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/errno.h> 15 #include <linux/sched.h> 16 #include <linux/mm.h> 17 #include <linux/kernel.h> 18 #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 42 static __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 54 static 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 99 void __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 } 111 112 int __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; 161 162 error: 163 scm_destroy(p); 164 return err; 165 } 166 167 int 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; 198 out: 199 return err; 200 } 201 202 void 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 } 268 269 struct 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 } 285 286 EXPORT_SYMBOL(__scm_destroy); 287 EXPORT_SYMBOL(__scm_send); 288 EXPORT_SYMBOL(put_cmsg); 289 EXPORT_SYMBOL(scm_detach_fds); 290 EXPORT_SYMBOL(scm_fp_dup); 291