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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"
char *seccomp_check_list(const char *str) {
assert(str);
if (strlen(str) == 0) {
fprintf(stderr, "Error: empty syscall lists are not allowed\n");
exit(1);
}
int len = strlen(str) + 1;
char *rv = malloc(len);
if (!rv)
errExit("malloc");
memset(rv, 0, len);
const char *ptr1 = str;
char *ptr2 = rv;
while (*ptr1 != '\0') {
if (isalnum(*ptr1) || *ptr1 == '_' || *ptr1 == ',' || *ptr1 == ':')
*ptr2++ = *ptr1++;
else {
fprintf(stderr, "Error: invalid syscall list\n");
exit(1);
}
}
return rv;
}
int seccomp_load(const char *fname) {
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;
unsigned short entries = (unsigned short) size / (unsigned short) sizeof(struct sock_filter);
//printf("size %d, entries %d\n", s.st_size, entries);
// read filter
struct sock_filter filter[entries];
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
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 1;
}
return 0;
}
// i386 filter installed on amd64 architectures
void seccomp_filter_32(void) {
if (arg_debug)
printf("Build secondary 32-bit filter\n");
// build the seccomp filter as a regular user
int rv = sbox_run(SBOX_USER | SBOX_CAPS_NONE | SBOX_SECCOMP, 4,
PATH_FSECCOMP, "secondary", "32", RUN_SECCOMP_I386);
if (rv)
exit(rv);
if (seccomp_load(RUN_SECCOMP_I386) == 0) {
if (arg_debug)
printf("Dual i386/amd64 seccomp filter configured\n");
}
}
// amd64 filter installed on i386 architectures
void seccomp_filter_64(void) {
if (arg_debug)
printf("Build secondary 64-bit filter\n");
// build the seccomp filter as a regular user
int rv = sbox_run(SBOX_USER | SBOX_CAPS_NONE | SBOX_SECCOMP, 4,
PATH_FSECCOMP, "secondary", "64", RUN_SECCOMP_AMD64);
if (rv)
exit(rv);
if (seccomp_load(RUN_SECCOMP_AMD64) == 0) {
if (arg_debug)
printf("Dual i386/amd64 seccomp filter configured\n");
}
}
// drop filter for seccomp option
int seccomp_filter_drop(int enforce_seccomp) {
// default seccomp
if (cfg.seccomp_list_drop == NULL && cfg.seccomp_list == NULL) {
#if defined(__x86_64__)
seccomp_filter_32();
#endif
#if defined(__i386__)
seccomp_filter_64();
#endif
if (arg_debug)
printf("Build default seccomp filter\n");
// build the seccomp filter as a regular user
int rv;
if (arg_allow_debuggers)
rv = sbox_run(SBOX_USER | SBOX_CAPS_NONE | SBOX_SECCOMP, 4,
PATH_FSECCOMP, "default", RUN_SECCOMP_CFG, "allow-debuggers");
else
rv = sbox_run(SBOX_USER | SBOX_CAPS_NONE | SBOX_SECCOMP, 3,
PATH_FSECCOMP, "default", RUN_SECCOMP_CFG);
if (rv)
exit(rv);
}
// default seccomp filter with additional drop list
else if (cfg.seccomp_list && cfg.seccomp_list_drop == NULL) {
#if defined(__x86_64__)
seccomp_filter_32();
#endif
#if defined(__i386__)
seccomp_filter_64();
#endif
if (arg_debug)
printf("Build default+drop seccomp filter\n");
// build the seccomp filter as a regular user
int rv;
if (arg_allow_debuggers)
rv = sbox_run(SBOX_USER | SBOX_CAPS_NONE | SBOX_SECCOMP, 6,
PATH_FSECCOMP, "default", "drop", RUN_SECCOMP_CFG, cfg.seccomp_list, "allow-debuggers");
else
rv = sbox_run(SBOX_USER | SBOX_CAPS_NONE | SBOX_SECCOMP, 5,
PATH_FSECCOMP, "default", "drop", RUN_SECCOMP_CFG, cfg.seccomp_list);
if (rv)
exit(rv);
}
// drop list without defaults - secondary filters are not installed
else if (cfg.seccomp_list == NULL && cfg.seccomp_list_drop) {
if (arg_debug)
printf("Build drop seccomp filter\n");
// build the seccomp filter as a regular user
int rv;
if (arg_allow_debuggers)
rv = sbox_run(SBOX_USER | SBOX_CAPS_NONE | SBOX_SECCOMP, 5,
PATH_FSECCOMP, "drop", RUN_SECCOMP_CFG, cfg.seccomp_list_drop, "allow-debuggers");
else
rv = sbox_run(SBOX_USER | SBOX_CAPS_NONE | SBOX_SECCOMP, 4,
PATH_FSECCOMP, "drop", RUN_SECCOMP_CFG, cfg.seccomp_list_drop);
if (rv)
exit(rv);
}
else {
assert(0);
}
// load the filter
if (seccomp_load(RUN_SECCOMP_CFG) == 0) {
if (arg_debug)
printf("seccomp filter configured\n");
}
else if (enforce_seccomp) {
fprintf(stderr, "Error: a seccomp-enabled Linux kernel is required, exiting...\n");
exit(1);
}
if (arg_debug)
sbox_run(SBOX_USER | SBOX_CAPS_NONE | SBOX_SECCOMP, 3,
PATH_FSECCOMP, "print", RUN_SECCOMP_CFG);
return seccomp_load(RUN_SECCOMP_CFG);
}
// keep filter for seccomp option
int seccomp_filter_keep(void) {
if (arg_debug)
printf("Build drop seccomp filter\n");
// build the seccomp filter as a regular user
int rv = sbox_run(SBOX_USER | SBOX_CAPS_NONE | SBOX_SECCOMP, 4,
PATH_FSECCOMP, "keep", RUN_SECCOMP_CFG, cfg.seccomp_list_keep);
if (rv)
exit(rv);
if (arg_debug)
printf("seccomp filter configured\n");
return seccomp_load(RUN_SECCOMP_CFG);
}
void seccomp_print_filter(pid_t pid) {
EUID_ASSERT();
// 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_SECCOMP_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 - run this as root, the user doesn't have access
int rv = sbox_run(SBOX_ROOT | SBOX_SECCOMP, 3,
PATH_FSECCOMP, "print", fname);
if (rv)
exit(rv);
free(fname);
exit(0);
}
#endif // HAVE_SECCOMP
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