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/*
* Copyright (C) 2012-2014 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 <limits.h>
#include <sys/cdefs.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/un.h>
#include <unistd.h>
#include <cutils/sockets.h>
#include <private/android_filesystem_config.h>
#include <private/android_logger.h>
#include "LogBuffer.h"
#include "LogListener.h"
#include "LogUtils.h"
LogListener::LogListener(LogBufferInterface* buf, LogReader* reader)
: SocketListener(getLogSocket(), false), logbuf(buf), reader(reader) {
}
bool LogListener::onDataAvailable(SocketClient* cli) {
static bool name_set;
if (!name_set) {
prctl(PR_SET_NAME, "logd.writer");
name_set = true;
}
char buffer[sizeof_log_id_t + sizeof(uint16_t) + sizeof(log_time) +
LOGGER_ENTRY_MAX_PAYLOAD];
struct iovec iov = { buffer, sizeof(buffer) };
alignas(4) char control[CMSG_SPACE(sizeof(struct ucred))];
struct msghdr hdr = {
NULL, 0, &iov, 1, control, sizeof(control), 0,
};
int socket = cli->getSocket();
// To clear the entire buffer is secure/safe, but this contributes to 1.68%
// overhead under logging load. We are safe because we check counts.
// memset(buffer, 0, sizeof(buffer));
ssize_t n = recvmsg(socket, &hdr, 0);
if (n <= (ssize_t)(sizeof(android_log_header_t))) {
return false;
}
struct ucred* cred = NULL;
struct cmsghdr* cmsg = CMSG_FIRSTHDR(&hdr);
while (cmsg != NULL) {
if (cmsg->cmsg_level == SOL_SOCKET &&
cmsg->cmsg_type == SCM_CREDENTIALS) {
cred = (struct ucred*)CMSG_DATA(cmsg);
break;
}
cmsg = CMSG_NXTHDR(&hdr, cmsg);
}
if (cred == NULL) {
return false;
}
if (cred->uid == AID_LOGD) {
// ignore log messages we send to ourself.
// Such log messages are often generated by libraries we depend on
// which use standard Android logging.
return false;
}
android_log_header_t* header =
reinterpret_cast<android_log_header_t*>(buffer);
if (/* header->id < LOG_ID_MIN || */ header->id >= LOG_ID_MAX ||
header->id == LOG_ID_KERNEL) {
return false;
}
if ((header->id == LOG_ID_SECURITY) &&
(!__android_log_security() ||
!clientHasLogCredentials(cred->uid, cred->gid, cred->pid))) {
return false;
}
char* msg = ((char*)buffer) + sizeof(android_log_header_t);
n -= sizeof(android_log_header_t);
// NB: hdr.msg_flags & MSG_TRUNC is not tested, silently passing a
// truncated message to the logs.
if (logbuf != nullptr) {
int res = logbuf->log(
(log_id_t)header->id, header->realtime, cred->uid, cred->pid,
header->tid, msg,
((size_t)n <= USHRT_MAX) ? (unsigned short)n : USHRT_MAX);
if (res > 0 && reader != nullptr) {
reader->notifyNewLog();
}
}
return true;
}
int LogListener::getLogSocket() {
static const char socketName[] = "logdw";
int sock = android_get_control_socket(socketName);
if (sock < 0) {
sock = socket_local_server(
socketName, ANDROID_SOCKET_NAMESPACE_RESERVED, SOCK_DGRAM);
}
int on = 1;
if (setsockopt(sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)) < 0) {
return -1;
}
return sock;
}
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