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Check correctly the packet length (CVE-2015-8605) 

XXX: pullup-6, pullup-7
This commit is contained in:
christos 2016-01-08 23:09:41 +00:00
parent 3ec8d00a3d
commit 1b08c7b3a2
1 changed files with 38 additions and 18 deletions
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56
external/bsd/dhcp/dist/common/packet.c vendored
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@ -1,4 +1,4 @@
/* $NetBSD: packet.c,v 1.1.1.4 2014/07/12 11:57:46 spz Exp $ */
/* $NetBSD: packet.c,v 1.2 2016/01/08 23:09:41 christos Exp $ */
/* packet.c
Packet assembly code, originally contributed by Archie Cobbs. */
@ -34,7 +34,7 @@
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: packet.c,v 1.1.1.4 2014/07/12 11:57:46 spz Exp $");
__RCSID("$NetBSD: packet.c,v 1.2 2016/01/08 23:09:41 christos Exp $");
#include "dhcpd.h"
@ -224,7 +224,28 @@ ssize_t decode_hw_header (interface, buf, bufix, from)
}
}
/* UDP header and IP header decoded together for convenience. */
/*!
*
* \brief UDP header and IP header decoded together for convenience.
*
* Attempt to decode the UDP and IP headers and, if necessary, checksum
* the packet.
*
* \param inteface - the interface on which the packet was recevied
* \param buf - a pointer to the buffer for the received packet
* \param bufix - where to start processing the buffer, previous
* routines may have processed parts of the buffer already
* \param from - space to return the address of the packet sender
* \param buflen - remaining length of the buffer, this will have been
* decremented by bufix by the caller
* \param rbuflen - space to return the length of the payload from the udp
* header
* \param csum_ready - indication if the checksum is valid for use
* non-zero indicates the checksum should be validated
*
* \return - the index to the first byte of the udp payload (that is the
* start of the DHCP packet
*/
ssize_t
decode_udp_ip_header(struct interface_info *interface,
@ -235,7 +256,7 @@ decode_udp_ip_header(struct interface_info *interface,
unsigned char *data;
struct ip ip;
struct udphdr udp;
unsigned char *upp, *endbuf;
unsigned char *upp;
u_int32_t ip_len, ulen, pkt_len;
u_int32_t sum, usum;
static int ip_packets_seen;
@ -246,11 +267,8 @@ decode_udp_ip_header(struct interface_info *interface,
static int udp_packets_length_overflow;
unsigned len;
/* Designate the end of the input buffer for bounds checks. */
endbuf = buf + bufix + buflen;
/* Assure there is at least an IP header there. */
if ((buf + bufix + sizeof(ip)) > endbuf)
if (sizeof(ip) > buflen)
return -1;
/* Copy the IP header into a stack aligned structure for inspection.
@ -262,13 +280,17 @@ decode_udp_ip_header(struct interface_info *interface,
ip_len = (*upp & 0x0f) << 2;
upp += ip_len;
/* Check the IP packet length. */
/* Check packet lengths are within the buffer:
* first the ip header (ip_len)
* then the packet length from the ip header (pkt_len)
* then the udp header (ip_len + sizeof(udp)
* We are liberal in what we accept, the udp payload should fit within
* pkt_len, but we only check against the full buffer size.
*/
pkt_len = ntohs(ip.ip_len);
if (pkt_len > buflen)
return -1;
/* Assure after ip_len bytes that there is enough room for a UDP header. */
if ((upp + sizeof(udp)) > endbuf)
if ((ip_len > buflen) ||
(pkt_len > buflen) ||
((ip_len + sizeof(udp)) > buflen))
return -1;
/* Copy the UDP header into a stack aligned structure for inspection. */
@ -289,7 +311,8 @@ decode_udp_ip_header(struct interface_info *interface,
return -1;
udp_packets_length_checked++;
if ((upp + ulen) > endbuf) {
/* verify that the payload length from the udp packet fits in the buffer */
if ((ip_len + ulen) > buflen) {
udp_packets_length_overflow++;
if ((udp_packets_length_checked > 4) &&
((udp_packets_length_checked /
@ -303,9 +326,6 @@ decode_udp_ip_header(struct interface_info *interface,
return -1;
}
if ((ulen < sizeof(udp)) || ((upp + ulen) > endbuf))
return -1;
/* Check the IP header checksum - it should be zero. */
++ip_packets_seen;
if (wrapsum (checksum (buf + bufix, ip_len, 0))) {