1 /*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <errno.h>
18 #include <stdio.h>
19 #include <stdlib.h>
20 #include <string.h>
21
22 #define LOG_TAG "FirewallController"
23 #define LOG_NDEBUG 0
24
25 #include <android-base/stringprintf.h>
26 #include <cutils/log.h>
27
28 #include "NetdConstants.h"
29 #include "FirewallController.h"
30
31 using android::base::StringAppendF;
32
33 auto FirewallController::execIptables = ::execIptables;
34 auto FirewallController::execIptablesSilently = ::execIptables;
35 auto FirewallController::execIptablesRestore = ::execIptablesRestore;
36
37 const char* FirewallController::TABLE = "filter";
38
39 const char* FirewallController::LOCAL_INPUT = "fw_INPUT";
40 const char* FirewallController::LOCAL_OUTPUT = "fw_OUTPUT";
41 const char* FirewallController::LOCAL_FORWARD = "fw_FORWARD";
42
43 const char* FirewallController::LOCAL_DOZABLE = "fw_dozable";
44 const char* FirewallController::LOCAL_STANDBY = "fw_standby";
45 const char* FirewallController::LOCAL_POWERSAVE = "fw_powersave";
46
47 // ICMPv6 types that are required for any form of IPv6 connectivity to work. Note that because the
48 // fw_dozable chain is called from both INPUT and OUTPUT, this includes both packets that we need
49 // to be able to send (e.g., RS, NS), and packets that we need to receive (e.g., RA, NA).
50 const char* FirewallController::ICMPV6_TYPES[] = {
51 "packet-too-big",
52 "router-solicitation",
53 "router-advertisement",
54 "neighbour-solicitation",
55 "neighbour-advertisement",
56 "redirect",
57 };
58
FirewallController(void)59 FirewallController::FirewallController(void) {
60 // If no rules are set, it's in BLACKLIST mode
61 mFirewallType = BLACKLIST;
62 }
63
setupIptablesHooks(void)64 int FirewallController::setupIptablesHooks(void) {
65 int res = 0;
66 // child chains are created but not attached, they will be attached explicitly.
67 FirewallType firewallType = getFirewallType(DOZABLE);
68 res |= createChain(LOCAL_DOZABLE, LOCAL_INPUT, firewallType);
69
70 firewallType = getFirewallType(STANDBY);
71 res |= createChain(LOCAL_STANDBY, LOCAL_INPUT, firewallType);
72
73 firewallType = getFirewallType(POWERSAVE);
74 res |= createChain(LOCAL_POWERSAVE, LOCAL_INPUT, firewallType);
75
76 return res;
77 }
78
enableFirewall(FirewallType ftype)79 int FirewallController::enableFirewall(FirewallType ftype) {
80 int res = 0;
81 if (mFirewallType != ftype) {
82 // flush any existing rules
83 disableFirewall();
84
85 if (ftype == WHITELIST) {
86 // create default rule to drop all traffic
87 res |= execIptables(V4V6, "-A", LOCAL_INPUT, "-j", "DROP", NULL);
88 res |= execIptables(V4V6, "-A", LOCAL_OUTPUT, "-j", "REJECT", NULL);
89 res |= execIptables(V4V6, "-A", LOCAL_FORWARD, "-j", "REJECT", NULL);
90 }
91
92 // Set this after calling disableFirewall(), since it defaults to WHITELIST there
93 mFirewallType = ftype;
94 }
95 return res;
96 }
97
disableFirewall(void)98 int FirewallController::disableFirewall(void) {
99 int res = 0;
100
101 mFirewallType = WHITELIST;
102
103 // flush any existing rules
104 res |= execIptables(V4V6, "-F", LOCAL_INPUT, NULL);
105 res |= execIptables(V4V6, "-F", LOCAL_OUTPUT, NULL);
106 res |= execIptables(V4V6, "-F", LOCAL_FORWARD, NULL);
107
108 return res;
109 }
110
enableChildChains(ChildChain chain,bool enable)111 int FirewallController::enableChildChains(ChildChain chain, bool enable) {
112 int res = 0;
113 const char* name;
114 switch(chain) {
115 case DOZABLE:
116 name = LOCAL_DOZABLE;
117 break;
118 case STANDBY:
119 name = LOCAL_STANDBY;
120 break;
121 case POWERSAVE:
122 name = LOCAL_POWERSAVE;
123 break;
124 default:
125 return res;
126 }
127
128 if (enable) {
129 res |= attachChain(name, LOCAL_INPUT);
130 res |= attachChain(name, LOCAL_OUTPUT);
131 } else {
132 res |= detachChain(name, LOCAL_INPUT);
133 res |= detachChain(name, LOCAL_OUTPUT);
134 }
135 return res;
136 }
137
isFirewallEnabled(void)138 int FirewallController::isFirewallEnabled(void) {
139 // TODO: verify that rules are still in place near top
140 return -1;
141 }
142
setInterfaceRule(const char * iface,FirewallRule rule)143 int FirewallController::setInterfaceRule(const char* iface, FirewallRule rule) {
144 if (mFirewallType == BLACKLIST) {
145 // Unsupported in BLACKLIST mode
146 return -1;
147 }
148
149 if (!isIfaceName(iface)) {
150 errno = ENOENT;
151 return -1;
152 }
153
154 const char* op;
155 if (rule == ALLOW) {
156 op = "-I";
157 } else {
158 op = "-D";
159 }
160
161 int res = 0;
162 res |= execIptables(V4V6, op, LOCAL_INPUT, "-i", iface, "-j", "RETURN", NULL);
163 res |= execIptables(V4V6, op, LOCAL_OUTPUT, "-o", iface, "-j", "RETURN", NULL);
164 return res;
165 }
166
setEgressSourceRule(const char * addr,FirewallRule rule)167 int FirewallController::setEgressSourceRule(const char* addr, FirewallRule rule) {
168 if (mFirewallType == BLACKLIST) {
169 // Unsupported in BLACKLIST mode
170 return -1;
171 }
172
173 IptablesTarget target = V4;
174 if (strchr(addr, ':')) {
175 target = V6;
176 }
177
178 const char* op;
179 if (rule == ALLOW) {
180 op = "-I";
181 } else {
182 op = "-D";
183 }
184
185 int res = 0;
186 res |= execIptables(target, op, LOCAL_INPUT, "-d", addr, "-j", "RETURN", NULL);
187 res |= execIptables(target, op, LOCAL_OUTPUT, "-s", addr, "-j", "RETURN", NULL);
188 return res;
189 }
190
setEgressDestRule(const char * addr,int protocol,int port,FirewallRule rule)191 int FirewallController::setEgressDestRule(const char* addr, int protocol, int port,
192 FirewallRule rule) {
193 if (mFirewallType == BLACKLIST) {
194 // Unsupported in BLACKLIST mode
195 return -1;
196 }
197
198 IptablesTarget target = V4;
199 if (strchr(addr, ':')) {
200 target = V6;
201 }
202
203 char protocolStr[16];
204 sprintf(protocolStr, "%d", protocol);
205
206 char portStr[16];
207 sprintf(portStr, "%d", port);
208
209 const char* op;
210 if (rule == ALLOW) {
211 op = "-I";
212 } else {
213 op = "-D";
214 }
215
216 int res = 0;
217 res |= execIptables(target, op, LOCAL_INPUT, "-s", addr, "-p", protocolStr,
218 "--sport", portStr, "-j", "RETURN", NULL);
219 res |= execIptables(target, op, LOCAL_OUTPUT, "-d", addr, "-p", protocolStr,
220 "--dport", portStr, "-j", "RETURN", NULL);
221 return res;
222 }
223
getFirewallType(ChildChain chain)224 FirewallType FirewallController::getFirewallType(ChildChain chain) {
225 switch(chain) {
226 case DOZABLE:
227 return WHITELIST;
228 case STANDBY:
229 return BLACKLIST;
230 case POWERSAVE:
231 return WHITELIST;
232 case NONE:
233 return mFirewallType;
234 default:
235 return BLACKLIST;
236 }
237 }
238
setUidRule(ChildChain chain,int uid,FirewallRule rule)239 int FirewallController::setUidRule(ChildChain chain, int uid, FirewallRule rule) {
240 char uidStr[16];
241 sprintf(uidStr, "%d", uid);
242
243 const char* op;
244 const char* target;
245 FirewallType firewallType = getFirewallType(chain);
246 if (firewallType == WHITELIST) {
247 target = "RETURN";
248 // When adding, insert RETURN rules at the front, before the catch-all DROP at the end.
249 op = (rule == ALLOW)? "-I" : "-D";
250 } else { // BLACKLIST mode
251 target = "DROP";
252 // When adding, append DROP rules at the end, after the RETURN rule that matches TCP RSTs.
253 op = (rule == DENY)? "-A" : "-D";
254 }
255
256 int res = 0;
257 switch(chain) {
258 case DOZABLE:
259 res |= execIptables(V4V6, op, LOCAL_DOZABLE, "-m", "owner", "--uid-owner",
260 uidStr, "-j", target, NULL);
261 break;
262 case STANDBY:
263 res |= execIptables(V4V6, op, LOCAL_STANDBY, "-m", "owner", "--uid-owner",
264 uidStr, "-j", target, NULL);
265 break;
266 case POWERSAVE:
267 res |= execIptables(V4V6, op, LOCAL_POWERSAVE, "-m", "owner", "--uid-owner",
268 uidStr, "-j", target, NULL);
269 break;
270 case NONE:
271 res |= execIptables(V4V6, op, LOCAL_INPUT, "-m", "owner", "--uid-owner", uidStr,
272 "-j", target, NULL);
273 res |= execIptables(V4V6, op, LOCAL_OUTPUT, "-m", "owner", "--uid-owner", uidStr,
274 "-j", target, NULL);
275 break;
276 default:
277 ALOGW("Unknown child chain: %d", chain);
278 break;
279 }
280 return res;
281 }
282
attachChain(const char * childChain,const char * parentChain)283 int FirewallController::attachChain(const char* childChain, const char* parentChain) {
284 return execIptables(V4V6, "-t", TABLE, "-A", parentChain, "-j", childChain, NULL);
285 }
286
detachChain(const char * childChain,const char * parentChain)287 int FirewallController::detachChain(const char* childChain, const char* parentChain) {
288 return execIptables(V4V6, "-t", TABLE, "-D", parentChain, "-j", childChain, NULL);
289 }
290
createChain(const char * childChain,const char * parentChain,FirewallType type)291 int FirewallController::createChain(const char* childChain,
292 const char* parentChain, FirewallType type) {
293 execIptablesSilently(V4V6, "-t", TABLE, "-D", parentChain, "-j", childChain, NULL);
294 std::vector<int32_t> uids;
295 return replaceUidChain(childChain, type == WHITELIST, uids);
296 }
297
makeUidRules(IptablesTarget target,const char * name,bool isWhitelist,const std::vector<int32_t> & uids)298 std::string FirewallController::makeUidRules(IptablesTarget target, const char *name,
299 bool isWhitelist, const std::vector<int32_t>& uids) {
300 std::string commands;
301 StringAppendF(&commands, "*filter\n:%s -\n", name);
302
303 // Allow TCP RSTs so we can cleanly close TCP connections of apps that no longer have network
304 // access. Both incoming and outgoing RSTs are allowed.
305 StringAppendF(&commands, "-A %s -p tcp --tcp-flags RST RST -j RETURN\n", name);
306
307 if (isWhitelist) {
308 // Allow ICMPv6 packets necessary to make IPv6 connectivity work. http://b/23158230 .
309 if (target == V6) {
310 for (size_t i = 0; i < ARRAY_SIZE(ICMPV6_TYPES); i++) {
311 StringAppendF(&commands, "-A %s -p icmpv6 --icmpv6-type %s -j RETURN\n",
312 name, ICMPV6_TYPES[i]);
313 }
314 }
315
316 // Always whitelist system UIDs.
317 StringAppendF(&commands,
318 "-A %s -m owner --uid-owner %d-%d -j RETURN\n", name, 0, MAX_SYSTEM_UID);
319 }
320
321 // Whitelist or blacklist the specified UIDs.
322 const char *action = isWhitelist ? "RETURN" : "DROP";
323 for (auto uid : uids) {
324 StringAppendF(&commands, "-A %s -m owner --uid-owner %d -j %s\n", name, uid, action);
325 }
326
327 // If it's a whitelist chain, add a default DROP at the end. This is not necessary for a
328 // blacklist chain, because all user-defined chains implicitly RETURN at the end.
329 if (isWhitelist) {
330 StringAppendF(&commands, "-A %s -j DROP\n", name);
331 }
332
333 StringAppendF(&commands, "COMMIT\n\x04"); // EOT.
334
335 return commands;
336 }
337
replaceUidChain(const char * name,bool isWhitelist,const std::vector<int32_t> & uids)338 int FirewallController::replaceUidChain(
339 const char *name, bool isWhitelist, const std::vector<int32_t>& uids) {
340 std::string commands4 = makeUidRules(V4, name, isWhitelist, uids);
341 std::string commands6 = makeUidRules(V6, name, isWhitelist, uids);
342 return execIptablesRestore(V4, commands4.c_str()) | execIptablesRestore(V6, commands6.c_str());
343 }
344