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 = "1.3";
  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_IP             0x8
 154 #define DKD_HAVE_UID            0x10
 155 #define DKD_HAVE_PID            0x20
 156 #define DKD_MUSTHAVE_SET (DKD_HAVE_IP|DKD_HAVE_VERSION|DKD_HAVE_SEC)
 157
 158 static struct decoded_args {
 159         int             ver;
 160         char            *hostname;
 161         char            *ip;
 162         uid_t           uid;
 163         pid_t           pid;
 164         sectype_t       sec;
 165 };
 166
 167 static unsigned int
 168 decode_key_description(const char *desc, struct decoded_args *arg)
 169 {
 170         int len;
 171         int retval = 0;
 172         char *pos;
 173         const char *tkn = desc;
 174
 175         do {
 176                 pos = index(tkn, ';');
 177                 if (strncmp(tkn, "host=", 5) == 0) {
 178
 179                         if (pos == NULL)
 180                                 len = strlen(tkn);
 181                         else
 182                                 len = pos - tkn;
 183
 184                         len -= 4;
 185                         SAFE_FREE(arg->hostname);
 186                         arg->hostname = SMB_XMALLOC_ARRAY(char, len);
 187                         strlcpy(arg->hostname, tkn + 5, len);
 188                         retval |= DKD_HAVE_HOSTNAME;
 189                 } else if (!strncmp(tkn, "ip4=", 4) ||
 190                            !strncmp(tkn, "ip6=", 4)) {
 191                         if (pos == NULL)
 192                                 len = strlen(tkn);
 193                         else
 194                                 len = pos - tkn;
 195
 196                         len -= 3;
 197                         SAFE_FREE(arg->ip);
 198                         arg->ip = SMB_XMALLOC_ARRAY(char, len);
 199                         strlcpy(arg->ip, tkn + 4, len);
 200                         retval |= DKD_HAVE_IP;
 201                 } else if (strncmp(tkn, "pid=", 4) == 0) {
 202                         errno = 0;
 203                         arg->pid = strtol(tkn + 4, NULL, 0);
 204                         if (errno != 0) {
 205                                 syslog(LOG_ERR, "Invalid pid format: %s",
 206                                        strerror(errno));
 207                                 return 1;
 208                         } else {
 209                                 retval |= DKD_HAVE_PID;
 210                         }
 211                 } else if (strncmp(tkn, "sec=", 4) == 0) {
 212                         if (strncmp(tkn + 4, "krb5", 4) == 0) {
 213                                 retval |= DKD_HAVE_SEC;
 214                                 arg->sec = KRB5;
 215                         } else if (strncmp(tkn + 4, "mskrb5", 6) == 0) {
 216                                 retval |= DKD_HAVE_SEC;
 217                                 arg->sec = MS_KRB5;
 218                         }
 219                 } else if (strncmp(tkn, "uid=", 4) == 0) {
 220                         errno = 0;
 221                         arg->uid = strtol(tkn + 4, NULL, 16);
 222                         if (errno != 0) {
 223                                 syslog(LOG_ERR, "Invalid uid format: %s",
 224                                        strerror(errno));
 225                                 return 1;
 226                         } else {
 227                                 retval |= DKD_HAVE_UID;
 228                         }
 229                 } else if (strncmp(tkn, "ver=", 4) == 0) {      /* if version */
 230                         errno = 0;
 231                         arg->ver = strtol(tkn + 4, NULL, 16);
 232                         if (errno != 0) {
 233                                 syslog(LOG_ERR, "Invalid version format: %s",
 234                                        strerror(errno));
 235                                 return 1;
 236                         } else {
 237                                 retval |= DKD_HAVE_VERSION;
 238                         }
 239                 }
 240                 if (pos == NULL)
 241                         break;
 242                 tkn = pos + 1;
 243         } while (tkn);
 244         return retval;
 245 }
 246
 247 static int
 248 cifs_resolver(const key_serial_t key, const char *key_descr)
 249 {
 250         int c;
 251         struct addrinfo *addr;
 252         char ip[INET6_ADDRSTRLEN];
 253         void *p;
 254         const char *keyend = key_descr;
 255         /* skip next 4 ';' delimiters to get to description */
 256         for (c = 1; c <= 4; c++) {
 257                 keyend = index(keyend+1, ';');
 258                 if (!keyend) {
 259                         syslog(LOG_ERR, "invalid key description: %s",
 260                                         key_descr);
 261                         return 1;
 262                 }
 263         }
 264         keyend++;
 265
 266         /* resolve name to ip */
 267         c = getaddrinfo(keyend, NULL, NULL, &addr);
 268         if (c) {
 269                 syslog(LOG_ERR, "unable to resolve hostname: %s [%s]",
 270                                 keyend, gai_strerror(c));
 271                 return 1;
 272         }
 273
 274         /* conver ip to string form */
 275         if (addr->ai_family == AF_INET)
 276                 p = &(((struct sockaddr_in *)addr->ai_addr)->sin_addr);
 277         else
 278                 p = &(((struct sockaddr_in6 *)addr->ai_addr)->sin6_addr);
 279
 280         if (!inet_ntop(addr->ai_family, p, ip, sizeof(ip))) {
 281                 syslog(LOG_ERR, "%s: inet_ntop: %s", __func__, strerror(errno));
 282                 freeaddrinfo(addr);
 283                 return 1;
 284         }
 285
 286         /* setup key */
 287         c = keyctl_instantiate(key, ip, strlen(ip)+1, 0);
 288         if (c == -1) {
 289                 syslog(LOG_ERR, "%s: keyctl_instantiate: %s", __func__,
 290                                 strerror(errno));
 291                 freeaddrinfo(addr);
 292                 return 1;
 293         }
 294
 295         freeaddrinfo(addr);
 296         return 0;
 297 }
 298
 299 static int
 300 ip_to_fqdn(const char *ipaddr, char *host, size_t hostlen)
 301 {
 302         int rc;
 303         struct addrinfo hints = { .ai_flags = AI_NUMERICHOST };
 304         struct addrinfo *res;
 305
 306         rc = getaddrinfo(ipaddr, NULL, &hints, &res);
 307         if (rc) {
 308                 syslog(LOG_DEBUG, "%s: failed to resolve %s to ipaddr: %s",
 309                         __func__, ipaddr,
 310                         rc == EAI_SYSTEM ? strerror(errno) : gai_strerror(rc));
 311                 return rc;
 312         }
 313
 314         rc = getnameinfo(res->ai_addr, res->ai_addrlen, host, hostlen,
 315                          NULL, 0, NI_NAMEREQD);
 316         freeaddrinfo(res);
 317         if (rc) {
 318                 syslog(LOG_DEBUG, "%s: failed to resolve %s to fqdn: %s",
 319                         __func__, ipaddr,
 320                         rc == EAI_SYSTEM ? strerror(errno) : gai_strerror(rc));
 321                 return rc;
 322         }
 323
 324         syslog(LOG_DEBUG, "%s: resolved %s to %s", __func__, ipaddr, host);
 325         return 0;
 326 }
 327
 328 static void
 329 usage(void)
 330 {
 331         syslog(LOG_INFO, "Usage: %s [-v] key_serial", prog);
 332         fprintf(stderr, "Usage: %s [-v] key_serial\n", prog);
 333 }
 334
 335 int main(const int argc, char *const argv[])
 336 {
 337         struct cifs_spnego_msg *keydata = NULL;
 338         DATA_BLOB secblob = data_blob_null;
 339         DATA_BLOB sess_key = data_blob_null;
 340         key_serial_t key = 0;
 341         size_t datalen;
 342         unsigned int have;
 343         long rc = 1;
 344         int c;
 345         char *buf, *princ, *ccname = NULL;
 346         char hostbuf[NI_MAXHOST];
 347         struct decoded_args arg = { };
 348         const char *oid;
 349
 350         openlog(prog, 0, LOG_DAEMON);
 351
 352         while ((c = getopt(argc, argv, "cv")) != -1) {
 353                 switch (c) {
 354                 case 'c':
 355                         /* legacy option -- skip it */
 356                         break;
 357                 case 'v':
 358                         printf("version: %s\n", CIFSSPNEGO_VERSION);
 359                         goto out;
 360                 default:
 361                         syslog(LOG_ERR, "unknown option: %c", c);
 362                         goto out;
 363                 }
 364         }
 365
 366         /* is there a key? */
 367         if (argc <= optind) {
 368                 usage();
 369                 goto out;
 370         }
 371
 372         /* get key and keyring values */
 373         errno = 0;
 374         key = strtol(argv[optind], NULL, 10);
 375         if (errno != 0) {
 376                 key = 0;
 377                 syslog(LOG_ERR, "Invalid key format: %s", strerror(errno));
 378                 goto out;
 379         }
 380
 381         rc = keyctl_describe_alloc(key, &buf);
 382         if (rc == -1) {
 383                 syslog(LOG_ERR, "keyctl_describe_alloc failed: %s",
 384                        strerror(errno));
 385                 rc = 1;
 386                 goto out;
 387         }
 388
 389         syslog(LOG_DEBUG, "key description: %s", buf);
 390
 391         if ((strncmp(buf, "cifs.resolver", sizeof("cifs.resolver")-1) == 0) ||
 392             (strncmp(buf, "dns_resolver", sizeof("dns_resolver")-1) == 0)) {
 393                 rc = cifs_resolver(key, buf);
 394                 goto out;
 395         }
 396
 397         have = decode_key_description(buf, &arg);
 398         SAFE_FREE(buf);
 399         if ((have & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) {
 400                 syslog(LOG_ERR, "unable to get necessary params from key "
 401                                 "description (0x%x)", have);
 402                 rc = 1;
 403                 goto out;
 404         }
 405
 406         if (arg.ver > CIFS_SPNEGO_UPCALL_VERSION) {
 407                 syslog(LOG_ERR, "incompatible kernel upcall version: 0x%x",
 408                                 arg.ver);
 409                 rc = 1;
 410                 goto out;
 411         }
 412
 413         if (have & DKD_HAVE_UID) {
 414                 rc = setuid(arg.uid);
 415                 if (rc == -1) {
 416                         syslog(LOG_ERR, "setuid: %s", strerror(errno));
 417                         goto out;
 418                 }
 419         }
 420
 421         if (have & DKD_HAVE_PID)
 422                 ccname = get_krb5_ccname(arg.pid);
 423
 424         if (have & DKD_HAVE_IP) {
 425                 rc = ip_to_fqdn(arg.ip, hostbuf, sizeof(hostbuf));
 426                 if (rc)
 427                         goto out;
 428         }
 429
 430         // do mech specific authorization
 431         switch (arg.sec) {
 432         case MS_KRB5:
 433         case KRB5:
 434                 /* for "cifs/" service name + terminating 0 */
 435                 datalen = strnlen(hostbuf, sizeof(hostbuf)) + 5 + 1;
 436                 princ = SMB_XMALLOC_ARRAY(char, datalen);
 437                 if (!princ) {
 438                         rc = 1;
 439                         break;
 440                 }
 441
 442                 if (arg.sec == MS_KRB5)
 443                         oid = OID_KERBEROS5_OLD;
 444                 else
 445                         oid = OID_KERBEROS5;
 446
 447                 /*
 448                  * try getting a cifs/ principal first and then fall back to
 449                  * getting a host/ principal if that doesn't work.
 450                  */
 451                 strlcpy(princ, "cifs/", datalen);
 452                 strlcpy(princ + 5, hostbuf, datalen - 5);
 453                 rc = handle_krb5_mech(oid, princ, &secblob, &sess_key, ccname);
 454                 if (rc) {
 455                         memcpy(princ, "host/", 5);
 456                         rc = handle_krb5_mech(oid, princ, &secblob, &sess_key,
 457                                                 ccname);
 458                 }
 459                 SAFE_FREE(princ);
 460                 break;
 461         default:
 462                 syslog(LOG_ERR, "sectype: %d is not implemented", arg.sec);
 463                 rc = 1;
 464                 break;
 465         }
 466
 467         if (rc)
 468                 goto out;
 469
 470         /* pack SecurityBLob and SessionKey into downcall packet */
 471         datalen =
 472             sizeof(struct cifs_spnego_msg) + secblob.length + sess_key.length;
 473         keydata = (struct cifs_spnego_msg*)SMB_XMALLOC_ARRAY(char, datalen);
 474         if (!keydata) {
 475                 rc = 1;
 476                 goto out;
 477         }
 478         keydata->version = arg.ver;
 479         keydata->flags = 0;
 480         keydata->sesskey_len = sess_key.length;
 481         keydata->secblob_len = secblob.length;
 482         memcpy(&(keydata->data), sess_key.data, sess_key.length);
 483         memcpy(&(keydata->data) + keydata->sesskey_len,
 484                secblob.data, secblob.length);
 485
 486         /* setup key */
 487         rc = keyctl_instantiate(key, keydata, datalen, 0);
 488         if (rc == -1) {
 489                 syslog(LOG_ERR, "keyctl_instantiate: %s", strerror(errno));
 490                 goto out;
 491         }
 492
 493         /* BB: maybe we need use timeout for key: for example no more then
 494          * ticket lifietime? */
 495         /* keyctl_set_timeout( key, 60); */
 496 out:
 497         /*
 498          * on error, negatively instantiate the key ourselves so that we can
 499          * make sure the kernel doesn't hang it off of a searchable keyring
 500          * and interfere with the next attempt to instantiate the key.
 501          */
 502         if (rc != 0  && key == 0)
 503                 keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT);
 504         data_blob_free(&secblob);
 505         data_blob_free(&sess_key);
 506         SAFE_FREE(ccname);
 507         SAFE_FREE(arg.hostname);
 508         SAFE_FREE(keydata);
 509         return rc;
 510 }