net/core/scm.c

   1 /* scm.c - Socket level control messages processing.
   2  *
   3  * Author:      Alexey Kuznetsov, <[email protected]>
   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/sched/user.h>
  18 #include <linux/mm.h>
  19 #include <linux/kernel.h>
  20 #include <linux/stat.h>
  21 #include <linux/socket.h>
  22 #include <linux/file.h>
  23 #include <linux/fcntl.h>
  24 #include <linux/net.h>
  25 #include <linux/interrupt.h>
  26 #include <linux/netdevice.h>
  27 #include <linux/security.h>
  28 #include <linux/pid_namespace.h>
  29 #include <linux/pid.h>
  30 #include <linux/nsproxy.h>
  31 #include <linux/slab.h>
  32 #include <linux/errqueue.h>
  33
  34 #include <linux/uaccess.h>
  35
  36 #include <net/protocol.h>
  37 #include <linux/skbuff.h>
  38 #include <net/sock.h>
  39 #include <net/compat.h>
  40 #include <net/scm.h>
  41 #include <net/cls_cgroup.h>
  42
  43
  44 /*
  45  *      Only allow a user to send credentials, that they could set with
  46  *      setu(g)id.
  47  */
  48
  49 static __inline__ int scm_check_creds(struct ucred *creds)
  50 {
  51         const struct cred *cred = current_cred();
  52         kuid_t uid = make_kuid(cred->user_ns, creds->uid);
  53         kgid_t gid = make_kgid(cred->user_ns, creds->gid);
  54
  55         if (!uid_valid(uid) || !gid_valid(gid))
  56                 return -EINVAL;
  57
  58         if ((creds->pid == task_tgid_vnr(current) ||
  59              ns_capable(task_active_pid_ns(current)->user_ns, CAP_SYS_ADMIN)) &&
  60             ((uid_eq(uid, cred->uid)   || uid_eq(uid, cred->euid) ||
  61               uid_eq(uid, cred->suid)) || ns_capable(cred->user_ns, CAP_SETUID)) &&
  62             ((gid_eq(gid, cred->gid)   || gid_eq(gid, cred->egid) ||
  63               gid_eq(gid, cred->sgid)) || ns_capable(cred->user_ns, CAP_SETGID))) {
  64                return 0;
  65         }
  66         return -EPERM;
  67 }
  68
  69 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
  70 {
  71         int *fdp = (int*)CMSG_DATA(cmsg);
  72         struct scm_fp_list *fpl = *fplp;
  73         struct file **fpp;
  74         int i, num;
  75
  76         num = (cmsg->cmsg_len - sizeof(struct cmsghdr))/sizeof(int);
  77
  78         if (num <= 0)
  79                 return 0;
  80
  81         if (num > SCM_MAX_FD)
  82                 return -EINVAL;
  83
  84         if (!fpl)
  85         {
  86                 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
  87                 if (!fpl)
  88                         return -ENOMEM;
  89                 *fplp = fpl;
  90                 fpl->count = 0;
  91                 fpl->max = SCM_MAX_FD;
  92                 fpl->user = NULL;
  93         }
  94         fpp = &fpl->fp[fpl->count];
  95
  96         if (fpl->count + num > fpl->max)
  97                 return -EINVAL;
  98
  99         /*
 100          *      Verify the descriptors and increment the usage count.
 101          */
 102
 103         for (i=0; i< num; i++)
 104         {
 105                 int fd = fdp[i];
 106                 struct file *file;
 107
 108                 if (fd < 0 || !(file = fget_raw(fd)))
 109                         return -EBADF;
 110                 *fpp++ = file;
 111                 fpl->count++;
 112         }
 113
 114         if (!fpl->user)
 115                 fpl->user = get_uid(current_user());
 116
 117         return num;
 118 }
 119
 120 void __scm_destroy(struct scm_cookie *scm)
 121 {
 122         struct scm_fp_list *fpl = scm->fp;
 123         int i;
 124
 125         if (fpl) {
 126                 scm->fp = NULL;
 127                 for (i=fpl->count-1; i>=0; i--)
 128                         fput(fpl->fp[i]);
 129                 free_uid(fpl->user);
 130                 kfree(fpl);
 131         }
 132 }
 133 EXPORT_SYMBOL(__scm_destroy);
 134
 135 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
 136 {
 137         struct cmsghdr *cmsg;
 138         int err;
 139
 140         for_each_cmsghdr(cmsg, msg) {
 141                 err = -EINVAL;
 142
 143                 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
 144                 /* The first check was omitted in <= 2.2.5. The reasoning was
 145                    that parser checks cmsg_len in any case, so that
 146                    additional check would be work duplication.
 147                    But if cmsg_level is not SOL_SOCKET, we do not check
 148                    for too short ancillary data object at all! Oops.
 149                    OK, let's add it...
 150                  */
 151                 if (!CMSG_OK(msg, cmsg))
 152                         goto error;
 153
 154                 if (cmsg->cmsg_level != SOL_SOCKET)
 155                         continue;
 156
 157                 switch (cmsg->cmsg_type)
 158                 {
 159                 case SCM_RIGHTS:
 160                         if (!sock->ops || sock->ops->family != PF_UNIX)
 161                                 goto error;
 162                         err=scm_fp_copy(cmsg, &p->fp);
 163                         if (err<0)
 164                                 goto error;
 165                         break;
 166                 case SCM_CREDENTIALS:
 167                 {
 168                         struct ucred creds;
 169                         kuid_t uid;
 170                         kgid_t gid;
 171                         if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
 172                                 goto error;
 173                         memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred));
 174                         err = scm_check_creds(&creds);
 175                         if (err)
 176                                 goto error;
 177
 178                         p->creds.pid = creds.pid;
 179                         if (!p->pid || pid_vnr(p->pid) != creds.pid) {
 180                                 struct pid *pid;
 181                                 err = -ESRCH;
 182                                 pid = find_get_pid(creds.pid);
 183                                 if (!pid)
 184                                         goto error;
 185                                 put_pid(p->pid);
 186                                 p->pid = pid;
 187                         }
 188
 189                         err = -EINVAL;
 190                         uid = make_kuid(current_user_ns(), creds.uid);
 191                         gid = make_kgid(current_user_ns(), creds.gid);
 192                         if (!uid_valid(uid) || !gid_valid(gid))
 193                                 goto error;
 194
 195                         p->creds.uid = uid;
 196                         p->creds.gid = gid;
 197                         break;
 198                 }
 199                 default:
 200                         goto error;
 201                 }
 202         }
 203
 204         if (p->fp && !p->fp->count)
 205         {
 206                 kfree(p->fp);
 207                 p->fp = NULL;
 208         }
 209         return 0;
 210
 211 error:
 212         scm_destroy(p);
 213         return err;
 214 }
 215 EXPORT_SYMBOL(__scm_send);
 216
 217 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
 218 {
 219         struct cmsghdr __user *cm
 220                 = (__force struct cmsghdr __user *)msg->msg_control;
 221         struct cmsghdr cmhdr;
 222         int cmlen = CMSG_LEN(len);
 223         int err;
 224
 225         if (MSG_CMSG_COMPAT & msg->msg_flags)
 226                 return put_cmsg_compat(msg, level, type, len, data);
 227
 228         if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
 229                 msg->msg_flags |= MSG_CTRUNC;
 230                 return 0; /* XXX: return error? check spec. */
 231         }
 232         if (msg->msg_controllen < cmlen) {
 233                 msg->msg_flags |= MSG_CTRUNC;
 234                 cmlen = msg->msg_controllen;
 235         }
 236         cmhdr.cmsg_level = level;
 237         cmhdr.cmsg_type = type;
 238         cmhdr.cmsg_len = cmlen;
 239
 240         err = -EFAULT;
 241         if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
 242                 goto out;
 243         if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
 244                 goto out;
 245         cmlen = CMSG_SPACE(len);
 246         if (msg->msg_controllen < cmlen)
 247                 cmlen = msg->msg_controllen;
 248         msg->msg_control += cmlen;
 249         msg->msg_controllen -= cmlen;
 250         err = 0;
 251 out:
 252         return err;
 253 }
 254 EXPORT_SYMBOL(put_cmsg);
 255
 256 void put_cmsg_scm_timestamping64(struct msghdr *msg, struct scm_timestamping_internal *tss_internal)
 257 {
 258         struct scm_timestamping64 tss;
 259         int i;
 260
 261         for (i = 0; i < ARRAY_SIZE(tss.ts); i++) {
 262                 tss.ts[i].tv_sec = tss_internal->ts[i].tv_sec;
 263                 tss.ts[i].tv_nsec = tss_internal->ts[i].tv_nsec;
 264         }
 265
 266         put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_NEW, sizeof(tss), &tss);
 267 }
 268 EXPORT_SYMBOL(put_cmsg_scm_timestamping64);
 269
 270 void put_cmsg_scm_timestamping(struct msghdr *msg, struct scm_timestamping_internal *tss_internal)
 271 {
 272         struct scm_timestamping tss;
 273         int i;
 274
 275         for (i = 0; i < ARRAY_SIZE(tss.ts); i++)
 276                 tss.ts[i] = timespec64_to_timespec(tss_internal->ts[i]);
 277
 278         put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_OLD, sizeof(tss), &tss);
 279 }
 280 EXPORT_SYMBOL(put_cmsg_scm_timestamping);
 281
 282 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
 283 {
 284         struct cmsghdr __user *cm
 285                 = (__force struct cmsghdr __user*)msg->msg_control;
 286
 287         int fdmax = 0;
 288         int fdnum = scm->fp->count;
 289         struct file **fp = scm->fp->fp;
 290         int __user *cmfptr;
 291         int err = 0, i;
 292
 293         if (MSG_CMSG_COMPAT & msg->msg_flags) {
 294                 scm_detach_fds_compat(msg, scm);
 295                 return;
 296         }
 297
 298         if (msg->msg_controllen > sizeof(struct cmsghdr))
 299                 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
 300                          / sizeof(int));
 301
 302         if (fdnum < fdmax)
 303                 fdmax = fdnum;
 304
 305         for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
 306              i++, cmfptr++)
 307         {
 308                 struct socket *sock;
 309                 int new_fd;
 310                 err = security_file_receive(fp[i]);
 311                 if (err)
 312                         break;
 313                 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
 314                                           ? O_CLOEXEC : 0);
 315                 if (err < 0)
 316                         break;
 317                 new_fd = err;
 318                 err = put_user(new_fd, cmfptr);
 319                 if (err) {
 320                         put_unused_fd(new_fd);
 321                         break;
 322                 }
 323                 /* Bump the usage count and install the file. */
 324                 sock = sock_from_file(fp[i], &err);
 325                 if (sock) {
 326                         sock_update_netprioidx(&sock->sk->sk_cgrp_data);
 327                         sock_update_classid(&sock->sk->sk_cgrp_data);
 328                 }
 329                 fd_install(new_fd, get_file(fp[i]));
 330         }
 331
 332         if (i > 0)
 333         {
 334                 int cmlen = CMSG_LEN(i*sizeof(int));
 335                 err = put_user(SOL_SOCKET, &cm->cmsg_level);
 336                 if (!err)
 337                         err = put_user(SCM_RIGHTS, &cm->cmsg_type);
 338                 if (!err)
 339                         err = put_user(cmlen, &cm->cmsg_len);
 340                 if (!err) {
 341                         cmlen = CMSG_SPACE(i*sizeof(int));
 342                         if (msg->msg_controllen < cmlen)
 343                                 cmlen = msg->msg_controllen;
 344                         msg->msg_control += cmlen;
 345                         msg->msg_controllen -= cmlen;
 346                 }
 347         }
 348         if (i < fdnum || (fdnum && fdmax <= 0))
 349                 msg->msg_flags |= MSG_CTRUNC;
 350
 351         /*
 352          * All of the files that fit in the message have had their
 353          * usage counts incremented, so we just free the list.
 354          */
 355         __scm_destroy(scm);
 356 }
 357 EXPORT_SYMBOL(scm_detach_fds);
 358
 359 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
 360 {
 361         struct scm_fp_list *new_fpl;
 362         int i;
 363
 364         if (!fpl)
 365                 return NULL;
 366
 367         new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
 368                           GFP_KERNEL);
 369         if (new_fpl) {
 370                 for (i = 0; i < fpl->count; i++)
 371                         get_file(fpl->fp[i]);
 372                 new_fpl->max = new_fpl->count;
 373                 new_fpl->user = get_uid(fpl->user);
 374         }
 375         return new_fpl;
 376 }
 377 EXPORT_SYMBOL(scm_fp_dup);