load public signature verification key from disc

1 files changed, 77 insertions, 0 deletions

diff --git a/key/box.go b/key/box.go
new file mode 100644
index 0000000..05d8991
--- /dev/null
+++ b/key/box.go
@@ -0,0 +1,77 @@
+package key
+
+import (
+	"bytes"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"os"
+)
+
+// BoxPublicKey is a public NaCl box key.
+type BoxPublicKey [32]byte
+
+// BoxPrivateKey is a private NaCl box key.
+type BoxPrivateKey [32]byte
+
+// LoadBoxKeypair reads the public and private NaCl box keys from disc,
+// or generates a new keypair if it does not already exist.
+// These keys can be used for NaCl box (encryption/decryption) operations.
+func LoadBoxKeypair() (pub BoxPublicKey, priv BoxPrivateKey, err error) {
+	err = generateBoxKeypairIfNotExist()
+	if err != nil {
+		return
+	}
+
+	pub, err = loadBoxKey(boxPubKeyFile)
+	if err != nil {
+		return
+	}
+
+	priv, err = loadBoxKey(boxPrivKeyFile)
+
+	return
+}
+
+// LoadBoxPublicKey reads the public NaCl box key from disc,
+// or generates a new keypair if it does not already exist.
+func LoadBoxPublicKey() (BoxPublicKey, error) {
+	err := generateBoxKeypairIfNotExist()
+	if err != nil {
+		return BoxPublicKey{}, err
+	}
+	key, err := loadBoxKey(boxPubKeyFile)
+	return BoxPublicKey(key), err
+}
+
+// loadBoxKey reads a NaCl box key (public or private)  from the specified file.
+func loadBoxKey(filename string) ([32]byte, error) {
+	// Open file.
+	f, err := os.Open(filename)
+	if err != nil {
+		return [32]byte{}, err
+	}
+	defer f.Close()
+
+	// Read key from file.
+	buf, err := io.ReadAll(f)
+	if err != nil {
+		return [32]byte{}, err
+	}
+
+	// Decode key.
+	var key [32]byte
+	if hex.DecodedLen(len(buf)) != len(key) {
+		return [32]byte{}, fmt.Errorf("malformed key: expected %d bytes; got %d",
+			len(key), hex.DecodedLen(len(buf)))
+	}
+	if _, err := hex.Decode(key[:], buf); err != nil {
+		return [32]byte{}, err
+	}
+
+	return key, nil
+}
+
+func (bpk1 BoxPublicKey) Compare(bpk2 BoxPublicKey) int {
+	return bytes.Compare(bpk1[:], bpk2[:])
+}