oem_iptables_hook.cpp revision 7c73e8951d91b5afe9d52f88d7ed3a09d120a725 
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 <stdio.h>
18#include <stdlib.h>
19#include <sys/types.h>
20#include <sys/wait.h>
21#include <errno.h>
22#include <string.h>
23#include <unistd.h>
24
25#define LOG_TAG "OemIptablesHook"
26#include <cutils/log.h>
27
28extern "C" int system_nosh(const char *command);
29
30static char IPTABLES_PATH[] = "/system/bin/iptables";
31static char OEM_SCRIPT_PATH[] = "/system/bin/oem-iptables-init.sh";
32
33static int runIptablesCmd(const char *cmd) {
34    char *buffer;
35    size_t len = strnlen(cmd, 255);
36    int res;
37
38    if (len == 255) {
39        ALOGE("command too long");
40        return -1;
41    }
42
43    asprintf(&buffer, "%s %s", IPTABLES_PATH, cmd);
44    res = system_nosh(buffer);
45    free(buffer);
46    return res;
47}
48
49static bool oemSetupHooks() {
50    // Order is important!
51    // -N to create the chain (no-op if already exist).
52    // -D to delete any pre-existing jump rule, to prevent dupes (no-op if doesn't exist)
53    // -I to insert our jump rule into the default chain
54
55    runIptablesCmd("-N oem_out");
56    runIptablesCmd("-D OUTPUT -j oem_out");
57    if (runIptablesCmd("-I OUTPUT -j oem_out"))
58        return false;
59
60    runIptablesCmd("-N oem_fwd");
61    runIptablesCmd("-D FORWARD -j oem_fwd");
62    if (runIptablesCmd("-I FORWARD -j oem_fwd"))
63        return false;
64
65    runIptablesCmd("-t nat -N oem_nat_pre");
66    runIptablesCmd("-t nat -D PREROUTING -j oem_nat_pre");
67    if (runIptablesCmd("-t nat -I PREROUTING -j oem_nat_pre"))
68        return false;
69
70    return true;
71}
72
73static bool oemCleanupHooks() {
74    // Order is important!
75    // -D to remove ref to the chain
76    // -F to empty the chain
77    // -X to delete the chain
78
79    runIptablesCmd("-D OUTPUT -j oem_out");
80    runIptablesCmd("-F oem_out");
81    runIptablesCmd("-X oem_out");
82
83    runIptablesCmd("-D FORWARD -j oem_fwd");
84    runIptablesCmd("-F oem_fwd");
85    runIptablesCmd("-X oem_fwd");
86
87    runIptablesCmd("-t nat -D PREROUTING -j oem_nat_pre");
88    runIptablesCmd("-t nat -F oem_nat_pre");
89    runIptablesCmd("-t nat -X oem_nat_pre");
90
91    return true;
92}
93
94static bool oemInitChains() {
95    int ret = system(OEM_SCRIPT_PATH);
96    if ((-1 == ret) || (0 != WEXITSTATUS(ret))) {
97        ALOGE("%s failed: %s", OEM_SCRIPT_PATH, strerror(errno));
98        oemCleanupHooks();
99        return false;
100    }
101    return true;
102}
103
104
105void setupOemIptablesHook() {
106    if (0 == access(OEM_SCRIPT_PATH, R_OK | X_OK)) {
107        // The call to oemCleanupHooks() is superfluous when done on bootup,
108        // but is needed for the case where netd has crashed/stopped and is
109        // restarted.
110        if (oemCleanupHooks() && oemSetupHooks() && oemInitChains()) {
111            ALOGI("OEM iptable hook installed.");
112        }
113    }
114}
115