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/mac.h> 65 #include <sys/malloc.h> 66 #include <sys/mount.h> 67 #include <sys/proc.h> 68 #include <sys/protosw.h> 69 #include <sys/queue.h> 70 #include <sys/systm.h> 71 #include <sys/sysproto.h> 72 #include <sys/sysent.h> 73 #include <sys/vnode.h> 74 #include <sys/file.h> 75 #include <sys/sbuf.h> 76 #include <sys/socket.h> 77 #include <sys/socketvar.h> 78 #include <sys/sx.h> 79 #include <sys/sysctl.h> 80 81 #include <netinet/in.h> 82 83 #include <vm/vm.h> 84 85 #include <sys/mac_policy.h> 86 87 SYSCTL_DECL(_security_mac); 88 89 SYSCTL_NODE(_security_mac, OID_AUTO, portacl, CTLFLAG_RW, 0, 90 "TrustedBSD mac_portacl policy controls"); 91 92 static int mac_portacl_enabled = 1; 93 SYSCTL_INT(_security_mac_portacl, OID_AUTO, enabled, CTLFLAG_RW, 94 &mac_portacl_enabled, 0, "Enforce portacl policy"); 95 TUNABLE_INT("security.mac.portacl.enabled", &mac_portacl_enabled); 96 97 static int mac_portacl_suser_exempt = 1; 98 SYSCTL_INT(_security_mac_portacl, OID_AUTO, suser_exempt, CTLFLAG_RW, 99 &mac_portacl_suser_exempt, 0, "Privilege permits binding of any port"); 100 TUNABLE_INT("security.mac.portacl.suser_exempt", 101 &mac_portacl_suser_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, "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 sx rule_sx; 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 sx_destroy(&rule_sx); 161 toast_rules(&rule_head); 162 } 163 164 static void 165 init(struct mac_policy_conf *mpc) 166 { 167 168 sx_init(&rule_sx, "rule_sx"); 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 #if 0 264 static void 265 rule_printf(struct sbuf *sb, struct rule *rule) 266 { 267 const char *idtype, *protocol; 268 269 switch(rule->r_idtype) { 270 case RULE_GID: 271 idtype = GID_STRING; 272 break; 273 case RULE_UID: 274 idtype = UID_STRING; 275 break; 276 default: 277 panic("rule_printf: unknown idtype (%d)\n", rule->r_idtype); 278 } 279 280 switch (rule->r_protocol) { 281 case RULE_PROTO_TCP: 282 protocol = TCP_STRING; 283 break; 284 case RULE_PROTO_UDP: 285 protocol = UDP_STRING; 286 break; 287 default: 288 panic("rule_printf: unknown protocol (%d)\n", 289 rule->r_protocol); 290 } 291 sbuf_printf(sb, "%s:%jd:%s:%d", idtype, (intmax_t)rule->r_id, 292 protocol, rule->r_port); 293 } 294 295 static char * 296 rules_to_string(void) 297 { 298 struct rule *rule; 299 struct sbuf *sb; 300 int needcomma; 301 char *temp; 302 303 sb = sbuf_new(NULL, NULL, 0, SBUF_AUTOEXTEND); 304 needcomma = 0; 305 sx_slock(&rule_sx); 306 for (rule = TAILQ_FIRST(&rule_head); rule != NULL; 307 rule = TAILQ_NEXT(rule, r_entries)) { 308 if (!needcomma) 309 needcomma = 1; 310 else 311 sbuf_printf(sb, ","); 312 rule_printf(sb, rule); 313 } 314 sx_sunlock(&rule_sx); 315 sbuf_finish(sb); 316 temp = strdup(sbuf_data(sb), M_PORTACL); 317 sbuf_delete(sb); 318 return (temp); 319 } 320 #endif 321 322 /* 323 * Note: due to races, there is not a single serializable order 324 * between parallel calls to the sysctl. 325 */ 326 static int 327 sysctl_rules(SYSCTL_HANDLER_ARGS) 328 { 329 char *string, *copy_string, *new_string; 330 struct rulehead head, save_head; 331 struct rule *rule; 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 strcpy(new_string, rule_string); 339 string = new_string; 340 } else 341 string = rule_string; 342 343 error = sysctl_handle_string(oidp, string, MAC_RULE_STRING_LEN, req); 344 if (error) 345 goto out; 346 347 if (req->newptr != NULL) { 348 copy_string = strdup(string, M_PORTACL); 349 TAILQ_INIT(&head); 350 error = parse_rules(copy_string, &head); 351 free(copy_string, M_PORTACL); 352 if (error) 353 goto out; 354 355 TAILQ_INIT(&save_head); 356 sx_xlock(&rule_sx); 357 /* 358 * XXX: Unfortunately, TAILQ doesn't yet have a supported 359 * assignment operator to copy one queue to another, due 360 * to a self-referential pointer in the tailq header. 361 * For now, do it the old-fashioned way. 362 */ 363 while ((rule = TAILQ_FIRST(&rule_head)) != NULL) { 364 TAILQ_REMOVE(&rule_head, rule, r_entries); 365 TAILQ_INSERT_HEAD(&save_head, rule, r_entries); 366 } 367 while ((rule = TAILQ_FIRST(&head)) != NULL) { 368 TAILQ_REMOVE(&head, rule, r_entries); 369 TAILQ_INSERT_HEAD(&rule_head, rule, r_entries); 370 } 371 strcpy(rule_string, string); 372 sx_xunlock(&rule_sx); 373 toast_rules(&save_head); 374 } 375 out: 376 if (new_string != NULL) 377 free(new_string, M_PORTACL); 378 return (error); 379 } 380 381 SYSCTL_PROC(_security_mac_portacl, OID_AUTO, rules, 382 CTLTYPE_STRING|CTLFLAG_RW, 0, 0, sysctl_rules, "A", "Rules"); 383 384 static int 385 rules_check(struct ucred *cred, int family, int type, u_int16_t port) 386 { 387 struct rule *rule; 388 int error; 389 390 #if 0 391 printf("Check requested for euid %d, family %d, type %d, port %d\n", 392 cred->cr_uid, family, type, port); 393 #endif 394 395 if (port > mac_portacl_port_high) 396 return (0); 397 398 error = EPERM; 399 sx_slock(&rule_sx); 400 for (rule = TAILQ_FIRST(&rule_head); 401 rule != NULL; 402 rule = TAILQ_NEXT(rule, r_entries)) { 403 if (type == SOCK_DGRAM && rule->r_protocol != RULE_PROTO_UDP) 404 continue; 405 if (type == SOCK_STREAM && rule->r_protocol != RULE_PROTO_TCP) 406 continue; 407 if (port != rule->r_port) 408 continue; 409 if (rule->r_idtype == RULE_UID) { 410 if (cred->cr_uid == rule->r_id) { 411 error = 0; 412 break; 413 } 414 } else if (rule->r_idtype == RULE_GID) { 415 if (cred->cr_gid == rule->r_id) { 416 error = 0; 417 break; 418 } else if (groupmember(rule->r_id, cred)) { 419 error = 0; 420 break; 421 } 422 } else 423 panic("rules_check: unknown rule type %d", 424 rule->r_idtype); 425 } 426 sx_sunlock(&rule_sx); 427 428 if (error != 0 && mac_portacl_suser_exempt != 0) 429 error = suser_cred(cred, 0); 430 431 return (error); 432 } 433 434 /* 435 * Note, this only limits the ability to explicitly bind a port, it 436 * doesn't limit implicitly bound ports for outgoing connections where 437 * the source port is left up to the IP stack to determine automatically. 438 */ 439 static int 440 check_socket_bind(struct ucred *cred, struct socket *so, 441 struct label *socketlabel, struct sockaddr *sockaddr) 442 { 443 struct sockaddr_in *sin; 444 int family, type; 445 u_int16_t port; 446 447 /* Only run if we are enabled. */ 448 if (mac_portacl_enabled == 0) 449 return (0); 450 451 /* Only interested in IPv4 and IPv6 sockets. */ 452 if (so->so_proto->pr_domain->dom_family != PF_INET && 453 so->so_proto->pr_domain->dom_family != PF_INET6) 454 return (0); 455 456 /* Currently, we don't attempt to deal with SOCK_RAW, etc. */ 457 if (so->so_type != SOCK_DGRAM && 458 so->so_type != SOCK_STREAM) 459 return (0); 460 461 /* Reject addresses we don't understand; fail closed. */ 462 if (sockaddr->sa_family != AF_INET && 463 sockaddr->sa_family != AF_INET6) 464 return (EINVAL); 465 466 family = so->so_proto->pr_domain->dom_family; 467 type = so->so_type; 468 sin = (struct sockaddr_in *) sockaddr; 469 port = ntohs(sin->sin_port); 470 471 return (rules_check(cred, family, type, port)); 472 } 473 474 static struct mac_policy_ops mac_portacl_ops = 475 { 476 .mpo_destroy = destroy, 477 .mpo_init = init, 478 .mpo_check_socket_bind = check_socket_bind, 479 }; 480 481 MAC_POLICY_SET(&mac_portacl_ops, trustedbsd_mac_portacl, 482 "TrustedBSD MAC/portacl", MPC_LOADTIME_FLAG_UNLOADOK, NULL); 483