/*
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* Copyright (C) 2012-2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <ctype.h>
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#include <limits.h>
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#include <stdio.h>
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#include <sys/cdefs.h>
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#include <sys/prctl.h>
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#include <sys/socket.h>
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#include <sys/types.h>
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#include <sys/un.h>
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#include <unistd.h>
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#include <cutils/sockets.h>
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#include <private/android_filesystem_config.h>
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#include <private/android_logger.h>
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#include "LogBuffer.h"
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#include "LogListener.h"
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#include "LogUtils.h"
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LogListener::LogListener(LogBufferInterface* buf, LogReader* reader)
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: SocketListener(getLogSocket(), false), logbuf(buf), reader(reader) {
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}
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bool LogListener::onDataAvailable(SocketClient* cli) {
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static bool name_set;
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if (!name_set) {
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prctl(PR_SET_NAME, "logd.writer");
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name_set = true;
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}
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// + 1 to ensure null terminator if MAX_PAYLOAD buffer is received
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char buffer[sizeof_log_id_t + sizeof(uint16_t) + sizeof(log_time) +
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LOGGER_ENTRY_MAX_PAYLOAD + 1];
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struct iovec iov = { buffer, sizeof(buffer) - 1 };
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alignas(4) char control[CMSG_SPACE(sizeof(struct ucred))];
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struct msghdr hdr = {
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nullptr, 0, &iov, 1, control, sizeof(control), 0,
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};
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int socket = cli->getSocket();
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// To clear the entire buffer is secure/safe, but this contributes to 1.68%
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// overhead under logging load. We are safe because we check counts, but
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// still need to clear null terminator
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// memset(buffer, 0, sizeof(buffer));
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ssize_t n = recvmsg(socket, &hdr, 0);
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if (n <= (ssize_t)(sizeof(android_log_header_t))) {
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return false;
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}
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buffer[n] = 0;
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struct ucred* cred = nullptr;
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struct cmsghdr* cmsg = CMSG_FIRSTHDR(&hdr);
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while (cmsg != nullptr) {
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if (cmsg->cmsg_level == SOL_SOCKET &&
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cmsg->cmsg_type == SCM_CREDENTIALS) {
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cred = (struct ucred*)CMSG_DATA(cmsg);
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break;
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}
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cmsg = CMSG_NXTHDR(&hdr, cmsg);
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}
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struct ucred fake_cred;
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if (cred == nullptr) {
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cred = &fake_cred;
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cred->pid = 0;
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cred->uid = DEFAULT_OVERFLOWUID;
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}
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if (cred->uid == AID_LOGD) {
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// ignore log messages we send to ourself.
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// Such log messages are often generated by libraries we depend on
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// which use standard Android logging.
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return false;
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}
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android_log_header_t* header =
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reinterpret_cast<android_log_header_t*>(buffer);
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log_id_t logId = static_cast<log_id_t>(header->id);
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if (/* logId < LOG_ID_MIN || */ logId >= LOG_ID_MAX ||
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logId == LOG_ID_KERNEL) {
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return false;
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}
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if ((logId == LOG_ID_SECURITY) &&
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(!__android_log_security() ||
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!clientHasLogCredentials(cred->uid, cred->gid, cred->pid))) {
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return false;
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}
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// Check credential validity, acquire corrected details if not supplied.
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if (cred->pid == 0) {
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cred->pid = logbuf ? logbuf->tidToPid(header->tid)
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: android::tidToPid(header->tid);
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if (cred->pid == getpid()) {
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// We expect that /proc/<tid>/ is accessible to self even without
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// readproc group, so that we will always drop messages that come
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// from any of our logd threads and their library calls.
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return false; // ignore self
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}
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}
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if (cred->uid == DEFAULT_OVERFLOWUID) {
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uid_t uid =
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logbuf ? logbuf->pidToUid(cred->pid) : android::pidToUid(cred->pid);
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if (uid == AID_LOGD) {
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uid = logbuf ? logbuf->pidToUid(header->tid)
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: android::pidToUid(cred->pid);
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}
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if (uid != AID_LOGD) cred->uid = uid;
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}
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char* msg = ((char*)buffer) + sizeof(android_log_header_t);
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n -= sizeof(android_log_header_t);
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// NB: hdr.msg_flags & MSG_TRUNC is not tested, silently passing a
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// truncated message to the logs.
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if (logbuf != nullptr) {
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int res = logbuf->log(
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logId, header->realtime, cred->uid, cred->pid, header->tid, msg,
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((size_t)n <= UINT16_MAX) ? (uint16_t)n : UINT16_MAX);
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if (res > 0 && reader != nullptr) {
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reader->notifyNewLog(static_cast<log_mask_t>(1 << logId));
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}
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}
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return true;
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}
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int LogListener::getLogSocket() {
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static const char socketName[] = "logdw";
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int sock = android_get_control_socket(socketName);
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if (sock < 0) { // logd started up in init.sh
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sock = socket_local_server(
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socketName, ANDROID_SOCKET_NAMESPACE_RESERVED, SOCK_DGRAM);
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int on = 1;
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if (setsockopt(sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on))) {
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return -1;
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}
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}
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return sock;
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}
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