source3/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, *oid, *hostname = NULL;
 226
 227         openlog(prog, 0, LOG_DAEMON);
 228
 229         while ((c = getopt(argc, argv, "cv")) != -1) {
 230                 switch (c) {
 231                 case 'c':{
 232                         use_cifs_service_prefix = 1;
 233                         break;
 234                         }
 235                 case 'v':{
 236                         printf("version: %s\n", CIFSSPNEGO_VERSION);
 237                         goto out;
 238                         }
 239                 default:{
 240                         syslog(LOG_WARNING, "unknown option: %c", c);
 241                         goto out;
 242                         }
 243                 }
 244         }
 245
 246         /* is there a key? */
 247         if (argc <= optind) {
 248                 usage();
 249                 goto out;
 250         }
 251
 252         /* get key and keyring values */
 253         errno = 0;
 254         key = strtol(argv[optind], NULL, 10);
 255         if (errno != 0) {
 256                 key = 0;
 257                 syslog(LOG_WARNING, "Invalid key format: %s", strerror(errno));
 258                 goto out;
 259         }
 260
 261         rc = keyctl_describe_alloc(key, &buf);
 262         if (rc == -1) {
 263                 syslog(LOG_WARNING, "keyctl_describe_alloc failed: %s",
 264                        strerror(errno));
 265                 rc = 1;
 266                 goto out;
 267         }
 268
 269         if ((strncmp(buf, "cifs.resolver", sizeof("cifs.resolver")-1) == 0) ||
 270             (strncmp(buf, "dns_resolver", sizeof("dns_resolver")-1) == 0)) {
 271                 rc = cifs_resolver(key, buf);
 272                 goto out;
 273         }
 274
 275         rc = decode_key_description(buf, &kernel_upcall_version, &sectype,
 276                                     &hostname, &uid);
 277         if ((rc & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) {
 278                 syslog(LOG_WARNING,
 279                        "unable to get from description necessary params");
 280                 rc = 1;
 281                 SAFE_FREE(buf);
 282                 goto out;
 283         }
 284         SAFE_FREE(buf);
 285
 286         if (kernel_upcall_version != CIFS_SPNEGO_UPCALL_VERSION) {
 287                 syslog(LOG_WARNING,
 288                        "incompatible kernel upcall version: 0x%x",
 289                        kernel_upcall_version);
 290                 rc = 1;
 291                 goto out;
 292         }
 293
 294         if (rc & DKD_HAVE_UID) {
 295                 rc = setuid(uid);
 296                 if (rc == -1) {
 297                         syslog(LOG_WARNING, "setuid: %s", strerror(errno));
 298                         goto out;
 299                 }
 300         }
 301
 302         /* BB: someday upcall SPNEGO blob could be checked here to decide
 303          * what mech to use */
 304
 305         // do mech specific authorization
 306         switch (sectype) {
 307         case MS_KRB5:
 308         case KRB5:{
 309                         char *princ;
 310                         size_t len;
 311
 312                         /* for "cifs/" service name + terminating 0 */
 313                         len = strlen(hostname) + 5 + 1;
 314                         princ = SMB_XMALLOC_ARRAY(char, len);
 315                         if (!princ) {
 316                                 rc = 1;
 317                                 break;
 318                         }
 319                         if (use_cifs_service_prefix) {
 320                                 strlcpy(princ, "cifs/", len);
 321                         } else {
 322                                 strlcpy(princ, "host/", len);
 323                         }
 324                         strlcpy(princ + 5, hostname, len - 5);
 325
 326                         if (sectype == MS_KRB5)
 327                                 oid = OID_KERBEROS5_OLD;
 328                         else
 329                                 oid = OID_KERBEROS5;
 330
 331                         rc = handle_krb5_mech(oid, princ, &secblob, &sess_key);
 332                         SAFE_FREE(princ);
 333                         break;
 334                 }
 335         default:{
 336                         syslog(LOG_WARNING, "sectype: %d is not implemented",
 337                                sectype);
 338                         rc = 1;
 339                         break;
 340                 }
 341         }
 342
 343         if (rc) {
 344                 goto out;
 345         }
 346
 347         /* pack SecurityBLob and SessionKey into downcall packet */
 348         datalen =
 349             sizeof(struct cifs_spnego_msg) + secblob.length + sess_key.length;
 350         keydata = (struct cifs_spnego_msg*)SMB_XMALLOC_ARRAY(char, datalen);
 351         if (!keydata) {
 352                 rc = 1;
 353                 goto out;
 354         }
 355         keydata->version = CIFS_SPNEGO_UPCALL_VERSION;
 356         keydata->flags = 0;
 357         keydata->sesskey_len = sess_key.length;
 358         keydata->secblob_len = secblob.length;
 359         memcpy(&(keydata->data), sess_key.data, sess_key.length);
 360         memcpy(&(keydata->data) + keydata->sesskey_len,
 361                secblob.data, secblob.length);
 362
 363         /* setup key */
 364         rc = keyctl_instantiate(key, keydata, datalen, 0);
 365         if (rc == -1) {
 366                 syslog(LOG_WARNING, "keyctl_instantiate: %s", strerror(errno));
 367                 goto out;
 368         }
 369
 370         /* BB: maybe we need use timeout for key: for example no more then
 371          * ticket lifietime? */
 372         /* keyctl_set_timeout( key, 60); */
 373 out:
 374         /*
 375          * on error, negatively instantiate the key ourselves so that we can
 376          * make sure the kernel doesn't hang it off of a searchable keyring
 377          * and interfere with the next attempt to instantiate the key.
 378          */
 379         if (rc != 0  && key == 0)
 380                 keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT);
 381         data_blob_free(&secblob);
 382         data_blob_free(&sess_key);
 383         SAFE_FREE(hostname);
 384         SAFE_FREE(keydata);
 385         return rc;
 386 }