cmd/tlsc/main.go

   1 /*
   2 ucspi/cmd/tlsc -- UCSPI TLS client
   3 Copyright (C) 2021 Sergey Matveev <stargrave@stargrave.org>
   4
   5 This program is free software: you can redistribute it and/or modify
   6 it under the terms of the GNU General Public License as published by
   7 the Free Software Foundation, version 3 of the License.
   8
   9 This program is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 GNU General Public License for more details.
  13
  14 You should have received a copy of the GNU General Public License
  15 along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16 */
  17
  18 package main
  19
  20 import (
  21         "bytes"
  22         "crypto/sha256"
  23         "crypto/tls"
  24         "crypto/x509"
  25         "encoding/hex"
  26         "encoding/pem"
  27         "errors"
  28         "flag"
  29         "fmt"
  30         "io"
  31         "log"
  32         "os"
  33         "os/exec"
  34
  35         "go.cypherpunks.ru/ucspi"
  36 )
  37
  38 func main() {
  39         onlyShow := flag.Bool("show", false, "Show server's certificate and exit")
  40         crtPath := flag.String("cert", "", "Path to client X.509 certificate")
  41         prvPath := flag.String("key", "", "Path to client PKCS#8 private key")
  42         casPath := flag.String("ca", "", "Path to CA certificates file")
  43         hostname := flag.String("name", "example.com", "Expected server's hostname")
  44         fpr := flag.String("fpr", "", "Expected SHA256 hash of server certificate's SPKI")
  45         flag.Usage = func() {
  46                 fmt.Fprintf(os.Stderr, `Usage: tcpclient host port tlsc -name expected.name
  47         [-cert cert.pem -key prv.pem] [-ca CAs.pem] [-fpr DEADBABE] [-show]
  48         program [args...]
  49
  50 `)
  51                 flag.PrintDefaults()
  52         }
  53         flag.Parse()
  54         log.SetFlags(log.Lshortfile)
  55
  56         if len(flag.Args()) == 0 {
  57                 flag.Usage()
  58                 os.Exit(1)
  59         }
  60
  61         cfg := &tls.Config{}
  62         if *hostname == "" || *onlyShow {
  63                 cfg.InsecureSkipVerify = true
  64         }
  65         if *hostname != "" {
  66                 cfg.ServerName = *hostname
  67         }
  68         if *crtPath != "" {
  69                 crtRaw, _, err := ucspi.CertificateFromFile(*crtPath)
  70                 if err != nil {
  71                         log.Fatalln(err)
  72                 }
  73                 prv, err := ucspi.PrivateKeyFromFile(*prvPath)
  74                 if err != nil {
  75                         log.Fatalln(err)
  76                 }
  77                 cfg.Certificates = []tls.Certificate{{
  78                         Certificate: [][]byte{crtRaw},
  79                         PrivateKey:  prv,
  80                 }}
  81         }
  82         if *casPath != "" {
  83                 var err error
  84                 cfg.RootCAs, err = ucspi.CertPoolFromFile(*casPath)
  85                 if err != nil {
  86                         log.Fatalln(err)
  87                 }
  88         }
  89         if *fpr != "" {
  90                 hshOur, err := hex.DecodeString(*fpr)
  91                 if err != nil {
  92                         log.Fatalln(err)
  93                 }
  94                 cfg.VerifyPeerCertificate = func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
  95                         spki := verifiedChains[0][0].RawSubjectPublicKeyInfo
  96                         hshTheir := sha256.Sum256(spki)
  97                         if bytes.Compare(hshOur, hshTheir[:]) != 0 {
  98                                 return errors.New("server certificate's SPKI hash mismatch")
  99                         }
 100                         return nil
 101                 }
 102         }
 103
 104         conn := &ucspi.Conn{R: os.NewFile(6, "R"), W: os.NewFile(7, "W")}
 105         if conn.R == nil {
 106                 log.Fatalln("no 6 file descriptor")
 107         }
 108         if conn.W == nil {
 109                 log.Fatalln("no 7 file descriptor")
 110         }
 111         tlsConn := tls.Client(conn, cfg)
 112         if err := tlsConn.Handshake(); err != nil {
 113                 log.Fatalln(err)
 114         }
 115         connState := tlsConn.ConnectionState()
 116         if *onlyShow {
 117                 fmt.Fprintf(
 118                         os.Stderr, "Version: %04x\nCipherSuite: %s\n",
 119                         connState.Version, tls.CipherSuiteName(connState.CipherSuite),
 120                 )
 121                 for _, cert := range connState.PeerCertificates {
 122                         os.Stderr.WriteString("\n")
 123                         pem.Encode(os.Stderr, &pem.Block{Type: "CERTIFICATE", Bytes: cert.Raw})
 124                         hsh := sha256.Sum256(cert.RawSubjectPublicKeyInfo)
 125                         fmt.Fprintf(
 126                                 os.Stderr, "Issuer: %s\nSubject: %s\nValidity: %s / %s\nSPKI SHA256: %s\n",
 127                                 cert.Issuer, cert.Subject, cert.NotBefore, cert.NotAfter,
 128                                 hex.EncodeToString(hsh[:]),
 129                         )
 130                 }
 131                 return
 132         }
 133         dn := connState.PeerCertificates[0].Subject.String()
 134
 135         args := flag.Args()
 136         cmd := exec.Command(args[0], args[1:]...)
 137         rr, rw, err := os.Pipe()
 138         if err != nil {
 139                 log.Fatalln(err)
 140         }
 141         wr, ww, err := os.Pipe()
 142         if err != nil {
 143                 log.Fatalln(err)
 144         }
 145         cmd.ExtraFiles = []*os.File{nil, nil, nil, rr, ww}
 146         cmd.Stdin = os.Stdin
 147         cmd.Stdout = os.Stdout
 148         cmd.Stderr = os.Stderr
 149         cmd.Env = append(os.Environ(), "PROTO=TLS")
 150         cmd.Env = append(cmd.Env, "TLSREMOTEDN="+dn)
 151         if err = cmd.Start(); err != nil {
 152                 log.Fatalln(err)
 153         }
 154         copiers := make(chan struct{})
 155         go func() {
 156                 io.Copy(rw, tlsConn)
 157                 rw.Close()
 158                 close(copiers)
 159         }()
 160         go func() {
 161                 io.Copy(tlsConn, wr)
 162         }()
 163         _, err = cmd.Process.Wait()
 164         <-copiers
 165         if err != nil {
 166                 log.Fatalln(err)
 167         }
 168 }