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         NONE = 0,
  36         KRB5,
  37         MS_KRB5
  38 } secType_t;
  39
  40 /*
  41  * Prepares AP-REQ data for mechToken and gets session key
  42  * Uses credentials from cache. It will not ask for password
  43  * you should receive credentials for yuor name manually using
  44  * kinit or whatever you wish.
  45  *
  46  * in:
  47  *      oid -           string with OID/ Could be OID_KERBEROS5
  48  *                      or OID_KERBEROS5_OLD
  49  *      principal -     Service name.
  50  *                      Could be "cifs/FQDN" for KRB5 OID
  51  *                      or for MS_KRB5 OID style server principal
  52  *                      like "pdc$@YOUR.REALM.NAME"
  53  *
  54  * out:
  55  *      secblob -       pointer for spnego wrapped AP-REQ data to be stored
  56  *      sess_key-       pointer for SessionKey data to be stored
  57  *
  58  * ret: 0 - success, others - failure
  59 */
  60 static int
  61 handle_krb5_mech(const char *oid, const char *principal,
  62                      DATA_BLOB * secblob, DATA_BLOB * sess_key)
  63 {
  64         int retval;
  65         DATA_BLOB tkt, tkt_wrapped;
  66
  67         /* get a kerberos ticket for the service and extract the session key */
  68         retval = cli_krb5_get_ticket(principal, 0,
  69                                      &tkt, sess_key, 0, NULL, NULL);
  70
  71         if (retval)
  72                 return retval;
  73
  74         /* wrap that up in a nice GSS-API wrapping */
  75         tkt_wrapped = spnego_gen_krb5_wrap(tkt, TOK_ID_KRB_AP_REQ);
  76
  77         /* and wrap that in a shiny SPNEGO wrapper */
  78         *secblob = gen_negTokenInit(oid, tkt_wrapped);
  79
  80         data_blob_free(&tkt_wrapped);
  81         data_blob_free(&tkt);
  82         return retval;
  83 }
  84
  85 #define DKD_HAVE_HOSTNAME       1
  86 #define DKD_HAVE_VERSION        2
  87 #define DKD_HAVE_SEC            4
  88 #define DKD_HAVE_IPV4           8
  89 #define DKD_HAVE_IPV6           16
  90 #define DKD_HAVE_UID            32
  91 #define DKD_MUSTHAVE_SET (DKD_HAVE_HOSTNAME|DKD_HAVE_VERSION|DKD_HAVE_SEC)
  92
  93 static int
  94 decode_key_description(const char *desc, int *ver, secType_t * sec,
  95                            char **hostname, uid_t * uid)
  96 {
  97         int retval = 0;
  98         char *pos;
  99         const char *tkn = desc;
 100
 101         do {
 102                 pos = index(tkn, ';');
 103                 if (strncmp(tkn, "host=", 5) == 0) {
 104                         int len;
 105
 106                         if (pos == NULL) {
 107                                 len = strlen(tkn);
 108                         } else {
 109                                 len = pos - tkn;
 110                         }
 111                         len -= 4;
 112                         SAFE_FREE(*hostname);
 113                         *hostname = SMB_XMALLOC_ARRAY(char, len);
 114                         strlcpy(*hostname, tkn + 5, len);
 115                         retval |= DKD_HAVE_HOSTNAME;
 116                 } else if (strncmp(tkn, "ipv4=", 5) == 0) {
 117                         /* BB: do we need it if we have hostname already? */
 118                 } else if (strncmp(tkn, "ipv6=", 5) == 0) {
 119                         /* BB: do we need it if we have hostname already? */
 120                 } else if (strncmp(tkn, "sec=", 4) == 0) {
 121                         if (strncmp(tkn + 4, "krb5", 4) == 0) {
 122                                 retval |= DKD_HAVE_SEC;
 123                                 *sec = KRB5;
 124                         } else if (strncmp(tkn + 4, "mskrb5", 6) == 0) {
 125                                 retval |= DKD_HAVE_SEC;
 126                                 *sec = MS_KRB5;
 127                         }
 128                 } else if (strncmp(tkn, "uid=", 4) == 0) {
 129                         errno = 0;
 130                         *uid = strtol(tkn + 4, NULL, 16);
 131                         if (errno != 0) {
 132                                 syslog(LOG_WARNING, "Invalid uid format: %s",
 133                                        strerror(errno));
 134                                 return 1;
 135                         } else {
 136                                 retval |= DKD_HAVE_UID;
 137                         }
 138                 } else if (strncmp(tkn, "ver=", 4) == 0) {      /* if version */
 139                         errno = 0;
 140                         *ver = strtol(tkn + 4, NULL, 16);
 141                         if (errno != 0) {
 142                                 syslog(LOG_WARNING,
 143                                        "Invalid version format: %s",
 144                                        strerror(errno));
 145                                 return 1;
 146                         } else {
 147                                 retval |= DKD_HAVE_VERSION;
 148                         }
 149                 }
 150                 if (pos == NULL)
 151                         break;
 152                 tkn = pos + 1;
 153         } while (tkn);
 154         return retval;
 155 }
 156
 157 static int
 158 cifs_resolver(const key_serial_t key, const char *key_descr)
 159 {
 160         int c;
 161         struct addrinfo *addr;
 162         char ip[INET6_ADDRSTRLEN];
 163         void *p;
 164         const char *keyend = key_descr;
 165         /* skip next 4 ';' delimiters to get to description */
 166         for (c = 1; c <= 4; c++) {
 167                 keyend = index(keyend+1, ';');
 168                 if (!keyend) {
 169                         syslog(LOG_WARNING, "invalid key description: %s",
 170                                         key_descr);
 171                         return 1;
 172                 }
 173         }
 174         keyend++;
 175
 176         /* resolve name to ip */
 177         c = getaddrinfo(keyend, NULL, NULL, &addr);
 178         if (c) {
 179                 syslog(LOG_WARNING, "unable to resolve hostname: %s [%s]",
 180                                 keyend, gai_strerror(c));
 181                 return 1;
 182         }
 183
 184         /* conver ip to string form */
 185         if (addr->ai_family == AF_INET) {
 186                 p = &(((struct sockaddr_in *)addr->ai_addr)->sin_addr);
 187         } else {
 188                 p = &(((struct sockaddr_in6 *)addr->ai_addr)->sin6_addr);
 189         }
 190         if (!inet_ntop(addr->ai_family, p, ip, sizeof(ip))) {
 191                 syslog(LOG_WARNING, "%s: inet_ntop: %s",
 192                                 __FUNCTION__, strerror(errno));
 193                 freeaddrinfo(addr);
 194                 return 1;
 195         }
 196
 197         /* setup key */
 198         c = keyctl_instantiate(key, ip, strlen(ip)+1, 0);
 199         if (c == -1) {
 200                 syslog(LOG_WARNING, "%s: keyctl_instantiate: %s",
 201                                 __FUNCTION__, strerror(errno));
 202                 freeaddrinfo(addr);
 203                 return 1;
 204         }
 205
 206         freeaddrinfo(addr);
 207         return 0;
 208 }
 209
 210 static void
 211 usage(void)
 212 {
 213         syslog(LOG_WARNING, "Usage: %s [-c] [-v] key_serial", prog);
 214         fprintf(stderr, "Usage: %s [-c] [-v] key_serial\n", prog);
 215 }
 216
 217 int main(const int argc, char *const argv[])
 218 {
 219         struct cifs_spnego_msg *keydata = NULL;
 220         DATA_BLOB secblob = data_blob_null;
 221         DATA_BLOB sess_key = data_blob_null;
 222         secType_t sectype = NONE;
 223         key_serial_t key = 0;
 224         size_t datalen;
 225         long rc = 1;
 226         uid_t uid = 0;
 227         int kernel_upcall_version = 0;
 228         int c, use_cifs_service_prefix = 0;
 229         char *buf, *hostname = NULL;
 230         const char *oid;
 231
 232         openlog(prog, 0, LOG_DAEMON);
 233
 234         while ((c = getopt(argc, argv, "cv")) != -1) {
 235                 switch (c) {
 236                 case 'c':{
 237                         use_cifs_service_prefix = 1;
 238                         break;
 239                         }
 240                 case 'v':{
 241                         printf("version: %s\n", CIFSSPNEGO_VERSION);
 242                         goto out;
 243                         }
 244                 default:{
 245                         syslog(LOG_WARNING, "unknown option: %c", c);
 246                         goto out;
 247                         }
 248                 }
 249         }
 250
 251         /* is there a key? */
 252         if (argc <= optind) {
 253                 usage();
 254                 goto out;
 255         }
 256
 257         /* get key and keyring values */
 258         errno = 0;
 259         key = strtol(argv[optind], NULL, 10);
 260         if (errno != 0) {
 261                 key = 0;
 262                 syslog(LOG_WARNING, "Invalid key format: %s", strerror(errno));
 263                 goto out;
 264         }
 265
 266         rc = keyctl_describe_alloc(key, &buf);
 267         if (rc == -1) {
 268                 syslog(LOG_WARNING, "keyctl_describe_alloc failed: %s",
 269                        strerror(errno));
 270                 rc = 1;
 271                 goto out;
 272         }
 273
 274         if ((strncmp(buf, "cifs.resolver", sizeof("cifs.resolver")-1) == 0) ||
 275             (strncmp(buf, "dns_resolver", sizeof("dns_resolver")-1) == 0)) {
 276                 rc = cifs_resolver(key, buf);
 277                 goto out;
 278         }
 279
 280         rc = decode_key_description(buf, &kernel_upcall_version, &sectype,
 281                                     &hostname, &uid);
 282         if ((rc & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) {
 283                 syslog(LOG_WARNING,
 284                        "unable to get from description necessary params");
 285                 rc = 1;
 286                 SAFE_FREE(buf);
 287                 goto out;
 288         }
 289         SAFE_FREE(buf);
 290
 291         if (kernel_upcall_version > CIFS_SPNEGO_UPCALL_VERSION) {
 292                 syslog(LOG_WARNING,
 293                        "incompatible kernel upcall version: 0x%x",
 294                        kernel_upcall_version);
 295                 rc = 1;
 296                 goto out;
 297         }
 298
 299         if (rc & DKD_HAVE_UID) {
 300                 rc = setuid(uid);
 301                 if (rc == -1) {
 302                         syslog(LOG_WARNING, "setuid: %s", strerror(errno));
 303                         goto out;
 304                 }
 305         }
 306
 307         /* BB: someday upcall SPNEGO blob could be checked here to decide
 308          * what mech to use */
 309
 310         // do mech specific authorization
 311         switch (sectype) {
 312         case MS_KRB5:
 313         case KRB5:{
 314                         char *princ;
 315                         size_t len;
 316
 317                         /* for "cifs/" service name + terminating 0 */
 318                         len = strlen(hostname) + 5 + 1;
 319                         princ = SMB_XMALLOC_ARRAY(char, len);
 320                         if (!princ) {
 321                                 rc = 1;
 322                                 break;
 323                         }
 324                         if (use_cifs_service_prefix) {
 325                                 strlcpy(princ, "cifs/", len);
 326                         } else {
 327                                 strlcpy(princ, "host/", len);
 328                         }
 329                         strlcpy(princ + 5, hostname, len - 5);
 330
 331                         if (sectype == MS_KRB5)
 332                                 oid = OID_KERBEROS5_OLD;
 333                         else
 334                                 oid = OID_KERBEROS5;
 335
 336                         rc = handle_krb5_mech(oid, princ, &secblob, &sess_key);
 337                         SAFE_FREE(princ);
 338                         break;
 339                 }
 340         default:{
 341                         syslog(LOG_WARNING, "sectype: %d is not implemented",
 342                                sectype);
 343                         rc = 1;
 344                         break;
 345                 }
 346         }
 347
 348         if (rc) {
 349                 goto out;
 350         }
 351
 352         /* pack SecurityBLob and SessionKey into downcall packet */
 353         datalen =
 354             sizeof(struct cifs_spnego_msg) + secblob.length + sess_key.length;
 355         keydata = (struct cifs_spnego_msg*)SMB_XMALLOC_ARRAY(char, datalen);
 356         if (!keydata) {
 357                 rc = 1;
 358                 goto out;
 359         }
 360         keydata->version = kernel_upcall_version;
 361         keydata->flags = 0;
 362         keydata->sesskey_len = sess_key.length;
 363         keydata->secblob_len = secblob.length;
 364         memcpy(&(keydata->data), sess_key.data, sess_key.length);
 365         memcpy(&(keydata->data) + keydata->sesskey_len,
 366                secblob.data, secblob.length);
 367
 368         /* setup key */
 369         rc = keyctl_instantiate(key, keydata, datalen, 0);
 370         if (rc == -1) {
 371                 syslog(LOG_WARNING, "keyctl_instantiate: %s", strerror(errno));
 372                 goto out;
 373         }
 374
 375         /* BB: maybe we need use timeout for key: for example no more then
 376          * ticket lifietime? */
 377         /* keyctl_set_timeout( key, 60); */
 378 out:
 379         /*
 380          * on error, negatively instantiate the key ourselves so that we can
 381          * make sure the kernel doesn't hang it off of a searchable keyring
 382          * and interfere with the next attempt to instantiate the key.
 383          */
 384         if (rc != 0  && key == 0)
 385                 keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT);
 386         data_blob_free(&secblob);
 387         data_blob_free(&sess_key);
 388         SAFE_FREE(hostname);
 389         SAFE_FREE(keydata);
 390         return rc;
 391 }