stupidgcm: deduplicate tests 1/2

Pull the code shared between chacha and gcm into
generic functions.

3 files changed, 167 insertions, 230 deletions

diff --git a/internal/stupidgcm/common_test.go b/internal/stupidgcm/common_test.go
new file mode 100644
index 0000000..28f3308
--- /dev/null
+++ b/internal/stupidgcm/common_test.go
@@ -0,0 +1,152 @@
+package stupidgcm
+
+import (
+	"bytes"
+	"crypto/cipher"
+	"encoding/hex"
+	"testing"
+)
+
+// testEncryptDecrypt encrypts and decrypts using both stupidgcm and Go's built-in
+// GCM implementation and verifies that the results are identical.
+func testEncryptDecrypt(t *testing.T, c1 cipher.AEAD, c2 cipher.AEAD) {
+	if c1.NonceSize() != c2.NonceSize() {
+		t.Fatal("different NonceSize")
+	}
+	if c1.Overhead() != c2.Overhead() {
+		t.Fatal("different Overhead")
+	}
+
+	authData := randBytes(24)
+	iv := randBytes(c1.NonceSize())
+
+	dst := make([]byte, 71) // 71 = arbitrary length
+
+	// Check all block sizes from 1 to 5000
+	for i := 1; i < 5000; i++ {
+		in := make([]byte, i)
+
+		c1out := c1.Seal(dst, iv, in, authData)
+		c2out := c2.Seal(dst, iv, in, authData)
+
+		// Ciphertext must be identical to Go GCM
+		if !bytes.Equal(c1out, c2out) {
+			t.Fatalf("Compare failed for encryption, size %d", i)
+			t.Log("c1out:")
+			t.Log("\n" + hex.Dump(c1out))
+			t.Log("c2out:")
+			t.Log("\n" + hex.Dump(c2out))
+		}
+
+		c1out2, sErr := c1.Open(dst, iv, c1out[len(dst):], authData)
+		if sErr != nil {
+			t.Fatal(sErr)
+		}
+		c2out2, gErr := c2.Open(dst, iv, c2out[len(dst):], authData)
+		if gErr != nil {
+			t.Fatal(gErr)
+		}
+
+		// Plaintext must be identical to Go GCM
+		if !bytes.Equal(c1out2, c2out2) {
+			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 testInplaceSeal(t *testing.T, c1 cipher.AEAD, c2 cipher.AEAD) {
+	authData := randBytes(24)
+	iv := randBytes(c1.NonceSize())
+
+	max := 5016
+	// Check all block sizes from 1 to 5000
+	for i := 1; i < max-16; i++ {
+		in := make([]byte, i)
+		dst := make([]byte, max-i)
+		dst = dst[:16]
+
+		c1out := c1.Seal(dst, iv, in, authData)
+		dst2 := make([]byte, 16)
+		c2out := c2.Seal(dst2, iv, in, authData)
+
+		// Ciphertext must be identical to Go GCM
+		if !bytes.Equal(c1out, c2out) {
+			t.Fatalf("Compare failed for encryption, size %d", i)
+			t.Log("sOut:")
+			t.Log("\n" + hex.Dump(c1out))
+			t.Log("gOut:")
+			t.Log("\n" + hex.Dump(c2out))
+		}
+	}
+}
+
+// testInplaceOpen - 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 testInplaceOpen(t *testing.T, c1 cipher.AEAD, c2 cipher.AEAD) {
+	authData := randBytes(24)
+	iv := randBytes(c1.NonceSize())
+
+	max := 5016
+	// Check all block sizes from 1 to 5000
+	for i := 1; i < max-c1.NonceSize(); i++ {
+		in := make([]byte, i)
+
+		c2ciphertext := c2.Seal(iv, iv, in, authData)
+
+		dst := make([]byte, max-i)
+		// sPlaintext ... stupidgcm plaintext
+		c1plaintext, err := c1.Open(dst[:0], iv, c2ciphertext[c1.NonceSize():], authData)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		// Plaintext must be identical to Go GCM
+		if !bytes.Equal(in, c1plaintext) {
+			t.Fatalf("Compare failed, i=%d", i)
+		}
+	}
+}
+
+// testCorruption verifies that changes in the ciphertext result in a decryption
+// error
+func testCorruption(t *testing.T, c cipher.AEAD) {
+	authData := randBytes(24)
+	iv := randBytes(c.NonceSize())
+
+	in := make([]byte, 354)
+	out := c.Seal(nil, iv, in, authData)
+	out2, sErr := c.Open(nil, iv, out, authData)
+	if sErr != nil {
+		t.Fatal(sErr)
+	}
+	if !bytes.Equal(in, out2) {
+		t.Fatalf("Compare failed")
+	}
+
+	// Corrupt first byte
+	out[0]++
+	out2, sErr = c.Open(nil, iv, out, authData)
+	if sErr == nil || out2 != nil {
+		t.Fatalf("Should have gotten error")
+	}
+	out[0]--
+
+	// Corrupt last byte
+	out[len(out)-1]++
+	out2, sErr = c.Open(nil, iv, out, authData)
+	if sErr == nil || out2 != nil {
+		t.Fatalf("Should have gotten error")
+	}
+	out[len(out)-1]--
+
+	// Append one byte
+	out = append(out, 0)
+	out2, sErr = c.Open(nil, iv, out, authData)
+	if sErr == nil || out2 != nil {
+		t.Fatalf("Should have gotten error")
+	}
+}
diff --git a/internal/stupidgcm/stupidchacha_test.go b/internal/stupidgcm/stupidchacha_test.go
index 010055f..c1086d1 100644
--- a/internal/stupidgcm/stupidchacha_test.go
+++ b/internal/stupidgcm/stupidchacha_test.go
@@ -6,8 +6,6 @@
 package stupidgcm
 
 import (
-	"bytes"
-	"encoding/hex"
 	"testing"
 
 	"golang.org/x/crypto/chacha20poly1305"
@@ -17,46 +15,13 @@ import (
 // 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)
+	c := newChacha20poly1305(key)
+	ref, 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)
-		}
-	}
+	testEncryptDecrypt(t, c, ref)
 }
 
 // Seal re-uses the "dst" buffer it is large enough.
@@ -64,34 +29,13 @@ func TestEncryptDecryptChacha(t *testing.T) {
 // 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)
+	c := newChacha20poly1305(key)
+	ref, 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))
-		}
-	}
+	testInplaceSeal(t, c, ref)
 }
 
 // Open re-uses the "dst" buffer it is large enough.
@@ -99,73 +43,20 @@ func TestInplaceSealChacha(t *testing.T) {
 // 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)
+	c := newChacha20poly1305(key)
+	ref, 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)
-		}
-	}
+	testInplaceOpen(t, c, ref)
 }
 
 // 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")
-	}
+	c := newChacha20poly1305(key)
 
-	// 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")
-	}
+	testCorruption(t, c)
 }
diff --git a/internal/stupidgcm/stupidgcm_test.go b/internal/stupidgcm/stupidgcm_test.go
index 18732df..968034e 100644
--- a/internal/stupidgcm/stupidgcm_test.go
+++ b/internal/stupidgcm/stupidgcm_test.go
@@ -6,11 +6,9 @@
 package stupidgcm
 
 import (
-	"bytes"
 	"crypto/aes"
 	"crypto/cipher"
 	"crypto/rand"
-	"encoding/hex"
 	"log"
 	"testing"
 )
@@ -30,9 +28,6 @@ func randBytes(n int) []byte {
 func TestEncryptDecrypt(t *testing.T) {
 	key := randBytes(32)
 	sGCM := New(key, false)
-	authData := randBytes(24)
-	iv := randBytes(16)
-	dst := make([]byte, 71) // 71 = random length
 
 	gAES, err := aes.NewCipher(key)
 	if err != nil {
@@ -43,36 +38,7 @@ func TestEncryptDecrypt(t *testing.T) {
 		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)
-		}
-	}
+	testEncryptDecrypt(t, sGCM, gGCM)
 }
 
 // Seal re-uses the "dst" buffer it is large enough.
@@ -81,8 +47,6 @@ func TestEncryptDecrypt(t *testing.T) {
 func TestInplaceSeal(t *testing.T) {
 	key := randBytes(32)
 	sGCM := New(key, false)
-	authData := randBytes(24)
-	iv := randBytes(16)
 
 	gAES, err := aes.NewCipher(key)
 	if err != nil {
@@ -92,26 +56,8 @@ func TestInplaceSeal(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	max := 5016
-	// Check all block sizes from 1 to 5000
-	for i := 1; i < max-16; i++ {
-		in := make([]byte, i)
-		dst := make([]byte, max-i)
-		dst = dst[:16]
 
-		sOut := sGCM.Seal(dst, iv, in, authData)
-		dst2 := make([]byte, 16)
-		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))
-		}
-	}
+	testInplaceSeal(t, sGCM, gGCM)
 }
 
 // Open re-uses the "dst" buffer it is large enough.
@@ -120,8 +66,6 @@ func TestInplaceSeal(t *testing.T) {
 func TestInplaceOpen(t *testing.T) {
 	key := randBytes(32)
 	sGCM := New(key, false)
-	authData := randBytes(24)
-	iv := randBytes(16)
 
 	gAES, err := aes.NewCipher(key)
 	if err != nil {
@@ -131,25 +75,8 @@ func TestInplaceOpen(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	max := 5016
-	// Check all block sizes from 1 to 5000
-	for i := 1; i < max-16; 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[16:], 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)
-		}
-	}
+	testInplaceOpen(t, sGCM, gGCM)
 }
 
 // TestCorruption verifies that changes in the ciphertext result in a decryption
@@ -157,39 +84,6 @@ func TestInplaceOpen(t *testing.T) {
 func TestCorruption(t *testing.T) {
 	key := randBytes(32)
 	sGCM := New(key, false)
-	authData := randBytes(24)
-	iv := randBytes(16)
 
-	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")
-	}
+	testCorruption(t, sGCM)
 }