appl/su/su.c

   1 /*
   2  * Copyright (c) 1999 - 2008 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 #ifdef HAVE_CRYPT_H
  53 #include <crypt.h>
  54 #endif
  55
  56 #include "crypto-headers.h"
  57 #ifdef KRB5
  58 #include <krb5.h>
  59 #endif
  60 #include <kafs.h>
  61 #include <err.h>
  62 #include <roken.h>
  63 #include <getarg.h>
  64
  65 #include "supaths.h"
  66
  67 #if !HAVE_DECL_ENVIRON
  68 extern char **environ;
  69 #endif
  70
  71 int kerberos_flag = 1;
  72 int csh_f_flag;
  73 int full_login;
  74 int env_flag;
  75 char *kerberos_instance = "root";
  76 int help_flag;
  77 int version_flag;
  78 char *cmd;
  79 char tkfile[256];
  80
  81 struct getargs args[] = {
  82     { "kerberos", 'K', arg_negative_flag, &kerberos_flag,
  83       "don't use kerberos" },
  84     { NULL,       'f', arg_flag,          &csh_f_flag,
  85       "don't read .cshrc" },
  86     { "full",     'l', arg_flag,          &full_login,
  87       "simulate full login" },
  88     { NULL,       'm', arg_flag,          &env_flag,
  89       "leave environment unmodified" },
  90     { "instance", 'i', arg_string,        &kerberos_instance,
  91       "root instance to use" },
  92     { "command",  'c', arg_string,        &cmd,
  93       "command to execute" },
  94     { "help",     'h', arg_flag,          &help_flag },
  95     { "version",  0,   arg_flag,          &version_flag },
  96 };
  97
  98
  99 static void
 100 usage (int ret)
 101 {
 102     arg_printusage (args,
 103                     sizeof(args)/sizeof(*args),
 104                     NULL,
 105                     "[login [shell arguments]]");
 106     exit (ret);
 107 }
 108
 109 static void
 110 free_info(struct passwd *p)
 111 {
 112     free (p->pw_name);
 113     free (p->pw_passwd);
 114     free (p->pw_dir);
 115     free (p->pw_shell);
 116     free (p);
 117 }
 118
 119 static struct passwd*
 120 dup_info(const struct passwd *pwd)
 121 {
 122     struct passwd *info;
 123
 124     info = malloc(sizeof(*info));
 125     if(info == NULL)
 126         return NULL;
 127     info->pw_name = strdup(pwd->pw_name);
 128     info->pw_passwd = strdup(pwd->pw_passwd);
 129     info->pw_uid = pwd->pw_uid;
 130     info->pw_gid = pwd->pw_gid;
 131     info->pw_dir = strdup(pwd->pw_dir);
 132     info->pw_shell = strdup(pwd->pw_shell);
 133     if(info->pw_name == NULL || info->pw_passwd == NULL ||
 134        info->pw_dir == NULL || info->pw_shell == NULL) {
 135         free_info (info);
 136         return NULL;
 137     }
 138     return info;
 139 }
 140
 141 #ifdef KRB5
 142 static krb5_context context;
 143 static krb5_ccache ccache;
 144
 145 static int
 146 krb5_verify(const struct passwd *login_info,
 147             const struct passwd *su_info,
 148             const char *kerberos_instance)
 149 {
 150     krb5_error_code ret;
 151     krb5_principal p;
 152     krb5_realm *realms, *r;
 153     char *login_name = NULL;
 154     int user_ok = 0;
 155
 156 #if defined(HAVE_GETLOGIN) && !defined(POSIX_GETLOGIN)
 157     login_name = getlogin();
 158 #endif
 159     ret = krb5_init_context (&context);
 160     if (ret) {
 161 #if 0
 162         warnx("krb5_init_context failed: %d", ret);
 163 #endif
 164         return 1;
 165     }
 166
 167     ret = krb5_get_default_realms(context, &realms);
 168     if (ret)
 169         return 1;
 170
 171     /* Check all local realms */
 172     for (r = realms; *r != NULL && !user_ok; r++) {
 173
 174         if (login_name == NULL || strcmp (login_name, "root") == 0)
 175             login_name = login_info->pw_name;
 176         if (strcmp (su_info->pw_name, "root") == 0)
 177             ret = krb5_make_principal(context, &p, *r,
 178                                       login_name,
 179                                       kerberos_instance,
 180                                       NULL);
 181         else
 182             ret = krb5_make_principal(context, &p, *r,
 183                                       su_info->pw_name,
 184                                       NULL);
 185         if (ret) {
 186             krb5_free_host_realm(context, realms);
 187             return 1;
 188         }
 189
 190         /* if we are su-ing too root, check with krb5_kuserok */
 191         if (su_info->pw_uid == 0 && !krb5_kuserok(context, p, su_info->pw_name))
 192             continue;
 193
 194         ret = krb5_cc_new_unique(context, krb5_cc_type_memory, NULL, &ccache);
 195         if(ret) {
 196             krb5_free_host_realm(context, realms);
 197             krb5_free_principal (context, p);
 198             return 1;
 199         }
 200         ret = krb5_verify_user(context, p, ccache, NULL, TRUE, NULL);
 201         krb5_free_principal (context, p);
 202         switch (ret) {
 203         case 0:
 204             user_ok = 1;
 205             break;
 206         case KRB5_LIBOS_PWDINTR :
 207             krb5_cc_destroy(context, ccache);
 208             break;
 209         case KRB5KRB_AP_ERR_BAD_INTEGRITY:
 210         case KRB5KRB_AP_ERR_MODIFIED:
 211             krb5_cc_destroy(context, ccache);
 212             krb5_warnx(context, "Password incorrect");
 213             break;
 214         default :
 215             krb5_cc_destroy(context, ccache);
 216             krb5_warn(context, ret, "krb5_verify_user");
 217             break;
 218         }
 219     }
 220     krb5_free_host_realm(context, realms);
 221     if (!user_ok)
 222         return 1;
 223     return 0;
 224 }
 225
 226 static int
 227 krb5_start_session(void)
 228 {
 229     krb5_ccache ccache2;
 230     char *cc_name;
 231     int ret;
 232
 233     ret = krb5_cc_new_unique(context, krb5_cc_type_file, NULL, &ccache2);
 234     if (ret) {
 235         krb5_cc_destroy(context, ccache);
 236         return 1;
 237     }
 238
 239     ret = krb5_cc_copy_cache(context, ccache, ccache2);
 240     if (ret) {
 241         krb5_cc_destroy(context, ccache);
 242         krb5_cc_destroy(context, ccache2);
 243         return 1;
 244     }
 245
 246     ret = asprintf(&cc_name, "%s:%s", krb5_cc_get_type(context, ccache2),
 247                    krb5_cc_get_name(context, ccache2));
 248     if (ret == -1) {
 249         krb5_cc_destroy(context, ccache);
 250         krb5_cc_destroy(context, ccache2);
 251         errx(1, "malloc - out of memory");
 252     }
 253     esetenv("KRB5CCNAME", cc_name, 1);
 254
 255     /* convert creds? */
 256     if(k_hasafs()) {
 257         if (k_setpag() == 0)
 258             krb5_afslog(context, ccache2, NULL, NULL);
 259     }
 260
 261     krb5_cc_close(context, ccache2);
 262     krb5_cc_destroy(context, ccache);
 263     return 0;
 264 }
 265 #endif
 266
 267
 268 #define GROUP_MEMBER            0
 269 #define GROUP_MISSING           1
 270 #define GROUP_EMPTY             2
 271 #define GROUP_NOT_MEMBER        3
 272
 273 static int
 274 group_member_p(const char *group, const char *user)
 275 {
 276     struct group *g;
 277     int i;
 278     g = getgrnam(group);
 279     if(g == NULL)
 280         return GROUP_MISSING;
 281     if(g->gr_mem[0] == NULL)
 282         return GROUP_EMPTY;
 283     for(i = 0; g->gr_mem[i] != NULL; i++)
 284         if(strcmp(user, g->gr_mem[i]) == 0)
 285             return GROUP_MEMBER;
 286     return GROUP_NOT_MEMBER;
 287 }
 288
 289 static int
 290 verify_unix(struct passwd *login, struct passwd *su)
 291 {
 292     char prompt[128];
 293     char pw_buf[1024];
 294     char *pw;
 295     int r;
 296     if(su->pw_passwd != NULL && *su->pw_passwd != '\0') {
 297         snprintf(prompt, sizeof(prompt), "%s's password: ", su->pw_name);
 298         r = UI_UTIL_read_pw_string(pw_buf, sizeof(pw_buf), prompt, 0);
 299         if(r != 0)
 300             exit(0);
 301         pw = crypt(pw_buf, su->pw_passwd);
 302         memset(pw_buf, 0, sizeof(pw_buf));
 303         if(strcmp(pw, su->pw_passwd) != 0) {
 304             syslog (LOG_ERR | LOG_AUTH, "%s to %s: incorrect password",
 305                     login->pw_name, su->pw_name);
 306             return 1;
 307         }
 308     }
 309     /* if su:ing to root, check membership of group wheel or root; if
 310        that group doesn't exist, or is empty, allow anyone to su
 311        root */
 312     if(su->pw_uid == 0) {
 313 #ifndef ROOT_GROUP
 314 #define ROOT_GROUP "wheel"
 315 #endif
 316         int gs = group_member_p(ROOT_GROUP, login->pw_name);
 317         if(gs == GROUP_NOT_MEMBER) {
 318             syslog (LOG_ERR | LOG_AUTH, "%s to %s: not in group %s",
 319                     login->pw_name, su->pw_name, ROOT_GROUP);
 320             return 1;
 321         }
 322         return 0;
 323     }
 324     return 0;
 325 }
 326
 327 int
 328 main(int argc, char **argv)
 329 {
 330     int i, optind = 0;
 331     char *su_user;
 332     struct passwd *su_info;
 333     struct passwd *login_info;
 334
 335     struct passwd *pwd;
 336
 337     char *shell;
 338
 339     int ok = 0;
 340
 341     setprogname (argv[0]);
 342
 343     if(getarg(args, sizeof(args) / sizeof(args[0]), argc, argv, &optind))
 344         usage(1);
 345
 346     for (i=0; i < optind; i++)
 347       if (strcmp(argv[i], "-") == 0) {
 348          full_login = 1;
 349          break;
 350       }
 351
 352     if(help_flag)
 353         usage(0);
 354     if(version_flag) {
 355         print_version(NULL);
 356         exit(0);
 357     }
 358     if(optind >= argc)
 359         su_user = "root";
 360     else
 361         su_user = argv[optind++];
 362
 363     if (!issuid() && getuid() != 0)
 364         warnx("Not setuid and you are not root, expect this to fail");
 365
 366     pwd = k_getpwnam(su_user);
 367     if(pwd == NULL)
 368         errx (1, "unknown login %s", su_user);
 369     if (pwd->pw_uid == 0 && strcmp ("root", su_user) != 0) {
 370         syslog (LOG_ALERT, "NIS attack, user %s has uid 0", su_user);
 371         errx (1, "unknown login %s", su_user);
 372     }
 373     su_info = dup_info(pwd);
 374     if (su_info == NULL)
 375         errx (1, "malloc: out of memory");
 376
 377         pwd = getpwuid(getuid());
 378     if(pwd == NULL)
 379         errx(1, "who are you?");
 380     login_info = dup_info(pwd);
 381     if (login_info == NULL)
 382         errx (1, "malloc: out of memory");
 383     if(env_flag)
 384         shell = login_info->pw_shell;
 385     else
 386         shell = su_info->pw_shell;
 387     if(shell == NULL || *shell == '\0')
 388         shell = _PATH_BSHELL;
 389
 390
 391 #ifdef KRB5
 392     if(kerberos_flag && ok == 0 &&
 393        krb5_verify(login_info, su_info, kerberos_instance) == 0)
 394         ok = 5;
 395 #endif
 396
 397     if(ok == 0 && login_info->pw_uid && verify_unix(login_info, su_info) != 0) {
 398         printf("Sorry!\n");
 399         exit(1);
 400     }
 401
 402 #ifdef HAVE_GETSPNAM
 403    {  struct spwd *sp;
 404       long    today;
 405
 406     sp = getspnam(su_info->pw_name);
 407     if (sp != NULL) {
 408         today = time(0)/(24L * 60 * 60);
 409         if (sp->sp_expire > 0) {
 410             if (today >= sp->sp_expire) {
 411                 if (login_info->pw_uid)
 412                     errx(1,"Your account has expired.");
 413                 else
 414                     printf("Your account has expired.");
 415             }
 416             else if (sp->sp_expire - today < 14)
 417                 printf("Your account will expire in %d days.\n",
 418                        (int)(sp->sp_expire - today));
 419         }
 420         if (sp->sp_max > 0) {
 421             if (today >= sp->sp_lstchg + sp->sp_max) {
 422                 if (login_info->pw_uid)
 423                     errx(1,"Your password has expired. Choose a new one.");
 424                 else
 425                     printf("Your password has expired. Choose a new one.");
 426             }
 427             else if (today >= sp->sp_lstchg + sp->sp_max - sp->sp_warn)
 428                 printf("Your account will expire in %d days.\n",
 429                        (int)(sp->sp_lstchg + sp->sp_max -today));
 430         }
 431     }
 432     }
 433 #endif
 434     {
 435         char *tty = ttyname (STDERR_FILENO);
 436         syslog (LOG_NOTICE | LOG_AUTH, tty ? "%s to %s on %s" : "%s to %s",
 437                 login_info->pw_name, su_info->pw_name, tty);
 438     }
 439
 440
 441     if(!env_flag) {
 442         if(full_login) {
 443             char *t = getenv ("TERM");
 444             char **newenv = NULL;
 445             int i, j;
 446
 447             i = read_environment(_PATH_ETC_ENVIRONMENT, &newenv);
 448
 449             environ = malloc ((10 + i) * sizeof (char *));
 450             if (environ == NULL)
 451                 err (1, "malloc");
 452             environ[0] = NULL;
 453
 454             for (j = 0; j < i; j++) {
 455                 char *p = strchr(newenv[j], '=');
 456                 if (p == NULL)
 457                     errx(1, "enviroment '%s' missing '='", newenv[j]);
 458                 *p++ = 0;
 459                 esetenv (newenv[j], p, 1);
 460             }
 461             free(newenv);
 462
 463             esetenv ("PATH", _PATH_DEFPATH, 1);
 464             if (t)
 465                 esetenv ("TERM", t, 1);
 466             if (chdir (su_info->pw_dir) < 0)
 467                 errx (1, "no directory");
 468         }
 469         if (full_login || su_info->pw_uid)
 470             esetenv ("USER", su_info->pw_name, 1);
 471         esetenv("HOME", su_info->pw_dir, 1);
 472         esetenv("SHELL", shell, 1);
 473     }
 474
 475     {
 476         int i;
 477         char **args;
 478         char *p;
 479
 480         p = strrchr(shell, '/');
 481         if(p)
 482             p++;
 483         else
 484             p = shell;
 485
 486         if (strcmp(p, "csh") != 0)
 487             csh_f_flag = 0;
 488
 489         args = malloc(((cmd ? 2 : 0) + 1 + argc - optind + 1 + csh_f_flag) * sizeof(*args));
 490         if (args == NULL)
 491             err (1, "malloc");
 492         i = 0;
 493         if(full_login) {
 494             if (asprintf(&args[i++], "-%s", p) == -1)
 495                 errx (1, "malloc");
 496         } else
 497             args[i++] = p;
 498         if (cmd) {
 499            args[i++] = "-c";
 500            args[i++] = cmd;
 501         }
 502
 503         if (csh_f_flag)
 504             args[i++] = "-f";
 505
 506         for (argv += optind; *argv; ++argv)
 507            args[i++] = *argv;
 508         args[i] = NULL;
 509
 510         if(setgid(su_info->pw_gid) < 0)
 511             err(1, "setgid");
 512         if (initgroups (su_info->pw_name, su_info->pw_gid) < 0)
 513             err (1, "initgroups");
 514         if(setuid(su_info->pw_uid) < 0
 515            || (su_info->pw_uid != 0 && setuid(0) == 0))
 516             err(1, "setuid");
 517
 518 #ifdef KRB5
 519         if (ok == 5)
 520            krb5_start_session();
 521 #endif
 522         execve(shell, args, environ);
 523     }
 524
 525     exit(1);
 526 }