71c6c44d8d
- add static in a number of places - initialize __progname rather than rely on magical extern values - use nitems() instead of manually spelling it out - unshadow 'idi' - teach 'error' that it is '__dead2' - add missing 'break'
488 lines
14 KiB
C
488 lines
14 KiB
C
/* $OpenBSD: bpf.c,v 1.13 2004/05/05 14:28:58 deraadt Exp $ */
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/* BPF socket interface code, originally contributed by Archie Cobbs. */
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/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1995, 1996, 1998, 1999
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* The Internet Software Consortium. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of The Internet Software Consortium nor the names
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* of its contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
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* CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This software has been written for the Internet Software Consortium
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* by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
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* Enterprises. To learn more about the Internet Software Consortium,
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* see ``http://www.vix.com/isc''. To learn more about Vixie
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* Enterprises, see ``http://www.vix.com''.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "dhcpd.h"
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#include "privsep.h"
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#include <sys/capsicum.h>
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#include <sys/ioctl.h>
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#include <sys/uio.h>
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#include <net/bpf.h>
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#include <netinet/in_systm.h>
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#include <netinet/ip.h>
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#include <netinet/udp.h>
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#include <netinet/if_ether.h>
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#define BPF_FORMAT "/dev/bpf%d"
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/*
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* Called by get_interface_list for each interface that's discovered.
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* Opens a packet filter for each interface and adds it to the select
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* mask.
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*/
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int
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if_register_bpf(struct interface_info *info, int flags)
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{
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char filename[50];
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int sock, b;
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/* Open a BPF device */
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for (b = 0;; b++) {
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snprintf(filename, sizeof(filename), BPF_FORMAT, b);
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sock = open(filename, flags);
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if (sock < 0) {
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if (errno == EBUSY)
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continue;
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else
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error("Can't find free bpf: %m");
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} else
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break;
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}
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/* Set the BPF device to point at this interface. */
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if (ioctl(sock, BIOCSETIF, info->ifp) < 0)
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error("Can't attach interface %s to bpf device %s: %m",
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info->name, filename);
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return (sock);
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}
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/*
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* Packet write filter program:
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* 'ip and udp and src port bootps and dst port (bootps or bootpc)'
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*/
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static struct bpf_insn dhcp_bpf_wfilter[] = {
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BPF_STMT(BPF_LD + BPF_B + BPF_IND, 14),
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, (IPVERSION << 4) + 5, 0, 12),
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/* Make sure this is an IP packet... */
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BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 10),
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/* Make sure it's a UDP packet... */
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BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 8),
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/* Make sure this isn't a fragment... */
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BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
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BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 6, 0), /* patched */
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/* Get the IP header length... */
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BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
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/* Make sure it's from the right port... */
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BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14),
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 68, 0, 3),
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/* Make sure it is to the right ports ... */
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BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1),
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/* If we passed all the tests, ask for the whole packet. */
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BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
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/* Otherwise, drop it. */
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BPF_STMT(BPF_RET+BPF_K, 0),
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};
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static int dhcp_bpf_wfilter_len = nitems(dhcp_bpf_wfilter);
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void
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if_register_send(struct interface_info *info)
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{
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cap_rights_t rights;
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struct bpf_version v;
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struct bpf_program p;
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int sock, on = 1;
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/* Open a BPF device and hang it on this interface... */
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info->wfdesc = if_register_bpf(info, O_WRONLY);
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/* Make sure the BPF version is in range... */
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if (ioctl(info->wfdesc, BIOCVERSION, &v) < 0)
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error("Can't get BPF version: %m");
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if (v.bv_major != BPF_MAJOR_VERSION ||
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v.bv_minor < BPF_MINOR_VERSION)
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error("Kernel BPF version out of range - recompile dhcpd!");
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/* Set up the bpf write filter program structure. */
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p.bf_len = dhcp_bpf_wfilter_len;
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p.bf_insns = dhcp_bpf_wfilter;
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if (dhcp_bpf_wfilter[7].k == 0x1fff)
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dhcp_bpf_wfilter[7].k = htons(IP_MF|IP_OFFMASK);
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if (ioctl(info->wfdesc, BIOCSETWF, &p) < 0)
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error("Can't install write filter program: %m");
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if (ioctl(info->wfdesc, BIOCLOCK, NULL) < 0)
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error("Cannot lock bpf");
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cap_rights_init(&rights, CAP_WRITE);
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if (cap_rights_limit(info->wfdesc, &rights) < 0 && errno != ENOSYS)
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error("Can't limit bpf descriptor: %m");
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/*
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* Use raw socket for unicast send.
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*/
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if ((sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP)) == -1)
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error("socket(SOCK_RAW): %m");
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if (setsockopt(sock, IPPROTO_IP, IP_HDRINCL, &on,
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sizeof(on)) == -1)
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error("setsockopt(IP_HDRINCL): %m");
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info->ufdesc = sock;
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}
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/*
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* Packet filter program...
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*
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* XXX: Changes to the filter program may require changes to the
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* constant offsets used in if_register_send to patch the BPF program!
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*/
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static struct bpf_insn dhcp_bpf_filter[] = {
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/* Make sure this is an IP packet... */
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BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
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/* Make sure it's a UDP packet... */
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BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
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/* Make sure this isn't a fragment... */
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BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
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BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
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/* Get the IP header length... */
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BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
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/* Make sure it's to the right port... */
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BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1), /* patch */
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/* If we passed all the tests, ask for the whole packet. */
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BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
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/* Otherwise, drop it. */
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BPF_STMT(BPF_RET+BPF_K, 0),
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};
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static int dhcp_bpf_filter_len = nitems(dhcp_bpf_filter);
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void
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if_register_receive(struct interface_info *info)
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{
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static const unsigned long cmds[2] = { SIOCGIFFLAGS, SIOCGIFMEDIA };
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cap_rights_t rights;
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struct bpf_version v;
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struct bpf_program p;
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int flag = 1, sz;
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/* Open a BPF device and hang it on this interface... */
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info->rfdesc = if_register_bpf(info, O_RDONLY);
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/* Make sure the BPF version is in range... */
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if (ioctl(info->rfdesc, BIOCVERSION, &v) < 0)
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error("Can't get BPF version: %m");
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if (v.bv_major != BPF_MAJOR_VERSION ||
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v.bv_minor < BPF_MINOR_VERSION)
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error("Kernel BPF version out of range - recompile dhcpd!");
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/*
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* Set immediate mode so that reads return as soon as a packet
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* comes in, rather than waiting for the input buffer to fill
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* with packets.
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*/
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if (ioctl(info->rfdesc, BIOCIMMEDIATE, &flag) < 0)
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error("Can't set immediate mode on bpf device: %m");
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/* Get the required BPF buffer length from the kernel. */
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if (ioctl(info->rfdesc, BIOCGBLEN, &sz) < 0)
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error("Can't get bpf buffer length: %m");
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info->rbuf_max = sz;
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info->rbuf = malloc(info->rbuf_max);
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if (!info->rbuf)
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error("Can't allocate %lu bytes for bpf input buffer.",
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(unsigned long)info->rbuf_max);
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info->rbuf_offset = 0;
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info->rbuf_len = 0;
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/* Set up the bpf filter program structure. */
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p.bf_len = dhcp_bpf_filter_len;
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p.bf_insns = dhcp_bpf_filter;
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/* Patch the server port into the BPF program...
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*
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* XXX: changes to filter program may require changes to the
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* insn number(s) used below!
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*/
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dhcp_bpf_filter[8].k = LOCAL_PORT;
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if (ioctl(info->rfdesc, BIOCSETF, &p) < 0)
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error("Can't install packet filter program: %m");
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if (ioctl(info->rfdesc, BIOCLOCK, NULL) < 0)
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error("Cannot lock bpf");
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cap_rights_init(&rights, CAP_IOCTL, CAP_EVENT, CAP_READ);
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if (cap_rights_limit(info->rfdesc, &rights) < 0 && errno != ENOSYS)
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error("Can't limit bpf descriptor: %m");
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if (cap_ioctls_limit(info->rfdesc, cmds, 2) < 0 && errno != ENOSYS)
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error("Can't limit ioctls for bpf descriptor: %m");
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}
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void
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send_packet_unpriv(int privfd, struct dhcp_packet *raw, size_t len,
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struct in_addr from, struct in_addr to)
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{
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struct imsg_hdr hdr;
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struct buf *buf;
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int errs;
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hdr.code = IMSG_SEND_PACKET;
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hdr.len = sizeof(hdr) +
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sizeof(size_t) + len +
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sizeof(from) + sizeof(to);
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if ((buf = buf_open(hdr.len)) == NULL)
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error("buf_open: %m");
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errs = 0;
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errs += buf_add(buf, &hdr, sizeof(hdr));
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errs += buf_add(buf, &len, sizeof(len));
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errs += buf_add(buf, raw, len);
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errs += buf_add(buf, &from, sizeof(from));
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errs += buf_add(buf, &to, sizeof(to));
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if (errs)
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error("buf_add: %m");
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if (buf_close(privfd, buf) == -1)
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error("buf_close: %m");
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}
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void
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send_packet_priv(struct interface_info *interface, struct imsg_hdr *hdr, int fd)
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{
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unsigned char buf[256];
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struct iovec iov[2];
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struct msghdr msg;
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struct dhcp_packet raw;
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size_t len;
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struct in_addr from, to;
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int result, bufp = 0;
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if (hdr->len < sizeof(*hdr) + sizeof(size_t))
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error("corrupted message received");
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buf_read(fd, &len, sizeof(len));
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if (hdr->len != sizeof(*hdr) + sizeof(size_t) + len +
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sizeof(from) + sizeof(to)) {
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error("corrupted message received");
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}
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if (len > sizeof(raw))
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error("corrupted message received");
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buf_read(fd, &raw, len);
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buf_read(fd, &from, sizeof(from));
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buf_read(fd, &to, sizeof(to));
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/* Assemble the headers... */
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if (to.s_addr == INADDR_BROADCAST)
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assemble_hw_header(interface, buf, &bufp);
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assemble_udp_ip_header(buf, &bufp, from.s_addr, to.s_addr,
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htons(REMOTE_PORT), (unsigned char *)&raw, len);
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iov[0].iov_base = buf;
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iov[0].iov_len = bufp;
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iov[1].iov_base = &raw;
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iov[1].iov_len = len;
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/* Fire it off */
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if (to.s_addr == INADDR_BROADCAST)
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result = writev(interface->wfdesc, iov, 2);
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else {
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struct sockaddr_in sato;
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sato.sin_addr = to;
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sato.sin_port = htons(REMOTE_PORT);
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sato.sin_family = AF_INET;
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sato.sin_len = sizeof(sato);
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memset(&msg, 0, sizeof(msg));
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msg.msg_name = (struct sockaddr *)&sato;
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msg.msg_namelen = sizeof(sato);
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msg.msg_iov = iov;
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msg.msg_iovlen = 2;
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result = sendmsg(interface->ufdesc, &msg, 0);
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}
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if (result < 0)
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warning("send_packet: %m");
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}
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ssize_t
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receive_packet(struct interface_info *interface, unsigned char *buf,
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size_t len, struct sockaddr_in *from, struct hardware *hfrom)
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{
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int length = 0, offset = 0;
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struct bpf_hdr hdr;
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/*
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* All this complexity is because BPF doesn't guarantee that
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* only one packet will be returned at a time. We're getting
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* what we deserve, though - this is a terrible abuse of the BPF
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* interface. Sigh.
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*/
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/* Process packets until we get one we can return or until we've
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* done a read and gotten nothing we can return...
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*/
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do {
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/* If the buffer is empty, fill it. */
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if (interface->rbuf_offset >= interface->rbuf_len) {
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length = read(interface->rfdesc, interface->rbuf,
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interface->rbuf_max);
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if (length <= 0)
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return (length);
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interface->rbuf_offset = 0;
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interface->rbuf_len = length;
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}
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/*
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* If there isn't room for a whole bpf header, something
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* went wrong, but we'll ignore it and hope it goes
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* away... XXX
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*/
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if (interface->rbuf_len - interface->rbuf_offset <
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sizeof(hdr)) {
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interface->rbuf_offset = interface->rbuf_len;
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continue;
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}
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/* Copy out a bpf header... */
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memcpy(&hdr, &interface->rbuf[interface->rbuf_offset],
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sizeof(hdr));
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/*
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* If the bpf header plus data doesn't fit in what's
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* left of the buffer, stick head in sand yet again...
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*/
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if (interface->rbuf_offset + hdr.bh_hdrlen + hdr.bh_caplen >
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interface->rbuf_len) {
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interface->rbuf_offset = interface->rbuf_len;
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continue;
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}
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/* Skip over the BPF header... */
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interface->rbuf_offset += hdr.bh_hdrlen;
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/*
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* If the captured data wasn't the whole packet, or if
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* the packet won't fit in the input buffer, all we can
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* do is drop it.
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*/
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if (hdr.bh_caplen != hdr.bh_datalen) {
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interface->rbuf_offset =
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BPF_WORDALIGN(interface->rbuf_offset +
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hdr.bh_caplen);
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continue;
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}
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/* Decode the physical header... */
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offset = decode_hw_header(interface->rbuf,
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interface->rbuf_offset, hfrom);
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/*
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* If a physical layer checksum failed (dunno of any
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* physical layer that supports this, but WTH), skip
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* this packet.
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*/
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if (offset < 0) {
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interface->rbuf_offset =
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BPF_WORDALIGN(interface->rbuf_offset +
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hdr.bh_caplen);
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continue;
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}
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interface->rbuf_offset += offset;
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hdr.bh_caplen -= offset;
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/* Decode the IP and UDP headers... */
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offset = decode_udp_ip_header(interface->rbuf,
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interface->rbuf_offset, from, NULL, hdr.bh_caplen);
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/* If the IP or UDP checksum was bad, skip the packet... */
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if (offset < 0) {
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interface->rbuf_offset =
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BPF_WORDALIGN(interface->rbuf_offset +
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hdr.bh_caplen);
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continue;
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}
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interface->rbuf_offset += offset;
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hdr.bh_caplen -= offset;
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/*
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* If there's not enough room to stash the packet data,
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* we have to skip it (this shouldn't happen in real
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* life, though).
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*/
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if (hdr.bh_caplen > len) {
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interface->rbuf_offset =
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BPF_WORDALIGN(interface->rbuf_offset +
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hdr.bh_caplen);
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|
continue;
|
|
}
|
|
|
|
/* Copy out the data in the packet... */
|
|
memcpy(buf, interface->rbuf + interface->rbuf_offset,
|
|
hdr.bh_caplen);
|
|
interface->rbuf_offset =
|
|
BPF_WORDALIGN(interface->rbuf_offset +
|
|
hdr.bh_caplen);
|
|
return (hdr.bh_caplen);
|
|
} while (!length);
|
|
return (0);
|
|
}
|