1// SPDX-License-Identifier: GPL-2.0
  2
  3/*
  4 * Copyright 2020 Google LLC.
  5 */
  6
  7#include "vmlinux.h"
  8#include <errno.h>
  9#include <bpf/bpf_helpers.h>
 10#include <bpf/bpf_tracing.h>
 11
 12u32 monitored_pid = 0;
 13
 14struct {
 15	__uint(type, BPF_MAP_TYPE_RINGBUF);
 16	__uint(max_entries, 1 << 12);
 17} ringbuf SEC(".maps");
 18
 19char _license[] SEC("license") = "GPL";
 20
 21bool use_ima_file_hash;
 22bool enable_bprm_creds_for_exec;
 23bool enable_kernel_read_file;
 24bool test_deny;
 25
 26static void ima_test_common(struct file *file)
 27{
 28	u64 ima_hash = 0;
 29	u64 *sample;
 30	int ret;
 31	u32 pid;
 32
 33	pid = bpf_get_current_pid_tgid() >> 32;
 34	if (pid == monitored_pid) {
 35		if (!use_ima_file_hash)
 36			ret = bpf_ima_inode_hash(file->f_inode, &ima_hash,
 37						 sizeof(ima_hash));
 38		else
 39			ret = bpf_ima_file_hash(file, &ima_hash,
 40						sizeof(ima_hash));
 41		if (ret < 0 || ima_hash == 0)
 42			return;
 43
 44		sample = bpf_ringbuf_reserve(&ringbuf, sizeof(u64), 0);
 45		if (!sample)
 46			return;
 47
 48		*sample = ima_hash;
 49		bpf_ringbuf_submit(sample, 0);
 50	}
 51
 52	return;
 53}
 54
 55static int ima_test_deny(void)
 56{
 57	u32 pid;
 58
 59	pid = bpf_get_current_pid_tgid() >> 32;
 60	if (pid == monitored_pid && test_deny)
 61		return -EPERM;
 62
 63	return 0;
 64}
 65
 66SEC("lsm.s/bprm_committed_creds")
 67void BPF_PROG(bprm_committed_creds, struct linux_binprm *bprm)
 68{
 69	ima_test_common(bprm->file);
 70}
 71
 72SEC("lsm.s/bprm_creds_for_exec")
 73int BPF_PROG(bprm_creds_for_exec, struct linux_binprm *bprm)
 74{
 75	if (!enable_bprm_creds_for_exec)
 76		return 0;
 77
 78	ima_test_common(bprm->file);
 79	return 0;
 80}
 81
 82SEC("lsm.s/kernel_read_file")
 83int BPF_PROG(kernel_read_file, struct file *file, enum kernel_read_file_id id,
 84	     bool contents)
 85{
 86	int ret;
 87
 88	if (!enable_kernel_read_file)
 89		return 0;
 90
 91	if (!contents)
 92		return 0;
 93
 94	if (id != READING_POLICY)
 95		return 0;
 96
 97	ret = ima_test_deny();
 98	if (ret < 0)
 99		return ret;
100
101	ima_test_common(file);
102	return 0;
103}