1 /*- 2 * Copyright (c) 2003-2004 Networks Associates Technology, Inc. 3 * All rights reserved. 4 * 5 * This software was developed for the FreeBSD Project by Network 6 * Associates Laboratories, the Security Research Division of Network 7 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), 8 * as part of the DARPA CHATS research program. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * $FreeBSD$ 32 */ 33 34 /* 35 * Developed by the TrustedBSD Project. 36 * 37 * Administratively limit access to local UDP/TCP ports for binding purposes. 38 * Intended to be combined with net.inet.ip.portrange.reservedhigh to allow 39 * specific uids and gids to bind specific ports for specific purposes, 40 * while not opening the door to any user replacing an "official" service 41 * while you're restarting it. This only affects ports explicitly bound by 42 * the user process (either for listen/outgoing socket for TCP, or send/ 43 * receive for UDP). This module will not limit ports bound implicitly for 44 * out-going connections where the process hasn't explicitly selected a port: 45 * these are automatically selected by the IP stack. 46 * 47 * To use this module, security.mac.enforce_socket must be enabled, and 48 * you will probably want to twiddle the net.inet sysctl listed above. 49 * Then use sysctl(8) to modify the rules string: 50 * 51 * # sysctl security.mac.portacl.rules="uid:425:tcp:80,uid:425:tcp:79" 52 * 53 * This ruleset, for example, permits uid 425 to bind TCP ports 80 (http) 54 * and 79 (finger). User names and group names can't be used directly 55 * because the kernel only knows about uids and gids. 56 */ 57 58 #include <sys/types.h> 59 #include <sys/param.h> 60 #include <sys/conf.h> 61 #include <sys/domain.h> 62 #include <sys/kernel.h> 63 #include <sys/libkern.h> 64 #include <sys/lock.h> 65 #include <sys/mac.h> 66 #include <sys/malloc.h> 67 #include <sys/mount.h> 68 #include <sys/mutex.h> 69 #include <sys/proc.h> 70 #include <sys/protosw.h> 71 #include <sys/queue.h> 72 #include <sys/systm.h> 73 #include <sys/sysproto.h> 74 #include <sys/sysent.h> 75 #include <sys/file.h> 76 #include <sys/sbuf.h> 77 #include <sys/socket.h> 78 #include <sys/socketvar.h> 79 #include <sys/sysctl.h> 80 81 #include <netinet/in.h> 82 #include <netinet/in_pcb.h> 83 84 #include <vm/vm.h> 85 86 #include <sys/mac_policy.h> 87 88 SYSCTL_DECL(_security_mac); 89 90 SYSCTL_NODE(_security_mac, OID_AUTO, portacl, CTLFLAG_RW, 0, 91 "TrustedBSD mac_portacl policy controls"); 92 93 static int mac_portacl_enabled = 1; 94 SYSCTL_INT(_security_mac_portacl, OID_AUTO, enabled, CTLFLAG_RW, 95 &mac_portacl_enabled, 0, "Enforce portacl policy"); 96 TUNABLE_INT("security.mac.portacl.enabled", &mac_portacl_enabled); 97 98 static int mac_portacl_suser_exempt = 1; 99 SYSCTL_INT(_security_mac_portacl, OID_AUTO, suser_exempt, CTLFLAG_RW, 100 &mac_portacl_suser_exempt, 0, "Privilege permits binding of any port"); 101 TUNABLE_INT("security.mac.portacl.suser_exempt", 102 &mac_portacl_suser_exempt); 103 104 static int mac_portacl_autoport_exempt = 1; 105 SYSCTL_INT(_security_mac_portacl, OID_AUTO, autoport_exempt, CTLFLAG_RW, 106 &mac_portacl_autoport_exempt, 0, "Allow automatic allocation through " 107 "binding port 0 if not IP_PORTRANGELOW"); 108 TUNABLE_INT("security.mac.portacl.autoport_exempt", 109 &mac_portacl_autoport_exempt); 110 111 static int mac_portacl_port_high = 1023; 112 SYSCTL_INT(_security_mac_portacl, OID_AUTO, port_high, CTLFLAG_RW, 113 &mac_portacl_port_high, 0, "Highest port to enforce for"); 114 TUNABLE_INT("security.mac.portacl.port_high", &mac_portacl_port_high); 115 116 MALLOC_DEFINE(M_PORTACL, "portacl rule", "Rules for mac_portacl"); 117 118 #define MAC_RULE_STRING_LEN 1024 119 120 #define RULE_GID 1 121 #define RULE_UID 2 122 #define RULE_PROTO_TCP 1 123 #define RULE_PROTO_UDP 2 124 struct rule { 125 id_t r_id; 126 int r_idtype; 127 u_int16_t r_port; 128 int r_protocol; 129 130 TAILQ_ENTRY(rule) r_entries; 131 }; 132 133 #define GID_STRING "gid" 134 #define TCP_STRING "tcp" 135 #define UID_STRING "uid" 136 #define UDP_STRING "udp" 137 138 /* 139 * Text format for the rule string is that a rule consists of a 140 * comma-seperated list of elements. Each element is in the form 141 * idtype:id:protocol:portnumber, and constitutes granting of permission 142 * for the specified binding. 143 */ 144 145 static struct mtx rule_mtx; 146 static TAILQ_HEAD(rulehead, rule) rule_head; 147 static char rule_string[MAC_RULE_STRING_LEN]; 148 149 static void 150 toast_rules(struct rulehead *head) 151 { 152 struct rule *rule; 153 154 while ((rule = TAILQ_FIRST(head)) != NULL) { 155 TAILQ_REMOVE(head, rule, r_entries); 156 free(rule, M_PORTACL); 157 } 158 } 159 160 /* 161 * Note that there is an inherent race condition in the unload of modules 162 * and access via sysctl. 163 */ 164 static void 165 destroy(struct mac_policy_conf *mpc) 166 { 167 168 mtx_destroy(&rule_mtx); 169 toast_rules(&rule_head); 170 } 171 172 static void 173 init(struct mac_policy_conf *mpc) 174 { 175 176 mtx_init(&rule_mtx, "rule_mtx", NULL, MTX_DEF); 177 TAILQ_INIT(&rule_head); 178 } 179 180 /* 181 * Note: parsing routines are destructive on the passed string. 182 */ 183 static int 184 parse_rule_element(char *element, struct rule **rule) 185 { 186 char *idtype, *id, *protocol, *portnumber, *p; 187 struct rule *new; 188 int error; 189 190 error = 0; 191 new = malloc(sizeof(*new), M_PORTACL, M_ZERO | M_WAITOK); 192 193 idtype = strsep(&element, ":"); 194 if (idtype == NULL) { 195 error = EINVAL; 196 goto out; 197 } 198 id = strsep(&element, ":"); 199 if (id == NULL) { 200 error = EINVAL; 201 goto out; 202 } 203 new->r_id = strtol(id, &p, 10); 204 if (*p != '\0') { 205 error = EINVAL; 206 goto out; 207 } 208 if (strcmp(idtype, UID_STRING) == 0) 209 new->r_idtype = RULE_UID; 210 else if (strcmp(idtype, GID_STRING) == 0) 211 new->r_idtype = RULE_GID; 212 else { 213 error = EINVAL; 214 goto out; 215 } 216 protocol = strsep(&element, ":"); 217 if (protocol == NULL) { 218 error = EINVAL; 219 goto out; 220 } 221 if (strcmp(protocol, TCP_STRING) == 0) 222 new->r_protocol = RULE_PROTO_TCP; 223 else if (strcmp(protocol, UDP_STRING) == 0) 224 new->r_protocol = RULE_PROTO_UDP; 225 else { 226 error = EINVAL; 227 goto out; 228 } 229 portnumber = element; 230 if (portnumber == NULL) { 231 error = EINVAL; 232 goto out; 233 } 234 new->r_port = strtol(portnumber, &p, 10); 235 if (*p != '\0') { 236 error = EINVAL; 237 goto out; 238 } 239 240 out: 241 if (error != 0) { 242 free(new, M_PORTACL); 243 *rule = NULL; 244 } else 245 *rule = new; 246 return (error); 247 } 248 249 static int 250 parse_rules(char *string, struct rulehead *head) 251 { 252 struct rule *new; 253 char *element; 254 int error; 255 256 error = 0; 257 while ((element = strsep(&string, ",")) != NULL) { 258 if (strlen(element) == 0) 259 continue; 260 error = parse_rule_element(element, &new); 261 if (error) 262 goto out; 263 TAILQ_INSERT_TAIL(head, new, r_entries); 264 } 265 out: 266 if (error != 0) 267 toast_rules(head); 268 return (error); 269 } 270 271 /* 272 * rule_printf() and rules_to_string() are unused currently because they rely 273 * on sbufs with auto-extension, which may sleep while holding a mutex. 274 * Instead, the non-canonical user-generated rule string is returned to the 275 * user when the rules are queried, which is faster anyway. 276 */ 277 #if 0 278 static void 279 rule_printf(struct sbuf *sb, struct rule *rule) 280 { 281 const char *idtype, *protocol; 282 283 switch(rule->r_idtype) { 284 case RULE_GID: 285 idtype = GID_STRING; 286 break; 287 case RULE_UID: 288 idtype = UID_STRING; 289 break; 290 default: 291 panic("rule_printf: unknown idtype (%d)\n", rule->r_idtype); 292 } 293 294 switch (rule->r_protocol) { 295 case RULE_PROTO_TCP: 296 protocol = TCP_STRING; 297 break; 298 case RULE_PROTO_UDP: 299 protocol = UDP_STRING; 300 break; 301 default: 302 panic("rule_printf: unknown protocol (%d)\n", 303 rule->r_protocol); 304 } 305 sbuf_printf(sb, "%s:%jd:%s:%d", idtype, (intmax_t)rule->r_id, 306 protocol, rule->r_port); 307 } 308 309 static char * 310 rules_to_string(void) 311 { 312 struct rule *rule; 313 struct sbuf *sb; 314 int needcomma; 315 char *temp; 316 317 sb = sbuf_new(NULL, NULL, 0, SBUF_AUTOEXTEND); 318 needcomma = 0; 319 mtx_lock(&rule_mtx); 320 for (rule = TAILQ_FIRST(&rule_head); rule != NULL; 321 rule = TAILQ_NEXT(rule, r_entries)) { 322 if (!needcomma) 323 needcomma = 1; 324 else 325 sbuf_printf(sb, ","); 326 rule_printf(sb, rule); 327 } 328 mtx_unlock(&rule_mtx); 329 sbuf_finish(sb); 330 temp = strdup(sbuf_data(sb), M_PORTACL); 331 sbuf_delete(sb); 332 return (temp); 333 } 334 #endif 335 336 /* 337 * Note: due to races, there is not a single serializable order 338 * between parallel calls to the sysctl. 339 */ 340 static int 341 sysctl_rules(SYSCTL_HANDLER_ARGS) 342 { 343 char *string, *copy_string, *new_string; 344 struct rulehead head, save_head; 345 int error; 346 347 new_string = NULL; 348 if (req->newptr == NULL) { 349 new_string = malloc(MAC_RULE_STRING_LEN, M_PORTACL, 350 M_WAITOK | M_ZERO); 351 strcpy(new_string, rule_string); 352 string = new_string; 353 } else 354 string = rule_string; 355 356 error = sysctl_handle_string(oidp, string, MAC_RULE_STRING_LEN, req); 357 if (error) 358 goto out; 359 360 if (req->newptr != NULL) { 361 copy_string = strdup(string, M_PORTACL); 362 TAILQ_INIT(&head); 363 error = parse_rules(copy_string, &head); 364 free(copy_string, M_PORTACL); 365 if (error) 366 goto out; 367 368 TAILQ_INIT(&save_head); 369 mtx_lock(&rule_mtx); 370 TAILQ_CONCAT(&save_head, &rule_head, r_entries); 371 TAILQ_CONCAT(&rule_head, &head, r_entries); 372 strcpy(rule_string, string); 373 mtx_unlock(&rule_mtx); 374 toast_rules(&save_head); 375 } 376 out: 377 if (new_string != NULL) 378 free(new_string, M_PORTACL); 379 return (error); 380 } 381 382 SYSCTL_PROC(_security_mac_portacl, OID_AUTO, rules, 383 CTLTYPE_STRING|CTLFLAG_RW, 0, 0, sysctl_rules, "A", "Rules"); 384 385 static int 386 rules_check(struct ucred *cred, int family, int type, u_int16_t port) 387 { 388 struct rule *rule; 389 int error; 390 391 #if 0 392 printf("Check requested for euid %d, family %d, type %d, port %d\n", 393 cred->cr_uid, family, type, port); 394 #endif 395 396 if (port > mac_portacl_port_high) 397 return (0); 398 399 error = EPERM; 400 mtx_lock(&rule_mtx); 401 for (rule = TAILQ_FIRST(&rule_head); 402 rule != NULL; 403 rule = TAILQ_NEXT(rule, r_entries)) { 404 if (type == SOCK_DGRAM && rule->r_protocol != RULE_PROTO_UDP) 405 continue; 406 if (type == SOCK_STREAM && rule->r_protocol != RULE_PROTO_TCP) 407 continue; 408 if (port != rule->r_port) 409 continue; 410 if (rule->r_idtype == RULE_UID) { 411 if (cred->cr_uid == rule->r_id) { 412 error = 0; 413 break; 414 } 415 } else if (rule->r_idtype == RULE_GID) { 416 if (cred->cr_gid == rule->r_id) { 417 error = 0; 418 break; 419 } else if (groupmember(rule->r_id, cred)) { 420 error = 0; 421 break; 422 } 423 } else 424 panic("rules_check: unknown rule type %d", 425 rule->r_idtype); 426 } 427 mtx_unlock(&rule_mtx); 428 429 if (error != 0 && mac_portacl_suser_exempt != 0) 430 error = suser_cred(cred, 0); 431 432 return (error); 433 } 434 435 /* 436 * Note, this only limits the ability to explicitly bind a port, it 437 * doesn't limit implicitly bound ports for outgoing connections where 438 * the source port is left up to the IP stack to determine automatically. 439 */ 440 static int 441 check_socket_bind(struct ucred *cred, struct socket *so, 442 struct label *socketlabel, struct sockaddr *sockaddr) 443 { 444 struct sockaddr_in *sin; 445 struct inpcb *inp; 446 int family, type; 447 u_int16_t port; 448 449 /* Only run if we are enabled. */ 450 if (mac_portacl_enabled == 0) 451 return (0); 452 453 /* Only interested in IPv4 and IPv6 sockets. */ 454 if (so->so_proto->pr_domain->dom_family != PF_INET && 455 so->so_proto->pr_domain->dom_family != PF_INET6) 456 return (0); 457 458 /* Currently, we don't attempt to deal with SOCK_RAW, etc. */ 459 if (so->so_type != SOCK_DGRAM && 460 so->so_type != SOCK_STREAM) 461 return (0); 462 463 /* Reject addresses we don't understand; fail closed. */ 464 if (sockaddr->sa_family != AF_INET && 465 sockaddr->sa_family != AF_INET6) 466 return (EINVAL); 467 468 family = so->so_proto->pr_domain->dom_family; 469 type = so->so_type; 470 sin = (struct sockaddr_in *) sockaddr; 471 port = ntohs(sin->sin_port); 472 473 /* 474 * Sockets are frequently bound with a specific IP address but a port 475 * number of '0' to request automatic port allocation. This is often 476 * desirable as long as IP_PORTRANGELOW isn't set, which might permit 477 * automatic allocation of a "privileged" port. The autoport exempt 478 * flag exempts port 0 allocation from rule checking as long as a low 479 * port isn't required. 480 */ 481 if (mac_portacl_autoport_exempt && port == 0) { 482 inp = sotoinpcb(so); 483 if ((inp->inp_flags & INP_LOWPORT) == 0) 484 return (0); 485 } 486 487 return (rules_check(cred, family, type, port)); 488 } 489 490 static struct mac_policy_ops mac_portacl_ops = 491 { 492 .mpo_destroy = destroy, 493 .mpo_init = init, 494 .mpo_check_socket_bind = check_socket_bind, 495 }; 496 497 MAC_POLICY_SET(&mac_portacl_ops, trustedbsd_mac_portacl, 498 "TrustedBSD MAC/portacl", MPC_LOADTIME_FLAG_UNLOADOK, NULL); 499