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/*
* Copyright (C) 2014-2018 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.
*/
//
// Firejail access database inplementation
//
// The database is a simple list of users allowed to run firejail SUID executable
// It is usually stored in /etc/firejail/firejail.users
// One username per line in the file
#include "../include/common.h"
#include "../include/firejail_user.h"
#include <sys/types.h>
#include <pwd.h>
#define MAXBUF 4098
// minimum values for uid and gid extracted from /etc/login.defs
int uid_min = 0;
int gid_min = 0;
static void init_uid_gid_min(void) {
if (uid_min != 0 && gid_min != 0)
return;
// read the real values from login.def
FILE *fp = fopen("/etc/login.defs", "r");
if (!fp)
goto errexit;
char buf[MAXBUF];
while (fgets(buf, MAXBUF, fp)) {
// comments
if (*buf == '#')
continue;
// skip empty space
char *ptr = buf;
while (*ptr == ' ' || *ptr == '\t')
ptr++;
if (strncmp(ptr, "UID_MIN", 7) == 0) {
int rv = sscanf(ptr + 7, "%d", &uid_min);
if (rv != 1 || uid_min < 0) {
fclose(fp);
goto errexit;
}
}
else if (strncmp(ptr, "GID_MIN", 7) == 0) {
int rv = sscanf(ptr + 7, "%d", &gid_min);
if (rv != 1 || gid_min < 0) {
fclose(fp);
goto errexit;
}
}
if (uid_min != 0 && gid_min != 0)
break;
}
fclose(fp);
if (uid_min == 0 || gid_min == 0)
goto errexit;
//printf("uid_min %d, gid_min %d\n", uid_min, gid_min);
return;
errexit:
fprintf(stderr, "Error: cannot read UID_MIN and/or GID_MIN from /etc/login.defs, using 1000 by default\n");
uid_min = 1000;
gid_min = 1000;
}
static inline char *get_fname(void) {
char *fname;
if (asprintf(&fname, "%s/firejail.users", SYSCONFDIR) == -1)
errExit("asprintf");
return fname;
}
// returns 1 if the user is found in the database or if the database was not created
int firejail_user_check(const char *name) {
assert(name);
init_uid_gid_min();
// root is allowed to run firejail by default
if (strcmp(name, "root") == 0)
return 1;
// user nobody is never allowed
if (strcmp(name, "root") == 0)
return 0;
// check file existence
char *fname = get_fname();
if (access(fname, F_OK)) {
free(fname);
return 1; // assume the user doesn't care about access checking
}
FILE *fp = fopen(fname, "r");
free(fname);
if (!fp)
return 0;
char buf[MAXBUF];
while (fgets(buf, MAXBUF, fp)) {
// lines starting with # are comments
if (*buf == '#')
continue;
// remove \n
char *ptr = strchr(buf, '\n');
if (ptr)
*ptr = '\0';
// compare
if (strcmp(buf, name) == 0) {
fclose(fp);
return 1;
}
}
fclose(fp);
return 0;
}
// add a user to the database
void firejail_user_add(const char *name) {
assert(name);
// is this a real user?
struct passwd *pw = getpwnam(name);
if (!pw) {
fprintf(stderr, "Error: user %s not found on this system.\n", name);
exit(1);
}
// check the user is not already in the database
char *fname = get_fname();
assert(fname);
if (access(fname, F_OK) == 0) {
if (firejail_user_check(name)) {
printf("User %s already in the database\n", name);
return;
}
}
printf("%s created\n", fname);
FILE *fp = fopen(fname, "a+");
if (!fp) {
fprintf(stderr, "Error: cannot open %s\n", fname);
perror("fopen");
free(fname);
return;
}
free(fname);
fprintf(fp, "%s\n", name);
fclose(fp);
}
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