source3/lib/msghdr.c

   1 /*
   2  * Unix SMB/CIFS implementation.
   3  * Copyright (C) Volker Lendecke 2014
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 3 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #include "replace.h"
  20 #include "lib/msghdr.h"
  21 #include "lib/iov_buf.h"
  22 #include <sys/socket.h>
  23
  24 ssize_t msghdr_prep_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
  25                         const int *fds, size_t num_fds)
  26 {
  27         size_t fds_size = sizeof(int) * MIN(num_fds, INT8_MAX);
  28         size_t cmsg_len = CMSG_LEN(fds_size);
  29         size_t cmsg_space = CMSG_SPACE(fds_size);
  30         struct cmsghdr *cmsg;
  31         void *fdptr;
  32
  33         if (num_fds == 0) {
  34                 if (msg != NULL) {
  35                         msg->msg_control = NULL;
  36                         msg->msg_controllen = 0;
  37                 }
  38                 return 0;
  39         }
  40         if (num_fds > INT8_MAX) {
  41                 return -1;
  42         }
  43         if (cmsg_space > bufsize) {
  44                 return cmsg_space;
  45         }
  46
  47         msg->msg_control = buf;
  48         msg->msg_controllen = cmsg_space;
  49
  50         cmsg = CMSG_FIRSTHDR(msg);
  51         cmsg->cmsg_level = SOL_SOCKET;
  52         cmsg->cmsg_type = SCM_RIGHTS;
  53         cmsg->cmsg_len = cmsg_len;
  54         fdptr = CMSG_DATA(cmsg);
  55         memcpy(fdptr, fds, fds_size);
  56         msg->msg_controllen = cmsg->cmsg_len;
  57
  58         return cmsg_space;
  59 }
  60
  61 struct msghdr_buf {
  62         struct msghdr msg;
  63         struct sockaddr_storage addr;
  64         struct iovec iov;
  65         uint8_t buf[];
  66 };
  67
  68 ssize_t msghdr_copy(struct msghdr_buf *msg, size_t msgsize,
  69                     const void *addr, socklen_t addrlen,
  70                     const struct iovec *iov, int iovcnt,
  71                     const int *fds, size_t num_fds)
  72 {
  73         size_t fd_len, iov_len, needed, bufsize;
  74
  75         bufsize = (msgsize > offsetof(struct msghdr_buf, buf)) ?
  76                 msgsize - offsetof(struct msghdr_buf, buf) : 0;
  77
  78         fd_len = msghdr_prep_fds(&msg->msg, msg->buf, bufsize, fds, num_fds);
  79
  80         if (bufsize >= fd_len) {
  81                 bufsize -= fd_len;
  82         } else {
  83                 bufsize = 0;
  84         }
  85
  86         if (msg != NULL) {
  87
  88                 if (addr != NULL) {
  89                         if (addrlen > sizeof(struct sockaddr_storage)) {
  90                                 errno = EMSGSIZE;
  91                                 return -1;
  92                         }
  93                         memcpy(&msg->addr, addr, addrlen);
  94                         msg->msg.msg_name = &msg->addr;
  95                         msg->msg.msg_namelen = addrlen;
  96                 } else {
  97                         msg->msg.msg_name = NULL;
  98                         msg->msg.msg_namelen = 0;
  99                 }
 100
 101                 msg->iov.iov_base = msg->buf + fd_len;
 102                 msg->iov.iov_len = iov_buf(
 103                         iov, iovcnt, msg->iov.iov_base, bufsize);
 104                 iov_len = msg->iov.iov_len;
 105
 106                 msg->msg.msg_iov = &msg->iov;
 107                 msg->msg.msg_iovlen = 1;
 108         } else {
 109                 iov_len = iov_buflen(iov, iovcnt);
 110         }
 111
 112         needed = offsetof(struct msghdr_buf, buf) + fd_len;
 113         if (needed < fd_len) {
 114                 return -1;
 115         }
 116         needed += iov_len;
 117         if (needed < iov_len) {
 118                 return -1;
 119         }
 120
 121         return needed;
 122 }
 123
 124 struct msghdr *msghdr_buf_msghdr(struct msghdr_buf *msg)
 125 {
 126         return &msg->msg;
 127 }
 128
 129 size_t msghdr_extract_fds(struct msghdr *msg, int *fds, size_t fds_size)
 130 {
 131         struct cmsghdr *cmsg;
 132         size_t num_fds;
 133
 134         for(cmsg = CMSG_FIRSTHDR(msg);
 135             cmsg != NULL;
 136             cmsg = CMSG_NXTHDR(msg, cmsg))
 137         {
 138                 if ((cmsg->cmsg_type == SCM_RIGHTS) &&
 139                     (cmsg->cmsg_level == SOL_SOCKET)) {
 140                         break;
 141                 }
 142         }
 143
 144         if (cmsg == NULL) {
 145                 return 0;
 146         }
 147
 148         num_fds = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
 149
 150         if ((num_fds != 0) && (fds_size >= num_fds)) {
 151                 memcpy(fds, CMSG_DATA(cmsg), num_fds * sizeof(int));
 152         }
 153
 154         return num_fds;
 155 }