lokinet/llarp/dns.cpp
2019-02-03 00:48:10 +00:00

642 lines
19 KiB
C++

#include <dnsd.hpp> // for llarp_handle_dnsd_recvfrom, dnsc
#include <util/buffer.hpp>
#include <util/endian.hpp>
#include <util/logger.hpp>
void
hexDump(const char *buffer, uint16_t size)
{
// would rather heap allocate than use VLA
char *hex_buffer = new char[size * 3 + 1];
hex_buffer[size * 3] = 0;
for(unsigned int j = 0; j < size; j++)
sprintf(&hex_buffer[3 * j], "%02X ", buffer[j]);
std::string str(hex_buffer);
llarp::LogInfo("First ", size, " bytes: ", str);
delete[] hex_buffer;
}
void
hexDumpAt(const char *const buffer, uint32_t pos, uint16_t size)
{
// would rather heap allocate than use VLA
char *hex_buffer = new char[size * 3 + 1];
hex_buffer[size * 3] = 0;
for(unsigned int j = 0; j < size; j++)
sprintf(&hex_buffer[3 * j], "%02X ", buffer[pos + j]);
std::string str(hex_buffer);
llarp::LogInfo(pos, " ", size, " bytes: ", str);
delete[] hex_buffer;
}
/*
<domain-name> is a domain name represented as a series of labels, and
terminated by a label with zero length. <character-string> is a single
length octet followed by that number of characters. <character-string>
is treated as binary information, and can be up to 256 characters in
length (including the length octet).
*/
std::string
getDNSstring(const char *const buffer, uint32_t *pos)
{
std::string str = "";
const char *moveable = buffer;
moveable += *pos;
uint8_t length = *moveable++;
(*pos)++;
if(length == 0xc0)
{
uint8_t cPos = *moveable++;
(*pos)++;
uint32_t cPos32 = cPos;
// llarp::LogInfo("Found reference at ", std::to_string(cPos));
return getDNSstring(buffer, &cPos32);
}
// hexDump(moveable, length);
// hexDump(buffer, length);
// printf("dnsStringLen[%d]\n", length);
// llarp::LogInfo("dnsStringLen ", std::to_string(length));
if(!length)
return str;
while(length != 0)
{
// llarp::LogInfo("Reading ", std::to_string(length));
for(int i = 0; i < length; i++)
{
char c = *moveable++;
(*pos)++;
str.append(1, c);
}
if(*moveable == '\xc0')
{
moveable++;
(*pos)++; // forward one char
uint8_t cPos = *moveable; // read char
uint32_t cPos32 = cPos;
// llarp::LogInfo("Remaining [", str, "] is an reference at ", (int)cPos);
std::string addl = getDNSstring(buffer, &cPos32);
// llarp::LogInfo("Addl str [", addl, "]");
str += "." + addl;
// llarp::LogInfo("Final str [", str, "]");
(*pos)++; // move past reference
return str;
}
length = *moveable++;
(*pos)++;
if(length > 64)
llarp::LogError("bug detected");
// else
// hexDump(buffer, length);
// llarp::LogInfo("NextLen ", std::to_string(length));
if(length != 0)
str.append(1, '.');
}
// llarp::LogInfo("Returning ", str);
return str;
}
void
code_domain(char *&buffer, const std::string &domain) throw()
{
std::string::size_type start(0);
std::string::size_type end; // indexes
// llarp::LogInfo("domain [", domain, "]");
while((end = domain.find('.', start)) != std::string::npos)
{
*buffer++ = end - start; // label length octet
for(std::string::size_type i = start; i < end; i++)
{
*buffer++ = domain[i]; // label octets
// llarp::LogInfo("Writing ", domain[i], " at ", i);
}
start = end + 1; // Skip '.'
}
// llarp::LogInfo("start ", start, " domain size ", domain.size());
*buffer++ = domain.size() - start; // last label length octet
for(size_t i = start; i < domain.size(); i++)
{
*buffer++ = domain[i]; // last label octets
// llarp::LogInfo("Writing ", domain[i], " at ", i);
}
*buffer++ = 0;
}
void
vcode_domain(std::vector< byte_t > &bytes, const std::string &domain) throw()
{
std::string::size_type start(0);
std::string::size_type end; // indexes
// llarp::LogInfo("domain [", domain, "]");
while((end = domain.find('.', start)) != std::string::npos)
{
bytes.push_back(end - start); // label length octet
for(std::string::size_type i = start; i < end; i++)
{
bytes.push_back(domain[i]); // label octets
// llarp::LogInfo("Writing ", domain[i], " at ", i);
}
start = end + 1; // Skip '.'
}
// llarp::LogInfo("start ", start, " domain size ", domain.size());
bytes.push_back(domain.size() - start); // last label length octet
for(size_t i = start; i < domain.size(); i++)
{
bytes.push_back(domain[i]); // last label octets
// llarp::LogInfo("Writing ", domain[i], " at ", i);
}
bytes.push_back(0); // end it
}
// expects host order
void
vput16bits(std::vector< byte_t > &bytes, uint16_t value) throw()
{
char buf[2] = {0};
char *write_buffer = buf;
htobe16buf(write_buffer, value);
bytes.push_back(buf[0]);
bytes.push_back(buf[1]);
}
// expects host order
void
vput32bits(std::vector< byte_t > &bytes, uint32_t value) throw()
{
char buf[4] = {0};
char *write_buffer = buf;
htobe32buf(write_buffer, value);
bytes.push_back(buf[0]);
bytes.push_back(buf[1]);
bytes.push_back(buf[2]);
bytes.push_back(buf[3]);
}
void
dns_writeType(std::vector< byte_t > &bytes, llarp::dns::record *record)
{
llarp::dns::type_1a *type1a = dynamic_cast< llarp::dns::type_1a * >(record);
if(type1a)
{
std::vector< byte_t > more_bytes = type1a->to_bytes();
llarp::LogDebug("[1]Adding ", more_bytes.size());
bytes.insert(bytes.end(), more_bytes.begin(), more_bytes.end());
}
llarp::dns::type_2ns *type2ns =
dynamic_cast< llarp::dns::type_2ns * >(record);
if(type2ns)
{
std::vector< byte_t > more_bytes = type2ns->to_bytes();
llarp::LogDebug("[2]Adding ", more_bytes.size());
bytes.insert(bytes.end(), more_bytes.begin(), more_bytes.end());
}
llarp::dns::type_5cname *type5cname =
dynamic_cast< llarp::dns::type_5cname * >(record);
if(type5cname)
{
std::vector< byte_t > more_bytes = type5cname->to_bytes();
llarp::LogDebug("[5]Adding ", more_bytes.size());
bytes.insert(bytes.end(), more_bytes.begin(), more_bytes.end());
}
llarp::dns::type_12ptr *type12ptr =
dynamic_cast< llarp::dns::type_12ptr * >(record);
if(type12ptr)
{
std::vector< byte_t > more_bytes = type12ptr->to_bytes();
llarp::LogDebug("[12]Adding ", more_bytes.size());
bytes.insert(bytes.end(), more_bytes.begin(), more_bytes.end());
}
llarp::dns::type_15mx *type15mx =
dynamic_cast< llarp::dns::type_15mx * >(record);
if(type15mx)
{
std::vector< byte_t > more_bytes = type15mx->to_bytes();
llarp::LogDebug("[15]Adding ", more_bytes.size());
bytes.insert(bytes.end(), more_bytes.begin(), more_bytes.end());
}
llarp::dns::type_16txt *type16txt =
dynamic_cast< llarp::dns::type_16txt * >(record);
if(type16txt)
{
std::vector< byte_t > more_bytes = type16txt->to_bytes();
llarp::LogDebug("[15]Adding ", more_bytes.size());
bytes.insert(bytes.end(), more_bytes.begin(), more_bytes.end());
}
}
std::vector< byte_t >
packet2bytes(dns_packet &in)
{
std::vector< byte_t > write_buffer;
vput16bits(write_buffer, in.header.id);
int fields = (in.header.qr << 15); // QR => message type, 1 = response
fields += (in.header.opcode << 14); // I think opcode is always 0
fields += in.header.rcode; // response code (3 => not found, 0 = Ok)
vput16bits(write_buffer, fields);
// don't pull these from the header, trust what we actually have more
vput16bits(write_buffer, in.questions.size()); // QD (number of questions)
vput16bits(write_buffer, in.answers.size()); // AN (number of answers)
vput16bits(write_buffer, in.auth_rrs.size()); // NS (number of auth RRs)
vput16bits(write_buffer,
in.additional_rrs.size()); // AR (number of Additional RRs)
for(auto &it : in.questions)
{
// code question
vcode_domain(write_buffer, it->name);
vput16bits(write_buffer, it->type);
vput16bits(write_buffer, it->qClass);
}
for(auto &it : in.answers)
{
// code answers
vcode_domain(write_buffer, it->name);
vput16bits(write_buffer, it->type);
vput16bits(write_buffer, it->aClass);
vput32bits(write_buffer, 1); // ttl
dns_writeType(write_buffer, it->record.get());
}
for(auto &it : in.auth_rrs)
{
// code answers
vcode_domain(write_buffer, it->name);
vput16bits(write_buffer, it->type);
vput16bits(write_buffer, it->aClass);
vput32bits(write_buffer, 1); // ttl
dns_writeType(write_buffer, it->record.get());
}
for(auto &it : in.additional_rrs)
{
// code answers
vcode_domain(write_buffer, it->name);
vput16bits(write_buffer, it->type);
vput16bits(write_buffer, it->aClass);
vput32bits(write_buffer, 1); // ttl
dns_writeType(write_buffer, it->record.get());
}
return write_buffer;
}
extern "C"
{
uint16_t
get16bits(const char *&buffer) throw()
{
uint16_t value = bufbe16toh(buffer);
buffer += 2;
return value;
}
uint32_t
get32bits(const char *&buffer) throw()
{
uint32_t value = bufbe32toh(buffer);
buffer += 4;
return value;
}
bool
decode_hdr(llarp_buffer_t *buffer, dns_msg_header *hdr)
{
uint16_t fields;
// reads as HOST byte order
if(!llarp_buffer_read_uint16(buffer, &hdr->id))
return false;
if(!llarp_buffer_read_uint16(buffer, &fields))
return false;
if(!llarp_buffer_read_uint16(buffer, &hdr->qdCount))
return false;
if(!llarp_buffer_read_uint16(buffer, &hdr->anCount))
return false;
if(!llarp_buffer_read_uint16(buffer, &hdr->nsCount))
return false;
if(!llarp_buffer_read_uint16(buffer, &hdr->arCount))
return false;
// decode fields into hdr
uint8_t lFields = (fields & 0x00FF) >> 0;
uint8_t hFields = (fields & 0xFF00) >> 8;
// process high byte
// hdr->qr = fields & 0x8000;
hdr->qr = (hFields >> 7) & 0x1;
hdr->opcode = fields & 0x7800;
hdr->aa = fields & 0x0400;
hdr->tc = fields & 0x0200;
hdr->rd = fields & 0x0100;
// process low byte
hdr->ra = (lFields >> 7) & 0x1;
hdr->z = (lFields >> 6) & 0x1;
hdr->ad = (lFields >> 5) & 0x1;
hdr->cd = (lFields >> 4) & 0x1;
hdr->rcode = lFields & 0xf;
return true;
}
dns_msg_question *
decode_question(const char *buffer, uint32_t *pos)
{
dns_msg_question *question = new dns_msg_question;
std::string m_qName = getDNSstring(buffer, pos);
llarp::LogDebug("Got question name: ", m_qName);
const char *moveable = buffer;
moveable += *pos; // advance to position
question->name = m_qName;
question->type = get16bits(moveable);
(*pos) += 2;
question->qClass = get16bits(moveable);
(*pos) += 2;
return question;
}
dns_msg_answer *
decode_answer(const char *const buffer, uint32_t *pos)
{
dns_msg_answer *answer = new dns_msg_answer;
/*
llarp_buffer_t bob;
bob.base = (unsigned char *)buffer;
bob.sz = 12;
llarp::DumpBuffer(bob);
*/
const char *moveable = buffer;
// llarp::LogDebug("Advancing to pos ", std::to_string(*pos));
moveable += (*pos); // advance to position
// hexDump(moveable, 12);
// hexDumpAt(buffer, *pos, 12);
if(*moveable == '\xc0')
{
// hexDump(moveable, 2);
moveable++;
(*pos)++;
uint8_t readAt = *moveable;
uint32_t readAt32 = readAt;
// llarp::LogInfo("Ref, skip. Read ", readAt32);
// hexDumpAt(buffer, readAt, 2);
answer->name = getDNSstring(buffer, &readAt32);
moveable++;
(*pos)++;
// hexDump(moveable, 10);
// hexDumpAt(buffer, *pos, 10);
}
else
{
// get DNSString?
llarp::LogWarn("Need to parse string, implement me");
/*
uint32_t readAt32 = *pos;
answer->name = getDNSstring(buffer, &readAt32);
llarp::LogInfo("Parsed string ", answer->name, " read ",
std::to_string(readAt32)); moveable += readAt32; (*pos) += readAt32;
*/
// moveable++; (*pos)++;
}
/*
hexDump(moveable, 10);
uint8_t first = *moveable++; (*pos)++;
llarp::LogInfo("decode - first", std::to_string(first));
// SOA hack
if(first != 12 && first != 14) // 0x0c (c0 0c) 0
{
llarp::LogDebug("decode - first isnt 12, stepping back");
moveable--; (*pos)--; // rewind buffer one byte
}
*/
// hexDump(moveable, 10);
answer->type = get16bits(moveable);
(*pos) += 2;
llarp::LogDebug("Answer Type: ", answer->type);
// assert(answer->type < 259);
if(answer->type > 259)
{
llarp::LogWarn("Answer type is off the charts");
}
answer->aClass = get16bits(moveable);
(*pos) += 2;
llarp::LogDebug("Answer Class: ", answer->aClass);
answer->ttl = get32bits(moveable);
(*pos) += 4;
llarp::LogDebug("Answer TTL: ", answer->ttl);
answer->rdLen = get16bits(moveable);
(*pos) += 2;
/*
llarp::LogDebug("Answer rdL: ", answer->rdLen, " at ",
std::to_string(*pos));
*/
// uint32_t cPos = moveable - buffer;
// llarp::LogInfo("pos at ", std::to_string(*pos), " calculated: ",
// std::to_string(cPos));
// hexDump(moveable, answer->rdLen);
// hexDumpAt(buffer, *pos, answer->rdLen);
if(answer->rdLen == 4)
{
answer->rData.resize(answer->rdLen);
memcpy(answer->rData.data(), moveable, answer->rdLen);
/*
llarp::LogDebug("Read ", std::to_string(answer->rData[0]), ".",
std::to_string(answer->rData[1]), ".",
std::to_string(answer->rData[2]), ".",
std::to_string(answer->rData[3]));
*/
moveable += answer->rdLen;
(*pos) += answer->rdLen; // advance the length
answer->record = std::make_unique< llarp::dns::type_1a >();
answer->record->parse(answer->rData);
}
else
{
llarp::LogDebug("Got type ", answer->type);
// FIXME: move this out of here, this shouldn't be responsible for decode
switch(answer->type)
{
case LLARP_DNS_RECTYPE_NS: // NS
{
std::string ns = getDNSstring(buffer, pos);
answer->rData.resize(ns.size());
memcpy(answer->rData.data(), ns.c_str(),
ns.size()); // raw copy rData
// don't really need to do anything here
moveable += answer->rdLen;
//(*pos) += answer->rdLen; // advance the length
answer->record = std::make_unique< llarp::dns::type_2ns >();
answer->record->parse(answer->rData);
}
break;
case LLARP_DNS_RECTYPE_CNAME: // CNAME
{
std::string cname = getDNSstring(buffer, pos);
llarp::LogDebug("CNAME ", cname);
answer->rData.resize(cname.size());
memcpy(answer->rData.data(), cname.c_str(), cname.size());
moveable += answer->rdLen;
//(*pos) += answer->rdLen; // advance the length
answer->record = std::make_unique< llarp::dns::type_5cname >();
answer->record->parse(answer->rData);
}
break;
case LLARP_DNS_RECTYPE_SOA: // type 6 = SOA
{
// 2 names, then 4x 32bit
// why risk any crashes
if(answer->rdLen < 24)
{
llarp::LogWarn("Weird SOA is less than 24 bytes: ", answer->rdLen);
}
/*
std::string mname = getDNSstring((char *)buffer);
std::string rname = getDNSstring((char *)buffer);
uint32_t serial = get32bits(buffer);
uint32_t refresh = get32bits(buffer);
uint32_t retry = get32bits(buffer);
uint32_t expire = get32bits(buffer);
uint32_t minimum = get32bits(buffer);
llarp::LogInfo("mname : ", mname);
llarp::LogInfo("rname : ", rname);
llarp::LogDebug("serial : ", serial);
llarp::LogDebug("refresh : ", refresh);
llarp::LogDebug("retry : ", retry);
llarp::LogDebug("expire : ", expire);
llarp::LogDebug("minimum : ", minimum);
*/
moveable += answer->rdLen;
(*pos) += answer->rdLen; // advance the length
}
break;
case LLARP_DNS_RECTYPE_PTR:
{
std::string revname = getDNSstring(buffer, pos);
llarp::LogInfo("revDNSname: ", revname);
// answer->rData = new uint8_t[answer->rdLen + 1];
answer->rData.resize(revname.size());
memcpy(answer->rData.data(), revname.c_str(), revname.size());
// answer->rData = (uint8_t *)strdup(revname.c_str()); // safer? nope
moveable += answer->rdLen;
//(*pos) += answer->rdLen; // advance the length
answer->record = std::make_unique< llarp::dns::type_12ptr >();
answer->record->parse(answer->rData);
}
break;
case LLARP_DNS_RECTYPE_MX:
{
uint16_t priority = get16bits(moveable);
(*pos) += 2;
std::string revname = getDNSstring(buffer, pos);
llarp::LogInfo("MX: ", revname, " @ ", priority);
// answer->rData = new uint8_t[revname.length() + 1];
// memcpy(answer->rData, revname.c_str(), answer->rdLen);
answer->rData.resize(revname.size());
memcpy(answer->rData.data(), revname.c_str(), revname.size());
moveable += answer->rdLen - 2; // advance the length
// llarp::LogInfo("leaving at ", std::to_string(*pos));
// hexDumpAt(buffer, *pos, 5);
// hexDump(moveable, 5);
answer->record = std::make_unique< llarp::dns::type_15mx >();
answer->record->parse(answer->rData);
}
break;
case LLARP_DNS_RECTYPE_TXT:
{
// hexDump(buffer, 5);
// std::string revname = getDNSstring((char *)buffer);
llarp::LogInfo("TXT: size: ", answer->rdLen);
answer->rData.resize(answer->rdLen);
memcpy(answer->rData.data(), moveable + 1, answer->rdLen);
moveable += answer->rdLen;
(*pos) += answer->rdLen; // advance the length
answer->record = std::make_unique< llarp::dns::type_16txt >();
answer->record->parse(answer->rData);
}
break;
// type 28 AAAA
default:
moveable += answer->rdLen;
(*pos) += answer->rdLen; // advance the length
llarp::LogWarn("Unknown Type ", answer->type);
break;
}
}
return answer;
}
void
put16bits(char *&buffer, uint16_t value) throw()
{
htobe16buf(buffer, value);
buffer += 2;
}
void
put32bits(char *&buffer, uint32_t value) throw()
{
htobe32buf(buffer, value);
buffer += 4;
}
void
llarp_handle_dns_recvfrom(struct llarp_udp_io *udp,
const struct sockaddr *addr, ManagedBuffer buf)
{
// auto buffer = llarp::StackBuffer< decltype(castBuf) >(castBuf);
dns_msg_header hdr;
if(!decode_hdr(&buf.underlying, &hdr))
{
llarp::LogError("failed to decode dns header");
return;
}
// rewind
buf.underlying.cur = buf.underlying.base;
llarp::LogDebug("msg id ", hdr.id);
llarp::LogDebug("msg qr ", (uint8_t)hdr.qr);
if(!udp)
{
llarp::LogError("no udp passed in to handler");
}
if(!addr)
{
llarp::LogError("no source addr passed in to handler");
}
if(hdr.qr)
{
llarp::LogDebug("handling as dnsc answer");
llarp_handle_dnsc_recvfrom(udp, addr, buf);
}
else
{
llarp::LogDebug("handling as dnsd question");
llarp_handle_dnsd_recvfrom(udp, addr, buf);
}
}
}