[crypto] Add our own general-purpose cipher-block chaining routines

src/crypto/cbc.c

@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2009 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <string.h>
+#include <assert.h>
+#include <gpxe/crypto.h>
+#include <gpxe/cbc.h>
+
+/** @file
+ *
+ * Cipher-block chaining
+ *
+ */
+
+/**
+ * XOR data blocks
+ *
+ * @v src		Input data
+ * @v dst		Second input data and output data buffer
+ * @v len		Length of data
+ */
+static void cbc_xor ( const void *src, void *dst, size_t len ) {
+	const uint32_t *srcl = src;
+	uint32_t *dstl = dst;
+	unsigned int i;
+
+	/* Assume that block sizes will always be dword-aligned, for speed */
+	assert ( ( len % sizeof ( *srcl ) ) == 0 );
+
+	for ( i = 0 ; i < ( len / sizeof ( *srcl ) ) ; i++ )
+		dstl[i] ^= srcl[i];
+}
+
+/**
+ * Encrypt data
+ *
+ * @v ctx		Context
+ * @v src		Data to encrypt
+ * @v dst		Buffer for encrypted data
+ * @v len		Length of data
+ * @v cipher		Underlying cipher algorithm
+ * @v cbc_ctx		CBC context
+ */
+void cbc_encrypt ( void *ctx, const void *src, void *dst, size_t len,
+		   struct cipher_algorithm *cipher, void *cbc_ctx ) {
+	size_t blocksize = cipher->blocksize;
+
+	assert ( ( len % blocksize ) == 0 );
+
+	while ( len ) {
+		cbc_xor ( src, cbc_ctx, blocksize );
+		cipher_encrypt ( cipher, ctx, cbc_ctx, dst, blocksize );
+		memcpy ( cbc_ctx, dst, blocksize );
+		dst += blocksize;
+		src += blocksize;
+		len -= blocksize;
+	}
+}
+
+/**
+ * Decrypt data
+ *
+ * @v ctx		Context
+ * @v src		Data to decrypt
+ * @v dst		Buffer for decrypted data
+ * @v len		Length of data
+ * @v cipher		Underlying cipher algorithm
+ * @v cbc_ctx		CBC context
+ */
+void cbc_decrypt ( void *ctx, const void *src, void *dst, size_t len,
+		   struct cipher_algorithm *cipher, void *cbc_ctx ) {
+	size_t blocksize = cipher->blocksize;
+
+	assert ( ( len % blocksize ) == 0 );
+
+	while ( len ) {
+		cipher_decrypt ( cipher, ctx, src, dst, blocksize );
+		cbc_xor ( cbc_ctx, dst, blocksize );
+		memcpy ( cbc_ctx, src, blocksize );
+		dst += blocksize;
+		src += blocksize;
+		len -= blocksize;
+	}
+}