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(); 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)); 248 if (!err) 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); 292