crypto/internal/boring: use noescape and nocallback cgo directives

The new noescape and nocallback directives can be used instead of the C
wrapper functions that are there just to avoid some parameters being
escaped to the heap.

This CL also helps demonstrate the use of the new directives in real
code.

I've added some benchmarks to demonstrate that this CL doesn't
introduce new heap allocations when using boringcrypto:

```
goos: linux
goarch: amd64
pkg: crypto/aes
cpu: AMD EPYC 7763 64-Core Processor
BenchmarkGCMSeal-32    	 8378692	       143.3 ns/op	 111.65 MB/s	       0 B/op	       0 allocs/op
BenchmarkGCMOpen-32    	 8383038	       142.7 ns/op	 112.11 MB/s	       0 B/op	       0 allocs/op
```

Change-Id: Ifd775484eb9a105afc5c3d4e75a6c6655cbadc53
Reviewed-on: https://go-review.googlesource.com/c/go/+/525035
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/src/crypto/cipher/gcm_test.go b/src/crypto/cipher/gcm_test.go
index 3556146ea6..7b9d1852d7 100644
--- a/src/crypto/cipher/gcm_test.go
+++ b/src/crypto/cipher/gcm_test.go
@@ -654,3 +654,39 @@ func TestGCMAsm(t *testing.T) {
 		}
 	}
 }
+
+func BenchmarkGCMSeal(b *testing.B) {
+	key, _ := hex.DecodeString("ab72c77b97cb5fe9a382d9fe81ffdbed")
+	nonce, _ := hex.DecodeString("54cc7dc2c37ec006bcc6d1db")
+	plaintext, _ := hex.DecodeString("f1cc3818e421876bb6b8bbd6c9")
+
+	aes, _ := aes.NewCipher(key)
+	aesgcm, _ := cipher.NewGCM(aes)
+
+	ciphertext := make([]byte, 32)
+	b.SetBytes(int64(len(plaintext)))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = aesgcm.Seal(ciphertext[:0], nonce, plaintext, nil)
+	}
+}
+
+func BenchmarkGCMOpen(b *testing.B) {
+	key, _ := hex.DecodeString("ab72c77b97cb5fe9a382d9fe81ffdbed")
+	nonce, _ := hex.DecodeString("54cc7dc2c37ec006bcc6d1db")
+	plaintext, _ := hex.DecodeString("f1cc3818e421876bb6b8bbd6c9")
+
+	aes, _ := aes.NewCipher(key)
+	aesgcm, _ := cipher.NewGCM(aes)
+
+	ciphertext := aesgcm.Seal(nil, nonce, plaintext, nil)
+
+	b.SetBytes(int64(len(ciphertext)))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, err := aesgcm.Open(plaintext[:0], nonce, ciphertext, nil)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}