blob: 271cf060ef8c69fb79f37768972af65b5457d835 [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>
Randy Dunlap4fc268d2006-01-11 12:17:47 -080014#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070015#include <linux/errno.h>
16#include <linux/sched.h>
17#include <linux/mm.h>
18#include <linux/kernel.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070019#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
28#include <asm/system.h>
29#include <asm/uaccess.h>
30
31#include <net/protocol.h>
32#include <linux/skbuff.h>
33#include <net/sock.h>
34#include <net/compat.h>
35#include <net/scm.h>
36
37
38/*
39 * Only allow a user to send credentials, that they could set with
40 * setu(g)id.
41 */
42
43static __inline__ int scm_check_creds(struct ucred *creds)
44{
45 if ((creds->pid == current->tgid || capable(CAP_SYS_ADMIN)) &&
46 ((creds->uid == current->uid || creds->uid == current->euid ||
47 creds->uid == current->suid) || capable(CAP_SETUID)) &&
48 ((creds->gid == current->gid || creds->gid == current->egid ||
49 creds->gid == current->sgid) || capable(CAP_SETGID))) {
50 return 0;
51 }
52 return -EPERM;
53}
54
55static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
56{
57 int *fdp = (int*)CMSG_DATA(cmsg);
58 struct scm_fp_list *fpl = *fplp;
59 struct file **fpp;
60 int i, num;
61
62 num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
63
64 if (num <= 0)
65 return 0;
66
67 if (num > SCM_MAX_FD)
68 return -EINVAL;
69
70 if (!fpl)
71 {
72 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
73 if (!fpl)
74 return -ENOMEM;
75 *fplp = fpl;
76 fpl->count = 0;
77 }
78 fpp = &fpl->fp[fpl->count];
79
80 if (fpl->count + num > SCM_MAX_FD)
81 return -EINVAL;
82
83 /*
84 * Verify the descriptors and increment the usage count.
85 */
86
87 for (i=0; i< num; i++)
88 {
89 int fd = fdp[i];
90 struct file *file;
91
92 if (fd < 0 || !(file = fget(fd)))
93 return -EBADF;
94 *fpp++ = file;
95 fpl->count++;
96 }
97 return num;
98}
99
100void __scm_destroy(struct scm_cookie *scm)
101{
102 struct scm_fp_list *fpl = scm->fp;
103 int i;
104
105 if (fpl) {
106 scm->fp = NULL;
107 for (i=fpl->count-1; i>=0; i--)
108 fput(fpl->fp[i]);
109 kfree(fpl);
110 }
111}
112
113int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
114{
115 struct cmsghdr *cmsg;
116 int err;
117
118 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
119 {
120 err = -EINVAL;
121
122 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
123 /* The first check was omitted in <= 2.2.5. The reasoning was
124 that parser checks cmsg_len in any case, so that
125 additional check would be work duplication.
126 But if cmsg_level is not SOL_SOCKET, we do not check
127 for too short ancillary data object at all! Oops.
128 OK, let's add it...
129 */
130 if (!CMSG_OK(msg, cmsg))
131 goto error;
132
133 if (cmsg->cmsg_level != SOL_SOCKET)
134 continue;
135
136 switch (cmsg->cmsg_type)
137 {
138 case SCM_RIGHTS:
139 err=scm_fp_copy(cmsg, &p->fp);
140 if (err<0)
141 goto error;
142 break;
143 case SCM_CREDENTIALS:
144 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
145 goto error;
146 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
147 err = scm_check_creds(&p->creds);
148 if (err)
149 goto error;
150 break;
151 default:
152 goto error;
153 }
154 }
155
156 if (p->fp && !p->fp->count)
157 {
158 kfree(p->fp);
159 p->fp = NULL;
160 }
161 return 0;
162
163error:
164 scm_destroy(p);
165 return err;
166}
167
168int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
169{
170 struct cmsghdr __user *cm = (struct cmsghdr __user *)msg->msg_control;
171 struct cmsghdr cmhdr;
172 int cmlen = CMSG_LEN(len);
173 int err;
174
175 if (MSG_CMSG_COMPAT & msg->msg_flags)
176 return put_cmsg_compat(msg, level, type, len, data);
177
178 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
179 msg->msg_flags |= MSG_CTRUNC;
180 return 0; /* XXX: return error? check spec. */
181 }
182 if (msg->msg_controllen < cmlen) {
183 msg->msg_flags |= MSG_CTRUNC;
184 cmlen = msg->msg_controllen;
185 }
186 cmhdr.cmsg_level = level;
187 cmhdr.cmsg_type = type;
188 cmhdr.cmsg_len = cmlen;
189
190 err = -EFAULT;
191 if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
192 goto out;
193 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
194 goto out;
195 cmlen = CMSG_SPACE(len);
196 msg->msg_control += cmlen;
197 msg->msg_controllen -= cmlen;
198 err = 0;
199out:
200 return err;
201}
202
203void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
204{
205 struct cmsghdr __user *cm = (struct cmsghdr __user*)msg->msg_control;
206
207 int fdmax = 0;
208 int fdnum = scm->fp->count;
209 struct file **fp = scm->fp->fp;
210 int __user *cmfptr;
211 int err = 0, i;
212
213 if (MSG_CMSG_COMPAT & msg->msg_flags) {
214 scm_detach_fds_compat(msg, scm);
215 return;
216 }
217
218 if (msg->msg_controllen > sizeof(struct cmsghdr))
219 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
220 / sizeof(int));
221
222 if (fdnum < fdmax)
223 fdmax = fdnum;
224
225 for (i=0, cmfptr=(int __user *)CMSG_DATA(cm); i<fdmax; i++, cmfptr++)
226 {
227 int new_fd;
228 err = security_file_receive(fp[i]);
229 if (err)
230 break;
231 err = get_unused_fd();
232 if (err < 0)
233 break;
234 new_fd = err;
235 err = put_user(new_fd, cmfptr);
236 if (err) {
237 put_unused_fd(new_fd);
238 break;
239 }
240 /* Bump the usage count and install the file. */
241 get_file(fp[i]);
242 fd_install(new_fd, fp[i]);
243 }
244
245 if (i > 0)
246 {
247 int cmlen = CMSG_LEN(i*sizeof(int));
Miklos Szeredieffee6a2006-10-09 21:42:14 -0700248 err = put_user(SOL_SOCKET, &cm->cmsg_level);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249 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);