crypto/openssh/auth-krb5.c

   1 /* $OpenBSD: auth-krb5.c,v 1.24 2021/04/03 06:18:40 djm Exp $ */
   2 /*
   3  *    Kerberos v5 authentication and ticket-passing routines.
   4  *
   5  * From: FreeBSD: src/crypto/openssh/auth-krb5.c,v 1.6 2001/02/13 16:58:04 assar
   6  */
   7 /*
   8  * Copyright (c) 2002 Daniel Kouril.  All rights reserved.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #include "includes.h"
  32
  33 #include <sys/types.h>
  34 #include <pwd.h>
  35 #include <stdarg.h>
  36
  37 #include "xmalloc.h"
  38 #include "ssh.h"
  39 #include "packet.h"
  40 #include "log.h"
  41 #include "sshbuf.h"
  42 #include "sshkey.h"
  43 #include "misc.h"
  44 #include "servconf.h"
  45 #include "uidswap.h"
  46 #include "hostfile.h"
  47 #include "auth.h"
  48
  49 #ifdef KRB5
  50 #include <errno.h>
  51 #include <unistd.h>
  52 #include <string.h>
  53 #include <krb5.h>
  54
  55 extern ServerOptions     options;
  56
  57 static int
  58 krb5_init(void *context)
  59 {
  60         Authctxt *authctxt = (Authctxt *)context;
  61         krb5_error_code problem;
  62
  63         if (authctxt->krb5_ctx == NULL) {
  64                 problem = krb5_init_context(&authctxt->krb5_ctx);
  65                 if (problem)
  66                         return (problem);
  67         }
  68         return (0);
  69 }
  70
  71 int
  72 auth_krb5_password(Authctxt *authctxt, const char *password)
  73 {
  74 #ifndef HEIMDAL
  75         krb5_creds creds;
  76         krb5_principal server;
  77 #endif
  78         krb5_error_code problem;
  79         krb5_ccache ccache = NULL;
  80         int len;
  81         char *client, *platform_client;
  82         const char *errmsg;
  83
  84         /* get platform-specific kerberos client principal name (if it exists) */
  85         platform_client = platform_krb5_get_principal_name(authctxt->pw->pw_name);
  86         client = platform_client ? platform_client : authctxt->pw->pw_name;
  87
  88         temporarily_use_uid(authctxt->pw);
  89
  90         problem = krb5_init(authctxt);
  91         if (problem)
  92                 goto out;
  93
  94         problem = krb5_parse_name(authctxt->krb5_ctx, client,
  95                     &authctxt->krb5_user);
  96         if (problem)
  97                 goto out;
  98
  99 #ifdef HEIMDAL
 100 # ifdef HAVE_KRB5_CC_NEW_UNIQUE
 101         problem = krb5_cc_new_unique(authctxt->krb5_ctx,
 102             krb5_mcc_ops.prefix, NULL, &ccache);
 103 # else
 104         problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_mcc_ops, &ccache);
 105 # endif
 106         if (problem)
 107                 goto out;
 108
 109         problem = krb5_cc_initialize(authctxt->krb5_ctx, ccache,
 110                 authctxt->krb5_user);
 111         if (problem)
 112                 goto out;
 113
 114         restore_uid();
 115
 116         problem = krb5_verify_user(authctxt->krb5_ctx, authctxt->krb5_user,
 117             ccache, password, 1, NULL);
 118
 119         temporarily_use_uid(authctxt->pw);
 120
 121         if (problem)
 122                 goto out;
 123
 124 # ifdef HAVE_KRB5_CC_NEW_UNIQUE
 125         problem = krb5_cc_new_unique(authctxt->krb5_ctx,
 126             krb5_fcc_ops.prefix, NULL, &authctxt->krb5_fwd_ccache);
 127 # else
 128         problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_fcc_ops,
 129             &authctxt->krb5_fwd_ccache);
 130 # endif
 131         if (problem)
 132                 goto out;
 133
 134         problem = krb5_cc_copy_cache(authctxt->krb5_ctx, ccache,
 135             authctxt->krb5_fwd_ccache);
 136         krb5_cc_destroy(authctxt->krb5_ctx, ccache);
 137         ccache = NULL;
 138         if (problem)
 139                 goto out;
 140
 141 #else
 142         problem = krb5_get_init_creds_password(authctxt->krb5_ctx, &creds,
 143             authctxt->krb5_user, (char *)password, NULL, NULL, 0, NULL, NULL);
 144         if (problem)
 145                 goto out;
 146
 147         problem = krb5_sname_to_principal(authctxt->krb5_ctx, NULL, NULL,
 148             KRB5_NT_SRV_HST, &server);
 149         if (problem)
 150                 goto out;
 151
 152         restore_uid();
 153         problem = krb5_verify_init_creds(authctxt->krb5_ctx, &creds, server,
 154             NULL, NULL, NULL);
 155         krb5_free_principal(authctxt->krb5_ctx, server);
 156         temporarily_use_uid(authctxt->pw);
 157         if (problem)
 158                 goto out;
 159
 160         if (!krb5_kuserok(authctxt->krb5_ctx, authctxt->krb5_user,
 161             authctxt->pw->pw_name)) {
 162                 problem = -1;
 163                 goto out;
 164         }
 165
 166         problem = ssh_krb5_cc_gen(authctxt->krb5_ctx,
 167             &authctxt->krb5_fwd_ccache);
 168         if (problem)
 169                 goto out;
 170
 171         problem = krb5_cc_initialize(authctxt->krb5_ctx,
 172             authctxt->krb5_fwd_ccache, authctxt->krb5_user);
 173         if (problem)
 174                 goto out;
 175
 176         problem = krb5_cc_store_cred(authctxt->krb5_ctx,
 177             authctxt->krb5_fwd_ccache, &creds);
 178         if (problem)
 179                 goto out;
 180 #endif
 181
 182         authctxt->krb5_ticket_file = (char *)krb5_cc_get_name(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);
 183
 184         len = strlen(authctxt->krb5_ticket_file) + 6;
 185         authctxt->krb5_ccname = xmalloc(len);
 186         snprintf(authctxt->krb5_ccname, len, "FILE:%s",
 187             authctxt->krb5_ticket_file);
 188
 189 #ifdef USE_PAM
 190         if (options.use_pam)
 191                 do_pam_putenv("KRB5CCNAME", authctxt->krb5_ccname);
 192 #endif
 193
 194  out:
 195         restore_uid();
 196
 197         free(platform_client);
 198
 199         if (problem) {
 200                 if (ccache)
 201                         krb5_cc_destroy(authctxt->krb5_ctx, ccache);
 202
 203                 if (authctxt->krb5_ctx != NULL && problem!=-1) {
 204                         errmsg = krb5_get_error_message(authctxt->krb5_ctx,
 205                             problem);
 206                         debug("Kerberos password authentication failed: %s",
 207                             errmsg);
 208                         krb5_free_error_message(authctxt->krb5_ctx, errmsg);
 209                 } else
 210                         debug("Kerberos password authentication failed: %d",
 211                             problem);
 212
 213                 krb5_cleanup_proc(authctxt);
 214
 215                 if (options.kerberos_or_local_passwd)
 216                         return (-1);
 217                 else
 218                         return (0);
 219         }
 220         return (authctxt->valid ? 1 : 0);
 221 }
 222
 223 void
 224 krb5_cleanup_proc(Authctxt *authctxt)
 225 {
 226         debug("krb5_cleanup_proc called");
 227         if (authctxt->krb5_fwd_ccache) {
 228                 krb5_cc_destroy(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);
 229                 authctxt->krb5_fwd_ccache = NULL;
 230         }
 231         if (authctxt->krb5_user) {
 232                 krb5_free_principal(authctxt->krb5_ctx, authctxt->krb5_user);
 233                 authctxt->krb5_user = NULL;
 234         }
 235         if (authctxt->krb5_ctx) {
 236                 krb5_free_context(authctxt->krb5_ctx);
 237                 authctxt->krb5_ctx = NULL;
 238         }
 239 }
 240
 241 #ifndef HEIMDAL
 242 krb5_error_code
 243 ssh_krb5_cc_gen(krb5_context ctx, krb5_ccache *ccache) {
 244         int tmpfd, ret, oerrno;
 245         char ccname[40];
 246         mode_t old_umask;
 247
 248         ret = snprintf(ccname, sizeof(ccname),
 249             "FILE:/tmp/krb5cc_%d_XXXXXXXXXX", geteuid());
 250         if (ret < 0 || (size_t)ret >= sizeof(ccname))
 251                 return ENOMEM;
 252
 253         old_umask = umask(0177);
 254         tmpfd = mkstemp(ccname + strlen("FILE:"));
 255         oerrno = errno;
 256         umask(old_umask);
 257         if (tmpfd == -1) {
 258                 logit("mkstemp(): %.100s", strerror(oerrno));
 259                 return oerrno;
 260         }
 261
 262         if (fchmod(tmpfd,S_IRUSR | S_IWUSR) == -1) {
 263                 oerrno = errno;
 264                 logit("fchmod(): %.100s", strerror(oerrno));
 265                 close(tmpfd);
 266                 return oerrno;
 267         }
 268         close(tmpfd);
 269
 270         return (krb5_cc_resolve(ctx, ccname, ccache));
 271 }
 272 #endif /* !HEIMDAL */
 273 #endif /* KRB5 */