fs/ecryptfs/netlink.c

   1 /**
   2  * eCryptfs: Linux filesystem encryption layer
   3  *
   4  * Copyright (C) 2004-2006 International Business Machines Corp.
   5  *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
   6  *              Tyler Hicks <tyhicks@ou.edu>
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License version
  10  * 2 as published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  20  * 02111-1307, USA.
  21  */
  22
  23 #include <net/sock.h>
  24 #include <linux/hash.h>
  25 #include <linux/random.h>
  26 #include "ecryptfs_kernel.h"
  27
  28 static struct sock *ecryptfs_nl_sock;
  29
  30 /**
  31  * ecryptfs_send_netlink
  32  * @data: The data to include as the payload
  33  * @data_len: The byte count of the data
  34  * @msg_ctx: The netlink context that will be used to handle the
  35  *          response message
  36  * @msg_type: The type of netlink message to send
  37  * @msg_flags: The flags to include in the netlink header
  38  * @daemon_pid: The process id of the daemon to send the message to
  39  *
  40  * Sends the data to the specified daemon pid and uses the netlink
  41  * context element to store the data needed for validation upon
  42  * receiving the response.  The data and the netlink context can be
  43  * null if just sending a netlink header is sufficient.  Returns zero
  44  * upon sending the message; non-zero upon error.
  45  */
  46 int ecryptfs_send_netlink(char *data, int data_len,
  47                           struct ecryptfs_msg_ctx *msg_ctx, u16 msg_type,
  48                           u16 msg_flags, pid_t daemon_pid)
  49 {
  50         struct sk_buff *skb;
  51         struct nlmsghdr *nlh;
  52         struct ecryptfs_message *msg;
  53         size_t payload_len;
  54         int rc;
  55
  56         payload_len = ((data && data_len) ? (sizeof(*msg) + data_len) : 0);
  57         skb = alloc_skb(NLMSG_SPACE(payload_len), GFP_KERNEL);
  58         if (!skb) {
  59                 rc = -ENOMEM;
  60                 ecryptfs_printk(KERN_ERR, "Failed to allocate socket buffer\n");
  61                 goto out;
  62         }
  63         nlh = NLMSG_PUT(skb, daemon_pid, msg_ctx ? msg_ctx->counter : 0,
  64                         msg_type, payload_len);
  65         nlh->nlmsg_flags = msg_flags;
  66         if (msg_ctx && payload_len) {
  67                 msg = (struct ecryptfs_message *)NLMSG_DATA(nlh);
  68                 msg->index = msg_ctx->index;
  69                 msg->data_len = data_len;
  70                 memcpy(msg->data, data, data_len);
  71         }
  72         rc = netlink_unicast(ecryptfs_nl_sock, skb, daemon_pid, 0);
  73         if (rc < 0) {
  74                 ecryptfs_printk(KERN_ERR, "Failed to send eCryptfs netlink "
  75                                 "message; rc = [%d]\n", rc);
  76                 goto out;
  77         }
  78         rc = 0;
  79         goto out;
  80 nlmsg_failure:
  81         rc = -EMSGSIZE;
  82         kfree_skb(skb);
  83 out:
  84         return rc;
  85 }
  86
  87 /**
  88  * ecryptfs_process_nl_reponse
  89  * @skb: The socket buffer containing the netlink message of state
  90  *       RESPONSE
  91  *
  92  * Processes a response message after sending a operation request to
  93  * userspace.  Attempts to assign the msg to a netlink context element
  94  * at the index specified in the msg.  The sk_buff and nlmsghdr must
  95  * be validated before this function. Returns zero upon delivery to
  96  * desired context element; non-zero upon delivery failure or error.
  97  */
  98 static int ecryptfs_process_nl_response(struct sk_buff *skb)
  99 {
 100         struct nlmsghdr *nlh = (struct nlmsghdr*)skb->data;
 101         struct ecryptfs_message *msg = NLMSG_DATA(nlh);
 102         int rc;
 103
 104         if (skb->len - NLMSG_HDRLEN - sizeof(*msg) != msg->data_len) {
 105                 rc = -EINVAL;
 106                 ecryptfs_printk(KERN_ERR, "Received netlink message with "
 107                                 "incorrectly specified data length\n");
 108                 goto out;
 109         }
 110         rc = ecryptfs_process_response(msg, NETLINK_CREDS(skb)->uid,
 111                                        NETLINK_CREDS(skb)->pid, nlh->nlmsg_seq);
 112         if (rc)
 113                 printk(KERN_ERR
 114                        "Error processing response message; rc = [%d]\n", rc);
 115 out:
 116         return rc;
 117 }
 118
 119 /**
 120  * ecryptfs_process_nl_helo
 121  * @skb: The socket buffer containing the nlmsghdr in HELO state
 122  *
 123  * Gets uid and pid of the skb and adds the values to the daemon id
 124  * hash. Returns zero after adding a new daemon id to the hash list;
 125  * non-zero otherwise.
 126  */
 127 static int ecryptfs_process_nl_helo(struct sk_buff *skb)
 128 {
 129         int rc;
 130
 131         rc = ecryptfs_process_helo(ECRYPTFS_TRANSPORT_NETLINK,
 132                                    NETLINK_CREDS(skb)->uid,
 133                                    NETLINK_CREDS(skb)->pid);
 134         if (rc)
 135                 printk(KERN_WARNING "Error processing HELO; rc = [%d]\n", rc);
 136         return rc;
 137 }
 138
 139 /**
 140  * ecryptfs_process_nl_quit
 141  * @skb: The socket buffer containing the nlmsghdr in QUIT state
 142  *
 143  * Gets uid and pid of the skb and deletes the corresponding daemon
 144  * id, if it is the registered that is requesting the
 145  * deletion. Returns zero after deleting the desired daemon id;
 146  * non-zero otherwise.
 147  */
 148 static int ecryptfs_process_nl_quit(struct sk_buff *skb)
 149 {
 150         int rc;
 151
 152         rc = ecryptfs_process_quit(NETLINK_CREDS(skb)->uid,
 153                                    NETLINK_CREDS(skb)->pid);
 154         if (rc)
 155                 printk(KERN_WARNING
 156                        "Error processing QUIT message; rc = [%d]\n", rc);
 157         return rc;
 158 }
 159
 160 /**
 161  * ecryptfs_receive_nl_message
 162  *
 163  * Callback function called by netlink system when a message arrives.
 164  * If the message looks to be valid, then an attempt is made to assign
 165  * it to its desired netlink context element and wake up the process
 166  * that is waiting for a response.
 167  */
 168 static void ecryptfs_receive_nl_message(struct sock *sk, int len)
 169 {
 170         struct sk_buff *skb;
 171         struct nlmsghdr *nlh;
 172         int rc = 0;     /* skb_recv_datagram requires this */
 173
 174 receive:
 175         skb = skb_recv_datagram(sk, 0, 0, &rc);
 176         if (rc == -EINTR)
 177                 goto receive;
 178         else if (rc < 0) {
 179                 ecryptfs_printk(KERN_ERR, "Error occurred while "
 180                                 "receiving eCryptfs netlink message; "
 181                                 "rc = [%d]\n", rc);
 182                 return;
 183         }
 184         nlh = (struct nlmsghdr *)skb->data;
 185         if (!NLMSG_OK(nlh, skb->len)) {
 186                 ecryptfs_printk(KERN_ERR, "Received corrupt netlink "
 187                                 "message\n");
 188                 goto free;
 189         }
 190         switch (nlh->nlmsg_type) {
 191                 case ECRYPTFS_NLMSG_RESPONSE:
 192                         if (ecryptfs_process_nl_response(skb)) {
 193                                 ecryptfs_printk(KERN_WARNING, "Failed to "
 194                                                 "deliver netlink response to "
 195                                                 "requesting operation\n");
 196                         }
 197                         break;
 198                 case ECRYPTFS_NLMSG_HELO:
 199                         if (ecryptfs_process_nl_helo(skb)) {
 200                                 ecryptfs_printk(KERN_WARNING, "Failed to "
 201                                                 "fulfill HELO request\n");
 202                         }
 203                         break;
 204                 case ECRYPTFS_NLMSG_QUIT:
 205                         if (ecryptfs_process_nl_quit(skb)) {
 206                                 ecryptfs_printk(KERN_WARNING, "Failed to "
 207                                                 "fulfill QUIT request\n");
 208                         }
 209                         break;
 210                 default:
 211                         ecryptfs_printk(KERN_WARNING, "Dropping netlink "
 212                                         "message of unrecognized type [%d]\n",
 213                                         nlh->nlmsg_type);
 214                         break;
 215         }
 216 free:
 217         kfree_skb(skb);
 218 }
 219
 220 /**
 221  * ecryptfs_init_netlink
 222  *
 223  * Initializes the daemon id hash list, netlink context array, and
 224  * necessary locks.  Returns zero upon success; non-zero upon error.
 225  */
 226 int ecryptfs_init_netlink(void)
 227 {
 228         int rc;
 229
 230         ecryptfs_nl_sock = netlink_kernel_create(NETLINK_ECRYPTFS, 0,
 231                                                  ecryptfs_receive_nl_message,
 232                                                  THIS_MODULE);
 233         if (!ecryptfs_nl_sock) {
 234                 rc = -EIO;
 235                 ecryptfs_printk(KERN_ERR, "Failed to create netlink socket\n");
 236                 goto out;
 237         }
 238         ecryptfs_nl_sock->sk_sndtimeo = ECRYPTFS_DEFAULT_SEND_TIMEOUT;
 239         rc = 0;
 240 out:
 241         return rc;
 242 }
 243
 244 /**
 245  * ecryptfs_release_netlink
 246  *
 247  * Frees all memory used by the netlink context array and releases the
 248  * netlink socket.
 249  */
 250 void ecryptfs_release_netlink(void)
 251 {
 252         if (ecryptfs_nl_sock && ecryptfs_nl_sock->sk_socket)
 253                 sock_release(ecryptfs_nl_sock->sk_socket);
 254         ecryptfs_nl_sock = NULL;
 255 }