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
20 struct local_storage {
21 struct inode *exec_inode;
22 __u32 value;
23 };
24
25 struct {
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
32 struct {
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
39 struct {
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
46 struct {
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
53 SEC("lsm/inode_unlink")
BPF_PROG(unlink_hook,struct inode * dir,struct dentry * victim)54 int 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
75 SEC("lsm.s/inode_rename")
BPF_PROG(inode_rename,struct inode * old_dir,struct dentry * old_dentry,struct inode * new_dir,struct dentry * new_dentry,unsigned int flags)76 int 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
106 SEC("lsm.s/socket_bind")
BPF_PROG(socket_bind,struct socket * sock,struct sockaddr * address,int addrlen)107 int 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
144 SEC("lsm.s/socket_post_create")
BPF_PROG(socket_post_create,struct socket * sock,int family,int type,int protocol,int kern)145 int 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 */
167 SEC("lsm.s/bprm_committed_creds")
BPF_PROG(exec,struct linux_binprm * bprm)168 void 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 }
189