/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <string>
#include <vector>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define LOG_TAG "StrictController"
#define LOG_NDEBUG 0
#include <cutils/log.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include "ConnmarkFlags.h"
#include "NetdConstants.h"
#include "StrictController.h"
auto StrictController::execIptablesRestore = ::execIptablesRestore;
const char* StrictController::LOCAL_OUTPUT = "st_OUTPUT";
const char* StrictController::LOCAL_CLEAR_DETECT = "st_clear_detect";
const char* StrictController::LOCAL_CLEAR_CAUGHT = "st_clear_caught";
const char* StrictController::LOCAL_PENALTY_LOG = "st_penalty_log";
const char* StrictController::LOCAL_PENALTY_REJECT = "st_penalty_reject";
using android::base::Join;
using android::base::StringPrintf;
StrictController::StrictController(void) {
}
int StrictController::enableStrict(void) {
char connmarkFlagAccept[16];
char connmarkFlagReject[16];
char connmarkFlagTestAccept[32];
char connmarkFlagTestReject[32];
sprintf(connmarkFlagAccept, "0x%x", ConnmarkFlags::STRICT_RESOLVED_ACCEPT);
sprintf(connmarkFlagReject, "0x%x", ConnmarkFlags::STRICT_RESOLVED_REJECT);
sprintf(connmarkFlagTestAccept, "0x%x/0x%x",
ConnmarkFlags::STRICT_RESOLVED_ACCEPT,
ConnmarkFlags::STRICT_RESOLVED_ACCEPT);
sprintf(connmarkFlagTestReject, "0x%x/0x%x",
ConnmarkFlags::STRICT_RESOLVED_REJECT,
ConnmarkFlags::STRICT_RESOLVED_REJECT);
disableStrict();
int res = 0;
std::vector<std::string> v4, v6;
#define CMD_V4(...) { auto cmd = StringPrintf(__VA_ARGS__); v4.push_back(cmd); }
#define CMD_V6(...) { auto cmd = StringPrintf(__VA_ARGS__); v6.push_back(cmd); }
#define CMD_V4V6(...) { CMD_V4(__VA_ARGS__); CMD_V6(__VA_ARGS__); };
CMD_V4V6("*filter");
// Chain triggered when cleartext socket detected and penalty is log
CMD_V4V6("-A %s -j CONNMARK --or-mark %s", LOCAL_PENALTY_LOG, connmarkFlagAccept);
CMD_V4V6("-A %s -j NFLOG --nflog-group 0", LOCAL_PENALTY_LOG);
// Chain triggered when cleartext socket detected and penalty is reject
CMD_V4V6("-A %s -j CONNMARK --or-mark %s", LOCAL_PENALTY_REJECT, connmarkFlagReject);
CMD_V4V6("-A %s -j NFLOG --nflog-group 0", LOCAL_PENALTY_REJECT);
CMD_V4V6("-A %s -j REJECT", LOCAL_PENALTY_REJECT);
// We use a high-order mark bit to keep track of connections that we've already resolved.
// Quickly skip connections that we've already resolved
CMD_V4V6("-A %s -m connmark --mark %s -j REJECT", LOCAL_CLEAR_DETECT, connmarkFlagTestReject);
CMD_V4V6("-A %s -m connmark --mark %s -j RETURN", LOCAL_CLEAR_DETECT, connmarkFlagTestAccept);
// Look for IPv4 TCP/UDP connections with TLS/DTLS header
const char *u32;
u32 = "0>>22&0x3C@ 12>>26&0x3C@ 0&0xFFFF0000=0x16030000 &&"
"0>>22&0x3C@ 12>>26&0x3C@ 4&0x00FF0000=0x00010000";
CMD_V4("-A %s -p tcp -m u32 --u32 \"%s\" -j CONNMARK --or-mark %s",
LOCAL_CLEAR_DETECT, u32, connmarkFlagAccept);
u32 = "0>>22&0x3C@ 8&0xFFFF0000=0x16FE0000 &&"
"0>>22&0x3C@ 20&0x00FF0000=0x00010000";
CMD_V4("-A %s -p udp -m u32 --u32 \"%s\" -j CONNMARK --or-mark %s",
LOCAL_CLEAR_DETECT, u32, connmarkFlagAccept);
// Look for IPv6 TCP/UDP connections with TLS/DTLS header. The IPv6 header
// doesn't have an IHL field to shift with, so we have to manually add in
// the 40-byte offset at every step.
u32 = "52>>26&0x3C@ 40&0xFFFF0000=0x16030000 &&"
"52>>26&0x3C@ 44&0x00FF0000=0x00010000";
CMD_V6("-A %s -p tcp -m u32 --u32 \"%s\" -j CONNMARK --or-mark %s",
LOCAL_CLEAR_DETECT, u32, connmarkFlagAccept);
u32 = "48&0xFFFF0000=0x16FE0000 &&"
"60&0x00FF0000=0x00010000";
CMD_V6("-A %s -p udp -m u32 --u32 \"%s\" -j CONNMARK --or-mark %s",
LOCAL_CLEAR_DETECT, u32, connmarkFlagAccept);
// Skip newly classified connections from above
CMD_V4V6("-A %s -m connmark --mark %s -j RETURN", LOCAL_CLEAR_DETECT, connmarkFlagTestAccept);
// Handle TCP/UDP payloads that didn't match TLS/DTLS filters above,
// which means we've probably found cleartext data. The TCP variant
// depends on u32 returning false when we try reading into the message
// body to ignore empty ACK packets.
u32 = "0>>22&0x3C@ 12>>26&0x3C@ 0&0x0=0x0";
CMD_V4("-A %s -p tcp -m state --state ESTABLISHED -m u32 --u32 \"%s\" -j %s",
LOCAL_CLEAR_DETECT, u32, LOCAL_CLEAR_CAUGHT);
u32 = "52>>26&0x3C@ 40&0x0=0x0";
CMD_V6("-A %s -p tcp -m state --state ESTABLISHED -m u32 --u32 \"%s\" -j %s",
LOCAL_CLEAR_DETECT, u32, LOCAL_CLEAR_CAUGHT);
CMD_V4V6("-A %s -p udp -j %s", LOCAL_CLEAR_DETECT, LOCAL_CLEAR_CAUGHT);
CMD_V4V6("COMMIT\n");
res |= execIptablesRestore(V4, Join(v4, '\n'));
res |= execIptablesRestore(V6, Join(v6, '\n'));
#undef CMD_V4
#undef CMD_V6
#undef CMD_V4V6
return res;
}
int StrictController::disableStrict(void) {
// Flush any existing rules
#define CLEAR_CHAIN(x) StringPrintf(":%s -", (x))
std::vector<std::string> commandList = {
"*filter",
CLEAR_CHAIN(LOCAL_OUTPUT),
CLEAR_CHAIN(LOCAL_PENALTY_LOG),
CLEAR_CHAIN(LOCAL_PENALTY_REJECT),
CLEAR_CHAIN(LOCAL_CLEAR_CAUGHT),
CLEAR_CHAIN(LOCAL_CLEAR_DETECT),
"COMMIT\n"
};
const std::string commands = Join(commandList, '\n');
return execIptablesRestore(V4V6, commands);
#undef CLEAR_CHAIN
}
int StrictController::setUidCleartextPenalty(uid_t uid, StrictPenalty penalty) {
// When a penalty is set, we don't know what penalty the UID previously had. In order to be able
// to clear the previous penalty without causing an iptables error by deleting rules that don't
// exist, put each UID's rules in a chain specific to that UID. That way, the commands we need
// to run to clear the previous penalty don't depend on what the penalty actually was - all we
// need to do is clear the chain.
std::string perUidChain = StringPrintf("st_clear_caught_%u", uid);
std::vector<std::string> commands;
if (penalty == ACCEPT) {
// Clean up any old rules
commands = {
"*filter",
StringPrintf("-D %s -m owner --uid-owner %d -j %s",
LOCAL_OUTPUT, uid, LOCAL_CLEAR_DETECT),
StringPrintf("-D %s -m owner --uid-owner %d -j %s",
LOCAL_CLEAR_CAUGHT, uid, perUidChain.c_str()),
StringPrintf("-F %s", perUidChain.c_str()),
StringPrintf("-X %s", perUidChain.c_str()),
};
} else {
// Always take a detour to investigate this UID
commands.push_back("*filter");
commands.push_back(StringPrintf(":%s -", perUidChain.c_str()));
commands.push_back(StringPrintf("-I %s -m owner --uid-owner %d -j %s",
LOCAL_OUTPUT, uid, LOCAL_CLEAR_DETECT));
commands.push_back(StringPrintf("-I %s -m owner --uid-owner %d -j %s",
LOCAL_CLEAR_CAUGHT, uid, perUidChain.c_str()));
if (penalty == LOG) {
commands.push_back(StringPrintf("-A %s -j %s", perUidChain.c_str(), LOCAL_PENALTY_LOG));
} else if (penalty == REJECT) {
commands.push_back(StringPrintf("-A %s -j %s", perUidChain.c_str(),
LOCAL_PENALTY_REJECT));
}
}
commands.push_back("COMMIT\n");
return execIptablesRestore(V4V6, Join(commands, "\n"));
}