appl/su/su.c

   1 /*
   2  * Copyright (c) 1999 - 2003 Kungliga Tekniska Högskolan
   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
  35 RCSID("$Id$");
  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
  73 int kerberos_flag = 1;
  74 int csh_f_flag;
  75 int full_login;
  76 int env_flag;
  77 char *kerberos_instance = "root";
  78 int help_flag;
  79 int version_flag;
  80 char *cmd;
  81 char tkfile[256];
  82
  83 struct 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
 101 static void
 102 usage (int ret)
 103 {
 104     arg_printusage (args,
 105                     sizeof(args)/sizeof(*args),
 106                     NULL,
 107                     "[login [shell arguments]]");
 108     exit (ret);
 109 }
 110
 111 static void
 112 free_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
 121 static struct passwd*
 122 dup_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)
 144 static void
 145 set_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
 164 static krb5_context context;
 165 static krb5_ccache ccache;
 166
 167 static int
 168 krb5_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
 233 static int
 234 krb5_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
 270 static int
 271 krb_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
 327 static int
 328 krb_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
 340 static int
 341 verify_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
 360 int
 361 main(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 }