verify.go

   1 /*
   2 Copyright (C) 2021 Sergey Matveev <stargrave@stargrave.org>
   3
   4 This program is free software: you can redistribute it and/or modify
   5 it under the terms of the GNU General Public License as published by
   6 the Free Software Foundation, version 3 of the License.
   7
   8 This program is distributed in the hope that it will be useful,
   9 but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 GNU General Public License for more details.
  12
  13 You should have received a copy of the GNU General Public License
  14 along with this program.  If not, see <http://www.gnu.org/licenses/>.
  15 */
  16
  17 package main
  18
  19 import (
  20         "bytes"
  21         "crypto/sha256"
  22         "crypto/x509"
  23         "encoding/hex"
  24         "encoding/pem"
  25         "fmt"
  26         "log"
  27         "os"
  28         "os/exec"
  29         "path/filepath"
  30         "strings"
  31         "sync"
  32
  33         "go.cypherpunks.ru/ucspi"
  34 )
  35
  36 var (
  37         CmdCerttool = "certtool"
  38         CmdWish     = "wish8.7"
  39
  40         certs     *string
  41         accepted  = make(map[string]string)
  42         acceptedM sync.RWMutex
  43         rejected  = make(map[string]string)
  44         rejectedM sync.RWMutex
  45 )
  46
  47 func spkiHash(cert *x509.Certificate) string {
  48         hsh := sha256.Sum256(cert.RawSubjectPublicKeyInfo)
  49         return hex.EncodeToString(hsh[:])
  50 }
  51
  52 func acceptedAdd(addr, h string) {
  53         acceptedM.Lock()
  54         accepted[addr] = h
  55         acceptedM.Unlock()
  56 }
  57
  58 func rejectedAdd(addr, h string) {
  59         rejectedM.Lock()
  60         rejected[addr] = h
  61         rejectedM.Unlock()
  62 }
  63
  64 type ErrRejected struct {
  65         addr string
  66 }
  67
  68 func (err ErrRejected) Error() string { return err.addr + " was rejected" }
  69
  70 func certInfo(certRaw []byte) string {
  71         cmd := exec.Command(CmdCerttool, "--certificate-info", "--inder")
  72         cmd.Stdin = bytes.NewReader(certRaw)
  73         out, err := cmd.Output()
  74         if err != nil {
  75                 return err.Error()
  76         }
  77         lines := make([]string, 0, 128)
  78         for i, line := range strings.Split(string(out), "\n") {
  79                 if strings.Contains(line, "ASCII:") {
  80                         continue
  81                 }
  82                 lines = append(lines, fmt.Sprintf(
  83                         "%03d %s", i, strings.ReplaceAll(line, `"`, `\"`),
  84                 ))
  85         }
  86         return strings.Join(lines, "\n")
  87 }
  88
  89 func verifyCert(
  90         host string,
  91         dialErr error,
  92         rawCerts [][]byte,
  93         verifiedChains [][]*x509.Certificate,
  94 ) error {
  95         var certTheir *x509.Certificate
  96         var err error
  97         if len(verifiedChains) > 0 {
  98                 certTheir = verifiedChains[0][0]
  99         } else {
 100                 certTheir, err = x509.ParseCertificate(rawCerts[0])
 101                 if err != nil {
 102                         return err
 103                 }
 104         }
 105         certTheirHash := spkiHash(certTheir)
 106         acceptedM.RLock()
 107         certOurHash := accepted[host]
 108         acceptedM.RUnlock()
 109         if certTheirHash == certOurHash {
 110                 return nil
 111         }
 112         rejectedM.RLock()
 113         certOurHash = rejected[host]
 114         rejectedM.RUnlock()
 115         if certTheirHash == certOurHash {
 116                 return ErrRejected{host}
 117         }
 118         daneExists, daneMatched := dane(host, certTheir)
 119         if daneExists {
 120                 if daneMatched {
 121                         sinkCert <- fmt.Sprintf("DANE\t%s\tmatched", host)
 122                 } else {
 123                         sinkErr <- fmt.Sprintf("DANE\t%s\tnot matched", host)
 124                 }
 125         }
 126         fn := filepath.Join(*certs, host)
 127         certsOur, _, err := ucspi.CertPoolFromFile(fn)
 128         if err == nil || dialErr != nil || (daneExists && !daneMatched) {
 129                 if certsOur != nil && certTheirHash == spkiHash(certsOur[0]) {
 130                         acceptedAdd(host, certTheirHash)
 131                         if bytes.Compare(certsOur[0].Raw, rawCerts[0]) != 0 {
 132                                 sinkCert <- fmt.Sprintf("Refresh\t%s\t%s", host, certTheirHash)
 133                                 goto CertUpdate
 134                         }
 135                         return nil
 136                 }
 137                 var b bytes.Buffer
 138                 b.WriteString(fmt.Sprintf("wm title . \"%s\"\n", host))
 139
 140                 if dialErr != nil {
 141                         b.WriteString(fmt.Sprintf(`set tErr [text .tErr]
 142 $tErr insert end "%s"
 143 $tErr configure -wrap word -height 5
 144 `, dialErr.Error()))
 145                         b.WriteString("grid .tErr -columnspan 3\n")
 146                 }
 147
 148                 if daneExists {
 149                         if daneMatched {
 150                                 b.WriteString("label .lDANE -bg green -text \"DANE matched\"\n")
 151                         } else {
 152                                 b.WriteString("label .lDANE -bg red -text \"DANE not matched!\"\n")
 153                         }
 154                         b.WriteString("grid .lDANE\n")
 155                 }
 156
 157                 var bCerts bytes.Buffer
 158                 for i, rawCert := range rawCerts {
 159                         bCerts.WriteString(fmt.Sprintf("Their %d:\n", i))
 160                         bCerts.WriteString(certInfo(rawCert))
 161                 }
 162                 b.WriteString(fmt.Sprintf(`set tTheir [text .tTheir]
 163 $tTheir insert end "%s"
 164 set sbTheir [scrollbar .sbTheir -command [list $tTheir yview]]
 165 $tTheir configure -wrap word -yscrollcommand [list $sbTheir set]
 166 `, bCerts.String()))
 167                 b.WriteString("grid $tTheir $sbTheir -sticky nsew -columnspan 3\n")
 168
 169                 if certsOur != nil {
 170                         bCerts.Reset()
 171                         for i, cert := range certsOur {
 172                                 bCerts.WriteString(fmt.Sprintf("Our %d:\n", i))
 173                                 bCerts.WriteString(certInfo(cert.Raw))
 174                         }
 175                         b.WriteString(fmt.Sprintf(`set tOur [text .tOur]
 176 $tOur insert end "%s"
 177 set sbOur [scrollbar .sbOur -command [list $tOur yview]]
 178 $tOur configure -wrap word -yscrollcommand [list $sbOur set]
 179 `, bCerts.String()))
 180                         b.WriteString("grid $tOur $sbOur -sticky nsew -columnspan 3\n")
 181                 }
 182
 183                 b.WriteString(`
 184 proc doAccept {} { exit 10 }
 185 proc doOnce {} { exit 11 }
 186 proc doReject {} { exit 12 }
 187 button .bAccept -text "Accept" -bg green -command doAccept
 188 button .bOnce -text "Once" -command doOnce
 189 button .bReject -text "Reject" -bg red -command doReject
 190 grid .bAccept .bOnce .bReject
 191 grid rowconfigure . 0 -weight 1
 192 grid columnconfigure . 0 -weight 1
 193 `)
 194
 195                 cmd := exec.Command(CmdWish)
 196                 // ioutil.WriteFile("/tmp/w.tcl", b.Bytes(), 0666)
 197                 cmd.Stdin = &b
 198                 err = cmd.Run()
 199                 exitError, ok := err.(*exec.ExitError)
 200                 if !ok {
 201                         sinkCert <- fmt.Sprintf("DENY\t%s\t%s", host, certTheirHash)
 202                         return ErrRejected{host}
 203                 }
 204                 switch exitError.ExitCode() {
 205                 case 10:
 206                         sinkCert <- fmt.Sprintf("ADD\t%s\t%s", host, certTheirHash)
 207                         goto CertUpdate
 208                 case 11:
 209                         sinkCert <- fmt.Sprintf("ONCE\t%s\t%s", host, certTheirHash)
 210                         acceptedAdd(host, certTheirHash)
 211                         return nil
 212                 case 12:
 213                         rejectedAdd(host, certTheirHash)
 214                         fallthrough
 215                 default:
 216                         sinkCert <- fmt.Sprintf("DENY\t%s\t%s", host, certTheirHash)
 217                         return ErrRejected{host}
 218                 }
 219         } else {
 220                 if !os.IsNotExist(err) {
 221                         return err
 222                 }
 223                 sinkCert <- fmt.Sprintf("TOFU\t%s\t%s", host, certTheirHash)
 224         }
 225 CertUpdate:
 226         tmp, err := os.CreateTemp(*certs, "")
 227         if err != nil {
 228                 log.Fatalln(err)
 229         }
 230         for _, rawCert := range rawCerts {
 231                 err = pem.Encode(tmp, &pem.Block{Type: "CERTIFICATE", Bytes: rawCert})
 232                 if err != nil {
 233                         log.Fatalln(err)
 234                 }
 235         }
 236         tmp.Close()
 237         os.Rename(tmp.Name(), fn)
 238         acceptedAdd(host, certTheirHash)
 239         return nil
 240 }