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/*
* Copyright (C) 2012-2013 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 <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/capability.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/prctl.h>
#include <cutils/properties.h>
#include "private/android_filesystem_config.h"
#include "CommandListener.h"
#include "LogBuffer.h"
#include "LogListener.h"
#include "LogAudit.h"
//
// The service is designed to be run by init, it does not respond well
// to starting up manually. When starting up manually the sockets will
// fail to open typically for one of the following reasons:
// EADDRINUSE if logger is running.
// EACCESS if started without precautions (below)
//
// Here is a cookbook procedure for starting up logd manually assuming
// init is out of the way, pedantically all permissions and selinux
// security is put back in place:
//
// setenforce 0
// rm /dev/socket/logd*
// chmod 777 /dev/socket
// # here is where you would attach the debugger or valgrind for example
// runcon u:r:logd:s0 /system/bin/logd </dev/null >/dev/null 2>&1 &
// sleep 1
// chmod 755 /dev/socket
// chown logd.logd /dev/socket/logd*
// restorecon /dev/socket/logd*
// setenforce 1
//
// If minimalism prevails, typical for debugging and security is not a concern:
//
// setenforce 0
// chmod 777 /dev/socket
// logd
//
static int drop_privs() {
struct sched_param param;
memset(¶m, 0, sizeof(param));
if (sched_setscheduler((pid_t) 0, SCHED_BATCH, ¶m) < 0) {
return -1;
}
if (prctl(PR_SET_KEEPCAPS, 1) < 0) {
return -1;
}
if (setgid(AID_LOGD) != 0) {
return -1;
}
if (setuid(AID_LOGD) != 0) {
return -1;
}
struct __user_cap_header_struct capheader;
struct __user_cap_data_struct capdata[2];
memset(&capheader, 0, sizeof(capheader));
memset(&capdata, 0, sizeof(capdata));
capheader.version = _LINUX_CAPABILITY_VERSION_3;
capheader.pid = 0;
capdata[CAP_TO_INDEX(CAP_SYSLOG)].permitted = CAP_TO_MASK(CAP_SYSLOG);
capdata[CAP_TO_INDEX(CAP_AUDIT_CONTROL)].permitted |= CAP_TO_MASK(CAP_AUDIT_CONTROL);
capdata[0].effective = capdata[0].permitted;
capdata[1].effective = capdata[1].permitted;
capdata[0].inheritable = 0;
capdata[1].inheritable = 0;
if (capset(&capheader, &capdata[0]) < 0) {
return -1;
}
return 0;
}
// Property helper
static bool property_get_bool(const char *key, bool def) {
char property[PROPERTY_VALUE_MAX];
property_get(key, property, "");
if (!strcasecmp(property, "true")) {
return true;
}
if (!strcasecmp(property, "false")) {
return false;
}
return def;
}
// Foreground waits for exit of the three main persistent threads that
// are started here. The three threads are created to manage UNIX
// domain client sockets for writing, reading and controlling the user
// space logger. Additional transitory per-client threads are created
// for each reader once they register.
int main() {
bool auditd = property_get_bool("logd.auditd", true);
int fdDmesg = -1;
if (auditd && property_get_bool("logd.auditd.dmesg", true)) {
fdDmesg = open("/dev/kmsg", O_WRONLY);
}
if (drop_privs() != 0) {
return -1;
}
// Serves the purpose of managing the last logs times read on a
// socket connection, and as a reader lock on a range of log
// entries.
LastLogTimes *times = new LastLogTimes();
// LogBuffer is the object which is responsible for holding all
// log entries.
LogBuffer *logBuf = new LogBuffer(times);
if (property_get_bool("logd.statistics.dgram_qlen", false)) {
logBuf->enableDgramQlenStatistics();
}
// LogReader listens on /dev/socket/logdr. When a client
// connects, log entries in the LogBuffer are written to the client.
LogReader *reader = new LogReader(logBuf);
if (reader->startListener()) {
exit(1);
}
// LogListener listens on /dev/socket/logdw for client
// initiated log messages. New log entries are added to LogBuffer
// and LogReader is notified to send updates to connected clients.
LogListener *swl = new LogListener(logBuf, reader);
// Backlog and /proc/sys/net/unix/max_dgram_qlen set to large value
if (swl->startListener(300)) {
exit(1);
}
// Command listener listens on /dev/socket/logd for incoming logd
// administrative commands.
CommandListener *cl = new CommandListener(logBuf, reader, swl);
if (cl->startListener()) {
exit(1);
}
// LogAudit listens on NETLINK_AUDIT socket for selinux
// initiated log messages. New log entries are added to LogBuffer
// and LogReader is notified to send updates to connected clients.
if (auditd) {
// failure is an option ... messages are in dmesg (required by standard)
LogAudit *al = new LogAudit(logBuf, reader, fdDmesg);
if (al->startListener()) {
delete al;
close(fdDmesg);
}
}
pause();
exit(0);
}
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