[crypto] Allow creation of arbitrary CBC cipher algorithms using CBC_CIPHER()

Given any block cipher, a corresponding CBC mode of behaviour for the
cipher can be created using the CBC_CIPHER() macro.

1 files changed, 56 insertions, 8 deletions

diff --git a/src/include/gpxe/cbc.h b/src/include/gpxe/cbc.h
index e2d57764..fcc115eb 100644
--- a/src/include/gpxe/cbc.h
+++ b/src/include/gpxe/cbc.h
@@ -15,15 +15,15 @@
  * @v ctx		Context
  * @v key		Key
  * @v keylen		Key length
- * @v cipher		Underlying cipher algorithm
+ * @v raw_cipher	Underlying cipher algorithm
  * @v cbc_ctx		CBC context
  * @ret rc		Return status code
  */
 static inline int cbc_setkey ( void *ctx, const void *key, size_t keylen,
-			       struct cipher_algorithm *cipher,
+			       struct cipher_algorithm *raw_cipher,
 			       void *cbc_ctx __unused ) {
 
-	return cipher_setkey ( cipher, ctx, key, keylen );
+	return cipher_setkey ( raw_cipher, ctx, key, keylen );
 }
 
 /**
@@ -31,20 +31,68 @@ static inline int cbc_setkey ( void *ctx, const void *key, size_t keylen,
  *
  * @v ctx		Context
  * @v iv		Initialisation vector
- * @v cipher		Underlying cipher algorithm
+ * @v raw_cipher	Underlying cipher algorithm
  * @v cbc_ctx		CBC context
  */
 static inline void cbc_setiv ( void *ctx __unused, const void *iv,
-			       struct cipher_algorithm *cipher,
+			       struct cipher_algorithm *raw_cipher,
 			       void *cbc_ctx ) {
-	memcpy ( cbc_ctx, iv, cipher->blocksize );
+	memcpy ( cbc_ctx, iv, raw_cipher->blocksize );
 }
 
 extern void cbc_encrypt ( void *ctx, const void *src, void *dst,
-			  size_t len, struct cipher_algorithm *cipher,
+			  size_t len, struct cipher_algorithm *raw_cipher,
 			  void *cbc_ctx );
 extern void cbc_decrypt ( void *ctx, const void *src, void *dst,
-			  size_t len, struct cipher_algorithm *cipher,
+			  size_t len, struct cipher_algorithm *raw_cipher,
 			  void *cbc_ctx );
 
+/**
+ * Create a cipher-block chaining mode of behaviour of an existing cipher
+ *
+ * @v _cbc_name		Name for the new CBC cipher
+ * @v _cbc_cipher	New cipher algorithm
+ * @v _raw_cipher	Underlying cipher algorithm
+ * @v _raw_context	Context structure for the underlying cipher
+ * @v _blocksize	Cipher block size
+ */
+#define CBC_CIPHER( _cbc_name, _cbc_cipher, _raw_cipher, _raw_context,	\
+		    _blocksize )					\
+struct _cbc_name ## _context {						\
+	_raw_context raw_ctx;						\
+	uint8_t cbc_ctx[_blocksize];					\
+};									\
+static int _cbc_name ## _setkey ( void *ctx, const void *key,		\
+				  size_t keylen ) {			\
+	struct _cbc_name ## _context * _cbc_name ## _ctx = ctx;		\
+	return cbc_setkey ( &_cbc_name ## _ctx->raw_ctx, key, keylen,	\
+			    &_raw_cipher, &_cbc_name ## _ctx->cbc_ctx );\
+}									\
+static void _cbc_name ## _setiv ( void *ctx, const void *iv ) {		\
+	struct _cbc_name ## _context * _cbc_name ## _ctx = ctx;		\
+	cbc_setiv ( &_cbc_name ## _ctx->raw_ctx, iv,			\
+		    &_raw_cipher, &aes_cbc_ctx->cbc_ctx );		\
+}									\
+static void _cbc_name ## _encrypt ( void *ctx, const void *src,		\
+				    void *dst, size_t len ) {		\
+	struct _cbc_name ## _context * _cbc_name ## _ctx = ctx;		\
+	cbc_encrypt ( &_cbc_name ## _ctx->raw_ctx, src, dst, len,	\
+		      &_raw_cipher, &aes_cbc_ctx->cbc_ctx );		\
+}									\
+static void _cbc_name ## _decrypt ( void *ctx, const void *src,		\
+				    void *dst, size_t len ) {		\
+	struct _cbc_name ## _context * _cbc_name ## _ctx = ctx;		\
+	cbc_decrypt ( &_cbc_name ## _ctx->raw_ctx, src, dst, len,	\
+		      &_raw_cipher, &aes_cbc_ctx->cbc_ctx );		\
+}									\
+struct cipher_algorithm _cbc_cipher = {					\
+	.name		= #_cbc_name,					\
+	.ctxsize	= sizeof ( struct _cbc_name ## _context ),	\
+	.blocksize	= _blocksize,					\
+	.setkey		= _cbc_name ## _setkey,				\
+	.setiv		= _cbc_name ## _setiv,				\
+	.encrypt	= _cbc_name ## _encrypt,			\
+	.decrypt	= _cbc_name ## _decrypt,			\
+};
+
 #endif /* _GPXE_CBC_H */