[crypto] Add AES key-wrap mode (RFC 3394)

The unwrapping half is used by WPA2 code; the wrapping half is currently
unused.

Signed-off-by: Marty Connor <mdc@etherboot.org>

src/crypto/aes_wrap.c

@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
+ *
+ * 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.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdlib.h>
+#include <string.h>
+#include <gpxe/crypto.h>
+#include <gpxe/aes.h>
+
+/**
+ * Wrap a key or other data using AES Key Wrap (RFC 3394)
+ *
+ * @v kek	Key Encryption Key, 16 bytes
+ * @v src	Data to encrypt
+ * @v nblk	Number of 8-byte blocks in @a data
+ * @ret dest	Encrypted data (8 bytes longer than input)
+ *
+ * The algorithm is implemented such that @a src and @a dest may point
+ * to the same buffer.
+ */
+int aes_wrap ( const void *kek, const void *src, void *dest, int nblk )
+{
+	u8 *A = dest;
+	u8 B[16];
+	u8 *R;
+	int i, j;
+	void *aes_ctx = malloc ( AES_CTX_SIZE );
+
+	if ( ! aes_ctx )
+		return -1;
+
+	cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 );
+
+	/* Set up */
+	memset ( A, 0xA6, sizeof ( A ) );
+	memmove ( dest + 8, src, nblk * 8 );
+
+	/* Wrap */
+	for ( j = 0; j < 6; j++ ) {
+		R = dest + 8;
+		for ( i = 1; i <= nblk; i++ ) {
+			memcpy ( B, A, 8 );
+			memcpy ( B + 8, R, 8 );
+			cipher_encrypt ( &aes_algorithm, aes_ctx, B, B, 16 );
+			memcpy ( A, B, 8 );
+			A[7] ^= ( nblk * j ) + i;
+			memcpy ( R, B + 8, 8 );
+			R += 8;
+		}
+	}
+
+	free ( aes_ctx );
+	return 0;
+}
+
+/**
+ * Unwrap a key or other data using AES Key Wrap (RFC 3394)
+ *
+ * @v kek	Key Encryption Key, 16 bytes
+ * @v src	Data to decrypt
+ * @v nblk	Number of 8-byte blocks in @e plaintext key
+ * @ret dest	Decrypted data (8 bytes shorter than input)
+ * @ret rc	Zero on success, nonzero on IV mismatch
+ *
+ * The algorithm is implemented such that @a src and @a dest may point
+ * to the same buffer.
+ */
+int aes_unwrap ( const void *kek, const void *src, void *dest, int nblk )
+{
+	u8 A[8], B[16];
+	u8 *R;
+	int i, j;
+	void *aes_ctx = malloc ( AES_CTX_SIZE );
+
+	if ( ! aes_ctx )
+		return -1;
+
+	cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 );
+
+	/* Set up */
+	memcpy ( A, src, 8 );
+	memmove ( dest, src + 8, nblk * 8 );
+
+	/* Unwrap */
+	for ( j = 5; j >= 0; j-- ) {
+		R = dest + ( nblk - 1 ) * 8;
+		for ( i = nblk; i >= 1; i-- ) {
+			memcpy ( B, A, 8 );
+			memcpy ( B + 8, R, 8 );
+			B[7] ^= ( nblk * j ) + i;
+			cipher_decrypt ( &aes_algorithm, aes_ctx, B, B, 16 );
+			memcpy ( A, B, 8 );
+			memcpy ( R, B + 8, 8 );
+			R -= 8;
+		}
+	}
+
+	free ( aes_ctx );
+
+	/* Check IV */
+	for ( i = 0; i < 8; i++ ) {
+		if ( A[i] != 0xA6 )
+			return -1;
+	}
+
+	return 0;
+}

src/include/gpxe/aes.h

@@ -24,4 +24,7 @@ struct aes_context {
 extern struct cipher_algorithm aes_algorithm;
 extern struct cipher_algorithm aes_cbc_algorithm;
 
+int aes_wrap ( const void *kek, const void *src, void *dest, int nblk );
+int aes_unwrap ( const void *kek, const void *src, void *dest, int nblk );
+
 #endif /* _GPXE_AES_H */