1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_NET_SCM_H
3#define __LINUX_NET_SCM_H
4
5#include <linux/limits.h>
6#include <linux/net.h>
7#include <linux/cred.h>
8#include <linux/file.h>
9#include <linux/security.h>
10#include <linux/pid.h>
11#include <linux/nsproxy.h>
12#include <linux/sched/signal.h>
13#include <net/compat.h>
14
15/* Well, we should have at least one descriptor open
16 * to accept passed FDs 8)
17 */
18#define SCM_MAX_FD	253
19
20struct scm_creds {
21	u32	pid;
22	kuid_t	uid;
23	kgid_t	gid;
24};
25
26struct scm_fp_list {
27	short			count;
28	short			count_unix;
29	short			max;
30	struct user_struct	*user;
31	struct file		*fp[SCM_MAX_FD];
32};
33
34struct scm_cookie {
35	struct pid		*pid;		/* Skb credentials */
36	struct scm_fp_list	*fp;		/* Passed files		*/
37	struct scm_creds	creds;		/* Skb credentials	*/
38#ifdef CONFIG_SECURITY_NETWORK
39	u32			secid;		/* Passed security ID 	*/
40#endif
41};
42
43void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm);
44void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm);
45int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm);
46void __scm_destroy(struct scm_cookie *scm);
47struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl);
48
49#ifdef CONFIG_SECURITY_NETWORK
50static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
51{
52	security_socket_getpeersec_dgram(sock, NULL, &scm->secid);
53}
54#else
55static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
56{ }
57#endif /* CONFIG_SECURITY_NETWORK */
58
59static __inline__ void scm_set_cred(struct scm_cookie *scm,
60				    struct pid *pid, kuid_t uid, kgid_t gid)
61{
62	scm->pid  = get_pid(pid);
63	scm->creds.pid = pid_vnr(pid);
64	scm->creds.uid = uid;
65	scm->creds.gid = gid;
66}
67
68static __inline__ void scm_destroy_cred(struct scm_cookie *scm)
69{
70	put_pid(scm->pid);
71	scm->pid  = NULL;
72}
73
74static __inline__ void scm_destroy(struct scm_cookie *scm)
75{
76	scm_destroy_cred(scm);
77	if (scm->fp)
78		__scm_destroy(scm);
79}
80
81static __inline__ int scm_send(struct socket *sock, struct msghdr *msg,
82			       struct scm_cookie *scm, bool forcecreds)
83{
84	memset(scm, 0, sizeof(*scm));
85	scm->creds.uid = INVALID_UID;
86	scm->creds.gid = INVALID_GID;
87	if (forcecreds)
88		scm_set_cred(scm, task_tgid(current), current_uid(), current_gid());
89	unix_get_peersec_dgram(sock, scm);
90	if (msg->msg_controllen <= 0)
91		return 0;
92	return __scm_send(sock, msg, scm);
93}
94
95#ifdef CONFIG_SECURITY_NETWORK
96static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
97{
98	char *secdata;
99	u32 seclen;
100	int err;
101
102	if (test_bit(SOCK_PASSSEC, &sock->flags)) {
103		err = security_secid_to_secctx(scm->secid, &secdata, &seclen);
104
105		if (!err) {
106			put_cmsg(msg, SOL_SOCKET, SCM_SECURITY, seclen, secdata);
107			security_release_secctx(secdata, seclen);
108		}
109	}
110}
111
112static inline bool scm_has_secdata(struct socket *sock)
113{
114	return test_bit(SOCK_PASSSEC, &sock->flags);
115}
116#else
117static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
118{ }
119
120static inline bool scm_has_secdata(struct socket *sock)
121{
122	return false;
123}
124#endif /* CONFIG_SECURITY_NETWORK */
125
126static __inline__ void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm)
127{
128	struct file *pidfd_file = NULL;
129	int len, pidfd;
130
131	/* put_cmsg() doesn't return an error if CMSG is truncated,
132	 * that's why we need to opencode these checks here.
133	 */
134	if (msg->msg_flags & MSG_CMSG_COMPAT)
135		len = sizeof(struct compat_cmsghdr) + sizeof(int);
136	else
137		len = sizeof(struct cmsghdr) + sizeof(int);
138
139	if (msg->msg_controllen < len) {
140		msg->msg_flags |= MSG_CTRUNC;
141		return;
142	}
143
144	if (!scm->pid)
145		return;
146
147	pidfd = pidfd_prepare(scm->pid, 0, &pidfd_file);
148
149	if (put_cmsg(msg, SOL_SOCKET, SCM_PIDFD, sizeof(int), &pidfd)) {
150		if (pidfd_file) {
151			put_unused_fd(pidfd);
152			fput(pidfd_file);
153		}
154
155		return;
156	}
157
158	if (pidfd_file)
159		fd_install(pidfd, pidfd_file);
160}
161
162static inline bool __scm_recv_common(struct socket *sock, struct msghdr *msg,
163				     struct scm_cookie *scm, int flags)
164{
165	if (!msg->msg_control) {
166		if (test_bit(SOCK_PASSCRED, &sock->flags) ||
167		    test_bit(SOCK_PASSPIDFD, &sock->flags) ||
168		    scm->fp || scm_has_secdata(sock))
169			msg->msg_flags |= MSG_CTRUNC;
170		scm_destroy(scm);
171		return false;
172	}
173
174	if (test_bit(SOCK_PASSCRED, &sock->flags)) {
175		struct user_namespace *current_ns = current_user_ns();
176		struct ucred ucreds = {
177			.pid = scm->creds.pid,
178			.uid = from_kuid_munged(current_ns, scm->creds.uid),
179			.gid = from_kgid_munged(current_ns, scm->creds.gid),
180		};
181		put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(ucreds), &ucreds);
182	}
183
184	scm_passec(sock, msg, scm);
185
186	if (scm->fp)
187		scm_detach_fds(msg, scm);
188
189	return true;
190}
191
192static inline void scm_recv(struct socket *sock, struct msghdr *msg,
193			    struct scm_cookie *scm, int flags)
194{
195	if (!__scm_recv_common(sock, msg, scm, flags))
196		return;
197
198	scm_destroy_cred(scm);
199}
200
201static inline void scm_recv_unix(struct socket *sock, struct msghdr *msg,
202				 struct scm_cookie *scm, int flags)
203{
204	if (!__scm_recv_common(sock, msg, scm, flags))
205		return;
206
207	if (test_bit(SOCK_PASSPIDFD, &sock->flags))
208		scm_pidfd_recv(msg, scm);
209
210	scm_destroy_cred(scm);
211}
212
213static inline int scm_recv_one_fd(struct file *f, int __user *ufd,
214				  unsigned int flags)
215{
216	if (!ufd)
217		return -EFAULT;
218	return receive_fd(f, ufd, flags);
219}
220
221#endif /* __LINUX_NET_SCM_H */
222
223