openssh/gss-serv-krb5.c

   1 /*      $OpenBSD: gss-serv-krb5.c,v 1.3 2004/07/21 10:36:23 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 #elsif !defined(MECHGLUE)
  44 # ifdef HAVE_GSSAPI_KRB5_H
  45 #  include <gssapi_krb5.h>
  46 # elif HAVE_GSSAPI_GSSAPI_KRB5_H
  47 #  include <gssapi/gssapi_krb5.h>
  48 # endif
  49 #endif
  50
  51 static krb5_context krb_context = NULL;
  52 static int ssh_gssapi_krb5_init();
  53 static int ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name);
  54 static int ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user);
  55 static void ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client);
  56
  57 ssh_gssapi_mech gssapi_kerberos_mech = {
  58         "toWM5Slw5Ew8Mqkay+al2g==",
  59         "Kerberos",
  60         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
  61         NULL,
  62         &ssh_gssapi_krb5_userok,
  63         &ssh_gssapi_krb5_localname,
  64         &ssh_gssapi_krb5_storecreds
  65 };
  66
  67 /* Initialise the krb5 library, for the stuff that GSSAPI won't do */
  68
  69 static int
  70 ssh_gssapi_krb5_init(void)
  71 {
  72         krb5_error_code problem;
  73
  74         if (krb_context != NULL)
  75                 return 1;
  76
  77         problem = krb5_init_context(&krb_context);
  78         if (problem) {
  79                 logit("Cannot initialize krb5 context");
  80                 return 0;
  81         }
  82
  83         return 1;
  84 }
  85
  86 /* Check if this user is OK to login. This only works with krb5 - other
  87  * GSSAPI mechanisms will need their own.
  88  * Returns true if the user is OK to log in, otherwise returns 0
  89  */
  90
  91 static int
  92 ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name)
  93 {
  94         krb5_principal princ;
  95         int retval;
  96
  97         if (ssh_gssapi_krb5_init() == 0)
  98                 return 0;
  99
 100         if ((retval = krb5_parse_name(krb_context, client->exportedname.value,
 101             &princ))) {
 102                 logit("krb5_parse_name(): %.100s",
 103                     krb5_get_err_text(krb_context, retval));
 104                 return 0;
 105         }
 106         if (krb5_kuserok(krb_context, princ, name)) {
 107                 retval = 1;
 108                 logit("Authorized to %s, krb5 principal %s (krb5_kuserok)",
 109                     name, (char *)client->displayname.value);
 110         } else
 111                 retval = 0;
 112
 113         krb5_free_principal(krb_context, princ);
 114         return retval;
 115 }
 116
 117
 118 /* Retrieve the local username associated with a set of Kerberos
 119  * credentials. Hopefully we can use this for the 'empty' username
 120  * logins discussed in the draft  */
 121 static int
 122 ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user) {
 123         krb5_principal princ;
 124         int retval;
 125
 126         if (ssh_gssapi_krb5_init() == 0)
 127                 return 0;
 128
 129         if ((retval=krb5_parse_name(krb_context, client->displayname.value,
 130                                     &princ))) {
 131                 logit("krb5_parse_name(): %.100s",
 132                         krb5_get_err_text(krb_context,retval));
 133                 return 0;
 134         }
 135
 136         /* We've got to return a malloc'd string */
 137         *user = (char *)xmalloc(256);
 138         if (krb5_aname_to_localname(krb_context, princ, 256, *user)) {
 139                 xfree(*user);
 140                 *user = NULL;
 141                 return(0);
 142         }
 143
 144         return(1);
 145 }
 146
 147 /* This writes out any forwarded credentials from the structure populated
 148  * during userauth. Called after we have setuid to the user */
 149
 150 static void
 151 ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
 152 {
 153         krb5_ccache ccache;
 154         krb5_error_code problem;
 155         krb5_principal princ;
 156         OM_uint32 maj_status, min_status;
 157         gss_cred_id_t krb5_cred_handle;
 158         int len;
 159
 160         if (client->creds == NULL) {
 161                 debug("No credentials stored");
 162                 return;
 163         }
 164
 165         if (ssh_gssapi_krb5_init() == 0)
 166                 return;
 167
 168 #ifdef HEIMDAL
 169         if ((problem = krb5_cc_gen_new(krb_context, &krb5_fcc_ops, &ccache))) {
 170                 logit("krb5_cc_gen_new(): %.100s",
 171                     krb5_get_err_text(krb_context, problem));
 172                 return;
 173         }
 174 #else
 175         if ((problem = ssh_krb5_cc_gen(krb_context, &ccache))) {
 176                 logit("ssh_krb5_cc_gen(): %.100s",
 177                     krb5_get_err_text(krb_context, problem));
 178                 return;
 179         }
 180 #endif  /* #ifdef HEIMDAL */
 181
 182         if ((problem = krb5_parse_name(krb_context,
 183             client->exportedname.value, &princ))) {
 184                 logit("krb5_parse_name(): %.100s",
 185                     krb5_get_err_text(krb_context, problem));
 186                 krb5_cc_destroy(krb_context, ccache);
 187                 return;
 188         }
 189
 190         if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
 191                 logit("krb5_cc_initialize(): %.100s",
 192                     krb5_get_err_text(krb_context, problem));
 193                 krb5_free_principal(krb_context, princ);
 194                 krb5_cc_destroy(krb_context, ccache);
 195                 return;
 196         }
 197
 198         krb5_free_principal(krb_context, princ);
 199
 200 #ifdef MECHGLUE
 201         krb5_cred_handle =
 202             __gss_get_mechanism_cred(client->creds,
 203                                      &(gssapi_kerberos_mech.oid));
 204 #else
 205         krb5_cred_handle = client->creds;
 206 #endif
 207
 208         if ((maj_status = gss_krb5_copy_ccache(&min_status,
 209             krb5_cred_handle, ccache))) {
 210                 logit("gss_krb5_copy_ccache() failed");
 211                 krb5_cc_destroy(krb_context, ccache);
 212                 return;
 213         }
 214
 215         client->store.filename = xstrdup(krb5_cc_get_name(krb_context, ccache));
 216         client->store.envvar = "KRB5CCNAME";
 217         len = strlen(client->store.filename) + 6;
 218         client->store.envval = xmalloc(len);
 219         snprintf(client->store.envval, len, "FILE:%s", client->store.filename);
 220
 221 #ifdef USE_PAM
 222         if (options.use_pam)
 223                 do_pam_putenv(client->store.envvar, client->store.envval);
 224 #endif
 225
 226         krb5_cc_close(krb_context, ccache);
 227
 228         return;
 229 }
 230
 231 #endif /* KRB5 */
 232
 233 #endif /* GSSAPI */