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/param.h> 59 #include <sys/domain.h> 60 #include <sys/kernel.h> 61 #include <sys/lock.h> 62 #include <sys/malloc.h> 63 #include <sys/module.h> 64 #include <sys/mutex.h> 65 #include <sys/priv.h> 66 #include <sys/proc.h> 67 #include <sys/protosw.h> 68 #include <sys/queue.h> 69 #include <sys/systm.h> 70 #include <sys/sbuf.h> 71 #include <sys/socket.h> 72 #include <sys/socketvar.h> 73 #include <sys/sysctl.h> 74 75 #include <netinet/in.h> 76 #include <netinet/in_pcb.h> 77 78 #include <security/mac/mac_policy.h> 79 80 SYSCTL_DECL(_security_mac); 81 82 SYSCTL_NODE(_security_mac, OID_AUTO, portacl, CTLFLAG_RW, 0, 83 "TrustedBSD mac_portacl policy controls"); 84 85 static int mac_portacl_enabled = 1; 86 SYSCTL_INT(_security_mac_portacl, OID_AUTO, enabled, CTLFLAG_RW, 87 &mac_portacl_enabled, 0, "Enforce portacl policy"); 88 TUNABLE_INT("security.mac.portacl.enabled", &mac_portacl_enabled); 89 90 static int mac_portacl_suser_exempt = 1; 91 SYSCTL_INT(_security_mac_portacl, OID_AUTO, suser_exempt, CTLFLAG_RW, 92 &mac_portacl_suser_exempt, 0, "Privilege permits binding of any port"); 93 TUNABLE_INT("security.mac.portacl.suser_exempt", 94 &mac_portacl_suser_exempt); 95 96 static int mac_portacl_autoport_exempt = 1; 97 SYSCTL_INT(_security_mac_portacl, OID_AUTO, autoport_exempt, CTLFLAG_RW, 98 &mac_portacl_autoport_exempt, 0, "Allow automatic allocation through " 99 "binding port 0 if not IP_PORTRANGELOW"); 100 TUNABLE_INT("security.mac.portacl.autoport_exempt", 101 &mac_portacl_autoport_exempt); 102 103 static int mac_portacl_port_high = 1023; 104 SYSCTL_INT(_security_mac_portacl, OID_AUTO, port_high, CTLFLAG_RW, 105 &mac_portacl_port_high, 0, "Highest port to enforce for"); 106 TUNABLE_INT("security.mac.portacl.port_high", &mac_portacl_port_high); 107 108 MALLOC_DEFINE(M_PORTACL, "mac_portacl_rule", "Rules for mac_portacl"); 109 110 #define MAC_RULE_STRING_LEN 1024 111 112 #define RULE_GID 1 113 #define RULE_UID 2 114 #define RULE_PROTO_TCP 1 115 #define RULE_PROTO_UDP 2 116 struct rule { 117 id_t r_id; 118 int r_idtype; 119 u_int16_t r_port; 120 int r_protocol; 121 122 TAILQ_ENTRY(rule) r_entries; 123 }; 124 125 #define GID_STRING "gid" 126 #define TCP_STRING "tcp" 127 #define UID_STRING "uid" 128 #define UDP_STRING "udp" 129 130 /* 131 * Text format for the rule string is that a rule consists of a 132 * comma-seperated list of elements. Each element is in the form 133 * idtype:id:protocol:portnumber, and constitutes granting of permission 134 * for the specified binding. 135 */ 136 137 static struct mtx rule_mtx; 138 static TAILQ_HEAD(rulehead, rule) rule_head; 139 static char rule_string[MAC_RULE_STRING_LEN]; 140 141 static void 142 toast_rules(struct rulehead *head) 143 { 144 struct rule *rule; 145 146 while ((rule = TAILQ_FIRST(head)) != NULL) { 147 TAILQ_REMOVE(head, rule, r_entries); 148 free(rule, M_PORTACL); 149 } 150 } 151 152 /* 153 * Note that there is an inherent race condition in the unload of modules 154 * and access via sysctl. 155 */ 156 static void 157 destroy(struct mac_policy_conf *mpc) 158 { 159 160 mtx_destroy(&rule_mtx); 161 toast_rules(&rule_head); 162 } 163 164 static void 165 init(struct mac_policy_conf *mpc) 166 { 167 168 mtx_init(&rule_mtx, "rule_mtx", NULL, MTX_DEF); 169 TAILQ_INIT(&rule_head); 170 } 171 172 /* 173 * Note: parsing routines are destructive on the passed string. 174 */ 175 static int 176 parse_rule_element(char *element, struct rule **rule) 177 { 178 char *idtype, *id, *protocol, *portnumber, *p; 179 struct rule *new; 180 int error; 181 182 error = 0; 183 new = malloc(sizeof(*new), M_PORTACL, M_ZERO | M_WAITOK); 184 185 idtype = strsep(&element, ":"); 186 if (idtype == NULL) { 187 error = EINVAL; 188 goto out; 189 } 190 id = strsep(&element, ":"); 191 if (id == NULL) { 192 error = EINVAL; 193 goto out; 194 } 195 new->r_id = strtol(id, &p, 10); 196 if (*p != '\0') { 197 error = EINVAL; 198 goto out; 199 } 200 if (strcmp(idtype, UID_STRING) == 0) 201 new->r_idtype = RULE_UID; 202 else if (strcmp(idtype, GID_STRING) == 0) 203 new->r_idtype = RULE_GID; 204 else { 205 error = EINVAL; 206 goto out; 207 } 208 protocol = strsep(&element, ":"); 209 if (protocol == NULL) { 210 error = EINVAL; 211 goto out; 212 } 213 if (strcmp(protocol, TCP_STRING) == 0) 214 new->r_protocol = RULE_PROTO_TCP; 215 else if (strcmp(protocol, UDP_STRING) == 0) 216 new->r_protocol = RULE_PROTO_UDP; 217 else { 218 error = EINVAL; 219 goto out; 220 } 221 portnumber = element; 222 if (portnumber == NULL) { 223 error = EINVAL; 224 goto out; 225 } 226 new->r_port = strtol(portnumber, &p, 10); 227 if (*p != '\0') { 228 error = EINVAL; 229 goto out; 230 } 231 232 out: 233 if (error != 0) { 234 free(new, M_PORTACL); 235 *rule = NULL; 236 } else 237 *rule = new; 238 return (error); 239 } 240 241 static int 242 parse_rules(char *string, struct rulehead *head) 243 { 244 struct rule *new; 245 char *element; 246 int error; 247 248 error = 0; 249 while ((element = strsep(&string, ",")) != NULL) { 250 if (strlen(element) == 0) 251 continue; 252 error = parse_rule_element(element, &new); 253 if (error) 254 goto out; 255 TAILQ_INSERT_TAIL(head, new, r_entries); 256 } 257 out: 258 if (error != 0) 259 toast_rules(head); 260 return (error); 261 } 262 263 /* 264 * rule_printf() and rules_to_string() are unused currently because they rely 265 * on sbufs with auto-extension, which may sleep while holding a mutex. 266 * Instead, the non-canonical user-generated rule string is returned to the 267 * user when the rules are queried, which is faster anyway. 268 */ 269 #if 0 270 static void 271 rule_printf(struct sbuf *sb, struct rule *rule) 272 { 273 const char *idtype, *protocol; 274 275 switch(rule->r_idtype) { 276 case RULE_GID: 277 idtype = GID_STRING; 278 break; 279 case RULE_UID: 280 idtype = UID_STRING; 281 break; 282 default: 283 panic("rule_printf: unknown idtype (%d)\n", rule->r_idtype); 284 } 285 286 switch (rule->r_protocol) { 287 case RULE_PROTO_TCP: 288 protocol = TCP_STRING; 289 break; 290 case RULE_PROTO_UDP: 291 protocol = UDP_STRING; 292 break; 293 default: 294 panic("rule_printf: unknown protocol (%d)\n", 295 rule->r_protocol); 296 } 297 sbuf_printf(sb, "%s:%jd:%s:%d", idtype, (intmax_t)rule->r_id, 298 protocol, rule->r_port); 299 } 300 301 static char * 302 rules_to_string(void) 303 { 304 struct rule *rule; 305 struct sbuf *sb; 306 int needcomma; 307 char *temp; 308 309 sb = sbuf_new(NULL, NULL, 0, SBUF_AUTOEXTEND); 310 needcomma = 0; 311 mtx_lock(&rule_mtx); 312 for (rule = TAILQ_FIRST(&rule_head); rule != NULL; 313 rule = TAILQ_NEXT(rule, r_entries)) { 314 if (!needcomma) 315 needcomma = 1; 316 else 317 sbuf_printf(sb, ","); 318 rule_printf(sb, rule); 319 } 320 mtx_unlock(&rule_mtx); 321 sbuf_finish(sb); 322 temp = strdup(sbuf_data(sb), M_PORTACL); 323 sbuf_delete(sb); 324 return (temp); 325 } 326 #endif 327 328 /* 329 * Note: due to races, there is not a single serializable order 330 * between parallel calls to the sysctl. 331 */ 332 static int 333 sysctl_rules(SYSCTL_HANDLER_ARGS) 334 { 335 char *string, *copy_string, *new_string; 336 struct rulehead head, save_head; 337 int error; 338 339 new_string = NULL; 340 if (req->newptr == NULL) { 341 new_string = malloc(MAC_RULE_STRING_LEN, M_PORTACL, 342 M_WAITOK | M_ZERO); 343 strcpy(new_string, rule_string); 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 > mac_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 && mac_portacl_suser_exempt != 0) 422 error = priv_check_cred(cred, PRIV_NETINET_RESERVEDPORT, 423 SUSER_ALLOWJAIL); 424 425 return (error); 426 } 427 428 /* 429 * Note, this only limits the ability to explicitly bind a port, it 430 * doesn't limit implicitly bound ports for outgoing connections where 431 * the source port is left up to the IP stack to determine automatically. 432 */ 433 static int 434 check_socket_bind(struct ucred *cred, struct socket *so, 435 struct label *socketlabel, struct sockaddr *sockaddr) 436 { 437 struct sockaddr_in *sin; 438 struct inpcb *inp; 439 int family, type; 440 u_int16_t port; 441 442 /* Only run if we are enabled. */ 443 if (mac_portacl_enabled == 0) 444 return (0); 445 446 /* Only interested in IPv4 and IPv6 sockets. */ 447 if (so->so_proto->pr_domain->dom_family != PF_INET && 448 so->so_proto->pr_domain->dom_family != PF_INET6) 449 return (0); 450 451 /* Currently, we don't attempt to deal with SOCK_RAW, etc. */ 452 if (so->so_type != SOCK_DGRAM && 453 so->so_type != SOCK_STREAM) 454 return (0); 455 456 /* Reject addresses we don't understand; fail closed. */ 457 if (sockaddr->sa_family != AF_INET && 458 sockaddr->sa_family != AF_INET6) 459 return (EINVAL); 460 461 family = so->so_proto->pr_domain->dom_family; 462 type = so->so_type; 463 sin = (struct sockaddr_in *) sockaddr; 464 port = ntohs(sin->sin_port); 465 466 /* 467 * Sockets are frequently bound with a specific IP address but a port 468 * number of '0' to request automatic port allocation. This is often 469 * desirable as long as IP_PORTRANGELOW isn't set, which might permit 470 * automatic allocation of a "privileged" port. The autoport exempt 471 * flag exempts port 0 allocation from rule checking as long as a low 472 * port isn't required. 473 */ 474 if (mac_portacl_autoport_exempt && port == 0) { 475 inp = sotoinpcb(so); 476 if ((inp->inp_flags & INP_LOWPORT) == 0) 477 return (0); 478 } 479 480 return (rules_check(cred, family, type, port)); 481 } 482 483 static struct mac_policy_ops mac_portacl_ops = 484 { 485 .mpo_destroy = destroy, 486 .mpo_init = init, 487 .mpo_check_socket_bind = check_socket_bind, 488 }; 489 490 MAC_POLICY_SET(&mac_portacl_ops, trustedbsd_mac_portacl, 491 "TrustedBSD MAC/portacl", MPC_LOADTIME_FLAG_UNLOADOK, NULL); 492