initial release. tests pass at least.

funcs.go

@@ -0,0 +1,33 @@
+package cc20p1305ssh
+
+/*
+	New returns a cipher.AEAD from KDF-derived key.
+
+	Currently, key should be KDFKeySize bytes and returned by bcrypt_pbkdf as it's currently the
+	only OpenSSH-supported KDF. It is up to the caller to perform the appropriate KDF.
+
+	Per the chacha20polycom1305@openssh.com specification, only the first KeySize bytes of key
+	is used for encrypting the private key. The second half (the canonical key is 64 bytes)
+	would be used for traffic purposes, but since this is a static blob it is not used.
+
+	If key is nil or <KDFKeySize bytes in length, an error ErrInvalidKeySize will be returned.
+
+	*DO NOT USE crypter FOR STREAMS. THIS SHOULD ONLY BE USED TO ENCRYPT AN OPENSSH PRIVATE KEY.*
+*/
+func New(key []byte) (crypter *ChaCha20Poly1305OpenSSH, err error) {
+
+	var crypterReal ChaCha20Poly1305OpenSSH
+
+	if key == nil || len(key) < KDFKeySize {
+		err = ErrInvalidKeySize
+		return
+	}
+
+	crypterReal = ChaCha20Poly1305OpenSSH{}
+	copy(crypterReal.kdfKey[:], key[:KDFKeySize])
+	copy(crypterReal.realKey[:], key[:KeySize])
+
+	crypter = &crypterReal
+
+	return
+}