stupidgcm: add chacha20poly1305 via openssl

"stupidChacha20poly1305".

XChaCha will build upon this.

1 files changed, 171 insertions, 0 deletions

diff --git a/internal/stupidgcm/stupidchacha_test.go b/internal/stupidgcm/stupidchacha_test.go
new file mode 100644
index 0000000..010055f
--- /dev/null
+++ b/internal/stupidgcm/stupidchacha_test.go
@@ -0,0 +1,171 @@
+// +build !without_openssl
+
+// We compare against Go's built-in GCM implementation. Since stupidgcm only
+// supports 128-bit IVs and Go only supports that from 1.5 onward, we cannot
+// run these tests on older Go versions.
+package stupidgcm
+
+import (
+	"bytes"
+	"encoding/hex"
+	"testing"
+
+	"golang.org/x/crypto/chacha20poly1305"
+)
+
+// TestEncryptDecrypt encrypts and decrypts using both stupidgcm and Go's built-in
+// GCM implementation and verifies that the results are identical.
+func TestEncryptDecryptChacha(t *testing.T) {
+	key := randBytes(32)
+	sGCM := newChacha20poly1305(key)
+	authData := randBytes(24)
+	iv := randBytes(sGCM.NonceSize())
+	dst := make([]byte, 71) // 71 = random length
+
+	gGCM, err := chacha20poly1305.New(key)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Check all block sizes from 1 to 5000
+	for i := 1; i < 5000; i++ {
+		in := make([]byte, i)
+
+		sOut := sGCM.Seal(dst, iv, in, authData)
+		gOut := gGCM.Seal(dst, iv, in, authData)
+
+		// Ciphertext must be identical to Go GCM
+		if !bytes.Equal(sOut, gOut) {
+			t.Fatalf("Compare failed for encryption, size %d", i)
+			t.Log("sOut:")
+			t.Log("\n" + hex.Dump(sOut))
+			t.Log("gOut:")
+			t.Log("\n" + hex.Dump(gOut))
+		}
+
+		sOut2, sErr := sGCM.Open(dst, iv, sOut[len(dst):], authData)
+		if sErr != nil {
+			t.Fatal(sErr)
+		}
+		gOut2, gErr := gGCM.Open(dst, iv, gOut[len(dst):], authData)
+		if gErr != nil {
+			t.Fatal(gErr)
+		}
+
+		// Plaintext must be identical to Go GCM
+		if !bytes.Equal(sOut2, gOut2) {
+			t.Fatalf("Compare failed for decryption, size %d", i)
+		}
+	}
+}
+
+// Seal re-uses the "dst" buffer it is large enough.
+// Check that this works correctly by testing different "dst" capacities from
+// 5000 to 16 and "in" lengths from 1 to 5000.
+func TestInplaceSealChacha(t *testing.T) {
+	key := randBytes(32)
+	sGCM := newChacha20poly1305(key)
+	authData := randBytes(24)
+	iv := randBytes(sGCM.NonceSize())
+
+	gGCM, err := chacha20poly1305.New(key)
+	if err != nil {
+		t.Fatal(err)
+	}
+	max := 5016
+	// Check all block sizes from 1 to 5000
+	for i := 1; i < max-len(iv); i++ {
+		in := make([]byte, i)
+		dst := make([]byte, max-i)
+		dst = dst[:len(iv)]
+
+		sOut := sGCM.Seal(dst, iv, in, authData)
+		dst2 := make([]byte, len(iv))
+		gOut := gGCM.Seal(dst2, iv, in, authData)
+
+		// Ciphertext must be identical to Go GCM
+		if !bytes.Equal(sOut, gOut) {
+			t.Fatalf("Compare failed for encryption, size %d", i)
+			t.Log("sOut:")
+			t.Log("\n" + hex.Dump(sOut))
+			t.Log("gOut:")
+			t.Log("\n" + hex.Dump(gOut))
+		}
+	}
+}
+
+// Open re-uses the "dst" buffer it is large enough.
+// Check that this works correctly by testing different "dst" capacities from
+// 5000 to 16 and "in" lengths from 1 to 5000.
+func TestInplaceOpenChacha(t *testing.T) {
+	key := randBytes(32)
+	sGCM := newChacha20poly1305(key)
+	authData := randBytes(24)
+	iv := randBytes(sGCM.NonceSize())
+
+	gGCM, err := chacha20poly1305.New(key)
+	if err != nil {
+		t.Fatal(err)
+	}
+	max := 5016
+	// Check all block sizes from 1 to 5000
+	for i := 1; i < max-len(iv); i++ {
+		in := make([]byte, i)
+
+		gCiphertext := gGCM.Seal(iv, iv, in, authData)
+
+		dst := make([]byte, max-i)
+		// sPlaintext ... stupidgcm plaintext
+		sPlaintext, err := sGCM.Open(dst[:0], iv, gCiphertext[len(iv):], authData)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		// Plaintext must be identical to Go GCM
+		if !bytes.Equal(in, sPlaintext) {
+			t.Fatalf("Compare failed, i=%d", i)
+		}
+	}
+}
+
+// TestCorruption verifies that changes in the ciphertext result in a decryption
+// error
+func TestCorruptionChacha(t *testing.T) {
+	key := randBytes(32)
+	sGCM := newChacha20poly1305(key)
+	authData := randBytes(24)
+	iv := randBytes(sGCM.NonceSize())
+
+	in := make([]byte, 354)
+	sOut := sGCM.Seal(nil, iv, in, authData)
+	sOut2, sErr := sGCM.Open(nil, iv, sOut, authData)
+	if sErr != nil {
+		t.Fatal(sErr)
+	}
+	if !bytes.Equal(in, sOut2) {
+		t.Fatalf("Compare failed")
+	}
+
+	// Corrupt first byte
+	sOut[0]++
+	sOut2, sErr = sGCM.Open(nil, iv, sOut, authData)
+	if sErr == nil || sOut2 != nil {
+		t.Fatalf("Should have gotten error")
+	}
+	sOut[0]--
+
+	// Corrupt last byte
+	sOut[len(sOut)-1]++
+	sOut2, sErr = sGCM.Open(nil, iv, sOut, authData)
+	if sErr == nil || sOut2 != nil {
+		t.Fatalf("Should have gotten error")
+	}
+	sOut[len(sOut)-1]--
+
+	// Append one byte
+	sOut = append(sOut, 0)
+	sOut2, sErr = sGCM.Open(nil, iv, sOut, authData)
+	if sErr == nil || sOut2 != nil {
+		t.Fatalf("Should have gotten error")
+	}
+}