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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.
*/
#ifdef HAVE_SECCOMP
#include "firejail.h"
#include "../include/seccomp.h"
// install protocol filter
void protocol_filter(const char *fname) {
#ifndef SYS_socket
if (arg_debug)
printf("No support for --protocol on this platform\n");
return;
#else
assert(fname);
// check file
struct stat s;
if (stat(fname, &s) == -1) {
fprintf(stderr, "Error: cannot read protocol filter file\n");
exit(1);
}
int size = s.st_size;
// read filter
struct sock_filter filter[32]; // big enough
memset(&filter[0], 0, sizeof(filter));
int src = open(fname, O_RDONLY);
int rd = 0;
while (rd < size) {
int rv = read(src, (unsigned char *) filter + rd, size - rd);
if (rv == -1) {
fprintf(stderr, "Error: cannot read %s file\n", fname);
exit(1);
}
rd += rv;
}
close(src);
// install filter
unsigned short entries = (unsigned short) size / (unsigned short) sizeof(struct sock_filter);
struct sock_fprog prog = {
.len = entries,
.filter = filter,
};
if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog) || prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
fprintf(stderr, "Warning: seccomp disabled, it requires a Linux kernel version 3.5 or newer.\n");
return;
}
#endif
}
void protocol_filter_save(void) {
// save protocol filter configuration in PROTOCOL_CFG
fs_build_mnt_dir();
FILE *fp = fopen(RUN_PROTOCOL_CFG, "w");
if (!fp)
errExit("fopen");
fprintf(fp, "%s\n", cfg.protocol);
SET_PERMS_STREAM(fp, 0, 0, 0600);
fclose(fp);
}
void protocol_filter_load(const char *fname) {
assert(fname);
// read protocol filter configuration from PROTOCOL_CFG
FILE *fp = fopen(fname, "r");
if (!fp)
return;
const int MAXBUF = 4098;
char buf[MAXBUF];
if (fgets(buf, MAXBUF, fp) == NULL) {
// empty file
fclose(fp);
return;
}
fclose(fp);
char *ptr = strchr(buf, '\n');
if (ptr)
*ptr = '\0';
cfg.protocol = strdup(buf);
if (!cfg.protocol)
errExit("strdup");
}
// --protocol.print
void protocol_print_filter_name(const char *name) {
EUID_ASSERT();
(void) name;
#ifdef SYS_socket
if (!name || strlen(name) == 0) {
fprintf(stderr, "Error: invalid sandbox name\n");
exit(1);
}
pid_t pid;
if (name2pid(name, &pid)) {
fprintf(stderr, "Error: cannot find sandbox %s\n", name);
exit(1);
}
protocol_print_filter(pid);
#else
fprintf(stderr, "Warning: --protocol not supported on this platform\n");
return;
#endif
}
// --protocol.print
void protocol_print_filter(pid_t pid) {
EUID_ASSERT();
(void) pid;
#ifdef SYS_socket
// if the pid is that of a firejail process, use the pid of the first child process
EUID_ROOT();
char *comm = pid_proc_comm(pid);
EUID_USER();
if (comm) {
if (strcmp(comm, "firejail") == 0) {
pid_t child;
if (find_child(pid, &child) == 0) {
pid = child;
}
}
free(comm);
}
// check privileges for non-root users
uid_t uid = getuid();
if (uid != 0) {
uid_t sandbox_uid = pid_get_uid(pid);
if (uid != sandbox_uid) {
fprintf(stderr, "Error: permission denied.\n");
exit(1);
}
}
// find the seccomp filter
EUID_ROOT();
char *fname;
if (asprintf(&fname, "/proc/%d/root%s", pid, RUN_PROTOCOL_CFG) == -1)
errExit("asprintf");
struct stat s;
if (stat(fname, &s) == -1) {
printf("Cannot access seccomp filter.\n");
exit(1);
}
// read and print the filter
protocol_filter_load(fname);
free(fname);
if (cfg.protocol)
printf("%s\n", cfg.protocol);
exit(0);
#else
fprintf(stderr, "Warning: --protocol not supported on this platform\n");
return;
#endif
}
#endif // HAVE_SECCOMP
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