stupidgcm: introduce stupidAEADCommon and use for both chacha & gcm

Nice deduplication and brings the GCM decrypt speed up to par.

internal/speed$ benchstat old new
name                old time/op   new time/op   delta
StupidGCM-4          4.71µs ± 0%   4.66µs ± 0%   -0.99%  (p=0.008 n=5+5)
StupidGCMDecrypt-4   5.77µs ± 1%   4.51µs ± 0%  -21.80%  (p=0.008 n=5+5)

name                old speed     new speed     delta
StupidGCM-4         870MB/s ± 0%  879MB/s ± 0%   +1.01%  (p=0.008 n=5+5)
StupidGCMDecrypt-4  710MB/s ± 1%  908MB/s ± 0%  +27.87%  (p=0.008 n=5+5)

1 files changed, 0 insertions, 156 deletions

diff --git a/internal/stupidgcm/stupidchacha.go b/internal/stupidgcm/stupidchacha.go
deleted file mode 100644
index 5073aa3..0000000
--- a/internal/stupidgcm/stupidchacha.go
+++ /dev/null
@@ -1,156 +0,0 @@
-// +build !without_openssl
-
-package stupidgcm
-
-import (
-	"crypto/cipher"
-	"fmt"
-	"log"
-
-	"golang.org/x/crypto/chacha20poly1305"
-)
-
-/*
-#include <openssl/evp.h>
-#include "chacha.h"
-#cgo pkg-config: libcrypto
-*/
-import "C"
-
-type stupidChacha20poly1305 struct {
-	key   [chacha20poly1305.KeySize]byte
-	wiped bool
-}
-
-// Verify that we satisfy the cipher.AEAD interface
-var _ cipher.AEAD = &stupidChacha20poly1305{}
-
-func newChacha20poly1305(key []byte) cipher.AEAD {
-	if len(key) != chacha20poly1305.KeySize {
-		log.Panicf("Only %d-byte keys are supported, you passed %d bytes", chacha20poly1305.KeySize, len(key))
-	}
-	ret := new(stupidChacha20poly1305)
-	copy(ret.key[:], key)
-	return ret
-}
-
-// NonceSize returns the required size of the nonce / IV.
-func (g *stupidChacha20poly1305) NonceSize() int {
-	return chacha20poly1305.NonceSize
-}
-
-// Overhead returns the number of bytes that are added for authentication.
-func (g *stupidChacha20poly1305) Overhead() int {
-	return tagLen
-}
-
-// Seal encrypts "in" using "iv" and "authData" and append the result to "dst"
-func (g *stupidChacha20poly1305) Seal(dst, iv, in, authData []byte) []byte {
-	if g.wiped {
-		panic("BUG: tried to use wiped key")
-	}
-	if len(iv) != g.NonceSize() {
-		log.Panicf("Only %d-byte IVs are supported, you passed %d bytes", g.NonceSize(), len(iv))
-	}
-	if len(in) == 0 {
-		log.Panic("Zero-length input data is not supported")
-	}
-	if len(g.key) != chacha20poly1305.KeySize {
-		log.Panicf("Wrong key length: %d. Key has been wiped?", len(g.key))
-	}
-
-	// If the "dst" slice is large enough we can use it as our output buffer
-	outLen := len(in) + tagLen
-	var buf []byte
-	inplace := false
-	if cap(dst)-len(dst) >= outLen {
-		inplace = true
-		buf = dst[len(dst) : len(dst)+outLen]
-	} else {
-		buf = make([]byte, outLen)
-	}
-
-	C.aead_seal(C.aeadTypeChacha,
-		(*C.uchar)(&in[0]),
-		C.int(len(in)),
-		(*C.uchar)(&authData[0]),
-		C.int(len(authData)),
-		(*C.uchar)(&g.key[0]),
-		C.int(len(g.key)),
-		(*C.uchar)(&iv[0]),
-		C.int(len(iv)),
-		(*C.uchar)(&buf[0]),
-		C.int(len(buf)))
-
-	if inplace {
-		return dst[:len(dst)+outLen]
-	}
-	return append(dst, buf...)
-}
-
-// Open decrypts "in" using "iv" and "authData" and append the result to "dst"
-func (g *stupidChacha20poly1305) Open(dst, iv, in, authData []byte) ([]byte, error) {
-	if g.wiped {
-		panic("BUG: tried to use wiped key")
-	}
-	if len(iv) != g.NonceSize() {
-		log.Panicf("Only %d-byte IVs are supported", g.NonceSize())
-	}
-	if len(g.key) != chacha20poly1305.KeySize {
-		log.Panicf("Wrong key length: %d. Key has been wiped?", len(g.key))
-	}
-	if len(in) <= tagLen {
-		return nil, fmt.Errorf("stupidChacha20poly1305: input data too short (%d bytes)", len(in))
-	}
-
-	// If the "dst" slice is large enough we can use it as our output buffer
-	outLen := len(in) - tagLen
-	var buf []byte
-	inplace := false
-	if cap(dst)-len(dst) >= outLen {
-		inplace = true
-		buf = dst[len(dst) : len(dst)+outLen]
-	} else {
-		buf = make([]byte, len(in)-tagLen)
-	}
-
-	ciphertext := in[:len(in)-tagLen]
-	tag := in[len(in)-tagLen:]
-
-	res := int(C.aead_open(C.aeadTypeChacha,
-		(*C.uchar)(&ciphertext[0]),
-		C.int(len(ciphertext)),
-		(*C.uchar)(&authData[0]),
-		C.int(len(authData)),
-		(*C.uchar)(&tag[0]),
-		C.int(len(tag)),
-		(*C.uchar)(&g.key[0]),
-		C.int(len(g.key)),
-		(*C.uchar)(&iv[0]),
-		C.int(len(iv)),
-		(*C.uchar)(&buf[0]),
-		C.int(len(buf))))
-
-	if res < 0 {
-		return nil, ErrAuth
-	}
-	if res != outLen {
-		log.Panicf("unexpected length %d", res)
-	}
-
-	if inplace {
-		return dst[:len(dst)+outLen], nil
-	}
-	return append(dst, buf...), nil
-}
-
-// Wipe tries to wipe the key from memory by overwriting it with zeros.
-//
-// This is not bulletproof due to possible GC copies, but
-// still raises the bar for extracting the key.
-func (g *stupidChacha20poly1305) Wipe() {
-	g.wiped = true
-	for i := range g.key {
-		g.key[i] = 0
-	}
-}