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1// SPDX-License-Identifier: GPL-2.02/*3 * Seccomp BPF example using a macro-based generator.4 *5 * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>6 * Author: Will Drewry <wad@chromium.org>7 *8 * The code may be used by anyone for any purpose,9 * and can serve as a starting point for developing10 * applications using prctl(PR_ATTACH_SECCOMP_FILTER).11 */12 13#include <linux/filter.h>14#include <linux/seccomp.h>15#include <linux/unistd.h>16#include <stdio.h>17#include <string.h>18#include <sys/prctl.h>19#include <unistd.h>20 21#include "bpf-helper.h"22 23#ifndef PR_SET_NO_NEW_PRIVS24#define PR_SET_NO_NEW_PRIVS 3825#endif26 27int main(int argc, char **argv)28{29 struct bpf_labels l = {30 .count = 0,31 };32 static const char msg1[] = "Please type something: ";33 static const char msg2[] = "You typed: ";34 char buf[256];35 struct sock_filter filter[] = {36 /* TODO: LOAD_SYSCALL_NR(arch) and enforce an arch */37 LOAD_SYSCALL_NR,38 SYSCALL(__NR_exit, ALLOW),39 SYSCALL(__NR_exit_group, ALLOW),40 SYSCALL(__NR_write, JUMP(&l, write_fd)),41 SYSCALL(__NR_read, JUMP(&l, read)),42 DENY, /* Don't passthrough into a label */43 44 LABEL(&l, read),45 ARG(0),46 JNE(STDIN_FILENO, DENY),47 ARG(1),48 JNE((unsigned long)buf, DENY),49 ARG(2),50 JGE(sizeof(buf), DENY),51 ALLOW,52 53 LABEL(&l, write_fd),54 ARG(0),55 JEQ(STDOUT_FILENO, JUMP(&l, write_buf)),56 JEQ(STDERR_FILENO, JUMP(&l, write_buf)),57 DENY,58 59 LABEL(&l, write_buf),60 ARG(1),61 JEQ((unsigned long)msg1, JUMP(&l, msg1_len)),62 JEQ((unsigned long)msg2, JUMP(&l, msg2_len)),63 JEQ((unsigned long)buf, JUMP(&l, buf_len)),64 DENY,65 66 LABEL(&l, msg1_len),67 ARG(2),68 JLT(sizeof(msg1), ALLOW),69 DENY,70 71 LABEL(&l, msg2_len),72 ARG(2),73 JLT(sizeof(msg2), ALLOW),74 DENY,75 76 LABEL(&l, buf_len),77 ARG(2),78 JLT(sizeof(buf), ALLOW),79 DENY,80 };81 struct sock_fprog prog = {82 .filter = filter,83 .len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),84 };85 ssize_t bytes;86 bpf_resolve_jumps(&l, filter, sizeof(filter)/sizeof(*filter));87 88 if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {89 perror("prctl(NO_NEW_PRIVS)");90 return 1;91 }92 93 if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {94 perror("prctl(SECCOMP)");95 return 1;96 }97 syscall(__NR_write, STDOUT_FILENO, msg1, strlen(msg1));98 bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf)-1);99 bytes = (bytes > 0 ? bytes : 0);100 syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2));101 syscall(__NR_write, STDERR_FILENO, buf, bytes);102 /* Now get killed */103 syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2)+2);104 return 0;105}106