client/cifs.upcall.c

   1 /*
   2 * CIFS user-space helper.
   3 * Copyright (C) Igor Mammedov (niallain@gmail.com) 2007
   4 * Copyright (C) Jeff Layton (jlayton@redhat.com) 2009
   5 *
   6 * Used by /sbin/request-key for handling
   7 * cifs upcall for kerberos authorization of access to share and
   8 * cifs upcall for DFS srver name resolving (IPv4/IPv6 aware).
   9 * You should have keyutils installed and add something like the
  10 * following lines to /etc/request-key.conf file:
  11
  12 create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
  13 create dns_resolver * * /usr/local/sbin/cifs.upcall %k
  14
  15 * This program is free software; you can redistribute it and/or modify
  16 * it under the terms of the GNU General Public License as published by
  17 * the Free Software Foundation; either version 2 of the License, or
  18 * (at your option) any later version.
  19 * This program is distributed in the hope that it will be useful,
  20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  22 * GNU General Public License for more details.
  23 * You should have received a copy of the GNU General Public License
  24 * along with this program; if not, write to the Free Software
  25 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  26 */
  27
  28 #include "includes.h"
  29 #include <keyutils.h>
  30
  31 #include "cifs_spnego.h"
  32
  33 const char *CIFSSPNEGO_VERSION = "1.2";
  34 static const char *prog = "cifs.upcall";
  35 typedef enum _secType {
  36         NONE = 0,
  37         KRB5,
  38         MS_KRB5
  39 } secType_t;
  40
  41 /*
  42  * given a process ID, get the value of the KRB5CCNAME environment variable
  43  * in the context of that process. On error, just return NULL.
  44  */
  45 static char *
  46 get_krb5_ccname(pid_t pid)
  47 {
  48         int fd;
  49         ssize_t len, left;
  50
  51         /*
  52          * FIXME: sysconf for ARG_MAX instead? Kernel seems to be limited to a
  53          * page however, so it may not matter.
  54          */
  55         char buf[4096];
  56         char *p, *value = NULL;
  57
  58         buf[4095] = '\0';
  59         snprintf(buf, 4095, "/proc/%d/environ", pid);
  60         fd = open(buf, O_RDONLY);
  61         if (fd < 0) {
  62                 syslog(LOG_DEBUG, "%s: unable to open %s: %d", __func__, buf,
  63                         errno);
  64                 return NULL;
  65         }
  66
  67         /* FIXME: don't assume that we get it all in the first read? */
  68         len = read(fd, buf, 4096);
  69         close(fd);
  70         if (len < 0) {
  71                 syslog(LOG_DEBUG, "%s: unable to read from /proc/%d/environ: "
  72                                   "%d", __func__, pid, errno);
  73                 return NULL;
  74         }
  75
  76         left = len;
  77         p = buf;
  78
  79         /* can't have valid KRB5CCNAME if there are < 13 bytes left */
  80         while (left > 12) {
  81                 if (strncmp("KRB5CCNAME=", p, 11)) {
  82                         p += strnlen(p, left);
  83                         ++p;
  84                         left = buf + len - p;
  85                         continue;
  86                 }
  87                 p += 11;
  88                 left -= 11;
  89                 value = SMB_STRNDUP(p, left);
  90                 break;
  91         }
  92         syslog(LOG_DEBUG, "%s: KRB5CCNAME=%s", __func__,
  93                                 value ? value : "(null)");
  94         return value;
  95 }
  96
  97 /*
  98  * Prepares AP-REQ data for mechToken and gets session key
  99  * Uses credentials from cache. It will not ask for password
 100  * you should receive credentials for yuor name manually using
 101  * kinit or whatever you wish.
 102  *
 103  * in:
 104  *      oid -           string with OID/ Could be OID_KERBEROS5
 105  *                      or OID_KERBEROS5_OLD
 106  *      principal -     Service name.
 107  *                      Could be "cifs/FQDN" for KRB5 OID
 108  *                      or for MS_KRB5 OID style server principal
 109  *                      like "pdc$@YOUR.REALM.NAME"
 110  *
 111  * out:
 112  *      secblob -       pointer for spnego wrapped AP-REQ data to be stored
 113  *      sess_key-       pointer for SessionKey data to be stored
 114  *
 115  * ret: 0 - success, others - failure
 116  */
 117 static int
 118 handle_krb5_mech(const char *oid, const char *principal, DATA_BLOB *secblob,
 119                  DATA_BLOB *sess_key, const char *ccname)
 120 {
 121         int retval;
 122         DATA_BLOB tkt, tkt_wrapped;
 123
 124         syslog(LOG_DEBUG, "%s: getting service ticket for %s", __func__,
 125                           principal);
 126
 127         /* get a kerberos ticket for the service and extract the session key */
 128         retval = cli_krb5_get_ticket(principal, 0, &tkt, sess_key, 0, ccname,
 129                                      NULL);
 130
 131         if (retval) {
 132                 syslog(LOG_DEBUG, "%s: failed to obtain service ticket (%d)",
 133                                   __func__, retval);
 134                 return retval;
 135         }
 136
 137         syslog(LOG_DEBUG, "%s: obtained service ticket", __func__);
 138
 139         /* wrap that up in a nice GSS-API wrapping */
 140         tkt_wrapped = spnego_gen_krb5_wrap(tkt, TOK_ID_KRB_AP_REQ);
 141
 142         /* and wrap that in a shiny SPNEGO wrapper */
 143         *secblob = gen_negTokenInit(oid, tkt_wrapped);
 144
 145         data_blob_free(&tkt_wrapped);
 146         data_blob_free(&tkt);
 147         return retval;
 148 }
 149
 150 #define DKD_HAVE_HOSTNAME       0x1
 151 #define DKD_HAVE_VERSION        0x2
 152 #define DKD_HAVE_SEC            0x4
 153 #define DKD_HAVE_IPV4           0x8
 154 #define DKD_HAVE_IPV6           0x10
 155 #define DKD_HAVE_UID            0x20
 156 #define DKD_HAVE_PID            0x40
 157 #define DKD_MUSTHAVE_SET (DKD_HAVE_HOSTNAME|DKD_HAVE_VERSION|DKD_HAVE_SEC)
 158
 159 static int
 160 decode_key_description(const char *desc, int *ver, secType_t *sec,
 161                            char **hostname, uid_t *uid, pid_t *pid)
 162 {
 163         int retval = 0;
 164         char *pos;
 165         const char *tkn = desc;
 166
 167         do {
 168                 pos = index(tkn, ';');
 169                 if (strncmp(tkn, "host=", 5) == 0) {
 170                         int len;
 171
 172                         if (pos == NULL)
 173                                 len = strlen(tkn);
 174                         else
 175                                 len = pos - tkn;
 176
 177                         len -= 4;
 178                         SAFE_FREE(*hostname);
 179                         *hostname = SMB_XMALLOC_ARRAY(char, len);
 180                         strlcpy(*hostname, tkn + 5, len);
 181                         retval |= DKD_HAVE_HOSTNAME;
 182                 } else if (strncmp(tkn, "ipv4=", 5) == 0) {
 183                         /* BB: do we need it if we have hostname already? */
 184                 } else if (strncmp(tkn, "ipv6=", 5) == 0) {
 185                         /* BB: do we need it if we have hostname already? */
 186                 } else if (strncmp(tkn, "pid=", 4) == 0) {
 187                         errno = 0;
 188                         *pid = strtol(tkn + 4, NULL, 0);
 189                         if (errno != 0) {
 190                                 syslog(LOG_ERR, "Invalid pid format: %s",
 191                                        strerror(errno));
 192                                 return 1;
 193                         } else {
 194                                 retval |= DKD_HAVE_PID;
 195                         }
 196                 } else if (strncmp(tkn, "sec=", 4) == 0) {
 197                         if (strncmp(tkn + 4, "krb5", 4) == 0) {
 198                                 retval |= DKD_HAVE_SEC;
 199                                 *sec = KRB5;
 200                         } else if (strncmp(tkn + 4, "mskrb5", 6) == 0) {
 201                                 retval |= DKD_HAVE_SEC;
 202                                 *sec = MS_KRB5;
 203                         }
 204                 } else if (strncmp(tkn, "uid=", 4) == 0) {
 205                         errno = 0;
 206                         *uid = strtol(tkn + 4, NULL, 16);
 207                         if (errno != 0) {
 208                                 syslog(LOG_ERR, "Invalid uid format: %s",
 209                                        strerror(errno));
 210                                 return 1;
 211                         } else {
 212                                 retval |= DKD_HAVE_UID;
 213                         }
 214                 } else if (strncmp(tkn, "ver=", 4) == 0) {      /* if version */
 215                         errno = 0;
 216                         *ver = strtol(tkn + 4, NULL, 16);
 217                         if (errno != 0) {
 218                                 syslog(LOG_ERR, "Invalid version format: %s",
 219                                        strerror(errno));
 220                                 return 1;
 221                         } else {
 222                                 retval |= DKD_HAVE_VERSION;
 223                         }
 224                 }
 225                 if (pos == NULL)
 226                         break;
 227                 tkn = pos + 1;
 228         } while (tkn);
 229         return retval;
 230 }
 231
 232 static int
 233 cifs_resolver(const key_serial_t key, const char *key_descr)
 234 {
 235         int c;
 236         struct addrinfo *addr;
 237         char ip[INET6_ADDRSTRLEN];
 238         void *p;
 239         const char *keyend = key_descr;
 240         /* skip next 4 ';' delimiters to get to description */
 241         for (c = 1; c <= 4; c++) {
 242                 keyend = index(keyend+1, ';');
 243                 if (!keyend) {
 244                         syslog(LOG_ERR, "invalid key description: %s",
 245                                         key_descr);
 246                         return 1;
 247                 }
 248         }
 249         keyend++;
 250
 251         /* resolve name to ip */
 252         c = getaddrinfo(keyend, NULL, NULL, &addr);
 253         if (c) {
 254                 syslog(LOG_ERR, "unable to resolve hostname: %s [%s]",
 255                                 keyend, gai_strerror(c));
 256                 return 1;
 257         }
 258
 259         /* conver ip to string form */
 260         if (addr->ai_family == AF_INET)
 261                 p = &(((struct sockaddr_in *)addr->ai_addr)->sin_addr);
 262         else
 263                 p = &(((struct sockaddr_in6 *)addr->ai_addr)->sin6_addr);
 264
 265         if (!inet_ntop(addr->ai_family, p, ip, sizeof(ip))) {
 266                 syslog(LOG_ERR, "%s: inet_ntop: %s", __func__, strerror(errno));
 267                 freeaddrinfo(addr);
 268                 return 1;
 269         }
 270
 271         /* setup key */
 272         c = keyctl_instantiate(key, ip, strlen(ip)+1, 0);
 273         if (c == -1) {
 274                 syslog(LOG_ERR, "%s: keyctl_instantiate: %s", __func__,
 275                                 strerror(errno));
 276                 freeaddrinfo(addr);
 277                 return 1;
 278         }
 279
 280         freeaddrinfo(addr);
 281         return 0;
 282 }
 283
 284 static void
 285 usage(void)
 286 {
 287         syslog(LOG_INFO, "Usage: %s [-c] [-v] key_serial", prog);
 288         fprintf(stderr, "Usage: %s [-c] [-v] key_serial\n", prog);
 289 }
 290
 291 int main(const int argc, char *const argv[])
 292 {
 293         struct cifs_spnego_msg *keydata = NULL;
 294         DATA_BLOB secblob = data_blob_null;
 295         DATA_BLOB sess_key = data_blob_null;
 296         secType_t sectype = NONE;
 297         key_serial_t key = 0;
 298         size_t datalen;
 299         long rc = 1;
 300         uid_t uid = 0;
 301         pid_t pid = 0;
 302         int kernel_upcall_version = 0;
 303         int c, use_cifs_service_prefix = 0;
 304         char *buf, *princ, *ccname = NULL, *hostname = NULL;
 305         const char *oid;
 306
 307         openlog(prog, 0, LOG_DAEMON);
 308
 309         while ((c = getopt(argc, argv, "cv")) != -1) {
 310                 switch (c) {
 311                 case 'c':
 312                         use_cifs_service_prefix = 1;
 313                         break;
 314                 case 'v':
 315                         printf("version: %s\n", CIFSSPNEGO_VERSION);
 316                         goto out;
 317                 default:
 318                         syslog(LOG_ERR, "unknown option: %c", c);
 319                         goto out;
 320                 }
 321         }
 322
 323         /* is there a key? */
 324         if (argc <= optind) {
 325                 usage();
 326                 goto out;
 327         }
 328
 329         /* get key and keyring values */
 330         errno = 0;
 331         key = strtol(argv[optind], NULL, 10);
 332         if (errno != 0) {
 333                 key = 0;
 334                 syslog(LOG_ERR, "Invalid key format: %s", strerror(errno));
 335                 goto out;
 336         }
 337
 338         rc = keyctl_describe_alloc(key, &buf);
 339         if (rc == -1) {
 340                 syslog(LOG_ERR, "keyctl_describe_alloc failed: %s",
 341                        strerror(errno));
 342                 rc = 1;
 343                 goto out;
 344         }
 345
 346         syslog(LOG_DEBUG, "key description: %s", buf);
 347
 348         if ((strncmp(buf, "cifs.resolver", sizeof("cifs.resolver")-1) == 0) ||
 349             (strncmp(buf, "dns_resolver", sizeof("dns_resolver")-1) == 0)) {
 350                 rc = cifs_resolver(key, buf);
 351                 goto out;
 352         }
 353
 354         rc = decode_key_description(buf, &kernel_upcall_version, &sectype,
 355                                     &hostname, &uid, &pid);
 356         if ((rc & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) {
 357                 syslog(LOG_ERR, "unable to get necessary params from key "
 358                                 "description (0x%x)", rc);
 359                 rc = 1;
 360                 SAFE_FREE(buf);
 361                 goto out;
 362         }
 363         SAFE_FREE(buf);
 364
 365         if (kernel_upcall_version > CIFS_SPNEGO_UPCALL_VERSION) {
 366                 syslog(LOG_ERR, "incompatible kernel upcall version: 0x%x",
 367                                 kernel_upcall_version);
 368                 rc = 1;
 369                 goto out;
 370         }
 371
 372         if (rc & DKD_HAVE_PID)
 373                 ccname = get_krb5_ccname(pid);
 374
 375         if (rc & DKD_HAVE_UID) {
 376                 rc = setuid(uid);
 377                 if (rc == -1) {
 378                         syslog(LOG_ERR, "setuid: %s", strerror(errno));
 379                         goto out;
 380                 }
 381         }
 382
 383         // do mech specific authorization
 384         switch (sectype) {
 385         case MS_KRB5:
 386         case KRB5:
 387                 /* for "cifs/" service name + terminating 0 */
 388                 datalen = strlen(hostname) + 5 + 1;
 389                 princ = SMB_XMALLOC_ARRAY(char, datalen);
 390                 if (!princ) {
 391                         rc = 1;
 392                         break;
 393                 }
 394
 395                 if (use_cifs_service_prefix)
 396                         strlcpy(princ, "cifs/", datalen);
 397                 else
 398                         strlcpy(princ, "host/", datalen);
 399
 400                 strlcpy(princ + 5, hostname, datalen - 5);
 401
 402                 if (sectype == MS_KRB5)
 403                         oid = OID_KERBEROS5_OLD;
 404                 else
 405                         oid = OID_KERBEROS5;
 406
 407                 rc = handle_krb5_mech(oid, princ, &secblob, &sess_key, ccname);
 408                 SAFE_FREE(princ);
 409                 break;
 410         default:
 411                 syslog(LOG_ERR, "sectype: %d is not implemented", sectype);
 412                 rc = 1;
 413                 break;
 414         }
 415
 416         if (rc)
 417                 goto out;
 418
 419         /* pack SecurityBLob and SessionKey into downcall packet */
 420         datalen =
 421             sizeof(struct cifs_spnego_msg) + secblob.length + sess_key.length;
 422         keydata = (struct cifs_spnego_msg*)SMB_XMALLOC_ARRAY(char, datalen);
 423         if (!keydata) {
 424                 rc = 1;
 425                 goto out;
 426         }
 427         keydata->version = kernel_upcall_version;
 428         keydata->flags = 0;
 429         keydata->sesskey_len = sess_key.length;
 430         keydata->secblob_len = secblob.length;
 431         memcpy(&(keydata->data), sess_key.data, sess_key.length);
 432         memcpy(&(keydata->data) + keydata->sesskey_len,
 433                secblob.data, secblob.length);
 434
 435         /* setup key */
 436         rc = keyctl_instantiate(key, keydata, datalen, 0);
 437         if (rc == -1) {
 438                 syslog(LOG_ERR, "keyctl_instantiate: %s", strerror(errno));
 439                 goto out;
 440         }
 441
 442         /* BB: maybe we need use timeout for key: for example no more then
 443          * ticket lifietime? */
 444         /* keyctl_set_timeout( key, 60); */
 445 out:
 446         /*
 447          * on error, negatively instantiate the key ourselves so that we can
 448          * make sure the kernel doesn't hang it off of a searchable keyring
 449          * and interfere with the next attempt to instantiate the key.
 450          */
 451         if (rc != 0  && key == 0)
 452                 keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT);
 453         data_blob_free(&secblob);
 454         data_blob_free(&sess_key);
 455         SAFE_FREE(ccname);
 456         SAFE_FREE(hostname);
 457         SAFE_FREE(keydata);
 458         return rc;
 459 }