openssh/gss-serv-krb5.c

   1 /* $OpenBSD: gss-serv-krb5.c,v 1.7 2006/08/03 03:34:42 deraadt Exp $ */
   2
   3 /*
   4  * Copyright (c) 2001-2007 Simon Wilkinson. 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  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "includes.h"
  28
  29 #ifdef GSSAPI
  30 #ifdef KRB5
  31
  32 #include <sys/types.h>
  33
  34 #include <stdarg.h>
  35 #include <string.h>
  36
  37 #include "xmalloc.h"
  38 #include "key.h"
  39 #include "hostfile.h"
  40 #include "auth.h"
  41 #include "log.h"
  42 #include "servconf.h"
  43
  44 #include "buffer.h"
  45 #include "ssh-gss.h"
  46
  47 extern ServerOptions options;
  48
  49 #ifdef HEIMDAL
  50 # include <krb5.h>
  51 #elif !defined(MECHGLUE)
  52 # ifdef HAVE_GSSAPI_KRB5_H
  53 #  include <gssapi_krb5.h>
  54 # elif HAVE_GSSAPI_GSSAPI_KRB5_H
  55 #  include <gssapi/gssapi_krb5.h>
  56 # endif
  57 #endif
  58
  59 static krb5_context krb_context = NULL;
  60 static int ssh_gssapi_krb5_init();
  61 static int ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name);
  62 static int ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user);
  63 static void ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client);
  64
  65 ssh_gssapi_mech gssapi_kerberos_mech = {
  66         "toWM5Slw5Ew8Mqkay+al2g==",
  67         "Kerberos",
  68         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
  69         NULL,
  70         &ssh_gssapi_krb5_userok,
  71         &ssh_gssapi_krb5_localname,
  72         &ssh_gssapi_krb5_storecreds,
  73         &ssh_gssapi_krb5_updatecreds
  74 };
  75
  76 /* Initialise the krb5 library, for the stuff that GSSAPI won't do */
  77
  78 static int
  79 ssh_gssapi_krb5_init(void)
  80 {
  81         krb5_error_code problem;
  82
  83         if (krb_context != NULL)
  84                 return 1;
  85
  86         problem = krb5_init_context(&krb_context);
  87         if (problem) {
  88                 logit("Cannot initialize krb5 context");
  89                 return 0;
  90         }
  91
  92         return 1;
  93 }
  94
  95 /* Check if this user is OK to login. This only works with krb5 - other
  96  * GSSAPI mechanisms will need their own.
  97  * Returns true if the user is OK to log in, otherwise returns 0
  98  */
  99
 100 static int
 101 ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name)
 102 {
 103         krb5_principal princ;
 104         int retval;
 105
 106         if (ssh_gssapi_krb5_init() == 0)
 107                 return 0;
 108
 109         if ((retval = krb5_parse_name(krb_context, client->exportedname.value,
 110             &princ))) {
 111                 logit("krb5_parse_name(): %.100s",
 112                     krb5_get_err_text(krb_context, retval));
 113                 return 0;
 114         }
 115         if (krb5_kuserok(krb_context, princ, name)) {
 116                 retval = 1;
 117                 logit("Authorized to %s, krb5 principal %s (krb5_kuserok)",
 118                     name, (char *)client->displayname.value);
 119         } else
 120                 retval = 0;
 121
 122         krb5_free_principal(krb_context, princ);
 123         return retval;
 124 }
 125
 126
 127 /* Retrieve the local username associated with a set of Kerberos
 128  * credentials. Hopefully we can use this for the 'empty' username
 129  * logins discussed in the draft  */
 130 static int
 131 ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user) {
 132         krb5_principal princ;
 133         int retval;
 134
 135         if (ssh_gssapi_krb5_init() == 0)
 136                 return 0;
 137
 138         if ((retval=krb5_parse_name(krb_context, client->displayname.value,
 139                                     &princ))) {
 140                 logit("krb5_parse_name(): %.100s",
 141                         krb5_get_err_text(krb_context,retval));
 142                 return 0;
 143         }
 144
 145         /* We've got to return a malloc'd string */
 146         *user = (char *)xmalloc(256);
 147         if (krb5_aname_to_localname(krb_context, princ, 256, *user)) {
 148                 xfree(*user);
 149                 *user = NULL;
 150                 return(0);
 151         }
 152
 153         return(1);
 154 }
 155
 156 /* This writes out any forwarded credentials from the structure populated
 157  * during userauth. Called after we have setuid to the user */
 158
 159 static void
 160 ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
 161 {
 162         krb5_ccache ccache;
 163         krb5_error_code problem;
 164         krb5_principal princ;
 165         OM_uint32 maj_status, min_status;
 166         gss_cred_id_t krb5_cred_handle;
 167         int len;
 168         const char *new_ccname;
 169
 170         if (client->creds == NULL) {
 171                 debug("No credentials stored");
 172                 return;
 173         }
 174
 175         if (ssh_gssapi_krb5_init() == 0)
 176                 return;
 177
 178 #ifdef HEIMDAL
 179         if ((problem = krb5_cc_gen_new(krb_context, &krb5_fcc_ops, &ccache))) {
 180                 logit("krb5_cc_gen_new(): %.100s",
 181                     krb5_get_err_text(krb_context, problem));
 182                 return;
 183         }
 184 #else
 185         if ((problem = ssh_krb5_cc_gen(krb_context, &ccache))) {
 186                 logit("ssh_krb5_cc_gen(): %.100s",
 187                     krb5_get_err_text(krb_context, problem));
 188                 return;
 189         }
 190 #endif  /* #ifdef HEIMDAL */
 191
 192         if ((problem = krb5_parse_name(krb_context,
 193             client->exportedname.value, &princ))) {
 194                 logit("krb5_parse_name(): %.100s",
 195                     krb5_get_err_text(krb_context, problem));
 196                 krb5_cc_destroy(krb_context, ccache);
 197                 return;
 198         }
 199
 200         if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
 201                 logit("krb5_cc_initialize(): %.100s",
 202                     krb5_get_err_text(krb_context, problem));
 203                 krb5_free_principal(krb_context, princ);
 204                 krb5_cc_destroy(krb_context, ccache);
 205                 return;
 206         }
 207
 208         krb5_free_principal(krb_context, princ);
 209
 210 #ifdef MECHGLUE
 211         krb5_cred_handle =
 212             __gss_get_mechanism_cred(client->creds,
 213                                      &(gssapi_kerberos_mech.oid));
 214 #else
 215         krb5_cred_handle = client->creds;
 216 #endif
 217
 218         if ((maj_status = gss_krb5_copy_ccache(&min_status,
 219             krb5_cred_handle, ccache))) {
 220                 logit("gss_krb5_copy_ccache() failed");
 221                 krb5_cc_destroy(krb_context, ccache);
 222                 return;
 223         }
 224
 225         new_ccname = krb5_cc_get_name(krb_context, ccache);
 226
 227         client->store.envvar = "KRB5CCNAME";
 228 #ifdef USE_CCAPI
 229         xasprintf(&client->store.envval, "API:%s", new_ccname);
 230         client->store.filename = NULL;
 231 #else
 232         xasprintf(&client->store.envval, "FILE:%s", new_ccname);
 233         client->store.filename = xstrdup(new_ccname);
 234 #endif
 235
 236 #ifdef USE_PAM
 237         if (options.use_pam)
 238                 do_pam_putenv(client->store.envvar, client->store.envval);
 239 #endif
 240
 241         krb5_cc_close(krb_context, ccache);
 242
 243         return;
 244 }
 245
 246 int
 247 ssh_gssapi_krb5_updatecreds(ssh_gssapi_ccache *store,
 248     ssh_gssapi_client *client)
 249 {
 250         krb5_ccache ccache = NULL;
 251         krb5_principal principal = NULL;
 252         char *name = NULL;
 253         krb5_error_code problem;
 254         OM_uint32 maj_status, min_status;
 255
 256         if ((problem = krb5_cc_resolve(krb_context, store->envval, &ccache))) {
 257                 logit("krb5_cc_resolve(): %.100s",
 258                     krb5_get_err_text(krb_context, problem));
 259                 return 0;
 260         }
 261
 262         /* Find out who the principal in this cache is */
 263         if ((problem = krb5_cc_get_principal(krb_context, ccache,
 264             &principal))) {
 265                 logit("krb5_cc_get_principal(): %.100s",
 266                     krb5_get_err_text(krb_context, problem));
 267                 krb5_cc_close(krb_context, ccache);
 268                 return 0;
 269         }
 270
 271         if ((problem = krb5_unparse_name(krb_context, principal, &name))) {
 272                 logit("krb5_unparse_name(): %.100s",
 273                     krb5_get_err_text(krb_context, problem));
 274                 krb5_free_principal(krb_context, principal);
 275                 krb5_cc_close(krb_context, ccache);
 276                 return 0;
 277         }
 278
 279
 280         if (strcmp(name,client->exportedname.value)!=0) {
 281                 debug("Name in local credentials cache differs. Not storing");
 282                 krb5_free_principal(krb_context, principal);
 283                 krb5_cc_close(krb_context, ccache);
 284                 krb5_free_unparsed_name(krb_context, name);
 285                 return 0;
 286         }
 287         krb5_free_unparsed_name(krb_context, name);
 288
 289         /* Name matches, so lets get on with it! */
 290
 291         if ((problem = krb5_cc_initialize(krb_context, ccache, principal))) {
 292                 logit("krb5_cc_initialize(): %.100s",
 293                     krb5_get_err_text(krb_context, problem));
 294                 krb5_free_principal(krb_context, principal);
 295                 krb5_cc_close(krb_context, ccache);
 296                 return 0;
 297         }
 298
 299         krb5_free_principal(krb_context, principal);
 300
 301         if ((maj_status = gss_krb5_copy_ccache(&min_status, client->creds,
 302             ccache))) {
 303                 logit("gss_krb5_copy_ccache() failed. Sorry!");
 304                 krb5_cc_close(krb_context, ccache);
 305                 return 0;
 306         }
 307
 308         return 1;
 309 }
 310
 311 #endif /* KRB5 */
 312
 313 #endif /* GSSAPI */