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 #include <gssapi_krb5.h>
  45 #endif
  46
  47 static krb5_context krb_context = NULL;
  48
  49 /* Initialise the krb5 library, for the stuff that GSSAPI won't do */
  50
  51 static int
  52 ssh_gssapi_krb5_init()
  53 {
  54         krb5_error_code problem;
  55
  56         if (krb_context != NULL)
  57                 return 1;
  58
  59         problem = krb5_init_context(&krb_context);
  60         if (problem) {
  61                 logit("Cannot initialize krb5 context");
  62                 return 0;
  63         }
  64         krb5_init_ets(krb_context);
  65
  66         return 1;
  67 }
  68
  69 /* Check if this user is OK to login. This only works with krb5 - other
  70  * GSSAPI mechanisms will need their own.
  71  * Returns true if the user is OK to log in, otherwise returns 0
  72  */
  73
  74 static int
  75 ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name)
  76 {
  77         krb5_principal princ;
  78         int retval;
  79
  80         if (ssh_gssapi_krb5_init() == 0)
  81                 return 0;
  82
  83         if ((retval = krb5_parse_name(krb_context, client->exportedname.value,
  84             &princ))) {
  85                 logit("krb5_parse_name(): %.100s",
  86                     krb5_get_err_text(krb_context, retval));
  87                 return 0;
  88         }
  89         if (krb5_kuserok(krb_context, princ, name)) {
  90                 retval = 1;
  91                 logit("Authorized to %s, krb5 principal %s (krb5_kuserok)",
  92                     name, (char *)client->displayname.value);
  93         } else
  94                 retval = 0;
  95
  96         krb5_free_principal(krb_context, princ);
  97         return retval;
  98 }
  99
 100
 101 /* This writes out any forwarded credentials from the structure populated
 102  * during userauth. Called after we have setuid to the user */
 103
 104 static void
 105 ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
 106 {
 107         krb5_ccache ccache;
 108         krb5_error_code problem;
 109         krb5_principal princ;
 110         OM_uint32 maj_status, min_status;
 111
 112         if (client->creds == NULL) {
 113                 debug("No credentials stored");
 114                 return;
 115         }
 116
 117         if (ssh_gssapi_krb5_init() == 0)
 118                 return;
 119
 120 #ifdef HEIMDAL
 121         if ((problem = krb5_cc_gen_new(krb_context, &krb5_fcc_ops, &ccache))) {
 122                 logit("krb5_cc_gen_new(): %.100s",
 123                     krb5_get_err_text(krb_context, problem));
 124                 return;
 125         }
 126 #else
 127         {
 128                 int tmpfd;
 129                 char ccname[40];
 130
 131                 snprintf(ccname, sizeof(ccname),
 132                     "FILE:/tmp/krb5cc_%d_XXXXXX", geteuid());
 133
 134                 if ((tmpfd = mkstemp(ccname + strlen("FILE:"))) == -1) {
 135                         logit("mkstemp(): %.100s", strerror(errno));
 136                         problem = errno;
 137                         return;
 138                 }
 139                 if (fchmod(tmpfd, S_IRUSR | S_IWUSR) == -1) {
 140                         logit("fchmod(): %.100s", strerror(errno));
 141                         close(tmpfd);
 142                         problem = errno;
 143                         return;
 144                 }
 145                 close(tmpfd);
 146                 if ((problem = krb5_cc_resolve(krb_context, ccname, &ccache))) {
 147                         logit("krb5_cc_resolve(): %.100s",
 148                             krb5_get_err_text(krb_context, problem));
 149                         return;
 150                 }
 151         }
 152 #endif  /* #ifdef HEIMDAL */
 153
 154         if ((problem = krb5_parse_name(krb_context,
 155             client->exportedname.value, &princ))) {
 156                 logit("krb5_parse_name(): %.100s",
 157                     krb5_get_err_text(krb_context, problem));
 158                 krb5_cc_destroy(krb_context, ccache);
 159                 return;
 160         }
 161
 162         if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
 163                 logit("krb5_cc_initialize(): %.100s",
 164                     krb5_get_err_text(krb_context, problem));
 165                 krb5_free_principal(krb_context, princ);
 166                 krb5_cc_destroy(krb_context, ccache);
 167                 return;
 168         }
 169
 170         krb5_free_principal(krb_context, princ);
 171
 172         if ((maj_status = gss_krb5_copy_ccache(&min_status,
 173             client->creds, ccache))) {
 174                 logit("gss_krb5_copy_ccache() failed");
 175                 krb5_cc_destroy(krb_context, ccache);
 176                 return;
 177         }
 178
 179         client->store.filename = xstrdup(krb5_cc_get_name(krb_context, ccache));
 180         client->store.envvar = "KRB5CCNAME";
 181         client->store.envval = xstrdup(client->store.filename);
 182
 183 #ifdef USE_PAM
 184         if (options.use_pam)
 185                 do_pam_putenv(client->store.envvar,client->store.envval);
 186 #endif
 187
 188         krb5_cc_close(krb_context, ccache);
 189
 190         return;
 191 }
 192
 193 ssh_gssapi_mech gssapi_kerberos_mech = {
 194         "toWM5Slw5Ew8Mqkay+al2g==",
 195         "Kerberos",
 196         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
 197         NULL,
 198         &ssh_gssapi_krb5_userok,
 199         NULL,
 200         &ssh_gssapi_krb5_storecreds
 201 };
 202
 203 #endif /* KRB5 */
 204
 205 #endif /* GSSAPI */