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                 return NULL;
  63
  64         /* FIXME: don't assume that we get it all in the first read? */
  65         len = read(fd, buf, 4096);
  66         close(fd);
  67         if (len < 0)
  68                 return NULL;
  69
  70         left = len;
  71         p = buf;
  72
  73         /* can't have valid KRB5CCNAME if there are < 13 bytes left */
  74         while (left > 12) {
  75                 if (strncmp("KRB5CCNAME=", p, 11)) {
  76                         p += strnlen(p, left);
  77                         ++p;
  78                         left = buf + len - p;
  79                         continue;
  80                 }
  81                 p += 11;
  82                 left -= 11;
  83                 value = SMB_STRNDUP(p, left);
  84                 break;
  85         }
  86         return value;
  87 }
  88
  89 /*
  90  * Prepares AP-REQ data for mechToken and gets session key
  91  * Uses credentials from cache. It will not ask for password
  92  * you should receive credentials for yuor name manually using
  93  * kinit or whatever you wish.
  94  *
  95  * in:
  96  *      oid -           string with OID/ Could be OID_KERBEROS5
  97  *                      or OID_KERBEROS5_OLD
  98  *      principal -     Service name.
  99  *                      Could be "cifs/FQDN" for KRB5 OID
 100  *                      or for MS_KRB5 OID style server principal
 101  *                      like "pdc$@YOUR.REALM.NAME"
 102  *
 103  * out:
 104  *      secblob -       pointer for spnego wrapped AP-REQ data to be stored
 105  *      sess_key-       pointer for SessionKey data to be stored
 106  *
 107  * ret: 0 - success, others - failure
 108 */
 109 static int
 110 handle_krb5_mech(const char *oid, const char *principal, DATA_BLOB *secblob,
 111                  DATA_BLOB *sess_key, const char *ccname)
 112 {
 113         int retval;
 114         DATA_BLOB tkt, tkt_wrapped;
 115
 116         /* get a kerberos ticket for the service and extract the session key */
 117         retval = cli_krb5_get_ticket(principal, 0, &tkt, sess_key, 0, ccname,
 118                                      NULL);
 119
 120         if (retval)
 121                 return retval;
 122
 123         /* wrap that up in a nice GSS-API wrapping */
 124         tkt_wrapped = spnego_gen_krb5_wrap(tkt, TOK_ID_KRB_AP_REQ);
 125
 126         /* and wrap that in a shiny SPNEGO wrapper */
 127         *secblob = gen_negTokenInit(oid, tkt_wrapped);
 128
 129         data_blob_free(&tkt_wrapped);
 130         data_blob_free(&tkt);
 131         return retval;
 132 }
 133
 134 #define DKD_HAVE_HOSTNAME       1
 135 #define DKD_HAVE_VERSION        2
 136 #define DKD_HAVE_SEC            4
 137 #define DKD_HAVE_IPV4           8
 138 #define DKD_HAVE_IPV6           16
 139 #define DKD_HAVE_UID            32
 140 #define DKD_HAVE_PID            64
 141 #define DKD_MUSTHAVE_SET (DKD_HAVE_HOSTNAME|DKD_HAVE_VERSION|DKD_HAVE_SEC)
 142
 143 static int
 144 decode_key_description(const char *desc, int *ver, secType_t *sec,
 145                            char **hostname, uid_t *uid, pid_t *pid)
 146 {
 147         int retval = 0;
 148         char *pos;
 149         const char *tkn = desc;
 150
 151         do {
 152                 pos = index(tkn, ';');
 153                 if (strncmp(tkn, "host=", 5) == 0) {
 154                         int len;
 155
 156                         if (pos == NULL) {
 157                                 len = strlen(tkn);
 158                         } else {
 159                                 len = pos - tkn;
 160                         }
 161                         len -= 4;
 162                         SAFE_FREE(*hostname);
 163                         *hostname = SMB_XMALLOC_ARRAY(char, len);
 164                         strlcpy(*hostname, tkn + 5, len);
 165                         retval |= DKD_HAVE_HOSTNAME;
 166                 } else if (strncmp(tkn, "ipv4=", 5) == 0) {
 167                         /* BB: do we need it if we have hostname already? */
 168                 } else if (strncmp(tkn, "ipv6=", 5) == 0) {
 169                         /* BB: do we need it if we have hostname already? */
 170                 } else if (strncmp(tkn, "pid=", 4) == 0) {
 171                         errno = 0;
 172                         *pid = strtol(tkn + 4, NULL, 0);
 173                         if (errno != 0) {
 174                                 syslog(LOG_WARNING, "Invalid pid format: %s",
 175                                        strerror(errno));
 176                                 return 1;
 177                         } else {
 178                                 retval |= DKD_HAVE_PID;
 179                         }
 180                 } else if (strncmp(tkn, "sec=", 4) == 0) {
 181                         if (strncmp(tkn + 4, "krb5", 4) == 0) {
 182                                 retval |= DKD_HAVE_SEC;
 183                                 *sec = KRB5;
 184                         } else if (strncmp(tkn + 4, "mskrb5", 6) == 0) {
 185                                 retval |= DKD_HAVE_SEC;
 186                                 *sec = MS_KRB5;
 187                         }
 188                 } else if (strncmp(tkn, "uid=", 4) == 0) {
 189                         errno = 0;
 190                         *uid = strtol(tkn + 4, NULL, 16);
 191                         if (errno != 0) {
 192                                 syslog(LOG_WARNING, "Invalid uid format: %s",
 193                                        strerror(errno));
 194                                 return 1;
 195                         } else {
 196                                 retval |= DKD_HAVE_UID;
 197                         }
 198                 } else if (strncmp(tkn, "ver=", 4) == 0) {      /* if version */
 199                         errno = 0;
 200                         *ver = strtol(tkn + 4, NULL, 16);
 201                         if (errno != 0) {
 202                                 syslog(LOG_WARNING,
 203                                        "Invalid version format: %s",
 204                                        strerror(errno));
 205                                 return 1;
 206                         } else {
 207                                 retval |= DKD_HAVE_VERSION;
 208                         }
 209                 }
 210                 if (pos == NULL)
 211                         break;
 212                 tkn = pos + 1;
 213         } while (tkn);
 214         return retval;
 215 }
 216
 217 static int
 218 cifs_resolver(const key_serial_t key, const char *key_descr)
 219 {
 220         int c;
 221         struct addrinfo *addr;
 222         char ip[INET6_ADDRSTRLEN];
 223         void *p;
 224         const char *keyend = key_descr;
 225         /* skip next 4 ';' delimiters to get to description */
 226         for (c = 1; c <= 4; c++) {
 227                 keyend = index(keyend+1, ';');
 228                 if (!keyend) {
 229                         syslog(LOG_WARNING, "invalid key description: %s",
 230                                         key_descr);
 231                         return 1;
 232                 }
 233         }
 234         keyend++;
 235
 236         /* resolve name to ip */
 237         c = getaddrinfo(keyend, NULL, NULL, &addr);
 238         if (c) {
 239                 syslog(LOG_WARNING, "unable to resolve hostname: %s [%s]",
 240                                 keyend, gai_strerror(c));
 241                 return 1;
 242         }
 243
 244         /* conver ip to string form */
 245         if (addr->ai_family == AF_INET) {
 246                 p = &(((struct sockaddr_in *)addr->ai_addr)->sin_addr);
 247         } else {
 248                 p = &(((struct sockaddr_in6 *)addr->ai_addr)->sin6_addr);
 249         }
 250         if (!inet_ntop(addr->ai_family, p, ip, sizeof(ip))) {
 251                 syslog(LOG_WARNING, "%s: inet_ntop: %s",
 252                                 __FUNCTION__, strerror(errno));
 253                 freeaddrinfo(addr);
 254                 return 1;
 255         }
 256
 257         /* setup key */
 258         c = keyctl_instantiate(key, ip, strlen(ip)+1, 0);
 259         if (c == -1) {
 260                 syslog(LOG_WARNING, "%s: keyctl_instantiate: %s",
 261                                 __FUNCTION__, strerror(errno));
 262                 freeaddrinfo(addr);
 263                 return 1;
 264         }
 265
 266         freeaddrinfo(addr);
 267         return 0;
 268 }
 269
 270 static void
 271 usage(void)
 272 {
 273         syslog(LOG_WARNING, "Usage: %s [-c] [-v] key_serial", prog);
 274         fprintf(stderr, "Usage: %s [-c] [-v] key_serial\n", prog);
 275 }
 276
 277 int main(const int argc, char *const argv[])
 278 {
 279         struct cifs_spnego_msg *keydata = NULL;
 280         DATA_BLOB secblob = data_blob_null;
 281         DATA_BLOB sess_key = data_blob_null;
 282         secType_t sectype = NONE;
 283         key_serial_t key = 0;
 284         size_t datalen;
 285         long rc = 1;
 286         uid_t uid = 0;
 287         pid_t pid = 0;
 288         int kernel_upcall_version = 0;
 289         int c, use_cifs_service_prefix = 0;
 290         char *buf, *ccname = NULL, *hostname = NULL;
 291         const char *oid;
 292
 293         openlog(prog, 0, LOG_DAEMON);
 294
 295         while ((c = getopt(argc, argv, "cv")) != -1) {
 296                 switch (c) {
 297                 case 'c':{
 298                         use_cifs_service_prefix = 1;
 299                         break;
 300                         }
 301                 case 'v':{
 302                         printf("version: %s\n", CIFSSPNEGO_VERSION);
 303                         goto out;
 304                         }
 305                 default:{
 306                         syslog(LOG_WARNING, "unknown option: %c", c);
 307                         goto out;
 308                         }
 309                 }
 310         }
 311
 312         /* is there a key? */
 313         if (argc <= optind) {
 314                 usage();
 315                 goto out;
 316         }
 317
 318         /* get key and keyring values */
 319         errno = 0;
 320         key = strtol(argv[optind], NULL, 10);
 321         if (errno != 0) {
 322                 key = 0;
 323                 syslog(LOG_WARNING, "Invalid key format: %s", strerror(errno));
 324                 goto out;
 325         }
 326
 327         rc = keyctl_describe_alloc(key, &buf);
 328         if (rc == -1) {
 329                 syslog(LOG_WARNING, "keyctl_describe_alloc failed: %s",
 330                        strerror(errno));
 331                 rc = 1;
 332                 goto out;
 333         }
 334
 335         if ((strncmp(buf, "cifs.resolver", sizeof("cifs.resolver")-1) == 0) ||
 336             (strncmp(buf, "dns_resolver", sizeof("dns_resolver")-1) == 0)) {
 337                 rc = cifs_resolver(key, buf);
 338                 goto out;
 339         }
 340
 341         rc = decode_key_description(buf, &kernel_upcall_version, &sectype,
 342                                     &hostname, &uid, &pid);
 343         if ((rc & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) {
 344                 syslog(LOG_WARNING,
 345                        "unable to get from description necessary params");
 346                 rc = 1;
 347                 SAFE_FREE(buf);
 348                 goto out;
 349         }
 350         SAFE_FREE(buf);
 351
 352         if (kernel_upcall_version > CIFS_SPNEGO_UPCALL_VERSION) {
 353                 syslog(LOG_WARNING,
 354                        "incompatible kernel upcall version: 0x%x",
 355                        kernel_upcall_version);
 356                 rc = 1;
 357                 goto out;
 358         }
 359
 360         if (rc & DKD_HAVE_PID)
 361                 ccname = get_krb5_ccname(pid);
 362
 363         if (rc & DKD_HAVE_UID) {
 364                 rc = setuid(uid);
 365                 if (rc == -1) {
 366                         syslog(LOG_WARNING, "setuid: %s", strerror(errno));
 367                         goto out;
 368                 }
 369         }
 370
 371         // do mech specific authorization
 372         switch (sectype) {
 373         case MS_KRB5:
 374         case KRB5:{
 375                         char *princ;
 376                         size_t len;
 377
 378                         /* for "cifs/" service name + terminating 0 */
 379                         len = strlen(hostname) + 5 + 1;
 380                         princ = SMB_XMALLOC_ARRAY(char, len);
 381                         if (!princ) {
 382                                 rc = 1;
 383                                 break;
 384                         }
 385                         if (use_cifs_service_prefix) {
 386                                 strlcpy(princ, "cifs/", len);
 387                         } else {
 388                                 strlcpy(princ, "host/", len);
 389                         }
 390                         strlcpy(princ + 5, hostname, len - 5);
 391
 392                         if (sectype == MS_KRB5)
 393                                 oid = OID_KERBEROS5_OLD;
 394                         else
 395                                 oid = OID_KERBEROS5;
 396
 397                         rc = handle_krb5_mech(oid, princ, &secblob, &sess_key,
 398                                               ccname);
 399                         SAFE_FREE(princ);
 400                         break;
 401                 }
 402         default:{
 403                         syslog(LOG_WARNING, "sectype: %d is not implemented",
 404                                sectype);
 405                         rc = 1;
 406                         break;
 407                 }
 408         }
 409
 410         if (rc) {
 411                 goto out;
 412         }
 413
 414         /* pack SecurityBLob and SessionKey into downcall packet */
 415         datalen =
 416             sizeof(struct cifs_spnego_msg) + secblob.length + sess_key.length;
 417         keydata = (struct cifs_spnego_msg*)SMB_XMALLOC_ARRAY(char, datalen);
 418         if (!keydata) {
 419                 rc = 1;
 420                 goto out;
 421         }
 422         keydata->version = kernel_upcall_version;
 423         keydata->flags = 0;
 424         keydata->sesskey_len = sess_key.length;
 425         keydata->secblob_len = secblob.length;
 426         memcpy(&(keydata->data), sess_key.data, sess_key.length);
 427         memcpy(&(keydata->data) + keydata->sesskey_len,
 428                secblob.data, secblob.length);
 429
 430         /* setup key */
 431         rc = keyctl_instantiate(key, keydata, datalen, 0);
 432         if (rc == -1) {
 433                 syslog(LOG_WARNING, "keyctl_instantiate: %s", strerror(errno));
 434                 goto out;
 435         }
 436
 437         /* BB: maybe we need use timeout for key: for example no more then
 438          * ticket lifietime? */
 439         /* keyctl_set_timeout( key, 60); */
 440 out:
 441         /*
 442          * on error, negatively instantiate the key ourselves so that we can
 443          * make sure the kernel doesn't hang it off of a searchable keyring
 444          * and interfere with the next attempt to instantiate the key.
 445          */
 446         if (rc != 0  && key == 0)
 447                 keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT);
 448         data_blob_free(&secblob);
 449         data_blob_free(&sess_key);
 450         SAFE_FREE(ccname);
 451         SAFE_FREE(hostname);
 452         SAFE_FREE(keydata);
 453         return rc;
 454 }