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/*
* Copyright (C) 2014-2017 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 "fseccomp.h"
#include "../include/seccomp.h"
#include <sys/syscall.h>
static struct sock_filter *filter = NULL;
static int filter_cnt = 0;
static void load_seccomp(const char *fname) {
assert(fname);
// open filter file
int fd = open(fname, O_RDONLY);
if (fd == -1)
goto errexit;
// calculate the number of entries
int size = lseek(fd, 0, SEEK_END);
if (size == -1)
goto errexit;
if (lseek(fd, 0 , SEEK_SET) == -1)
goto errexit;
unsigned short entries = (unsigned short) size / (unsigned short) sizeof(struct sock_filter);
filter_cnt = entries;
// read filter
filter = malloc(size);
if (filter == NULL)
goto errexit;
memset(filter, 0, size);
int rd = 0;
while (rd < size) {
int rv = read(fd, (unsigned char *) filter + rd, size - rd);
if (rv == -1)
goto errexit;
rd += rv;
}
// close file
close(fd);
return;
errexit:
fprintf(stderr, "Error fseccomp: cannot read %s\n", fname);
exit(1);
}
static int detect_filter_type(void) {
// the filter ishould already be load in filter variable
assert(filter);
printf("SECCOMP Filter\n");
// testing for main seccomp filter, protocol, mdwe - platform architecture
const struct sock_filter start_main[] = {
VALIDATE_ARCHITECTURE,
#if defined(__x86_64__)
EXAMINE_SYSCALL,
HANDLE_X32
#else
EXAMINE_SYSCALL
#endif
};
if (memcmp(&start_main[0], filter, sizeof(start_main)) == 0) {
printf(" VALIDATE_ARCHITECTURE\n");
printf(" EXAMINE_SYSCALL\n");
#if defined(__x86_64__)
printf(" HANDLE_X32\n");
#endif
return sizeof(start_main) / sizeof(struct sock_filter);
}
// testing for secondary 64 bit filter
const struct sock_filter start_secondary_64[] = {
VALIDATE_ARCHITECTURE_64,
EXAMINE_SYSCALL,
};
if (memcmp(&start_secondary_64[0], filter, sizeof(start_secondary_64)) == 0) {
printf(" VALIDATE_ARCHITECTURE_64\n");
printf(" EXAMINE_SYSCALL\n");
return sizeof(start_secondary_64) / sizeof(struct sock_filter);
}
// testing for secondary 32 bit filter
const struct sock_filter start_secondary_32[] = {
VALIDATE_ARCHITECTURE_32,
EXAMINE_SYSCALL,
};
if (memcmp(&start_secondary_32[0], filter, sizeof(start_secondary_32)) == 0) {
printf(" VALIDATE_ARCHITECTURE_32\n");
printf(" EXAMINE_SYSCALL\n");
return sizeof(start_secondary_32) / sizeof(struct sock_filter);
}
const struct sock_filter start_secondary_block[] = {
VALIDATE_ARCHITECTURE_KILL,
#if defined(__x86_64__)
EXAMINE_SYSCALL,
HANDLE_X32_KILL,
#else
EXAMINE_SYSCALL
#endif
};
if (memcmp(&start_secondary_block[0], filter, sizeof(start_secondary_block)) == 0) {
printf(" VALIDATE_ARCHITECTURE_KILL\n");
printf(" EXAMINE_SYSCALL\n");
#if defined(__x86_64__)
printf(" HANDLE_X32_KILL\n");
#endif
return sizeof(start_secondary_block) / sizeof(struct sock_filter);
}
return 0; // filter unrecognized
}
// debug filter
void filter_print(const char *fname) {
assert(fname);
load_seccomp(fname);
int i = detect_filter_type();
if (i == 0) {
printf("Invalid seccomp filter %s\n", fname);
return;
}
// loop trough the rest of commands
while (i < filter_cnt) {
// minimal parsing!
struct sock_filter *s = (struct sock_filter *) &filter[i];
if (s->code == BPF_JMP+BPF_JEQ+BPF_K && (s + 1)->code == BPF_RET+BPF_K && (s + 1)->k == SECCOMP_RET_ALLOW ) {
printf(" WHITELIST %d %s\n", s->k, syscall_find_nr(s->k));
i += 2;
}
else if (s->code == BPF_JMP+BPF_JEQ+BPF_K && (s + 1)->code == BPF_RET+BPF_K && (s + 1)->k == SECCOMP_RET_KILL ) {
printf(" BLACKLIST %d %s\n", s->k, syscall_find_nr(s->k));
i += 2;
}
else if (s->code == BPF_JMP+BPF_JEQ+BPF_K && (s + 1)->code == BPF_RET+BPF_K && ((s + 1)->k & ~SECCOMP_RET_DATA) == SECCOMP_RET_ERRNO) {
printf(" BLACKLIST_ERRNO %d %s %d %s\n", s->k, syscall_find_nr(s->k), (s + 1)->k & SECCOMP_RET_DATA, errno_find_nr((s + 1)->k & SECCOMP_RET_DATA));
i += 2;
}
else if (s->code == BPF_RET+BPF_K && (s->k & ~SECCOMP_RET_DATA) == SECCOMP_RET_ERRNO) {
printf(" RETURN_ERRNO %d %s\n", s->k & SECCOMP_RET_DATA, errno_find_nr(s->k & SECCOMP_RET_DATA));
i++;
}
else if (s->code == BPF_RET+BPF_K && s->k == SECCOMP_RET_KILL) {
printf(" KILL_PROCESS\n");
i++;
}
else if (s->code == BPF_RET+BPF_K && s->k == SECCOMP_RET_ALLOW) {
printf(" RETURN_ALLOW\n");
i++;
}
else {
printf(" UNKNOWN ENTRY %x!\n", s->code);
i++;
}
}
}
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