106 lines
2.5 KiB
C
106 lines
2.5 KiB
C
|
// SPDX-License-Identifier: GPL-2.0
|
||
|
|
/*
|
||
|
|
* Seccomp BPF example using a macro-based generator.
|
||
|
|
*
|
||
|
|
* Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
|
||
|
|
* Author: Will Drewry <wad@chromium.org>
|
||
|
|
*
|
||
|
|
* The code may be used by anyone for any purpose,
|
||
|
|
* and can serve as a starting point for developing
|
||
|
|
* applications using prctl(PR_ATTACH_SECCOMP_FILTER).
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <linux/filter.h>
|
||
|
|
#include <linux/seccomp.h>
|
||
|
|
#include <linux/unistd.h>
|
||
|
|
#include <stdio.h>
|
||
|
|
#include <string.h>
|
||
|
|
#include <sys/prctl.h>
|
||
|
|
#include <unistd.h>
|
||
|
|
|
||
|
|
#include "bpf-helper.h"
|
||
|
|
|
||
|
|
#ifndef PR_SET_NO_NEW_PRIVS
|
||
|
|
#define PR_SET_NO_NEW_PRIVS 38
|
||
|
|
#endif
|
||
|
|
|
||
|
|
int main(int argc, char **argv)
|
||
|
|
{
|
||
|
|
struct bpf_labels l = {
|
||
|
|
.count = 0,
|
||
|
|
};
|
||
|
|
static const char msg1[] = "Please type something: ";
|
||
|
|
static const char msg2[] = "You typed: ";
|
||
|
|
char buf[256];
|
||
|
|
struct sock_filter filter[] = {
|
||
|
|
/* TODO: LOAD_SYSCALL_NR(arch) and enforce an arch */
|
||
|
|
LOAD_SYSCALL_NR,
|
||
|
|
SYSCALL(__NR_exit, ALLOW),
|
||
|
|
SYSCALL(__NR_exit_group, ALLOW),
|
||
|
|
SYSCALL(__NR_write, JUMP(&l, write_fd)),
|
||
|
|
SYSCALL(__NR_read, JUMP(&l, read)),
|
||
|
|
DENY, /* Don't passthrough into a label */
|
||
|
|
|
||
|
|
LABEL(&l, read),
|
||
|
|
ARG(0),
|
||
|
|
JNE(STDIN_FILENO, DENY),
|
||
|
|
ARG(1),
|
||
|
|
JNE((unsigned long)buf, DENY),
|
||
|
|
ARG(2),
|
||
|
|
JGE(sizeof(buf), DENY),
|
||
|
|
ALLOW,
|
||
|
|
|
||
|
|
LABEL(&l, write_fd),
|
||
|
|
ARG(0),
|
||
|
|
JEQ(STDOUT_FILENO, JUMP(&l, write_buf)),
|
||
|
|
JEQ(STDERR_FILENO, JUMP(&l, write_buf)),
|
||
|
|
DENY,
|
||
|
|
|
||
|
|
LABEL(&l, write_buf),
|
||
|
|
ARG(1),
|
||
|
|
JEQ((unsigned long)msg1, JUMP(&l, msg1_len)),
|
||
|
|
JEQ((unsigned long)msg2, JUMP(&l, msg2_len)),
|
||
|
|
JEQ((unsigned long)buf, JUMP(&l, buf_len)),
|
||
|
|
DENY,
|
||
|
|
|
||
|
|
LABEL(&l, msg1_len),
|
||
|
|
ARG(2),
|
||
|
|
JLT(sizeof(msg1), ALLOW),
|
||
|
|
DENY,
|
||
|
|
|
||
|
|
LABEL(&l, msg2_len),
|
||
|
|
ARG(2),
|
||
|
|
JLT(sizeof(msg2), ALLOW),
|
||
|
|
DENY,
|
||
|
|
|
||
|
|
LABEL(&l, buf_len),
|
||
|
|
ARG(2),
|
||
|
|
JLT(sizeof(buf), ALLOW),
|
||
|
|
DENY,
|
||
|
|
};
|
||
|
|
struct sock_fprog prog = {
|
||
|
|
.filter = filter,
|
||
|
|
.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
|
||
|
|
};
|
||
|
|
ssize_t bytes;
|
||
|
|
bpf_resolve_jumps(&l, filter, sizeof(filter)/sizeof(*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(SECCOMP)");
|
||
|
|
return 1;
|
||
|
|
}
|
||
|
|
syscall(__NR_write, STDOUT_FILENO, msg1, strlen(msg1));
|
||
|
|
bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf)-1);
|
||
|
|
bytes = (bytes > 0 ? bytes : 0);
|
||
|
|
syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2));
|
||
|
|
syscall(__NR_write, STDERR_FILENO, buf, bytes);
|
||
|
|
/* Now get killed */
|
||
|
|
syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2)+2);
|
||
|
|
return 0;
|
||
|
|
}
|