44c4ec2c8769b1a922d69a6f0e5882bc6f58f001
[linux-2.6.git] / net / core / scm.c
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
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
43 static __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
55 static 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
100 void __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
113 int __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
163 error:
164         scm_destroy(p);
165         return err;
166 }
167
168 int 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;
199 out:
200         return err;
201 }
202
203 void 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_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
232                                           ? O_CLOEXEC : 0);
233                 if (err < 0)
234                         break;
235                 new_fd = err;
236                 err = put_user(new_fd, cmfptr);
237                 if (err) {
238                         put_unused_fd(new_fd);
239                         break;
240                 }
241                 /* Bump the usage count and install the file. */
242                 get_file(fp[i]);
243                 fd_install(new_fd, fp[i]);
244         }
245
246         if (i > 0)
247         {
248                 int cmlen = CMSG_LEN(i*sizeof(int));
249                 err = put_user(SOL_SOCKET, &cm->cmsg_level);
250                 if (!err)
251                         err = put_user(SCM_RIGHTS, &cm->cmsg_type);
252                 if (!err)
253                         err = put_user(cmlen, &cm->cmsg_len);
254                 if (!err) {
255                         cmlen = CMSG_SPACE(i*sizeof(int));
256                         msg->msg_control += cmlen;
257                         msg->msg_controllen -= cmlen;
258                 }
259         }
260         if (i < fdnum || (fdnum && fdmax <= 0))
261                 msg->msg_flags |= MSG_CTRUNC;
262
263         /*
264          * All of the files that fit in the message have had their
265          * usage counts incremented, so we just free the list.
266          */
267         __scm_destroy(scm);
268 }
269
270 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
271 {
272         struct scm_fp_list *new_fpl;
273         int i;
274
275         if (!fpl)
276                 return NULL;
277
278         new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
279         if (new_fpl) {
280                 for (i=fpl->count-1; i>=0; i--)
281                         get_file(fpl->fp[i]);
282                 memcpy(new_fpl, fpl, sizeof(*fpl));
283         }
284         return new_fpl;
285 }
286
287 EXPORT_SYMBOL(__scm_destroy);
288 EXPORT_SYMBOL(__scm_send);
289 EXPORT_SYMBOL(put_cmsg);
290 EXPORT_SYMBOL(scm_detach_fds);
291 EXPORT_SYMBOL(scm_fp_dup);