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nmap/libnetutil/UDPHeader.cc

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/***************************************************************************
* UDPHeader.cc -- The UDPHeader Class represents a UDP packet. It *
* contains methods to set the different header fields. These methods *
* tipically perform the necessary error checks and byte order *
* conversions. *
* *
***********************IMPORTANT NMAP LICENSE TERMS************************
* *
* The Nmap Security Scanner is (C) 1996-2012 Insecure.Com LLC. Nmap is *
* also a registered trademark of Insecure.Com LLC. This program is free *
* software; you may redistribute and/or modify it under the terms of the *
* GNU General Public License as published by the Free Software *
* Foundation; Version 2 with the clarifications and exceptions described *
* below. This guarantees your right to use, modify, and redistribute *
* this software under certain conditions. If you wish to embed Nmap *
* technology into proprietary software, we sell alternative licenses *
* (contact sales@insecure.com). Dozens of software vendors already *
* license Nmap technology such as host discovery, port scanning, OS *
* detection, version detection, and the Nmap Scripting Engine. *
* *
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* This program is distributed in the hope that it will be useful, but *
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* *
***************************************************************************/
/* This code was originally part of the Nping tool. */
#include "UDPHeader.h"
/******************************************************************************/
/* CONTRUCTORS, DESTRUCTORS AND INITIALIZATION METHODS */
/******************************************************************************/
UDPHeader::UDPHeader(){
this->reset();
} /* End of UDPHeader constructor */
UDPHeader::~UDPHeader(){
} /* End of UDPHeader destructor */
/** Sets every attribute to its default value */
void UDPHeader::reset(){
this->length=UDP_HEADER_LEN;
this->setSourcePort(UDP_DEFAULT_SPORT);
this->setDestinationPort(UDP_DEFAULT_DPORT);
this->setTotalLength(UDP_HEADER_LEN);
this->setSum(0);
} /* End of reset() */
/******************************************************************************/
/* PacketElement:: OVERWRITTEN METHODS */
/******************************************************************************/
/** @warning This method is essential for the superclass getBinaryBuffer()
* method to work. Do NOT change a thing unless you know what you're doing */
u8 * UDPHeader::getBufferPointer(){
return (u8*)(&h);
} /* End of getBufferPointer() */
/** Stores supplied packet in the internal buffer so the information
* can be accessed using the standard get & set methods.
* @warning The UDPHeader class is able to hold a maximum of 8 bytes. If the
* supplied buffer is longer than that, only the first 8 bytes will be stored
* in the internal buffer.
* @warning Supplied len MUST be at least 8 bytes (UDP header length).
* @return OP_SUCCESS on success and OP_FAILURE in case of error */
int UDPHeader::storeRecvData(const u8 *buf, size_t len){
if(buf==NULL || len<UDP_HEADER_LEN){
return OP_FAILURE;
}else{
this->reset(); /* Re-init the object, just in case the caller had used it already */
this->length=UDP_HEADER_LEN;
memcpy(&(this->h), buf, UDP_HEADER_LEN);
}
return OP_SUCCESS;
} /* End of storeRecvData() */
/* Returns a protocol identifier. This is used by packet parsing funtions
* that return linked lists of PacketElement objects, to determine the protocol
* the object represents. */
int UDPHeader::protocol_id() const {
return HEADER_TYPE_UDP;
} /* End of protocol_id() */
/** Determines if the data stored in the object after an storeRecvData() call
* is valid and safe to use. This mainly checks the length of the data but may
* also test the value of certain protocol fields to ensure their correctness.
* @return the length, in bytes, of the header, if its found to be valid or
* OP_FAILURE (-1) otherwise. */
int UDPHeader::validate(){
if( this->length!=UDP_HEADER_LEN)
return OP_FAILURE;
else
return UDP_HEADER_LEN;
} /* End of validate() */
/** Prints the contents of the header and calls print() on the next protocol
* header in the chain (if there is any).
* @return OP_SUCCESS on success and OP_FAILURE in case of error. */
int UDPHeader::print(FILE *output, int detail) const {
fprintf(output, "UDP[");
fprintf(output, "%d", this->getSourcePort());
fprintf(output, " >");
fprintf(output, " %d", this->getDestinationPort());
if(detail>=PRINT_DETAIL_HIGH)
fprintf(output, " len=%d", (int)this->getTotalLength() );
if(detail>=PRINT_DETAIL_MED)
fprintf(output, " csum=0x%04X", ntohs( this->getSum() ));
fprintf(output, "]");
if(this->next!=NULL){
print_separator(output, detail);
next->print(output, detail);
}
return OP_SUCCESS;
} /* End of print() */
/******************************************************************************/
/* PROTOCOL-SPECIFIC METHODS */
/******************************************************************************/
/** Sets source port.
* @warning Port must be supplied in host byte order. This method performs
* byte order conversion using htons() */
int UDPHeader::setSourcePort(u16 p){
h.uh_sport = htons(p);
return OP_SUCCESS;
} /* End of setSrcPort() */
/** Returns source port in HOST byte order */
u16 UDPHeader::getSourcePort() const {
return ntohs(h.uh_sport);
} /* End of getSrcPort() */
/** Sets destination port.
* @warning Port must be supplied in host byte order. This method performs
* byte order conversion using htons() */
int UDPHeader::setDestinationPort(u16 p){
h.uh_dport = htons(p);
return OP_SUCCESS;
} /* End of setDstPort() */
/** Returns destination port in HOST byte order */
u16 UDPHeader::getDestinationPort() const {
return ntohs(h.uh_dport);
} /* End of getDstPort() */
int UDPHeader::setSum(struct in_addr src, struct in_addr dst){
int bufflen;
u8 aux[ 65535-8 ];
/* FROM: RFC 5405 Unicast UDP Usage Guidelines, November 2008
* "A UDP datagram is carried in a single IP packet and is hence limited to
* a maximum payload of 65,507 bytes for IPv4 and 65,527 bytes for IPv6"
*
* So, UDP is supposed to be able to carry 65535-8 bytes but in fact it can
* only carry 65,507 or 65,527. However, we are not taking that into account
* here because UDP is supposed to be independent of IPv4, IPv6 or
* whatever other network layer protocol is used to carry the UDP datagrams.*/
h.uh_sum = 0;
/* Copy packet contents to a buffer */
bufflen=dumpToBinaryBuffer(aux, 65536-8 );
/* Compute checksum */
h.uh_sum = ipv4_pseudoheader_cksum(&src, &dst, IPPROTO_UDP,bufflen, (char *) aux);
return OP_SUCCESS;
} /* End of setSum() */
/** @warning Sum is set to supplied value with NO byte ordering conversion
* performed. */
int UDPHeader::setSum(u16 s){
h.uh_sum = s;
return OP_SUCCESS;
} /* End of setSum() */
int UDPHeader::setSum(){
this->h.uh_sum=0;
this->h.uh_sum = this->compute_checksum();
return OP_SUCCESS;
} /* End of setSum() */
/** Set the UDP checksum field to a random value, which may accidentally
* match the correct checksum */
int UDPHeader::setSumRandom(){
h.uh_sum=(1 + (get_random_u16()%(65535-1))); /* Discard value zero */
return OP_SUCCESS;
} /* End of setSumRandom() */
/** Set the UDP checksum field to a random value. It takes the source and
* destination address to make sure the random generated sum does not
* accidentally match the correct checksum. This function only handles
* IPv4 address. */
int UDPHeader::setSumRandom(struct in_addr source, struct in_addr destination){
u16 correct_csum=0;
/* Compute the correct checksum */
this->setSum(source, destination);
correct_csum=this->getSum();
/* Generate numbers until one does not match the correct sum */
while( (h.uh_sum=(1 + (get_random_u16()%(65535-1))))==correct_csum);
return OP_SUCCESS;
} /* End of setSumRandom() */
u16 UDPHeader::getSum() const {
return h.uh_sum;
} /* End of getSum() */
int UDPHeader::setTotalLength(){
int mylen = 8;
int otherslen=0;
if (next!=NULL)
otherslen=next->getLen();
/* FROM: RFC 5405 Unicast UDP Usage Guidelines, November 2008
* "A UDP datagram is carried in a single IP packet and is hence limited to
* a maximum payload of 65,507 bytes for IPv4 and 65,527 bytes for IPv6"
*
* So, UDP is supposed to be able to carry 65535-8 bytes but in fact it can
* only carry 65,507 or 65,527. However, we are not taking that into account
* here because UDP is supposed to be independent of IPv4, IPv6 or
* whatever other network layer protocol is used to carry the UDP datagrams.*/
if ((mylen+otherslen) > 65535 || (mylen+otherslen)<8 ){
printf("UDPHeader::setTotalLenght(): Invalid length.\n");
return OP_FAILURE;
}
h.uh_ulen=htons( mylen+otherslen );
return OP_SUCCESS;
} /* End of setTotalLenght() */
/** @warning Supplied value MUST be in HOST byte order */
int UDPHeader::setTotalLength(u16 l){
this->h.uh_ulen=htons(l);
return OP_SUCCESS;
} /* End of setTotalLenght() */
/** @warning Returned value is in HOST byte order */
u16 UDPHeader::getTotalLength() const {
return ntohs(this->h.uh_ulen);
} /* End of getTotalLenght() */
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