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platform_system_core
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platform_system_core/logd/main.cpp

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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 <poll.h>
#include <sched.h>
#include <semaphore.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/capability.h>
#include <sys/klog.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <syslog.h>
#include <unistd.h>
#include <cstdbool>
#include <memory>
#include <android-base/macros.h>
#include <cutils/android_get_control_file.h>
#include <cutils/properties.h>
#include <cutils/sched_policy.h>
#include <cutils/sockets.h>
#include <log/event_tag_map.h>
#include <packagelistparser/packagelistparser.h>
#include <private/android_filesystem_config.h>
#include <private/android_logger.h>
#include <utils/threads.h>
#include "CommandListener.h"
#include "LogBuffer.h"
#include "LogListener.h"
#include "LogAudit.h"
#include "LogKlog.h"
#include "LogUtils.h"
#define KMSG_PRIORITY(PRI) \
'<', \
'0' + LOG_MAKEPRI(LOG_DAEMON, LOG_PRI(PRI)) / 10, \
'0' + LOG_MAKEPRI(LOG_DAEMON, LOG_PRI(PRI)) % 10, \
'>'
//
// 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(bool klogd, bool auditd) {
// Tricky, if ro.build.type is "eng" then this is true because of the
// side effect that ro.debuggable == 1 as well, else it is false.
bool eng = __android_logger_property_get_bool("ro.build.type", BOOL_DEFAULT_FALSE);
struct sched_param param;
memset(&param, 0, sizeof(param));
if (set_sched_policy(0, SP_BACKGROUND) < 0) {
android::prdebug("failed to set background scheduling policy");
if (!eng) return -1;
}
if (sched_setscheduler((pid_t) 0, SCHED_BATCH, &param) < 0) {
android::prdebug("failed to set batch scheduler");
if (!eng) return -1;
}
if (setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_BACKGROUND) < 0) {
android::prdebug("failed to set background cgroup");
if (!eng) return -1;
}
if (!eng && (prctl(PR_SET_DUMPABLE, 0) < 0)) {
android::prdebug("failed to clear PR_SET_DUMPABLE");
return -1;
}
if (prctl(PR_SET_KEEPCAPS, 1) < 0) {
android::prdebug("failed to set PR_SET_KEEPCAPS");
if (!eng) return -1;
}
std::unique_ptr<struct _cap_struct, int(*)(void *)> caps(cap_init(), cap_free);
if (cap_clear(caps.get()) < 0) return -1;
cap_value_t cap_value[] = {
CAP_SETGID, // must be first for below
klogd ? CAP_SYSLOG : CAP_SETGID,
auditd ? CAP_AUDIT_CONTROL : CAP_SETGID
};
if (cap_set_flag(caps.get(), CAP_PERMITTED,
arraysize(cap_value), cap_value,
CAP_SET) < 0) return -1;
if (cap_set_flag(caps.get(), CAP_EFFECTIVE,
arraysize(cap_value), cap_value,
CAP_SET) < 0) return -1;
if (cap_set_proc(caps.get()) < 0) {
android::prdebug("failed to set CAP_SETGID, CAP_SYSLOG or CAP_AUDIT_CONTROL (%d)", errno);
if (!eng) return -1;
}
gid_t groups[] = { AID_READPROC };
if (setgroups(arraysize(groups), groups) == -1) {
android::prdebug("failed to set AID_READPROC groups");
if (!eng) return -1;
}
if (setgid(AID_LOGD) != 0) {
android::prdebug("failed to set AID_LOGD gid");
if (!eng) return -1;
}
if (setuid(AID_LOGD) != 0) {
android::prdebug("failed to set AID_LOGD uid");
if (!eng) return -1;
}
if (cap_set_flag(caps.get(), CAP_PERMITTED, 1, cap_value, CAP_CLEAR) < 0) return -1;
if (cap_set_flag(caps.get(), CAP_EFFECTIVE, 1, cap_value, CAP_CLEAR) < 0) return -1;
if (cap_set_proc(caps.get()) < 0) {
android::prdebug("failed to clear CAP_SETGID (%d)", errno);
if (!eng) return -1;
}
return 0;
}
// Property helper
static bool check_flag(const char *prop, const char *flag) {
const char *cp = strcasestr(prop, flag);
if (!cp) {
return false;
}
// We only will document comma (,)
static const char sep[] = ",:;|+ \t\f";
if ((cp != prop) && !strchr(sep, cp[-1])) {
return false;
}
cp += strlen(flag);
return !*cp || !!strchr(sep, *cp);
}
static int fdDmesg = -1;
void android::prdebug(const char *fmt, ...) {
if (fdDmesg < 0) {
return;
}
static const char message[] = {
KMSG_PRIORITY(LOG_DEBUG), 'l', 'o', 'g', 'd', ':', ' '
};
char buffer[256];
memcpy(buffer, message, sizeof(message));
va_list ap;
va_start(ap, fmt);
int n = vsnprintf(buffer + sizeof(message),
sizeof(buffer) - sizeof(message), fmt, ap);
va_end(ap);
if (n > 0) {
buffer[sizeof(buffer) - 1] = '\0';
if (!strchr(buffer, '\n')) {
buffer[sizeof(buffer) - 2] = '\0';
strlcat(buffer, "\n", sizeof(buffer));
}
write(fdDmesg, buffer, strlen(buffer));
}
}
static sem_t uidName;
static uid_t uid;
static char *name;
static sem_t reinit;
static bool reinit_running = false;
static LogBuffer *logBuf = NULL;
static bool package_list_parser_cb(pkg_info *info, void * /* userdata */) {
bool rc = true;
if (info->uid == uid) {
name = strdup(info->name);
// false to stop processing
rc = false;
}
packagelist_free(info);
return rc;
}
static void *reinit_thread_start(void * /*obj*/) {
prctl(PR_SET_NAME, "logd.daemon");
set_sched_policy(0, SP_BACKGROUND);
setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_BACKGROUND);
cap_t caps = cap_init();
(void)cap_clear(caps);
(void)cap_set_proc(caps);
(void)cap_free(caps);
// If we are AID_ROOT, we should drop to AID_LOGD+AID_SYSTEM, if we are
// anything else, we have even lesser privileges and accept our fate. Not
// worth checking for error returns setting this thread's privileges.
(void)setgid(AID_SYSTEM); // readonly access to /data/system/packages.list
(void)setuid(AID_LOGD); // access to everything logd.
while (reinit_running && !sem_wait(&reinit) && reinit_running) {
// uidToName Privileged Worker
if (uid) {
name = NULL;
packagelist_parse(package_list_parser_cb, NULL);
uid = 0;
sem_post(&uidName);
continue;
}
if (fdDmesg >= 0) {
static const char reinit_message[] = { KMSG_PRIORITY(LOG_INFO),
'l', 'o', 'g', 'd', '.', 'd', 'a', 'e', 'm', 'o', 'n', ':',
' ', 'r', 'e', 'i', 'n', 'i', 't', '\n' };
write(fdDmesg, reinit_message, sizeof(reinit_message));
}
// Anything that reads persist.<property>
if (logBuf) {
logBuf->init();
logBuf->initPrune(NULL);
}
}
return NULL;
}
static sem_t sem_name;
char *android::uidToName(uid_t u) {
if (!u || !reinit_running) {
return NULL;
}
sem_wait(&sem_name);
// Not multi-thread safe, we use sem_name to protect
uid = u;
name = NULL;
sem_post(&reinit);
sem_wait(&uidName);
char *ret = name;
sem_post(&sem_name);
return ret;
}
// Serves as a global method to trigger reinitialization
// and as a function that can be provided to signal().
void reinit_signal_handler(int /*signal*/) {
sem_post(&reinit);
}
// tagToName converts an events tag into a name
const char *android::tagToName(size_t *len, uint32_t tag) {
static const EventTagMap *map;
if (!map) {
sem_wait(&sem_name);
if (!map) {
map = android_openEventTagMap(NULL);
}
sem_post(&sem_name);
if (!map) {
if (len) len = 0;
return NULL;
}
}
return android_lookupEventTag_len(map, len, tag);
}
static void readDmesg(LogAudit *al, LogKlog *kl) {
if (!al && !kl) {
return;
}
int rc = klogctl(KLOG_SIZE_BUFFER, NULL, 0);
if (rc <= 0) {
return;
}
size_t len = rc + 1024; // Margin for additional input race or trailing nul
std::unique_ptr<char []> buf(new char[len]);
rc = klogctl(KLOG_READ_ALL, buf.get(), len);
if (rc <= 0) {
return;
}
if ((size_t)rc < len) {
len = rc + 1;
}
buf[--len] = '\0';
if (kl && kl->isMonotonic()) {
kl->synchronize(buf.get(), len);
}
size_t sublen;
for (char *ptr = NULL, *tok = buf.get();
(rc >= 0) && ((tok = log_strntok_r(tok, &len, &ptr, &sublen)));
tok = NULL) {
if (al) {
rc = al->log(tok, sublen);
}
if (kl) {
rc = kl->log(tok, sublen);
}
}
}
static int issueReinit() {
cap_t caps = cap_init();
(void)cap_clear(caps);
(void)cap_set_proc(caps);
(void)cap_free(caps);
int sock = TEMP_FAILURE_RETRY(
socket_local_client("logd",
ANDROID_SOCKET_NAMESPACE_RESERVED,
SOCK_STREAM));
if (sock < 0) return -errno;
static const char reinitStr[] = "reinit";
ssize_t ret = TEMP_FAILURE_RETRY(write(sock, reinitStr, sizeof(reinitStr)));
if (ret < 0) return -errno;
struct pollfd p;
memset(&p, 0, sizeof(p));
p.fd = sock;
p.events = POLLIN;
ret = TEMP_FAILURE_RETRY(poll(&p, 1, 1000));
if (ret < 0) return -errno;
if ((ret == 0) || !(p.revents & POLLIN)) return -ETIME;
static const char success[] = "success";
char buffer[sizeof(success) - 1];
memset(buffer, 0, sizeof(buffer));
ret = TEMP_FAILURE_RETRY(read(sock, buffer, sizeof(buffer)));
if (ret < 0) return -errno;
return strncmp(buffer, success, sizeof(success) - 1) != 0;
}
// Foreground waits for exit of the main persistent threads
// that are started here. The threads are created to manage
// UNIX domain client sockets for writing, reading and
// controlling the user space logger, and for any additional
// logging plugins like auditd and restart control. Additional
// transitory per-client threads are created for each reader.
int main(int argc, char *argv[]) {
// issue reinit command. KISS argument parsing.
if ((argc > 1) && argv[1] && !strcmp(argv[1], "--reinit")) {
return issueReinit();
}
static const char dev_kmsg[] = "/dev/kmsg";
fdDmesg = android_get_control_file(dev_kmsg);
if (fdDmesg < 0) {
fdDmesg = TEMP_FAILURE_RETRY(open(dev_kmsg, O_WRONLY | O_CLOEXEC));
}
int fdPmesg = -1;
bool klogd = __android_logger_property_get_bool("logd.kernel",
BOOL_DEFAULT_TRUE |
BOOL_DEFAULT_FLAG_PERSIST |
BOOL_DEFAULT_FLAG_ENG |
BOOL_DEFAULT_FLAG_SVELTE);
if (klogd) {
static const char proc_kmsg[] = "/proc/kmsg";
fdPmesg = android_get_control_file(proc_kmsg);
if (fdPmesg < 0) {
fdPmesg = TEMP_FAILURE_RETRY(open(proc_kmsg,
O_RDONLY | O_NDELAY | O_CLOEXEC));
}
if (fdPmesg < 0) android::prdebug("Failed to open %s\n", proc_kmsg);
}
// Reinit Thread
sem_init(&reinit, 0, 0);
sem_init(&uidName, 0, 0);
sem_init(&sem_name, 0, 1);
pthread_attr_t attr;
if (!pthread_attr_init(&attr)) {
struct sched_param param;
memset(&param, 0, sizeof(param));
pthread_attr_setschedparam(&attr, &param);
pthread_attr_setschedpolicy(&attr, SCHED_BATCH);
if (!pthread_attr_setdetachstate(&attr,
PTHREAD_CREATE_DETACHED)) {
pthread_t thread;
reinit_running = true;
if (pthread_create(&thread, &attr, reinit_thread_start, NULL)) {
reinit_running = false;
}
}
pthread_attr_destroy(&attr);
}
bool auditd = __android_logger_property_get_bool("ro.logd.auditd",
BOOL_DEFAULT_TRUE);
if (drop_privs(klogd, auditd) != 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.
logBuf = new LogBuffer(times);
signal(SIGHUP, reinit_signal_handler);
if (__android_logger_property_get_bool("logd.statistics",
BOOL_DEFAULT_TRUE |
BOOL_DEFAULT_FLAG_PERSIST |
BOOL_DEFAULT_FLAG_ENG |
BOOL_DEFAULT_FLAG_SVELTE)) {
logBuf->enableStatistics();
}
// 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(600)) {
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.
LogAudit *al = NULL;
if (auditd) {
al = new LogAudit(logBuf, reader,
__android_logger_property_get_bool(
"ro.logd.auditd.dmesg",
BOOL_DEFAULT_TRUE)
? fdDmesg
: -1);
}
LogKlog *kl = NULL;
if (klogd) {
kl = new LogKlog(logBuf, reader, fdDmesg, fdPmesg, al != NULL);
}
readDmesg(al, kl);
// failure is an option ... messages are in dmesg (required by standard)
if (kl && kl->startListener()) {
delete kl;
}
if (al && al->startListener()) {
delete al;
}
TEMP_FAILURE_RETRY(pause());
exit(0);
}
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