// Copyright (C) 2023 Internet Systems Consortium, Inc. ("ISC")
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#include <config.h>

#include <dhcp/option4_dnr.h>
#include <dns/labelsequence.h>
#include <util/strutil.h>

using namespace isc::asiolink;
using namespace isc::util;

namespace isc {
namespace dhcp {

Option4Dnr::Option4Dnr(OptionBufferConstIter begin, OptionBufferConstIter end)
    : Option(V4, DHO_V4_DNR) {
    unpack(begin, end);
}

OptionPtr
Option4Dnr::clone() const {
    return (cloneInternal<Option4Dnr>());
}

void
Option4Dnr::pack(OutputBuffer& buf, bool check) const {
    packHeader(buf, check);
    for (const DnrInstance& dnr_instance : dnr_instances_) {
        buf.writeUint16(dnr_instance.getDnrInstanceDataLength());
        buf.writeUint16(dnr_instance.getServicePriority());
        buf.writeUint8(dnr_instance.getAdnLength());
        dnr_instance.packAdn(buf);
        if (dnr_instance.isAdnOnlyMode()) {
            continue;
        }

        buf.writeUint8(dnr_instance.getAddrLength());
        dnr_instance.packAddresses(buf);
        dnr_instance.packSvcParams(buf);
    }
}

void
Option4Dnr::unpack(OptionBufferConstIter begin, OptionBufferConstIter end) {
    setData(begin, end);
    while (begin != end) {
        DnrInstance dnr_instance(V4);
        if (std::distance(begin, end) < dnr_instance.getMinimalLength()) {
            isc_throw(OutOfRange, dnr_instance.getLogPrefix()
                                      << "DNR instance data truncated to size "
                                      << std::distance(begin, end));
        }

        // Unpack DnrInstanceDataLength.
        dnr_instance.unpackDnrInstanceDataLength(begin, end);

        const OptionBufferConstIter dnr_instance_end = begin +
                                                       dnr_instance.getDnrInstanceDataLength();

        // Unpack Service priority.
        dnr_instance.unpackServicePriority(begin);

        // Unpack ADN len + ADN.
        dnr_instance.unpackAdn(begin, dnr_instance_end);

        if (begin == dnr_instance_end) {
            // ADN only mode, other fields are not included.
            addDnrInstance(dnr_instance);
            continue;
        }

        dnr_instance.setAdnOnlyMode(false);

        // Unpack Addr Len + IPv4 Address(es).
        dnr_instance.unpackAddresses(begin, dnr_instance_end);

        // SvcParams (variable length) field is last.
        dnr_instance.unpackSvcParams(begin, dnr_instance_end);

        addDnrInstance(dnr_instance);
    }
}

std::string
Option4Dnr::toText(int indent) const {
    std::ostringstream stream;
    std::string in(indent, ' ');  // base indentation
    stream << in << "type=" << type_ << "(V4_DNR), "
           << "len=" << (len() - getHeaderLen());
    int i = 0;
    for (const DnrInstance& dnr_instance : dnr_instances_) {
        stream << ", DNR Instance " << ++i
               << "(Instance len=" << dnr_instance.getDnrInstanceDataLength() << ", "
               << dnr_instance.getDnrInstanceAsText() << ")";
    }

    return (stream.str());
}

uint16_t
Option4Dnr::len() const {
    uint16_t len = OPTION4_HDR_LEN;
    for (const DnrInstance& dnr_instance : dnr_instances_) {
        len += dnr_instance.getDnrInstanceDataLength() +
               dnr_instance.getDnrInstanceDataLengthSize();
    }

    return (len);
}

void
Option4Dnr::addDnrInstance(DnrInstance& dnr_instance) {
    dnr_instances_.push_back(dnr_instance);
}

const std::unordered_set<std::string> DnrInstance::FORBIDDEN_SVC_PARAMS = {"ipv4hint", "ipv6hint"};

DnrInstance::DnrInstance(Option::Universe universe)
    : universe_(universe), dnr_instance_data_length_(0), service_priority_(0),
      adn_length_(0), addr_length_(0), svc_params_length_(0),
      adn_only_mode_(true), dnr_instance_data_length_size_(0),
      adn_length_size_(0), addr_length_size_(0), minimal_length_(0) {
    initMembers();
}

DnrInstance::DnrInstance(Option::Universe universe,
                         const uint16_t service_priority,
                         const std::string& adn,
                         const DnrInstance::AddressContainer& ip_addresses,
                         const std::string& svc_params)
    : universe_(universe), dnr_instance_data_length_(0),
      service_priority_(service_priority), adn_length_(0),
      addr_length_(0), ip_addresses_(ip_addresses), svc_params_length_(0),
      adn_only_mode_(true), svc_params_(svc_params),
      dnr_instance_data_length_size_(0), adn_length_size_(0),
      addr_length_size_(0), minimal_length_(0) {
    initMembers();
    setAdn(adn);
    checkFields();
}

DnrInstance::DnrInstance(Option::Universe universe,
                         const uint16_t service_priority,
                         const std::string& adn)
    : universe_(universe), dnr_instance_data_length_(0),
      service_priority_(service_priority), adn_length_(0),
      addr_length_(0), svc_params_length_(0), adn_only_mode_(true),
      dnr_instance_data_length_size_(0), adn_length_size_(0),
      addr_length_size_(0), minimal_length_(0) {
    initMembers();
    setAdn(adn);
}

void
DnrInstance::packAdn(OutputBuffer& buf) const {
    if (!adn_) {
        // This should not happen since Encrypted DNS options are designed
        // to always include an authentication domain name.
        isc_throw(InvalidOptionDnrDomainName, getLogPrefix()
                                                  << "Mandatory Authentication Domain Name fully "
                                                     "qualified domain-name is missing");
    }

    isc::dns::LabelSequence label_sequence(*adn_);
    if (label_sequence.getDataLength() > 0) {
        size_t data_length = 0;
        const uint8_t* data = label_sequence.getData(&data_length);
        buf.writeData(data, data_length);
    }
}

void
DnrInstance::packAddresses(OutputBuffer& buf) const {
    AddressContainer::const_iterator address = ip_addresses_.begin();
    while (address != ip_addresses_.end()) {
        buf.writeUint32(address->toUint32());
        ++address;
    }
}

void
DnrInstance::packSvcParams(OutputBuffer& buf) const {
    if (svc_params_length_ > 0) {
        buf.writeData(&(*svc_params_.begin()), svc_params_length_);
    }
}

std::string
DnrInstance::getAdnAsText() const {
    return (adn_) ? (adn_->toText()) : ("");
}

void
DnrInstance::setAdn(const std::string& adn) {
    std::string trimmed_adn = str::trim(adn);
    if (trimmed_adn.empty()) {
        isc_throw(InvalidOptionDnrDomainName, getLogPrefix()
                                                  << "Mandatory Authentication Domain Name fully "
                                                     "qualified domain-name must not be empty");
    }

    try {
        adn_.reset(new isc::dns::Name(trimmed_adn, true));
    } catch (const Exception& ex) {
        isc_throw(InvalidOptionDnrDomainName, getLogPrefix()
                                                  << "Failed to parse "
                                                     "fully qualified domain-name from string - "
                                                  << ex.what());
    }

    size_t adn_len = 0;
    isc::dns::LabelSequence label_sequence(*adn_);
    label_sequence.getData(&adn_len);
    if (adn_len > std::numeric_limits<uint16_t>::max()) {
        isc_throw(InvalidOptionDnrDomainName, getLogPrefix() << "Given ADN FQDN length " << adn_len
                                                             << " is bigger than uint_16 MAX");
    }

    adn_length_ = adn_len;
    if (universe_ == Option::V4) {
        dnr_instance_data_length_ = dnrInstanceLen();
    }
}

void
DnrInstance::unpackAdn(OptionBufferConstIter& begin, OptionBufferConstIter end) {
    OpaqueDataTuple::LengthFieldType lft = OptionDataTypeUtil::getTupleLenFieldType(universe_);
    OpaqueDataTuple adn_tuple(lft);
    try {
        adn_tuple.unpack(begin, end);
    } catch (const Exception& ex) {
        isc_throw(BadValue, getLogPrefix() << "failed to unpack ADN data"
                                           << " - " << ex.what());
    }

    adn_length_ = adn_tuple.getLength();

    // Encrypted DNS options are designed to always include an authentication domain name,
    // so when there is no FQDN included, we shall throw an exception.
    if (adn_length_ == 0) {
        isc_throw(InvalidOptionDnrDomainName, getLogPrefix()
                                                  << "Mandatory Authentication Domain Name fully "
                                                     "qualified domain-name is missing");
    }

    InputBuffer name_buf(adn_tuple.getData().data(), adn_length_);
    try {
        adn_.reset(new isc::dns::Name(name_buf, true));
    } catch (const Exception& ex) {
        isc_throw(InvalidOptionDnrDomainName, getLogPrefix()
                                                  << "Failed to parse "
                                                     "fully qualified domain-name from wire format "
                                                     "- " << ex.what());
    }

    begin += adn_length_ + getAdnLengthSize();
}

void
DnrInstance::checkSvcParams(bool from_wire_data) {
    std::string svc_params = str::trim(svc_params_);
    if (svc_params.empty()) {
        isc_throw(InvalidOptionDnrSvcParams, getLogPrefix()
                                                 << "Provided Svc Params field is empty");
    }

    if (!from_wire_data) {
        // If Service Params field was not parsed from on-wire data,
        // but actually was provided with ctor, let's calculate svc_params_length_.
        auto svc_params_len = svc_params.length();
        if (svc_params_len > std::numeric_limits<uint16_t>::max()) {
            isc_throw(InvalidOptionDnrSvcParams, getLogPrefix()
                                                     << "Given Svc Params length " << svc_params_len
                                                     << " is bigger than uint_16 MAX");
        }

        svc_params_length_ = svc_params_len;
        // If Service Params field was not parsed from on-wire data,
        // but actually was provided with ctor, let's replace it with trimmed value.
        svc_params_ = svc_params;
    }

    // SvcParams are a whitespace-separated list, with each SvcParam
    // consisting of a SvcParamKey=SvcParamValue pair or a standalone SvcParamKey.
    // SvcParams in presentation format MAY appear in any order, but keys MUST NOT be repeated.

    // Let's put all elements of a whitespace-separated list into a vector.
    std::vector<std::string> tokens = str::tokens(svc_params, " ");

    // Set of keys used to check if a key is not repeated.
    std::unordered_set<std::string> keys;
    // String sanitizer is used to check keys syntax.
    str::StringSanitizerPtr sanitizer;
    // SvcParamKeys are lower-case alphanumeric strings. Key names
    // contain 1-63 characters from the ranges "a"-"z", "0"-"9", and "-".
    std::string regex = "[^a-z0-9-]";
    sanitizer.reset(new str::StringSanitizer(regex, ""));

    // Now let's check each SvcParamKey=SvcParamValue pair.
    for (const std::string& token : tokens) {
        std::vector<std::string> key_val = str::tokens(token, "=");
        if (key_val.size() > 2) {
            isc_throw(InvalidOptionDnrSvcParams,
                      getLogPrefix() << "Wrong Svc Params syntax - more than one "
                                        "equals sign found in SvcParamKey=SvcParamValue pair");
        }

        // SvcParam Key related checks come below.
        std::string key = key_val[0];
        if (key.length() > 63) {
            isc_throw(InvalidOptionDnrSvcParams,
                      getLogPrefix() << "Wrong Svc Params syntax - key had more than 63 "
                                        "characters - " << key);
        }

        if (FORBIDDEN_SVC_PARAMS.find(key) != FORBIDDEN_SVC_PARAMS.end()) {
            isc_throw(InvalidOptionDnrSvcParams, getLogPrefix() << "Wrong Svc Params syntax - key "
                                                                << key << " must not be used");
        }

        auto insert_res = keys.insert(key);
        if (!insert_res.second) {
            isc_throw(InvalidOptionDnrSvcParams, getLogPrefix() << "Wrong Svc Params syntax - key "
                                                                << key << " was duplicated");
        }

        std::string sanitized_key = sanitizer->scrub(key);
        if (sanitized_key.size() < key.size()) {
            isc_throw(InvalidOptionDnrSvcParams,
                      getLogPrefix()
                          << "Wrong Svc Params syntax - invalid character used in key - " << key);
        }
    }
}

void
DnrInstance::checkFields() {
    if (svc_params_.empty() && ip_addresses_.empty()) {
        // ADN only mode, nothing more to do.
        return;
    }

    if (!svc_params_.empty() && ip_addresses_.empty()) {
        // As per draft-ietf-add-dnr 3.1.8:
        // If additional data is supplied (i.e. not ADN only mode),
        // the option includes at least one valid IP address.
        isc_throw(OutOfRange, getLogPrefix() << "No IP address given. Since this is not ADN only "
                                                "mode, at least one valid IP address must "
                                                "be included");
    }

    if (!svc_params_.empty()) {
        checkSvcParams(false);
    }

    adn_only_mode_ = false;
    const uint8_t addr_field_len = (universe_ == Option::V4) ? V4ADDRESS_LEN : V6ADDRESS_LEN;
    const uint16_t max_addr_len = (universe_ == Option::V4) ? std::numeric_limits<uint8_t>::max() :
                                                              std::numeric_limits<uint16_t>::max();
    auto addr_len = ip_addresses_.size() * addr_field_len;
    if (addr_len > max_addr_len) {
        isc_throw(OutOfRange, getLogPrefix() << "Given IP addresses length " << addr_len
                                             << " is bigger than MAX " << max_addr_len);
    }

    addr_length_ = addr_len;
    if (universe_ == Option::V4) {
        dnr_instance_data_length_ = dnrInstanceLen();
    }
}

std::string
DnrInstance::getDnrInstanceAsText() const {
    std::ostringstream stream;
    stream << "service_priority=" << service_priority_ << ", adn_length=" << adn_length_ << ", "
           << "adn='" << getAdnAsText() << "'";
    if (!adn_only_mode_) {
        stream << ", addr_length=" << addr_length_ << ", address(es):";
        for (const auto& address : ip_addresses_) {
            stream << " " << address.toText();
        }

        if (svc_params_length_ > 0) {
            stream << ", svc_params='" + svc_params_ + "'";
        }
    }

    return (stream.str());
}

uint16_t
DnrInstance::dnrInstanceLen() const {
    uint16_t len = SERVICE_PRIORITY_SIZE + adn_length_ + getAdnLengthSize();
    if (!adn_only_mode_) {
        len += addr_length_ + getAddrLengthSize() + svc_params_length_;
    }

    return (len);
}

void
DnrInstance::addIpAddress(const IOAddress& ip_address) {
    ip_addresses_.push_back(ip_address);
}

void
DnrInstance::unpackDnrInstanceDataLength(OptionBufferConstIter& begin, OptionBufferConstIter end) {
    dnr_instance_data_length_ = readUint16(&*begin, getDnrInstanceDataLengthSize());
    begin += getDnrInstanceDataLengthSize();
    if (std::distance(begin, end) < dnr_instance_data_length_) {
        isc_throw(OutOfRange, getLogPrefix()
                                  << "DNR instance data truncated to size "
                                  << std::distance(begin, end) << " but it was supposed to be "
                                  << dnr_instance_data_length_);
    }
}

void
DnrInstance::unpackServicePriority(OptionBufferConstIter& begin) {
    service_priority_ = readUint16(&*begin, SERVICE_PRIORITY_SIZE);
    begin += SERVICE_PRIORITY_SIZE;
}

void
DnrInstance::unpackAddresses(OptionBufferConstIter& begin, const OptionBufferConstIter end) {
    OpaqueDataTuple addr_tuple(OpaqueDataTuple::LENGTH_1_BYTE);
    try {
        addr_tuple.unpack(begin, end);
    } catch (const Exception& ex) {
        isc_throw(BadValue, getLogPrefix() << "failed to unpack IP Addresses data"
                                           << " - " << ex.what());
    }

    addr_length_ = addr_tuple.getLength();
    // It MUST be a multiple of 4.
    if ((addr_length_ % V4ADDRESS_LEN) != 0) {
        isc_throw(OutOfRange, getLogPrefix()
                                  << "Addr Len=" << addr_length_ << " is not divisible by 4");
    }

    // As per draft-ietf-add-dnr 3.1.8:
    // If additional data is supplied (i.e. not ADN only mode),
    // the option includes at least one valid IP address.
    if (addr_length_ == 0) {
        isc_throw(OutOfRange, getLogPrefix()
                                  << "Addr Len=" << addr_length_
                                  << " but it must contain at least one valid IP address");
    }

    begin += getAddrLengthSize();
    OptionBufferConstIter addr_begin = begin;
    OptionBufferConstIter addr_end = addr_begin + addr_length_;

    while (addr_begin != addr_end) {
        const uint8_t* ptr = &(*addr_begin);
        addIpAddress(IOAddress(readUint32(ptr, std::distance(addr_begin, addr_end))));
        addr_begin += V4ADDRESS_LEN;
        begin += V4ADDRESS_LEN;
    }
}

void
DnrInstance::unpackSvcParams(OptionBufferConstIter& begin, OptionBufferConstIter end) {
    svc_params_length_ = std::distance(begin, end);
    if (svc_params_length_ > 0) {
        svc_params_.assign(begin, end);
        checkSvcParams();
        begin += svc_params_length_;
    }
}

void
DnrInstance::initMembers() {
    dnr_instance_data_length_size_ = (universe_ == Option::V6) ? 0 : 2;
    adn_length_size_ = (universe_ == Option::V6) ? 2 : 1;
    addr_length_size_ = (universe_ == Option::V6) ? 2 : 1;
    minimal_length_ = dnr_instance_data_length_size_ + SERVICE_PRIORITY_SIZE + adn_length_size_;
    log_prefix_ =
        (universe_ == Option::V4) ?
            ("DHCPv4 Encrypted DNS Option (" + std::to_string(DHO_V4_DNR) + ") malformed: ") :
            ("DHCPv6 Encrypted DNS Option (" + std::to_string(D6O_V6_DNR) + ") malformed: ");
}

}  // namespace dhcp
}  // namespace isc