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 
12 char _license[] SEC("license") = "GPL";
13 
14 #define DUMMY_STORAGE_VALUE 0xdeadbeef
15 
16 int monitored_pid = 0;
17 int inode_storage_result = -1;
18 int sk_storage_result = -1;
19 int task_storage_result = -1;
20 
21 struct local_storage {
22 	struct inode *exec_inode;
23 	__u32 value;
24 };
25 
26 struct {
27 	__uint(type, BPF_MAP_TYPE_INODE_STORAGE);
28 	__uint(map_flags, BPF_F_NO_PREALLOC);
29 	__type(key, int);
30 	__type(value, struct local_storage);
31 } inode_storage_map SEC(".maps");
32 
33 struct {
34 	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
35 	__uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
36 	__type(key, int);
37 	__type(value, struct local_storage);
38 } sk_storage_map SEC(".maps");
39 
40 struct {
41 	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
42 	__uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
43 	__type(key, int);
44 	__type(value, struct local_storage);
45 } sk_storage_map2 SEC(".maps");
46 
47 struct {
48 	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
49 	__uint(map_flags, BPF_F_NO_PREALLOC);
50 	__type(key, int);
51 	__type(value, struct local_storage);
52 } task_storage_map SEC(".maps");
53 
54 struct {
55 	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
56 	__uint(map_flags, BPF_F_NO_PREALLOC);
57 	__type(key, int);
58 	__type(value, struct local_storage);
59 } task_storage_map2 SEC(".maps");
60 
61 SEC("lsm/inode_unlink")
62 int BPF_PROG(unlink_hook, struct inode *dir, struct dentry *victim)
63 {
64 	__u32 pid = bpf_get_current_pid_tgid() >> 32;
65 	struct bpf_local_storage *local_storage;
66 	struct local_storage *storage;
67 	struct task_struct *task;
68 	bool is_self_unlink;
69 
70 	if (pid != monitored_pid)
71 		return 0;
72 
73 	task = bpf_get_current_task_btf();
74 	if (!task)
75 		return 0;
76 
77 	task_storage_result = -1;
78 
79 	storage = bpf_task_storage_get(&task_storage_map, task, 0, 0);
80 	if (!storage)
81 		return 0;
82 
83 	/* Don't let an executable delete itself */
84 	is_self_unlink = storage->exec_inode == victim->d_inode;
85 
86 	storage = bpf_task_storage_get(&task_storage_map2, task, 0,
87 				       BPF_LOCAL_STORAGE_GET_F_CREATE);
88 	if (!storage || storage->value)
89 		return 0;
90 
91 	if (bpf_task_storage_delete(&task_storage_map, task))
92 		return 0;
93 
94 	/* Ensure that the task_storage_map is disconnected from the storage.
95 	 * The storage memory should not be freed back to the
96 	 * bpf_mem_alloc.
97 	 */
98 	local_storage = task->bpf_storage;
99 	if (!local_storage || local_storage->smap)
100 		return 0;
101 
102 	task_storage_result = 0;
103 
104 	return is_self_unlink ? -EPERM : 0;
105 }
106 
107 SEC("lsm.s/inode_rename")
108 int BPF_PROG(inode_rename, struct inode *old_dir, struct dentry *old_dentry,
109 	     struct inode *new_dir, struct dentry *new_dentry,
110 	     unsigned int flags)
111 {
112 	struct local_storage *storage;
113 	int err;
114 
115 	/* new_dentry->d_inode can be NULL when the inode is renamed to a file
116 	 * that did not exist before. The helper should be able to handle this
117 	 * NULL pointer.
118 	 */
119 	bpf_inode_storage_get(&inode_storage_map, new_dentry->d_inode, 0,
120 			      BPF_LOCAL_STORAGE_GET_F_CREATE);
121 
122 	storage = bpf_inode_storage_get(&inode_storage_map, old_dentry->d_inode,
123 					0, 0);
124 	if (!storage)
125 		return 0;
126 
127 	if (storage->value != DUMMY_STORAGE_VALUE)
128 		inode_storage_result = -1;
129 
130 	err = bpf_inode_storage_delete(&inode_storage_map, old_dentry->d_inode);
131 	if (!err)
132 		inode_storage_result = err;
133 
134 	return 0;
135 }
136 
137 SEC("lsm.s/socket_bind")
138 int BPF_PROG(socket_bind, struct socket *sock, struct sockaddr *address,
139 	     int addrlen)
140 {
141 	__u32 pid = bpf_get_current_pid_tgid() >> 32;
142 	struct local_storage *storage;
143 	struct sock *sk = sock->sk;
144 
145 	if (pid != monitored_pid || !sk)
146 		return 0;
147 
148 	storage = bpf_sk_storage_get(&sk_storage_map, sk, 0, 0);
149 	if (!storage)
150 		return 0;
151 
152 	sk_storage_result = -1;
153 	if (storage->value != DUMMY_STORAGE_VALUE)
154 		return 0;
155 
156 	/* This tests that we can associate multiple elements
157 	 * with the local storage.
158 	 */
159 	storage = bpf_sk_storage_get(&sk_storage_map2, sk, 0,
160 				     BPF_LOCAL_STORAGE_GET_F_CREATE);
161 	if (!storage)
162 		return 0;
163 
164 	if (bpf_sk_storage_delete(&sk_storage_map2, sk))
165 		return 0;
166 
167 	storage = bpf_sk_storage_get(&sk_storage_map2, sk, 0,
168 				     BPF_LOCAL_STORAGE_GET_F_CREATE);
169 	if (!storage)
170 		return 0;
171 
172 	if (bpf_sk_storage_delete(&sk_storage_map, sk))
173 		return 0;
174 
175 	/* Ensure that the sk_storage_map is disconnected from the storage. */
176 	if (!sk->sk_bpf_storage || sk->sk_bpf_storage->smap)
177 		return 0;
178 
179 	sk_storage_result = 0;
180 	return 0;
181 }
182 
183 SEC("lsm.s/socket_post_create")
184 int BPF_PROG(socket_post_create, struct socket *sock, int family, int type,
185 	     int protocol, int kern)
186 {
187 	__u32 pid = bpf_get_current_pid_tgid() >> 32;
188 	struct local_storage *storage;
189 	struct sock *sk = sock->sk;
190 
191 	if (pid != monitored_pid || !sk)
192 		return 0;
193 
194 	storage = bpf_sk_storage_get(&sk_storage_map, sk, 0,
195 				     BPF_LOCAL_STORAGE_GET_F_CREATE);
196 	if (!storage)
197 		return 0;
198 
199 	storage->value = DUMMY_STORAGE_VALUE;
200 
201 	return 0;
202 }
203 
204 /* This uses the local storage to remember the inode of the binary that a
205  * process was originally executing.
206  */
207 SEC("lsm.s/bprm_committed_creds")
208 void BPF_PROG(exec, struct linux_binprm *bprm)
209 {
210 	__u32 pid = bpf_get_current_pid_tgid() >> 32;
211 	struct local_storage *storage;
212 
213 	if (pid != monitored_pid)
214 		return;
215 
216 	storage = bpf_task_storage_get(&task_storage_map,
217 				       bpf_get_current_task_btf(), 0,
218 				       BPF_LOCAL_STORAGE_GET_F_CREATE);
219 	if (storage)
220 		storage->exec_inode = bprm->file->f_inode;
221 
222 	storage = bpf_inode_storage_get(&inode_storage_map, bprm->file->f_inode,
223 					0, BPF_LOCAL_STORAGE_GET_F_CREATE);
224 	if (!storage)
225 		return;
226 
227 	storage->value = DUMMY_STORAGE_VALUE;
228 }
229