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/*
* Copyright (C) 2014-2016 Firejail Authors
*
* This file is part of firejail project
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "firejail.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <grp.h>
#include <pwd.h>
void check_user(int argc, char **argv) {
EUID_ASSERT();
int i;
char *user = NULL;
int found = 0;
for (i = 1; i < argc; i++) {
// check options
if (strcmp(argv[i], "--") == 0)
break;
if (strncmp(argv[i], "--", 2) != 0)
break;
// check user option
if (strncmp(argv[i], "--user=", 7) == 0) {
found = 1;
user = argv[i] + 7;
break;
}
}
if (!found)
return;
// check root
if (getuid() != 0) {
fprintf(stderr, "Error: you need to be root to use --user command line option\n");
exit(1);
}
// switch user
struct passwd *pw = getpwnam(user);
if (!pw) {
fprintf(stderr, "Error: cannot find user %s\n", user);
exit(1);
}
printf("Switching to user %s, UID %d, GID %d\n", user, pw->pw_uid, pw->pw_gid);
int rv = initgroups(user, pw->pw_gid);
if (rv == -1) {
perror("initgroups");
fprintf(stderr, "Error: cannot switch to user %s\n", user);
}
rv = setgid(pw->pw_gid);
if (rv == -1) {
perror("setgid");
fprintf(stderr, "Error: cannot switch to user %s\n", user);
}
rv = setuid(pw->pw_uid);
if (rv == -1) {
perror("setuid");
fprintf(stderr, "Error: cannot switch to user %s\n", user);
}
// build the new command line
int len = 0;
for (i = 0; i < argc; i++) {
len += strlen(argv[i]) + 1; // + ' '
}
char *cmd = malloc(len + 1); // + '\0'
if (!cmd)
errExit("malloc");
char *ptr = cmd;
int first = 1;
for (i = 0; i < argc; i++) {
if (strncmp(argv[i], "--user=", 7) == 0 && first) {
first = 0;
continue;
}
ptr += sprintf(ptr, "%s ", argv[i]);
}
// run command
char *a[4];
a[0] = "/bin/bash";
a[1] = "-c";
a[2] = cmd;
a[3] = NULL;
execvp(a[0], a);
perror("execvp");
exit(1);
}
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