LogCommand.cpp revision 57a0af93133ad0d190a79372b702653f96b99fe8 
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 <errno.h>
18#include <stdio.h>
19#include <stdlib.h>
20
21#include <private/android_filesystem_config.h>
22
23#include "LogCommand.h"
24
25LogCommand::LogCommand(const char *cmd)
26        : FrameworkCommand(cmd) {
27}
28
29// gets a list of supplementary group IDs associated with
30// the socket peer.  This is implemented by opening
31// /proc/PID/status and look for the "Group:" line.
32//
33// This function introduces races especially since status
34// can change 'shape' while reading, the net result is err
35// on lack of permission.
36//
37// Race-free alternative is to introduce pairs of sockets
38// and threads for each command and reading, one each that
39// has open permissions, and one that has restricted
40// permissions.
41
42static bool groupIsLog(char *buf) {
43    char *ptr;
44    static const char ws[] = " \n";
45    bool ret = false;
46
47    for (buf = strtok_r(buf, ws, &ptr); buf; buf = strtok_r(NULL, ws, &ptr)) {
48        errno = 0;
49        gid_t Gid = strtol(buf, NULL, 10);
50        if (errno != 0) {
51            return false;
52        }
53        if (Gid == AID_LOG) {
54            ret = true;
55        }
56    }
57    return ret;
58}
59
60bool clientHasLogCredentials(SocketClient * cli) {
61    uid_t uid = cli->getUid();
62    if (uid == AID_ROOT) {
63        return true;
64    }
65
66    gid_t gid = cli->getGid();
67    if ((gid == AID_ROOT) || (gid == AID_SYSTEM) || (gid == AID_LOG)) {
68        return true;
69    }
70
71    // FYI We will typically be here for 'adb logcat'
72    bool ret = false;
73
74    char filename[1024];
75    snprintf(filename, sizeof(filename), "/proc/%d/status", cli->getPid());
76
77    FILE *file = fopen(filename, "r");
78    if (!file) {
79        return ret;
80    }
81
82    bool foundGid = false;
83    bool foundUid = false;
84
85    char line[1024];
86    while (fgets(line, sizeof(line), file)) {
87        static const char groups_string[] = "Groups:\t";
88        static const char uid_string[] = "Uid:\t";
89        static const char gid_string[] = "Gid:\t";
90
91        if (strncmp(groups_string, line, strlen(groups_string)) == 0) {
92            ret = groupIsLog(line + strlen(groups_string));
93            if (!ret) {
94                break;
95            }
96        } else if (strncmp(uid_string, line, strlen(uid_string)) == 0) {
97            uid_t u[4] = { (uid_t) -1, (uid_t) -1, (uid_t) -1, (uid_t) -1};
98
99            sscanf(line + strlen(uid_string), "%u\t%u\t%u\t%u",
100                   &u[0], &u[1], &u[2], &u[3]);
101
102            // Protect against PID reuse by checking that the UID is the same
103            if ((uid != u[0]) || (uid != u[1]) || (uid != u[2]) || (uid != u[3])) {
104                ret = false;
105                break;
106            }
107            foundUid = true;
108        } else if (strncmp(gid_string, line, strlen(gid_string)) == 0) {
109            gid_t g[4] = { (gid_t) -1, (gid_t) -1, (gid_t) -1, (gid_t) -1};
110
111            sscanf(line + strlen(gid_string), "%u\t%u\t%u\t%u",
112                   &g[0], &g[1], &g[2], &g[3]);
113
114            // Protect against PID reuse by checking that the GID is the same
115            if ((gid != g[0]) || (gid != g[1]) || (gid != g[2]) || (gid != g[3])) {
116                ret = false;
117                break;
118            }
119            foundGid = true;
120        }
121    }
122
123    fclose(file);
124
125    if (!foundGid || !foundUid) {
126        ret = false;
127    }
128
129    return ret;
130}
131