Initial import

internal/cryptutil/key.go

@@ -0,0 +1,114 @@
+package cryptutil
+
+import (
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"crypto/sha1"
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"os"
+)
+
+type publicKeyer interface {
+	Public() any
+}
+
+// PublicKey returns the public part of a crypto.PrivateKey.
+func PublicKey(key crypto.PrivateKey) any {
+	switch key := key.(type) {
+	case ed25519.PublicKey:
+		return key
+	case ed25519.PrivateKey:
+		return key.Public()
+	case ecdsa.PublicKey:
+		return &key
+	case *ecdsa.PublicKey:
+		return key
+	case *ecdsa.PrivateKey:
+		return &key.PublicKey
+	case rsa.PublicKey:
+		return &key
+	case *rsa.PublicKey:
+		return key
+	case *rsa.PrivateKey:
+		return &key.PublicKey
+	default:
+		if p, ok := key.(publicKeyer); ok {
+			return p.Public()
+		}
+		panic(fmt.Sprintf("don't know how to extract a public key from %T", key))
+	}
+}
+
+// LoadPrivateKey loads a private key from disk.
+func LoadPrivateKey(name string) (crypto.PrivateKey, error) {
+	b, err := os.ReadFile(name)
+	if err != nil {
+		return nil, err
+	}
+	return decodePEMPrivateKey(b)
+}
+
+func decodePEMPrivateKey(b []byte) (key crypto.PrivateKey, err error) {
+	var (
+		rest  = b
+		block *pem.Block
+	)
+	for {
+		if block, rest = pem.Decode(rest); block == nil {
+			return nil, errors.New("mitm: no private key PEM block could be decoded")
+		}
+		switch block.Type {
+		case "EC PRIVATE KEY":
+			return x509.ParseECPrivateKey(block.Bytes)
+
+		case "RSA PRIVATE KEY":
+			return x509.ParsePKCS1PrivateKey(block.Bytes)
+
+		case "PRIVATE KEY":
+			return x509.ParsePKCS8PrivateKey(block.Bytes)
+		}
+	}
+}
+
+// GenerateKeyID generates the PKIX public key ID.
+func GenerateKeyID(key crypto.PublicKey) []byte {
+	b, err := x509.MarshalPKIXPublicKey(key)
+	if err != nil {
+		return nil
+	}
+	return sha1.New().Sum(b)
+}
+
+func keyType(key any) string {
+	switch key := key.(type) {
+	case ed25519.PrivateKey:
+		return "ed25519"
+	case *ecdsa.PrivateKey:
+		return "ecdsa (" + curveType(key.Curve) + ")"
+	case *rsa.PrivateKey:
+		return "rsa"
+	default:
+		return fmt.Sprintf("%T", key)
+	}
+}
+
+func curveType(c elliptic.Curve) string {
+	switch c {
+	case elliptic.P224():
+		return "p224"
+	case elliptic.P256():
+		return "p256"
+	case elliptic.P384():
+		return "p384"
+	case elliptic.P521():
+		return "p521"
+	default:
+		return fmt.Sprintf("%T", c)
+	}
+}