feat(agent): add agent support (#1828)

api/crypto/ecdsa.go

@@ -0,0 +1,125 @@
+package crypto
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/md5"
+	"crypto/rand"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/hex"
+	"math/big"
+)
+
+const (
+	// PrivateKeyPemHeader represents the header that is appended to the PEM file when
+	// storing the private key.
+	PrivateKeyPemHeader = "EC PRIVATE KEY"
+	// PublicKeyPemHeader represents the header that is appended to the PEM file when
+	// storing the public key.
+	PublicKeyPemHeader = "ECDSA PUBLIC KEY"
+)
+
+// ECDSAService is a service used to create digital signatures when communicating with
+// an agent based environment. It will automatically generates a key pair using ECDSA or
+// can also reuse an existing ECDSA key pair.
+type ECDSAService struct {
+	privateKey    *ecdsa.PrivateKey
+	publicKey     *ecdsa.PublicKey
+	encodedPubKey string
+}
+
+// EncodedPublicKey returns the encoded version of the public that can be used
+// to be shared with other services. It's the hexadecimal encoding of the public key
+// content.
+func (service *ECDSAService) EncodedPublicKey() string {
+	return service.encodedPubKey
+}
+
+// PEMHeaders returns the ECDSA PEM headers.
+func (service *ECDSAService) PEMHeaders() (string, string) {
+	return PrivateKeyPemHeader, PublicKeyPemHeader
+}
+
+// ParseKeyPair parses existing private/public key pair content and associate
+// the parsed keys to the service.
+func (service *ECDSAService) ParseKeyPair(private, public []byte) error {
+	privateKey, err := x509.ParseECPrivateKey(private)
+	if err != nil {
+		return err
+	}
+
+	service.privateKey = privateKey
+
+	encodedKey := hex.EncodeToString(public)
+	service.encodedPubKey = encodedKey
+
+	publicKey, err := x509.ParsePKIXPublicKey(public)
+	if err != nil {
+		return err
+	}
+
+	service.publicKey = publicKey.(*ecdsa.PublicKey)
+
+	return nil
+}
+
+// GenerateKeyPair will create a new key pair using ECDSA.
+func (service *ECDSAService) GenerateKeyPair() ([]byte, []byte, error) {
+	pubkeyCurve := elliptic.P256()
+
+	privatekey, err := ecdsa.GenerateKey(pubkeyCurve, rand.Reader)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	service.privateKey = privatekey
+	service.publicKey = &privatekey.PublicKey
+
+	private, err := x509.MarshalECPrivateKey(service.privateKey)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	public, err := x509.MarshalPKIXPublicKey(service.publicKey)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	encodedKey := hex.EncodeToString(public)
+	service.encodedPubKey = encodedKey
+
+	return private, public, nil
+}
+
+// Sign creates a signature from a message.
+// It automatically hash the message using MD5 and creates a signature from
+// that hash.
+// It then encodes the generated signature in base64.
+func (service *ECDSAService) Sign(message string) (string, error) {
+	digest := md5.New()
+	digest.Write([]byte(message))
+	hash := digest.Sum(nil)
+
+	r := big.NewInt(0)
+	s := big.NewInt(0)
+
+	r, s, err := ecdsa.Sign(rand.Reader, service.privateKey, hash)
+	if err != nil {
+		return "", err
+	}
+
+	keyBytes := service.privateKey.Params().BitSize / 8
+
+	rBytes := r.Bytes()
+	rBytesPadded := make([]byte, keyBytes)
+	copy(rBytesPadded[keyBytes-len(rBytes):], rBytes)
+
+	sBytes := s.Bytes()
+	sBytesPadded := make([]byte, keyBytes)
+	copy(sBytesPadded[keyBytes-len(sBytes):], sBytes)
+
+	signature := append(rBytesPadded, sBytesPadded...)
+
+	return base64.RawStdEncoding.EncodeToString(signature), nil
+}