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.gitignore vendored Normal file
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pktls
testsrv
testcl
**.swp

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COPYING Normal file
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Apache License
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http://www.apache.org/licenses/
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pktls
=====
**DO NOT USE THIS (YET), UNAUDITED, PRE-RELEASE.**
Description
-----------
A Go library to allow using wireguard-style asymmetric keys to configure mutual TLS authentication.
.-------------.
| Server |
|-------------| .--------------.
| server.priv | | Client 1 |
| | <---- TLS -----.---- |--------------|
| client1.pub | | | client1.priv |
| client2.pub | | | server.pub |
'-------------' | '--------------'
| .--------------.
| | Client 2 |
'---- |--------------|
| client2.priv |
| server.pub |
'--------------'
No more having to deal with openssl, CAs, expiring certificates, and complex x509 bootstrap - just use genkey/pubkey!
Under the hood, it uses ED25519 to generate self-signed certificates for both sides.o
Key Generation
--------------
go get code.hackerspace.pl/q3k/pktls
go build code.hackerspace.pl/q3k/pkgtls/cmd/pktls
./pktls genkey > server.priv
./pktls pubkey < server.priv > server.pub
The resulting keys look very much like wireguard keys, but are _not compatible_. pktls keys will not work as wireguard keys, and vice-versa.
Library usage
-------------
On the server side:
pk, err := pktls.ServerFromString("<private key>", []string{"<client public key>", "<client public key>"})
config := tls.Config{}
pk.Configure(&config)
// Use config with tls.Listen, grpc/credentials.NewTLS, etc.
On the client side:
pk, err := pktls.ClientFromString("<private key>", "<server public key>")
config := tls.Config{}
pk.Configure(&config)
// Use config with tls.Dial, grpc/credentials.NewTLS, etc.
For example code, see cmd/test{srv,cl}.
Sample client/server
--------------------
To test this library without writing Go, you can run a pktls server/client pair as following:
go get code.hackerspace.pl/q3k/pktls
go build code.hackerspace.pl/q3k/pkgtls/cmd/pktls
./pktls genkey > server.priv
./pktls pubkey < server.priv > server.pub
./pktls genkey > client.priv
./pktls pubkey < client.priv > client.pub
go build code.hackerspace.pl/q3k/pkgtls/cmd/testsrv
./testsrv -private_key $(cat server.priv) -allowed $(cat client.pub) -listen 127.0.0.1:1337
# and on another terminal:
go build code.hackerspace.pl/q3k/pkgtls/cmd/testcl
./testcl -private_key $(cat client.priv) -remote_key $(cat server.pub) -remote 127.0.0.1:1337
You should observe the client receiving a hello message from the server (”yo”), and the server being able to introspect the identity of the client.

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package main
import (
"bufio"
"fmt"
"io"
"log"
"os"
"code.hackerspace.pl/q3k/pktls"
)
func usage(cmd string) {
fmt.Fprintf(os.Stderr, `Usage: %s <subcommand>
Available subcommands:
genkey: Generates a new private key and writes it to stdout
pubkey: Reads a private key from stdin and writes a public key to stdout
`, cmd)
}
func main() {
switch len(os.Args) {
case 0:
// This should never happen.
panic("no argv?")
case 1:
usage(os.Args[0])
default:
switch os.Args[1] {
case "genkey":
genkey()
case "pubkey":
pubkey()
default:
usage(os.Args[0])
}
}
}
func genkey() {
key, err := pktls.PrivateGenerate()
if err != nil {
log.Fatalf("Generation failed: %v", err)
}
fmt.Printf("%s\n", key.String())
}
func pubkey() {
r := bufio.NewReader(os.Stdin)
data, err := r.ReadString('\n')
if err != nil && err != io.EOF {
log.Fatalf("Read from stdin failed: %v", err)
}
priv, err := pktls.PrivateFromString(data)
if err != nil {
log.Fatalf("Private key read failed: %v", err)
}
fmt.Printf("%s\n", priv.Public().String())
}

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package main
import (
"crypto/tls"
"flag"
"io"
"os"
"code.hackerspace.pl/q3k/pktls"
"github.com/golang/glog"
)
var (
flagRemote string
flagPrivateKey string
flagRemoteKey string
)
func init() {
flag.Set("logtostderr", "true")
}
func main() {
flag.StringVar(&flagRemote, "remote", "127.0.0.1:1337", "Server address")
// In production code, do not accept private key literals on the command line,
// instead read them from a file.
flag.StringVar(&flagPrivateKey, "private_key", "", "Client private key")
flag.StringVar(&flagRemoteKey, "remote_key", "", "Server public key")
flag.Parse()
if flagPrivateKey == "" {
glog.Exitf("-private_key must be set")
}
if flagRemoteKey == "" {
glog.Exitf("-remote_key must be set")
}
pk, err := pktls.ClientFromString(flagPrivateKey, flagRemoteKey)
if err != nil {
glog.Exitf("loading keys failed: %v", err)
}
glog.Infof("Connecting with pubkey %s", pk.PrivateKey.Public().String())
config := tls.Config{}
err = pk.Configure(&config)
if err != nil {
glog.Exitf("pki.Configure: %v", err)
}
conn, err := tls.Dial("tcp", flagRemote, &config)
if err != nil {
glog.Exitf("Dial: %v", err)
}
_, err = io.Copy(os.Stdout, conn)
if err != nil && err != io.EOF {
glog.Exitf("Copy failed: %v", err)
}
}

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package main
import (
"crypto/tls"
"flag"
"fmt"
"net"
"strings"
"time"
"code.hackerspace.pl/q3k/pktls"
"github.com/golang/glog"
)
var (
flagListen string
flagPrivate string
flagAllowed string
)
func init() {
flag.Set("logtostderr", "true")
}
func main() {
flag.StringVar(&flagListen, "listen", "0.0.0.0:1337", "Listen on address")
// In production code, do not accept private key literals on the command line,
// instead read them from a file.
flag.StringVar(&flagPrivate, "private_key", "", "Server private key")
flag.StringVar(&flagAllowed, "allowed", "", "Comma-separated list of allowed client public keys")
flag.Parse()
if flagPrivate == "" {
glog.Exitf("-private_key must be set")
}
// Parse allowed keys, making them unique and stripping whitespace.
allowedRaw := strings.Split(flagAllowed, ",")
allowedSet := make(map[string]bool)
for _, pk := range allowedRaw {
pk = strings.TrimSpace(pk)
if len(pk) == 0 {
continue
}
allowedSet[pk] = true
}
var allowed []string
for pk, _ := range allowedSet {
allowed = append(allowed, pk)
}
pk, err := pktls.ServerFromString(flagPrivate, allowed)
if err != nil {
glog.Exitf("loading keys failed: %v", err)
}
glog.Infof("Starting with pubkey %s", pk.PrivateKey.Public().String())
config := tls.Config{}
err = pk.Configure(&config)
if err != nil {
glog.Exitf("pki.Configure: %v", err)
}
listener, err := tls.Listen("tcp", flagListen, &config)
if err != nil {
glog.Exitf("tcp.Listen(%q): %v", flagListen, err)
}
defer listener.Close()
glog.Infof("Listening on %v", flagListen)
for {
cl, err := listener.Accept()
if err != nil {
glog.Exitf("Accept failed: %v", err)
}
handle(cl)
}
}
func handle(cl net.Conn) {
defer cl.Close()
identity, err := pktls.ClientPubkey(cl)
if err != nil {
glog.Infof("%v: could not get identity: %v", cl.RemoteAddr(), err)
return
}
glog.Infof("%v: connected (%v)", cl.RemoteAddr(), identity)
t := time.NewTicker(1 * time.Second)
defer t.Stop()
fmt.Fprintf(cl, "yo\n")
}

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config.go Normal file
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package pktls
import (
"crypto/tls"
"crypto/x509"
"errors"
"fmt"
)
type Config struct {
PrivateKey PrivateKey
}
type ServerConfig struct {
Config
Allowed []PublicKey
}
type ClientConfig struct {
Config
Server PublicKey
}
func ServerFromString(privkey string, allowed []string) (*ServerConfig, error) {
if len(allowed) == 0 {
return nil, fmt.Errorf("no allowed keys set, server will accept no clients")
}
priv, err := PrivateFromString(privkey)
if err != nil {
return nil, fmt.Errorf("server private key: %w", err)
}
allowedKeys := make([]PublicKey, len(allowed))
for i, pk := range allowed {
public, err := PublicFromString(pk)
if err != nil {
return nil, fmt.Errorf("allowed key %d: %w", i, err)
}
allowedKeys[i] = public
}
cfg := &ServerConfig{
Config: Config{
PrivateKey: priv,
},
Allowed: allowedKeys,
}
return cfg, nil
}
func ClientFromString(privkey string, server string) (*ClientConfig, error) {
priv, err := PrivateFromString(privkey)
if err != nil {
return nil, fmt.Errorf("client private key: %w", err)
}
serverKey, err := PublicFromString(server)
if err != nil {
return nil, fmt.Errorf("server public key: %w", err)
}
cfg := &ClientConfig{
Config: Config{
PrivateKey: priv,
},
Server: serverKey,
}
return cfg, nil
}
func (s *ServerConfig) Configure(config *tls.Config) error {
tlsCert, err := s.PrivateKey.GenerateTLS(TLSServer)
if err != nil {
return fmt.Errorf("generating TLS certificate/keypair failed: %w", err)
}
config.Certificates = []tls.Certificate{*tlsCert}
config.ClientAuth = tls.RequireAnyClientCert
config.VerifyPeerCertificate = s.VerifyPeerCertificate
return nil
}
func (s *ServerConfig) VerifyPeerCertificate(rawCerts [][]byte, _ [][]*x509.Certificate) error {
if len(rawCerts) != 1 {
return fmt.Errorf("need exacty one client certificate")
}
cert := rawCerts[0]
lastErr := ErrWrongIdentity
for _, allowed := range s.Allowed {
err := allowed.Verify(TLSServer, cert)
switch {
case err == nil:
return nil
case errors.Is(err, ErrWrongIdentity):
lastErr = err
continue
default:
return err
}
}
return lastErr
}
func (c *ClientConfig) Configure(config *tls.Config) error {
tlsCert, err := c.PrivateKey.GenerateTLS(TLSClient)
if err != nil {
return fmt.Errorf("generating TLS certificate/keypair failed: %w", err)
}
config.Certificates = []tls.Certificate{*tlsCert}
config.InsecureSkipVerify = true
config.VerifyPeerCertificate = c.VerifyPeerCertificate
return nil
}
func (c *ClientConfig) VerifyPeerCertificate(rawCerts [][]byte, _ [][]*x509.Certificate) error {
if len(rawCerts) != 1 {
return fmt.Errorf("need exacty one server certificate")
}
cert := rawCerts[0]
return c.Server.Verify(TLSClient, cert)
}

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go.mod Normal file
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module code.hackerspace.pl/q3k/pktls
go 1.14
require (
github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b
github.com/jorrizza/ed2curve25519 v0.1.0
golang.org/x/crypto v0.0.0-20201117144127-c1f2f97bffc9
)

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go.sum Normal file
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@ -0,0 +1,14 @@
github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b h1:VKtxabqXZkF25pY9ekfRL6a582T4P37/31XEstQ5p58=
github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
github.com/jorrizza/ed2curve25519 v0.1.0 h1:P58ZEiVKW4vknYuGyOXuskMm82rTJyGhgRGrMRcCE8E=
github.com/jorrizza/ed2curve25519 v0.1.0/go.mod h1:27VPNk2FnNqLQNvvVymiX41VE/nokPyn5HHP7gtfYlo=
golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
golang.org/x/crypto v0.0.0-20201117144127-c1f2f97bffc9 h1:phUcVbl53swtrUN8kQEXFhUxPlIlWyBfKmidCu7P95o=
golang.org/x/crypto v0.0.0-20201117144127-c1f2f97bffc9/go.mod h1:jdWPYTVW3xRLrWPugEBEK3UY2ZEsg3UU495nc5E+M+I=
golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/term v0.0.0-20201117132131-f5c789dd3221/go.mod h1:Nr5EML6q2oocZ2LXRh80K7BxOlk5/8JxuGnuhpl+muw=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

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keys.go Normal file
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package pktls
import (
"crypto/ed25519"
"crypto/rand"
"encoding/base64"
"fmt"
"strings"
)
const (
b64PrefixPublic = "p1"
b64PrefixPrivate = "s1"
keyLength = 32
)
type PublicKey ed25519.PublicKey
type PrivateKey ed25519.PrivateKey
func (p PrivateKey) String() string {
return b64PrefixPrivate + base64.StdEncoding.EncodeToString(ed25519.PrivateKey(p).Seed())
}
func privateFromBytes(seed []byte) PrivateKey {
if len(seed) != keyLength {
panic("seed must be 32 bytes long")
}
return PrivateKey(ed25519.NewKeyFromSeed(seed))
}
func PrivateGenerate() (PrivateKey, error) {
var seed [keyLength]byte
_, err := rand.Read(seed[:])
if err != nil {
return nil, fmt.Errorf("rand.Read: %v", err)
}
return privateFromBytes(seed[:]), nil
}
func PrivateFromString(s string) (PrivateKey, error) {
if !strings.HasPrefix(s, b64PrefixPrivate) {
if strings.HasPrefix(s, b64PrefixPublic) {
return nil, fmt.Errorf("invalid key: looks like a public key?")
}
return nil, fmt.Errorf("invalid key: not a pktls key")
}
s = s[len(b64PrefixPrivate):]
bytes, err := base64.StdEncoding.DecodeString(s)
if err != nil {
return nil, fmt.Errorf("invalid key: base64 decode failed")
}
if len(bytes) != keyLength {
return nil, fmt.Errorf("invalid key: wrong length")
}
return privateFromBytes(bytes), nil
}
func (p PrivateKey) Public() PublicKey {
return PublicKey(ed25519.PrivateKey(p).Public().(ed25519.PublicKey))
}
func publicFromBytes(pk []byte) PublicKey {
return PublicKey(pk)
}
func PublicFromString(s string) (PublicKey, error) {
if !strings.HasPrefix(s, b64PrefixPublic) {
if strings.HasPrefix(s, b64PrefixPrivate) {
return nil, fmt.Errorf("invalid key: looks like a private key?")
}
return nil, fmt.Errorf("invalid key: not a pktls key")
}
s = s[len(b64PrefixPublic):]
bytes, err := base64.StdEncoding.DecodeString(s)
if err != nil {
return nil, fmt.Errorf("invalid key: base64 decode failed")
}
if len(bytes) != keyLength {
return nil, fmt.Errorf("invalid key: wrong length")
}
return publicFromBytes(bytes), nil
}
func (p PublicKey) String() string {
return b64PrefixPublic + base64.StdEncoding.EncodeToString(p)
}

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keys_test.go Normal file
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package pktls
import (
"bytes"
"crypto"
"crypto/ed25519"
"crypto/rand"
"testing"
)
func TestPrivateIO(t *testing.T) {
priv1, err := PrivateGenerate()
if err != nil {
t.Fatalf("PrivateGenerate: %v", err)
}
str := priv1.String()
priv2, err := PrivateFromString(str)
if err != nil {
t.Fatalf("PrivateFromString: %v", err)
}
// TODO(q3k): use ed25519.PrivateKey.Equal when go 1.15 becomes a bit more mainstream
if !bytes.Equal(priv1, priv2) {
t.Fatalf("private key re-read from string differs from original")
}
}
func TestPublicIO(t *testing.T) {
priv1, err := PrivateGenerate()
if err != nil {
t.Fatalf("PrivateGenerate: %v", err)
}
pub1 := priv1.Public()
str := pub1.String()
pub2, err := PublicFromString(str)
if err != nil {
t.Fatalf("PublicFromString: %v", err)
}
// TODO(q3k): use ed25519.PublicKey.Equal when go 1.15 becomes a bit more mainstream
if !bytes.Equal(pub1, pub2) {
t.Fatalf("public key re-read from string differs from original")
}
}
func TestE2E(t *testing.T) {
// genkey equivalent
priv1, err := PrivateGenerate()
if err != nil {
t.Fatalf("PrivateGenerate: %v", err)
}
priv := priv1.String()
// pubkey equivalent
priv2, err := PrivateFromString(priv)
if err != nil {
t.Fatalf("PrivateFromString: %v", err)
}
pub := priv2.Public().String()
// sender equivalent
msg := []byte("ahou")
sig, err := ed25519.PrivateKey(priv2).Sign(rand.Reader, msg, crypto.Hash(0))
if err != nil {
t.Fatalf("Sign: %v", err)
}
// receiver equivalent
pub1, err := PublicFromString(pub)
if err != nil {
t.Fatalf("PublicFromString: %v", err)
}
if !ed25519.Verify(ed25519.PublicKey(pub1), msg, sig) {
t.Fatalf("Signature verification failed")
}
}

170
tls.go Normal file
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package pktls
import (
"bytes"
"crypto"
"crypto/ed25519"
"crypto/rand"
"crypto/sha1"
"crypto/tls"
"crypto/x509"
"crypto/x509/pkix"
"encoding/asn1"
"encoding/pem"
"errors"
"fmt"
"math/big"
"net"
"time"
)
type TLSMode int
const (
TLSServer TLSMode = iota
TLSClient
)
var (
// From RFC 5280 Section 4.1.2.5
unknownNotAfter = time.Unix(253402300799, 0)
ErrWrongIdentity = errors.New("unknown identity")
)
// Workaround for https://github.com/golang/go/issues/26676 in Go's crypto/x509. Specifically Go
// violates Section 4.2.1.2 of RFC 5280 without this.
// Fixed for 1.15 in https://go-review.googlesource.com/c/go/+/227098/.
//
// Taken from https://github.com/FiloSottile/mkcert/blob/master/cert.go#L295 written by one of Go's
// crypto engineers
func calculateSKID(pubKey crypto.PublicKey) ([]byte, error) {
spkiASN1, err := x509.MarshalPKIXPublicKey(pubKey)
if err != nil {
return nil, err
}
var spki struct {
Algorithm pkix.AlgorithmIdentifier
SubjectPublicKey asn1.BitString
}
_, err = asn1.Unmarshal(spkiASN1, &spki)
if err != nil {
return nil, err
}
skid := sha1.Sum(spki.SubjectPublicKey.Bytes)
return skid[:], nil
}
func (p PrivateKey) GenerateTLS(mode TLSMode) (*tls.Certificate, error) {
private := ed25519.PrivateKey(p)
public := private.Public()
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 127)
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
return nil, fmt.Errorf("failed to generate serial number: %w", err)
}
skid, err := calculateSKID(public)
if err != nil {
return nil, fmt.Errorf("failed to calculate subject key DI: %w", err)
}
template := x509.Certificate{
SerialNumber: serialNumber,
Subject: pkix.Name{
Organization: []string{"pktls"},
},
NotBefore: time.Now(),
NotAfter: unknownNotAfter,
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
BasicConstraintsValid: true,
SubjectKeyId: skid,
AuthorityKeyId: skid,
}
switch mode {
case TLSServer:
template.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth}
case TLSClient:
template.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth}
default:
return nil, fmt.Errorf("invalid TLS mode argument")
}
certDER, err := x509.CreateCertificate(rand.Reader, &template, &template, public, private)
if err != nil {
return nil, fmt.Errorf("failed to sign certificate: %w", err)
}
keyDER, err := x509.MarshalPKCS8PrivateKey(private)
if err != nil {
return nil, fmt.Errorf("failed to marshal private key: %w", err)
}
keyPEM := pem.EncodeToMemory(&pem.Block{Type: "PRIVATE KEY", Bytes: keyDER})
certPEM := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: certDER})
tlsCert, err := tls.X509KeyPair(certPEM, keyPEM)
if err != nil {
return nil, fmt.Errorf("failed to use new certificate: %w", err)
}
return &tlsCert, nil
}
func parseCertificate(cert *x509.Certificate) (PublicKey, error) {
if cert.PublicKeyAlgorithm != x509.Ed25519 {
return nil, fmt.Errorf("certificate subject public key algorithm not ED25519")
}
presented := cert.PublicKey.(ed25519.PublicKey)
if len(presented) != keyLength {
return nil, fmt.Errorf("%w: pubkey invalid", ErrWrongIdentity)
}
return publicFromBytes(presented), nil
}
func (p PublicKey) Verify(mode TLSMode, pem []byte) error {
cert, err := x509.ParseCertificate(pem)
if err != nil {
return err
}
presented, err := parseCertificate(cert)
if err != nil {
return err
}
if !bytes.Equal(presented, p) {
return fmt.Errorf("%w: pubkey %s", ErrWrongIdentity, presented.String())
}
for _, ku := range cert.ExtKeyUsage {
switch mode {
case TLSServer:
if ku == x509.ExtKeyUsageClientAuth {
return nil
}
case TLSClient:
if ku == x509.ExtKeyUsageServerAuth {
return nil
}
}
}
return fmt.Errorf("%w: pubkey not valid for this mode", ErrWrongIdentity)
}
func ClientPubkey(c net.Conn) (*PublicKey, error) {
inner, ok := c.(*tls.Conn)
if !ok {
return nil, fmt.Errorf("not a TLS connection")
}
if err := inner.Handshake(); err != nil {
return nil, fmt.Errorf("handshake failed: %w", err)
}
state := inner.ConnectionState()
pubkey, err := parseCertificate(state.PeerCertificates[0])
if err != nil {
return nil, fmt.Errorf("internal error: invalid certificate: %w", err)
}
return &pubkey, nil
}