source/client/cifs.upcall.c

   1 /*
   2 * CIFS user-space helper.
   3 * Copyright (C) Igor Mammedov (niallain@gmail.com) 2007
   4 *
   5 * Used by /sbin/request-key for handling
   6 * cifs upcall for kerberos authorization of access to share and
   7 * cifs upcall for DFS srver name resolving (IPv4/IPv6 aware).
   8 * You should have keyutils installed and add something like the
   9 * following lines to /etc/request-key.conf file:
  10
  11 create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
  12 create dns_resolver * * /usr/local/sbin/cifs.upcall %k
  13
  14 * This program is free software; you can redistribute it and/or modify
  15 * it under the terms of the GNU General Public License as published by
  16 * the Free Software Foundation; either version 2 of the License, or
  17 * (at your option) any later version.
  18 * This program is distributed in the hope that it will be useful,
  19 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  21 * GNU General Public License for more details.
  22 * You should have received a copy of the GNU General Public License
  23 * along with this program; if not, write to the Free Software
  24 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  25 */
  26
  27 #include "includes.h"
  28 #include <keyutils.h>
  29
  30 #include "cifs_spnego.h"
  31
  32 const char *CIFSSPNEGO_VERSION = "1.2";
  33 static const char *prog = "cifs.upcall";
  34 typedef enum _secType {
  35         KRB5,
  36         MS_KRB5
  37 } secType_t;
  38
  39 /*
  40  * Prepares AP-REQ data for mechToken and gets session key
  41  * Uses credentials from cache. It will not ask for password
  42  * you should receive credentials for yuor name manually using
  43  * kinit or whatever you wish.
  44  *
  45  * in:
  46  *      oid -           string with OID/ Could be OID_KERBEROS5
  47  *                      or OID_KERBEROS5_OLD
  48  *      principal -     Service name.
  49  *                      Could be "cifs/FQDN" for KRB5 OID
  50  *                      or for MS_KRB5 OID style server principal
  51  *                      like "pdc$@YOUR.REALM.NAME"
  52  *
  53  * out:
  54  *      secblob -       pointer for spnego wrapped AP-REQ data to be stored
  55  *      sess_key-       pointer for SessionKey data to be stored
  56  *
  57  * ret: 0 - success, others - failure
  58 */
  59 int handle_krb5_mech(const char *oid, const char *principal,
  60                      DATA_BLOB * secblob, DATA_BLOB * sess_key)
  61 {
  62         int retval;
  63         DATA_BLOB tkt, tkt_wrapped;
  64
  65         /* get a kerberos ticket for the service and extract the session key */
  66         retval = cli_krb5_get_ticket(principal, 0,
  67                                      &tkt, sess_key, 0, NULL, NULL);
  68
  69         if (retval)
  70                 return retval;
  71
  72         /* wrap that up in a nice GSS-API wrapping */
  73         tkt_wrapped = spnego_gen_krb5_wrap(tkt, TOK_ID_KRB_AP_REQ);
  74
  75         /* and wrap that in a shiny SPNEGO wrapper */
  76         *secblob = gen_negTokenInit(oid, tkt_wrapped);
  77
  78         data_blob_free(&tkt_wrapped);
  79         data_blob_free(&tkt);
  80         return retval;
  81 }
  82
  83 #define DKD_HAVE_HOSTNAME       1
  84 #define DKD_HAVE_VERSION        2
  85 #define DKD_HAVE_SEC            4
  86 #define DKD_HAVE_IPV4           8
  87 #define DKD_HAVE_IPV6           16
  88 #define DKD_HAVE_UID            32
  89 #define DKD_MUSTHAVE_SET (DKD_HAVE_HOSTNAME|DKD_HAVE_VERSION|DKD_HAVE_SEC)
  90
  91 int decode_key_description(const char *desc, int *ver, secType_t * sec,
  92                            char **hostname, uid_t * uid)
  93 {
  94         int retval = 0;
  95         char *pos;
  96         const char *tkn = desc;
  97
  98         do {
  99                 pos = index(tkn, ';');
 100                 if (strncmp(tkn, "host=", 5) == 0) {
 101                         int len;
 102
 103                         if (pos == NULL) {
 104                                 len = strlen(tkn);
 105                         } else {
 106                                 len = pos - tkn;
 107                         }
 108                         len -= 4;
 109                         SAFE_FREE(*hostname);
 110                         *hostname = SMB_XMALLOC_ARRAY(char, len);
 111                         strlcpy(*hostname, tkn + 5, len);
 112                         retval |= DKD_HAVE_HOSTNAME;
 113                 } else if (strncmp(tkn, "ipv4=", 5) == 0) {
 114                         /* BB: do we need it if we have hostname already? */
 115                 } else if (strncmp(tkn, "ipv6=", 5) == 0) {
 116                         /* BB: do we need it if we have hostname already? */
 117                 } else if (strncmp(tkn, "sec=", 4) == 0) {
 118                         if (strncmp(tkn + 4, "krb5", 4) == 0) {
 119                                 retval |= DKD_HAVE_SEC;
 120                                 *sec = KRB5;
 121                         } else if (strncmp(tkn + 4, "mskrb5", 6) == 0) {
 122                                 retval |= DKD_HAVE_SEC;
 123                                 *sec = MS_KRB5;
 124                         }
 125                 } else if (strncmp(tkn, "uid=", 4) == 0) {
 126                         errno = 0;
 127                         *uid = strtol(tkn + 4, NULL, 16);
 128                         if (errno != 0) {
 129                                 syslog(LOG_WARNING, "Invalid uid format: %s",
 130                                        strerror(errno));
 131                                 return 1;
 132                         } else {
 133                                 retval |= DKD_HAVE_UID;
 134                         }
 135                 } else if (strncmp(tkn, "ver=", 4) == 0) {      /* if version */
 136                         errno = 0;
 137                         *ver = strtol(tkn + 4, NULL, 16);
 138                         if (errno != 0) {
 139                                 syslog(LOG_WARNING,
 140                                        "Invalid version format: %s",
 141                                        strerror(errno));
 142                                 return 1;
 143                         } else {
 144                                 retval |= DKD_HAVE_VERSION;
 145                         }
 146                 }
 147                 if (pos == NULL)
 148                         break;
 149                 tkn = pos + 1;
 150         } while (tkn);
 151         return retval;
 152 }
 153
 154 int cifs_resolver(const key_serial_t key, const char *key_descr)
 155 {
 156         int c;
 157         struct addrinfo *addr;
 158         char ip[INET6_ADDRSTRLEN];
 159         void *p;
 160         const char *keyend = key_descr;
 161         /* skip next 4 ';' delimiters to get to description */
 162         for (c = 1; c <= 4; c++) {
 163                 keyend = index(keyend+1, ';');
 164                 if (!keyend) {
 165                         syslog(LOG_WARNING, "invalid key description: %s",
 166                                         key_descr);
 167                         return 1;
 168                 }
 169         }
 170         keyend++;
 171
 172         /* resolve name to ip */
 173         c = getaddrinfo(keyend, NULL, NULL, &addr);
 174         if (c) {
 175                 syslog(LOG_WARNING, "unable to resolve hostname: %s [%s]",
 176                                 keyend, gai_strerror(c));
 177                 return 1;
 178         }
 179
 180         /* conver ip to string form */
 181         if (addr->ai_family == AF_INET) {
 182                 p = &(((struct sockaddr_in *)addr->ai_addr)->sin_addr);
 183         } else {
 184                 p = &(((struct sockaddr_in6 *)addr->ai_addr)->sin6_addr);
 185         }
 186         if (!inet_ntop(addr->ai_family, p, ip, sizeof(ip))) {
 187                 syslog(LOG_WARNING, "%s: inet_ntop: %s",
 188                                 __FUNCTION__, strerror(errno));
 189                 freeaddrinfo(addr);
 190                 return 1;
 191         }
 192
 193         /* setup key */
 194         c = keyctl_instantiate(key, ip, strlen(ip)+1, 0);
 195         if (c == -1) {
 196                 syslog(LOG_WARNING, "%s: keyctl_instantiate: %s",
 197                                 __FUNCTION__, strerror(errno));
 198                 freeaddrinfo(addr);
 199                 return 1;
 200         }
 201
 202         freeaddrinfo(addr);
 203         return 0;
 204 }
 205
 206 void
 207 usage(void)
 208 {
 209         syslog(LOG_WARNING, "Usage: %s [-c] [-v] key_serial", prog);
 210         fprintf(stderr, "Usage: %s [-c] [-v] key_serial\n", prog);
 211 }
 212
 213 int main(const int argc, char *const argv[])
 214 {
 215         struct cifs_spnego_msg *keydata = NULL;
 216         DATA_BLOB secblob = data_blob_null;
 217         DATA_BLOB sess_key = data_blob_null;
 218         secType_t sectype;
 219         key_serial_t key = 0;
 220         size_t datalen;
 221         long rc = 1;
 222         uid_t uid;
 223         int kernel_upcall_version;
 224         int c, use_cifs_service_prefix = 0;
 225         char *buf, *hostname = NULL;
 226         const char *oid;
 227
 228         openlog(prog, 0, LOG_DAEMON);
 229
 230         while ((c = getopt(argc, argv, "cv")) != -1) {
 231                 switch (c) {
 232                 case 'c':{
 233                         use_cifs_service_prefix = 1;
 234                         break;
 235                         }
 236                 case 'v':{
 237                         printf("version: %s\n", CIFSSPNEGO_VERSION);
 238                         goto out;
 239                         }
 240                 default:{
 241                         syslog(LOG_WARNING, "unknown option: %c", c);
 242                         goto out;
 243                         }
 244                 }
 245         }
 246
 247         /* is there a key? */
 248         if (argc <= optind) {
 249                 usage();
 250                 goto out;
 251         }
 252
 253         /* get key and keyring values */
 254         errno = 0;
 255         key = strtol(argv[optind], NULL, 10);
 256         if (errno != 0) {
 257                 key = 0;
 258                 syslog(LOG_WARNING, "Invalid key format: %s", strerror(errno));
 259                 goto out;
 260         }
 261
 262         rc = keyctl_describe_alloc(key, &buf);
 263         if (rc == -1) {
 264                 syslog(LOG_WARNING, "keyctl_describe_alloc failed: %s",
 265                        strerror(errno));
 266                 rc = 1;
 267                 goto out;
 268         }
 269
 270         if ((strncmp(buf, "cifs.resolver", sizeof("cifs.resolver")-1) == 0) ||
 271             (strncmp(buf, "dns_resolver", sizeof("dns_resolver")-1) == 0)) {
 272                 rc = cifs_resolver(key, buf);
 273                 goto out;
 274         }
 275
 276         rc = decode_key_description(buf, &kernel_upcall_version, &sectype,
 277                                     &hostname, &uid);
 278         if ((rc & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) {
 279                 syslog(LOG_WARNING,
 280                        "unable to get from description necessary params");
 281                 rc = 1;
 282                 SAFE_FREE(buf);
 283                 goto out;
 284         }
 285         SAFE_FREE(buf);
 286
 287         if (kernel_upcall_version > CIFS_SPNEGO_UPCALL_VERSION) {
 288                 syslog(LOG_WARNING,
 289                        "incompatible kernel upcall version: 0x%x",
 290                        kernel_upcall_version);
 291                 rc = 1;
 292                 goto out;
 293         }
 294
 295         if (rc & DKD_HAVE_UID) {
 296                 rc = setuid(uid);
 297                 if (rc == -1) {
 298                         syslog(LOG_WARNING, "setuid: %s", strerror(errno));
 299                         goto out;
 300                 }
 301         }
 302
 303         /* BB: someday upcall SPNEGO blob could be checked here to decide
 304          * what mech to use */
 305
 306         // do mech specific authorization
 307         switch (sectype) {
 308         case MS_KRB5:
 309         case KRB5:{
 310                         char *princ;
 311                         size_t len;
 312
 313                         /* for "cifs/" service name + terminating 0 */
 314                         len = strlen(hostname) + 5 + 1;
 315                         princ = SMB_XMALLOC_ARRAY(char, len);
 316                         if (!princ) {
 317                                 rc = 1;
 318                                 break;
 319                         }
 320                         if (use_cifs_service_prefix) {
 321                                 strlcpy(princ, "cifs/", len);
 322                         } else {
 323                                 strlcpy(princ, "host/", len);
 324                         }
 325                         strlcpy(princ + 5, hostname, len - 5);
 326
 327                         if (sectype == MS_KRB5)
 328                                 oid = OID_KERBEROS5_OLD;
 329                         else
 330                                 oid = OID_KERBEROS5;
 331
 332                         rc = handle_krb5_mech(oid, princ, &secblob, &sess_key);
 333                         SAFE_FREE(princ);
 334                         break;
 335                 }
 336         default:{
 337                         syslog(LOG_WARNING, "sectype: %d is not implemented",
 338                                sectype);
 339                         rc = 1;
 340                         break;
 341                 }
 342         }
 343
 344         if (rc) {
 345                 goto out;
 346         }
 347
 348         /* pack SecurityBLob and SessionKey into downcall packet */
 349         datalen =
 350             sizeof(struct cifs_spnego_msg) + secblob.length + sess_key.length;
 351         keydata = (struct cifs_spnego_msg*)SMB_XMALLOC_ARRAY(char, datalen);
 352         if (!keydata) {
 353                 rc = 1;
 354                 goto out;
 355         }
 356         keydata->version = kernel_upcall_version;
 357         keydata->flags = 0;
 358         keydata->sesskey_len = sess_key.length;
 359         keydata->secblob_len = secblob.length;
 360         memcpy(&(keydata->data), sess_key.data, sess_key.length);
 361         memcpy(&(keydata->data) + keydata->sesskey_len,
 362                secblob.data, secblob.length);
 363
 364         /* setup key */
 365         rc = keyctl_instantiate(key, keydata, datalen, 0);
 366         if (rc == -1) {
 367                 syslog(LOG_WARNING, "keyctl_instantiate: %s", strerror(errno));
 368                 goto out;
 369         }
 370
 371         /* BB: maybe we need use timeout for key: for example no more then
 372          * ticket lifietime? */
 373         /* keyctl_set_timeout( key, 60); */
 374 out:
 375         /*
 376          * on error, negatively instantiate the key ourselves so that we can
 377          * make sure the kernel doesn't hang it off of a searchable keyring
 378          * and interfere with the next attempt to instantiate the key.
 379          */
 380         if (rc != 0  && key == 0)
 381                 keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT);
 382         data_blob_free(&secblob);
 383         data_blob_free(&sess_key);
 384         SAFE_FREE(hostname);
 385         SAFE_FREE(keydata);
 386         return rc;
 387 }