Implement "gocryptfs -speed"

A crypto benchmark mode like "openssl speed".

Example run:

  $ ./gocryptfs -speed
  AES-GCM-256-OpenSSL 	 180.89 MB/s	(selected in auto mode)
  AES-GCM-256-Go      	  48.19 MB/s
  AES-SIV-512-Go      	  37.40 MB/s

1 files changed, 120 insertions, 0 deletions

diff --git a/internal/speed/speed.go b/internal/speed/speed.go
new file mode 100644
index 0000000..f9bf93c
--- /dev/null
+++ b/internal/speed/speed.go
@@ -0,0 +1,120 @@
+// Package speed implements the "-speed" command-line option,
+// similar to "openssl speed".
+// It benchmarks the crypto algorithms and libraries used by
+// gocryptfs.
+package speed
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"fmt"
+	"log"
+	"testing"
+
+	"github.com/rfjakob/gocryptfs/internal/prefer_openssl"
+	"github.com/rfjakob/gocryptfs/internal/siv_aead"
+	"github.com/rfjakob/gocryptfs/internal/stupidgcm"
+)
+
+func Run() {
+	bTable := []struct {
+		name      string
+		f         func(*testing.B)
+		preferred bool
+	}{
+		{name: "AES-GCM-256-OpenSSL", f: bStupidGCM, preferred: prefer_openssl.PreferOpenSSL()},
+		{name: "AES-GCM-256-Go", f: bGoGCM, preferred: !prefer_openssl.PreferOpenSSL()},
+		{name: "AES-SIV-512-Go", f: bAESSIV, preferred: false},
+	}
+	for _, b := range bTable {
+		fmt.Printf("%-20s\t", b.name)
+		mbs := mbPerSec(testing.Benchmark(b.f))
+		if mbs > 0 {
+			fmt.Printf("%7.2f MB/s", mbs)
+		} else {
+			fmt.Printf("    N/A")
+		}
+		if b.preferred {
+			fmt.Printf("\t(selected in auto mode)\n")
+		} else {
+			fmt.Printf("\t\n")
+		}
+	}
+}
+
+func mbPerSec(r testing.BenchmarkResult) float64 {
+	if r.Bytes <= 0 || r.T <= 0 || r.N <= 0 {
+		return 0
+	}
+	return (float64(r.Bytes) * float64(r.N) / 1e6) / r.T.Seconds()
+}
+
+// Get "n" random bytes from /dev/urandom or panic
+func randBytes(n int) []byte {
+	b := make([]byte, n)
+	_, err := rand.Read(b)
+	if err != nil {
+		log.Panic("Failed to read random bytes: " + err.Error())
+	}
+	return b
+}
+
+const blockSize = 4096
+
+func bStupidGCM(b *testing.B) {
+	if stupidgcm.BuiltWithoutOpenssl {
+		b.Skip("openssl has been disabled at compile-time")
+	}
+	key := randBytes(32)
+	authData := randBytes(24)
+	iv := randBytes(16)
+	in := make([]byte, blockSize)
+	b.SetBytes(int64(len(in)))
+
+	sGCM := stupidgcm.New(key)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		// Encrypt and append to nonce
+		sGCM.Seal(iv, iv, in, authData)
+	}
+}
+
+func bGoGCM(b *testing.B) {
+	key := randBytes(32)
+	authData := randBytes(24)
+	iv := randBytes(16)
+	in := make([]byte, blockSize)
+	b.SetBytes(int64(len(in)))
+
+	gAES, err := aes.NewCipher(key)
+	if err != nil {
+		b.Fatal(err)
+	}
+	gGCM, err := cipher.NewGCMWithNonceSize(gAES, 16)
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		// Encrypt and append to nonce
+		gGCM.Seal(iv, iv, in, authData)
+	}
+}
+
+func bAESSIV(b *testing.B) {
+	key := randBytes(64)
+	authData := randBytes(24)
+	iv := randBytes(16)
+	in := make([]byte, blockSize)
+	b.SetBytes(int64(len(in)))
+	gGCM := siv_aead.New(key)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		// Encrypt and append to nonce
+		gGCM.Seal(iv, iv, in, authData)
+	}
+}