openssh/gss-serv-krb5.c

   1 /*      $OpenBSD: gss-serv-krb5.c,v 1.1 2003/08/22 10:56:09 markus 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 /* Retrieve the local username associated with a set of Kerberos
 102  * credentials. Hopefully we can use this for the 'empty' username
 103  * logins discussed in the draft  */
 104 static int
 105 ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user) {
 106         krb5_principal princ;
 107         int retval;
 108
 109         if (ssh_gssapi_krb5_init() == 0)
 110                 return 0;
 111
 112         if ((retval=krb5_parse_name(krb_context, client->displayname.value,
 113                                     &princ))) {
 114                 logit("krb5_parse_name(): %.100s",
 115                         krb5_get_err_text(krb_context,retval));
 116                 return 0;
 117         }
 118
 119         /* We've got to return a malloc'd string */
 120         *user = (char *)xmalloc(256);
 121         if (krb5_aname_to_localname(krb_context, princ, 256, *user)) {
 122                 xfree(*user);
 123                 *user = NULL;
 124                 return(0);
 125         }
 126
 127         return(1);
 128 }
 129
 130 /* This writes out any forwarded credentials from the structure populated
 131  * during userauth. Called after we have setuid to the user */
 132
 133 static void
 134 ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
 135 {
 136         krb5_ccache ccache;
 137         krb5_error_code problem;
 138         krb5_principal princ;
 139         OM_uint32 maj_status, min_status;
 140         gss_cred_id_t krb5_cred_handle;
 141
 142
 143         if (client->creds == NULL) {
 144                 debug("No credentials stored");
 145                 return;
 146         }
 147
 148         if (ssh_gssapi_krb5_init() == 0)
 149                 return;
 150
 151 #ifdef HEIMDAL
 152         if ((problem = krb5_cc_gen_new(krb_context, &krb5_fcc_ops, &ccache))) {
 153                 logit("krb5_cc_gen_new(): %.100s",
 154                     krb5_get_err_text(krb_context, problem));
 155                 return;
 156         }
 157 #else
 158         {
 159                 int tmpfd;
 160                 char ccname[40];
 161
 162                 snprintf(ccname, sizeof(ccname),
 163                     "FILE:/tmp/krb5cc_%d_XXXXXX", geteuid());
 164
 165                 if ((tmpfd = mkstemp(ccname + strlen("FILE:"))) == -1) {
 166                         logit("mkstemp(): %.100s", strerror(errno));
 167                         problem = errno;
 168                         return;
 169                 }
 170                 if (fchmod(tmpfd, S_IRUSR | S_IWUSR) == -1) {
 171                         logit("fchmod(): %.100s", strerror(errno));
 172                         close(tmpfd);
 173                         problem = errno;
 174                         return;
 175                 }
 176                 close(tmpfd);
 177                 if ((problem = krb5_cc_resolve(krb_context, ccname, &ccache))) {
 178                         logit("krb5_cc_resolve(): %.100s",
 179                             krb5_get_err_text(krb_context, problem));
 180                         return;
 181                 }
 182         }
 183 #endif  /* #ifdef HEIMDAL */
 184
 185         if ((problem = krb5_parse_name(krb_context,
 186             client->exportedname.value, &princ))) {
 187                 logit("krb5_parse_name(): %.100s",
 188                     krb5_get_err_text(krb_context, problem));
 189                 krb5_cc_destroy(krb_context, ccache);
 190                 return;
 191         }
 192
 193         if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
 194                 logit("krb5_cc_initialize(): %.100s",
 195                     krb5_get_err_text(krb_context, problem));
 196                 krb5_free_principal(krb_context, princ);
 197                 krb5_cc_destroy(krb_context, ccache);
 198                 return;
 199         }
 200
 201         krb5_free_principal(krb_context, princ);
 202
 203 #ifdef MECHGLUE
 204         krb5_cred_handle =
 205             __gss_get_mechanism_cred(client->creds,
 206                                      &(gssapi_kerberos_mech.oid));
 207 #else
 208         krb5_cred_handle = client->creds;
 209 #endif
 210
 211         if ((maj_status = gss_krb5_copy_ccache(&min_status,
 212             krb5_cred_handle, ccache))) {
 213                 logit("gss_krb5_copy_ccache() failed");
 214                 krb5_cc_destroy(krb_context, ccache);
 215                 return;
 216         }
 217
 218         client->store.filename = xstrdup(krb5_cc_get_name(krb_context, ccache));
 219         client->store.envvar = "KRB5CCNAME";
 220         client->store.envval = xstrdup(client->store.filename);
 221
 222 #ifdef USE_PAM
 223         if (options.use_pam)
 224                 do_pam_putenv(client->store.envvar,client->store.envval);
 225 #endif
 226
 227         krb5_cc_close(krb_context, ccache);
 228
 229         return;
 230 }
 231
 232 ssh_gssapi_mech gssapi_kerberos_mech = {
 233         "toWM5Slw5Ew8Mqkay+al2g==",
 234         "Kerberos",
 235         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
 236         NULL,
 237         &ssh_gssapi_krb5_userok,
 238         &ssh_gssapi_krb5_localname,
 239         &ssh_gssapi_krb5_storecreds
 240 };
 241
 242 ssh_gssapi_mech gssapi_kerberos_mech_old = {
 243         "Se3H81ismmOC3OE+FwYCiQ==",
 244         "Kerberos",
 245         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
 246         &ssh_gssapi_krb5_init,
 247         &ssh_gssapi_krb5_userok,
 248         &ssh_gssapi_krb5_localname,
 249         &ssh_gssapi_krb5_storecreds
 250 };
 251
 252 #endif /* KRB5 */
 253
 254 #endif /* GSSAPI */