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scanner.go
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scanner.go
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// Copyright 2014 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package scanner holds code for iterating through the contents of a CT log.
package scanner
import (
"container/list"
"fmt"
"log"
"math/big"
"regexp"
"sync"
"sync/atomic"
"time"
ct "github.com/google/certificate-transparency-go"
"github.com/google/certificate-transparency-go/client"
"github.com/google/certificate-transparency-go/x509"
"golang.org/x/net/context"
)
// Matcher describes how to match certificates and precertificates; clients should implement this interface
// to perform their own match criteria.
type Matcher interface {
// CertificateMatches is called by the scanner for each X509 Certificate found in the log.
// The implementation should return true if the passed Certificate is interesting, and false otherwise.
CertificateMatches(*x509.Certificate) bool
// PrecertificateMatches is called by the scanner for each CT Precertificate found in the log.
// The implementation should return true if the passed Precertificate is interesting, and false otherwise.
PrecertificateMatches(*ct.Precertificate) bool
}
// MatchAll is a Matcher which will match every possible Certificate and Precertificate.
type MatchAll struct{}
// CertificateMatches returns true if the given cert should match; in this case, always.
func (m MatchAll) CertificateMatches(_ *x509.Certificate) bool {
return true
}
// PrecertificateMatches returns true if the given precert should match, in this case, always.
func (m MatchAll) PrecertificateMatches(_ *ct.Precertificate) bool {
return true
}
// MatchNone is a Matcher which will never match any Certificate or Precertificate.
type MatchNone struct{}
// CertificateMatches returns true if the given cert should match; in this case, never.
func (m MatchNone) CertificateMatches(_ *x509.Certificate) bool {
return false
}
// PrecertificateMatches returns true if the given cert should match; in this case, never.
func (m MatchNone) PrecertificateMatches(_ *ct.Precertificate) bool {
return false
}
// MatchSerialNumber performs a match for a specific serial number.
type MatchSerialNumber struct {
SerialNumber big.Int
}
// CertificateMatches returns true if the given cert should match; in this
// case, only if the serial number matches.
func (m MatchSerialNumber) CertificateMatches(c *x509.Certificate) bool {
return c.SerialNumber.String() == m.SerialNumber.String()
}
// PrecertificateMatches returns true if the given cert should match; in this
// case, only if the serial number matches.
func (m MatchSerialNumber) PrecertificateMatches(p *ct.Precertificate) bool {
return p.TBSCertificate.SerialNumber.String() == m.SerialNumber.String()
}
// MatchSubjectRegex is a Matcher which will use CertificateSubjectRegex and PrecertificateSubjectRegex
// to determine whether Certificates and Precertificates are interesting.
// The two regexes are tested against Subject CN (Common Name) as well as all
// Subject Alternative Names
type MatchSubjectRegex struct {
CertificateSubjectRegex *regexp.Regexp
PrecertificateSubjectRegex *regexp.Regexp
}
// CertificateMatches returns true if either CN or any SAN of c matches m.CertificateSubjectRegex.
func (m MatchSubjectRegex) CertificateMatches(c *x509.Certificate) bool {
if m.CertificateSubjectRegex.FindStringIndex(c.Subject.CommonName) != nil {
return true
}
for _, alt := range c.DNSNames {
if m.CertificateSubjectRegex.FindStringIndex(alt) != nil {
return true
}
}
return false
}
// PrecertificateMatches returns true if either CN or any SAN of p matches m.PrecertificateSubjectRegex.
func (m MatchSubjectRegex) PrecertificateMatches(p *ct.Precertificate) bool {
if m.PrecertificateSubjectRegex.FindStringIndex(p.TBSCertificate.Subject.CommonName) != nil {
return true
}
for _, alt := range p.TBSCertificate.DNSNames {
if m.PrecertificateSubjectRegex.FindStringIndex(alt) != nil {
return true
}
}
return false
}
// MatchIssuerRegex matches on issuer CN (common name) by regex
type MatchIssuerRegex struct {
CertificateIssuerRegex *regexp.Regexp
PrecertificateIssuerRegex *regexp.Regexp
}
// CertificateMatches returns true if the given cert's CN matches.
func (m MatchIssuerRegex) CertificateMatches(c *x509.Certificate) bool {
return m.CertificateIssuerRegex.FindStringIndex(c.Issuer.CommonName) != nil
}
// PrecertificateMatches returns true if the given precert's CN matches.
func (m MatchIssuerRegex) PrecertificateMatches(p *ct.Precertificate) bool {
return m.PrecertificateIssuerRegex.FindStringIndex(p.TBSCertificate.Issuer.CommonName) != nil
}
// ScannerOptions holds configuration options for the Scanner
type ScannerOptions struct {
// Custom matcher for x509 Certificates, functor will be called for each
// Certificate found during scanning.
Matcher Matcher
// Match precerts only (Matcher still applies to precerts)
PrecertOnly bool
// Number of entries to request in one batch from the Log
BatchSize int
// Number of concurrent matchers to run
NumWorkers int
// Number of concurrent fethers to run
ParallelFetch int
// Log entry index to start fetching & matching at
StartIndex int64
// Don't print any status messages to stdout
Quiet bool
}
// DefaultScannerOptions creates a new ScannerOptions struct with sensible defaults.
func DefaultScannerOptions() *ScannerOptions {
return &ScannerOptions{
Matcher: &MatchAll{},
PrecertOnly: false,
BatchSize: 1000,
NumWorkers: 1,
ParallelFetch: 1,
StartIndex: 0,
Quiet: false,
}
}
// Scanner is a tool to scan all the entries in a CT Log.
type Scanner struct {
// Client used to talk to the CT log instance
logClient *client.LogClient
// Configuration options for this Scanner instance
opts ScannerOptions
// Counter of the number of certificates scanned
certsProcessed int64
// Counter of the number of precertificates encountered during the scan.
precertsSeen int64
unparsableEntries int64
entriesWithNonFatalErrors int64
Log func(msg string)
}
// matcherJob represents the context for an individual matcher job.
type matcherJob struct {
// The log entry returned by the log server
entry ct.LogEntry
// The index of the entry containing the LeafInput in the log
index int64
}
// fetchRange represents a range of certs to fetch from a CT log
type fetchRange struct {
start int64
end int64
}
// Takes the error returned by either x509.ParseCertificate() or
// x509.ParseTBSCertificate() and determines if it's non-fatal or otherwise.
// In the case of non-fatal errors, the error will be logged,
// entriesWithNonFatalErrors will be incremented, and the return value will be
// nil.
// Fatal errors will be logged, unparsableEntires will be incremented, and the
// fatal error itself will be returned.
// When err is nil, this method does nothing.
func (s *Scanner) handleParseEntryError(err error, entryType ct.LogEntryType, index int64) error {
if err == nil {
// No error to handle
return nil
}
switch err.(type) {
case x509.NonFatalErrors:
atomic.AddInt64(&s.entriesWithNonFatalErrors, 1)
// We'll make a note, but continue.
s.Log(fmt.Sprintf("Non-fatal error in %+v at index %d: %s", entryType, index, err.Error()))
default:
atomic.AddInt64(&s.unparsableEntries, 1)
s.Log(fmt.Sprintf("Failed to parse in %+v at index %d : %s", entryType, index, err.Error()))
return err
}
return nil
}
// Processes the given entry in the specified log.
func (s *Scanner) processEntry(entry ct.LogEntry, foundCert func(*ct.LogEntry), foundPrecert func(*ct.LogEntry)) {
atomic.AddInt64(&s.certsProcessed, 1)
switch entry.Leaf.TimestampedEntry.EntryType {
case ct.X509LogEntryType:
if s.opts.PrecertOnly {
// Only interested in precerts and this is an X.509 cert, early-out.
return
}
cert, err := x509.ParseCertificate(entry.Leaf.TimestampedEntry.X509Entry.Data)
if err = s.handleParseEntryError(err, entry.Leaf.TimestampedEntry.EntryType, entry.Index); err != nil {
// We hit an unparseable entry, already logged inside handleParseEntryError()
return
}
if s.opts.Matcher.CertificateMatches(cert) {
entry.X509Cert = cert
foundCert(&entry)
}
case ct.PrecertLogEntryType:
c, err := x509.ParseTBSCertificate(entry.Leaf.TimestampedEntry.PrecertEntry.TBSCertificate)
if err = s.handleParseEntryError(err, entry.Leaf.TimestampedEntry.EntryType, entry.Index); err != nil {
// We hit an unparseable entry, already logged inside handleParseEntryError()
return
}
precert := &ct.Precertificate{
Raw: entry.Chain[0].Data,
TBSCertificate: *c,
IssuerKeyHash: entry.Leaf.TimestampedEntry.PrecertEntry.IssuerKeyHash}
if s.opts.Matcher.PrecertificateMatches(precert) {
entry.Precert = precert
foundPrecert(&entry)
}
atomic.AddInt64(&s.precertsSeen, 1)
}
}
// Worker function to match certs.
// Accepts MatcherJobs over the entries channel, and processes them.
// Returns true over the done channel when the entries channel is closed.
func (s *Scanner) matcherJob(id int, entries <-chan matcherJob, foundCert func(*ct.LogEntry), foundPrecert func(*ct.LogEntry), wg *sync.WaitGroup) {
for e := range entries {
s.processEntry(e.entry, foundCert, foundPrecert)
}
s.Log(fmt.Sprintf("Matcher %d finished", id))
wg.Done()
}
// Worker function for fetcher jobs.
// Accepts cert ranges to fetch over the ranges channel, and if the fetch is
// successful sends the individual LeafInputs out (as MatcherJobs) into the
// entries channel for the matchers to chew on.
// Will retry failed attempts to retrieve ranges indefinitely.
// Sends true over the done channel when the ranges channel is closed.
func (s *Scanner) fetcherJob(id int, ranges <-chan fetchRange, entries chan<- matcherJob, wg *sync.WaitGroup) {
for r := range ranges {
success := false
// TODO(alcutter): give up after a while:
for !success {
logEntries, err := s.logClient.GetEntries(context.TODO(), r.start, r.end)
if err != nil {
s.Log(fmt.Sprintf("Problem fetching from log: %s", err.Error()))
continue
}
for _, logEntry := range logEntries {
logEntry.Index = r.start
entries <- matcherJob{logEntry, r.start}
r.start++
}
if r.start > r.end {
// Only complete if we actually got all the leaves we were
// expecting -- Logs MAY return fewer than the number of
// leaves requested.
success = true
}
}
}
s.Log(fmt.Sprintf("Fetcher %d finished", id))
wg.Done()
}
func min(a int64, b int64) int64 {
if a < b {
return a
}
return b
}
func max(a int64, b int64) int64 {
if a > b {
return a
}
return b
}
// Pretty prints the passed in number of seconds into a more human readable
// string.
func humanTime(seconds int) string {
nanos := time.Duration(seconds) * time.Second
hours := int(nanos / (time.Hour))
nanos %= time.Hour
minutes := int(nanos / time.Minute)
nanos %= time.Minute
seconds = int(nanos / time.Second)
s := ""
if hours > 0 {
s += fmt.Sprintf("%d hours ", hours)
}
if minutes > 0 {
s += fmt.Sprintf("%d minutes ", minutes)
}
if seconds > 0 {
s += fmt.Sprintf("%d seconds ", seconds)
}
return s
}
// Scan performs a scan against the Log.
// For each x509 certificate found, foundCert will be called with the
// index of the entry and certificate itself as arguments. For each precert
// found, foundPrecert will be called with the index of the entry and the raw
// precert string as the arguments.
//
// This method blocks until the scan is complete.
func (s *Scanner) Scan(foundCert func(*ct.LogEntry),
foundPrecert func(*ct.LogEntry)) error {
s.Log("Starting up...\n")
s.certsProcessed = 0
s.precertsSeen = 0
s.unparsableEntries = 0
s.entriesWithNonFatalErrors = 0
latestSth, err := s.logClient.GetSTH(context.Background())
if err != nil {
return err
}
s.Log(fmt.Sprintf("Got STH with %d certs", latestSth.TreeSize))
ticker := time.NewTicker(time.Second)
startTime := time.Now()
fetches := make(chan fetchRange, 1000)
jobs := make(chan matcherJob, 100000)
go func() {
for range ticker.C {
certsProcessed := atomic.LoadInt64(&s.certsProcessed)
throughput := float64(certsProcessed) / time.Since(startTime).Seconds()
remainingCerts := int64(latestSth.TreeSize) - int64(s.opts.StartIndex) - certsProcessed
remainingSeconds := int(float64(remainingCerts) / throughput)
remainingString := humanTime(remainingSeconds)
s.Log(fmt.Sprintf("Processed: %d certs (to index %d). Throughput: %3.2f ETA: %s\n", certsProcessed,
s.opts.StartIndex+int64(certsProcessed), throughput, remainingString))
}
}()
var ranges list.List
for start := s.opts.StartIndex; start < int64(latestSth.TreeSize); {
end := min(start+int64(s.opts.BatchSize), int64(latestSth.TreeSize)) - 1
ranges.PushBack(fetchRange{start, end})
start = end + 1
}
var fetcherWG sync.WaitGroup
var matcherWG sync.WaitGroup
// Start matcher workers
for w := 0; w < s.opts.NumWorkers; w++ {
matcherWG.Add(1)
go s.matcherJob(w, jobs, foundCert, foundPrecert, &matcherWG)
}
// Start fetcher workers
for w := 0; w < s.opts.ParallelFetch; w++ {
fetcherWG.Add(1)
go s.fetcherJob(w, fetches, jobs, &fetcherWG)
}
for r := ranges.Front(); r != nil; r = r.Next() {
fetches <- r.Value.(fetchRange)
}
close(fetches)
fetcherWG.Wait()
close(jobs)
matcherWG.Wait()
s.Log(fmt.Sprintf("Completed %d certs in %s", atomic.LoadInt64(&s.certsProcessed), humanTime(int(time.Since(startTime).Seconds()))))
s.Log(fmt.Sprintf("Saw %d precerts", atomic.LoadInt64(&s.precertsSeen)))
s.Log(fmt.Sprintf("%d unparsable entries, %d non-fatal errors", atomic.LoadInt64(&s.unparsableEntries), atomic.LoadInt64(&s.entriesWithNonFatalErrors)))
return nil
}
// NewScanner creates a new Scanner instance using client to talk to the log,
// taking configuration options from opts.
func NewScanner(client *client.LogClient, opts ScannerOptions) *Scanner {
var scanner Scanner
scanner.logClient = client
// Set a default match-everything regex if none was provided:
if opts.Matcher == nil {
opts.Matcher = &MatchAll{}
}
if opts.Quiet {
scanner.Log = func(msg string) {}
} else {
scanner.Log = func(msg string) { log.Print(msg) }
}
scanner.opts = opts
return &scanner
}