auth-krb5.c

   1 /* $OpenBSD: auth-krb5.c,v 1.19 2006/08/03 03:34:41 deraadt Exp $ */
   2 /*
   3  *    Kerberos v5 authentication and ticket-passing routines.
   4  *
   5  * $FreeBSD: src/crypto/openssh/auth-krb5.c,v 1.6 2001/02/13 16:58:04 assar Exp $
   6  */
   7 /*
   8  * Copyright (c) 2002 Daniel Kouril.  All rights reserved.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #include "includes.h"
  32
  33 #include <sys/types.h>
  34 #include <pwd.h>
  35 #include <stdarg.h>
  36
  37 #include "xmalloc.h"
  38 #include "ssh.h"
  39 #include "ssh1.h"
  40 #include "packet.h"
  41 #include "log.h"
  42 #include "buffer.h"
  43 #include "servconf.h"
  44 #include "uidswap.h"
  45 #include "key.h"
  46 #include "hostfile.h"
  47 #include "auth.h"
  48
  49 #ifdef KRB5
  50 #include <errno.h>
  51 #include <unistd.h>
  52 #include <string.h>
  53 #include <krb5.h>
  54
  55 extern ServerOptions     options;
  56
  57 static int
  58 krb5_init(void *context)
  59 {
  60         Authctxt *authctxt = (Authctxt *)context;
  61         krb5_error_code problem;
  62
  63         if (authctxt->krb5_ctx == NULL) {
  64                 problem = krb5_init_context(&authctxt->krb5_ctx);
  65                 if (problem)
  66                         return (problem);
  67         }
  68         return (0);
  69 }
  70
  71 int
  72 auth_krb5_password(Authctxt *authctxt, const char *password)
  73 {
  74 #ifndef HEIMDAL
  75         krb5_creds creds;
  76         krb5_principal server;
  77 #endif
  78         krb5_error_code problem;
  79         krb5_ccache ccache = NULL;
  80         int len;
  81         char *client, *platform_client;
  82
  83         /* get platform-specific kerberos client principal name (if it exists) */
  84         platform_client = platform_krb5_get_principal_name(authctxt->pw->pw_name);
  85         client = platform_client ? platform_client : authctxt->pw->pw_name;
  86
  87         temporarily_use_uid(authctxt->pw);
  88
  89         problem = krb5_init(authctxt);
  90         if (problem)
  91                 goto out;
  92
  93         problem = krb5_parse_name(authctxt->krb5_ctx, client,
  94                     &authctxt->krb5_user);
  95         if (problem)
  96                 goto out;
  97
  98 #ifdef HEIMDAL
  99         problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_mcc_ops, &ccache);
 100         if (problem)
 101                 goto out;
 102
 103         problem = krb5_cc_initialize(authctxt->krb5_ctx, ccache,
 104                 authctxt->krb5_user);
 105         if (problem)
 106                 goto out;
 107
 108         restore_uid();
 109
 110         problem = krb5_verify_user(authctxt->krb5_ctx, authctxt->krb5_user,
 111             ccache, password, 1, NULL);
 112
 113         temporarily_use_uid(authctxt->pw);
 114
 115         if (problem)
 116                 goto out;
 117
 118         problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_fcc_ops,
 119             &authctxt->krb5_fwd_ccache);
 120         if (problem)
 121                 goto out;
 122
 123         problem = krb5_cc_copy_cache(authctxt->krb5_ctx, ccache,
 124             authctxt->krb5_fwd_ccache);
 125         krb5_cc_destroy(authctxt->krb5_ctx, ccache);
 126         ccache = NULL;
 127         if (problem)
 128                 goto out;
 129
 130 #else
 131         problem = krb5_get_init_creds_password(authctxt->krb5_ctx, &creds,
 132             authctxt->krb5_user, (char *)password, NULL, NULL, 0, NULL, NULL);
 133         if (problem)
 134                 goto out;
 135
 136         problem = krb5_sname_to_principal(authctxt->krb5_ctx, NULL, NULL,
 137             KRB5_NT_SRV_HST, &server);
 138         if (problem)
 139                 goto out;
 140
 141         restore_uid();
 142         problem = krb5_verify_init_creds(authctxt->krb5_ctx, &creds, server,
 143             NULL, NULL, NULL);
 144         krb5_free_principal(authctxt->krb5_ctx, server);
 145         temporarily_use_uid(authctxt->pw);
 146         if (problem)
 147                 goto out;
 148
 149         if (!krb5_kuserok(authctxt->krb5_ctx, authctxt->krb5_user, client)) {
 150                 problem = -1;
 151                 goto out;
 152         }
 153
 154         problem = ssh_krb5_cc_gen(authctxt->krb5_ctx, &authctxt->krb5_fwd_ccache);
 155         if (problem)
 156                 goto out;
 157
 158         problem = krb5_cc_initialize(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache,
 159                                      authctxt->krb5_user);
 160         if (problem)
 161                 goto out;
 162
 163         problem= krb5_cc_store_cred(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache,
 164                                  &creds);
 165         if (problem)
 166                 goto out;
 167 #endif
 168
 169         authctxt->krb5_ticket_file = (char *)krb5_cc_get_name(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);
 170
 171         len = strlen(authctxt->krb5_ticket_file) + 6;
 172         authctxt->krb5_ccname = xmalloc(len);
 173 #ifdef USE_CCAPI
 174         snprintf(authctxt->krb5_ccname, len, "API:%s",
 175             authctxt->krb5_ticket_file);
 176 #else
 177         snprintf(authctxt->krb5_ccname, len, "FILE:%s",
 178             authctxt->krb5_ticket_file);
 179 #endif
 180
 181 #ifdef USE_PAM
 182         if (options.use_pam)
 183                 do_pam_putenv("KRB5CCNAME", authctxt->krb5_ccname);
 184 #endif
 185
 186  out:
 187         restore_uid();
 188
 189         if (platform_client != NULL)
 190                 xfree(platform_client);
 191
 192         if (problem) {
 193                 if (ccache)
 194                         krb5_cc_destroy(authctxt->krb5_ctx, ccache);
 195
 196                 if (authctxt->krb5_ctx != NULL && problem!=-1)
 197                         debug("Kerberos password authentication failed: %s",
 198                             krb5_get_err_text(authctxt->krb5_ctx, problem));
 199                 else
 200                         debug("Kerberos password authentication failed: %d",
 201                             problem);
 202
 203                 krb5_cleanup_proc(authctxt);
 204
 205                 if (options.kerberos_or_local_passwd)
 206                         return (-1);
 207                 else
 208                         return (0);
 209         }
 210         return (authctxt->valid ? 1 : 0);
 211 }
 212
 213 void
 214 krb5_cleanup_proc(Authctxt *authctxt)
 215 {
 216         debug("krb5_cleanup_proc called");
 217         if (authctxt->krb5_fwd_ccache) {
 218                 krb5_cc_destroy(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);
 219                 authctxt->krb5_fwd_ccache = NULL;
 220         }
 221         if (authctxt->krb5_user) {
 222                 krb5_free_principal(authctxt->krb5_ctx, authctxt->krb5_user);
 223                 authctxt->krb5_user = NULL;
 224         }
 225         if (authctxt->krb5_ctx) {
 226                 krb5_free_context(authctxt->krb5_ctx);
 227                 authctxt->krb5_ctx = NULL;
 228         }
 229 }
 230
 231 #ifndef HEIMDAL
 232 krb5_error_code
 233 ssh_krb5_cc_gen(krb5_context ctx, krb5_ccache *ccache) {
 234         int ret;
 235         char ccname[40];
 236         mode_t old_umask;
 237 #ifdef USE_CCAPI
 238         char cctemplate[] = "API:krb5cc_%d";
 239 #else
 240         char cctemplate[] = "FILE:/tmp/krb5cc_%d_XXXXXXXXXX";
 241         int tmpfd;
 242 #endif
 243
 244         ret = snprintf(ccname, sizeof(ccname),
 245             cctemplate, geteuid());
 246         if (ret < 0 || (size_t)ret >= sizeof(ccname))
 247                 return ENOMEM;
 248
 249 #ifndef USE_CCAPI
 250         old_umask = umask(0177);
 251         tmpfd = mkstemp(ccname + strlen("FILE:"));
 252         umask(old_umask);
 253         if (tmpfd == -1) {
 254                 logit("mkstemp(): %.100s", strerror(errno));
 255                 return errno;
 256         }
 257
 258         if (fchmod(tmpfd,S_IRUSR | S_IWUSR) == -1) {
 259                 logit("fchmod(): %.100s", strerror(errno));
 260                 close(tmpfd);
 261                 return errno;
 262         }
 263         close(tmpfd);
 264 #endif
 265
 266         return (krb5_cc_resolve(ctx, ccname, ccache));
 267 }
 268 #endif /* !HEIMDAL */
 269 #endif /* KRB5 */