1 /*- 2 * Copyright (c) 2003-2004 Networks Associates Technology, Inc. 3 * Copyright (c) 2006 SPARTA, Inc. 4 * All rights reserved. 5 * 6 * This software was developed for the FreeBSD Project by Network 7 * Associates Laboratories, the Security Research Division of Network 8 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), 9 * as part of the DARPA CHATS research program. 10 * 11 * This software was enhanced by SPARTA ISSO under SPAWAR contract 12 * N66001-04-C-6019 ("SEFOS"). 13 * 14 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions 16 * are met: 17 * 1. Redistributions of source code must retain the above copyright 18 * notice, this list of conditions and the following disclaimer. 19 * 2. Redistributions in binary form must reproduce the above copyright 20 * notice, this list of conditions and the following disclaimer in the 21 * documentation and/or other materials provided with the distribution. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 /* 37 * Developed by the TrustedBSD Project. 38 * 39 * Administratively limit access to local UDP/TCP ports for binding purposes. 40 * Intended to be combined with net.inet.ip.portrange.reservedhigh to allow 41 * specific uids and gids to bind specific ports for specific purposes, 42 * while not opening the door to any user replacing an "official" service 43 * while you're restarting it. This only affects ports explicitly bound by 44 * the user process (either for listen/outgoing socket for TCP, or send/ 45 * receive for UDP). This module will not limit ports bound implicitly for 46 * out-going connections where the process hasn't explicitly selected a port: 47 * these are automatically selected by the IP stack. 48 * 49 * To use this module, security.mac.enforce_socket must be enabled, and you 50 * will probably want to twiddle the net.inet sysctl listed above. Then use 51 * sysctl(8) to modify the rules string: 52 * 53 * # sysctl security.mac.portacl.rules="uid:425:tcp:80,uid:425:tcp:79" 54 * 55 * This ruleset, for example, permits uid 425 to bind TCP ports 80 (http) and 56 * 79 (finger). User names and group names can't be used directly because 57 * the kernel only knows about uids and gids. 58 */ 59 60 #include <sys/param.h> 61 #include <sys/domain.h> 62 #include <sys/kernel.h> 63 #include <sys/lock.h> 64 #include <sys/malloc.h> 65 #include <sys/module.h> 66 #include <sys/mutex.h> 67 #include <sys/priv.h> 68 #include <sys/proc.h> 69 #include <sys/protosw.h> 70 #include <sys/queue.h> 71 #include <sys/systm.h> 72 #include <sys/sbuf.h> 73 #include <sys/socket.h> 74 #include <sys/socketvar.h> 75 #include <sys/sysctl.h> 76 77 #include <netinet/in.h> 78 #include <netinet/in_pcb.h> 79 80 #include <security/mac/mac_policy.h> 81 82 static SYSCTL_NODE(_security_mac, OID_AUTO, portacl, 83 CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 84 "TrustedBSD mac_portacl policy controls"); 85 86 static int portacl_enabled = 1; 87 SYSCTL_INT(_security_mac_portacl, OID_AUTO, enabled, CTLFLAG_RWTUN, 88 &portacl_enabled, 0, "Enforce portacl policy"); 89 90 static int portacl_suser_exempt = 1; 91 SYSCTL_INT(_security_mac_portacl, OID_AUTO, suser_exempt, CTLFLAG_RWTUN, 92 &portacl_suser_exempt, 0, "Privilege permits binding of any port"); 93 94 static int portacl_autoport_exempt = 1; 95 SYSCTL_INT(_security_mac_portacl, OID_AUTO, autoport_exempt, CTLFLAG_RWTUN, 96 &portacl_autoport_exempt, 0, "Allow automatic allocation through " 97 "binding port 0 if not IP_PORTRANGELOW"); 98 99 static int portacl_port_high = 1023; 100 SYSCTL_INT(_security_mac_portacl, OID_AUTO, port_high, CTLFLAG_RWTUN, 101 &portacl_port_high, 0, "Highest port to enforce for"); 102 103 static MALLOC_DEFINE(M_PORTACL, "portacl_rule", "Rules for mac_portacl"); 104 105 #define MAC_RULE_STRING_LEN 1024 106 107 #define RULE_GID 1 108 #define RULE_UID 2 109 #define RULE_PROTO_TCP 1 110 #define RULE_PROTO_UDP 2 111 struct rule { 112 id_t r_id; 113 int r_idtype; 114 u_int16_t r_port; 115 int r_protocol; 116 117 TAILQ_ENTRY(rule) r_entries; 118 }; 119 120 #define GID_STRING "gid" 121 #define TCP_STRING "tcp" 122 #define UID_STRING "uid" 123 #define UDP_STRING "udp" 124 125 /* 126 * Text format for the rule string is that a rule consists of a 127 * comma-separated list of elements. Each element is in the form 128 * idtype:id:protocol:portnumber, and constitutes granting of permission 129 * for the specified binding. 130 */ 131 132 static struct mtx rule_mtx; 133 static TAILQ_HEAD(rulehead, rule) rule_head; 134 static char rule_string[MAC_RULE_STRING_LEN]; 135 136 static void 137 toast_rules(struct rulehead *head) 138 { 139 struct rule *rule; 140 141 while ((rule = TAILQ_FIRST(head)) != NULL) { 142 TAILQ_REMOVE(head, rule, r_entries); 143 free(rule, M_PORTACL); 144 } 145 } 146 147 /* 148 * Note that there is an inherent race condition in the unload of modules 149 * and access via sysctl. 150 */ 151 static void 152 destroy(struct mac_policy_conf *mpc) 153 { 154 155 mtx_destroy(&rule_mtx); 156 toast_rules(&rule_head); 157 } 158 159 static void 160 init(struct mac_policy_conf *mpc) 161 { 162 163 mtx_init(&rule_mtx, "rule_mtx", NULL, MTX_DEF); 164 TAILQ_INIT(&rule_head); 165 } 166 167 /* 168 * Note: parsing routines are destructive on the passed string. 169 */ 170 static int 171 parse_rule_element(char *element, struct rule **rule) 172 { 173 char *idtype, *id, *protocol, *portnumber, *p; 174 struct rule *new; 175 int error; 176 177 error = 0; 178 new = malloc(sizeof(*new), M_PORTACL, M_ZERO | M_WAITOK); 179 180 idtype = strsep(&element, ":"); 181 if (idtype == NULL) { 182 error = EINVAL; 183 goto out; 184 } 185 id = strsep(&element, ":"); 186 if (id == NULL) { 187 error = EINVAL; 188 goto out; 189 } 190 new->r_id = strtol(id, &p, 10); 191 if (*p != '\0') { 192 error = EINVAL; 193 goto out; 194 } 195 if (strcmp(idtype, UID_STRING) == 0) 196 new->r_idtype = RULE_UID; 197 else if (strcmp(idtype, GID_STRING) == 0) 198 new->r_idtype = RULE_GID; 199 else { 200 error = EINVAL; 201 goto out; 202 } 203 protocol = strsep(&element, ":"); 204 if (protocol == NULL) { 205 error = EINVAL; 206 goto out; 207 } 208 if (strcmp(protocol, TCP_STRING) == 0) 209 new->r_protocol = RULE_PROTO_TCP; 210 else if (strcmp(protocol, UDP_STRING) == 0) 211 new->r_protocol = RULE_PROTO_UDP; 212 else { 213 error = EINVAL; 214 goto out; 215 } 216 portnumber = element; 217 if (portnumber == NULL) { 218 error = EINVAL; 219 goto out; 220 } 221 new->r_port = strtol(portnumber, &p, 10); 222 if (*p != '\0') { 223 error = EINVAL; 224 goto out; 225 } 226 227 out: 228 if (error != 0) { 229 free(new, M_PORTACL); 230 *rule = NULL; 231 } else 232 *rule = new; 233 return (error); 234 } 235 236 static int 237 parse_rules(char *string, struct rulehead *head) 238 { 239 struct rule *new; 240 char *element; 241 int error; 242 243 error = 0; 244 while ((element = strsep(&string, ",")) != NULL) { 245 if (strlen(element) == 0) 246 continue; 247 error = parse_rule_element(element, &new); 248 if (error) 249 goto out; 250 TAILQ_INSERT_TAIL(head, new, r_entries); 251 } 252 out: 253 if (error != 0) 254 toast_rules(head); 255 return (error); 256 } 257 258 /* 259 * rule_printf() and rules_to_string() are unused currently because they rely 260 * on sbufs with auto-extension, which may sleep while holding a mutex. 261 * Instead, the non-canonical user-generated rule string is returned to the 262 * user when the rules are queried, which is faster anyway. 263 */ 264 #if 0 265 static void 266 rule_printf(struct sbuf *sb, struct rule *rule) 267 { 268 const char *idtype, *protocol; 269 270 switch(rule->r_idtype) { 271 case RULE_GID: 272 idtype = GID_STRING; 273 break; 274 case RULE_UID: 275 idtype = UID_STRING; 276 break; 277 default: 278 panic("rule_printf: unknown idtype (%d)\n", rule->r_idtype); 279 } 280 281 switch (rule->r_protocol) { 282 case RULE_PROTO_TCP: 283 protocol = TCP_STRING; 284 break; 285 case RULE_PROTO_UDP: 286 protocol = UDP_STRING; 287 break; 288 default: 289 panic("rule_printf: unknown protocol (%d)\n", 290 rule->r_protocol); 291 } 292 sbuf_printf(sb, "%s:%jd:%s:%d", idtype, (intmax_t)rule->r_id, 293 protocol, rule->r_port); 294 } 295 296 static char * 297 rules_to_string(void) 298 { 299 struct rule *rule; 300 struct sbuf *sb; 301 int needcomma; 302 char *temp; 303 304 sb = sbuf_new_auto(); 305 needcomma = 0; 306 mtx_lock(&rule_mtx); 307 for (rule = TAILQ_FIRST(&rule_head); rule != NULL; 308 rule = TAILQ_NEXT(rule, r_entries)) { 309 if (!needcomma) 310 needcomma = 1; 311 else 312 sbuf_printf(sb, ","); 313 rule_printf(sb, rule); 314 } 315 mtx_unlock(&rule_mtx); 316 sbuf_finish(sb); 317 temp = strdup(sbuf_data(sb), M_PORTACL); 318 sbuf_delete(sb); 319 return (temp); 320 } 321 #endif 322 323 /* 324 * Note: due to races, there is not a single serializable order 325 * between parallel calls to the sysctl. 326 */ 327 static int 328 sysctl_rules(SYSCTL_HANDLER_ARGS) 329 { 330 char *string, *copy_string, *new_string; 331 struct rulehead head, save_head; 332 int error; 333 334 new_string = NULL; 335 if (req->newptr != NULL) { 336 new_string = malloc(MAC_RULE_STRING_LEN, M_PORTACL, 337 M_WAITOK | M_ZERO); 338 mtx_lock(&rule_mtx); 339 strcpy(new_string, rule_string); 340 mtx_unlock(&rule_mtx); 341 string = new_string; 342 } else 343 string = rule_string; 344 345 error = sysctl_handle_string(oidp, string, MAC_RULE_STRING_LEN, req); 346 if (error) 347 goto out; 348 349 if (req->newptr != NULL) { 350 copy_string = strdup(string, M_PORTACL); 351 TAILQ_INIT(&head); 352 error = parse_rules(copy_string, &head); 353 free(copy_string, M_PORTACL); 354 if (error) 355 goto out; 356 357 TAILQ_INIT(&save_head); 358 mtx_lock(&rule_mtx); 359 TAILQ_CONCAT(&save_head, &rule_head, r_entries); 360 TAILQ_CONCAT(&rule_head, &head, r_entries); 361 strcpy(rule_string, string); 362 mtx_unlock(&rule_mtx); 363 toast_rules(&save_head); 364 } 365 out: 366 if (new_string != NULL) 367 free(new_string, M_PORTACL); 368 return (error); 369 } 370 371 SYSCTL_PROC(_security_mac_portacl, OID_AUTO, rules, 372 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 373 0, 0, sysctl_rules, "A", 374 "Rules"); 375 376 static int 377 rules_check(struct ucred *cred, int family, int type, u_int16_t port) 378 { 379 struct rule *rule; 380 int error; 381 382 #if 0 383 printf("Check requested for euid %d, family %d, type %d, port %d\n", 384 cred->cr_uid, family, type, port); 385 #endif 386 387 if (port > portacl_port_high) 388 return (0); 389 390 error = EPERM; 391 mtx_lock(&rule_mtx); 392 for (rule = TAILQ_FIRST(&rule_head); 393 rule != NULL; 394 rule = TAILQ_NEXT(rule, r_entries)) { 395 if (type == SOCK_DGRAM && rule->r_protocol != RULE_PROTO_UDP) 396 continue; 397 if (type == SOCK_STREAM && rule->r_protocol != RULE_PROTO_TCP) 398 continue; 399 if (port != rule->r_port) 400 continue; 401 if (rule->r_idtype == RULE_UID) { 402 if (cred->cr_uid == rule->r_id) { 403 error = 0; 404 break; 405 } 406 } else if (rule->r_idtype == RULE_GID) { 407 if (cred->cr_gid == rule->r_id) { 408 error = 0; 409 break; 410 } else if (groupmember(rule->r_id, cred)) { 411 error = 0; 412 break; 413 } 414 } else 415 panic("rules_check: unknown rule type %d", 416 rule->r_idtype); 417 } 418 mtx_unlock(&rule_mtx); 419 420 if (error != 0 && portacl_suser_exempt != 0) 421 error = priv_check_cred(cred, PRIV_NETINET_RESERVEDPORT); 422 423 return (error); 424 } 425 426 /* 427 * Note, this only limits the ability to explicitly bind a port, it 428 * doesn't limit implicitly bound ports for outgoing connections where 429 * the source port is left up to the IP stack to determine automatically. 430 */ 431 static int 432 socket_check_bind(struct ucred *cred, struct socket *so, 433 struct label *solabel, struct sockaddr *sa) 434 { 435 struct sockaddr_in *sin; 436 struct inpcb *inp; 437 int family, type; 438 u_int16_t port; 439 440 /* Only run if we are enabled. */ 441 if (portacl_enabled == 0) 442 return (0); 443 444 /* Only interested in IPv4 and IPv6 sockets. */ 445 if (so->so_proto->pr_domain->dom_family != PF_INET && 446 so->so_proto->pr_domain->dom_family != PF_INET6) 447 return (0); 448 449 /* Currently, we don't attempt to deal with SOCK_RAW, etc. */ 450 if (so->so_type != SOCK_DGRAM && 451 so->so_type != SOCK_STREAM) 452 return (0); 453 454 /* Reject addresses we don't understand; fail closed. */ 455 if (sa->sa_family != AF_INET && sa->sa_family != AF_INET6) 456 return (EINVAL); 457 458 family = so->so_proto->pr_domain->dom_family; 459 type = so->so_type; 460 sin = (struct sockaddr_in *) sa; 461 port = ntohs(sin->sin_port); 462 463 /* 464 * Sockets are frequently bound with a specific IP address but a port 465 * number of '0' to request automatic port allocation. This is often 466 * desirable as long as IP_PORTRANGELOW isn't set, which might permit 467 * automatic allocation of a "privileged" port. The autoport exempt 468 * flag exempts port 0 allocation from rule checking as long as a low 469 * port isn't required. 470 */ 471 if (portacl_autoport_exempt && port == 0) { 472 inp = sotoinpcb(so); 473 if ((inp->inp_flags & INP_LOWPORT) == 0) 474 return (0); 475 } 476 477 return (rules_check(cred, family, type, port)); 478 } 479 480 static struct mac_policy_ops portacl_ops = 481 { 482 .mpo_destroy = destroy, 483 .mpo_init = init, 484 .mpo_socket_check_bind = socket_check_bind, 485 }; 486 487 MAC_POLICY_SET(&portacl_ops, mac_portacl, "TrustedBSD MAC/portacl", 488 MPC_LOADTIME_FLAG_UNLOADOK, NULL); 489 MODULE_VERSION(mac_portacl, 1); 490