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         } else {
  65                 cfg.ServerName = *hostname
  66         }
  67         if *crtPath != "" {
  68                 crtRaw, _, err := ucspi.CertificateFromFile(*crtPath)
  69                 if err != nil {
  70                         log.Fatalln(err)
  71                 }
  72                 prv, err := ucspi.PrivateKeyFromFile(*prvPath)
  73                 if err != nil {
  74                         log.Fatalln(err)
  75                 }
  76                 cfg.Certificates = []tls.Certificate{{
  77                         Certificate: [][]byte{crtRaw},
  78                         PrivateKey:  prv,
  79                 }}
  80         }
  81         if *casPath != "" {
  82                 var err error
  83                 cfg.RootCAs, err = ucspi.CertPoolFromFile(*casPath)
  84                 if err != nil {
  85                         log.Fatalln(err)
  86                 }
  87         }
  88         if *fpr != "" {
  89                 hshOur, err := hex.DecodeString(*fpr)
  90                 if err != nil {
  91                         log.Fatalln(err)
  92                 }
  93                 cfg.VerifyPeerCertificate = func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
  94                         spki := verifiedChains[0][0].RawSubjectPublicKeyInfo
  95                         hshTheir := sha256.Sum256(spki)
  96                         if bytes.Compare(hshOur, hshTheir[:]) != 0 {
  97                                 return errors.New("server certificate's SPKI hash mismatch")
  98                         }
  99                         return nil
 100                 }
 101         }
 102
 103         conn := &ucspi.Conn{R: os.NewFile(6, "R"), W: os.NewFile(7, "W")}
 104         if conn.R == nil {
 105                 log.Fatalln("no 6 file descriptor")
 106         }
 107         if conn.W == nil {
 108                 log.Fatalln("no 7 file descriptor")
 109         }
 110         tlsConn := tls.Client(conn, cfg)
 111         if err := tlsConn.Handshake(); err != nil {
 112                 log.Fatalln(err)
 113         }
 114         connState := tlsConn.ConnectionState()
 115         if *onlyShow {
 116                 fmt.Fprintf(
 117                         os.Stderr, "Version: %04x\nCipherSuite: %s\n",
 118                         connState.Version, tls.CipherSuiteName(connState.CipherSuite),
 119                 )
 120                 for _, cert := range connState.PeerCertificates {
 121                         os.Stderr.WriteString("\n")
 122                         pem.Encode(os.Stderr, &pem.Block{Type: "CERTIFICATE", Bytes: cert.Raw})
 123                         hsh := sha256.Sum256(cert.RawSubjectPublicKeyInfo)
 124                         fmt.Fprintf(
 125                                 os.Stderr, "Issuer: %s\nSubject: %s\nValidity: %s / %s\nSPKI SHA256: %s\n",
 126                                 cert.Issuer, cert.Subject, cert.NotBefore, cert.NotAfter,
 127                                 hex.EncodeToString(hsh[:]),
 128                         )
 129                 }
 130                 return
 131         }
 132         dn := connState.PeerCertificates[0].Subject.String()
 133
 134         args := flag.Args()
 135         cmd := exec.Command(args[0], args[1:]...)
 136         rr, rw, err := os.Pipe()
 137         if err != nil {
 138                 log.Fatalln(err)
 139         }
 140         wr, ww, err := os.Pipe()
 141         if err != nil {
 142                 log.Fatalln(err)
 143         }
 144         cmd.ExtraFiles = []*os.File{nil, nil, nil, rr, ww}
 145         cmd.Stdin = os.Stdin
 146         cmd.Stdout = os.Stdout
 147         cmd.Stderr = os.Stderr
 148         cmd.Env = append(os.Environ(), "PROTO=TLS")
 149         cmd.Env = append(cmd.Env, "TLSREMOTEDN="+dn)
 150         if err = cmd.Start(); err != nil {
 151                 log.Fatalln(err)
 152         }
 153         copiers := make(chan struct{})
 154         go func() {
 155                 io.Copy(rw, tlsConn)
 156                 rw.Close()
 157                 close(copiers)
 158         }()
 159         go func() {
 160                 io.Copy(tlsConn, wr)
 161         }()
 162         _, err = cmd.Process.Wait()
 163         <-copiers
 164         if err != nil {
 165                 log.Fatalln(err)
 166         }
 167 }