PenTest/nmap
1
0
Fork 0
mirror of https://github.com/nmap/nmap.git synced 2025-12-18 13:39:02 +00:00
Code Issues Projects Releases Wiki Activity

Fix UDP checksum generation (0 -> 0xffff)

Browse Source 
See changelog and http://seclists.org/nmap-dev/2013/q4/122
This commit is contained in:
dmiller
2013-11-06 02:46:20 +00:00
parent bce4bcf7f9
commit 77f1429a56
2 changed files with 16 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
CHANGELOG
View File

@@ -1,5 +1,10 @@
# Nmap Changelog ($Id$); -*-text-*- # Nmap Changelog ($Id$); -*-text-*-
o Fixed a bug with UDP checksum calculation. When the UDP checksum is zero
(0x0000), it must be transmitted as 1's-complement -0 (0xffff) to avoid
ambiguity with +0, which indicates no checksum was calculated. This affected
UDP on IPv4 only. Reported by Michael Weber. [Daniel Miller]
o [NSE] Removed a fixed value (28428) which was being set for the Request ID in o [NSE] Removed a fixed value (28428) which was being set for the Request ID in
the snmpWalk library function; a value based on nmap.clock_ms will now be set the snmpWalk library function; a value based on nmap.clock_ms will now be set
instead. [jah] instead. [jah]

13
libnetutil/netutil.cc
View File

@@ -844,7 +844,15 @@ unsigned short ipv4_pseudoheader_cksum(const struct in_addr *src,
sum = ip_cksum_add(hstart, len, sum); sum = ip_cksum_add(hstart, len, sum);
/* Fold in the carry, take the complement, and return. */ /* Fold in the carry, take the complement, and return. */
return ip_cksum_carry(sum); sum = ip_cksum_carry(sum);
/* RFC 768: "If the computed checksum is zero, it is transmitted as all
* ones (the equivalent in one's complement arithmetic). An all zero
* transmitted checksum value means that the transmitter generated no
* checksum" */
if (proto == IP_PROTO_UDP && sum == 0)
sum = 0xFFFF;
return sum;
} }
/* Calculate the Internet checksum of some given data concatenated with the /* Calculate the Internet checksum of some given data concatenated with the
@@ -868,6 +876,7 @@ u16 ipv6_pseudoheader_cksum(const struct in6_addr *src,
sum = ip_cksum_add(&hdr, sizeof(hdr), 0); sum = ip_cksum_add(&hdr, sizeof(hdr), 0);
sum = ip_cksum_add(hstart, len, sum); sum = ip_cksum_add(hstart, len, sum);
sum = ip_cksum_carry(sum);
/* RFC 2460: "Unlike IPv4, when UDP packets are originated by an IPv6 node, /* RFC 2460: "Unlike IPv4, when UDP packets are originated by an IPv6 node,
the UDP checksum is not optional. That is, whenever originating a UDP the UDP checksum is not optional. That is, whenever originating a UDP
packet, an IPv6 node must compute a UDP checksum over the packet and the packet, an IPv6 node must compute a UDP checksum over the packet and the
@@ -876,7 +885,7 @@ u16 ipv6_pseudoheader_cksum(const struct in6_addr *src,
if (nxt == IP_PROTO_UDP && sum == 0) if (nxt == IP_PROTO_UDP && sum == 0)
sum = 0xFFFF; sum = 0xFFFF;
return ip_cksum_carry(sum); return sum;
} }
void sethdrinclude(int sd) { void sethdrinclude(int sd) {