From 0968285664ecc3690b41980e08b290198df0d068 Mon Sep 17 00:00:00 2001
From: Andy Wang <cbeuw.andy@gmail.com>
Date: Sun, 18 Oct 2020 00:45:28 +0100
Subject: [PATCH] Improve test coverage

---
 internal/common/crypto_test.go   | 94 ++++++++++++++++++++++++++++++++
 internal/ecdh/curve25519_test.go | 15 +++++
 2 files changed, 109 insertions(+)
 create mode 100644 internal/common/crypto_test.go

diff --git a/internal/common/crypto_test.go b/internal/common/crypto_test.go
new file mode 100644
index 0000000..4f8a186
--- /dev/null
+++ b/internal/common/crypto_test.go
@@ -0,0 +1,94 @@
+package common
+
+import (
+	"bytes"
+	"encoding/hex"
+	"errors"
+	"github.com/stretchr/testify/assert"
+	"io"
+	"math/rand"
+	"testing"
+)
+
+const gcmTagSize = 16
+
+func TestAESGCM(t *testing.T) {
+	// test vectors from https://luca-giuzzi.unibs.it/corsi/Support/papers-cryptography/gcm-spec.pdf
+	t.Run("correct 128", func(t *testing.T) {
+		key, _ := hex.DecodeString("00000000000000000000000000000000")
+		plaintext, _ := hex.DecodeString("")
+		nonce, _ := hex.DecodeString("000000000000000000000000")
+		ciphertext, _ := hex.DecodeString("")
+		tag, _ := hex.DecodeString("58e2fccefa7e3061367f1d57a4e7455a")
+
+		encryptedWithTag, err := AESGCMEncrypt(nonce, key, plaintext)
+		assert.NoError(t, err)
+		assert.Equal(t, ciphertext, encryptedWithTag[:len(plaintext)])
+		assert.Equal(t, tag, encryptedWithTag[len(plaintext):len(plaintext)+gcmTagSize])
+
+		decrypted, err := AESGCMDecrypt(nonce, key, encryptedWithTag)
+		assert.NoError(t, err)
+		// slight inconvenience here that assert.Equal does not consider a nil slice and an empty slice to be
+		// equal. decrypted should be []byte(nil) but plaintext is []byte{}
+		assert.True(t, bytes.Equal(plaintext, decrypted))
+	})
+	t.Run("bad key size", func(t *testing.T) {
+		key, _ := hex.DecodeString("0000000000000000000000000000")
+		plaintext, _ := hex.DecodeString("")
+		nonce, _ := hex.DecodeString("000000000000000000000000")
+		ciphertext, _ := hex.DecodeString("")
+		tag, _ := hex.DecodeString("58e2fccefa7e3061367f1d57a4e7455a")
+
+		_, err := AESGCMEncrypt(nonce, key, plaintext)
+		assert.Error(t, err)
+
+		_, err = AESGCMDecrypt(nonce, key, append(ciphertext, tag...))
+		assert.Error(t, err)
+	})
+	t.Run("bad nonce size", func(t *testing.T) {
+		key, _ := hex.DecodeString("00000000000000000000000000000000")
+		plaintext, _ := hex.DecodeString("")
+		nonce, _ := hex.DecodeString("00000000000000000000")
+		ciphertext, _ := hex.DecodeString("")
+		tag, _ := hex.DecodeString("58e2fccefa7e3061367f1d57a4e7455a")
+
+		_, err := AESGCMEncrypt(nonce, key, plaintext)
+		assert.Error(t, err)
+
+		_, err = AESGCMDecrypt(nonce, key, append(ciphertext, tag...))
+		assert.Error(t, err)
+	})
+	t.Run("bad tag", func(t *testing.T) {
+		key, _ := hex.DecodeString("00000000000000000000000000000000")
+		nonce, _ := hex.DecodeString("00000000000000000000")
+		ciphertext, _ := hex.DecodeString("")
+		tag, _ := hex.DecodeString("fffffccefa7e3061367f1d57a4e745ff")
+
+		_, err := AESGCMDecrypt(nonce, key, append(ciphertext, tag...))
+		assert.Error(t, err)
+	})
+}
+
+type failingReader struct {
+	fails  int
+	reader io.Reader
+}
+
+func (f *failingReader) Read(p []byte) (n int, err error) {
+	if f.fails > 0 {
+		f.fails -= 1
+		return 0, errors.New("no data for you yet")
+	} else {
+		return f.reader.Read(p)
+	}
+}
+
+func TestRandRead(t *testing.T) {
+	failer := &failingReader{
+		fails:  3,
+		reader: rand.New(rand.NewSource(0)),
+	}
+	readBuf := make([]byte, 10)
+	RandRead(failer, readBuf)
+	assert.NotEqual(t, [10]byte{}, readBuf)
+}
diff --git a/internal/ecdh/curve25519_test.go b/internal/ecdh/curve25519_test.go
index a0330b3..8e9a1c1 100644
--- a/internal/ecdh/curve25519_test.go
+++ b/internal/ecdh/curve25519_test.go
@@ -32,6 +32,7 @@ import (
 	"bytes"
 	"crypto"
 	"crypto/rand"
+	"io"
 	"testing"
 )
 
@@ -39,6 +40,20 @@ func TestCurve25519(t *testing.T) {
 	testECDH(t)
 }
 
+func TestErrors(t *testing.T) {
+	reader, writer := io.Pipe()
+	_ = writer.Close()
+	_, _, err := GenerateKey(reader)
+	if err == nil {
+		t.Error("GenerateKey should return error")
+	}
+
+	_, ok := Unmarshal([]byte{1})
+	if ok {
+		t.Error("Unmarshal should return false")
+	}
+}
+
 func BenchmarkCurve25519(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		testECDH(b)