1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
|
/*
* 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 <thread>
#include <cutils/sockets.h>
#include <private/android_filesystem_config.h>
#include <private/android_logger.h>
#include "LogBuffer.h"
#include "LogListener.h"
#include "LogPermissions.h"
LogListener::LogListener(LogBuffer* buf) : socket_(GetLogSocket()), logbuf_(buf) {}
bool LogListener::StartListener() {
if (socket_ <= 0) {
return false;
}
auto thread = std::thread(&LogListener::ThreadFunction, this);
thread.detach();
return true;
}
void LogListener::ThreadFunction() {
prctl(PR_SET_NAME, "logd.writer");
while (true) {
HandleData();
}
}
void LogListener::HandleData() {
// + 1 to ensure null terminator if MAX_PAYLOAD buffer is received
__attribute__((uninitialized)) char
buffer[sizeof(android_log_header_t) + LOGGER_ENTRY_MAX_PAYLOAD + 1];
struct iovec iov = {buffer, sizeof(buffer) - 1};
alignas(4) char control[CMSG_SPACE(sizeof(struct ucred))];
struct msghdr hdr = {
nullptr, 0, &iov, 1, control, sizeof(control), 0,
};
ssize_t n = recvmsg(socket_, &hdr, 0);
if (n <= (ssize_t)(sizeof(android_log_header_t))) {
return;
}
// To clear the entire buffer would be safe, but this contributes to 1.68%
// overhead under logging load. We are safe because we check counts, but
// still need to clear null terminator
buffer[n] = 0;
struct ucred* cred = nullptr;
struct cmsghdr* cmsg = CMSG_FIRSTHDR(&hdr);
while (cmsg != nullptr) {
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 == nullptr) {
return;
}
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;
}
android_log_header_t* header =
reinterpret_cast<android_log_header_t*>(buffer);
log_id_t logId = static_cast<log_id_t>(header->id);
if (/* logId < LOG_ID_MIN || */ logId >= LOG_ID_MAX ||
logId == LOG_ID_KERNEL) {
return;
}
if (logId == LOG_ID_SECURITY) {
if (!__android_log_security()) {
return;
}
if (!clientCanWriteSecurityLog(cred->uid, cred->gid, cred->pid)) {
return;
}
}
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.
logbuf_->Log(logId, header->realtime, cred->uid, cred->pid, header->tid, msg,
((size_t)n <= UINT16_MAX) ? (uint16_t)n : UINT16_MAX);
}
int LogListener::GetLogSocket() {
static const char socketName[] = "logdw";
int sock = android_get_control_socket(socketName);
if (sock < 0) { // logd started up in init.sh
sock = socket_local_server(
socketName, ANDROID_SOCKET_NAMESPACE_RESERVED, SOCK_DGRAM);
int on = 1;
if (setsockopt(sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on))) {
return -1;
}
}
return sock;
}
|
