mirror of
https://github.com/RetroShare/RetroShare.git
synced 2025-08-16 10:01:14 -04:00
Add ability to retrieve External IP using DNS server.
IPV6 compatible.
This commit is contained in:
Phenom
parent
56d34a8a2c
commit
a09db6717b
8 changed files with 444 additions and 135 deletions
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@ -21,6 +21,9 @@
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* *
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*******************************************************************************/
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//#define DEBUG_SPEC_DNS 1
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#include "util/rsdebug.h"
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#include "util/rsnet.h"
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#include "util/rsthreads.h"
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#include "util/rsstring.h"
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@ -40,6 +43,72 @@
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#define BIG_ENDIAN 4321
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#endif
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//https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-2
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constexpr uint16_t DNSC_IN = 1; //Internet (IN)
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//https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-4
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constexpr uint16_t DNST_A = 1; //Ipv4 address
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constexpr uint16_t DNST_AAAA =28; //Ipv6 address
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///Need to pack as we use sizeof them. (avoid padding)
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#pragma pack(1)
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//DNS header structure
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struct DNS_HEADER
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{
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unsigned short id; // identification number
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//Header flags https://www.bind9.net/dns-header-flags
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unsigned char rd :1; //bit 07 Recursion Desired, indicates if the client means a recursive query
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unsigned char tc :1; //bit 06 TrunCation, indicates that this message was truncated due to excessive length
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unsigned char aa :1; //bit 05 Authoritative Answer, in a response, indicates if the DNS server is authoritative for the queried hostname
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unsigned char opcode :4;//bit 01-04 The type can be QUERY (standard query, 0), IQUERY (inverse query, 1), or STATUS (server status request, 2)
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unsigned char qr :1; //bit 00 Indicates if the message is a query (0) or a reply (1)
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unsigned char rcode :4; //bit 12-15 Response Code can be NOERROR (0), FORMERR (1, Format error), SERVFAIL (2), NXDOMAIN (3, Nonexistent domain), etc.
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unsigned char cd :1; //bit 11 Checking Disabled [RFC 4035][RFC 6840][RFC Errata 4927] used by DNSSEC
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unsigned char ad :1; //bit 10 Authentic Data [RFC 4035][RFC 6840][RFC Errata 4924] used by DNSSEC
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unsigned char z :1; //bit 09 Zero, reserved for future use
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unsigned char ra :1; //bit 08 Recursion Available [RFC 1035] in a response, indicates if the replying DNS server supports recursion
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unsigned short q_count; // number of question entries
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unsigned short ans_count; // number of answer entries
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unsigned short auth_count; // number of authority resource records entries
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unsigned short add_count; // number of additional resource record entries
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};
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//// OpCode text https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-5
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//static const char *opcodetext[] = { "QUERY", "IQUERY", "STATUS",
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// "RESERVED3", "NOTIFY", "UPDATE",
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// "STATEFUL", "RESERVED7", "RESERVED8",
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// "RESERVED9", "RESERVED10", "RESERVED11",
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// "RESERVED12", "RESERVED13", "RESERVED14",
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// "RESERVED15" };
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//// RCode text https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6
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//static const char *rcodetext[] = { "NOERROR", "FORMERR", "SERVFAIL",
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// "NXDOMAIN", "NOTIMP", "REFUSED",
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// "YXDOMAIN", "YXRRSET", "NXRRSET",
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// "NOTAUTH", "NOTZONE", "DSOTYPENI",
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// "RESERVED12", "RESERVED13", "RESERVED14",
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// "RESERVED15", "BADVERS", "BADKEY",
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// "BADTIME", "BADMODE", "BADNAME",
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// "BADALG", "BADTRUNC", "BADCOOKIE"};
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//Constant sized fields of query structure
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//https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml
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struct QUESTION
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{
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unsigned short qtype; //https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-4
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unsigned short qclass; //https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-2
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};
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//Constant sized fields of the resource record structure
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struct RR_DATA
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{
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unsigned short rtype; //https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-4
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unsigned short rclass; //https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-2
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unsigned int rttl; //Time To Live is the number of seconds left before the information expires. (32bits integer, so maximum 140 years)
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unsigned short data_len;//Lenght of following data
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};
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#pragma pack()
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#ifndef ntohll
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uint64_t ntohll(uint64_t x)
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{
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@ -99,6 +168,248 @@ bool rsGetHostByName(const std::string& hostname, in_addr& returned_addr)
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return ok;
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}
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bool rsGetHostByNameSpecDNS(const std::string& servername, const std::string& hostname, std::string& returned_addr)
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{
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#ifdef DEBUG_SPEC_DNS
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RsDbg()<<__PRETTY_FUNCTION__<<" servername="<< servername << " hostname=" << hostname << std::endl;
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#endif
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if (strlen(servername.c_str()) > 256)
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{
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RsErr()<<__PRETTY_FUNCTION__<<": servername is too long > 256 chars:"<<servername<<std::endl;
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return false;
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}
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if (strlen(hostname.c_str()) > 256)
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{
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RsErr()<<__PRETTY_FUNCTION__<<": hostname is too long > 256 chars:"<<hostname<<std::endl;
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return false;
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}
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bool isIPV4 = false;
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in_addr dns_server_4; in6_addr dns_server_6;
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if (inet_pton(AF_INET, servername.c_str(), &dns_server_4))
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isIPV4 = true;
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else if (inet_pton(AF_INET6, servername.c_str(), &dns_server_6))
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isIPV4 = false;
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else if (rsGetHostByName(servername, dns_server_4))
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isIPV4 = true;
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else
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{
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RsErr()<<__PRETTY_FUNCTION__<<": servername is on an unknow format: "<<servername<<std::endl;
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return false;
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}
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unsigned char buf[65536];
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struct sockaddr_in dest4;struct sockaddr_in6 dest6;
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if (isIPV4)
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{
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dest4.sin_family = AF_INET;
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dest4.sin_port = htons(53);
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dest4.sin_addr.s_addr = dns_server_4.s_addr;
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} else {
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dest6.sin6_family = AF_INET6;
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dest6.sin6_port = htons(53);
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dest6.sin6_flowinfo = 0;
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dest6.sin6_addr = dns_server_6;
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dest6.sin6_scope_id = 0;
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}
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//Set the DNS structure to standard queries
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struct DNS_HEADER* dns = (struct DNS_HEADER *)&buf;
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dns->id = static_cast<unsigned short>(htons(getpid())); //Transaction Id
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//dns flags = 0x0100 Standard Query
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dns->qr = 0; //Query/Response: Message is a query
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dns->opcode = 0; //OpCode: Standard query
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dns->aa = 0; //Authoritative: Server is not an authority for domain
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dns->tc = 0; //TrunCated: Message is not truncated
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dns->rd = 1; //Recursion Desired: Do query recursively
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dns->ra = 0; //Recursion Available: Server cannot do recursive queries
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dns->z = 0; //Z: reserved
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dns->ad = 0; //Authentic Data: Answer/authority portion was not authenticated by the server
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dns->cd = 0; //Checking Disabled: Unacceptable
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dns->rcode = 0; //Response Code: No error
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dns->q_count = htons(1); //1 Question
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dns->ans_count = 0; //0 Answer
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dns->auth_count = 0; //0 Authority RRs
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dns->add_count = 0; //0 Additional RRs
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size_t curSendSize = sizeof(struct DNS_HEADER);
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//Point to the query server name portion
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unsigned char* qname =static_cast<unsigned char*>(&buf[curSendSize]);
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//First byte is Label Type: https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-10
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qname[0] = 0x04; //One Label with Normal label lower 6 bits is the length of the label
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memcpy(&qname[1],hostname.c_str(),strlen(hostname.c_str()));
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size_t qnameSize = strlen((const char*)qname);
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// Format Hostname like www.google.com to 3www6google3com
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{
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size_t last = qnameSize;
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for(size_t i = qnameSize-1 ; i > 0 ; i--)
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if(qname[i]=='.')
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{
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qname[i]=last-i-1;
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last = i;
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}
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}
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curSendSize += qnameSize +1; //With \0 terminator
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//Point to the query constant portion
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struct QUESTION* qinfo =(struct QUESTION*)&buf[curSendSize];
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qinfo->qtype = htons(isIPV4 ? DNST_A : DNST_AAAA); //Type: A / AAAA(Host Address)
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qinfo->qclass = htons(DNSC_IN); //Class: IN
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curSendSize += sizeof(struct QUESTION);
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#ifdef DEBUG_SPEC_DNS
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RsDbg()<<__PRETTY_FUNCTION__<< " Sending Packet: " << std::endl << hexDump(buf, curSendSize) << std::endl;
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#endif
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int s = isIPV4 ? socket(AF_INET , SOCK_DGRAM , IPPROTO_UDP)
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: socket(AF_INET6 , SOCK_DGRAM , IPPROTO_UDP) ; //UDP packet for DNS queries
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ssize_t send_size = sendto(s, (char*)buf, curSendSize, 0
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,isIPV4 ? (struct sockaddr*)&dest4
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: (struct sockaddr*)&dest6
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,isIPV4 ? sizeof(dest4)
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: sizeof(dest6)
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);
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if( send_size < 0)
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{
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RsErr()<<__PRETTY_FUNCTION__<<": Send Failed with size = " << send_size << std::endl;
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return false;
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}
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#ifdef DEBUG_SPEC_DNS
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RsDbg()<<__PRETTY_FUNCTION__<< " Waiting answer..." << std::endl;
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#endif
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//****************************************************************************************//
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//--- Receive the answer ---//
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//****************************************************************************************//
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socklen_t dest_size = static_cast<socklen_t>(sizeof dest4);
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ssize_t rec_size=recvfrom(s,(char*)buf , 65536 , 0 , (struct sockaddr*)&dest4 , &dest_size );
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if(rec_size <= 0)
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{
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RsErr()<<__PRETTY_FUNCTION__<<": Receive Failed"<<std::endl;
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return false;
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}
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#ifdef DEBUG_SPEC_DNS
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RsDbg()<<__PRETTY_FUNCTION__<< " Received: " << hexDump(buf, rec_size) << std::endl;
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#endif
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if (rec_size< static_cast<ssize_t>(sizeof(struct DNS_HEADER)) )
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{
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RsErr()<<__PRETTY_FUNCTION__<<": Request received too small to get DNSHeader."<<std::endl;
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return false;
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}
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#ifdef DEBUG_SPEC_DNS
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//Point to the header portion
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dns = (struct DNS_HEADER*) buf;
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RsDbg()<<__PRETTY_FUNCTION__<<" The response contains : " << std::endl
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<<ntohs(dns->q_count) << " Questions." << std::endl
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<<ntohs(dns->ans_count) << " Answers." << std::endl
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<<ntohs(dns->auth_count) << " Authoritative Servers." << std::endl
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<<ntohs(dns->add_count) << " Additional records." << std::endl;
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#endif
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size_t curRecSize = sizeof(struct DNS_HEADER);
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if (rec_size< static_cast<ssize_t>(curRecSize + 1 + sizeof(struct QUESTION)) )
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{
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RsErr()<<__PRETTY_FUNCTION__<<": Request received too small to get Question return."<<std::endl;
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return false;
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}
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//Point to the query portion
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unsigned char* qnameRecv =static_cast<unsigned char*>(&buf[curRecSize]);
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if (memcmp(qname,qnameRecv,qnameSize + 1 + sizeof(struct QUESTION)) )
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{
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RsErr()<<__PRETTY_FUNCTION__<<": Request received different from that sent."<<std::endl;
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return false;
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}
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curRecSize += qnameSize + 1 + sizeof(struct QUESTION);
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if (rec_size< static_cast<ssize_t>(curRecSize + 2) )
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{
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RsErr()<<__PRETTY_FUNCTION__<<": Request received too small to get Answer return."<<std::endl;
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return false;
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}
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//Point to the Answer portion
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unsigned char* reader = &buf[curRecSize];
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size_t rLabelSize=0;
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if((reader[0]&0xC0) == 0)
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{
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//Normal label lower 6 bits is the length of the label
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rLabelSize=(reader[0]&~(0xC0)*256) + reader[1];
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}
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else if ((reader[0]&0xC0) == 0xC0)
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{
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//Compressed label the lower 6 bits and the 8 bits from next octet form a pointer to the compression target.
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//Don't need to read it, maybe the same as in Query
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rLabelSize=0;
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}
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else
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{
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RsErr()<<__PRETTY_FUNCTION__<<": Answer received with unmanaged label format."<<std::endl;
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return false;
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}
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curRecSize += 2 + rLabelSize;
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if (rec_size< static_cast<ssize_t>(curRecSize + sizeof(struct RR_DATA)) )
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{
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RsErr()<<__PRETTY_FUNCTION__<<": Request received too small to get Data return."<<std::endl;
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return false;
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}
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//Point to the query portion
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struct RR_DATA* rec_data = (struct RR_DATA *)&buf[curRecSize];
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if (rec_data->rtype!=qinfo->qtype)
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{
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RsErr()<<__PRETTY_FUNCTION__<<": Answer's type received different from query sent."<<std::endl;
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return false;
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}
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if (rec_data->rclass!=qinfo->qclass)
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{
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RsErr()<<__PRETTY_FUNCTION__<<": Answer's class received different from query sent."<<std::endl;
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return false;
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}
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curRecSize += sizeof(struct RR_DATA);
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if (rec_size< static_cast<ssize_t>(curRecSize + ntohs(rec_data->data_len)) )
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{
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RsErr()<<__PRETTY_FUNCTION__<<": Request received too small to get Full Data return."<<std::endl;
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return false;
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}
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//Retrieve Address
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if(ntohs(rec_data->data_len)==4)
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{
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if (isIPV4)
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{
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in_addr ipv4Add;
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ipv4Add.s_addr=*(in_addr_t*)&buf[curRecSize];
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#ifdef DEBUG_SPEC_DNS
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RsDbg()<<__PRETTY_FUNCTION__<< " Retrieve address: " << rs_inet_ntoa(ipv4Add) << std::endl;
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#endif
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returned_addr = rs_inet_ntoa(ipv4Add);
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return true;
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}
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}
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else if(ntohs(rec_data->data_len)==16)
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{
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if (!isIPV4)
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{
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in6_addr ipv6Add;
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ipv6Add =*(in6_addr*)&buf[curRecSize];
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#ifdef DEBUG_SPEC_DNS
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RsDbg()<<__PRETTY_FUNCTION__<< " Retrieve address: " << rs_inet_ntoa(ipv6Add) << std::endl;
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#endif
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returned_addr = rs_inet_ntoa(ipv6Add);
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return true;
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}
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}
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RsErr()<<__PRETTY_FUNCTION__<< " Retrieve unmanaged data size=" << ntohs(rec_data->data_len) << std::endl;
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return false;
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}
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bool isValidNet(const struct in_addr *addr)
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{
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// invalid address.
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@ -174,3 +485,18 @@ std::string rs_inet_ntoa(struct in_addr in)
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rs_sprintf(str, "%u.%u.%u.%u", (int) bytes[0], (int) bytes[1], (int) bytes[2], (int) bytes[3]);
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return str;
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}
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std::string rs_inet_ntoa(const in6_addr& in)
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{
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std::string str;
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rs_sprintf(str, "%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x",
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(int)in.s6_addr[0] , (int)in.s6_addr[1],
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(int)in.s6_addr[2] , (int)in.s6_addr[3],
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(int)in.s6_addr[4] , (int)in.s6_addr[5],
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(int)in.s6_addr[6] , (int)in.s6_addr[7],
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(int)in.s6_addr[8] , (int)in.s6_addr[9],
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(int)in.s6_addr[10], (int)in.s6_addr[11],
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(int)in.s6_addr[12], (int)in.s6_addr[13],
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(int)in.s6_addr[14], (int)in.s6_addr[15]);
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return str;
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}
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