs()) {
259	if (k_setpag() == 0)
260	    krb5_afslog(context, ccache2, NULL, NULL);
261    }
262#endif
263
264    krb5_cc_close(context, ccache2);
265    krb5_cc_destroy(context, ccache);
266    return 0;
267}
268#endif
269
270#ifdef KRB4
271
272static int
273krb_verify(const struct passwd *login_info,
274	   const struct passwd *su_info,
275	   const char *kerberos_instance)
276{
277    int ret;
278    char *login_name = NULL;
279    char *name, *instance, realm[REALM_SZ];
280
281#if defined(HAVE_GETLOGIN) && !defined(POSIX_GETLOGIN)
282    login_name = getlogin();
283#endif
284
285    ret = krb_get_lrealm(realm, 1);
286
287    if (login_name == NULL || strcmp (login_name, "root") == 0)
288	login_name = login_info->pw_name;
289    if (strcmp (su_info->pw_name, "root") == 0) {
290	name = login_name;
291	instance = (char*)kerberos_instance;
292    } else {
293	name = su_info->pw_name;
294	instance = "";
295    }
296
297    if(su_info->pw_uid != 0 ||
298       krb_kuserok(name, instance, realm, su_info->pw_name) == 0) {
299	char password[128];
300	char *prompt;
301	asprintf (&prompt,
302		  "%s's Password: ",
303		  krb_unparse_name_long (name, instance, realm));
304	if (des_read_pw_string (password, sizeof (password), prompt, 0)) {
305	    memset (password, 0, sizeof (password));
306	    free(prompt);
307	    return (1);
308	}
309	free(prompt);
310	if (strlen(password) == 0)
311	    return (1);		/* Empty passwords are not allowed */
312	set_tkfile();
313	setuid(geteuid()); /* need to run as root here */
314	ret = krb_verify_user(name, instance, realm, password,
315			      KRB_VERIFY_SECURE, NULL);
316	memset(password, 0, sizeof(password));
317
318	if(ret) {
319	    warnx("%s", krb_get_err_text(ret));
320	    return 1;
321	}
322	chown (tkt_string(), su_info->pw_uid, su_info->pw_gid);
323	return 0;
324    }
325    return 1;
326}
327
328
329static int
330krb_start_session(void)
331{
332    esetenv("KRBTKFILE", tkfile, 1);
333
334    /* convert creds? */
335    if(k_hasafs() && k_setpag() == 0)
336	krb_afslog(NULL, NULL);
337
338    return 0;
339}
340#endif
341
342static int
343verify_unix(struct passwd *su)
344{
345    char prompt[128];
346    char pw_buf[1024];
347    char *pw;
348    int r;
349    if(su->pw_passwd != NULL && *su->pw_passwd != '\0') {
350	snprintf(prompt, sizeof(prompt), "%s's password: ", su->pw_name);
351	r = des_read_pw_string(pw_buf, sizeof(pw_buf), prompt, 0);
352	if(r != 0)
353	    exit(0);
354	pw = crypt(pw_buf, su->pw_passwd);
355	memset(pw_buf, 0, sizeof(pw_buf));
356	if(strcmp(pw, su->pw_passwd) != 0)
357	    return 1;
358    }
359    return 0;
360}
361
362int
363main(int argc, char **argv)
364{
365    int i, optind = 0;
366    char *su_user;
367    struct passwd *su_info;
368    struct passwd *login_info;
369
370    struct passwd *pwd;
371
372    char *shell;
373
374    int ok = 0;
375    int kerberos_error=1;
376
377    setprogname (argv[0]);
378
379    if(getarg(args, sizeof(args) / sizeof(args[0]), argc, argv, &optind))
380	usage(1);
381
382    for (i=0; i < optind; i++)
383      if (strcmp(argv[i], "-") == 0) {
384	 full_login = 1;
385	 break;
386      }
387
388    if(help_flag)
389	usage(0);
390    if(version_flag) {
391	print_version(NULL);
392	exit(0);
393    }
394    if(optind >= argc)
395	su_user = "root";
396    else
397	su_user = argv[optind++];
398
399    pwd = k_getpwnam(su_user);
400    if(pwd == NULL)
401	errx (1, "unknown login %s", su_user);
402    if (pwd->pw_uid == 0 && strcmp ("root", su_user) != 0) {
403	syslog (LOG_ALERT, "NIS attack, user %s has uid 0", su_user);
404	errx (1, "unknown login %s", su_user);
405    }
406    su_info = dup_info(pwd);
407    if (su_info == NULL)
408	errx (1, "malloc: out of memory");
409
410	pwd = getpwuid(getuid());
411    if(pwd == NULL)
412	errx(1, "who are you?");
413    login_info = dup_info(pwd);
414    if (login_info == NULL)
415	errx (1, "malloc: out of memory");
416    if(env_flag)
417	shell = login_info->pw_shell;
418    else
419	shell = su_info->pw_shell;
420    if(shell == NULL || *shell == '\0')
421	shell = _PATH_BSHELL;
422
423
424#ifdef KRB5
425    if(kerberos_flag && ok == 0 &&
426      (kerberos_error=krb5_verify(login_info, su_info, kerberos_instance)) == 0)
427	ok = 5;
428#endif
429#ifdef KRB4
430    if(kerberos_flag && ok == 0 &&
431       (kerberos_error = krb_verify(login_info, su_info, kerberos_instance)) == 0)
432	ok = 4;
433#endif
434
435    if(ok == 0 && login_info->pw_uid && verify_unix(su_info) != 0) {
436	printf("Sorry!\n");
437	exit(1);
438    }
439
440#ifdef HAVE_GETSPNAM
441   {  struct spwd *sp;
442      long    today;
443
444    sp = getspnam(su_info->pw_name);
445    if (sp != NULL) {
446	today = time(0)/(24L * 60 * 60);
447	if (sp->sp_expire > 0) {
448	    if (today >= sp->sp_expire) {
449		if (login_info->pw_uid)
450		    errx(1,"Your account has expired.");
451		else
452		    printf("Your account has expired.");
453            }
454            else if (sp->sp_expire - today < 14)
455                printf("Your account will expire in %d days.\n",
456		       (int)(sp->sp_expire - today));
457	}
458	if (sp->sp_max > 0) {
459	    if (today >= sp->sp_lstchg + sp->sp_max) {
460		if (login_info->pw_uid)
461		    errx(1,"Your password has expired. Choose a new one.");
462		else
463		    printf("Your password has expired. Choose a new one.");
464	    }
465	    else if (today >= sp->sp_lstchg + sp->sp_max - sp->sp_warn)
466		printf("Your account will expire in %d days.\n",
467		       (int)(sp->sp_lstchg + sp->sp_max -today));
468	}
469    }
470    }
471#endif
472    {
473	char *tty = ttyname (STDERR_FILENO);
474	syslog (LOG_NOTICE | LOG_AUTH, tty ? "%s to %s" : "%s to %s on %s",
475		login_info->pw_name, su_info->pw_name, tty);
476    }
477
478
479    if(!env_flag) {
480	if(full_login) {
481	    char *t = getenv ("TERM");
482
483	    environ = malloc (10 * sizeof (char *));
484	    if (environ == NULL)
485		err (1, "malloc");
486	    environ[0] = NULL;
487	    esetenv ("PATH", _PATH_DEFPATH, 1);
488	    if (t)
489		esetenv ("TERM", t, 1);
490	    if (chdir (su_info->pw_dir) < 0)
491		errx (1, "no directory");
492	}
493	if (full_login || su_info->pw_uid)
494	    esetenv ("USER", su_info->pw_name, 1);
495	esetenv("HOME", su_info->pw_dir, 1);
496	esetenv("SHELL", shell, 1);
497    }
498
499    {
500	int i;
501	char **args;
502	char *p;
503
504	p = strrchr(shell, '/');
505	if(p)
506	    p++;
507	else
508	    p = shell;
509
510	if (strcmp(p, "csh") != 0)
511	    csh_f_flag = 0;
512
513        args = malloc(((cmd ? 2 : 0) + 1 + argc - optind + 1 + csh_f_flag) * sizeof(*args));
514	if (args == NULL)
515	    err (1, "malloc");
516	i = 0;
517	if(full_login)
518	    asprintf(&args[i++], "-%s", p);
519	else
520	    args[i++] = p;
521	if (cmd) {
522	   args[i++] = "-c";
523	   args[i++] = cmd;
524	}
525
526	if (csh_f_flag)
527	    args[i++] = "-f";
528
529	for (argv += optind; *argv; ++argv)
530	   args[i++] = *argv;
531	args[i] = NULL;
532
533	if(setgid(su_info->pw_gid) < 0)
534	    err(1, "setgid");
535	if (initgroups (su_info->pw_name, su_info->pw_gid) < 0)
536	    err (1, "initgroups");
537	if(setuid(su_info->pw_uid) < 0
538	   || (su_info->pw_uid != 0 && setuid(0) == 0))
539	    err(1, "setuid");
540
541#ifdef KRB5
542        if (ok == 5)
543           krb5_start_session();
544#endif
545#ifdef KRB4
546	if (ok == 4)
547	    krb_start_session();
548#endif
549	{
550	    char **p;
551	    for(p = args; *p; p++)
552		printf("%s ", *p);
553	    printf("\n");
554	}
555	execv(shell, args);
556    }
557
558    exit(1);
559}
560