LogListener.cpp revision 4690640760983dffa9b28e257aac293da4282e85 
1/*
2 * Copyright (C) 2012-2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <limits.h>
18#include <sys/cdefs.h>
19#include <sys/prctl.h>
20#include <sys/socket.h>
21#include <sys/types.h>
22#include <sys/un.h>
23#include <unistd.h>
24
25#include <cutils/sockets.h>
26#include <log/logger.h>
27#include <private/android_filesystem_config.h>
28#include <private/android_logger.h>
29
30#include "LogListener.h"
31#include "LogUtils.h"
32
33LogListener::LogListener(LogBuffer *buf, LogReader *reader) :
34        SocketListener(getLogSocket(), false),
35        logbuf(buf),
36        reader(reader) {
37}
38
39bool LogListener::onDataAvailable(SocketClient *cli) {
40    static bool name_set;
41    if (!name_set) {
42        prctl(PR_SET_NAME, "logd.writer");
43        name_set = true;
44    }
45
46    char buffer[sizeof_log_id_t + sizeof(uint16_t) + sizeof(log_time)
47        + LOGGER_ENTRY_MAX_PAYLOAD];
48    struct iovec iov = { buffer, sizeof(buffer) };
49
50    char control[CMSG_SPACE(sizeof(struct ucred))] __aligned(4);
51    struct msghdr hdr = {
52        NULL,
53        0,
54        &iov,
55        1,
56        control,
57        sizeof(control),
58        0,
59    };
60
61    int socket = cli->getSocket();
62
63    // To clear the entire buffer is secure/safe, but this contributes to 1.68%
64    // overhead under logging load. We are safe because we check counts.
65    // memset(buffer, 0, sizeof(buffer));
66    ssize_t n = recvmsg(socket, &hdr, 0);
67    if (n <= (ssize_t)(sizeof(android_log_header_t))) {
68        return false;
69    }
70
71    struct ucred *cred = NULL;
72
73    struct cmsghdr *cmsg = CMSG_FIRSTHDR(&hdr);
74    while (cmsg != NULL) {
75        if (cmsg->cmsg_level == SOL_SOCKET
76                && cmsg->cmsg_type  == SCM_CREDENTIALS) {
77            cred = (struct ucred *)CMSG_DATA(cmsg);
78            break;
79        }
80        cmsg = CMSG_NXTHDR(&hdr, cmsg);
81    }
82
83    if (cred == NULL) {
84        return false;
85    }
86
87    if (cred->uid == AID_LOGD) {
88        // ignore log messages we send to ourself.
89        // Such log messages are often generated by libraries we depend on
90        // which use standard Android logging.
91        return false;
92    }
93
94    android_log_header_t *header = reinterpret_cast<android_log_header_t *>(buffer);
95    if (/* header->id < LOG_ID_MIN || */ header->id >= LOG_ID_MAX || header->id == LOG_ID_KERNEL) {
96        return false;
97    }
98
99    if ((header->id == LOG_ID_SECURITY) &&
100            (!__android_log_security() ||
101             !clientHasLogCredentials(cred->uid, cred->gid, cred->pid))) {
102        return false;
103    }
104
105    char *msg = ((char *)buffer) + sizeof(android_log_header_t);
106    n -= sizeof(android_log_header_t);
107
108    // NB: hdr.msg_flags & MSG_TRUNC is not tested, silently passing a
109    // truncated message to the logs.
110
111    if (logbuf->log((log_id_t)header->id, header->realtime,
112            cred->uid, cred->pid, header->tid, msg,
113            ((size_t) n <= USHRT_MAX) ? (unsigned short) n : USHRT_MAX) >= 0) {
114        reader->notifyNewLog();
115    }
116
117    return true;
118}
119
120int LogListener::getLogSocket() {
121    static const char socketName[] = "logdw";
122    int sock = android_get_control_socket(socketName);
123
124    if (sock < 0) {
125        sock = socket_local_server(socketName,
126                                   ANDROID_SOCKET_NAMESPACE_RESERVED,
127                                   SOCK_DGRAM);
128    }
129
130    int on = 1;
131    if (setsockopt(sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)) < 0) {
132        return -1;
133    }
134    return sock;
135}
136