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