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 = "1.1";
  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_KERBEROS5, 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                         }
 122                 } else if (strncmp(tkn, "uid=", 4) == 0) {
 123                         errno = 0;
 124                         *uid = strtol(tkn + 4, NULL, 16);
 125                         if (errno != 0) {
 126                                 syslog(LOG_WARNING, "Invalid uid format: %s",
 127                                        strerror(errno));
 128                                 return 1;
 129                         } else {
 130                                 retval |= DKD_HAVE_UID;
 131                         }
 132                 } else if (strncmp(tkn, "ver=", 4) == 0) {      /* if version */
 133                         errno = 0;
 134                         *ver = strtol(tkn + 4, NULL, 16);
 135                         if (errno != 0) {
 136                                 syslog(LOG_WARNING,
 137                                        "Invalid version format: %s",
 138                                        strerror(errno));
 139                                 return 1;
 140                         } else {
 141                                 retval |= DKD_HAVE_VERSION;
 142                         }
 143                 }
 144                 if (pos == NULL)
 145                         break;
 146                 tkn = pos + 1;
 147         } while (tkn);
 148         return retval;
 149 }
 150
 151 int cifs_resolver(const key_serial_t key, const char *key_descr)
 152 {
 153         int c;
 154         struct addrinfo *addr;
 155         char ip[INET6_ADDRSTRLEN];
 156         void *p;
 157         const char *keyend = key_descr;
 158         /* skip next 4 ';' delimiters to get to description */
 159         for (c = 1; c <= 4; c++) {
 160                 keyend = index(keyend+1, ';');
 161                 if (!keyend) {
 162                         syslog(LOG_WARNING, "invalid key description: %s",
 163                                         key_descr);
 164                         return 1;
 165                 }
 166         }
 167         keyend++;
 168
 169         /* resolve name to ip */
 170         c = getaddrinfo(keyend, NULL, NULL, &addr);
 171         if (c) {
 172                 syslog(LOG_WARNING, "unable to resolve hostname: %s [%s]",
 173                                 keyend, gai_strerror(c));
 174                 return 1;
 175         }
 176
 177         /* conver ip to string form */
 178         if (addr->ai_family == AF_INET) {
 179                 p = &(((struct sockaddr_in *)addr->ai_addr)->sin_addr);
 180         } else {
 181                 p = &(((struct sockaddr_in6 *)addr->ai_addr)->sin6_addr);
 182         }
 183         if (!inet_ntop(addr->ai_family, p, ip, sizeof(ip))) {
 184                 syslog(LOG_WARNING, "%s: inet_ntop: %s",
 185                                 __FUNCTION__, strerror(errno));
 186                 freeaddrinfo(addr);
 187                 return 1;
 188         }
 189
 190         /* setup key */
 191         c = keyctl_instantiate(key, ip, strlen(ip)+1, 0);
 192         if (c == -1) {
 193                 syslog(LOG_WARNING, "%s: keyctl_instantiate: %s",
 194                                 __FUNCTION__, strerror(errno));
 195                 freeaddrinfo(addr);
 196                 return 1;
 197         }
 198
 199         freeaddrinfo(addr);
 200         return 0;
 201 }
 202
 203 void
 204 usage(void)
 205 {
 206         syslog(LOG_WARNING, "Usage: %s [-c] [-v] key_serial", prog);
 207         fprintf(stderr, "Usage: %s [-c] [-v] key_serial\n", prog);
 208 }
 209
 210 int main(const int argc, char *const argv[])
 211 {
 212         struct cifs_spnego_msg *keydata = NULL;
 213         DATA_BLOB secblob = data_blob_null;
 214         DATA_BLOB sess_key = data_blob_null;
 215         secType_t sectype;
 216         key_serial_t key = 0;
 217         size_t datalen;
 218         long rc = 1;
 219         uid_t uid;
 220         int kernel_upcall_version;
 221         int c, use_cifs_service_prefix = 0;
 222         char *buf, *hostname = NULL;
 223
 224         openlog(prog, 0, LOG_DAEMON);
 225
 226         while ((c = getopt(argc, argv, "cv")) != -1) {
 227                 switch (c) {
 228                 case 'c':{
 229                         use_cifs_service_prefix = 1;
 230                         break;
 231                         }
 232                 case 'v':{
 233                         printf("version: %s\n", CIFSSPNEGO_VERSION);
 234                         goto out;
 235                         }
 236                 default:{
 237                         syslog(LOG_WARNING, "unknown option: %c", c);
 238                         goto out;
 239                         }
 240                 }
 241         }
 242
 243         /* is there a key? */
 244         if (argc <= optind) {
 245                 usage();
 246                 goto out;
 247         }
 248
 249         /* get key and keyring values */
 250         errno = 0;
 251         key = strtol(argv[optind], NULL, 10);
 252         if (errno != 0) {
 253                 key = 0;
 254                 syslog(LOG_WARNING, "Invalid key format: %s", strerror(errno));
 255                 goto out;
 256         }
 257
 258         rc = keyctl_describe_alloc(key, &buf);
 259         if (rc == -1) {
 260                 syslog(LOG_WARNING, "keyctl_describe_alloc failed: %s",
 261                        strerror(errno));
 262                 rc = 1;
 263                 goto out;
 264         }
 265
 266         if ((strncmp(buf, "cifs.resolver", sizeof("cifs.resolver")-1) == 0) ||
 267             (strncmp(buf, "dns_resolver", sizeof("dns_resolver")-1) == 0)) {
 268                 rc = cifs_resolver(key, buf);
 269                 goto out;
 270         }
 271
 272         rc = decode_key_description(buf, &kernel_upcall_version, &sectype,
 273                                     &hostname, &uid);
 274         if ((rc & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) {
 275                 syslog(LOG_WARNING,
 276                        "unable to get from description necessary params");
 277                 rc = 1;
 278                 SAFE_FREE(buf);
 279                 goto out;
 280         }
 281         SAFE_FREE(buf);
 282
 283         if (kernel_upcall_version != CIFS_SPNEGO_UPCALL_VERSION) {
 284                 syslog(LOG_WARNING,
 285                        "incompatible kernel upcall version: 0x%x",
 286                        kernel_upcall_version);
 287                 rc = 1;
 288                 goto out;
 289         }
 290
 291         if (rc & DKD_HAVE_UID) {
 292                 rc = setuid(uid);
 293                 if (rc == -1) {
 294                         syslog(LOG_WARNING, "setuid: %s", strerror(errno));
 295                         goto out;
 296                 }
 297         }
 298
 299         /* BB: someday upcall SPNEGO blob could be checked here to decide
 300          * what mech to use */
 301
 302         // do mech specific authorization
 303         switch (sectype) {
 304         case KRB5:{
 305                         char *princ;
 306                         size_t len;
 307
 308                         /* for "cifs/" service name + terminating 0 */
 309                         len = strlen(hostname) + 5 + 1;
 310                         princ = SMB_XMALLOC_ARRAY(char, len);
 311                         if (!princ) {
 312                                 rc = 1;
 313                                 break;
 314                         }
 315                         if (use_cifs_service_prefix) {
 316                                 strlcpy(princ, "cifs/", len);
 317                         } else {
 318                                 strlcpy(princ, "host/", len);
 319                         }
 320                         strlcpy(princ + 5, hostname, len - 5);
 321
 322                         rc = handle_krb5_mech(OID_KERBEROS5, princ,
 323                                               &secblob, &sess_key);
 324                         SAFE_FREE(princ);
 325                         break;
 326                 }
 327         default:{
 328                         syslog(LOG_WARNING, "sectype: %d is not implemented",
 329                                sectype);
 330                         rc = 1;
 331                         break;
 332                 }
 333         }
 334
 335         if (rc) {
 336                 goto out;
 337         }
 338
 339         /* pack SecurityBLob and SessionKey into downcall packet */
 340         datalen =
 341             sizeof(struct cifs_spnego_msg) + secblob.length + sess_key.length;
 342         keydata = (struct cifs_spnego_msg*)SMB_XMALLOC_ARRAY(char, datalen);
 343         if (!keydata) {
 344                 rc = 1;
 345                 goto out;
 346         }
 347         keydata->version = CIFS_SPNEGO_UPCALL_VERSION;
 348         keydata->flags = 0;
 349         keydata->sesskey_len = sess_key.length;
 350         keydata->secblob_len = secblob.length;
 351         memcpy(&(keydata->data), sess_key.data, sess_key.length);
 352         memcpy(&(keydata->data) + keydata->sesskey_len,
 353                secblob.data, secblob.length);
 354
 355         /* setup key */
 356         rc = keyctl_instantiate(key, keydata, datalen, 0);
 357         if (rc == -1) {
 358                 syslog(LOG_WARNING, "keyctl_instantiate: %s", strerror(errno));
 359                 goto out;
 360         }
 361
 362         /* BB: maybe we need use timeout for key: for example no more then
 363          * ticket lifietime? */
 364         /* keyctl_set_timeout( key, 60); */
 365 out:
 366         /*
 367          * on error, negatively instantiate the key ourselves so that we can
 368          * make sure the kernel doesn't hang it off of a searchable keyring
 369          * and interfere with the next attempt to instantiate the key.
 370          */
 371         if (rc != 0  && key == 0)
 372                 keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT);
 373         data_blob_free(&secblob);
 374         data_blob_free(&sess_key);
 375         SAFE_FREE(hostname);
 376         SAFE_FREE(keydata);
 377         return rc;
 378 }