Add openssl benchmark

Results:

  BenchmarkAESGCMSeal4K   	   20000	     98638 ns/op	  41.53 MB/s
  BenchmarkAESGCMOpen4K   	   20000	     98781 ns/op	  41.47 MB/s
  BenchmarkOpensslGCMenc4K	   50000	     27563 ns/op	 148.60 MB/s
  BenchmarkOpensslGCMdec4K	   50000	     27563 ns/op	 148.60 MB/s

openssl is 3x faster.

benchmark/openssl_test.go

@@ -0,0 +1,140 @@
+package benchmark
+
+// Benchmark go built-int GCM against spacemonkey openssl bindings
+//
+// Run benchmark:
+// go test -bench=.
+
+import (
+	"bytes"
+	"testing"
+	"github.com/spacemonkeygo/openssl"
+	"crypto/aes"
+	"crypto/cipher"
+)
+
+func BenchmarkAESGCMSeal4K(b *testing.B) {
+	buf := make([]byte, 1024*4)
+	b.SetBytes(int64(len(buf)))
+
+	var key [16]byte
+	var nonce [12]byte
+	aes, _ := aes.NewCipher(key[:])
+	aesgcm, _ := cipher.NewGCM(aes)
+	var out []byte
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		out = aesgcm.Seal(out[:0], nonce[:], buf, nil)
+	}
+}
+
+func BenchmarkAESGCMOpen4K(b *testing.B) {
+	buf := make([]byte, 1024*4)
+	b.SetBytes(int64(len(buf)))
+
+	var key [16]byte
+	var nonce [12]byte
+	aes, _ := aes.NewCipher(key[:])
+	aesgcm, _ := cipher.NewGCM(aes)
+	var out []byte
+	out = aesgcm.Seal(out[:0], nonce[:], buf, nil)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, err := aesgcm.Open(buf[:0], nonce[:], out, nil)
+		if err != nil {
+			b.Errorf("Open: %v", err)
+		}
+	}
+}
+
+func BenchmarkOpensslGCMenc4K(b *testing.B) {
+	buf := make([]byte, 1024*4)
+	b.SetBytes(int64(len(buf)))
+
+	var key [16]byte
+	var nonce [12]byte
+
+	var ciphertext bytes.Buffer
+	var part []byte
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		ciphertext.Reset()
+		ectx, err := openssl.NewGCMEncryptionCipherCtx(128, nil, key[:], nonce[:])
+		if err != nil {
+			b.FailNow()
+		}
+		part, err = ectx.EncryptUpdate(buf)
+		if err != nil {
+			b.FailNow()
+		}
+		ciphertext.Write(part)
+		part, err = ectx.EncryptFinal()
+		if err != nil {
+			b.FailNow()
+		}
+		ciphertext.Write(part)
+		part, err = ectx.GetTag()
+		if err != nil {
+			b.FailNow()
+		}
+		ciphertext.Write(part)
+	}
+}
+
+func BenchmarkOpensslGCMdec4K(b *testing.B) {
+	buf := makeOpensslCiphertext()
+	b.SetBytes(int64(1024*4))
+
+	tag := buf[4096:]
+	buf = buf[0:4096]
+
+	var key [16]byte
+	var nonce [12]byte
+
+	var plaintext bytes.Buffer
+	var part []byte
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		plaintext.Reset()
+		dctx, err := openssl.NewGCMDecryptionCipherCtx(128, nil, key[:], nonce[:])
+		if err != nil {
+			b.FailNow()
+		}
+		part, err = dctx.DecryptUpdate(buf)
+		if err != nil {
+			b.FailNow()
+		}
+		plaintext.Write(part)
+		err = dctx.SetTag(tag)
+		if err != nil {
+			b.FailNow()
+		}
+		part, err = dctx.DecryptFinal()
+		if err != nil {
+			b.FailNow()
+		}
+		plaintext.Write(part)
+	}
+}
+
+func makeOpensslCiphertext() []byte {
+	buf := make([]byte, 1024*4)
+	var key [16]byte
+	var nonce [12]byte
+	var ciphertext bytes.Buffer
+	var part []byte
+
+	ectx, _ := openssl.NewGCMEncryptionCipherCtx(128, nil, key[:], nonce[:])
+	part, _ = ectx.EncryptUpdate(buf)
+	ciphertext.Write(part)
+	part, _ = ectx.EncryptFinal()
+	ciphertext.Write(part)
+	part, _ = ectx.GetTag()
+	ciphertext.Write(part)
+
+	return ciphertext.Bytes()
+}