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      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 #include <string.h>
     21 
     22 #include <private/android_filesystem_config.h>
     23 
     24 #include "LogCommand.h"
     25 
     26 LogCommand::LogCommand(const char *cmd) : 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 
     42 static 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 
     60 bool 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