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/*
* This file is part of PowerDNS or dnsdist.
* Copyright -- PowerDNS.COM B.V. and its contributors
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of version 2 of the GNU General Public License as
* published by the Free Software Foundation.
*
* In addition, for the avoidance of any doubt, permission is granted to
* link this program with OpenSSL and to (re)distribute the binaries
* produced as the result of such linking.
*
* 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 for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "dns.hh"
#include "ednsoptions.hh"
#include "iputils.hh"
bool getNextEDNSOption(const char* data, size_t dataLen, uint16_t& optionCode, uint16_t& optionLen)
{
if (data == nullptr || dataLen < (sizeof(uint16_t) + sizeof(uint16_t))) {
return false;
}
size_t pos = 0;
const uint8_t* p = reinterpret_cast<const uint8_t*>(data);
optionCode = (static_cast<uint16_t>(p[pos]) * 256) + p[pos + 1];
pos += EDNS_OPTION_CODE_SIZE;
optionLen = (static_cast<uint16_t>(p[pos]) * 256) + p[pos + 1];
pos += EDNS_OPTION_LENGTH_SIZE;
(void) pos;
return true;
}
/* extract the position (relative to the optRR pointer!) and size of a specific EDNS0 option from a pointer on the beginning rdLen of the OPT RR */
int getEDNSOption(const char* optRR, const size_t len, uint16_t wantedOption, size_t* optionValuePosition, size_t * optionValueSize)
{
assert(optRR != nullptr);
assert(optionValuePosition != nullptr);
assert(optionValueSize != nullptr);
size_t pos = 0;
if (len < DNS_RDLENGTH_SIZE)
return EINVAL;
const uint16_t rdLen = (((unsigned char) optRR[pos]) * 256) + ((unsigned char) optRR[pos+1]);
size_t rdPos = 0;
pos += DNS_RDLENGTH_SIZE;
if ((pos + rdLen) > len) {
return EINVAL;
}
while(len >= (pos + EDNS_OPTION_CODE_SIZE + EDNS_OPTION_LENGTH_SIZE) &&
rdLen >= (rdPos + EDNS_OPTION_CODE_SIZE + EDNS_OPTION_LENGTH_SIZE)) {
uint16_t optionCode;
uint16_t optionLen;
if (!getNextEDNSOption(optRR + pos, len-pos, optionCode, optionLen)) {
break;
}
pos += EDNS_OPTION_CODE_SIZE;
rdPos += EDNS_OPTION_CODE_SIZE;
pos += EDNS_OPTION_LENGTH_SIZE;
rdPos += EDNS_OPTION_LENGTH_SIZE;
if (optionLen > (rdLen - rdPos) || optionLen > (len - pos)) {
return EINVAL;
}
if (optionCode == wantedOption) {
*optionValuePosition = pos - (EDNS_OPTION_CODE_SIZE + EDNS_OPTION_LENGTH_SIZE);
*optionValueSize = optionLen + EDNS_OPTION_CODE_SIZE + EDNS_OPTION_LENGTH_SIZE;
return 0;
}
else {
/* skip this option */
pos += optionLen;
rdPos += optionLen;
}
}
return ENOENT;
}
/* extract all EDNS0 options from a pointer on the beginning rdLen of the OPT RR */
int getEDNSOptions(const char* optRR, const size_t len, EDNSOptionViewMap& options)
{
assert(optRR != nullptr);
size_t pos = 0;
if (len < DNS_RDLENGTH_SIZE)
return EINVAL;
const uint16_t rdLen = (((unsigned char) optRR[pos]) * 256) + ((unsigned char) optRR[pos+1]);
size_t rdPos = 0;
pos += DNS_RDLENGTH_SIZE;
if ((pos + rdLen) > len) {
return EINVAL;
}
while(len >= (pos + EDNS_OPTION_CODE_SIZE + EDNS_OPTION_LENGTH_SIZE) &&
rdLen >= (rdPos + EDNS_OPTION_CODE_SIZE + EDNS_OPTION_LENGTH_SIZE)) {
const uint16_t optionCode = (((unsigned char) optRR[pos]) * 256) + ((unsigned char) optRR[pos+1]);
pos += EDNS_OPTION_CODE_SIZE;
rdPos += EDNS_OPTION_CODE_SIZE;
const uint16_t optionLen = (((unsigned char) optRR[pos]) * 256) + ((unsigned char) optRR[pos+1]);
pos += EDNS_OPTION_LENGTH_SIZE;
rdPos += EDNS_OPTION_LENGTH_SIZE;
if (optionLen > (rdLen - rdPos) || optionLen > (len - pos))
return EINVAL;
EDNSOptionViewValue value;
value.content = optRR + pos;
value.size = optionLen;
options[optionCode].values.push_back(value);
/* skip this option */
pos += optionLen;
rdPos += optionLen;
}
return 0;
}
bool getEDNSOptionsFromContent(const std::string& content, std::vector<std::pair<uint16_t, std::string>>& options)
{
size_t pos = 0;
uint16_t code, len;
const size_t contentLength = content.size();
while (pos < contentLength && (contentLength - pos) >= (EDNS_OPTION_CODE_SIZE + EDNS_OPTION_LENGTH_SIZE)) {
code = (static_cast<unsigned char>(content.at(pos)) * 256) + static_cast<unsigned char>(content.at(pos+1));
pos += EDNS_OPTION_CODE_SIZE;
len = (static_cast<unsigned char>(content.at(pos)) * 256) + static_cast<unsigned char>(content.at(pos+1));
pos += EDNS_OPTION_LENGTH_SIZE;
if (pos > contentLength || len > (contentLength - pos)) {
return false;
}
options.emplace_back(code, std::string(&content.at(pos), len));
pos += len;
}
return true;
}
void generateEDNSOption(uint16_t optionCode, const std::string& payload, std::string& res)
{
const uint16_t ednsOptionCode = htons(optionCode);
const uint16_t payloadLen = htons(payload.length());
res.append((const char *) &ednsOptionCode, sizeof ednsOptionCode);
res.append((const char *) &payloadLen, sizeof payloadLen);
res.append(payload);
}
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