client_info.go

package main

import (
	"fmt"
	"strings"

	tls "github.com/jmhodges/howsmyssl/tls110"
)

type rating string

const (
	okay       rating = "Probably Okay"
	improvable rating = "Improvable"
	bad        rating = "Bad"
)

type clientInfo struct {
	GivenCipherSuites              []string            `json:"given_cipher_suites"`
	EphemeralKeysSupported         bool                `json:"ephemeral_keys_supported"`             // good if true
	SessionTicketsSupported        bool                `json:"session_ticket_supported"`             // good if true
	TLSCompressionSupported        bool                `json:"tls_compression_supported"`            // bad if true
	UnknownCipherSuiteSupported    bool                `json:"unknown_cipher_suite_supported"`       // bad if true
	BEASTVuln                      bool                `json:"beast_vuln"`                           // bad if true
	AbleToDetectNMinusOneSplitting bool                `json:"able_to_detect_n_minus_one_splitting"` // neutral
	InsecureCipherSuites           map[string][]string `json:"insecure_cipher_suites"`
	TLSVersion                     string              `json:"tls_version"`
	Rating                         rating              `json:"rating"`
}

const (
	versionTLS13        uint16 = 0x0304
	versionTLS13Draft18        = 0x7f00 | 18
	versionTLS13Draft21        = 0x7f00 | 21
	versionTLS13Draft22        = 0x7f00 | 22
	versionTLS13Draft23        = 0x7f00 | 23
	versionTLS13Draft24        = 0x7f00 | 24
	versionTLS13Draft25        = 0x7f00 | 25
	versionTLS13Draft26        = 0x7f00 | 26
	versionTLS13Draft27        = 0x7f00 | 27
	versionTLS13Draft28        = 0x7f00 | 28
	versionTLS13Draft29        = 0x7f00 | 29
	versionTLS13Draft30        = 0x7f00 | 30
	versionTLS13Draft31        = 0x7f00 | 31
	versionTLS13Draft32        = 0x7f00 | 32
	versionTLS13Draft33        = 0x7f00 | 33
)

var actualSupportedVersions = map[uint16]string{
	tls.VersionSSL30:    "SSL 3.0",
	tls.VersionTLS10:    "TLS 1.0",
	tls.VersionTLS11:    "TLS 1.1",
	tls.VersionTLS12:    "TLS 1.2",
	versionTLS13:        "TLS 1.3", // TODO(#119): use crypto/tls's constant when it has it
	versionTLS13Draft18: "TLS 1.3",
	versionTLS13Draft21: "TLS 1.3",
	versionTLS13Draft22: "TLS 1.3",
	versionTLS13Draft23: "TLS 1.3",
	versionTLS13Draft24: "TLS 1.3",
	versionTLS13Draft25: "TLS 1.3",
	versionTLS13Draft26: "TLS 1.3",
	versionTLS13Draft27: "TLS 1.3",
	versionTLS13Draft28: "TLS 1.3",
	versionTLS13Draft29: "TLS 1.3",
	versionTLS13Draft30: "TLS 1.3",
	versionTLS13Draft31: "TLS 1.3",
	versionTLS13Draft32: "TLS 1.3",
	versionTLS13Draft33: "TLS 1.3",
}

func pullClientInfo(c *conn) *clientInfo {
	d := &clientInfo{InsecureCipherSuites: make(map[string][]string)}

	st := c.ConnectionState()
	if !st.HandshakeComplete {
		panic("given a TLS conn that has not completed its handshake")
	}
	var sweet32Seen []string
	for _, ci := range st.ClientCipherSuites {
		s, found := allCipherSuites[ci]
		if found {
			if strings.Contains(s, "DHE_") {
				d.EphemeralKeysSupported = true
			}
			if cbcSuites[ci] && st.Version <= tls.VersionTLS10 {
				d.BEASTVuln = !st.NMinusOneRecordSplittingDetected
				d.AbleToDetectNMinusOneSplitting = st.AbleToDetectNMinusOneSplitting
			}
			if fewBitCipherSuites[s] {
				d.InsecureCipherSuites[s] = append(d.InsecureCipherSuites[s], fewBitReason)
			}
			if nullCipherSuites[s] {
				d.InsecureCipherSuites[s] = append(d.InsecureCipherSuites[s], nullReason)
			}
			if nullAuthCipherSuites[s] {
				d.InsecureCipherSuites[s] = append(d.InsecureCipherSuites[s], nullAuthReason)
			}
			if rc4CipherSuites[s] {
				d.InsecureCipherSuites[s] = append(d.InsecureCipherSuites[s], rc4Reason)
			}
			if sweet32CipherSuites[s] {
				sweet32Seen = append(sweet32Seen, s)
			} else if len(sweet32Seen) != 0 && !metaCipherSuites[ci] && !tls13Suites[ci] {
				for _, seen := range sweet32Seen {
					d.InsecureCipherSuites[seen] = append(d.InsecureCipherSuites[seen], sweet32Reason)
				}
				sweet32Seen = []string{}
			}
		} else {
			w, found := weirdNSSSuites[ci]
			if !found {
				d.UnknownCipherSuiteSupported = true
				s = fmt.Sprintf("Some unknown cipher suite: %#04x", ci)
			} else {
				s = w
				d.InsecureCipherSuites[s] = append(d.InsecureCipherSuites[s], weirdNSSReason)
			}
		}
		d.GivenCipherSuites = append(d.GivenCipherSuites, s)
	}
	d.SessionTicketsSupported = st.SessionTicketsSupported

	for _, cm := range st.CompressionMethods {
		if cm != 0x0 {
			d.TLSCompressionSupported = true
			break
		}
	}
	vers := st.Version
	d.TLSVersion = actualSupportedVersions[vers]

	// Check TLS 1.3's supported_versions extension for the actual TLS version
	// if it was passed in.
	for _, v := range st.SupportedVersions {
		maybeStr, found := actualSupportedVersions[v]
		if found && v > vers {
			vers = v
			d.TLSVersion = maybeStr
		}
	}
	if d.TLSVersion == "" {
		d.TLSVersion = "an unknown version of SSL/TLS"
	}

	d.Rating = okay

	if !d.EphemeralKeysSupported || vers == tls.VersionTLS11 {
		d.Rating = improvable
	}

	if d.TLSCompressionSupported ||
		d.UnknownCipherSuiteSupported ||
		d.BEASTVuln ||
		len(d.InsecureCipherSuites) != 0 ||
		vers <= tls.VersionTLS10 {
		d.Rating = bad
	}
	return d
}