/*************************************************************************** * 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. * * * * Note that the GPL places important restrictions on "derived 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: * * o Integrates source code from Nmap * * o Reads or includes Nmap copyrighted data files, such as * * nmap-os-db or nmap-service-probes. * * o Executes Nmap and parses the results (as opposed to typical shell or * * execution-menu apps, which simply display raw Nmap output and so are * * not derivative works.) * * o Integrates/includes/aggregates Nmap into a proprietary executable * * installer, such as those produced by InstallShield. * * o Links to a library or executes a program that does any of the above * * * * The term "Nmap" should be taken to also include any portions or derived * * works of Nmap, as well as other software we distribute under this * * license such as Zenmap, Ncat, and Nping. This list is not exclusive, * * but is meant to clarify our interpretation of derived works with some * * common examples. Our interpretation applies only to Nmap--we don't * * speak for other people's GPL works. * * * * If you have any questions about the GPL licensing restrictions on using * * Nmap in non-GPL works, we would be 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@insecure.com for * * further information. * * * * As a special exception to the GPL terms, Insecure.Com LLC 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. You must obey the GNU GPL in all * * respects for all of the code used other than OpenSSL. If you modify * * this file, you may extend this exception to your version of the file, * * but you are not obligated to do so. * * * * If you received these files with a written license agreement or * * contract stating terms other than the terms above, then that * * alternative license agreement takes precedence over these comments. * * * * 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 (none * * have been found so far). * * * * 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 nmap-dev@insecure.org 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 (Insecure.Com LLC) 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 GNU * * General Public License v2.0 for more details at * * http://www.gnu.org/licenses/gpl-2.0.html , or in the COPYING file * * included with Nmap. * * * ***************************************************************************/ /* 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 || lenreset(); /* 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() */