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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) 1996-2016 Insecure.Com LLC ("The Nmap *
* Project"). Nmap is also a registered trademark of the Nmap Project. *
* 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 ("GPL"), BUT ONLY WITH ALL OF THE *
* CLARIFICATIONS AND EXCEPTIONS DESCRIBED HEREIN. 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@nmap.com). *
* Dozens of software vendors already license Nmap technology such as *
* host discovery, port scanning, OS detection, version detection, and *
* the Nmap Scripting Engine. *
* *
* Note that the GPL places important restrictions on "derivative works", *
* yet it does not provide a detailed definition of that term. To avoid *
* misunderstandings, we interpret that term as broadly as copyright law *
* allows. For example, we consider an application to constitute a *
* derivative work for the purpose of this license if it does any of the *
* following with any software or content covered by this license *
* ("Covered Software"): *
* *
* o Integrates source code from Covered Software. *
* *
* o Reads or includes copyrighted data files, such as Nmap's nmap-os-db *
* or nmap-service-probes. *
* *
* o Is designed specifically to execute Covered Software and parse the *
* results (as opposed to typical shell or execution-menu apps, which will *
* execute anything you tell them to). *
* *
* o Includes Covered Software in a proprietary executable installer. The *
* installers produced by InstallShield are an example of this. Including *
* Nmap with other software in compressed or archival form does not *
* trigger this provision, provided appropriate open source decompression *
* or de-archiving software is widely available for no charge. For the *
* purposes of this license, an installer is considered to include Covered *
* Software even if it actually retrieves a copy of Covered Software from *
* another source during runtime (such as by downloading it from the *
* Internet). *
* *
* o Links (statically or dynamically) to a library which does any of the *
* above. *
* *
* o Executes a helper program, module, or script to do any of the above. *
* *
* This list is not exclusive, but is meant to clarify our interpretation *
* of derived works with some common examples. Other people may interpret *
* the plain GPL differently, so we consider this a special exception to *
* the GPL that we apply to Covered Software. Works which meet any of *
* these conditions must conform to all of the terms of this license, *
* particularly including the GPL Section 3 requirements of providing *
* source code and allowing free redistribution of the work as a whole. *
* *
* As another special exception to the GPL terms, the Nmap Project grants *
* permission to link the code of this program with any version of the *
* OpenSSL library which is distributed under a license identical to that *
* listed in the included docs/licenses/OpenSSL.txt file, and distribute *
* linked combinations including the two. *
* *
* The Nmap Project has permission to redistribute Npcap, a packet *
* capturing driver and library for the Microsoft Windows platform. *
* Npcap is a separate work with it's own license rather than this Nmap *
* license. Since the Npcap license does not permit redistribution *
* without special permission, our Nmap Windows binary packages which *
* contain Npcap may not be redistributed without special permission. *
* *
* Any redistribution of Covered Software, including any derived works, *
* must obey and carry forward all of the terms of this license, including *
* obeying all GPL rules and restrictions. For example, source code of *
* the whole work must be provided and free redistribution must be *
* allowed. All GPL references to "this License", are to be treated as *
* including the terms and conditions of this license text as well. *
* *
* Because this license imposes special exceptions to the GPL, Covered *
* Work may not be combined (even as part of a larger work) with plain GPL *
* software. The terms, conditions, and exceptions of this license must *
* be included as well. This license is incompatible with some other open *
* source licenses as well. In some cases we can relicense portions of *
* Nmap or grant special permissions to use it in other open source *
* software. Please contact fyodor@nmap.org with any such requests. *
* Similarly, we don't incorporate incompatible open source software into *
* Covered Software without special permission from the copyright holders. *
* *
* If you have any questions about the licensing restrictions on using *
* Nmap in other works, are happy to help. As mentioned above, we also *
* offer alternative license to integrate Nmap into proprietary *
* applications and appliances. These contracts have been sold to dozens *
* of software vendors, and generally include a perpetual license as well *
* as providing for priority support and updates. They also fund the *
* continued development of Nmap. Please email sales@nmap.com for further *
* information. *
* *
* If you have received a written license agreement or contract for *
* Covered Software stating terms other than these, you may choose to use *
* and redistribute Covered Software under those terms instead of these. *
* *
* Source is provided to this software because we believe users have a *
* right to know exactly what a program is going to do before they run it. *
* This also allows you to audit the software for security holes. *
* *
* Source code also allows you to port Nmap to new platforms, fix bugs, *
* and add new features. You are highly encouraged to send your changes *
* to the dev@nmap.org mailing list for possible incorporation into the *
* main distribution. By sending these changes to Fyodor or one of the *
* Insecure.Org development mailing lists, or checking them into the Nmap *
* source code repository, it is understood (unless you specify *
* otherwise) that you are offering the Nmap Project the unlimited, *
* non-exclusive right to reuse, modify, and relicense the code. Nmap *
* will always be available Open Source, but this is important because *
* the inability to relicense code has caused devastating problems for *
* other Free Software projects (such as KDE and NASM). We also *
* occasionally relicense the code to third parties as discussed above. *
* If you wish to specify special license conditions of your *
* contributions, just say so when you send them. *
* *
* This program is distributed in the hope that it will be useful, but *
* WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the Nmap *
* license file for more details (it's in a COPYING file included with *
* Nmap, and also available from https://svn.nmap.org/nmap/COPYING) *
* *
***************************************************************************/
/* 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::setTotalLength(): Invalid length.\n");
return OP_FAILURE;
}
h.uh_ulen=htons( mylen+otherslen );
return OP_SUCCESS;
} /* End of setTotalLength() */
/** @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 setTotalLength() */
/** @warning Returned value is in HOST byte order */
u16 UDPHeader::getTotalLength() const {
return ntohs(this->h.uh_ulen);
} /* End of getTotalLength() */
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