blob: e887d19be506f51e8625d4dbc8b63c1c3e367030 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* 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/errno.h>
15#include <linux/sched.h>
16#include <linux/mm.h>
17#include <linux/kernel.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070018#include <linux/stat.h>
19#include <linux/socket.h>
20#include <linux/file.h>
21#include <linux/fcntl.h>
22#include <linux/net.h>
23#include <linux/interrupt.h>
24#include <linux/netdevice.h>
25#include <linux/security.h>
26
27#include <asm/system.h>
28#include <asm/uaccess.h>
29
30#include <net/protocol.h>
31#include <linux/skbuff.h>
32#include <net/sock.h>
33#include <net/compat.h>
34#include <net/scm.h>
35
36
37/*
38 * Only allow a user to send credentials, that they could set with
39 * setu(g)id.
40 */
41
42static __inline__ int scm_check_creds(struct ucred *creds)
43{
44 if ((creds->pid == current->tgid || capable(CAP_SYS_ADMIN)) &&
45 ((creds->uid == current->uid || creds->uid == current->euid ||
46 creds->uid == current->suid) || capable(CAP_SETUID)) &&
47 ((creds->gid == current->gid || creds->gid == current->egid ||
48 creds->gid == current->sgid) || capable(CAP_SETGID))) {
49 return 0;
50 }
51 return -EPERM;
52}
53
54static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
55{
56 int *fdp = (int*)CMSG_DATA(cmsg);
57 struct scm_fp_list *fpl = *fplp;
58 struct file **fpp;
59 int i, num;
60
61 num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
62
63 if (num <= 0)
64 return 0;
65
66 if (num > SCM_MAX_FD)
67 return -EINVAL;
68
69 if (!fpl)
70 {
71 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
72 if (!fpl)
73 return -ENOMEM;
74 *fplp = fpl;
75 fpl->count = 0;
76 }
77 fpp = &fpl->fp[fpl->count];
78
79 if (fpl->count + num > SCM_MAX_FD)
80 return -EINVAL;
81
82 /*
83 * Verify the descriptors and increment the usage count.
84 */
85
86 for (i=0; i< num; i++)
87 {
88 int fd = fdp[i];
89 struct file *file;
90
91 if (fd < 0 || !(file = fget(fd)))
92 return -EBADF;
93 *fpp++ = file;
94 fpl->count++;
95 }
96 return num;
97}
98
99void __scm_destroy(struct scm_cookie *scm)
100{
101 struct scm_fp_list *fpl = scm->fp;
102 int i;
103
104 if (fpl) {
105 scm->fp = NULL;
106 for (i=fpl->count-1; i>=0; i--)
107 fput(fpl->fp[i]);
108 kfree(fpl);
109 }
110}
111
112int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
113{
114 struct cmsghdr *cmsg;
115 int err;
116
117 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
118 {
119 err = -EINVAL;
120
121 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
122 /* The first check was omitted in <= 2.2.5. The reasoning was
123 that parser checks cmsg_len in any case, so that
124 additional check would be work duplication.
125 But if cmsg_level is not SOL_SOCKET, we do not check
126 for too short ancillary data object at all! Oops.
127 OK, let's add it...
128 */
129 if (!CMSG_OK(msg, cmsg))
130 goto error;
131
132 if (cmsg->cmsg_level != SOL_SOCKET)
133 continue;
134
135 switch (cmsg->cmsg_type)
136 {
137 case SCM_RIGHTS:
138 err=scm_fp_copy(cmsg, &p->fp);
139 if (err<0)
140 goto error;
141 break;
142 case SCM_CREDENTIALS:
143 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
144 goto error;
145 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
146 err = scm_check_creds(&p->creds);
147 if (err)
148 goto error;
149 break;
150 default:
151 goto error;
152 }
153 }
154
155 if (p->fp && !p->fp->count)
156 {
157 kfree(p->fp);
158 p->fp = NULL;
159 }
160 return 0;
161
162error:
163 scm_destroy(p);
164 return err;
165}
166
167int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
168{
169 struct cmsghdr __user *cm = (struct cmsghdr __user *)msg->msg_control;
170 struct cmsghdr cmhdr;
171 int cmlen = CMSG_LEN(len);
172 int err;
173
174 if (MSG_CMSG_COMPAT & msg->msg_flags)
175 return put_cmsg_compat(msg, level, type, len, data);
176
177 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
178 msg->msg_flags |= MSG_CTRUNC;
179 return 0; /* XXX: return error? check spec. */
180 }
181 if (msg->msg_controllen < cmlen) {
182 msg->msg_flags |= MSG_CTRUNC;
183 cmlen = msg->msg_controllen;
184 }
185 cmhdr.cmsg_level = level;
186 cmhdr.cmsg_type = type;
187 cmhdr.cmsg_len = cmlen;
188
189 err = -EFAULT;
190 if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
191 goto out;
192 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
193 goto out;
194 cmlen = CMSG_SPACE(len);
195 msg->msg_control += cmlen;
196 msg->msg_controllen -= cmlen;
197 err = 0;
198out:
199 return err;
200}
201
202void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
203{
204 struct cmsghdr __user *cm = (struct cmsghdr __user*)msg->msg_control;
205
206 int fdmax = 0;
207 int fdnum = scm->fp->count;
208 struct file **fp = scm->fp->fp;
209 int __user *cmfptr;
210 int err = 0, i;
211
212 if (MSG_CMSG_COMPAT & msg->msg_flags) {
213 scm_detach_fds_compat(msg, scm);
214 return;
215 }
216
217 if (msg->msg_controllen > sizeof(struct cmsghdr))
218 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
219 / sizeof(int));
220
221 if (fdnum < fdmax)
222 fdmax = fdnum;
223
224 for (i=0, cmfptr=(int __user *)CMSG_DATA(cm); i<fdmax; i++, cmfptr++)
225 {
226 int new_fd;
227 err = security_file_receive(fp[i]);
228 if (err)
229 break;
230 err = get_unused_fd();
231 if (err < 0)
232 break;
233 new_fd = err;
234 err = put_user(new_fd, cmfptr);
235 if (err) {
236 put_unused_fd(new_fd);
237 break;
238 }
239 /* Bump the usage count and install the file. */
240 get_file(fp[i]);
241 fd_install(new_fd, fp[i]);
242 }
243
244 if (i > 0)
245 {
246 int cmlen = CMSG_LEN(i*sizeof(int));
247 if (!err)
248 err = put_user(SOL_SOCKET, &cm->cmsg_level);
249 if (!err)
250 err = put_user(SCM_RIGHTS, &cm->cmsg_type);
251 if (!err)
252 err = put_user(cmlen, &cm->cmsg_len);
253 if (!err) {
254 cmlen = CMSG_SPACE(i*sizeof(int));
255 msg->msg_control += cmlen;
256 msg->msg_controllen -= cmlen;
257 }
258 }
259 if (i < fdnum || (fdnum && fdmax <= 0))
260 msg->msg_flags |= MSG_CTRUNC;
261
262 /*
263 * All of the files that fit in the message have had their
264 * usage counts incremented, so we just free the list.
265 */
266 __scm_destroy(scm);
267}
268
269struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
270{
271 struct scm_fp_list *new_fpl;
272 int i;
273
274 if (!fpl)
275 return NULL;
276
277 new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
278 if (new_fpl) {
279 for (i=fpl->count-1; i>=0; i--)
280 get_file(fpl->fp[i]);
281 memcpy(new_fpl, fpl, sizeof(*fpl));
282 }
283 return new_fpl;
284}
285
286EXPORT_SYMBOL(__scm_destroy);
287EXPORT_SYMBOL(__scm_send);
288EXPORT_SYMBOL(put_cmsg);
289EXPORT_SYMBOL(scm_detach_fds);
290EXPORT_SYMBOL(scm_fp_dup);