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1da177e4 LT |
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> | |
4fc268d2 | 14 | #include <linux/capability.h> |
1da177e4 LT |
15 | #include <linux/errno.h> |
16 | #include <linux/sched.h> | |
17 | #include <linux/mm.h> | |
18 | #include <linux/kernel.h> | |
1da177e4 LT |
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 | /* | |
4ec93edb | 39 | * Only allow a user to send credentials, that they could set with |
1da177e4 LT |
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; | |
4ec93edb | 82 | |
1da177e4 LT |
83 | /* |
84 | * Verify the descriptors and increment the usage count. | |
85 | */ | |
4ec93edb | 86 | |
1da177e4 LT |
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. | |
4ec93edb | 126 | But if cmsg_level is not SOL_SOCKET, we do not check |
1da177e4 LT |
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; | |
4ec93edb | 162 | |
1da177e4 LT |
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)) | |
4ec93edb | 192 | goto out; |
1da177e4 LT |
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; | |
4a19542e UD |
231 | err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags |
232 | ? O_CLOEXEC : 0); | |
1da177e4 LT |
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)); | |
effee6a0 | 249 | err = put_user(SOL_SOCKET, &cm->cmsg_level); |
1da177e4 LT |
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); |