lib/util/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/util/msghdr.h"
  21 #include "lib/util/iov_buf.h"
  22 #include <sys/socket.h>
  23
  24 #if defined(HAVE_STRUCT_MSGHDR_MSG_CONTROL)
  25
  26 ssize_t msghdr_prep_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
  27                         const int *fds, size_t num_fds)
  28 {
  29         size_t fds_size = sizeof(int) * MIN(num_fds, INT8_MAX);
  30         size_t cmsg_len = CMSG_LEN(fds_size);
  31         size_t cmsg_space = CMSG_SPACE(fds_size);
  32         struct cmsghdr *cmsg;
  33         void *fdptr;
  34
  35         if (num_fds == 0) {
  36                 if (msg != NULL) {
  37                         msg->msg_control = NULL;
  38                         msg->msg_controllen = 0;
  39                 }
  40                 /*
  41                  * C99 doesn't allow 0-length arrays
  42                  */
  43                 return 1;
  44         }
  45         if (num_fds > INT8_MAX) {
  46                 return -1;
  47         }
  48         if ((msg == NULL) || (cmsg_space > bufsize)) {
  49                 /*
  50                  * C99 doesn't allow 0-length arrays
  51                  */
  52                 return MAX(cmsg_space, 1);
  53         }
  54
  55         msg->msg_control = buf;
  56         msg->msg_controllen = cmsg_space;
  57
  58         cmsg = CMSG_FIRSTHDR(msg);
  59         cmsg->cmsg_level = SOL_SOCKET;
  60         cmsg->cmsg_type = SCM_RIGHTS;
  61         cmsg->cmsg_len = cmsg_len;
  62         fdptr = CMSG_DATA(cmsg);
  63         memcpy(fdptr, fds, fds_size);
  64         msg->msg_controllen = cmsg->cmsg_len;
  65
  66         return cmsg_space;
  67 }
  68
  69 size_t msghdr_prep_recv_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
  70                             size_t num_fds)
  71 {
  72         size_t ret = CMSG_SPACE(sizeof(int) * num_fds);
  73
  74         if (bufsize < ret) {
  75                 return ret;
  76         }
  77         if (msg != NULL) {
  78                 if (num_fds != 0) {
  79                         msg->msg_control = buf;
  80                         msg->msg_controllen = ret;
  81                 } else {
  82                         msg->msg_control = NULL;
  83                         msg->msg_controllen = 0;
  84                 }
  85         }
  86         return ret;
  87 }
  88
  89 size_t msghdr_extract_fds(struct msghdr *msg, int *fds, size_t fds_size)
  90 {
  91         struct cmsghdr *cmsg;
  92         size_t num_fds;
  93
  94         for(cmsg = CMSG_FIRSTHDR(msg);
  95             cmsg != NULL;
  96             cmsg = CMSG_NXTHDR(msg, cmsg))
  97         {
  98                 if ((cmsg->cmsg_type == SCM_RIGHTS) &&
  99                     (cmsg->cmsg_level == SOL_SOCKET)) {
 100                         break;
 101                 }
 102         }
 103
 104         if (cmsg == NULL) {
 105                 return 0;
 106         }
 107
 108         num_fds = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
 109
 110         if ((num_fds != 0) && (fds != NULL) && (fds_size >= num_fds)) {
 111                 memcpy(fds, CMSG_DATA(cmsg), num_fds * sizeof(int));
 112         }
 113
 114         return num_fds;
 115 }
 116
 117 #elif defined(HAVE_STRUCT_MSGHDR_MSG_ACCRIGHTS)
 118
 119 ssize_t msghdr_prep_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
 120                         const int *fds, size_t num_fds)
 121 {
 122         size_t needed;
 123
 124         if (num_fds > INT8_MAX) {
 125                 return -1;
 126         }
 127
 128         needed = sizeof(int) * num_fds;
 129
 130         if ((msg == NULL) || (needed > bufsize)) {
 131                 return needed;
 132         }
 133
 134         memcpy(buf, fds, needed);
 135
 136         msg->msg_accrights = (caddr_t) buf;
 137         msg->msg_accrightslen = needed;
 138
 139         return needed;
 140 }
 141
 142 size_t msghdr_prep_recv_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
 143                             size_t num_fds)
 144 {
 145         size_t ret = num_fds * sizeof(int);
 146
 147         if (bufsize < ret) {
 148                 return ret;
 149         }
 150
 151         if (msg != NULL) {
 152                 if (num_fds != 0) {
 153                         msg->msg_accrights = (caddr_t) buf;
 154                         msg->msg_accrightslen = ret;
 155                 } else {
 156                         msg->msg_accrights = NULL;
 157                         msg->msg_accrightslen = 0;
 158                 }
 159         }
 160         return ret;
 161 }
 162
 163 size_t msghdr_extract_fds(struct msghdr *msg, int *fds, size_t fds_size)
 164 {
 165         size_t num_fds = msg->msg_accrightslen / sizeof(int);
 166
 167         if ((fds != 0) && (num_fds <= fds_size)) {
 168                 memcpy(fds, msg->msg_accrights, msg->msg_accrightslen);
 169         }
 170
 171         return num_fds;
 172 }
 173
 174 #else
 175
 176 ssize_t msghdr_prep_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
 177                         const int *fds, size_t num_fds)
 178 {
 179         return -1;
 180 }
 181
 182 size_t msghdr_prep_recv_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
 183                             size_t num_fds)
 184 {
 185         return 0;
 186 }
 187
 188 size_t msghdr_extract_fds(struct msghdr *msg, int *fds, size_t fds_size)
 189 {
 190         return 0;
 191 }
 192
 193 #endif
 194
 195 struct msghdr_buf {
 196         struct msghdr msg;
 197         struct sockaddr_storage addr;
 198         struct iovec iov;
 199         uint8_t buf[];
 200 };
 201
 202 ssize_t msghdr_copy(struct msghdr_buf *msg, size_t msgsize,
 203                     const void *addr, socklen_t addrlen,
 204                     const struct iovec *iov, int iovcnt,
 205                     const int *fds, size_t num_fds)
 206 {
 207         ssize_t fd_len;
 208         size_t iov_len, needed, bufsize;
 209
 210         bufsize = (msgsize > offsetof(struct msghdr_buf, buf)) ?
 211                 msgsize - offsetof(struct msghdr_buf, buf) : 0;
 212
 213         if (msg != NULL) {
 214                 msg->msg = (struct msghdr) { 0 };
 215
 216                 fd_len = msghdr_prep_fds(&msg->msg, msg->buf, bufsize,
 217                                          fds, num_fds);
 218         } else {
 219                 fd_len = msghdr_prep_fds(NULL, NULL, bufsize, fds, num_fds);
 220         }
 221
 222         if (fd_len == -1) {
 223                 return -1;
 224         }
 225
 226         if (bufsize >= fd_len) {
 227                 bufsize -= fd_len;
 228         } else {
 229                 bufsize = 0;
 230         }
 231
 232         if (msg != NULL) {
 233
 234                 if (addr != NULL) {
 235                         if (addrlen > sizeof(struct sockaddr_storage)) {
 236                                 errno = EMSGSIZE;
 237                                 return -1;
 238                         }
 239                         memcpy(&msg->addr, addr, addrlen);
 240                         msg->msg.msg_name = &msg->addr;
 241                         msg->msg.msg_namelen = addrlen;
 242                 } else {
 243                         msg->msg.msg_name = NULL;
 244                         msg->msg.msg_namelen = 0;
 245                 }
 246
 247                 msg->iov.iov_base = msg->buf + fd_len;
 248                 msg->iov.iov_len = iov_buf(
 249                         iov, iovcnt, msg->iov.iov_base, bufsize);
 250                 iov_len = msg->iov.iov_len;
 251
 252                 msg->msg.msg_iov = &msg->iov;
 253                 msg->msg.msg_iovlen = 1;
 254         } else {
 255                 iov_len = iov_buflen(iov, iovcnt);
 256         }
 257
 258         needed = offsetof(struct msghdr_buf, buf) + fd_len;
 259         if (needed < fd_len) {
 260                 return -1;
 261         }
 262         needed += iov_len;
 263         if (needed < iov_len) {
 264                 return -1;
 265         }
 266
 267         return needed;
 268 }
 269
 270 struct msghdr *msghdr_buf_msghdr(struct msghdr_buf *msg)
 271 {
 272         return &msg->msg;
 273 }