models.go

package tlsmodel

import (
	"bytes"
	"crypto/dsa"
	"crypto/ecdsa"
	"crypto/rsa"
	"crypto/tls"
	cryptotls "crypto/tls"
	"crypto/x509"
	"encoding/gob"
	"encoding/json"
	"fmt"
	"log"
	"math/big"
	"net"
	"sort"
	"strconv"
	"strings"
	"time"
)

var (
	//tls13KeyExchange is a constant to identify a key exchange or MAC/PRF in a TLS3 cipher
	tls13KeyExchange = "TLSv1.3"

	//NkxErrorMessage error message
	NkxErrorMessage = "Not a key exchange message"
)

//CipherConfig extracts the important elements of a Ciphersuit based on its name
type CipherConfig struct {
	CipherID               uint16
	Cipher                 string
	KeyExchange            string
	Authentication         string
	IsExport               bool
	SupportsForwardSecrecy bool
	Encryption             string
	MACPRF                 string //MAC (TLS <=1.1) or PseudoRandomFunction (TLS >= 1.2)
}

//IsAuthenticated returns whether the cipher supports authentication
func (cc *CipherConfig) IsAuthenticated() bool {
	return !(cc.Authentication == "NULL" || cc.Authentication == "anon")
}

func rsaPerformanceMultiplier(keyLength int) int {
	switch keyLength {
	case 1024:
		return 2
	case 2048:
		return 4
	case 3072:
		return 8
	default:
		return 10

	}
}

func dhPerformanceMultiplier(keyLength int) int {
	switch keyLength {
	case 1024:
		return 1
	case 2048:
		return 2
	case 3072:
		return 3
	default:
		return 10

	}
}
func (cc *CipherConfig) getKXPerfMultiplier(config CipherConfigParameters) int {
	if cc.usesRSAKeyExchange() {
		return rsaPerformanceMultiplier(config.RSABitLength)
	}
	if cc.usesDHKeyExchange() {
		return dhPerformanceMultiplier(config.SupportedGroupStrength)
	}
	return 10
}

func (cc *CipherConfig) getKXPerf(config CipherConfigParameters) int {
	switch cc.KeyExchange {
	case "NULL":
		return 1
	case "ECDH":
		return 2 * cc.getKXPerfMultiplier(config)
	case "ECDHE":
		return 3 * cc.getKXPerfMultiplier(config)
	case "RSA":
		return 4 * cc.getKXPerfMultiplier(config)
	case "DH":
		return 5 * cc.getKXPerfMultiplier(config)
	case "DHE":
		return 6 * cc.getKXPerfMultiplier(config)
	case "KRB5": //from here is arbitrary - don't care
		return 100
	case "PSK":
		return 100
	case "ECCPWD":
		return 100
	case "SRP":
		return 100

	}
	if strings.Contains(cc.Cipher, "SCSV") {
		//these are signalling ciphers just return a large multiplier
		return 100
	}
	return -1
}

func (cc *CipherConfig) getAuthPerf() int {
	switch cc.Authentication {
	case "anon":
		return 1
	case "NULL":
		return 1
	case "ECDSA":
		return 2
	case "SHA":
		return 3
	case "RSA":
		return 4
	case "DHE":
		return 5
	case "DSS": //from here is arbitrary - don't care
		return 10
	case "PSK":
		return 10
	case "KRB5":
		return 10
	case "ECCPWD":
		return 10
	case "SRP":
		return 10
	}
	if strings.Contains(cc.Cipher, "SCSV") {
		//these are signalling ciphers just return a large multiplier
		return 10
	}
	return -1
}

func (cc *CipherConfig) getMACPRFPerf() int {
	switch cc.MACPRF {
	case "NULL":
		return 1
	case "MD5":
		return 2
	case "SHA":
		return 3
	case "SHA256":
		return 4
	case "SHA384":
		return 5
	}
	if strings.Contains(cc.Cipher, "SCSV") {
		//these are signalling ciphers just return a large multiplier
		return 10
	}
	return -1
}

func (cc *CipherConfig) getEncAlg() string {
	alg := strings.Split(cc.Encryption, "_")

	switch alg[0] {
	case "NULL":
		return "NULL"
	case "AES":
		return "AES"
	case "CAMELLIA":
		return "CAMELLIA"
	case "DES":
		return "DES"
	case "CHACHA20":
		return "CHACHA20"
	case "DES40":
		return "DES40"
	case "IDEA":
		return "IDEA"
	case "ARIA":
		return "ARIA"
	case "RC4":
		return "RC4"
	case "RC2":
		return "RC2"
	case "SEED":
		return "SEED"
	case "3DES":
		if len(alg) > 1 && alg[1] == "EDE" {
			return "3DES_EDE"
		}
		return "NA"

	}
	if strings.Contains(cc.Cipher, "SCSV") {
		//these are signalling ciphers just return a large multiplier
		return "NA"
	}
	return "NA"
}

func (cc *CipherConfig) getEncAlgPerf() int {
	switch cc.getEncAlg() {
	case "NULL":
		return 1
	case "AES":
		return 2
	case "RC2":
		return 3
	case "RC4":
		return 3
	case "CAMELLIA":
		return 4
	case "CHACHA20":
		return 4
	case "SEED":
		return 5
	case "DES40":
		return 6
	case "DES":
		return 6
	case "3DES_EDE":
		return 7
	case "ARIA": //from here is arbitrary - don't care
		return 10
	case "IDEA":
		return 10
	}
	if strings.Contains(cc.Cipher, "SCSV") {
		//these are signalling ciphers just return a large multiplier
		return 10
	}
	return -1
}

func (cc *CipherConfig) getEncKeyPerf() int {
	switch cc.GetEncryptionKeyLength() {
	case 0:
		return 1
	case 40:
		return 2
	case 56:
		return 3
	case 112:
		return 4
	case 128:
		return 5
	case 256:
		return 6

	}
	if strings.Contains(cc.Cipher, "SCSV") {
		//these are signalling ciphers just return a large multiplier
		return 10
	}
	return -1
}

func (cc *CipherConfig) getEncMode() string {
	if strings.Contains(cc.Encryption, "CBC") {
		return "CBC"
	}

	if strings.Contains(cc.Encryption, "CCM_8") {
		return "CCM_8"
	}

	if strings.Contains(cc.Encryption, "RC4") {
		return "RC4"
	}
	mode := strings.Split(cc.Encryption, "_")

	switch mode[len(mode)-1] {
	case "GCM":
		return "GCM"
	case "CBC":
		return "CBC"
	case "CCM":
		return "CCM"
	case "MD5":
		return "MD5"
	case "NULL":
		return "NULL"
	case "POLY1305":
		return "POLY1305"
	}
	return mode[len(mode)-1]
}

func (cc *CipherConfig) getEncModePerf() int {
	switch cc.getEncMode() {
	case "NULL":
		return 1
	case "GCM":
		return 2
	case "MD5":
		return 3
	case "RC4":
		return 3
	case "POLY1305":
		return 4
	case "CCM":
		return 4
	case "CCM_8":
		return 4
	case "CBC":
		return 5
	}
	if strings.Contains(cc.Cipher, "SCSV") {
		//these are signalling ciphers just return a large multiplier
		return 10
	}
	return -1
}

//GetEncryptionKeyLength returns the effective key lengths of encryption algorithms used in the cipher
//See https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r4.pdf for details
func (cc *CipherConfig) GetEncryptionKeyLength() int {
	kl := -1 //key length
	enc := cc.Encryption
	switch {
	case enc == "NULL" || cc.Cipher == "TLS_EMPTY_RENEGOTIATION_INFO_SCSV" || cc.Cipher == "TLS_FALLBACK_SCSV":
		kl = 0
	case strings.Contains(enc, "3DES"):
		kl = 112
	case strings.Contains(enc, "DES40") || strings.Contains(enc, "CBC_40"):
		kl = 40
	case enc == "DES_CBC":
		kl = 56
	case enc == "SEED_CBC" || enc == "IDEA_CBC": //see https://tools.ietf.org/html/rfc4269 for SEED.
		kl = 128
	case enc == "CHACHA20_POLY1305": //see https://tools.ietf.org/html/rfc7539#section-4
		kl = 256
	case len(strings.Split(enc, "_")) >= 2:
		k := strings.Split(enc, "_")[1]
		kk, err := strconv.Atoi(k)
		if err != nil {
			kl = -1
		} else {
			kl = kk
		}
	}
	return kl
}

//GetKeyExchangeKeyLength returns the key length indicated by the cipher
func (cc *CipherConfig) GetKeyExchangeKeyLength(cipher, protocol uint16, scan ScanResult) int {
	kl := -1
	kx := cc.KeyExchange
	switch {
	case kx == "NULL":
		kl = 0
	case cc.Authentication == "anon":
		kl = 0
	case kx == "RSA" || (cc.Authentication == "RSA" && strings.Contains(kx, "DH") && func() bool {
		//deal with DH ciphers that use RSA for key exchange
		ex, ok := scan.KeyExchangeByProtocolByCipher[protocol]
		if ok {
			if _, ok2 := ex[cipher]; !ok2 { //ensure that the cipher does not actually exchange keys
				return true
			}
		}
		return false
	}()):
		if c, ok := scan.CertificatesPerProtocol[protocol]; ok {
			certs, err := c.GetCertificates()
			if err == nil && len(certs) > 0 && certs[0].PublicKeyAlgorithm.String() == "RSA" {
				if pub, ok := certs[0].PublicKey.(*rsa.PublicKey); ok {
					kl = pub.N.BitLen()
				}
			}
		}
	case cc.Authentication == "RSA" && strings.HasPrefix(kx, "DH"):
		if ex, ok := scan.KeyExchangeByProtocolByCipher[protocol]; ok {
			if kex, ok2 := ex[cipher]; ok2 { // there is a key exchange data
				if key := kex.Key; len(key) > 1 {
					length := int(key[0])<<8 | int(key[1])
					kxch := key[2 : 2+length]
					Public := new(big.Int).SetBytes(kxch)
					return Public.BitLen()
				}
			}
		}
	case strings.Contains(kx, "ECDH"): // see https://www.ietf.org/rfc/rfc5480.txt and pp 133 https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-56Ar3.pdf for comparable strength
		if ex, ok := scan.KeyExchangeByProtocolByCipher[protocol]; ok {
			if kex, ok := ex[cipher]; ok {
				if key := kex.Key; len(key) > 2 {
					cid := uint16(key[1])<<8 | uint16(key[2])
					if k, ok := SupportedGroupStrength[cid]; ok {
						kl = k
					}
				}
			}
		}

	case strings.Contains(kx, tls13KeyExchange):
		if ex, ok := scan.KeyExchangeByProtocolByCipher[protocol]; ok {
			if kex, ok := ex[cipher]; ok {
				if cid := uint16(kex.Group); cid != 0 {
					if k, ok := SupportedGroupStrength[cid]; ok {
						kl = k
					}
				}
			}
		}
	}

	return kl
}

//getContextFreeKeyExchangeKeyLength returns the key length indicated by the cipher and key exchange config
func (cc *CipherConfig) getContextFreeKeyExchangeKeyLength(config CipherConfigParameters) int {
	if cc.KeyExchange == "NULL" {
		return 0
	}
	if cc.usesRSAKeyExchange() {
		return config.RSABitLength
	}
	if cc.usesDHKeyExchange() {
		return config.SupportedGroupStrength
	}
	return -1
}

func (cc *CipherConfig) usesRSAKeyExchange() bool {
	kx := cc.KeyExchange
	if kx == "RSA" || (cc.Authentication == "RSA" && strings.Contains(kx, "DH")) {
		return true
	}
	return false
}

func (cc *CipherConfig) usesDHKeyExchange() bool {
	if cc.Authentication != "RSA" && strings.Contains(cc.KeyExchange, "DH") {
		return true
	}
	return false
}

//ComputeContextFreeMetric calculates interesting metrics about the cipher
func (cc *CipherConfig) ComputeContextFreeMetric(config CipherConfigParameters) (metric CipherMetrics) {
	metric.KeyExchangeStrength = mapKeyExchangeKeylengthToScore(cc.getContextFreeKeyExchangeKeyLength(config))
	metric.EncryptionKeyStrength = mapEncKeyLengthToScore(cc.GetEncryptionKeyLength())
	if cc.IsAuthenticated() {
		metric.Authentication = 100
	}
	metric.MacPRF = cc.GetMACPRFStrength()
	metric.Performance = cc.getPerformanceMetric(config)
	if cc.SupportsForwardSecrecy {
		metric.ForwardSecrecy = 100
	}
	metric.ConfigParams = config
	metric.CipherConfig = *cc
	metric.OverallScore = (10*metric.Authentication + 30*metric.ForwardSecrecy + 10*metric.KeyExchangeStrength +
		40*metric.EncryptionKeyStrength + 10*metric.MacPRF) / 100
	return
}

func (cc *CipherConfig) getPerformanceMetric(config CipherConfigParameters) int {
	return ((cc.getKXPerf(config)) * cc.getAuthPerf() * cc.getEncAlgPerf() * cc.getEncKeyPerf() *
		cc.getEncModePerf() * cc.getMACPRFPerf())
}

//GetMACPRFStrength returns the relative strength of the MAC/PRF algorithm
func (cc *CipherConfig) GetMACPRFStrength() int {
	if strings.Contains(cc.Cipher, "SCSV") {
		return 0
	}
	strength := -1
	switch cc.MACPRF {
	case "SHA384":
		strength = 100
	case "SHA256":
		strength = 90
	case "SHA":
		strength = 50
	case "MD5":
		strength = 20
	case "NULL":
		strength = 0
	default:
		strength = -1
	}
	return strength
}

//EnumerateCipherMetrics enumerates metrics for ciphers along multiple config axes
func EnumerateCipherMetrics() (metrics []CipherMetrics) {
	strengthToSupportedGroups := make(map[int][]string)

	for nc, kx := range SupportedGroupStrength {
		if kx >= 0 && kx == 3072 {
			if ncs, present := strengthToSupportedGroups[kx]; present {
				strengthToSupportedGroups[kx] = append(ncs, SupportedGroups[nc])
			} else {
				strengthToSupportedGroups[kx] = []string{SupportedGroups[nc]}
			}
		}
	}
	// RSALengths := []int{1024, 2048, 3072}
	RSALengths := []int{2048}

	rsaParams := []CipherConfigParameters{}
	for _, rsa := range RSALengths {
		rsaParams = append(rsaParams, CipherConfigParameters{
			RSABitLength: rsa,
		})
	}

	dheParams := []CipherConfigParameters{}
	for kx := range strengthToSupportedGroups {
		dheParams = append(dheParams, CipherConfigParameters{
			SupportedGroupStrength: kx,
			SupportedGroups:        strengthToSupportedGroups[kx],
		})
	}

	ccs := []CipherConfig{}

	dummyConfig := CipherConfigParameters{}
	for c := range CipherSuiteMap {
		if cc, err := GetCipherConfig(c); err == nil {
			ccs = append(ccs, cc)
		}
	}
	for _, cc := range ccs {
		if cc.usesRSAKeyExchange() {
			for _, param := range rsaParams {
				m := cc.ComputeContextFreeMetric(param)
				metrics = append(metrics, m)
			}
			continue
		}

		if cc.usesDHKeyExchange() {
			for _, param := range dheParams {
				m := cc.ComputeContextFreeMetric(param)
				metrics = append(metrics, m)
			}
			continue
		}

		m := cc.ComputeContextFreeMetric(dummyConfig)
		metrics = append(metrics, m)
	}
	sort.Sort(CipherMetricsSorter(metrics))
	return
}

//CipherConfigParameters contains information about Parameters for determining the key length of key exchange algorithms and other cipher parameters
type CipherConfigParameters struct {
	RSABitLength           int //The RSA key from the certificate
	SupportedGroupStrength int
	SupportedGroups        []string //The Supported Groups that have the indicated strength
}

//CipherMetrics are various metrics of interest to compare ciphers as the bases for various desirable property ordering such as security and performance
type CipherMetrics struct {
	Authentication        int
	KeyExchangeStrength   int
	ForwardSecrecy        int
	EncryptionKeyStrength int
	MacPRF                int
	Performance           int
	OverallScore          int
	ConfigParams          CipherConfigParameters
	CipherConfig          CipherConfig
}

func isTLS13Cipher(cipher uint16) bool {
	for _, x := range TLS13Ciphers {
		if x == cipher {
			return true
		}
	}
	return false
}

func getCipherConfig13(cipher uint16) (config CipherConfig, err error) {
	if cipherName, exists := CipherSuiteMap[cipher]; exists {
		config.CipherID = cipher
		config.Cipher = cipherName
		config.KeyExchange = tls13KeyExchange
		config.Authentication = tls13KeyExchange
		cipherName = strings.TrimPrefix(cipherName, "TLS_")
		//set these values temporarily
		config.MACPRF = tls13KeyExchange
		config.Encryption = cipherName
		if strings.Contains(cipherName, "SHA256") {
			config.MACPRF = "SHA256"
			config.Encryption = strings.TrimSuffix(cipherName, "_SHA256")
		} else if strings.Contains(cipherName, "SHA384") {
			config.MACPRF = "SHA384"
			config.Encryption = strings.TrimSuffix(cipherName, "_SHA384")
		}

		return
	}
	return config, fmt.Errorf("The cipher id 0x%x is not recognised", cipher)
}

//GetCipherConfig extracts a `CipherConfig` using the Cipher's IANA string name
// Details here https://www.iana.org/assignments/tls-parameters/tls-parameters.txt
func GetCipherConfig(cipher uint16) (config CipherConfig, err error) {
	if cipherName, exists := CipherSuiteMap[cipher]; exists {
		config.CipherID = cipher
		config.Cipher = cipherName
		if cipherName == "TLS_EMPTY_RENEGOTIATION_INFO_SCSV" || cipherName == "TLS_FALLBACK_SCSV" {
			return
		}
		if isTLS13Cipher(cipher) {
			return getCipherConfig13(cipher)
		}
		cipherName = strings.TrimPrefix(cipherName, "TLS_")

		cs := strings.Split(cipherName, "_WITH_")
		if len(cs) != 2 {
			return config, fmt.Errorf("Expects a cipher name that contains _WITH_ but got %s", config.Cipher)
		}
		kxAuth, encMAC := cs[0], cs[1]
		config.IsExport = strings.Contains(kxAuth, "EXPORT")
		ka := strings.Split(kxAuth, "_")
		if len(ka) == 1 {
			config.KeyExchange = ka[0]
			config.Authentication = ka[0]
		}
		if len(ka) >= 2 {
			if ka[1] == "EXPORT" {
				config.KeyExchange = ka[0]
				config.Authentication = ka[0]
			} else {
				config.KeyExchange = ka[0]
				config.Authentication = ka[1]
			}
		}

		if strings.Contains(config.KeyExchange, "DHE") {
			config.SupportsForwardSecrecy = true
		}

		em := strings.Split(encMAC, "_")
		m := em[len(em)-1]
		if strings.Contains(m, "SHA") || strings.Contains(m, "MD5") || m == "NULL" {
			config.MACPRF = m
			config.Encryption = strings.Join(em[:len(em)-1], "_")
		} else if strings.Contains(encMAC, "CCM") {
			config.MACPRF = "SHA256" // see https://tools.ietf.org/html/rfc6655#section-4
			config.Encryption = encMAC
		} else {
			config.Encryption = encMAC
		}
		return
	}
	return config, fmt.Errorf("The cipher id 0x%x is not recognised", cipher)
}

//ScanData is the Human-readable result of a given scan
type ScanData struct {
	ScanRequest AdvancedScanRequest
	Results     map[int][]HumanScanResult //ScanGroup index (in the ASR) -> human scan results
}

//ScanGroup is a grouping of CIDR ranges to be scanned with descriptions, useful for reporting
type ScanGroup struct {
	Description string   `yaml:"description"` //Freeform text used in reporting
	CIDRRanges  []string `yaml:"cidrRanges"`
}

//AdvancedScanRequest is a model to describe a given TLS Audit scan
type AdvancedScanRequest struct {
	Config ScanConfig
	//Next two fields will be automatically set once scan starts
	Day        string //Date the scan was run in the format yyyy-mm-dd
	ScanID     string //Non-empty ScanID means this is a ScanRequest to resume an existing, possibly incomplete, scan
	ScanGroups []ScanGroup
}

//GroupedHost exploded hosts from an associated ScanGroup
type GroupedHost struct {
	ScanGroup ScanGroup
	Hosts     []string
}

//PersistedScanRequest persisted version of ScanRequest
type PersistedScanRequest struct {
	Request      AdvancedScanRequest
	GroupedHosts []GroupedHost
	ScanStart    time.Time
	ScanEnd      time.Time
	Progress     int
	HostCount    int
}

// //ServerResultSummary is a mini report of scan result
// type ServerResultSummary struct {
// 	Server   string
// 	HostName string
// 	Port     string
// 	Grade    string
// }

//ScanResultSummary is the summary of a scan result session
type ScanResultSummary struct {
	Request          AdvancedScanRequest
	ScanStart        time.Time
	ScanEnd          time.Time
	Progress         int
	HostCount        int
	PortCount        int
	BestGrade        string
	WorstGrade       string
	HostGrades       map[string]string
	GradeToHostPorts map[string][]string
}

//Marshall scan request
func (psr PersistedScanRequest) Marshall() []byte {
	result := bytes.Buffer{}
	gob.Register(PersistedScanRequest{})
	err := gob.NewEncoder(&result).Encode(&psr)
	if err != nil {
		log.Print(err)
	}
	return result.Bytes()
}

//UnmasharlPersistedScanRequest builds PersistedScanRequest from bytes
func UnmasharlPersistedScanRequest(data []byte) (PersistedScanRequest, error) {

	psr := PersistedScanRequest{}
	gob.Register(psr)
	buf := bytes.NewBuffer(data)
	err := gob.NewDecoder(buf).Decode(&psr)
	if err != nil {
		return psr, err
	}
	return psr, nil
}

//ScanProgress contains partial scam results with an indication of progress
type ScanProgress struct {
	ScanID      string
	Progress    float32
	ScanResults []HumanScanResult // this is the latest scan results delta, at the end of scan all cummulative scans are sent
	Narrative   string            //freeflow text
}

//ScanConfig describes details of how the TLS scan should be carried out
type ScanConfig struct {
	ProtocolsOnly bool
	Timeout       int
	//Number of Packets per Second to send out during underlying port scan
	PacketsPerSecond int
	//Suppress certificate output
	HideCerts bool
	//Suppress output of TLS status of closed ports or ports with no TLS
	HideNoTLS bool
	//control whether to produce a running commentary of scan progress or stay quiet till the end
	Quiet       bool
	ServicePort int
}

//SecurityScore contains the overall grading of a TLS/SSL port
type SecurityScore struct {
	ProtocolScore         int
	KeyExchangeScore      int
	CipherEncryptionScore int
	CertificateScore      int
	Grade                 string
	Warnings              []string
}

//OrderGrade allows a simple numeric ordering of TLS grades. Actual values don't matter
func (SecurityScore) OrderGrade(grade string) int {
	switch grade {
	case "A+":
		return 120
	case "A":
		return 118
	case "B":
		return 116
	case "C":
		return 114
	case "D":
		return 112
	case "E":
		return 110
	case "F":
		return 108
	case "T":
		return 106
	case "TA+":
		return 20
	case "TA":
		return 18
	case "TB":
		return 16
	case "TC":
		return 14
	case "TD":
		return 12
	case "TE":
		return 10
	case "TF":
		return 8
	case "U":
		return 6
	case "Worst": // used to indicate worst case before data
		return 200
	case "Best": //used to indicate best case before data
		return -200
	case "":
		return 200
	default:
		return -200
	}
}

// KeyExchangeAlgorithm says what it is
type KeyExchangeAlgorithm int

//HostAndPort is a model representing a hostname and a given port
type HostAndPort struct {
	Hostname string
	Port     string
}

// ServerHelloMessage is the TLS server hello message
type ServerHelloMessage struct {
	Raw                          []byte
	Vers                         uint16
	Random                       []byte
	SessionId                    []byte
	CipherSuite                  uint16
	CompressionMethod            uint8
	NextProtoNeg                 bool
	NextProtos                   []string
	OcspStapling                 bool
	Scts                         [][]byte
	TicketSupported              bool
	SecureRenegotiation          []byte
	SecureRenegotiationSupported bool
	AlpnProtocol                 string
	SupportedVersion             uint16
	ServerShare                  KeyShare
	SelectedIdentityPresent      bool
	SelectedIdentity             uint16

	// HelloRetryRequest extensions
	cookie        []byte
	selectedGroup CurveID

	RawHello interface{}
}

// CurveID is the type of a TLS identifier for an elliptic curve. See
// https://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-8.
//
// In TLS 1.3, this type is called NamedGroup, but at this time this library
// only supports Elliptic Curve based groups. See RFC 8446, Section 4.2.7.
type CurveID uint16

//KeyShare TLS 1.3 Key Share. See RFC 8446, Section 4.2.8.
type KeyShare struct {
	Group CurveID
	Data  []byte
}

// ServerKeyExchangeMsg is the key exchange message
type ServerKeyExchangeMsg struct {
	// Raw []byte
	Key   []byte
	Group CurveID // for TLS v1.3
}

// HelloAndKey bundles server hello and ServerKeyExchange messages
type HelloAndKey struct {
	Hello  ServerHelloMessage
	Key    ServerKeyExchangeMsg
	HasKey bool
}

// CertificateMessage simply exporting the internal certificateMsg
type CertificateMessage struct {
	// Raw          []byte
	Certificates [][]byte
	Certs        []*x509.Certificate
}

//GetCertificates returns the list of certificates in a TLS certificate message
func (cert *CertificateMessage) GetCertificates() (certs []*x509.Certificate, e error) {
	if cert.Certs == nil {
		for _, c := range cert.Certificates {
			cc, err := x509.ParseCertificate(c)
			if err != nil {
				return certs, err
			}
			certs = append(certs, cc)
		}
		cert.Certs = certs
	} else {
		certs = cert.Certs
	}
	return

}

// ScanResult is the scan result of a server TLS settings
type ScanResult struct {
	Server                                 string
	Port                                   string
	SupportedProtocols                     []uint16
	HasCipherPreferenceOrderByProtocol     map[uint16]bool
	CipherPreferenceOrderByProtocol        map[uint16][]uint16
	OcspStaplingByProtocol                 map[uint16]bool
	SelectedCipherByProtocol               map[uint16]uint16
	ALPNByProtocol                         map[uint16]string
	SecureRenegotiationSupportedByProtocol map[uint16]bool
	CipherSuiteByProtocol                  map[uint16][]uint16
	ServerHelloMessageByProtocolByCipher   map[uint16]map[uint16]ServerHelloMessage
	CertificatesPerProtocol                map[uint16]CertificateMessage
	KeyExchangeByProtocolByCipher          map[uint16]map[uint16]ServerKeyExchangeMsg
	IsSTARTLS                              bool
	IsSSH                                  bool
	SupportsTLSFallbackSCSV                bool
	GroupID                                int //ScanRequest Host Group index
}

//UnmarsharlScanResult builds ScanResults from bytes
func UnmarsharlScanResult(data []byte) ([]ScanResult, error) {

	sr := []ScanResult{}
	gob.Register(sr)
	buf := bytes.NewBuffer(data)
	err := gob.NewDecoder(buf).Decode(&sr)
	if err != nil {
		return sr, err
	}
	return sr, nil
}

//HumanScanResult is a Stringified version of ScanResult
type HumanScanResult struct {
	Server                                 string
	HostName                               string
	Port                                   string
	SupportsTLS                            bool
	SupportedProtocols                     []string
	HasCipherPreferenceOrderByProtocol     map[string]bool
	CipherPreferenceOrderByProtocol        map[string][]string
	OcspStaplingByProtocol                 map[string]bool
	SelectedCipherByProtocol               map[string]string
	ALPNByProtocol                         map[string]string
	SecureRenegotiationSupportedByProtocol map[string]bool
	CipherSuiteByProtocol                  map[string][]string
	// ServerHelloMessageByProtocolByCipher   map[string]map[string]ServerHelloMessage
	CertificatesPerProtocol map[string][]HumanCertificate
	// KeyExchangeByProtocolByCipher          map[string]map[string]ServerKeyExchangeMsg
	IsSTARTLS               bool
	IsSSH                   bool
	SupportsTLSFallbackSCSV bool
	Score                   SecurityScore
	GroupID                 int //ScanRequest Host Group index
}

//HumanCertificate is a "string" representation of various attributes of a certificate
type HumanCertificate struct {
	Subject            string
	SubjectSerialNo    string
	SubjectCN          string
	SubjectAN          string
	SerialNumber       string
	Issuer             string
	PublicKeyAlgorithm string
	ValidFrom          string
	ValidUntil         string
	Key                string
	SignatureAlgorithm string
	Signature          string
	OcspStapling       bool
	RevocationDetail   string
}

func getCurve(protocol, cipher uint16, scan ScanResult) string {
	curveID := ""
	if c, ok := scan.KeyExchangeByProtocolByCipher[protocol]; ok {
		if ex, ok := c[cipher]; ok {
			if cid := uint16(ex.Group); cid != 0 { // we would have set the CurveID group in TLS v1.3 and above
				curveID = fmt.Sprintf(" (Supported Group: %s)", SupportedGroups[cid])
			} else {
				key := ex.Key
				if len(key) > 4 && key[0] == 3 {
					//Supported Group
					cid := uint16(key[1])<<8 | uint16(key[2])
					curveID = fmt.Sprintf(" (Supported Group: %s)", SupportedGroups[cid])
				}
			}
		}
	}
	return fmt.Sprintf("%s (0x%x) %s", CipherSuiteMap[cipher], cipher, curveID)
}

//ToStringStruct returns a string-decoded form of ScanResult
func (s ScanResult) ToStringStruct() (out HumanScanResult) {
	out.GroupID = s.GroupID
	out.Server = s.Server
	ip, err := net.LookupAddr(s.Server)
	if err == nil {
		out.HostName = strings.Join(ip, ", ")
	}
	out.Port = s.Port
	out.SupportsTLS = s.SupportsTLS()
	for _, p := range s.SupportedProtocols {
		out.SupportedProtocols = append(out.SupportedProtocols, TLSVersionMap[p])
	}
	out.HasCipherPreferenceOrderByProtocol = make(map[string]bool)
	for p := range s.HasCipherPreferenceOrderByProtocol {
		out.HasCipherPreferenceOrderByProtocol[TLSVersionMap[p]] = s.HasCipherPreferenceOrderByProtocol[p]
	}
	out.CipherPreferenceOrderByProtocol = make(map[string][]string)
	for k, v := range s.CipherPreferenceOrderByProtocol {
		ciphers := []string{}
		if s.HasCipherPreferenceOrderByProtocol[k] {
			for _, c := range v {
				ciphers = append(ciphers, fmt.Sprintf("%s,%s", getCurve(k, c, s), scoreCipher(c, k, s)))
			}
		}
		out.CipherPreferenceOrderByProtocol[TLSVersionMap[k]] = ciphers
	}
	out.OcspStaplingByProtocol = make(map[string]bool)
	for k, v := range s.OcspStaplingByProtocol {
		out.OcspStaplingByProtocol[TLSVersionMap[k]] = v
	}

	out.SelectedCipherByProtocol = make(map[string]string)
	for k, v := range s.SelectedCipherByProtocol {
		out.SelectedCipherByProtocol[TLSVersionMap[k]] = getCurve(k, v, s)
	}

	out.ALPNByProtocol = make(map[string]string)
	for k, v := range s.ALPNByProtocol {
		out.ALPNByProtocol[TLSVersionMap[k]] = v
	}

	out.SecureRenegotiationSupportedByProtocol = make(map[string]bool)
	for k, v := range s.SecureRenegotiationSupportedByProtocol {
		out.SecureRenegotiationSupportedByProtocol[TLSVersionMap[k]] = v
	}

	out.CipherSuiteByProtocol = make(map[string][]string)
	for k, v := range s.CipherSuiteByProtocol {
		ciphers := []string{}
		for _, c := range v {
			ciphers = append(ciphers, fmt.Sprintf("%s,%s", getCurve(k, c, s), scoreCipher(c, k, s)))
		}
		out.CipherSuiteByProtocol[TLSVersionMap[k]] = ciphers
	}

	out.CertificatesPerProtocol = make(map[string][]HumanCertificate)
	for p, c := range s.CertificatesPerProtocol {
		certs, err := c.GetCertificates()
		out.CertificatesPerProtocol[TLSVersionMap[p]] = []HumanCertificate{}
		if err != nil {
			continue
		}

		for _, cert := range certs {
			certKey := ""
			if key, ok := cert.PublicKey.(*rsa.PublicKey); ok {
				certKey = fmt.Sprintf("%d bits (e %d)", key.N.BitLen(), key.E)
			}
			sigLen := len(cert.Signature) - 1
			sig := fmt.Sprintf("%x...%x", cert.Signature[:8], cert.Signature[sigLen-8:sigLen])
			ocsp := false
			if o, ok := s.OcspStaplingByProtocol[p]; ok {
				ocsp = o
			}
			out.CertificatesPerProtocol[TLSVersionMap[p]] = append(out.CertificatesPerProtocol[TLSVersionMap[p]],
				HumanCertificate{
					Subject:            cert.Subject.String(),
					SubjectSerialNo:    cert.Subject.SerialNumber,
					SubjectCN:          cert.Subject.CommonName,
					SubjectAN:          strings.Join(cert.DNSNames, ", "),
					SerialNumber:       cert.SerialNumber.String(),
					Issuer:             cert.Issuer.String(),
					PublicKeyAlgorithm: cert.PublicKeyAlgorithm.String(),
					ValidFrom:          cert.NotBefore.String(),
					ValidUntil:         cert.NotAfter.String(),
					Key:                certKey,
					SignatureAlgorithm: cert.SignatureAlgorithm.String(),
					Signature:          sig,
					OcspStapling:       ocsp,
					RevocationDetail:   revokers(cert),
				})

		}
	}
	out.IsSTARTLS = s.IsSTARTLS
	out.IsSSH = s.IsSSH
	out.SupportsTLSFallbackSCSV = s.SupportsTLSFallbackSCSV
	out.Score = s.CalculateScore()
	return
}

func revokers(cert *x509.Certificate) string {
	revs := []string{}
	ocsp := ""
	crl := ""
	if len(cert.OCSPServer) > 0 {
		revs = append(revs, "OCSP")
		ocsp = fmt.Sprintf("OCSP: %s ", strings.Join(cert.OCSPServer, ", "))
	}
	if len(cert.CRLDistributionPoints) > 0 {
		revs = append(revs, "CRL")
		crl = fmt.Sprintf("CRL: %s ", strings.Join(cert.CRLDistributionPoints, ", "))
	}
	return fmt.Sprintf("%s. %s%s", strings.Join(revs, " and "), ocsp, crl)
}

//ToJSON returns a JSON-formatted string representation of the ScanResult
func (s ScanResult) ToJSON() (js string) {
	if data, err := json.Marshal(s.ToStringStruct()); err == nil {
		return string(data)
	}
	return
}

// SupportsTLS determines whether the port on the specified server supports TLS at all
func (s ScanResult) SupportsTLS() bool {
	if len(s.SupportedProtocols) == 0 {
		return false
	}
	return true
}

//ToString generates a string output
func (s ScanResult) ToString(config ScanConfig) (result string) {
	hn, err := net.LookupAddr(s.Server)
	hostname := s.Server
	if err == nil {
		hostname = strings.Join(hn, ",")
	}
	result += fmt.Sprintf("%s (%s)\n\tPort: %s\n", s.Server, hostname, s.Port)
	if len(s.SupportedProtocols) == 0 {
		if config.HideNoTLS {
			return ""
		}
		result += "\tNo supported SSL/TLS protocol found\n"
	} else {
		sortedSupportedProtocols := s.SupportedProtocols
		sort.Slice(sortedSupportedProtocols, func(i, j int) bool { return sortedSupportedProtocols[i] > sortedSupportedProtocols[j] })
		for _, tls := range sortedSupportedProtocols {
			startTLS := ""
			if s.IsSTARTLS {
				startTLS = " (STARTTLS)"
			}
			result += fmt.Sprintf("\t%s%s:\n", TLSVersionMap[tls], startTLS)
			tls13RenegotiationSupport := ""
			if tls == cryptotls.VersionTLS13 {
				tls13RenegotiationSupport = " (not applicable to TLS v1.3)" // see https://tools.ietf.org/html/rfc8446#section-4.1.2
			}
			result += fmt.Sprintf("\t\tSupports secure renegotiation: %t%s\n", s.SecureRenegotiationSupportedByProtocol[tls], tls13RenegotiationSupport)
			result += fmt.Sprintf("\t\tApplication Layer Protocol Negotiation: %s\n", s.ALPNByProtocol[tls])
			if !config.ProtocolsOnly {

				result += fmt.Sprintf("\t\tHas a cipher preference order: %t\n", s.HasCipherPreferenceOrderByProtocol[tls])
				result += fmt.Sprintf("\t\tSelected cipher when all client ciphers (in numerical order) are presented: %s\n", CipherSuiteMap[s.SelectedCipherByProtocol[tls]])
				if s.HasCipherPreferenceOrderByProtocol[tls] {
					result += "\t\tSupported Ciphersuites (in order of preference):\n"
					for _, cipher := range s.CipherPreferenceOrderByProtocol[tls] {
						result += fmt.Sprintf("\t\t\t%s - %s\n", getCurve(tls, cipher, s), scoreCipher(cipher, tls, s))
					}
				} else {
					result += "\n\t\tSupported Ciphersuites (server has no order preference):\n"
					for _, cipher := range s.CipherSuiteByProtocol[tls] {
						result += fmt.Sprintf("\t\t\t%s - %s\n", getCurve(tls, cipher, s), scoreCipher(cipher, tls, s))
					}
				}
			}
			if certM, ok := s.CertificatesPerProtocol[tls]; !config.HideCerts && ok {
				certs, err := certM.GetCertificates()
				if err == nil && len(certs) > 0 {
					result += "\tCertificate Information:\n"
					cert := certs[0]
					result += "\t\tSubject: " + cert.Subject.String() + "\n\t\tSubject Serial Number: " + cert.Subject.SerialNumber + "\n"
					result += "\t\tSubject Common names: " + cert.Subject.CommonName + "\n"
					result += "\t\tAlternative names: " + strings.Join(cert.DNSNames, ", ") + "\n"
					result += fmt.Sprintf("\t\tSerial Number: %x\n", cert.SerialNumber)
					result += "\t\tValid from: " + cert.NotBefore.String() + "\n"
					result += "\t\tValid until: " + cert.NotAfter.String() + "\n"
					result += "\t\tIssuer: " + cert.Issuer.String() + "\n"
					result += "\t\tSignature algorithm: " + cert.SignatureAlgorithm.String() + "\n"
					sigLen := len(cert.Signature) - 1
					result += fmt.Sprintf("\t\tSignature: %x...%x\n", cert.Signature[:8], cert.Signature[sigLen-8:sigLen])
					if key, ok := cert.PublicKey.(*rsa.PublicKey); ok {
						result += fmt.Sprintf("\t\tKey: %d bits (e %d)\n", key.N.BitLen(), key.E)
					}
					result += fmt.Sprintf("\t\tSupports OCSP stapling: %t\n", s.OcspStaplingByProtocol[tls])
					result += fmt.Sprintf("\t\tChain length: %d\n", len(certs))
					if len(certs) > 1 {
						for i := 0; i < len(certs); i++ {
							c := certs[i]
							result += fmt.Sprintf("\t\t\tChain %d (CA: %t): %s. (Expires: %s)\n", len(certs)-i-1, c.IsCA, c.Subject.String(), c.NotAfter.String())
						}
					}
				}
			}
		}
	}
	score := s.CalculateScore()
	result += "\n======================================================================================"
	result += fmt.Sprintf("\nOverall Grade for %s (%s) on Port %s: %s\n", s.Server, hostname, s.Port, score.Grade)
	result += fmt.Sprintf("Protocol score: %d, Cipher key exchange score: %d, Cipher encryption score: %d\n", score.ProtocolScore, score.KeyExchangeScore, score.CipherEncryptionScore)
	if len(score.Warnings) > 0 {
		result += "Warnings:\n"
		for _, w := range score.Warnings {
			result += fmt.Sprintf("\t%s\n", w)
		}
	}
	result += "======================================================================================\n"
	return
}

func (s ScanResult) String() string {
	return s.ToString(ScanConfig{})
}

//CalculateScore computes an SSLLab-esque score for the scan
// https://github.com/ssllabs/research/wiki/SS
// https://community.qualys.com/docs/DOC-6321-ssl-labs-grading-2018
//SecurityScoreL-Server-Rating-Guide contains the overall grading of a TLS/SSL port
func (s *ScanResult) CalculateScore() (result SecurityScore) {

	max := uint16(0)
	min := uint16(1000)
	for _, p := range s.SupportedProtocols {
		if p > max {
			max = p
		}
		if p < min {
			min = p
		}
	}

	highProtocol := scoreProtocol(max)
	lowProtocol := scoreProtocol(min)

	result.ProtocolScore = (highProtocol + lowProtocol) / 2

	if s.SupportsTLS() {

		cipherKeyExchangeScore := 1000
		cipherStrengthMinScore := 1000
		cipherStrengthMaxScore := 0
		// for _, p := range s.SupportedProtocols {
		p := s.SupportedProtocols[0] // use the strongest protocol
		c := s.SelectedCipherByProtocol[p]
		selectMinimalKeyExchangeScore(c, p, &cipherKeyExchangeScore, &cipherStrengthMinScore, &cipherStrengthMaxScore, *s)
		var cipherSuite []uint16
		if s.HasCipherPreferenceOrderByProtocol[p] {
			cipherSuite = s.CipherPreferenceOrderByProtocol[p]
		} else {
			cipherSuite = s.CipherSuiteByProtocol[p]
		}
		for _, c := range cipherSuite {
			selectMinimalKeyExchangeScore(c, p, &cipherKeyExchangeScore, &cipherStrengthMinScore, &cipherStrengthMaxScore, *s)
		}
		// }

		result.KeyExchangeScore = cipherKeyExchangeScore

		result.CipherEncryptionScore = (cipherStrengthMaxScore + cipherStrengthMinScore) / 2

		result.Grade = toTLSGrade((30*result.ProtocolScore + 30*result.KeyExchangeScore + 40*result.CipherEncryptionScore) / 100)

		scoreCertificate(&result, s)
		result.adjustScore(*s)
	} else {
		//No TLS
		result.Grade = toTLSGrade(-1)
	}
	return
}

func scoreCertificate(score *SecurityScore, scan *ScanResult) {
	for _, c := range scan.CertificatesPerProtocol {
		certs, err := c.GetCertificates()
		if err != nil || len(certs) == 0 {
			cap(score, "T", "Error in obtaining certificates. Untrusted")
			return
		}

		intermediates := x509.NewCertPool()
		for i, cert := range certs {
			if i == 0 {
				continue
			}
			intermediates.AddCert(cert)
		}
		_, err = certs[0].Verify(x509.VerifyOptions{
			Roots:         nil,
			Intermediates: intermediates,
		})
		if err != nil {
			cap(score, "T", "Fails common public CA verification. "+err.Error())
			return
		}
	}
	score.CertificateScore = 100
}

func scoreProtocol(protocol uint16) (score int) {
	switch protocol {
	case VersionSSL20:
		score = 0
	case tls.VersionSSL30:
		score = 80
	case tls.VersionTLS10:
		score = 70 // pegged down from 90
	case tls.VersionTLS11:
		score = 85 // pegged down from 95
	case tls.VersionTLS12:
		score = 100
	case VersionTLS13:
		score = 100
	}
	return
}

//SecurityScore contains the overall grading of a TLS/SSL port
func (score *SecurityScore) adjustScore(scan ScanResult) {

	if !supportsTLS12(scan) {
		cap(score, "C", "TLS v1.2 not suported")
	}

	if supportsSSLV3(scan) {
		cap(score, "C", "Supports SSL v3. Vulnerable to POODLE attack")
	}

	if !supportsPFS(scan) {
		cap(score, "B", "Forward Secrecy not suported")
	}

	if !supportsAEAD(scan) {
		cap(score, "B", "Authenticated Encryption (AEAD) not suported")
	}

	if supportsAnonAuth(scan) {
		cap(score, "F", "Server supports anonymous (insecure) suites")
	}

	adjustUsingCertificateSecurity(score, scan)

	if scan.SupportsTLSFallbackSCSV {
		if score.Grade == "A" {
			score.Grade = "A+"
		} else if score.Grade == "TA" {
			score.Grade = "TA+"
		}
	}
}

func adjustUsingCertificateSecurity(score *SecurityScore, scan ScanResult) {
	for _, c := range scan.CertificatesPerProtocol {
		certs, err := c.GetCertificates()
		if err != nil {
			cap(score, "T", "Error in obtaining certificates. Untrusted")
			return
		}
		for _, cert := range certs {
			publicKey := cert.PublicKey
			switch cert.PublicKeyAlgorithm {
			case x509.RSA:
				if pk, ok := publicKey.(*rsa.PublicKey); ok {
					bitlength := pk.N.BitLen()
					switch {
					case bitlength >= 1024 && bitlength < 2048:
						cap(score, "B", fmt.Sprintf("Public key length is %d (< 2048)", bitlength))
					case bitlength < 1024:
						cap(score, "F", fmt.Sprintf("Public key length is %d (< 1024)", bitlength))
					}
				} else {
					cap(score, "T", fmt.Sprintf("Got malformed public key format"))
				}
			case x509.ECDSA:
				if pk, ok := publicKey.(*ecdsa.PublicKey); ok {
					bitlength := pk.Y.BitLen()
					switch {
					case bitlength >= 1024 && bitlength < 2048:
						cap(score, "B", fmt.Sprintf("Public key length is %d (< 2048)", bitlength))
					case bitlength < 1024:
						cap(score, "F", fmt.Sprintf("Public key length is %d (< 1024)", bitlength))
					}
				} else {
					cap(score, "T", fmt.Sprintf("Got malformed public key format"))
				}
			case x509.DSA:
				if pk, ok := publicKey.(*dsa.PublicKey); ok {
					bitlength := pk.Y.BitLen()
					switch {
					case bitlength >= 1024 && bitlength < 2048:
						cap(score, "B", fmt.Sprintf("Public key length is %d (< 2048)", bitlength))
					case bitlength < 1024:
						cap(score, "F", fmt.Sprintf("Public key length is %d (< 1024)", bitlength))
					}
				} else {
					cap(score, "T", fmt.Sprintf("Got malformed public key format"))
				}
			case x509.UnknownPublicKeyAlgorithm:
				cap(score, "T", "Using anonymous/unknown signature algorithm")
			}

			sigAlgo := cert.SignatureAlgorithm.String()
			switch {
			case strings.Contains(sigAlgo, "MD"): //cap MD2 and MD5 signatures to F
				cap(score, "T", fmt.Sprintf("Insecure/Untrusted %s signature algorithm", sigAlgo))
			case strings.Contains(sigAlgo, "SHA1") || strings.Contains(sigAlgo, "SHA-1"):
				cap(score, "T", fmt.Sprintf("Insecure/Untrusted %s signature algorithm", sigAlgo))
			}
		}
	}
}

//SecurityScore contains the overall grading of a TLS/SSL port
func cap(score *SecurityScore, grade, reason string) {
	score.Warnings = append(score.Warnings, fmt.Sprintf("%s. Grade capped to %s", reason, grade))
	if grade == "T" && score.OrderGrade(score.Grade) > score.OrderGrade("T") {
		score.Grade = "T" + score.Grade
	} else if strings.HasPrefix(score.Grade, "T") && score.OrderGrade(score.Grade) > score.OrderGrade("T"+grade) {
		score.Grade = "T" + grade
	} else if score.OrderGrade(score.Grade) > score.OrderGrade(grade) {
		score.Grade = grade
	}
}

func supportsTLS12(scan ScanResult) (yes bool) {
	for _, p := range scan.SupportedProtocols {
		if p == tls.VersionTLS12 {
			yes = true
			break
		}
	}
	return
}

func supportsSSLV3(scan ScanResult) (yes bool) {
	for _, p := range scan.SupportedProtocols {
		if p == tls.VersionSSL30 {
			yes = true
			break
		}
	}
	return
}

//check Forward Secrecy support
// checks that the default cipher selected per every supported protocol is PFS-capable
func supportsPFS(scan ScanResult) bool {
	pfs := true

	for _, p := range scan.SupportedProtocols {
		if p == tls.VersionTLS13 { //TLS v1.3 only soppurts (EC)DHE key exchange: https://tools.ietf.org/html/rfc8446#section-4.1
			continue
		}
		cipher := scan.SelectedCipherByProtocol[p]
		cc, _ := GetCipherConfig(cipher)
		if !strings.Contains(cc.KeyExchange, "DHE") {
			pfs = false
			break
		}
		if !pfs {
			break
		}
	}
	return pfs
}

//check for anonymous authentication
func supportsAnonAuth(scan ScanResult) bool {
	anon := false

	for _, p := range scan.SupportedProtocols {
		if p == tls.VersionTLS13 { //TLS v1.3 will not do such ciphers
			continue
		}
		var ciphers []uint16
		if scan.HasCipherPreferenceOrderByProtocol[p] {
			ciphers = scan.CipherPreferenceOrderByProtocol[p]
		} else {
			ciphers = scan.CipherSuiteByProtocol[p]
		}
		for _, cipher := range ciphers {
			if cc, err := GetCipherConfig(cipher); err == nil {
				if cc.Authentication == "anon" {
					return true
				}
			}
		}
	}
	return anon
}

//check for Authenticate Encryption with Associated Data (AEAD) support
func supportsAEAD(scan ScanResult) bool {
	aead := false
	for _, aeP := range AEADProtocols {
		for _, p := range scan.SupportedProtocols {
			if p == aeP {
				var ciphers []uint16
				if scan.HasCipherPreferenceOrderByProtocol[p] {
					ciphers = scan.CipherPreferenceOrderByProtocol[p]
				} else {
					ciphers = scan.CipherSuiteByProtocol[p]
				}
				for _, c := range ciphers {
					cc, _ := GetCipherConfig(c)
					if strings.Contains(cc.Encryption, "GCM") || strings.Contains(cc.Encryption, "POLY1305") || strings.Contains(cc.Encryption, "CCM") {
						aead = true
						break
					}
				}
				if aead {
					break
				}
			}
		}
	}
	return aead
}

//see https://github.com/ssllabs/research/wiki/SSL-Server-Rating-Guide
func toTLSGrade(score int) (grade string) {
	switch {
	case score >= 80:
		grade = "A"
	case score >= 65:
		grade = "B"
	case score >= 50:
		grade = "C"
	case score >= 35:
		grade = "D"
	case score >= 20:
		grade = "E"
	case score < 0:
		grade = "U" // for untrusted, possibly plaintext connection
	default:
		grade = "F"
	}
	return
}

func mapKeyExchangeKeylengthToScore(kl int) (score int) {
	switch {
	case kl >= 4096:
		score = 100
	case kl >= 2048:
		score = 90
	case kl >= 1024:
		score = 80
	case kl >= 512:
		score = 40
	case kl > 0:
		score = 20
	default:
		score = 0
	}
	return
}

func mapEncKeyLengthToScore(kl int) (score int) {
	switch {
	case kl >= 256:
		score = 100
	case kl >= 128:
		score = 80
	case kl >= 112: // It seems SSLLabs does this based on some scans that have a high key length of
		// 256 and a low key lenght of 112. The score was 90 = (100+80)/2 instead of the expected 60
		score = 70
	case kl > 0:
		score = 20
	default:
		score = 0
	}
	return
}

func selectMinimalKeyExchangeScore(cipher, protocol uint16, keyExchangeScore, cipherStrengthMinScore, cipherStrengthMaxScore *int, scan ScanResult) {
	if cc, err := GetCipherConfig(cipher); err == nil {
		kl := cc.GetKeyExchangeKeyLength(cipher, protocol, scan)
		if score := mapKeyExchangeKeylengthToScore(kl); score < *keyExchangeScore {
			*keyExchangeScore = score
		}
		ks := cc.GetEncryptionKeyLength()
		score := mapEncKeyLengthToScore(ks)
		if *cipherStrengthMinScore > score {
			*cipherStrengthMinScore = score
		}

		if *cipherStrengthMaxScore < score {
			*cipherStrengthMaxScore = score
		}
	}
}

func scoreCipher(cipher, protocol uint16, scan ScanResult) (score string) {
	if cc, err := GetCipherConfig(cipher); err == nil {
		s := (40*mapEncKeyLengthToScore(cc.GetEncryptionKeyLength()) + 30*scoreProtocol(protocol) +
			30*mapKeyExchangeKeylengthToScore(cc.GetKeyExchangeKeyLength(cipher, protocol, scan))) / 100
		return toTLSGrade(s)
	}
	return
}

//TLSAuditConfig is the configuration of the nmap runner
type TLSAuditConfig struct {
	DailySchedules   []string    `yaml:"dailySchedules"` // in the format 13:45, 01:20 etc
	ServicePort      int         `yaml:"servicePort"`
	IsProduction     bool        `yaml:"isProduction"`
	PacketsPerSecond int         `yaml:"packetsPerSecond"`
	Timeout          int         `yaml:"timeout"`
	ScanGroups       []ScanGroup `yaml:"scanGroups"`
}

//TLSAuditSnapshot a snapshot representing the results of a given scan session
type TLSAuditSnapshot struct {
	Timestamp   time.Time
	ScanResults []ScanResult
}

//TLSAuditSnapshotHuman a snapshot representing the results of a given scan session
type TLSAuditSnapshotHuman struct {
	Timestamp   time.Time
	ScanResults []HumanScanResult
}