Added key derivation

cryptokdf/crypto_kdf.go

@@ -0,0 +1,44 @@
+package cryptokdf
+
+// #cgo pkg-config: libsodium
+// #include <stdlib.h>
+// #include <sodium.h>
+import "C"
+import "github.com/GoKillers/libsodium-go/support"
+
+func CryptoKdfKeybytes() int {
+	return int(C.crypto_kdf_keybytes())
+}
+
+func CryptoKdfContextbytes() int {
+	return int(C.crypto_kdf_contextbytes())
+}
+
+func CryptoKdfBytesMin() int {
+	return int(C.crypto_kdf_bytes_min())
+}
+
+func CryptoKdfBytesMax() int {
+	return int(C.crypto_kdf_bytes_max())
+}
+
+func CryptoKdfKeygen(k []byte) {
+	support.CheckSize(k, CryptoKdfKeybytes(), "keybytes")
+	C.crypto_kdf_keygen((*C.uchar)(&k[0]))
+}
+
+func CryptoKdfDeriveFromKey(l int, i uint64, c string, k []byte) ([]byte, int) {
+	support.CheckSize(k, CryptoKdfKeybytes(), "keybytes")
+	support.CheckSize([]byte(c), CryptoKdfContextbytes(), "contextbytes")
+	support.CheckSizeInRange(l, CryptoKdfBytesMin(), CryptoKdfBytesMax(), "subkey_len")
+	out := make([]byte, l)
+
+	exit := int(C.crypto_kdf_derive_from_key(
+		(*C.uchar)(&out[0]),
+		(C.size_t)(l),
+		(C.uint64_t)(i),
+		C.CString(c),
+		(*C.uchar)(&k[0])))
+
+	return out, exit
+}