l2_packet_privsep.c

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/*
 * WPA Supplicant - Layer2 packet handling with privilege separation
 * Copyright (c) 2007, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"
#include <sys/un.h>

#include "common.h"
#include "eloop.h"
#include "l2_packet.h"
#include "common/privsep_commands.h"


struct l2_packet_data {
        int fd; /* UNIX domain socket for privsep access */
        void (*rx_callback)(void *ctx, const u8 *src_addr,
                            const u8 *buf, size_t len);
        void *rx_callback_ctx;
        u8 own_addr[ETH_ALEN];
        char *own_socket_path;
        struct sockaddr_un priv_addr;
};


static int wpa_priv_cmd(struct l2_packet_data *l2, int cmd,
                        const void *data, size_t data_len)
{
        struct msghdr msg;
        struct iovec io[2];

        io[0].iov_base = &cmd;
        io[0].iov_len = sizeof(cmd);
        io[1].iov_base = (u8 *) data;
        io[1].iov_len = data_len;

        os_memset(&msg, 0, sizeof(msg));
        msg.msg_iov = io;
        msg.msg_iovlen = data ? 2 : 1;
        msg.msg_name = &l2->priv_addr;
        msg.msg_namelen = sizeof(l2->priv_addr);

        if (sendmsg(l2->fd, &msg, 0) < 0) {
                perror("L2: sendmsg(cmd)");
                return -1;
        }

        return 0;
}

                             
int l2_packet_get_own_addr(struct l2_packet_data *l2, u8 *addr)
{
        os_memcpy(addr, l2->own_addr, ETH_ALEN);
        return 0;
}


int l2_packet_send(struct l2_packet_data *l2, const u8 *dst_addr, u16 proto,
                   const u8 *buf, size_t len)
{
        struct msghdr msg;
        struct iovec io[4];
        int cmd = PRIVSEP_CMD_L2_SEND;

        io[0].iov_base = &cmd;
        io[0].iov_len = sizeof(cmd);
        io[1].iov_base = &dst_addr;
        io[1].iov_len = ETH_ALEN;
        io[2].iov_base = &proto;
        io[2].iov_len = 2;
        io[3].iov_base = (u8 *) buf;
        io[3].iov_len = len;

        os_memset(&msg, 0, sizeof(msg));
        msg.msg_iov = io;
        msg.msg_iovlen = 4;
        msg.msg_name = &l2->priv_addr;
        msg.msg_namelen = sizeof(l2->priv_addr);

        if (sendmsg(l2->fd, &msg, 0) < 0) {
                perror("L2: sendmsg(packet_send)");
                return -1;
        }

        return 0;
}


static void l2_packet_receive(int sock, void *eloop_ctx, void *sock_ctx)
{
        struct l2_packet_data *l2 = eloop_ctx;
        u8 buf[2300];
        int res;
        struct sockaddr_un from;
        socklen_t fromlen = sizeof(from);

        os_memset(&from, 0, sizeof(from));
        res = recvfrom(sock, buf, sizeof(buf), 0, (struct sockaddr *) &from,
                       &fromlen);
        if (res < 0) {
                perror("l2_packet_receive - recvfrom");
                return;
        }
        if (res < ETH_ALEN) {
                wpa_printf(MSG_DEBUG, "L2: Too show packet received");
                return;
        }

        if (from.sun_family != AF_UNIX ||
            os_strncmp(from.sun_path, l2->priv_addr.sun_path,
                       sizeof(from.sun_path)) != 0) {
                wpa_printf(MSG_DEBUG, "L2: Received message from unexpected "
                           "source");
                return;
        }

        l2->rx_callback(l2->rx_callback_ctx, buf, buf + ETH_ALEN,
                        res - ETH_ALEN);
}


struct l2_packet_data * l2_packet_init(
        const char *ifname, const u8 *own_addr, unsigned short protocol,
        void (*rx_callback)(void *ctx, const u8 *src_addr,
                            const u8 *buf, size_t len),
        void *rx_callback_ctx, int l2_hdr)
{
        struct l2_packet_data *l2;
        char *own_dir = "/tmp";
        char *priv_dir = "/var/run/wpa_priv";
        size_t len;
        static unsigned int counter = 0;
        struct sockaddr_un addr;
        fd_set rfds;
        struct timeval tv;
        int res;
        u8 reply[ETH_ALEN + 1];
        int reg_cmd[2];

        l2 = os_zalloc(sizeof(struct l2_packet_data));
        if (l2 == NULL)
                return NULL;
        l2->rx_callback = rx_callback;
        l2->rx_callback_ctx = rx_callback_ctx;

        len = os_strlen(own_dir) + 50;
        l2->own_socket_path = os_malloc(len);
        if (l2->own_socket_path == NULL) {
                os_free(l2);
                return NULL;
        }
        os_snprintf(l2->own_socket_path, len, "%s/wpa_privsep-l2-%d-%d",
                    own_dir, getpid(), counter++);

        l2->priv_addr.sun_family = AF_UNIX;
        os_snprintf(l2->priv_addr.sun_path, sizeof(l2->priv_addr.sun_path),
                    "%s/%s", priv_dir, ifname);

        l2->fd = socket(PF_UNIX, SOCK_DGRAM, 0);
        if (l2->fd < 0) {
                perror("socket(PF_UNIX)");
                os_free(l2->own_socket_path);
                l2->own_socket_path = NULL;
                os_free(l2);
                return NULL;
        }

        os_memset(&addr, 0, sizeof(addr));
        addr.sun_family = AF_UNIX;
        os_strlcpy(addr.sun_path, l2->own_socket_path, sizeof(addr.sun_path));
        if (bind(l2->fd, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
                perror("bind(PF_UNIX)");
                goto fail;
        }

        reg_cmd[0] = protocol;
        reg_cmd[1] = l2_hdr;
        if (wpa_priv_cmd(l2, PRIVSEP_CMD_L2_REGISTER, reg_cmd, sizeof(reg_cmd))
            < 0) {
                wpa_printf(MSG_ERROR, "L2: Failed to register with wpa_priv");
                goto fail;
        }

        FD_ZERO(&rfds);
        FD_SET(l2->fd, &rfds);
        tv.tv_sec = 5;
        tv.tv_usec = 0;
        res = select(l2->fd + 1, &rfds, NULL, NULL, &tv);
        if (res < 0 && errno != EINTR) {
                perror("select");
                goto fail;
        }

        if (FD_ISSET(l2->fd, &rfds)) {
                res = recv(l2->fd, reply, sizeof(reply), 0);
                if (res < 0) {
                        perror("recv");
                        goto fail;
                }
        } else {
                wpa_printf(MSG_DEBUG, "L2: Timeout while waiting for "
                           "registration reply");
                goto fail;
        }

        if (res != ETH_ALEN) {
                wpa_printf(MSG_DEBUG, "L2: Unexpected registration reply "
                           "(len=%d)", res);
        }
        os_memcpy(l2->own_addr, reply, ETH_ALEN);

        eloop_register_read_sock(l2->fd, l2_packet_receive, l2, NULL);

        return l2;

fail:
        close(l2->fd);
        l2->fd = -1;
        unlink(l2->own_socket_path);
        os_free(l2->own_socket_path);
        l2->own_socket_path = NULL;
        os_free(l2);
        return NULL;
}


void l2_packet_deinit(struct l2_packet_data *l2)
{
        if (l2 == NULL)
                return;

        if (l2->fd >= 0) {
                wpa_priv_cmd(l2, PRIVSEP_CMD_L2_UNREGISTER, NULL, 0);
                eloop_unregister_read_sock(l2->fd);
                close(l2->fd);
        }

        if (l2->own_socket_path) {
                unlink(l2->own_socket_path);
                os_free(l2->own_socket_path);
        }
                
        os_free(l2);
}


int l2_packet_get_ip_addr(struct l2_packet_data *l2, char *buf, size_t len)
{
        /* TODO */
        return -1;
}


void l2_packet_notify_auth_start(struct l2_packet_data *l2)
{
        wpa_priv_cmd(l2, PRIVSEP_CMD_L2_NOTIFY_AUTH_START, NULL, 0);
}