1/* scm.c - Socket level control messages processing.
  2 *
  3 * Author:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
  4 *              Alignment and value checking mods by Craig Metz
  5 *
  6 *		This program is free software; you can redistribute it and/or
  7 *		modify it under the terms of the GNU General Public License
  8 *		as published by the Free Software Foundation; either version
  9 *		2 of the License, or (at your option) any later version.
 10 */
 11
 12#include <linux/module.h>
 13#include <linux/signal.h>
 14#include <linux/capability.h>
 15#include <linux/errno.h>
 16#include <linux/sched.h>
 17#include <linux/mm.h>
 18#include <linux/kernel.h>
 19#include <linux/stat.h>
 20#include <linux/socket.h>
 21#include <linux/file.h>
 22#include <linux/fcntl.h>
 23#include <linux/net.h>
 24#include <linux/interrupt.h>
 25#include <linux/netdevice.h>
 26#include <linux/security.h>
 27#include <linux/pid_namespace.h>
 28#include <linux/pid.h>
 29#include <linux/nsproxy.h>
 30#include <linux/slab.h>
 31
 32#include <asm/uaccess.h>
 33
 34#include <net/protocol.h>
 35#include <linux/skbuff.h>
 36#include <net/sock.h>
 37#include <net/compat.h>
 38#include <net/scm.h>
 39#include <net/cls_cgroup.h>
 40
 41
 42/*
 43 *	Only allow a user to send credentials, that they could set with
 44 *	setu(g)id.
 45 */
 46
 47static __inline__ int scm_check_creds(struct ucred *creds)
 48{
 49	const struct cred *cred = current_cred();
 50	kuid_t uid = make_kuid(cred->user_ns, creds->uid);
 51	kgid_t gid = make_kgid(cred->user_ns, creds->gid);
 52
 53	if (!uid_valid(uid) || !gid_valid(gid))
 54		return -EINVAL;
 55
 56	if ((creds->pid == task_tgid_vnr(current) ||
 57	     ns_capable(task_active_pid_ns(current)->user_ns, CAP_SYS_ADMIN)) &&
 58	    ((uid_eq(uid, cred->uid)   || uid_eq(uid, cred->euid) ||
 59	      uid_eq(uid, cred->suid)) || ns_capable(cred->user_ns, CAP_SETUID)) &&
 60	    ((gid_eq(gid, cred->gid)   || gid_eq(gid, cred->egid) ||
 61	      gid_eq(gid, cred->sgid)) || ns_capable(cred->user_ns, CAP_SETGID))) {
 62	       return 0;
 63	}
 64	return -EPERM;
 65}
 66
 67static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
 68{
 69	int *fdp = (int*)CMSG_DATA(cmsg);
 70	struct scm_fp_list *fpl = *fplp;
 71	struct file **fpp;
 72	int i, num;
 73
 74	num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
 75
 76	if (num <= 0)
 77		return 0;
 78
 79	if (num > SCM_MAX_FD)
 80		return -EINVAL;
 81
 82	if (!fpl)
 83	{
 84		fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
 85		if (!fpl)
 86			return -ENOMEM;
 87		*fplp = fpl;
 88		fpl->count = 0;
 89		fpl->max = SCM_MAX_FD;
 90		fpl->user = NULL;
 91	}
 92	fpp = &fpl->fp[fpl->count];
 93
 94	if (fpl->count + num > fpl->max)
 95		return -EINVAL;
 96
 97	/*
 98	 *	Verify the descriptors and increment the usage count.
 99	 */
100
101	for (i=0; i< num; i++)
102	{
103		int fd = fdp[i];
104		struct file *file;
105
106		if (fd < 0 || !(file = fget_raw(fd)))
107			return -EBADF;
108		*fpp++ = file;
109		fpl->count++;
110	}
111
112	if (!fpl->user)
113		fpl->user = get_uid(current_user());
114
115	return num;
116}
117
118void __scm_destroy(struct scm_cookie *scm)
119{
120	struct scm_fp_list *fpl = scm->fp;
121	int i;
122
123	if (fpl) {
124		scm->fp = NULL;
125		for (i=fpl->count-1; i>=0; i--)
126			fput(fpl->fp[i]);
127		free_uid(fpl->user);
128		kfree(fpl);
129	}
130}
131EXPORT_SYMBOL(__scm_destroy);
132
133int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
134{
135	struct cmsghdr *cmsg;
136	int err;
137
138	for_each_cmsghdr(cmsg, msg) {
139		err = -EINVAL;
140
141		/* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
142		/* The first check was omitted in <= 2.2.5. The reasoning was
143		   that parser checks cmsg_len in any case, so that
144		   additional check would be work duplication.
145		   But if cmsg_level is not SOL_SOCKET, we do not check
146		   for too short ancillary data object at all! Oops.
147		   OK, let's add it...
148		 */
149		if (!CMSG_OK(msg, cmsg))
150			goto error;
151
152		if (cmsg->cmsg_level != SOL_SOCKET)
153			continue;
154
155		switch (cmsg->cmsg_type)
156		{
157		case SCM_RIGHTS:
158			if (!sock->ops || sock->ops->family != PF_UNIX)
159				goto error;
160			err=scm_fp_copy(cmsg, &p->fp);
161			if (err<0)
162				goto error;
163			break;
164		case SCM_CREDENTIALS:
165		{
166			struct ucred creds;
167			kuid_t uid;
168			kgid_t gid;
169			if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
170				goto error;
171			memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred));
172			err = scm_check_creds(&creds);
173			if (err)
174				goto error;
175
176			p->creds.pid = creds.pid;
177			if (!p->pid || pid_vnr(p->pid) != creds.pid) {
178				struct pid *pid;
179				err = -ESRCH;
180				pid = find_get_pid(creds.pid);
181				if (!pid)
182					goto error;
183				put_pid(p->pid);
184				p->pid = pid;
185			}
186
187			err = -EINVAL;
188			uid = make_kuid(current_user_ns(), creds.uid);
189			gid = make_kgid(current_user_ns(), creds.gid);
190			if (!uid_valid(uid) || !gid_valid(gid))
191				goto error;
192
193			p->creds.uid = uid;
194			p->creds.gid = gid;
195			break;
196		}
197		default:
198			goto error;
199		}
200	}
201
202	if (p->fp && !p->fp->count)
203	{
204		kfree(p->fp);
205		p->fp = NULL;
206	}
207	return 0;
208
209error:
210	scm_destroy(p);
211	return err;
212}
213EXPORT_SYMBOL(__scm_send);
214
215int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
216{
217	struct cmsghdr __user *cm
218		= (__force struct cmsghdr __user *)msg->msg_control;
219	struct cmsghdr cmhdr;
220	int cmlen = CMSG_LEN(len);
221	int err;
222
223	if (MSG_CMSG_COMPAT & msg->msg_flags)
224		return put_cmsg_compat(msg, level, type, len, data);
225
226	if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
227		msg->msg_flags |= MSG_CTRUNC;
228		return 0; /* XXX: return error? check spec. */
229	}
230	if (msg->msg_controllen < cmlen) {
231		msg->msg_flags |= MSG_CTRUNC;
232		cmlen = msg->msg_controllen;
233	}
234	cmhdr.cmsg_level = level;
235	cmhdr.cmsg_type = type;
236	cmhdr.cmsg_len = cmlen;
237
238	err = -EFAULT;
239	if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
240		goto out;
241	if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
242		goto out;
243	cmlen = CMSG_SPACE(len);
244	if (msg->msg_controllen < cmlen)
245		cmlen = msg->msg_controllen;
246	msg->msg_control += cmlen;
247	msg->msg_controllen -= cmlen;
248	err = 0;
249out:
250	return err;
251}
252EXPORT_SYMBOL(put_cmsg);
253
254void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
255{
256	struct cmsghdr __user *cm
257		= (__force struct cmsghdr __user*)msg->msg_control;
258
259	int fdmax = 0;
260	int fdnum = scm->fp->count;
261	struct file **fp = scm->fp->fp;
262	int __user *cmfptr;
263	int err = 0, i;
264
265	if (MSG_CMSG_COMPAT & msg->msg_flags) {
266		scm_detach_fds_compat(msg, scm);
267		return;
268	}
269
270	if (msg->msg_controllen > sizeof(struct cmsghdr))
271		fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
272			 / sizeof(int));
273
274	if (fdnum < fdmax)
275		fdmax = fdnum;
276
277	for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
278	     i++, cmfptr++)
279	{
280		struct socket *sock;
281		int new_fd;
282		err = security_file_receive(fp[i]);
283		if (err)
284			break;
285		err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
286					  ? O_CLOEXEC : 0);
287		if (err < 0)
288			break;
289		new_fd = err;
290		err = put_user(new_fd, cmfptr);
291		if (err) {
292			put_unused_fd(new_fd);
293			break;
294		}
295		/* Bump the usage count and install the file. */
296		sock = sock_from_file(fp[i], &err);
297		if (sock) {
298			sock_update_netprioidx(&sock->sk->sk_cgrp_data);
299			sock_update_classid(&sock->sk->sk_cgrp_data);
300		}
301		fd_install(new_fd, get_file(fp[i]));
302	}
303
304	if (i > 0)
305	{
306		int cmlen = CMSG_LEN(i*sizeof(int));
307		err = put_user(SOL_SOCKET, &cm->cmsg_level);
308		if (!err)
309			err = put_user(SCM_RIGHTS, &cm->cmsg_type);
310		if (!err)
311			err = put_user(cmlen, &cm->cmsg_len);
312		if (!err) {
313			cmlen = CMSG_SPACE(i*sizeof(int));
314			if (msg->msg_controllen < cmlen)
315				cmlen = msg->msg_controllen;
316			msg->msg_control += cmlen;
317			msg->msg_controllen -= cmlen;
318		}
319	}
320	if (i < fdnum || (fdnum && fdmax <= 0))
321		msg->msg_flags |= MSG_CTRUNC;
322
323	/*
324	 * All of the files that fit in the message have had their
325	 * usage counts incremented, so we just free the list.
326	 */
327	__scm_destroy(scm);
328}
329EXPORT_SYMBOL(scm_detach_fds);
330
331struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
332{
333	struct scm_fp_list *new_fpl;
334	int i;
335
336	if (!fpl)
337		return NULL;
338
339	new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
340			  GFP_KERNEL);
341	if (new_fpl) {
342		for (i = 0; i < fpl->count; i++)
343			get_file(fpl->fp[i]);
344		new_fpl->max = new_fpl->count;
345		new_fpl->user = get_uid(fpl->user);
346	}
347	return new_fpl;
348}
349EXPORT_SYMBOL(scm_fp_dup);

  1/* scm.c - Socket level control messages processing.
  2 *
  3 * Author:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
  4 *              Alignment and value checking mods by Craig Metz
  5 *
  6 *		This program is free software; you can redistribute it and/or
  7 *		modify it under the terms of the GNU General Public License
  8 *		as published by the Free Software Foundation; either version
  9 *		2 of the License, or (at your option) any later version.
 10 */
 11
 12#include <linux/module.h>
 13#include <linux/signal.h>
 14#include <linux/capability.h>
 15#include <linux/errno.h>
 16#include <linux/sched.h>
 17#include <linux/mm.h>
 18#include <linux/kernel.h>
 19#include <linux/stat.h>
 20#include <linux/socket.h>
 21#include <linux/file.h>
 22#include <linux/fcntl.h>
 23#include <linux/net.h>
 24#include <linux/interrupt.h>
 25#include <linux/netdevice.h>
 26#include <linux/security.h>
 27#include <linux/pid_namespace.h>
 28#include <linux/pid.h>
 29#include <linux/nsproxy.h>
 30#include <linux/slab.h>
 31
 32#include <linux/uaccess.h>
 33
 34#include <net/protocol.h>
 35#include <linux/skbuff.h>
 36#include <net/sock.h>
 37#include <net/compat.h>
 38#include <net/scm.h>
 39#include <net/cls_cgroup.h>
 40
 41
 42/*
 43 *	Only allow a user to send credentials, that they could set with
 44 *	setu(g)id.
 45 */
 46
 47static __inline__ int scm_check_creds(struct ucred *creds)
 48{
 49	const struct cred *cred = current_cred();
 50	kuid_t uid = make_kuid(cred->user_ns, creds->uid);
 51	kgid_t gid = make_kgid(cred->user_ns, creds->gid);
 52
 53	if (!uid_valid(uid) || !gid_valid(gid))
 54		return -EINVAL;
 55
 56	if ((creds->pid == task_tgid_vnr(current) ||
 57	     ns_capable(task_active_pid_ns(current)->user_ns, CAP_SYS_ADMIN)) &&
 58	    ((uid_eq(uid, cred->uid)   || uid_eq(uid, cred->euid) ||
 59	      uid_eq(uid, cred->suid)) || ns_capable(cred->user_ns, CAP_SETUID)) &&
 60	    ((gid_eq(gid, cred->gid)   || gid_eq(gid, cred->egid) ||
 61	      gid_eq(gid, cred->sgid)) || ns_capable(cred->user_ns, CAP_SETGID))) {
 62	       return 0;
 63	}
 64	return -EPERM;
 65}
 66
 67static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
 68{
 69	int *fdp = (int*)CMSG_DATA(cmsg);
 70	struct scm_fp_list *fpl = *fplp;
 71	struct file **fpp;
 72	int i, num;
 73
 74	num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
 75
 76	if (num <= 0)
 77		return 0;
 78
 79	if (num > SCM_MAX_FD)
 80		return -EINVAL;
 81
 82	if (!fpl)
 83	{
 84		fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
 85		if (!fpl)
 86			return -ENOMEM;
 87		*fplp = fpl;
 88		fpl->count = 0;
 89		fpl->max = SCM_MAX_FD;
 90		fpl->user = NULL;
 91	}
 92	fpp = &fpl->fp[fpl->count];
 93
 94	if (fpl->count + num > fpl->max)
 95		return -EINVAL;
 96
 97	/*
 98	 *	Verify the descriptors and increment the usage count.
 99	 */
100
101	for (i=0; i< num; i++)
102	{
103		int fd = fdp[i];
104		struct file *file;
105
106		if (fd < 0 || !(file = fget_raw(fd)))
107			return -EBADF;
108		*fpp++ = file;
109		fpl->count++;
110	}
111
112	if (!fpl->user)
113		fpl->user = get_uid(current_user());
114
115	return num;
116}
117
118void __scm_destroy(struct scm_cookie *scm)
119{
120	struct scm_fp_list *fpl = scm->fp;
121	int i;
122
123	if (fpl) {
124		scm->fp = NULL;
125		for (i=fpl->count-1; i>=0; i--)
126			fput(fpl->fp[i]);
127		free_uid(fpl->user);
128		kfree(fpl);
129	}
130}
131EXPORT_SYMBOL(__scm_destroy);
132
133int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
134{
135	struct cmsghdr *cmsg;
136	int err;
137
138	for_each_cmsghdr(cmsg, msg) {
139		err = -EINVAL;
140
141		/* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
142		/* The first check was omitted in <= 2.2.5. The reasoning was
143		   that parser checks cmsg_len in any case, so that
144		   additional check would be work duplication.
145		   But if cmsg_level is not SOL_SOCKET, we do not check
146		   for too short ancillary data object at all! Oops.
147		   OK, let's add it...
148		 */
149		if (!CMSG_OK(msg, cmsg))
150			goto error;
151
152		if (cmsg->cmsg_level != SOL_SOCKET)
153			continue;
154
155		switch (cmsg->cmsg_type)
156		{
157		case SCM_RIGHTS:
158			if (!sock->ops || sock->ops->family != PF_UNIX)
159				goto error;
160			err=scm_fp_copy(cmsg, &p->fp);
161			if (err<0)
162				goto error;
163			break;
164		case SCM_CREDENTIALS:
165		{
166			struct ucred creds;
167			kuid_t uid;
168			kgid_t gid;
169			if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
170				goto error;
171			memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred));
172			err = scm_check_creds(&creds);
173			if (err)
174				goto error;
175
176			p->creds.pid = creds.pid;
177			if (!p->pid || pid_vnr(p->pid) != creds.pid) {
178				struct pid *pid;
179				err = -ESRCH;
180				pid = find_get_pid(creds.pid);
181				if (!pid)
182					goto error;
183				put_pid(p->pid);
184				p->pid = pid;
185			}
186
187			err = -EINVAL;
188			uid = make_kuid(current_user_ns(), creds.uid);
189			gid = make_kgid(current_user_ns(), creds.gid);
190			if (!uid_valid(uid) || !gid_valid(gid))
191				goto error;
192
193			p->creds.uid = uid;
194			p->creds.gid = gid;
195			break;
196		}
197		default:
198			goto error;
199		}
200	}
201
202	if (p->fp && !p->fp->count)
203	{
204		kfree(p->fp);
205		p->fp = NULL;
206	}
207	return 0;
208
209error:
210	scm_destroy(p);
211	return err;
212}
213EXPORT_SYMBOL(__scm_send);
214
215int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
216{
217	struct cmsghdr __user *cm
218		= (__force struct cmsghdr __user *)msg->msg_control;
219	struct cmsghdr cmhdr;
220	int cmlen = CMSG_LEN(len);
221	int err;
222
223	if (MSG_CMSG_COMPAT & msg->msg_flags)
224		return put_cmsg_compat(msg, level, type, len, data);
225
226	if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
227		msg->msg_flags |= MSG_CTRUNC;
228		return 0; /* XXX: return error? check spec. */
229	}
230	if (msg->msg_controllen < cmlen) {
231		msg->msg_flags |= MSG_CTRUNC;
232		cmlen = msg->msg_controllen;
233	}
234	cmhdr.cmsg_level = level;
235	cmhdr.cmsg_type = type;
236	cmhdr.cmsg_len = cmlen;
237
238	err = -EFAULT;
239	if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
240		goto out;
241	if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
242		goto out;
243	cmlen = CMSG_SPACE(len);
244	if (msg->msg_controllen < cmlen)
245		cmlen = msg->msg_controllen;
246	msg->msg_control += cmlen;
247	msg->msg_controllen -= cmlen;
248	err = 0;
249out:
250	return err;
251}
252EXPORT_SYMBOL(put_cmsg);
253
254void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
255{
256	struct cmsghdr __user *cm
257		= (__force struct cmsghdr __user*)msg->msg_control;
258
259	int fdmax = 0;
260	int fdnum = scm->fp->count;
261	struct file **fp = scm->fp->fp;
262	int __user *cmfptr;
263	int err = 0, i;
264
265	if (MSG_CMSG_COMPAT & msg->msg_flags) {
266		scm_detach_fds_compat(msg, scm);
267		return;
268	}
269
270	if (msg->msg_controllen > sizeof(struct cmsghdr))
271		fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
272			 / sizeof(int));
273
274	if (fdnum < fdmax)
275		fdmax = fdnum;
276
277	for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
278	     i++, cmfptr++)
279	{
280		struct socket *sock;
281		int new_fd;
282		err = security_file_receive(fp[i]);
283		if (err)
284			break;
285		err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
286					  ? O_CLOEXEC : 0);
287		if (err < 0)
288			break;
289		new_fd = err;
290		err = put_user(new_fd, cmfptr);
291		if (err) {
292			put_unused_fd(new_fd);
293			break;
294		}
295		/* Bump the usage count and install the file. */
296		sock = sock_from_file(fp[i], &err);
297		if (sock) {
298			sock_update_netprioidx(&sock->sk->sk_cgrp_data);
299			sock_update_classid(&sock->sk->sk_cgrp_data);
300		}
301		fd_install(new_fd, get_file(fp[i]));
302	}
303
304	if (i > 0)
305	{
306		int cmlen = CMSG_LEN(i*sizeof(int));
307		err = put_user(SOL_SOCKET, &cm->cmsg_level);
308		if (!err)
309			err = put_user(SCM_RIGHTS, &cm->cmsg_type);
310		if (!err)
311			err = put_user(cmlen, &cm->cmsg_len);
312		if (!err) {
313			cmlen = CMSG_SPACE(i*sizeof(int));
314			if (msg->msg_controllen < cmlen)
315				cmlen = msg->msg_controllen;
316			msg->msg_control += cmlen;
317			msg->msg_controllen -= cmlen;
318		}
319	}
320	if (i < fdnum || (fdnum && fdmax <= 0))
321		msg->msg_flags |= MSG_CTRUNC;
322
323	/*
324	 * All of the files that fit in the message have had their
325	 * usage counts incremented, so we just free the list.
326	 */
327	__scm_destroy(scm);
328}
329EXPORT_SYMBOL(scm_detach_fds);
330
331struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
332{
333	struct scm_fp_list *new_fpl;
334	int i;
335
336	if (!fpl)
337		return NULL;
338
339	new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
340			  GFP_KERNEL);
341	if (new_fpl) {
342		for (i = 0; i < fpl->count; i++)
343			get_file(fpl->fp[i]);
344		new_fpl->max = new_fpl->count;
345		new_fpl->user = get_uid(fpl->user);
346	}
347	return new_fpl;
348}
349EXPORT_SYMBOL(scm_fp_dup);