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 #include <getopt.h>
  31
  32 #include "cifs_spnego.h"
  33
  34 const char *CIFSSPNEGO_VERSION = "1.3";
  35 static const char *prog = "cifs.upcall";
  36 typedef enum _sectype {
  37         NONE = 0,
  38         KRB5,
  39         MS_KRB5
  40 } sectype_t;
  41
  42 /*
  43  * given a process ID, get the value of the KRB5CCNAME environment variable
  44  * in the context of that process. On error, just return NULL.
  45  */
  46 static char *
  47 get_krb5_ccname(pid_t pid)
  48 {
  49         int fd;
  50         ssize_t len, left;
  51
  52         /*
  53          * FIXME: sysconf for ARG_MAX instead? Kernel seems to be limited to a
  54          * page however, so it may not matter.
  55          */
  56         char buf[4096];
  57         char *p, *value = NULL;
  58
  59         buf[4095] = '\0';
  60         snprintf(buf, 4095, "/proc/%d/environ", pid);
  61         fd = open(buf, O_RDONLY);
  62         if (fd < 0) {
  63                 syslog(LOG_DEBUG, "%s: unable to open %s: %d", __func__, buf,
  64                         errno);
  65                 return NULL;
  66         }
  67
  68         /* FIXME: don't assume that we get it all in the first read? */
  69         len = read(fd, buf, 4096);
  70         close(fd);
  71         if (len < 0) {
  72                 syslog(LOG_DEBUG, "%s: unable to read from /proc/%d/environ: "
  73                                   "%d", __func__, pid, errno);
  74                 return NULL;
  75         }
  76
  77         left = len;
  78         p = buf;
  79
  80         /* can't have valid KRB5CCNAME if there are < 13 bytes left */
  81         while (left > 12) {
  82                 if (strncmp("KRB5CCNAME=", p, 11)) {
  83                         p += strnlen(p, left);
  84                         ++p;
  85                         left = buf + len - p;
  86                         continue;
  87                 }
  88                 p += 11;
  89                 left -= 11;
  90                 value = SMB_STRNDUP(p, left);
  91                 break;
  92         }
  93         syslog(LOG_DEBUG, "%s: KRB5CCNAME=%s", __func__,
  94                                 value ? value : "(null)");
  95         return value;
  96 }
  97
  98 /*
  99  * Prepares AP-REQ data for mechToken and gets session key
 100  * Uses credentials from cache. It will not ask for password
 101  * you should receive credentials for yuor name manually using
 102  * kinit or whatever you wish.
 103  *
 104  * in:
 105  *      oid -           string with OID/ Could be OID_KERBEROS5
 106  *                      or OID_KERBEROS5_OLD
 107  *      principal -     Service name.
 108  *                      Could be "cifs/FQDN" for KRB5 OID
 109  *                      or for MS_KRB5 OID style server principal
 110  *                      like "pdc$@YOUR.REALM.NAME"
 111  *
 112  * out:
 113  *      secblob -       pointer for spnego wrapped AP-REQ data to be stored
 114  *      sess_key-       pointer for SessionKey data to be stored
 115  *
 116  * ret: 0 - success, others - failure
 117  */
 118 static int
 119 handle_krb5_mech(const char *oid, const char *principal, DATA_BLOB *secblob,
 120                  DATA_BLOB *sess_key, const char *ccname)
 121 {
 122         int retval;
 123         DATA_BLOB tkt, tkt_wrapped;
 124
 125         syslog(LOG_DEBUG, "%s: getting service ticket for %s", __func__,
 126                           principal);
 127
 128         /* get a kerberos ticket for the service and extract the session key */
 129         retval = cli_krb5_get_ticket(principal, 0, &tkt, sess_key, 0, ccname,
 130                                      NULL);
 131
 132         if (retval) {
 133                 syslog(LOG_DEBUG, "%s: failed to obtain service ticket (%d)",
 134                                   __func__, retval);
 135                 return retval;
 136         }
 137
 138         syslog(LOG_DEBUG, "%s: obtained service ticket", __func__);
 139
 140         /* wrap that up in a nice GSS-API wrapping */
 141         tkt_wrapped = spnego_gen_krb5_wrap(tkt, TOK_ID_KRB_AP_REQ);
 142
 143         /* and wrap that in a shiny SPNEGO wrapper */
 144         *secblob = gen_negTokenInit(oid, tkt_wrapped);
 145
 146         data_blob_free(&tkt_wrapped);
 147         data_blob_free(&tkt);
 148         return retval;
 149 }
 150
 151 #define DKD_HAVE_HOSTNAME       0x1
 152 #define DKD_HAVE_VERSION        0x2
 153 #define DKD_HAVE_SEC            0x4
 154 #define DKD_HAVE_IP             0x8
 155 #define DKD_HAVE_UID            0x10
 156 #define DKD_HAVE_PID            0x20
 157 #define DKD_MUSTHAVE_SET (DKD_HAVE_HOSTNAME|DKD_HAVE_VERSION|DKD_HAVE_SEC)
 158
 159 struct decoded_args {
 160         int             ver;
 161         char            *hostname;
 162         char            *ip;
 163         uid_t           uid;
 164         pid_t           pid;
 165         sectype_t       sec;
 166 };
 167
 168 static unsigned int
 169 decode_key_description(const char *desc, struct decoded_args *arg)
 170 {
 171         int len;
 172         int retval = 0;
 173         char *pos;
 174         const char *tkn = desc;
 175
 176         do {
 177                 pos = index(tkn, ';');
 178                 if (strncmp(tkn, "host=", 5) == 0) {
 179
 180                         if (pos == NULL)
 181                                 len = strlen(tkn);
 182                         else
 183                                 len = pos - tkn;
 184
 185                         len -= 4;
 186                         SAFE_FREE(arg->hostname);
 187                         arg->hostname = SMB_XMALLOC_ARRAY(char, len);
 188                         strlcpy(arg->hostname, tkn + 5, len);
 189                         retval |= DKD_HAVE_HOSTNAME;
 190                 } else if (!strncmp(tkn, "ip4=", 4) ||
 191                            !strncmp(tkn, "ip6=", 4)) {
 192                         if (pos == NULL)
 193                                 len = strlen(tkn);
 194                         else
 195                                 len = pos - tkn;
 196
 197                         len -= 3;
 198                         SAFE_FREE(arg->ip);
 199                         arg->ip = SMB_XMALLOC_ARRAY(char, len);
 200                         strlcpy(arg->ip, tkn + 4, len);
 201                         retval |= DKD_HAVE_IP;
 202                 } else if (strncmp(tkn, "pid=", 4) == 0) {
 203                         errno = 0;
 204                         arg->pid = strtol(tkn + 4, NULL, 0);
 205                         if (errno != 0) {
 206                                 syslog(LOG_ERR, "Invalid pid format: %s",
 207                                        strerror(errno));
 208                                 return 1;
 209                         } else {
 210                                 retval |= DKD_HAVE_PID;
 211                         }
 212                 } else if (strncmp(tkn, "sec=", 4) == 0) {
 213                         if (strncmp(tkn + 4, "krb5", 4) == 0) {
 214                                 retval |= DKD_HAVE_SEC;
 215                                 arg->sec = KRB5;
 216                         } else if (strncmp(tkn + 4, "mskrb5", 6) == 0) {
 217                                 retval |= DKD_HAVE_SEC;
 218                                 arg->sec = MS_KRB5;
 219                         }
 220                 } else if (strncmp(tkn, "uid=", 4) == 0) {
 221                         errno = 0;
 222                         arg->uid = strtol(tkn + 4, NULL, 16);
 223                         if (errno != 0) {
 224                                 syslog(LOG_ERR, "Invalid uid format: %s",
 225                                        strerror(errno));
 226                                 return 1;
 227                         } else {
 228                                 retval |= DKD_HAVE_UID;
 229                         }
 230                 } else if (strncmp(tkn, "ver=", 4) == 0) {      /* if version */
 231                         errno = 0;
 232                         arg->ver = strtol(tkn + 4, NULL, 16);
 233                         if (errno != 0) {
 234                                 syslog(LOG_ERR, "Invalid version format: %s",
 235                                        strerror(errno));
 236                                 return 1;
 237                         } else {
 238                                 retval |= DKD_HAVE_VERSION;
 239                         }
 240                 }
 241                 if (pos == NULL)
 242                         break;
 243                 tkn = pos + 1;
 244         } while (tkn);
 245         return retval;
 246 }
 247
 248 static int
 249 cifs_resolver(const key_serial_t key, const char *key_descr)
 250 {
 251         int c;
 252         struct addrinfo *addr;
 253         char ip[INET6_ADDRSTRLEN];
 254         void *p;
 255         const char *keyend = key_descr;
 256         /* skip next 4 ';' delimiters to get to description */
 257         for (c = 1; c <= 4; c++) {
 258                 keyend = index(keyend+1, ';');
 259                 if (!keyend) {
 260                         syslog(LOG_ERR, "invalid key description: %s",
 261                                         key_descr);
 262                         return 1;
 263                 }
 264         }
 265         keyend++;
 266
 267         /* resolve name to ip */
 268         c = getaddrinfo(keyend, NULL, NULL, &addr);
 269         if (c) {
 270                 syslog(LOG_ERR, "unable to resolve hostname: %s [%s]",
 271                                 keyend, gai_strerror(c));
 272                 return 1;
 273         }
 274
 275         /* conver ip to string form */
 276         if (addr->ai_family == AF_INET)
 277                 p = &(((struct sockaddr_in *)addr->ai_addr)->sin_addr);
 278         else
 279                 p = &(((struct sockaddr_in6 *)addr->ai_addr)->sin6_addr);
 280
 281         if (!inet_ntop(addr->ai_family, p, ip, sizeof(ip))) {
 282                 syslog(LOG_ERR, "%s: inet_ntop: %s", __func__, strerror(errno));
 283                 freeaddrinfo(addr);
 284                 return 1;
 285         }
 286
 287         /* setup key */
 288         c = keyctl_instantiate(key, ip, strlen(ip)+1, 0);
 289         if (c == -1) {
 290                 syslog(LOG_ERR, "%s: keyctl_instantiate: %s", __func__,
 291                                 strerror(errno));
 292                 freeaddrinfo(addr);
 293                 return 1;
 294         }
 295
 296         freeaddrinfo(addr);
 297         return 0;
 298 }
 299
 300 /*
 301  * Older kernels sent IPv6 addresses without colons. Well, at least
 302  * they're fixed-length strings. Convert these addresses to have colon
 303  * delimiters to make getaddrinfo happy.
 304  */
 305 static void
 306 convert_inet6_addr(const char *from, char *to)
 307 {
 308         int i = 1;
 309
 310         while (*from) {
 311                 *to++ = *from++;
 312                 if (!(i++ % 4) && *from)
 313                         *to++ = ':';
 314         }
 315         *to = 0;
 316 }
 317
 318 static int
 319 ip_to_fqdn(const char *addrstr, char *host, size_t hostlen)
 320 {
 321         int rc;
 322         struct addrinfo hints = { .ai_flags = AI_NUMERICHOST };
 323         struct addrinfo *res;
 324         const char *ipaddr = addrstr;
 325         char converted[INET6_ADDRSTRLEN + 1];
 326
 327         if ((strlen(ipaddr) > INET_ADDRSTRLEN) && !strchr(ipaddr, ':')) {
 328                 convert_inet6_addr(ipaddr, converted);
 329                 ipaddr = converted;
 330         }
 331
 332         rc = getaddrinfo(ipaddr, NULL, &hints, &res);
 333         if (rc) {
 334                 syslog(LOG_DEBUG, "%s: failed to resolve %s to "
 335                         "ipaddr: %s", __func__, ipaddr,
 336                 rc == EAI_SYSTEM ? strerror(errno) : gai_strerror(rc));
 337                 return rc;
 338         }
 339
 340         rc = getnameinfo(res->ai_addr, res->ai_addrlen, host, hostlen,
 341                          NULL, 0, NI_NAMEREQD);
 342         freeaddrinfo(res);
 343         if (rc) {
 344                 syslog(LOG_DEBUG, "%s: failed to resolve %s to fqdn: %s",
 345                         __func__, ipaddr,
 346                         rc == EAI_SYSTEM ? strerror(errno) : gai_strerror(rc));
 347                 return rc;
 348         }
 349
 350         syslog(LOG_DEBUG, "%s: resolved %s to %s", __func__, ipaddr, host);
 351         return 0;
 352 }
 353
 354 static void
 355 usage(void)
 356 {
 357         syslog(LOG_INFO, "Usage: %s [-t] [-v] key_serial", prog);
 358         fprintf(stderr, "Usage: %s [-t] [-v] key_serial\n", prog);
 359 }
 360
 361 const struct option long_options[] = {
 362         { "trust-dns",  0, NULL, 't' },
 363         { "version",    0, NULL, 'v' },
 364         { NULL,         0, NULL, 0 }
 365 };
 366
 367 int main(const int argc, char *const argv[])
 368 {
 369         struct cifs_spnego_msg *keydata = NULL;
 370         DATA_BLOB secblob = data_blob_null;
 371         DATA_BLOB sess_key = data_blob_null;
 372         key_serial_t key = 0;
 373         size_t datalen;
 374         unsigned int have;
 375         long rc = 1;
 376         int c, try_dns = 0;
 377         char *buf, *princ = NULL, *ccname = NULL;
 378         char hostbuf[NI_MAXHOST], *host;
 379         struct decoded_args arg = { };
 380         const char *oid;
 381
 382         hostbuf[0] = '\0';
 383
 384         openlog(prog, 0, LOG_DAEMON);
 385
 386         while ((c = getopt_long(argc, argv, "ctv", long_options, NULL)) != -1) {
 387                 switch (c) {
 388                 case 'c':
 389                         /* legacy option -- skip it */
 390                         break;
 391                 case 't':
 392                         try_dns++;
 393                         break;
 394                 case 'v':
 395                         printf("version: %s\n", CIFSSPNEGO_VERSION);
 396                         goto out;
 397                 default:
 398                         syslog(LOG_ERR, "unknown option: %c", c);
 399                         goto out;
 400                 }
 401         }
 402
 403         /* is there a key? */
 404         if (argc <= optind) {
 405                 usage();
 406                 goto out;
 407         }
 408
 409         /* get key and keyring values */
 410         errno = 0;
 411         key = strtol(argv[optind], NULL, 10);
 412         if (errno != 0) {
 413                 key = 0;
 414                 syslog(LOG_ERR, "Invalid key format: %s", strerror(errno));
 415                 goto out;
 416         }
 417
 418         rc = keyctl_describe_alloc(key, &buf);
 419         if (rc == -1) {
 420                 syslog(LOG_ERR, "keyctl_describe_alloc failed: %s",
 421                        strerror(errno));
 422                 rc = 1;
 423                 goto out;
 424         }
 425
 426         syslog(LOG_DEBUG, "key description: %s", buf);
 427
 428         if ((strncmp(buf, "cifs.resolver", sizeof("cifs.resolver")-1) == 0) ||
 429             (strncmp(buf, "dns_resolver", sizeof("dns_resolver")-1) == 0)) {
 430                 rc = cifs_resolver(key, buf);
 431                 goto out;
 432         }
 433
 434         have = decode_key_description(buf, &arg);
 435         SAFE_FREE(buf);
 436         if ((have & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) {
 437                 syslog(LOG_ERR, "unable to get necessary params from key "
 438                                 "description (0x%x)", have);
 439                 rc = 1;
 440                 goto out;
 441         }
 442
 443         if (arg.ver > CIFS_SPNEGO_UPCALL_VERSION) {
 444                 syslog(LOG_ERR, "incompatible kernel upcall version: 0x%x",
 445                                 arg.ver);
 446                 rc = 1;
 447                 goto out;
 448         }
 449
 450         if (have & DKD_HAVE_UID) {
 451                 rc = setuid(arg.uid);
 452                 if (rc == -1) {
 453                         syslog(LOG_ERR, "setuid: %s", strerror(errno));
 454                         goto out;
 455                 }
 456         }
 457
 458         if (have & DKD_HAVE_PID)
 459                 ccname = get_krb5_ccname(arg.pid);
 460
 461         host = arg.hostname;
 462
 463         // do mech specific authorization
 464         switch (arg.sec) {
 465         case MS_KRB5:
 466         case KRB5:
 467 retry_new_hostname:
 468                 /* for "cifs/" service name + terminating 0 */
 469                 datalen = strlen(host) + 5 + 1;
 470                 princ = SMB_XMALLOC_ARRAY(char, datalen);
 471                 if (!princ) {
 472                         rc = -ENOMEM;
 473                         break;
 474                 }
 475
 476                 if (arg.sec == MS_KRB5)
 477                         oid = OID_KERBEROS5_OLD;
 478                 else
 479                         oid = OID_KERBEROS5;
 480
 481                 /*
 482                  * try getting a cifs/ principal first and then fall back to
 483                  * getting a host/ principal if that doesn't work.
 484                  */
 485                 strlcpy(princ, "cifs/", datalen);
 486                 strlcpy(princ + 5, host, datalen - 5);
 487                 rc = handle_krb5_mech(oid, princ, &secblob, &sess_key, ccname);
 488                 if (!rc)
 489                         break;
 490
 491                 memcpy(princ, "host/", 5);
 492                 rc = handle_krb5_mech(oid, princ, &secblob, &sess_key, ccname);
 493                 if (!rc)
 494                         break;
 495
 496                 if (!try_dns || !(have & DKD_HAVE_IP))
 497                         break;
 498
 499                 rc = ip_to_fqdn(arg.ip, hostbuf, sizeof(hostbuf));
 500                 if (rc)
 501                         break;
 502
 503                 SAFE_FREE(princ);
 504                 try_dns = 0;
 505                 host = hostbuf;
 506                 goto retry_new_hostname;
 507         default:
 508                 syslog(LOG_ERR, "sectype: %d is not implemented", arg.sec);
 509                 rc = 1;
 510                 break;
 511         }
 512
 513         SAFE_FREE(princ);
 514
 515         if (rc)
 516                 goto out;
 517
 518         /* pack SecurityBLob and SessionKey into downcall packet */
 519         datalen =
 520             sizeof(struct cifs_spnego_msg) + secblob.length + sess_key.length;
 521         keydata = (struct cifs_spnego_msg*)SMB_XMALLOC_ARRAY(char, datalen);
 522         if (!keydata) {
 523                 rc = 1;
 524                 goto out;
 525         }
 526         keydata->version = arg.ver;
 527         keydata->flags = 0;
 528         keydata->sesskey_len = sess_key.length;
 529         keydata->secblob_len = secblob.length;
 530         memcpy(&(keydata->data), sess_key.data, sess_key.length);
 531         memcpy(&(keydata->data) + keydata->sesskey_len,
 532                secblob.data, secblob.length);
 533
 534         /* setup key */
 535         rc = keyctl_instantiate(key, keydata, datalen, 0);
 536         if (rc == -1) {
 537                 syslog(LOG_ERR, "keyctl_instantiate: %s", strerror(errno));
 538                 goto out;
 539         }
 540
 541         /* BB: maybe we need use timeout for key: for example no more then
 542          * ticket lifietime? */
 543         /* keyctl_set_timeout( key, 60); */
 544 out:
 545         /*
 546          * on error, negatively instantiate the key ourselves so that we can
 547          * make sure the kernel doesn't hang it off of a searchable keyring
 548          * and interfere with the next attempt to instantiate the key.
 549          */
 550         if (rc != 0  && key == 0)
 551                 keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT);
 552         data_blob_free(&secblob);
 553         data_blob_free(&sess_key);
 554         SAFE_FREE(ccname);
 555         SAFE_FREE(arg.hostname);
 556         SAFE_FREE(arg.ip);
 557         SAFE_FREE(keydata);
 558         return rc;
 559 }