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scanner.go
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scanner.go
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package main
import (
"compress/gzip"
"fmt"
"io/ioutil"
"net/http"
"net/url"
"strings"
"sync"
"github.com/bitly/go-simplejson"
)
var (
googleHeaders = map[string]string{
"User-Agent": "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.62 Safari/537.36",
"Accept": "application/json, text/plain, */*",
"Accept-Language": "en-US,en;q=0.5",
"Accept-Encoding": "gzip, deflate, br",
"Referer": "https://transparencyreport.google.com",
"Sec-Fetch-Site": "same-origin",
"Sec-Fetch-Mode": "cors",
"Sec-Fetch-Dest": "empty",
"Connection": "keep-alive",
"DNT": "1",
}
)
// A Scanner processes a stream of domain names, looking them up in Google's
// certificate transparency system. One scanner can process many domains in
// parallel.
type Scanner struct {
client *http.Client
maxPages int
lock *sync.Mutex
scanned map[string]struct{}
in chan string
out chan Record
}
// ScanStream loops over a channel of domain strings, scans them, and writes
// records to an output stream.
func (s Scanner) ScanStream() error {
for domain := range s.in {
domain = normalizeDomain(domain)
s.lock.Lock()
if _, present := s.scanned[domain]; present {
// This domain has already been seen. Skip it
s.lock.Unlock()
continue
}
s.scanned[domain] = struct{}{}
s.lock.Unlock()
if err := s.scan(domain); err != nil {
return err
}
}
return nil
}
// scan a single domain.
func (s Scanner) scan(domain string) error {
token := ""
for i := 0; i < s.maxPages; i++ {
q := url.Values{}
var reqPath string
if token == "" {
// There's no continuation token. This is the first request
reqPath = "/transparencyreport/api/v3/httpsreport/ct/certsearch"
q.Set("include_subdomains", "true")
q.Set("domain", domain)
} else {
// Continue retrieving pages of results
reqPath = "/transparencyreport/api/v3/httpsreport/ct/certsearch/page"
q.Set("p", token)
}
u := &url.URL{
Scheme: "https",
Host: "transparencyreport.google.com",
Path: reqPath,
RawQuery: q.Encode(),
}
req, err := http.NewRequest(
http.MethodGet,
u.String(),
nil,
)
if err != nil {
return fmt.Errorf("creating request: %w", err)
}
setGoogleHeaders(req)
resp, err := s.client.Do(req)
if err != nil {
return fmt.Errorf("sending request: %w", err)
}
if resp.StatusCode < 200 || resp.StatusCode > 299 {
return fmt.Errorf("non-200 response %d: %s", resp.StatusCode, resp.Status)
}
r := resp.Body
if resp.Header.Get("Content-Encoding") == "gzip" {
r, err = gzip.NewReader(r)
if err != nil {
return fmt.Errorf("creating gzip reader: %w", err)
}
}
b, err := ioutil.ReadAll(r)
if err != nil {
return fmt.Errorf("reading response body: %w", err)
}
resp.Body.Close()
if string(b[:4]) == ")]}'" {
// To prevent XSSI, a prefix is added that needs to be stripped
b = b[4:]
}
records, newToken, err := parseCTData(b)
if err != nil {
return fmt.Errorf("parsing CT data: %w", err)
}
for _, record := range records {
// mark each record with which domain it came from and send it
record.From = domain
s.out <- record
}
if newToken == "" {
// no continuation token, this domain is done
break
}
token = newToken
}
return nil
}
// normalizeDomain tries to normalize domain name strings, with room to grow.
func normalizeDomain(d string) string {
return strings.TrimSpace(d)
}
// setGoogleHeaders applies the headers google expets to a request
func setGoogleHeaders(req *http.Request) {
for h, v := range googleHeaders {
req.Header.Set(h, v)
}
}
// A Record captures information about a domain from certificate transparency
// and subsequent DNS resolution
type Record struct {
From string
Name string
Issuer string
NotBeforeTime int64
NotAfterTime int64
Addrs []string
Err error
}
/*
[
[
"https.ct.cdsr",
[
[
null,
"debug.example.org",
"Let's Encrypt Authority X3",
1605043123456,
1612819123456,
"<base64>",
2,
null,
1
],
[
null,
"debug.example.org",
"Let's Encrypt Authority X3",
1605043123456,
1612819123456,
"<base64>",
2,
null,
1
]
],
[
[
"1234567890193923849",
null,
"C=US, O=Let's Encrypt, CN=R3",
6
],
[
"9328174140391839128",
null,
"C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3",
44
]
],
[
null,
"<base64>",
null,
1,
5
]
]
]
*/
// parseCTData parses a page of certificate transparency data from a goolge
// response. The JSON returned is all nested arrays instead of having a
// sensible object structure.
func parseCTData(b []byte) ([]Record, string, error) {
j, err := simplejson.NewJson(b)
if err != nil {
return nil, "", fmt.Errorf("parsing JSON: %w", err)
}
recordsJSON := j.GetIndex(0).GetIndex(1)
recordsArray, err := recordsJSON.Array()
if err != nil {
return nil, "", fmt.Errorf("records not an array")
}
lenRecords := len(recordsArray)
records := make([]Record, lenRecords)
for i := 0; i < lenRecords; i++ {
currentRecord := recordsJSON.GetIndex(i)
records[i] = Record{
Name: currentRecord.GetIndex(1).MustString(),
Issuer: currentRecord.GetIndex(2).MustString(),
NotBeforeTime: currentRecord.GetIndex(3).MustInt64(),
NotAfterTime: currentRecord.GetIndex(4).MustInt64(),
}
}
token := j.GetIndex(0).GetIndex(3).GetIndex(1).MustString()
return records, token, nil
}
// getGoogleCookie retrieves a cookie uses for subsequent CT scan requests.
// The cookie only needs to be fetched once. The tool doesn't monitor cookie
// expiration.
func getGoogleCookie(client *http.Client) error {
if client.Jar == nil {
return fmt.Errorf("no cookie jar set")
}
req, err := http.NewRequest(
http.MethodGet,
"https://transparencyreport.google.com/https/certificates?hl=en_GB",
nil,
)
if err != nil {
return fmt.Errorf("creating request: %w", err)
}
setGoogleHeaders(req)
resp, err := client.Do(req)
if err != nil {
return fmt.Errorf("sending request: %w", err)
}
if resp.StatusCode < 200 || resp.StatusCode > 299 {
return fmt.Errorf("non-200 response %d: %s", resp.StatusCode, resp.Status)
}
return nil
}