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) 2001-2003 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 <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 };
  74
  75 /* Initialise the krb5 library, for the stuff that GSSAPI won't do */
  76
  77 static int
  78 ssh_gssapi_krb5_init(void)
  79 {
  80         krb5_error_code problem;
  81
  82         if (krb_context != NULL)
  83                 return 1;
  84
  85         problem = krb5_init_context(&krb_context);
  86         if (problem) {
  87                 logit("Cannot initialize krb5 context");
  88                 return 0;
  89         }
  90
  91         return 1;
  92 }
  93
  94 /* Check if this user is OK to login. This only works with krb5 - other
  95  * GSSAPI mechanisms will need their own.
  96  * Returns true if the user is OK to log in, otherwise returns 0
  97  */
  98
  99 static int
 100 ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name)
 101 {
 102         krb5_principal princ;
 103         int retval;
 104
 105         if (ssh_gssapi_krb5_init() == 0)
 106                 return 0;
 107
 108         if ((retval = krb5_parse_name(krb_context, client->exportedname.value,
 109             &princ))) {
 110                 logit("krb5_parse_name(): %.100s",
 111                     krb5_get_err_text(krb_context, retval));
 112                 return 0;
 113         }
 114         if (krb5_kuserok(krb_context, princ, name)) {
 115                 retval = 1;
 116                 logit("Authorized to %s, krb5 principal %s (krb5_kuserok)",
 117                     name, (char *)client->displayname.value);
 118         } else
 119                 retval = 0;
 120
 121         krb5_free_principal(krb_context, princ);
 122         return retval;
 123 }
 124
 125
 126 /* Retrieve the local username associated with a set of Kerberos
 127  * credentials. Hopefully we can use this for the 'empty' username
 128  * logins discussed in the draft  */
 129 static int
 130 ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user) {
 131         krb5_principal princ;
 132         int retval;
 133
 134         if (ssh_gssapi_krb5_init() == 0)
 135                 return 0;
 136
 137         if ((retval=krb5_parse_name(krb_context, client->displayname.value,
 138                                     &princ))) {
 139                 logit("krb5_parse_name(): %.100s",
 140                         krb5_get_err_text(krb_context,retval));
 141                 return 0;
 142         }
 143
 144         /* We've got to return a malloc'd string */
 145         *user = (char *)xmalloc(256);
 146         if (krb5_aname_to_localname(krb_context, princ, 256, *user)) {
 147                 xfree(*user);
 148                 *user = NULL;
 149                 return(0);
 150         }
 151
 152         return(1);
 153 }
 154
 155 /* This writes out any forwarded credentials from the structure populated
 156  * during userauth. Called after we have setuid to the user */
 157
 158 static void
 159 ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
 160 {
 161         krb5_ccache ccache;
 162         krb5_error_code problem;
 163         krb5_principal princ;
 164         OM_uint32 maj_status, min_status;
 165         gss_cred_id_t krb5_cred_handle;
 166         int len;
 167         const char *new_ccname;
 168
 169         if (client->creds == NULL) {
 170                 debug("No credentials stored");
 171                 return;
 172         }
 173
 174         if (ssh_gssapi_krb5_init() == 0)
 175                 return;
 176
 177 #ifdef HEIMDAL
 178         if ((problem = krb5_cc_gen_new(krb_context, &krb5_fcc_ops, &ccache))) {
 179                 logit("krb5_cc_gen_new(): %.100s",
 180                     krb5_get_err_text(krb_context, problem));
 181                 return;
 182         }
 183 #else
 184         if ((problem = ssh_krb5_cc_gen(krb_context, &ccache))) {
 185                 logit("ssh_krb5_cc_gen(): %.100s",
 186                     krb5_get_err_text(krb_context, problem));
 187                 return;
 188         }
 189 #endif  /* #ifdef HEIMDAL */
 190
 191         if ((problem = krb5_parse_name(krb_context,
 192             client->exportedname.value, &princ))) {
 193                 logit("krb5_parse_name(): %.100s",
 194                     krb5_get_err_text(krb_context, problem));
 195                 krb5_cc_destroy(krb_context, ccache);
 196                 return;
 197         }
 198
 199         if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
 200                 logit("krb5_cc_initialize(): %.100s",
 201                     krb5_get_err_text(krb_context, problem));
 202                 krb5_free_principal(krb_context, princ);
 203                 krb5_cc_destroy(krb_context, ccache);
 204                 return;
 205         }
 206
 207         krb5_free_principal(krb_context, princ);
 208
 209 #ifdef MECHGLUE
 210         krb5_cred_handle =
 211             __gss_get_mechanism_cred(client->creds,
 212                                      &(gssapi_kerberos_mech.oid));
 213 #else
 214         krb5_cred_handle = client->creds;
 215 #endif
 216
 217         if ((maj_status = gss_krb5_copy_ccache(&min_status,
 218             krb5_cred_handle, ccache))) {
 219                 logit("gss_krb5_copy_ccache() failed");
 220                 krb5_cc_destroy(krb_context, ccache);
 221                 return;
 222         }
 223
 224         new_ccname = krb5_cc_get_name(krb_context, ccache);
 225
 226         client->store.envvar = "KRB5CCNAME";
 227 #ifdef USE_CCAPI
 228         xasprintf(&client->store.envval, "API:%s", new_ccname);
 229         client->store.filename = NULL;
 230 #else
 231         xasprintf(&client->store.envval, "FILE:%s", new_ccname);
 232         client->store.filename = xstrdup(new_ccname);
 233 #endif
 234
 235 #ifdef USE_PAM
 236         if (options.use_pam)
 237                 do_pam_putenv(client->store.envvar, client->store.envval);
 238 #endif
 239
 240         krb5_cc_close(krb_context, ccache);
 241
 242         return;
 243 }
 244
 245 #endif /* KRB5 */
 246
 247 #endif /* GSSAPI */