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 * $FreeBSD$ 36 */ 37 38 /* 39 * Developed by the TrustedBSD Project. 40 * 41 * Administratively limit access to local UDP/TCP ports for binding purposes. 42 * Intended to be combined with net.inet.ip.portrange.reservedhigh to allow 43 * specific uids and gids to bind specific ports for specific purposes, 44 * while not opening the door to any user replacing an "official" service 45 * while you're restarting it. This only affects ports explicitly bound by 46 * the user process (either for listen/outgoing socket for TCP, or send/ 47 * receive for UDP). This module will not limit ports bound implicitly for 48 * out-going connections where the process hasn't explicitly selected a port: 49 * these are automatically selected by the IP stack. 50 * 51 * To use this module, security.mac.enforce_socket must be enabled, and you 52 * will probably want to twiddle the net.inet sysctl listed above. Then use 53 * sysctl(8) to modify the rules string: 54 * 55 * # sysctl security.mac.portacl.rules="uid:425:tcp:80,uid:425:tcp:79" 56 * 57 * This ruleset, for example, permits uid 425 to bind TCP ports 80 (http) and 58 * 79 (finger). User names and group names can't be used directly because 59 * the kernel only knows about uids and gids. 60 */ 61 62 #include <sys/param.h> 63 #include <sys/domain.h> 64 #include <sys/kernel.h> 65 #include <sys/lock.h> 66 #include <sys/malloc.h> 67 #include <sys/module.h> 68 #include <sys/mutex.h> 69 #include <sys/priv.h> 70 #include <sys/proc.h> 71 #include <sys/protosw.h> 72 #include <sys/queue.h> 73 #include <sys/systm.h> 74 #include <sys/sbuf.h> 75 #include <sys/socket.h> 76 #include <sys/socketvar.h> 77 #include <sys/sysctl.h> 78 79 #include <netinet/in.h> 80 #include <netinet/in_pcb.h> 81 82 #include <security/mac/mac_policy.h> 83 84 SYSCTL_DECL(_security_mac); 85 86 static SYSCTL_NODE(_security_mac, OID_AUTO, portacl, 87 CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 88 "TrustedBSD mac_portacl policy controls"); 89 90 static int portacl_enabled = 1; 91 SYSCTL_INT(_security_mac_portacl, OID_AUTO, enabled, CTLFLAG_RWTUN, 92 &portacl_enabled, 0, "Enforce portacl policy"); 93 94 static int portacl_suser_exempt = 1; 95 SYSCTL_INT(_security_mac_portacl, OID_AUTO, suser_exempt, CTLFLAG_RWTUN, 96 &portacl_suser_exempt, 0, "Privilege permits binding of any port"); 97 98 static int portacl_autoport_exempt = 1; 99 SYSCTL_INT(_security_mac_portacl, OID_AUTO, autoport_exempt, CTLFLAG_RWTUN, 100 &portacl_autoport_exempt, 0, "Allow automatic allocation through " 101 "binding port 0 if not IP_PORTRANGELOW"); 102 103 static int portacl_port_high = 1023; 104 SYSCTL_INT(_security_mac_portacl, OID_AUTO, port_high, CTLFLAG_RWTUN, 105 &portacl_port_high, 0, "Highest port to enforce for"); 106 107 static MALLOC_DEFINE(M_PORTACL, "portacl_rule", "Rules for mac_portacl"); 108 109 #define MAC_RULE_STRING_LEN 1024 110 111 #define RULE_GID 1 112 #define RULE_UID 2 113 #define RULE_PROTO_TCP 1 114 #define RULE_PROTO_UDP 2 115 struct rule { 116 id_t r_id; 117 int r_idtype; 118 u_int16_t r_port; 119 int r_protocol; 120 121 TAILQ_ENTRY(rule) r_entries; 122 }; 123 124 #define GID_STRING "gid" 125 #define TCP_STRING "tcp" 126 #define UID_STRING "uid" 127 #define UDP_STRING "udp" 128 129 /* 130 * Text format for the rule string is that a rule consists of a 131 * comma-separated list of elements. Each element is in the form 132 * idtype:id:protocol:portnumber, and constitutes granting of permission 133 * for the specified binding. 134 */ 135 136 static struct mtx rule_mtx; 137 static TAILQ_HEAD(rulehead, rule) rule_head; 138 static char rule_string[MAC_RULE_STRING_LEN]; 139 140 static void 141 toast_rules(struct rulehead *head) 142 { 143 struct rule *rule; 144 145 while ((rule = TAILQ_FIRST(head)) != NULL) { 146 TAILQ_REMOVE(head, rule, r_entries); 147 free(rule, M_PORTACL); 148 } 149 } 150 151 /* 152 * Note that there is an inherent race condition in the unload of modules 153 * and access via sysctl. 154 */ 155 static void 156 destroy(struct mac_policy_conf *mpc) 157 { 158 159 mtx_destroy(&rule_mtx); 160 toast_rules(&rule_head); 161 } 162 163 static void 164 init(struct mac_policy_conf *mpc) 165 { 166 167 mtx_init(&rule_mtx, "rule_mtx", NULL, MTX_DEF); 168 TAILQ_INIT(&rule_head); 169 } 170 171 /* 172 * Note: parsing routines are destructive on the passed string. 173 */ 174 static int 175 parse_rule_element(char *element, struct rule **rule) 176 { 177 char *idtype, *id, *protocol, *portnumber, *p; 178 struct rule *new; 179 int error; 180 181 error = 0; 182 new = malloc(sizeof(*new), M_PORTACL, M_ZERO | M_WAITOK); 183 184 idtype = strsep(&element, ":"); 185 if (idtype == NULL) { 186 error = EINVAL; 187 goto out; 188 } 189 id = strsep(&element, ":"); 190 if (id == NULL) { 191 error = EINVAL; 192 goto out; 193 } 194 new->r_id = strtol(id, &p, 10); 195 if (*p != '\0') { 196 error = EINVAL; 197 goto out; 198 } 199 if (strcmp(idtype, UID_STRING) == 0) 200 new->r_idtype = RULE_UID; 201 else if (strcmp(idtype, GID_STRING) == 0) 202 new->r_idtype = RULE_GID; 203 else { 204 error = EINVAL; 205 goto out; 206 } 207 protocol = strsep(&element, ":"); 208 if (protocol == NULL) { 209 error = EINVAL; 210 goto out; 211 } 212 if (strcmp(protocol, TCP_STRING) == 0) 213 new->r_protocol = RULE_PROTO_TCP; 214 else if (strcmp(protocol, UDP_STRING) == 0) 215 new->r_protocol = RULE_PROTO_UDP; 216 else { 217 error = EINVAL; 218 goto out; 219 } 220 portnumber = element; 221 if (portnumber == NULL) { 222 error = EINVAL; 223 goto out; 224 } 225 new->r_port = strtol(portnumber, &p, 10); 226 if (*p != '\0') { 227 error = EINVAL; 228 goto out; 229 } 230 231 out: 232 if (error != 0) { 233 free(new, M_PORTACL); 234 *rule = NULL; 235 } else 236 *rule = new; 237 return (error); 238 } 239 240 static int 241 parse_rules(char *string, struct rulehead *head) 242 { 243 struct rule *new; 244 char *element; 245 int error; 246 247 error = 0; 248 while ((element = strsep(&string, ",")) != NULL) { 249 if (strlen(element) == 0) 250 continue; 251 error = parse_rule_element(element, &new); 252 if (error) 253 goto out; 254 TAILQ_INSERT_TAIL(head, new, r_entries); 255 } 256 out: 257 if (error != 0) 258 toast_rules(head); 259 return (error); 260 } 261 262 /* 263 * rule_printf() and rules_to_string() are unused currently because they rely 264 * on sbufs with auto-extension, which may sleep while holding a mutex. 265 * Instead, the non-canonical user-generated rule string is returned to the 266 * user when the rules are queried, which is faster anyway. 267 */ 268 #if 0 269 static void 270 rule_printf(struct sbuf *sb, struct rule *rule) 271 { 272 const char *idtype, *protocol; 273 274 switch(rule->r_idtype) { 275 case RULE_GID: 276 idtype = GID_STRING; 277 break; 278 case RULE_UID: 279 idtype = UID_STRING; 280 break; 281 default: 282 panic("rule_printf: unknown idtype (%d)\n", rule->r_idtype); 283 } 284 285 switch (rule->r_protocol) { 286 case RULE_PROTO_TCP: 287 protocol = TCP_STRING; 288 break; 289 case RULE_PROTO_UDP: 290 protocol = UDP_STRING; 291 break; 292 default: 293 panic("rule_printf: unknown protocol (%d)\n", 294 rule->r_protocol); 295 } 296 sbuf_printf(sb, "%s:%jd:%s:%d", idtype, (intmax_t)rule->r_id, 297 protocol, rule->r_port); 298 } 299 300 static char * 301 rules_to_string(void) 302 { 303 struct rule *rule; 304 struct sbuf *sb; 305 int needcomma; 306 char *temp; 307 308 sb = sbuf_new_auto(); 309 needcomma = 0; 310 mtx_lock(&rule_mtx); 311 for (rule = TAILQ_FIRST(&rule_head); rule != NULL; 312 rule = TAILQ_NEXT(rule, r_entries)) { 313 if (!needcomma) 314 needcomma = 1; 315 else 316 sbuf_printf(sb, ","); 317 rule_printf(sb, rule); 318 } 319 mtx_unlock(&rule_mtx); 320 sbuf_finish(sb); 321 temp = strdup(sbuf_data(sb), M_PORTACL); 322 sbuf_delete(sb); 323 return (temp); 324 } 325 #endif 326 327 /* 328 * Note: due to races, there is not a single serializable order 329 * between parallel calls to the sysctl. 330 */ 331 static int 332 sysctl_rules(SYSCTL_HANDLER_ARGS) 333 { 334 char *string, *copy_string, *new_string; 335 struct rulehead head, save_head; 336 int error; 337 338 new_string = NULL; 339 if (req->newptr != NULL) { 340 new_string = malloc(MAC_RULE_STRING_LEN, M_PORTACL, 341 M_WAITOK | M_ZERO); 342 mtx_lock(&rule_mtx); 343 strcpy(new_string, rule_string); 344 mtx_unlock(&rule_mtx); 345 string = new_string; 346 } else 347 string = rule_string; 348 349 error = sysctl_handle_string(oidp, string, MAC_RULE_STRING_LEN, req); 350 if (error) 351 goto out; 352 353 if (req->newptr != NULL) { 354 copy_string = strdup(string, M_PORTACL); 355 TAILQ_INIT(&head); 356 error = parse_rules(copy_string, &head); 357 free(copy_string, M_PORTACL); 358 if (error) 359 goto out; 360 361 TAILQ_INIT(&save_head); 362 mtx_lock(&rule_mtx); 363 TAILQ_CONCAT(&save_head, &rule_head, r_entries); 364 TAILQ_CONCAT(&rule_head, &head, r_entries); 365 strcpy(rule_string, string); 366 mtx_unlock(&rule_mtx); 367 toast_rules(&save_head); 368 } 369 out: 370 if (new_string != NULL) 371 free(new_string, M_PORTACL); 372 return (error); 373 } 374 375 SYSCTL_PROC(_security_mac_portacl, OID_AUTO, rules, 376 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 377 0, 0, sysctl_rules, "A", 378 "Rules"); 379 380 static int 381 rules_check(struct ucred *cred, int family, int type, u_int16_t port) 382 { 383 struct rule *rule; 384 int error; 385 386 #if 0 387 printf("Check requested for euid %d, family %d, type %d, port %d\n", 388 cred->cr_uid, family, type, port); 389 #endif 390 391 if (port > portacl_port_high) 392 return (0); 393 394 error = EPERM; 395 mtx_lock(&rule_mtx); 396 for (rule = TAILQ_FIRST(&rule_head); 397 rule != NULL; 398 rule = TAILQ_NEXT(rule, r_entries)) { 399 if (type == SOCK_DGRAM && rule->r_protocol != RULE_PROTO_UDP) 400 continue; 401 if (type == SOCK_STREAM && rule->r_protocol != RULE_PROTO_TCP) 402 continue; 403 if (port != rule->r_port) 404 continue; 405 if (rule->r_idtype == RULE_UID) { 406 if (cred->cr_uid == rule->r_id) { 407 error = 0; 408 break; 409 } 410 } else if (rule->r_idtype == RULE_GID) { 411 if (cred->cr_gid == rule->r_id) { 412 error = 0; 413 break; 414 } else if (groupmember(rule->r_id, cred)) { 415 error = 0; 416 break; 417 } 418 } else 419 panic("rules_check: unknown rule type %d", 420 rule->r_idtype); 421 } 422 mtx_unlock(&rule_mtx); 423 424 if (error != 0 && portacl_suser_exempt != 0) 425 error = priv_check_cred(cred, PRIV_NETINET_RESERVEDPORT); 426 427 return (error); 428 } 429 430 /* 431 * Note, this only limits the ability to explicitly bind a port, it 432 * doesn't limit implicitly bound ports for outgoing connections where 433 * the source port is left up to the IP stack to determine automatically. 434 */ 435 static int 436 socket_check_bind(struct ucred *cred, struct socket *so, 437 struct label *solabel, struct sockaddr *sa) 438 { 439 struct sockaddr_in *sin; 440 struct inpcb *inp; 441 int family, type; 442 u_int16_t port; 443 444 /* Only run if we are enabled. */ 445 if (portacl_enabled == 0) 446 return (0); 447 448 /* Only interested in IPv4 and IPv6 sockets. */ 449 if (so->so_proto->pr_domain->dom_family != PF_INET && 450 so->so_proto->pr_domain->dom_family != PF_INET6) 451 return (0); 452 453 /* Currently, we don't attempt to deal with SOCK_RAW, etc. */ 454 if (so->so_type != SOCK_DGRAM && 455 so->so_type != SOCK_STREAM) 456 return (0); 457 458 /* Reject addresses we don't understand; fail closed. */ 459 if (sa->sa_family != AF_INET && sa->sa_family != AF_INET6) 460 return (EINVAL); 461 462 family = so->so_proto->pr_domain->dom_family; 463 type = so->so_type; 464 sin = (struct sockaddr_in *) sa; 465 port = ntohs(sin->sin_port); 466 467 /* 468 * Sockets are frequently bound with a specific IP address but a port 469 * number of '0' to request automatic port allocation. This is often 470 * desirable as long as IP_PORTRANGELOW isn't set, which might permit 471 * automatic allocation of a "privileged" port. The autoport exempt 472 * flag exempts port 0 allocation from rule checking as long as a low 473 * port isn't required. 474 */ 475 if (portacl_autoport_exempt && port == 0) { 476 inp = sotoinpcb(so); 477 if ((inp->inp_flags & INP_LOWPORT) == 0) 478 return (0); 479 } 480 481 return (rules_check(cred, family, type, port)); 482 } 483 484 static struct mac_policy_ops portacl_ops = 485 { 486 .mpo_destroy = destroy, 487 .mpo_init = init, 488 .mpo_socket_check_bind = socket_check_bind, 489 }; 490 491 MAC_POLICY_SET(&portacl_ops, mac_portacl, "TrustedBSD MAC/portacl", 492 MPC_LOADTIME_FLAG_UNLOADOK, NULL); 493 MODULE_VERSION(mac_portacl, 1); 494