openssh/gss-serv-krb5.c

   1 /*
   2  * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
  14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  23  */
  24
  25 #include "includes.h"
  26
  27 #ifdef GSSAPI
  28 #ifdef KRB5
  29
  30 #include "auth.h"
  31 #include "auth-pam.h"
  32 #include "xmalloc.h"
  33 #include "log.h"
  34 #include "servconf.h"
  35
  36 #include "ssh-gss.h"
  37
  38 extern ServerOptions options;
  39
  40 #ifdef HEIMDAL
  41 #include <krb5.h>
  42 #else
  43 #include <gssapi_krb5.h>
  44 #define krb5_get_err_text(context,code) error_message(code)
  45 #endif
  46
  47 static int ssh_gssapi_krb5_init();
  48 static int ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name);
  49 static int ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user);
  50 static void ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client);
  51
  52 static krb5_context krb_context = NULL;
  53
  54 /* We've been using a wrongly encoded mechanism ID for yonks */
  55
  56 ssh_gssapi_mech gssapi_kerberos_mech_old = {
  57         "Se3H81ismmOC3OE+FwYCiQ==",
  58         "Kerberos",
  59         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
  60         &ssh_gssapi_krb5_init,
  61         &ssh_gssapi_krb5_userok,
  62         &ssh_gssapi_krb5_localname,
  63         &ssh_gssapi_krb5_storecreds
  64 };
  65
  66 ssh_gssapi_mech gssapi_kerberos_mech = {
  67         "toWM5Slw5Ew8Mqkay+al2g==",
  68         "Kerberos",
  69         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
  70         NULL,
  71         &ssh_gssapi_krb5_userok,
  72         &ssh_gssapi_krb5_localname,
  73         &ssh_gssapi_krb5_storecreds
  74 };
  75
  76 /* Initialise the krb5 library, so we can use it for those bits that
  77  * GSSAPI won't do */
  78
  79 static int
  80 ssh_gssapi_krb5_init() {
  81         krb5_error_code problem;
  82
  83         if (krb_context !=NULL)
  84                 return 1;
  85
  86         problem = krb5_init_context(&krb_context);
  87         if (problem) {
  88                 log("Cannot initialize krb5 context");
  89                 return 0;
  90         }
  91         krb5_init_ets(krb_context);
  92
  93         return 1;
  94 }
  95
  96 /* Check if this user is OK to login. This only works with krb5 - other
  97  * GSSAPI mechanisms will need their own.
  98  * Returns true if the user is OK to log in, otherwise returns 0
  99  */
 100
 101 static int
 102 ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name) {
 103         krb5_principal princ;
 104         int retval;
 105
 106         if (ssh_gssapi_krb5_init() == 0)
 107                 return 0;
 108
 109         if ((retval=krb5_parse_name(krb_context, client->name.value,
 110                                     &princ))) {
 111                 log("krb5_parse_name(): %.100s",
 112                         krb5_get_err_text(krb_context,retval));
 113                 return 0;
 114         }
 115         if (krb5_kuserok(krb_context, princ, name)) {
 116                 retval = 1;
 117                 log("Authorized to %s, krb5 principal %s (krb5_kuserok)",name,
 118                     (char *)client->name.value);
 119         }
 120         else
 121                 retval = 0;
 122
 123         krb5_free_principal(krb_context, princ);
 124         return retval;
 125 }
 126
 127 /* Retrieve the local username associated with a set of Kerberos
 128  * credentials. Hopefully we can use this for the 'empty' username
 129  * logins discussed in the draft  */
 130 static int
 131 ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user) {
 132         krb5_principal princ;
 133         int retval;
 134
 135         if (ssh_gssapi_krb5_init() == 0)
 136                 return 0;
 137
 138         if ((retval=krb5_parse_name(krb_context, client->name.value,
 139                                     &princ))) {
 140                 log("krb5_parse_name(): %.100s",
 141                         krb5_get_err_text(krb_context,retval));
 142                 return 0;
 143         }
 144
 145         /* We've got to return a malloc'd string */
 146         *user = (char *)xmalloc(256);
 147         if (krb5_aname_to_localname(krb_context, princ, 256, *user)) {
 148                 xfree(*user);
 149                 *user = NULL;
 150                 return(0);
 151         }
 152
 153         return(1);
 154 }
 155
 156 /* Make sure that this is called _after_ we've setuid to the user */
 157
 158 /* This writes out any forwarded credentials. Its specific to the Kerberos
 159  * GSSAPI mechanism
 160  *
 161  * We assume that our caller has made sure that the user has selected
 162  * delegated credentials, and that the client_creds structure is correctly
 163  * populated.
 164  */
 165
 166 static void
 167 ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client) {
 168         krb5_ccache ccache;
 169         krb5_error_code problem;
 170         krb5_principal princ;
 171         char ccname[35];
 172         static char name[40];
 173         int tmpfd;
 174         OM_uint32 maj_status,min_status;
 175         gss_cred_id_t krb5_cred_handle;
 176
 177         if (client->creds==NULL) {
 178                 debug("No credentials stored");
 179                 return;
 180         }
 181
 182         if (ssh_gssapi_krb5_init() == 0)
 183                 return;
 184
 185         if (options.gss_use_session_ccache) {
 186                 snprintf(ccname,sizeof(ccname),"/tmp/krb5cc_%d_XXXXXX",geteuid());
 187
 188                 if ((tmpfd = mkstemp(ccname))==-1) {
 189                         log("mkstemp(): %.100s", strerror(errno));
 190                         return;
 191                 }
 192                 if (fchmod(tmpfd, S_IRUSR | S_IWUSR) == -1) {
 193                         log("fchmod(): %.100s", strerror(errno));
 194                         close(tmpfd);
 195                         return;
 196                 }
 197         } else {
 198                 snprintf(ccname,sizeof(ccname),"/tmp/krb5cc_%d",geteuid());
 199                 tmpfd = open(ccname, O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR);
 200                 if (tmpfd == -1) {
 201                         log("open(): %.100s", strerror(errno));
 202                         return;
 203                 }
 204         }
 205
 206         close(tmpfd);
 207         snprintf(name, sizeof(name), "FILE:%s",ccname);
 208
 209         if ((problem = krb5_cc_resolve(krb_context, name, &ccache))) {
 210                 log("krb5_cc_default(): %.100s",
 211                         krb5_get_err_text(krb_context,problem));
 212                 return;
 213         }
 214
 215         if ((problem = krb5_parse_name(krb_context, client->name.value,
 216                                        &princ))) {
 217                 log("krb5_parse_name(): %.100s",
 218                         krb5_get_err_text(krb_context,problem));
 219                 krb5_cc_destroy(krb_context,ccache);
 220                 return;
 221         }
 222
 223         if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
 224                 log("krb5_cc_initialize(): %.100s",
 225                         krb5_get_err_text(krb_context,problem));
 226                 krb5_free_principal(krb_context,princ);
 227                 krb5_cc_destroy(krb_context,ccache);
 228                 return;
 229         }
 230
 231         krb5_free_principal(krb_context,princ);
 232
 233 #ifdef MECHGLUE
 234         krb5_cred_handle =
 235             __gss_get_mechanism_cred(client->creds,
 236                                      &(gssapi_kerberos_mech.oid));
 237 #else
 238         krb5_cred_handle = client->creds;
 239 #endif
 240
 241         if ((maj_status = gss_krb5_copy_ccache(&min_status,
 242                                                client->creds,
 243                                                ccache))) {
 244                 log("gss_krb5_copy_ccache() failed");
 245                 krb5_cc_destroy(krb_context,ccache);
 246                 return;
 247         }
 248
 249         krb5_cc_close(krb_context,ccache);
 250
 251 #ifdef USE_PAM
 252         do_pam_putenv("KRB5CCNAME",name);
 253 #endif
 254
 255         client->store.filename=strdup(ccname);
 256         client->store.envvar="KRB5CCNAME";
 257         client->store.envval=strdup(name);
 258
 259         return;
 260 }
 261
 262 #endif /* KRB5 */
 263
 264 #endif /* GSSAPI */