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 krb5_context krb_context = NULL;
  48
  49 /* Initialise the krb5 library, so we can use it for those bits that
  50  * GSSAPI won't do */
  51
  52 static int
  53 ssh_gssapi_krb5_init() {
  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                 log("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         krb5_principal princ;
  77         int retval;
  78
  79         if (ssh_gssapi_krb5_init() == 0)
  80                 return 0;
  81
  82         if ((retval=krb5_parse_name(krb_context, client->name.value,
  83                                     &princ))) {
  84                 log("krb5_parse_name(): %.100s",
  85                         krb5_get_err_text(krb_context,retval));
  86                 return 0;
  87         }
  88         if (krb5_kuserok(krb_context, princ, name)) {
  89                 retval = 1;
  90                 log("Authorized to %s, krb5 principal %s (krb5_kuserok)",name,
  91                     (char *)client->name.value);
  92         }
  93         else
  94                 retval = 0;
  95
  96         krb5_free_principal(krb_context, princ);
  97         return retval;
  98 }
  99
 100 /* Retrieve the local username associated with a set of Kerberos
 101  * credentials. Hopefully we can use this for the 'empty' username
 102  * logins discussed in the draft  */
 103 static int
 104 ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user) {
 105         krb5_principal princ;
 106         int retval;
 107
 108         if (ssh_gssapi_krb5_init() == 0)
 109                 return 0;
 110
 111         if ((retval=krb5_parse_name(krb_context, client->name.value,
 112                                     &princ))) {
 113                 log("krb5_parse_name(): %.100s",
 114                         krb5_get_err_text(krb_context,retval));
 115                 return 0;
 116         }
 117
 118         /* We've got to return a malloc'd string */
 119         *user = (char *)xmalloc(256);
 120         if (krb5_aname_to_localname(krb_context, princ, 256, *user)) {
 121                 xfree(*user);
 122                 *user = NULL;
 123                 return(0);
 124         }
 125
 126         return(1);
 127 }
 128
 129 /* Make sure that this is called _after_ we've setuid to the user */
 130
 131 /* This writes out any forwarded credentials. Its specific to the Kerberos
 132  * GSSAPI mechanism
 133  *
 134  * We assume that our caller has made sure that the user has selected
 135  * delegated credentials, and that the client_creds structure is correctly
 136  * populated.
 137  */
 138
 139 static void
 140 ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client) {
 141         krb5_ccache ccache;
 142         krb5_error_code problem;
 143         krb5_principal princ;
 144         char ccname[35];
 145         static char name[40];
 146         int tmpfd;
 147         OM_uint32 maj_status,min_status;
 148
 149         if (client->creds==NULL) {
 150                 debug("No credentials stored");
 151                 return;
 152         }
 153
 154         if (ssh_gssapi_krb5_init() == 0)
 155                 return;
 156
 157         if (options.gss_use_session_ccache) {
 158                 snprintf(ccname,sizeof(ccname),"/tmp/krb5cc_%d_XXXXXX",geteuid());
 159
 160                 if ((tmpfd = mkstemp(ccname))==-1) {
 161                         log("mkstemp(): %.100s", strerror(errno));
 162                         return;
 163                 }
 164                 if (fchmod(tmpfd, S_IRUSR | S_IWUSR) == -1) {
 165                         log("fchmod(): %.100s", strerror(errno));
 166                         close(tmpfd);
 167                         return;
 168                 }
 169         } else {
 170                 snprintf(ccname,sizeof(ccname),"/tmp/krb5cc_%d",geteuid());
 171                 tmpfd = open(ccname, O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR);
 172                 if (tmpfd == -1) {
 173                         log("open(): %.100s", strerror(errno));
 174                         return;
 175                 }
 176         }
 177
 178         close(tmpfd);
 179         snprintf(name, sizeof(name), "FILE:%s",ccname);
 180
 181         if ((problem = krb5_cc_resolve(krb_context, name, &ccache))) {
 182                 log("krb5_cc_default(): %.100s",
 183                         krb5_get_err_text(krb_context,problem));
 184                 return;
 185         }
 186
 187         if ((problem = krb5_parse_name(krb_context, client->name.value,
 188                                        &princ))) {
 189                 log("krb5_parse_name(): %.100s",
 190                         krb5_get_err_text(krb_context,problem));
 191                 krb5_cc_destroy(krb_context,ccache);
 192                 return;
 193         }
 194
 195         if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
 196                 log("krb5_cc_initialize(): %.100s",
 197                         krb5_get_err_text(krb_context,problem));
 198                 krb5_free_principal(krb_context,princ);
 199                 krb5_cc_destroy(krb_context,ccache);
 200                 return;
 201         }
 202
 203         krb5_free_principal(krb_context,princ);
 204
 205         #ifdef HEIMDAL
 206         if ((problem = krb5_cc_copy_cache(krb_context,
 207                                            client->creds->ccache,
 208                                            ccache))) {
 209                 log("krb5_cc_copy_cache(): %.100s",
 210                         krb5_get_err_text(krb_context,problem));
 211                 krb5_cc_destroy(krb_context,ccache);
 212                 return;
 213         }
 214         #else
 215         if ((maj_status = gss_krb5_copy_ccache(&min_status,
 216                                                client->creds,
 217                                                ccache))) {
 218                 log("gss_krb5_copy_ccache() failed");
 219                 krb5_cc_destroy(krb_context,ccache);
 220                 return;
 221         }
 222         #endif
 223
 224         krb5_cc_close(krb_context,ccache);
 225
 226 #ifdef USE_PAM
 227         do_pam_putenv("KRB5CCNAME",name);
 228 #endif
 229
 230         client->store.filename=strdup(ccname);
 231         client->store.envvar="KRB5CCNAME";
 232         client->store.envval=strdup(name);
 233
 234         return;
 235 }
 236
 237 /* We've been using a wrongly encoded mechanism ID for yonks */
 238
 239 ssh_gssapi_mech gssapi_kerberos_mech_old = {
 240         "Se3H81ismmOC3OE+FwYCiQ==",
 241         "Kerberos",
 242         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
 243         &ssh_gssapi_krb5_init,
 244         &ssh_gssapi_krb5_userok,
 245         &ssh_gssapi_krb5_localname,
 246         &ssh_gssapi_krb5_storecreds
 247 };
 248
 249 ssh_gssapi_mech gssapi_kerberos_mech = {
 250         "toWM5Slw5Ew8Mqkay+al2g==",
 251         "Kerberos",
 252         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
 253         NULL,
 254         &ssh_gssapi_krb5_userok,
 255         &ssh_gssapi_krb5_localname,
 256         &ssh_gssapi_krb5_storecreds
 257 };
 258
 259 #endif /* KRB5 */
 260
 261 #endif /* GSSAPI */