status-go/server/pairing/certs.go

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package pairing
import (
"crypto/ecdsa"
"crypto/sha256"
"crypto/tls"
"crypto/x509"
"encoding/asn1"
"encoding/pem"
"fmt"
"math/big"
"net"
"net/url"
"time"
"go.uber.org/zap"
"github.com/status-im/status-go/logutils"
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"github.com/status-im/status-go/server"
)
const CertificateMaxClockDrift = time.Minute
func makeSerialNumberFromKey(pk *ecdsa.PrivateKey) *big.Int {
h := sha256.New()
h.Write(append(pk.D.Bytes(), append(pk.Y.Bytes(), pk.X.Bytes()...)...))
return new(big.Int).SetBytes(h.Sum(nil))
}
func GenerateCertFromKey(pk *ecdsa.PrivateKey, from time.Time, IPAddresses []net.IP, DNSNames []string) (tls.Certificate, []byte, error) {
cert := server.GenerateX509Cert(makeSerialNumberFromKey(pk), from.Add(-CertificateMaxClockDrift), from.Add(time.Hour), IPAddresses, DNSNames)
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certPem, keyPem, err := server.GenerateX509PEMs(cert, pk)
if err != nil {
return tls.Certificate{}, nil, err
}
tlsCert, err := tls.X509KeyPair(certPem, keyPem)
if err != nil {
return tls.Certificate{}, nil, err
}
block, _ := pem.Decode(certPem)
if block == nil {
return tls.Certificate{}, nil, fmt.Errorf("failed to decode certPem")
}
leaf, err := x509.ParseCertificate(block.Bytes)
if err != nil {
return tls.Certificate{}, nil, err
}
tlsCert.Leaf = leaf
return tlsCert, certPem, nil
}
// verifyCertPublicKey checks that the ecdsa.PublicKey using in a x509.Certificate matches a known ecdsa.PublicKey
func verifyCertPublicKey(cert *x509.Certificate, publicKey *ecdsa.PublicKey) error {
certKey, ok := cert.PublicKey.(*ecdsa.PublicKey)
if !ok {
return fmt.Errorf("unexpected public key type, expected ecdsa.PublicKey")
}
if !certKey.Equal(publicKey) {
return fmt.Errorf("server certificate MUST match the given public key")
}
return nil
}
// verifyCertSig checks that a x509.Certificate's Signature verifies against x509.Certificate's PublicKey
// If the x509.Certificate's PublicKey is not an ecdsa.PublicKey an error will be thrown
func verifyCertSig(cert *x509.Certificate) (bool, error) {
var esig struct {
R, S *big.Int
}
if _, err := asn1.Unmarshal(cert.Signature, &esig); err != nil {
return false, err
}
hash := sha256.New()
hash.Write(cert.RawTBSCertificate)
ecKey, ok := cert.PublicKey.(*ecdsa.PublicKey)
if !ok {
return false, fmt.Errorf("certificate public is not an ecdsa.PublicKey")
}
verified := ecdsa.Verify(ecKey, hash.Sum(nil), esig.R, esig.S)
return verified, nil
}
// verifyCert verifies an x509.Certificate against a known ecdsa.PublicKey
// combining the checks of verifyCertPublicKey and verifyCertSig.
// If an x509.Certificate fails to verify an error is also thrown
func verifyCert(cert *x509.Certificate, publicKey *ecdsa.PublicKey) error {
err := verifyCertPublicKey(cert, publicKey)
if err != nil {
return err
}
verified, err := verifyCertSig(cert)
if err != nil {
return err
}
if !verified {
return fmt.Errorf("server certificate signature MUST verify")
}
return nil
}
// getServerCert pings a given tls host, extracts and returns its x509.Certificate
// the function expects there to be only 1 certificate
func getServerCert(URL *url.URL) (*x509.Certificate, error) {
conf := &tls.Config{
InsecureSkipVerify: true, // nolint: gosec // Only skip verify to get the server's TLS cert. DO NOT skip for any other reason.
}
// one second should be enough to get the server's TLS cert in LAN?
conn, err := tls.DialWithDialer(&net.Dialer{Timeout: time.Second}, "tcp", URL.Host, conf)
if err != nil {
return nil, err
}
defer func(conn *tls.Conn) {
if e := conn.Close(); e != nil {
logutils.ZapLogger().Warn("failed to close temporary TLS connection:", zap.Error(e))
}
}(conn)
certs := conn.ConnectionState().PeerCertificates
if len(certs) != 1 {
return nil, fmt.Errorf("expected 1 TLS certificate, received '%d'", len(certs))
}
return certs[0], nil
}