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/**
* Copyright (C) ARM Limited 2014-2016. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include "Command.h"
#include <fcntl.h>
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include "Logging.h"
#include "SessionData.h"
static int getUid(const char *const name, const char *const tmpDir, uid_t *const uid) {
// Lookups may fail when using a different libc or a statically compiled executable
char gatorTemp[32];
snprintf(gatorTemp, sizeof(gatorTemp), "%s/gator_temp", tmpDir);
const int fd = open(gatorTemp, 600, O_CREAT | O_CLOEXEC);
if (fd < 0) {
return false;
}
close(fd);
char cmd[128];
snprintf(cmd, sizeof(cmd), "chown %s %s || rm %s", name, gatorTemp, gatorTemp);
const int pid = fork();
if (pid < 0) {
logg.logError("fork failed");
handleException();
}
if (pid == 0) {
execlp("sh", "sh", "-c", cmd, NULL);
exit(-1);
}
while ((waitpid(pid, NULL, 0) < 0) && (errno == EINTR));
struct stat st;
int result = -1;
if (stat(gatorTemp, &st) != 0) {
return false;
}
result = st.st_uid;
unlink(gatorTemp);
*uid = result;
return true;
}
static bool getUid(const char *const name, uid_t *const uid, gid_t *const gid) {
// Look up the username
struct passwd *const user = getpwnam(name);
if (user != NULL) {
*uid = user->pw_uid;
*gid = user->pw_gid;
return true;
}
// Unable to get the user without getpwanm, so create a unique uid by adding a fixed number to the pid
*gid = 0x484560f8 + getpid();
// Are we on Linux
if (access("/tmp", W_OK) == 0) {
return getUid(name, "/tmp", uid);
}
// Are we on android
if (access("/data", W_OK) == 0) {
return getUid(name, "/data", uid);
}
return false;
}
void *commandThread(void *) {
prctl(PR_SET_NAME, (unsigned long)&"gatord-command", 0, 0, 0);
const char *const name = gSessionData.mCaptureUser == NULL ? "nobody" : gSessionData.mCaptureUser;
uid_t uid;
gid_t gid;
if (!getUid(name, &uid, &gid)) {
logg.logError("Unable to look up the user %s, please double check that the user exists", name);
handleException();
}
sleep(3);
char buf[1<<8];
int pipefd[2];
if (pipe_cloexec(pipefd) != 0) {
logg.logError("pipe failed");
handleException();
}
const int pid = fork();
if (pid < 0) {
logg.logError("fork failed");
handleException();
}
if (pid == 0) {
buf[0] = '\0';
close(pipefd[0]);
// Gator runs at a high priority, reset the priority to the default
if (setpriority(PRIO_PROCESS, syscall(__NR_gettid), 0) == -1) {
snprintf(buf, sizeof(buf), "setpriority failed");
goto fail_exit;
}
if (setgroups(1, &gid) != 0) {
snprintf(buf, sizeof(buf), "setgroups failed");
goto fail_exit;
}
if (setresgid(gid, gid, gid) != 0) {
snprintf(buf, sizeof(buf), "setresgid failed");
goto fail_exit;
}
if (setresuid(uid, uid, uid) != 0) {
snprintf(buf, sizeof(buf), "setresuid failed");
goto fail_exit;
}
{
const char *const path = gSessionData.mCaptureWorkingDir == NULL ? "/" : gSessionData.mCaptureWorkingDir;
if (chdir(path) != 0) {
snprintf(buf, sizeof(buf), "Unable to cd to %s, please verify the directory exists and is accessible to %s", path, name);
goto fail_exit;
}
}
execlp("sh", "sh", "-c", gSessionData.mCaptureCommand, NULL);
snprintf(buf, sizeof(buf), "execv failed");
fail_exit:
if (buf[0] != '\0') {
const ssize_t bytes = write(pipefd[1], buf, sizeof(buf));
// Can't do anything if this fails
(void)bytes;
}
exit(-1);
}
close(pipefd[1]);
const ssize_t bytes = read(pipefd[0], buf, sizeof(buf));
if (bytes > 0) {
logg.logError("%s", buf);
handleException();
}
close(pipefd[0]);
return NULL;
}
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