1 files changed, 22 insertions, 0 deletions
diff --git a/libgo/go/crypto/cipher/cbc.go b/libgo/go/crypto/cipher/cbc.go
index 241e122..0367d59 100644
--- a/libgo/go/crypto/cipher/cbc.go
+++ b/libgo/go/crypto/cipher/cbc.go
@@ -29,6 +29,14 @@ func newCBC(b Block, iv []byte) *cbc {
 
 type cbcEncrypter cbc
 
+// cbcEncAble is an interface implemented by ciphers that have a specific
+// optimized implementation of CBC encryption, like crypto/aes.
+// NewCBCEncrypter will check for this interface and return the specific
+// BlockMode if found.
+type cbcEncAble interface {
+	NewCBCEncrypter(iv []byte) BlockMode
+}
+
 // NewCBCEncrypter returns a BlockMode which encrypts in cipher block chaining
 // mode, using the given Block. The length of iv must be the same as the
 // Block's block size.
@@ -36,6 +44,9 @@ func NewCBCEncrypter(b Block, iv []byte) BlockMode {
 	if len(iv) != b.BlockSize() {
 		panic("cipher.NewCBCEncrypter: IV length must equal block size")
 	}
+	if cbc, ok := b.(cbcEncAble); ok {
+		return cbc.NewCBCEncrypter(iv)
+	}
 	return (*cbcEncrypter)(newCBC(b, iv))
 }
 
@@ -75,6 +86,14 @@ func (x *cbcEncrypter) SetIV(iv []byte) {
 
 type cbcDecrypter cbc
 
+// cbcDecAble is an interface implemented by ciphers that have a specific
+// optimized implementation of CBC decryption, like crypto/aes.
+// NewCBCDecrypter will check for this interface and return the specific
+// BlockMode if found.
+type cbcDecAble interface {
+	NewCBCDecrypter(iv []byte) BlockMode
+}
+
 // NewCBCDecrypter returns a BlockMode which decrypts in cipher block chaining
 // mode, using the given Block. The length of iv must be the same as the
 // Block's block size and must match the iv used to encrypt the data.
@@ -82,6 +101,9 @@ func NewCBCDecrypter(b Block, iv []byte) BlockMode {
 	if len(iv) != b.BlockSize() {
 		panic("cipher.NewCBCDecrypter: IV length must equal block size")
 	}
+	if cbc, ok := b.(cbcDecAble); ok {
+		return cbc.NewCBCDecrypter(iv)
+	}
 	return (*cbcDecrypter)(newCBC(b, iv))
 }