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/*
* Copyright (C) 2014-2022 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.
*/
/*
struct sock_filter filter[] = {
VALIDATE_ARCHITECTURE,
EXAMINE_SYSCALL,
ONLY(SYS_socket),
EXAMINE_ARGUMENT(0), // allow only AF_INET and AF_INET6, drop everything else
WHITELIST(AF_INET),
WHITELIST(AF_INET6),
WHITELIST(AF_PACKET),
RETURN_ERRNO(ENOTSUP)
};
struct sock_fprog prog = {
.len = (unsigned short)(sizeof(filter) / sizeof(filter[0])),
.filter = filter,
};
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
perror("prctl(NO_NEW_PRIVS)");
return 1;
}
if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
perror("prctl");
return 1;
}
*/
#include "fseccomp.h"
#include "../include/seccomp.h"
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/socket.h>
static char *protocol[] = {
"unix",
"inet",
"inet6",
"netlink",
"packet",
"bluetooth",
NULL
};
#ifdef SYS_socket
static struct sock_filter protocol_filter_command[] = {
WHITELIST(AF_UNIX),
WHITELIST(AF_INET),
WHITELIST(AF_INET6),
WHITELIST(AF_NETLINK),
WHITELIST(AF_PACKET),
WHITELIST(AF_BLUETOOTH)
};
#endif
// Note: protocol[] and protocol_filter_command are synchronized
// command length
struct sock_filter whitelist[] = {
WHITELIST(AF_UNIX)
};
unsigned whitelist_len = sizeof(whitelist) / sizeof(struct sock_filter);
#ifdef SYS_socket
static struct sock_filter *find_protocol_domain(const char *p) {
int i = 0;
while (protocol[i] != NULL) {
if (strcmp(protocol[i], p) == 0)
return &protocol_filter_command[i * whitelist_len];
i++;
}
return NULL;
}
#endif
void protocol_print(void) {
#ifndef SYS_socket
if (!arg_quiet)
fprintf(stderr, "Warning fseccomp: firejail --protocol not supported on this platform\n");
return;
#endif
int i = 0;
while (protocol[i] != NULL) {
printf("%s, ", protocol[i]);
i++;
}
printf("\n");
}
// install protocol filter
void protocol_build_filter(const char *prlist, const char *fname) {
assert(prlist);
assert(fname);
#ifndef SYS_socket
if (!arg_quiet)
fprintf(stderr, "Warning fseccomp: --protocol not supported on this platform\n");
return;
#else
// build the filter
struct sock_filter filter[32]; // big enough
memset(&filter[0], 0, sizeof(filter));
uint8_t *ptr = (uint8_t *) &filter[0];
// header
struct sock_filter filter_start[] = {
#if defined __x86_64__
/* check for native arch */
BPF_STMT(BPF_LD+BPF_W+BPF_ABS, (offsetof(struct seccomp_data, arch))),
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, ARCH_NR, 1 + 2 + 1, 0),
/* i386 filter */
EXAMINE_SYSCALL, // 1
// checking SYS_socket only: filtering SYS_socketcall not possible with seccomp
ONLY(359), // 1 + 2
BPF_JUMP(BPF_JMP+BPF_JA+BPF_K, (3 + 1 + 3 + 2), 0, 0), // 1 + 2 + 1
#else
#warning 32 bit protocol filter not implemented yet for your architecture
#endif
VALIDATE_ARCHITECTURE, // 3
EXAMINE_SYSCALL, // 3 + 1
#if defined __x86_64__
HANDLE_X32, // 3 + 1 + 3
#endif
ONLY(SYS_socket), // 3 + 1 (+ 3) + 2
EXAMINE_ARGUMENT(0) // 3 + 1 (+ 3) + 2 + 1
};
memcpy(ptr, &filter_start[0], sizeof(filter_start));
ptr += sizeof(filter_start);
// parse list and add commands
char *tmplist = strdup(prlist);
if (!tmplist)
errExit("strdup");
char *token = strtok(tmplist, ",");
if (!token)
errExit("strtok");
while (token) {
struct sock_filter *domain = find_protocol_domain(token);
if (domain == NULL) {
fprintf(stderr, "Error fseccomp: %s is not a valid protocol\n", token);
exit(1);
}
memcpy(ptr, domain, whitelist_len * sizeof(struct sock_filter));
ptr += whitelist_len * sizeof(struct sock_filter);
token = strtok(NULL, ",");
}
free(tmplist);
// add end of filter
struct sock_filter filter_end[] = {
RETURN_ERRNO(ENOTSUP)
};
memcpy(ptr, &filter_end[0], sizeof(filter_end));
ptr += sizeof(filter_end);
// save filter to file
int dst = open(fname, O_CREAT|O_WRONLY|O_TRUNC, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
if (dst < 0) {
fprintf(stderr, "Error fseccomp: cannot open %s file\n", fname);
exit(1);
}
int size = (int) ((uintptr_t) ptr - (uintptr_t) (filter));
int written = 0;
while (written < size) {
int rv = write(dst, (unsigned char *) filter + written, size - written);
if (rv == -1) {
fprintf(stderr, "Error fseccomp: cannot write %s file\n", fname);
exit(1);
}
written += rv;
}
close(dst);
#endif // SYS_socket
}
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