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
 12char _license[] SEC("license") = "GPL";
 13
 14#define DUMMY_STORAGE_VALUE 0xdeadbeef
 15
 16int monitored_pid = 0;
 17int inode_storage_result = -1;
 18int sk_storage_result = -1;
 19
 20struct local_storage {
 21	struct inode *exec_inode;
 22	__u32 value;
 23};
 24
 25struct {
 26	__uint(type, BPF_MAP_TYPE_INODE_STORAGE);
 27	__uint(map_flags, BPF_F_NO_PREALLOC);
 28	__type(key, int);
 29	__type(value, struct local_storage);
 30} inode_storage_map SEC(".maps");
 31
 32struct {
 33	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
 34	__uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
 35	__type(key, int);
 36	__type(value, struct local_storage);
 37} sk_storage_map SEC(".maps");
 38
 39struct {
 40	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
 41	__uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
 42	__type(key, int);
 43	__type(value, struct local_storage);
 44} sk_storage_map2 SEC(".maps");
 45
 46struct {
 47	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
 48	__uint(map_flags, BPF_F_NO_PREALLOC);
 49	__type(key, int);
 50	__type(value, struct local_storage);
 51} task_storage_map SEC(".maps");
 52
 53SEC("lsm/inode_unlink")
 54int BPF_PROG(unlink_hook, struct inode *dir, struct dentry *victim)
 55{
 56	__u32 pid = bpf_get_current_pid_tgid() >> 32;
 57	struct local_storage *storage;
 58	bool is_self_unlink;
 59
 60	if (pid != monitored_pid)
 61		return 0;
 62
 63	storage = bpf_task_storage_get(&task_storage_map,
 64				       bpf_get_current_task_btf(), 0, 0);
 65	if (storage) {
 66		/* Don't let an executable delete itself */
 67		is_self_unlink = storage->exec_inode == victim->d_inode;
 68		if (is_self_unlink)
 69			return -EPERM;
 70	}
 71
 72	return 0;
 73}
 74
 75SEC("lsm.s/inode_rename")
 76int BPF_PROG(inode_rename, struct inode *old_dir, struct dentry *old_dentry,
 77	     struct inode *new_dir, struct dentry *new_dentry,
 78	     unsigned int flags)
 79{
 80	__u32 pid = bpf_get_current_pid_tgid() >> 32;
 81	struct local_storage *storage;
 82	int err;
 83
 84	/* new_dentry->d_inode can be NULL when the inode is renamed to a file
 85	 * that did not exist before. The helper should be able to handle this
 86	 * NULL pointer.
 87	 */
 88	bpf_inode_storage_get(&inode_storage_map, new_dentry->d_inode, 0,
 89			      BPF_LOCAL_STORAGE_GET_F_CREATE);
 90
 91	storage = bpf_inode_storage_get(&inode_storage_map, old_dentry->d_inode,
 92					0, 0);
 93	if (!storage)
 94		return 0;
 95
 96	if (storage->value != DUMMY_STORAGE_VALUE)
 97		inode_storage_result = -1;
 98
 99	err = bpf_inode_storage_delete(&inode_storage_map, old_dentry->d_inode);
100	if (!err)
101		inode_storage_result = err;
102
103	return 0;
104}
105
106SEC("lsm.s/socket_bind")
107int BPF_PROG(socket_bind, struct socket *sock, struct sockaddr *address,
108	     int addrlen)
109{
110	__u32 pid = bpf_get_current_pid_tgid() >> 32;
111	struct local_storage *storage;
112	int err;
113
114	if (pid != monitored_pid)
115		return 0;
116
117	storage = bpf_sk_storage_get(&sk_storage_map, sock->sk, 0,
118				     BPF_LOCAL_STORAGE_GET_F_CREATE);
119	if (!storage)
120		return 0;
121
122	if (storage->value != DUMMY_STORAGE_VALUE)
123		sk_storage_result = -1;
124
125	/* This tests that we can associate multiple elements
126	 * with the local storage.
127	 */
128	storage = bpf_sk_storage_get(&sk_storage_map2, sock->sk, 0,
129				     BPF_LOCAL_STORAGE_GET_F_CREATE);
130	if (!storage)
131		return 0;
132
133	err = bpf_sk_storage_delete(&sk_storage_map, sock->sk);
134	if (err)
135		return 0;
136
137	err = bpf_sk_storage_delete(&sk_storage_map2, sock->sk);
138	if (!err)
139		sk_storage_result = err;
140
141	return 0;
142}
143
144SEC("lsm.s/socket_post_create")
145int BPF_PROG(socket_post_create, struct socket *sock, int family, int type,
146	     int protocol, int kern)
147{
148	__u32 pid = bpf_get_current_pid_tgid() >> 32;
149	struct local_storage *storage;
150
151	if (pid != monitored_pid)
152		return 0;
153
154	storage = bpf_sk_storage_get(&sk_storage_map, sock->sk, 0,
155				     BPF_LOCAL_STORAGE_GET_F_CREATE);
156	if (!storage)
157		return 0;
158
159	storage->value = DUMMY_STORAGE_VALUE;
160
161	return 0;
162}
163
164/* This uses the local storage to remember the inode of the binary that a
165 * process was originally executing.
166 */
167SEC("lsm.s/bprm_committed_creds")
168void BPF_PROG(exec, struct linux_binprm *bprm)
169{
170	__u32 pid = bpf_get_current_pid_tgid() >> 32;
171	struct local_storage *storage;
172
173	if (pid != monitored_pid)
174		return;
175
176	storage = bpf_task_storage_get(&task_storage_map,
177				       bpf_get_current_task_btf(), 0,
178				       BPF_LOCAL_STORAGE_GET_F_CREATE);
179	if (storage)
180		storage->exec_inode = bprm->file->f_inode;
181
182	storage = bpf_inode_storage_get(&inode_storage_map, bprm->file->f_inode,
183					0, BPF_LOCAL_STORAGE_GET_F_CREATE);
184	if (!storage)
185		return;
186
187	storage->value = DUMMY_STORAGE_VALUE;
188}