openssh/gss-serv-krb5.c

   1 /*      $OpenBSD: gss-serv-krb5.c,v 1.2 2003/11/21 11:57:03 djm Exp $   */
   2
   3 /*
   4  * Copyright (c) 2001-2003 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 "auth.h"
  33 #include "xmalloc.h"
  34 #include "log.h"
  35 #include "servconf.h"
  36
  37 #include "ssh-gss.h"
  38
  39 extern ServerOptions options;
  40
  41 #ifdef HEIMDAL
  42 # include <krb5.h>
  43 #else
  44 # ifdef HAVE_GSSAPI_KRB5
  45 #  include <gssapi_krb5.h>
  46 # elif HAVE_GSSAPI_GSSAPI_KRB5
  47 #  include <gssapi/gssapi_krb5.h>
  48 # endif
  49 #endif
  50
  51 static krb5_context krb_context = NULL;
  52
  53 /* Initialise the krb5 library, for the stuff that GSSAPI won't do */
  54
  55 static int
  56 ssh_gssapi_krb5_init()
  57 {
  58         krb5_error_code problem;
  59
  60         if (krb_context != NULL)
  61                 return 1;
  62
  63         problem = krb5_init_context(&krb_context);
  64         if (problem) {
  65                 logit("Cannot initialize krb5 context");
  66                 return 0;
  67         }
  68         krb5_init_ets(krb_context);
  69
  70         return 1;
  71 }
  72
  73 /* Check if this user is OK to login. This only works with krb5 - other
  74  * GSSAPI mechanisms will need their own.
  75  * Returns true if the user is OK to log in, otherwise returns 0
  76  */
  77
  78 static int
  79 ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name)
  80 {
  81         krb5_principal princ;
  82         int retval;
  83
  84         if (ssh_gssapi_krb5_init() == 0)
  85                 return 0;
  86
  87         if ((retval = krb5_parse_name(krb_context, client->exportedname.value,
  88             &princ))) {
  89                 logit("krb5_parse_name(): %.100s",
  90                     krb5_get_err_text(krb_context, retval));
  91                 return 0;
  92         }
  93         if (krb5_kuserok(krb_context, princ, name)) {
  94                 retval = 1;
  95                 logit("Authorized to %s, krb5 principal %s (krb5_kuserok)",
  96                     name, (char *)client->displayname.value);
  97         } else
  98                 retval = 0;
  99
 100         krb5_free_principal(krb_context, princ);
 101         return retval;
 102 }
 103
 104
 105 /* Retrieve the local username associated with a set of Kerberos
 106  * credentials. Hopefully we can use this for the 'empty' username
 107  * logins discussed in the draft  */
 108 static int
 109 ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user) {
 110         krb5_principal princ;
 111         int retval;
 112
 113         if (ssh_gssapi_krb5_init() == 0)
 114                 return 0;
 115
 116         if ((retval=krb5_parse_name(krb_context, client->displayname.value,
 117                                     &princ))) {
 118                 logit("krb5_parse_name(): %.100s",
 119                         krb5_get_err_text(krb_context,retval));
 120                 return 0;
 121         }
 122
 123         /* We've got to return a malloc'd string */
 124         *user = (char *)xmalloc(256);
 125         if (krb5_aname_to_localname(krb_context, princ, 256, *user)) {
 126                 xfree(*user);
 127                 *user = NULL;
 128                 return(0);
 129         }
 130
 131         return(1);
 132 }
 133
 134 /* This writes out any forwarded credentials from the structure populated
 135  * during userauth. Called after we have setuid to the user */
 136
 137 static void
 138 ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
 139 {
 140         krb5_ccache ccache;
 141         krb5_error_code problem;
 142         krb5_principal princ;
 143         OM_uint32 maj_status, min_status;
 144         gss_cred_id_t krb5_cred_handle;
 145         int len;
 146
 147         if (client->creds == NULL) {
 148                 debug("No credentials stored");
 149                 return;
 150         }
 151
 152         if (ssh_gssapi_krb5_init() == 0)
 153                 return;
 154
 155 #ifdef HEIMDAL
 156         if ((problem = krb5_cc_gen_new(krb_context, &krb5_fcc_ops, &ccache))) {
 157                 logit("krb5_cc_gen_new(): %.100s",
 158                     krb5_get_err_text(krb_context, problem));
 159                 return;
 160         }
 161 #else
 162         {
 163                 int tmpfd;
 164                 char ccname[40];
 165
 166                 snprintf(ccname, sizeof(ccname),
 167                     "FILE:/tmp/krb5cc_%d_XXXXXX", geteuid());
 168
 169                 if ((tmpfd = mkstemp(ccname + strlen("FILE:"))) == -1) {
 170                         logit("mkstemp(): %.100s", strerror(errno));
 171                         problem = errno;
 172                         return;
 173                 }
 174                 if (fchmod(tmpfd, S_IRUSR | S_IWUSR) == -1) {
 175                         logit("fchmod(): %.100s", strerror(errno));
 176                         close(tmpfd);
 177                         problem = errno;
 178                         return;
 179                 }
 180                 close(tmpfd);
 181                 if ((problem = krb5_cc_resolve(krb_context, ccname, &ccache))) {
 182                         logit("krb5_cc_resolve(): %.100s",
 183                             krb5_get_err_text(krb_context, problem));
 184                         return;
 185                 }
 186         }
 187 #endif  /* #ifdef HEIMDAL */
 188
 189         if ((problem = krb5_parse_name(krb_context,
 190             client->exportedname.value, &princ))) {
 191                 logit("krb5_parse_name(): %.100s",
 192                     krb5_get_err_text(krb_context, problem));
 193                 krb5_cc_destroy(krb_context, ccache);
 194                 return;
 195         }
 196
 197         if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
 198                 logit("krb5_cc_initialize(): %.100s",
 199                     krb5_get_err_text(krb_context, problem));
 200                 krb5_free_principal(krb_context, princ);
 201                 krb5_cc_destroy(krb_context, ccache);
 202                 return;
 203         }
 204
 205         krb5_free_principal(krb_context, princ);
 206
 207 #ifdef MECHGLUE
 208         krb5_cred_handle =
 209             __gss_get_mechanism_cred(client->creds,
 210                                      &(gssapi_kerberos_mech.oid));
 211 #else
 212         krb5_cred_handle = client->creds;
 213 #endif
 214
 215         if ((maj_status = gss_krb5_copy_ccache(&min_status,
 216             krb5_cred_handle, ccache))) {
 217                 logit("gss_krb5_copy_ccache() failed");
 218                 krb5_cc_destroy(krb_context, ccache);
 219                 return;
 220         }
 221
 222         client->store.filename = xstrdup(krb5_cc_get_name(krb_context, ccache));
 223         client->store.envvar = "KRB5CCNAME";
 224         len = strlen(client->store.filename) + 6;
 225         client->store.envval = xmalloc(len);
 226         snprintf(client->store.envval, len, "FILE:%s", client->store.filename);
 227
 228 #ifdef USE_PAM
 229         if (options.use_pam)
 230                 do_pam_putenv(client->store.envvar, client->store.envval);
 231 #endif
 232
 233         krb5_cc_close(krb_context, ccache);
 234
 235         return;
 236 }
 237
 238 ssh_gssapi_mech gssapi_kerberos_mech = {
 239         "toWM5Slw5Ew8Mqkay+al2g==",
 240         "Kerberos",
 241         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
 242         NULL,
 243         &ssh_gssapi_krb5_userok,
 244         &ssh_gssapi_krb5_localname,
 245         &ssh_gssapi_krb5_storecreds
 246 };
 247
 248 ssh_gssapi_mech gssapi_kerberos_mech_old = {
 249         "Se3H81ismmOC3OE+FwYCiQ==",
 250         "Kerberos",
 251         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
 252         &ssh_gssapi_krb5_init,
 253         &ssh_gssapi_krb5_userok,
 254         &ssh_gssapi_krb5_localname,
 255         &ssh_gssapi_krb5_storecreds
 256 };
 257
 258 #endif /* KRB5 */
 259
 260 #endif /* GSSAPI */