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 #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 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 #ifdef KRB5_INIT_ETS
  83         krb5_init_ets(krb_context);
  84 #endif
  85
  86         return 1;
  87 }
  88
  89 /* Check if this user is OK to login. This only works with krb5 - other
  90  * GSSAPI mechanisms will need their own.
  91  * Returns true if the user is OK to log in, otherwise returns 0
  92  */
  93
  94 static int
  95 ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name)
  96 {
  97         krb5_principal princ;
  98         int retval;
  99
 100         if (ssh_gssapi_krb5_init() == 0)
 101                 return 0;
 102
 103         if ((retval = krb5_parse_name(krb_context, client->exportedname.value,
 104             &princ))) {
 105                 logit("krb5_parse_name(): %.100s",
 106                     krb5_get_err_text(krb_context, retval));
 107                 return 0;
 108         }
 109         if (krb5_kuserok(krb_context, princ, name)) {
 110                 retval = 1;
 111                 logit("Authorized to %s, krb5 principal %s (krb5_kuserok)",
 112                     name, (char *)client->displayname.value);
 113         } else
 114                 retval = 0;
 115
 116         krb5_free_principal(krb_context, princ);
 117         return retval;
 118 }
 119
 120
 121 /* Retrieve the local username associated with a set of Kerberos
 122  * credentials. Hopefully we can use this for the 'empty' username
 123  * logins discussed in the draft  */
 124 static int
 125 ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user) {
 126         krb5_principal princ;
 127         int retval;
 128
 129         if (ssh_gssapi_krb5_init() == 0)
 130                 return 0;
 131
 132         if ((retval=krb5_parse_name(krb_context, client->displayname.value,
 133                                     &princ))) {
 134                 logit("krb5_parse_name(): %.100s",
 135                         krb5_get_err_text(krb_context,retval));
 136                 return 0;
 137         }
 138
 139         /* We've got to return a malloc'd string */
 140         *user = (char *)xmalloc(256);
 141         if (krb5_aname_to_localname(krb_context, princ, 256, *user)) {
 142                 xfree(*user);
 143                 *user = NULL;
 144                 return(0);
 145         }
 146
 147         return(1);
 148 }
 149
 150 /* This writes out any forwarded credentials from the structure populated
 151  * during userauth. Called after we have setuid to the user */
 152
 153 static void
 154 ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
 155 {
 156         krb5_ccache ccache;
 157         krb5_error_code problem;
 158         krb5_principal princ;
 159         OM_uint32 maj_status, min_status;
 160         gss_cred_id_t krb5_cred_handle;
 161         int len;
 162
 163         if (client->creds == NULL) {
 164                 debug("No credentials stored");
 165                 return;
 166         }
 167
 168         if (ssh_gssapi_krb5_init() == 0)
 169                 return;
 170
 171 #ifdef HEIMDAL
 172         if ((problem = krb5_cc_gen_new(krb_context, &krb5_fcc_ops, &ccache))) {
 173                 logit("krb5_cc_gen_new(): %.100s",
 174                     krb5_get_err_text(krb_context, problem));
 175                 return;
 176         }
 177 #else
 178         {
 179                 int tmpfd;
 180                 char ccname[40];
 181                 mode_t old_umask;
 182
 183                 snprintf(ccname, sizeof(ccname),
 184                     "FILE:/tmp/krb5cc_%d_XXXXXX", geteuid());
 185
 186                 old_umask = umask(0177);
 187                 tmpfd = mkstemp(ccname + strlen("FILE:"));
 188                 umask(old_umask);
 189                 if (tmpfd == -1) {
 190                         logit("mkstemp(): %.100s", strerror(errno));
 191                         problem = errno;
 192                         return;
 193                 }
 194                 if (fchmod(tmpfd, S_IRUSR | S_IWUSR) == -1) {
 195                         logit("fchmod(): %.100s", strerror(errno));
 196                         close(tmpfd);
 197                         problem = errno;
 198                         return;
 199                 }
 200                 close(tmpfd);
 201                 if ((problem = krb5_cc_resolve(krb_context, ccname, &ccache))) {
 202                         logit("krb5_cc_resolve(): %.100s",
 203                             krb5_get_err_text(krb_context, problem));
 204                         return;
 205                 }
 206         }
 207 #endif  /* #ifdef HEIMDAL */
 208
 209         if ((problem = krb5_parse_name(krb_context,
 210             client->exportedname.value, &princ))) {
 211                 logit("krb5_parse_name(): %.100s",
 212                     krb5_get_err_text(krb_context, problem));
 213                 krb5_cc_destroy(krb_context, ccache);
 214                 return;
 215         }
 216
 217         if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
 218                 logit("krb5_cc_initialize(): %.100s",
 219                     krb5_get_err_text(krb_context, problem));
 220                 krb5_free_principal(krb_context, princ);
 221                 krb5_cc_destroy(krb_context, ccache);
 222                 return;
 223         }
 224
 225         krb5_free_principal(krb_context, princ);
 226
 227 #ifdef MECHGLUE
 228         krb5_cred_handle =
 229             __gss_get_mechanism_cred(client->creds,
 230                                      &(gssapi_kerberos_mech.oid));
 231 #else
 232         krb5_cred_handle = client->creds;
 233 #endif
 234
 235         if ((maj_status = gss_krb5_copy_ccache(&min_status,
 236             krb5_cred_handle, ccache))) {
 237                 logit("gss_krb5_copy_ccache() failed");
 238                 krb5_cc_destroy(krb_context, ccache);
 239                 return;
 240         }
 241
 242         client->store.filename = xstrdup(krb5_cc_get_name(krb_context, ccache));
 243         client->store.envvar = "KRB5CCNAME";
 244         len = strlen(client->store.filename) + 6;
 245         client->store.envval = xmalloc(len);
 246         snprintf(client->store.envval, len, "FILE:%s", client->store.filename);
 247
 248 #ifdef USE_PAM
 249         if (options.use_pam)
 250                 do_pam_putenv(client->store.envvar, client->store.envval);
 251 #endif
 252
 253         krb5_cc_close(krb_context, ccache);
 254
 255         return;
 256 }
 257
 258 #endif /* KRB5 */
 259
 260 #endif /* GSSAPI */