Verify STH signatures

cmd/common.go

@@ -7,7 +7,7 @@ import (
 	"os"
 	"bytes"
 	"os/user"
-	"bufio"
+	"encoding/json"
 	"sync"
 	"strings"
 	"path/filepath"
@@ -20,7 +20,8 @@ var batchSize = flag.Int("batch_size", 1000, "Max number of entries to request a
 var numWorkers = flag.Int("num_workers", 2, "Number of concurrent matchers")
 var parallelFetch = flag.Int("parallel_fetch", 2, "Number of concurrent GetEntries fetches")
 var script = flag.String("script", "", "Script to execute when a matching certificate is found")
-var logsFilename = flag.String("logs", "", "File containing log URLs")
+var logsFilename = flag.String("logs", "", "JSON file containing log URLs")
+var underwater = flag.Bool("underwater", false, "Monitor certificates from distrusted CAs")
 var noSave = flag.Bool("no_save", false, "Do not save a copy of matching certificates")
 var verbose = flag.Bool("verbose", false, "Be verbose")
 var allTime = flag.Bool("all_time", false, "Scan certs from all time, not just since last scan")
@@ -28,19 +29,6 @@ var stateDir string
 
 var printMutex sync.Mutex
 
-var defaultLogs = []string{
-	"https://log.certly.io",
-	"https://ct1.digicert-ct.com/log",
-	"https://ct.googleapis.com/aviator",
-	"https://ct.googleapis.com/pilot",
-	"https://ct.googleapis.com/rocketeer",
-	"https://ct.izenpe.com",
-	"https://ct.ws.symantec.com",
-	"https://vega.ws.symantec.com",
-	"https://ctlog.api.venafi.com",
-	"https://ct.wosign.com",
-}
-
 func isRoot () bool {
 	return os.Geteuid() == 0
 }
@@ -97,7 +85,7 @@ func defangLogUri (logUri string) string {
 func Main (argStateDir string, processCallback ctwatch.ProcessCallback) {
 	stateDir = argStateDir
 
-	var logs []string
+	var logs []ctwatch.LogInfo
 	if *logsFilename != "" {
 		logFile, err := os.Open(*logsFilename)
 		if err != nil {
@@ -105,16 +93,16 @@ func Main (argStateDir string, processCallback ctwatch.ProcessCallback) {
 			os.Exit(3)
 		}
 		defer logFile.Close()
-		scanner := bufio.NewScanner(logFile)
+		var logFileObj ctwatch.LogInfoFile
-		for scanner.Scan() {
+		if err := json.NewDecoder(logFile).Decode(&logFileObj); err != nil {
-			logs = append(logs, scanner.Text())
+			fmt.Fprintf(os.Stderr, "%s: Error decoding logs file: %s: %s\n", os.Args[0], *logsFilename, err)
-		}
-		if err := scanner.Err(); err != nil {
-			fmt.Fprintf(os.Stderr, "%s: Error reading logs file: %s: %s\n", os.Args[0], *logsFilename, err)
 			os.Exit(3)
 		}
+		logs = logFileObj.Logs
+	} else if *underwater {
+		logs = ctwatch.UnderwaterLogs
 	} else {
-		logs = defaultLogs
+		logs = ctwatch.DefaultLogs
 	}
 
 	if err := os.Mkdir(stateDir, 0777); err != nil && !os.IsExist(err) {
@@ -131,7 +119,13 @@ func Main (argStateDir string, processCallback ctwatch.ProcessCallback) {
 
 	exitCode := 0
 
-	for _, logUri := range logs {
+	for _, logInfo := range logs {
+		logUri := logInfo.FullURI()
+		logKey, err := logInfo.ParsedPublicKey()
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%s: %s: Bad public key: %s\n", os.Args[0], logUri, err)
+			os.Exit(3)
+		}
 		stateFilename := filepath.Join(stateDir, "sths", defangLogUri(logUri))
 		prevSTH, err := ctwatch.ReadStateFile(stateFilename)
 		if err != nil {
@@ -146,7 +140,7 @@ func Main (argStateDir string, processCallback ctwatch.ProcessCallback) {
 			ParallelFetch: *parallelFetch,
 			Quiet:         !*verbose,
 		}
-		scanner := ctwatch.NewScanner(logUri, logClient, opts)
+		scanner := ctwatch.NewScanner(logUri, logKey, logClient, opts)
 
 		latestSTH, err := scanner.GetSTH()
 		if err != nil {

logs.go

@@ -0,0 +1,106 @@
+package ctwatch
+
+import (
+	"encoding/base64"
+	"crypto"
+	"crypto/x509"
+)
+
+type LogInfoFile struct {
+	Logs		[]LogInfo	`json:"logs"`
+}
+type LogInfo struct {
+	Description	string		`json:"description"`
+	Key		[]byte		`json:"key"`
+	Url		string		`json:"url"`
+	MMD		int		`json:"maximum_merge_delay"`
+}
+
+func (info *LogInfo) FullURI () string {
+	return "https://" + info.Url
+}
+
+func (info *LogInfo) ParsedPublicKey () (crypto.PublicKey, error) {
+	return x509.ParsePKIXPublicKey(info.Key)
+}
+
+var DefaultLogs = []LogInfo{
+	{
+		Description: "Google 'Pilot' log",
+		Key: mustDecodeBase64("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEfahLEimAoz2t01p3uMziiLOl/fHTDM0YDOhBRuiBARsV4UvxG2LdNgoIGLrtCzWE0J5APC2em4JlvR8EEEFMoA=="),
+		Url: "ct.googleapis.com/pilot",
+		MMD: 86400,
+	},
+	{
+		Description: "Google 'Aviator' log",
+		Key: mustDecodeBase64("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE1/TMabLkDpCjiupacAlP7xNi0I1JYP8bQFAHDG1xhtolSY1l4QgNRzRrvSe8liE+NPWHdjGxfx3JhTsN9x8/6Q=="),
+		Url: "ct.googleapis.com/aviator",
+		MMD: 86400,
+	},
+	{
+		Description: "DigiCert Log Server",
+		Key: mustDecodeBase64("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEAkbFvhu7gkAW6MHSrBlpE1n4+HCFRkC5OLAjgqhkTH+/uzSfSl8ois8ZxAD2NgaTZe1M9akhYlrYkes4JECs6A=="),
+		Url: "ct1.digicert-ct.com/log",
+		MMD: 86400,
+	},
+	{
+		Description: "Google 'Rocketeer' log",
+		Key: mustDecodeBase64("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEIFsYyDzBi7MxCAC/oJBXK7dHjG+1aLCOkHjpoHPqTyghLpzA9BYbqvnV16mAw04vUjyYASVGJCUoI3ctBcJAeg=="),
+		Url: "ct.googleapis.com/rocketeer",
+		MMD: 86400,
+	},
+	{
+		Description: "Certly.IO log",
+		Key: mustDecodeBase64("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAECyPLhWKYYUgEc+tUXfPQB4wtGS2MNvXrjwFCCnyYJifBtd2Sk7Cu+Js9DNhMTh35FftHaHu6ZrclnNBKwmbbSA=="),
+		Url: "log.certly.io",
+		MMD: 86400,
+	},
+	{
+		Description: "Izenpe log",
+		Key: mustDecodeBase64("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEJ2Q5DC3cUBj4IQCiDu0s6j51up+TZAkAEcQRF6tczw90rLWXkJMAW7jr9yc92bIKgV8vDXU4lDeZHvYHduDuvg=="),
+		Url: "ct.izenpe.com",
+		MMD: 86400,
+	},
+	{
+		Description: "Symantec log",
+		Key: mustDecodeBase64("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEluqsHEYMG1XcDfy1lCdGV0JwOmkY4r87xNuroPS2bMBTP01CEDPwWJePa75y9CrsHEKqAy8afig1dpkIPSEUhg=="),
+		Url: "ct.ws.symantec.com",
+		MMD: 86400,
+	},
+	{
+		Description: "Venafi log",
+		Key: mustDecodeBase64("MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAolpIHxdSlTXLo1s6H1OCdpSj/4DyHDc8wLG9wVmLqy1lk9fz4ATVmm+/1iN2Nk8jmctUKK2MFUtlWXZBSpym97M7frGlSaQXUWyA3CqQUEuIJOmlEjKTBEiQAvpfDjCHjlV2Be4qTM6jamkJbiWtgnYPhJL6ONaGTiSPm7Byy57iaz/hbckldSOIoRhYBiMzeNoA0DiRZ9KmfSeXZ1rB8y8X5urSW+iBzf2SaOfzBvDpcoTuAaWx2DPazoOl28fP1hZ+kHUYvxbcMjttjauCFx+JII0dmuZNIwjfeG/GBb9frpSX219k1O4Wi6OEbHEr8at/XQ0y7gTikOxBn/s5wQIDAQAB"),
+		Url: "ctlog.api.venafi.com",
+		MMD: 86400,
+	},
+	{
+		Description: "Symantec 'Vega' log",
+		Key: mustDecodeBase64("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE6pWeAv/u8TNtS4e8zf0ZF2L/lNPQWQc/Ai0ckP7IRzA78d0NuBEMXR2G3avTK0Zm+25ltzv9WWis36b4ztIYTQ=="),
+		Url: "vega.ws.symantec.com",
+		MMD: 86400,
+	},
+	{
+		Description: "WoSign CT Log Server",
+		Key: mustDecodeBase64("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE1+wvK3VPN7yjQ7qLZWY8fWrlDCqmwuUm/gx9TnzwOrzi0yLcAdAfbkOcXG6DrZwV9sSNYLUdu6NiaX7rp6oBmw=="),
+		Url: "ct.wosign.com",
+		MMD: 86400,
+	},
+}
+
+// Logs which monitor certs from distrusted roots
+var UnderwaterLogs = []LogInfo{
+	{
+		Description: "Google 'Submariner' log",
+		Key: mustDecodeBase64("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEOfifIGLUV1Voou9JLfA5LZreRLSUMOCeeic8q3Dw0fpRkGMWV0Gtq20fgHQweQJeLVmEByQj9p81uIW4QkWkTw=="),
+		Url: "ct.googleapis.com/submariner",
+		MMD: 86400,
+	},
+}
+
+func mustDecodeBase64 (str string) []byte {
+	bytes, err := base64.StdEncoding.DecodeString(str)
+	if err != nil {
+		panic("MustDecodeBase64: " + err.Error())
+	}
+	return bytes
+}

scanner.go

@@ -7,6 +7,8 @@ import (
 	"sync"
 	"sync/atomic"
 	"time"
+	"crypto"
+	"errors"
 
 	"github.com/google/certificate-transparency/go"
 	"github.com/google/certificate-transparency/go/client"
@@ -44,6 +46,9 @@ type Scanner struct {
 	// Base URI of CT log
 	LogUri				string
 
+	// Public key of the log
+	publicKey			crypto.PublicKey
+
 	// Client used to talk to the CT log instance
 	logClient			*client.LogClient
 
@@ -168,7 +173,15 @@ func (s *Scanner) GetSTH() (*ct.SignedTreeHead, error) {
 	if err != nil {
 		return nil, err
 	}
-	// TODO: Verify STH signature
+	if s.publicKey != nil {
+		verifier, err := ct.NewSignatureVerifier(s.publicKey)
+		if err != nil {
+			return nil, err
+		}
+		if err := verifier.VerifySTHSignature(*latestSth); err != nil {
+			return nil, errors.New("STH signature is invalid: " + err.Error())
+		}
+	}
 	return latestSth, nil
 }
 
@@ -255,9 +268,10 @@ func (s *Scanner) Scan(startIndex int64, endIndex int64, processCert ProcessCall
 
 // Creates a new Scanner instance using |client| to talk to the log, and taking
 // configuration options from |opts|.
-func NewScanner(logUri string, client *client.LogClient, opts ScannerOptions) *Scanner {
+func NewScanner(logUri string, publicKey crypto.PublicKey, client *client.LogClient, opts ScannerOptions) *Scanner {
 	var scanner Scanner
 	scanner.LogUri = logUri
+	scanner.publicKey = publicKey
 	scanner.logClient = client
 	scanner.opts = opts
 	return &scanner