Initial commit: crypto.go and protocol.go implementation + unit tests

crypto_test.go

@@ -0,0 +1,108 @@
+package ownwire_sdk_test
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+
+	sdk "ownwire.net/ownwire-sdk"
+)
+
+func derive_nonce_reference(shared_key [32]byte, session_uuid_bytes [16]byte, salt16 [16]byte, seq_num uint64, is_response bool) [12]byte {
+	seq_be8 := [8]byte{}
+	for i := 7; i >= 0; i-- {
+		seq_be8[i] = byte(seq_num & 0xff)
+		seq_num >>= 8
+	}
+
+	flag := byte(0)
+	if is_response {
+		flag = 1
+	}
+
+	mac := hmac.New(sha256.New, shared_key[:])
+	mac.Write([]byte("ownwire/v1:gcm-nonce"))
+	mac.Write(session_uuid_bytes[:])
+	mac.Write(salt16[:])
+	mac.Write(seq_be8[:])
+	mac.Write([]byte{flag})
+
+	sum := mac.Sum(nil)
+
+	var iv [12]byte
+	copy(iv[:], sum[:12])
+	return iv
+}
+
+var _ = Describe("Crypto", func() {
+	It("parses UUID bytes", func() {
+		uuid_str := "cb653f53-6f7d-4aeb-ba0d-d2b17c290d8a"
+		uuid_bytes, err := sdk.ParseUUIDBytes(uuid_str)
+		Expect(err).To(BeNil())
+		Expect(hex.EncodeToString(uuid_bytes[:])).To(Equal("cb653f536f7d4aebba0dd2b17c290d8a"))
+	})
+
+	It("derives nonce exactly as reference implementation", func() {
+		var shared_key [32]byte
+		for i := 0; i < 32; i++ {
+			shared_key[i] = byte(i)
+		}
+
+		uuid_bytes, err := sdk.ParseUUIDBytes("cb653f53-6f7d-4aeb-ba0d-d2b17c290d8a")
+		Expect(err).To(BeNil())
+
+		var salt16 [16]byte
+		for i := 0; i < 16; i++ {
+			salt16[i] = byte(0xa0 + i)
+		}
+
+		seq_num := uint64(0x0102030405060708)
+
+		got := sdk.DeriveNonce(shared_key, uuid_bytes, salt16, seq_num, false)
+		want := derive_nonce_reference(shared_key, uuid_bytes, salt16, seq_num, false)
+
+		Expect(got).To(Equal(want))
+	})
+
+	It("encrypts and decrypts roundtrip", func() {
+		var shared_key [32]byte
+		for i := 0; i < 32; i++ {
+			shared_key[i] = byte(0x55 ^ i)
+		}
+
+		uuid_bytes, err := sdk.ParseUUIDBytes("cb653f53-6f7d-4aeb-ba0d-d2b17c290d8a")
+		Expect(err).To(BeNil())
+
+		plain_text := []byte("hello ownwire")
+		seq_num := uint64(123)
+
+		enc, err := sdk.EncryptAESGCM(shared_key, uuid_bytes, plain_text, seq_num, false)
+		Expect(err).To(BeNil())
+		Expect(enc.ContentB64).ToNot(BeEmpty())
+		Expect(enc.SaltHex).To(HaveLen(32)) // 16 bytes hex
+
+		out, err := sdk.DecryptAESGCM(shared_key, uuid_bytes, enc.ContentB64, enc.SaltHex, seq_num, false)
+		Expect(err).To(BeNil())
+		Expect(string(out)).To(Equal(string(plain_text)))
+	})
+
+	It("fails decrypt if seq changes", func() {
+		var shared_key [32]byte
+		for i := 0; i < 32; i++ {
+			shared_key[i] = byte(0x11 + i)
+		}
+
+		uuid_bytes, err := sdk.ParseUUIDBytes("cb653f53-6f7d-4aeb-ba0d-d2b17c290d8a")
+		Expect(err).To(BeNil())
+
+		enc, err := sdk.EncryptAESGCM(shared_key, uuid_bytes, []byte("hello"), 1, false)
+		Expect(err).To(BeNil())
+
+		_, err = sdk.DecryptAESGCM(shared_key, uuid_bytes, enc.ContentB64, enc.SaltHex, 2, false)
+		Expect(err).ToNot(BeNil())
+	})
+})
+