[PATCH] cryptoloop

util-linux is waiting for this: it needs to update "struct loop_info64"
to add the encryption policy name.

drivers/block/Kconfig

@@ -237,29 +237,20 @@ config BLK_DEV_LOOP
 	  root file system inside a DOS FAT file using this loop device
 	  driver.
 
-	  The loop device driver can also be used to "hide" a file system in a
-	  disk partition, floppy, or regular file, either using encryption
+	  To use the loop device, you need the losetup utility, found in the
+	  util-linux package, see
+	  <ftp://ftp.kernel.org/pub/linux/utils/util-linux/>.
+
+	  The loop device driver can also be used to "hide" a file system in
+	  a disk partition, floppy, or regular file, either using encryption
 	  (scrambling the data) or steganography (hiding the data in the low
 	  bits of, say, a sound file). This is also safe if the file resides
-	  on a remote file server. If you want to do this, you will first have
-	  to acquire and install a kernel patch from
-	  <ftp://ftp.kerneli.org/pub/kerneli/>, and then you need to
-	  say Y to this option.
-
-	  Note that alternative ways to use encrypted file systems are
-	  provided by the cfs package, which can be gotten from
-	  <ftp://ftp.kerneli.org/pub/kerneli/net-source/>, and the newer tcfs
-	  package, available at <http://tcfs.dia.unisa.it/>. You do not need
-	  to say Y here if you want to use one of these. However, using cfs
-	  requires saying Y to "NFS file system support" below while using
-	  tcfs requires applying a kernel patch. An alternative steganography
-	  solution is provided by StegFS, also available from
-	  <ftp://ftp.kerneli.org/pub/kerneli/net-source/>.
-
-	  To use the loop device, you need the losetup utility and a recent
-	  version of the mount program, both contained in the util-linux
-	  package. The location and current version number of util-linux is
-	  contained in the file <file:Documentation/Changes>.
+	  on a remote file server.
+
+	  There are several ways of doing this. Some of these require kernel
+	  patches. The vanilla kernel offers the cryptoloop option. If you
+	  want to use that, say Y to both LOOP and CRYPTOLOOP, and make sure
+	  you have a recent (version 2.12 or later) version of util-linux.
 
 	  Note that this loop device has nothing to do with the loopback
 	  device used for network connections from the machine to itself.
@@ -271,6 +262,14 @@ config BLK_DEV_LOOP
 
 	  Most users will answer N here.
 
+config BLK_DEV_CRYPTOLOOP
+	tristate "Cryptoloop Support"
+	depends on BLK_DEV_LOOP
+	---help---
+	  Say Y here if you want to be able to use the ciphers that are 
+	  provided by the CryptoAPI as loop transformation. This might be
+	  used as hard disk encryption.
+
 config BLK_DEV_NBD
 	tristate "Network block device support"
 	depends on NET

drivers/block/Makefile

@@ -36,3 +36,4 @@ obj-$(CONFIG_BLK_DEV_DAC960)	+= DAC960.o
 
 obj-$(CONFIG_BLK_DEV_UMEM)	+= umem.o
 obj-$(CONFIG_BLK_DEV_NBD)	+= nbd.o
+obj-$(CONFIG_BLK_DEV_CRYPTOLOOP) += cryptoloop.o

drivers/block/cryptoloop.c

+/*
+   Linux loop encryption enabling module
+
+   Copyright (C)  2002 Herbert Valerio Riedel <hvr@gnu.org>
+   Copyright (C)  2003 Fruhwirth Clemens <clemens@endorphin.org>
+
+   This module 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
+   (at your option) any later version.
+
+   This module 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 module; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/module.h>
+
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/crypto.h>
+#include <linux/blkdev.h>
+#include <linux/loop.h>
+#include <linux/blk.h>
+#include <asm/semaphore.h>
+#include <asm/uaccess.h>
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("loop blockdevice transferfunction adaptor / CryptoAPI");
+MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
+
+#define LOOP_IV_SECTOR_BITS 9
+#define LOOP_IV_SECTOR_SIZE (1 << LOOP_IV_SECTOR_BITS)
+
+static int
+cryptoloop_init(struct loop_device *lo, const struct loop_info64 *info)
+{
+	int err = -EINVAL;
+	char cms[LO_NAME_SIZE];			/* cipher-mode string */
+	char *cipher;
+	char *mode;
+	char *cmsp = cms;			/* c-m string pointer */
+	struct crypto_tfm *tfm = NULL;
+
+	/* encryption breaks for non sector aligned offsets */
+
+	if (info->lo_offset % LOOP_IV_SECTOR_SIZE)
+		goto out;
+
+	strncpy(cms, info->lo_crypt_name, LO_NAME_SIZE);
+	cms[LO_NAME_SIZE - 1] = 0;
+	cipher = strsep(&cmsp, "-");
+	mode = strsep(&cmsp, "-");
+
+	if (mode == NULL || strcmp(mode, "cbc") == 0)
+		tfm = crypto_alloc_tfm(cipher, CRYPTO_TFM_MODE_CBC);
+	else if (strcmp(mode, "ecb") == 0)
+		tfm = crypto_alloc_tfm(cipher, CRYPTO_TFM_MODE_ECB);
+	if (tfm == NULL)
+		return -EINVAL;
+
+	err = tfm->crt_u.cipher.cit_setkey(tfm, info->lo_encrypt_key,
+					   info->lo_encrypt_key_size);
+	
+	if (err != 0)
+		goto out_free_tfm;
+
+	lo->key_data = tfm;
+	return 0;
+
+ out_free_tfm:
+	crypto_free_tfm(tfm);
+
+ out:
+	return err;
+}
+
+typedef int (*encdec_t)(struct crypto_tfm *tfm,
+			struct scatterlist *sg_out,
+			struct scatterlist *sg_in,
+			unsigned int nsg, u8 *iv);
+
+static int
+cryptoloop_transfer(struct loop_device *lo, int cmd, char *raw_buf,
+		     char *loop_buf, int size, sector_t IV)
+{
+	struct crypto_tfm *tfm = (struct crypto_tfm *) lo->key_data;
+	struct scatterlist sg_out = { 0, };
+	struct scatterlist sg_in = { 0, };
+
+	encdec_t encdecfunc;
+	char const *in;
+	char *out;
+
+	if (cmd == READ) {
+		in = raw_buf;
+		out = loop_buf;
+		encdecfunc = tfm->crt_u.cipher.cit_decrypt_iv;
+	} else {
+		in = loop_buf;
+		out = raw_buf;
+		encdecfunc = tfm->crt_u.cipher.cit_encrypt_iv;
+	}
+
+	while (size > 0) {
+		const int sz = min(size, LOOP_IV_SECTOR_SIZE);
+		u32 iv[4] = { 0, };
+		iv[0] = cpu_to_le32(IV & 0xffffffff);
+
+		sg_in.page = virt_to_page(in);
+		sg_in.offset = (unsigned long)in & ~PAGE_MASK;
+		sg_in.length = sz;
+
+		sg_out.page = virt_to_page(out);
+		sg_out.offset = (unsigned long)out & ~PAGE_MASK;
+		sg_out.length = sz;
+
+		encdecfunc(tfm, &sg_out, &sg_in, sz, (u8 *)iv);
+
+		IV++;
+		size -= sz;
+		in += sz;
+		out += sz;
+	}
+
+	return 0;
+}
+
+
+static int
+cryptoloop_ioctl(struct loop_device *lo, int cmd, unsigned long arg)
+{
+	return -EINVAL;
+}
+
+static int
+cryptoloop_release(struct loop_device *lo)
+{
+	struct crypto_tfm *tfm = (struct crypto_tfm *) lo->key_data;
+	if (tfm != NULL) {
+		crypto_free_tfm(tfm);
+		lo->key_data = NULL;
+		return 0;
+	}
+	printk(KERN_ERR "cryptoloop_release(): tfm == NULL?\n");
+	return -EINVAL;
+}
+
+static struct loop_func_table cryptoloop_funcs = {
+	.number = LO_CRYPT_CRYPTOAPI,
+	.init = cryptoloop_init,
+	.ioctl = cryptoloop_ioctl,
+	.transfer = cryptoloop_transfer,
+	.release = cryptoloop_release,
+	.owner = THIS_MODULE
+};
+
+static int __init
+init_cryptoloop(void)
+{
+	int rc = loop_register_transfer(&cryptoloop_funcs);
+
+	if (rc)
+		printk(KERN_ERR "cryptoloop: loop_register_transfer failed\n");
+	return rc;
+}
+
+static void __exit
+cleanup_cryptoloop(void)
+{
+	if (loop_unregister_transfer(LO_CRYPT_CRYPTOAPI))
+		printk(KERN_ERR
+			"cryptoloop: loop_unregister_transfer failed\n");
+}
+
+module_init(init_cryptoloop);
+module_exit(cleanup_cryptoloop);

drivers/block/loop.c

@@ -840,7 +840,8 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
 	lo->lo_flags = 0;
 	lo->lo_queue.queuedata = NULL;
 	memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
-	memset(lo->lo_name, 0, LO_NAME_SIZE);
+	memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
+	memset(lo->lo_file_name, 0, LO_NAME_SIZE);
 	invalidate_bdev(bdev, 0);
 	set_capacity(disks[lo->lo_number], 0);
 	filp->f_dentry->d_inode->i_mapping->gfp_mask = gfp;
@@ -892,7 +893,10 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 			return -EFBIG;
 	}
 
-	strlcpy(lo->lo_name, info->lo_name, LO_NAME_SIZE);
+	memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
+	memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE);
+	lo->lo_file_name[LO_NAME_SIZE-1] = 0;
+	lo->lo_crypt_name[LO_NAME_SIZE-1] = 0;
 
 	if (!xfer)
 		xfer = &none_funcs;
@@ -931,7 +935,8 @@ loop_get_status(struct loop_device *lo, struct loop_info64 *info)
 	info->lo_offset = lo->lo_offset;
 	info->lo_sizelimit = lo->lo_sizelimit;
 	info->lo_flags = lo->lo_flags;
-	strlcpy(info->lo_name, lo->lo_name, LO_NAME_SIZE);
+	memcpy(info->lo_file_name, lo->lo_file_name, LO_NAME_SIZE);
+	memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE);
 	info->lo_encrypt_type =
 		lo->lo_encryption ? lo->lo_encryption->number : 0;
 	if (lo->lo_encrypt_key_size && capable(CAP_SYS_ADMIN)) {
@@ -957,7 +962,10 @@ loop_info64_from_old(const struct loop_info *info, struct loop_info64 *info64)
 	info64->lo_flags = info->lo_flags;
 	info64->lo_init[0] = info->lo_init[0];
 	info64->lo_init[1] = info->lo_init[1];
-	memcpy(info64->lo_name, info->lo_name, LO_NAME_SIZE);
+	if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
+		memcpy(info64->lo_crypt_name, info->lo_name, LO_NAME_SIZE);
+	else
+		memcpy(info64->lo_file_name, info->lo_name, LO_NAME_SIZE);
 	memcpy(info64->lo_encrypt_key, info->lo_encrypt_key, LO_KEY_SIZE);
 }
 
@@ -975,8 +983,11 @@ loop_info64_to_old(const struct loop_info64 *info64, struct loop_info *info)
 	info->lo_flags = info64->lo_flags;
 	info->lo_init[0] = info64->lo_init[0];
 	info->lo_init[1] = info64->lo_init[1];
-	memcpy(info->lo_name, info64->lo_name, LO_NAME_SIZE);
-	memcpy(info->lo_encrypt_key,info64->lo_encrypt_key,LO_KEY_SIZE);
+	if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
+		memcpy(info->lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
+	else
+		memcpy(info->lo_name, info64->lo_file_name, LO_NAME_SIZE);
+	memcpy(info->lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);
 
 	/* error in case values were truncated */
 	if (info->lo_device != info64->lo_device ||

include/linux/loop.h

@@ -36,7 +36,8 @@ struct loop_device {
 	int		(*transfer)(struct loop_device *, int cmd,
 				    char *raw_buf, char *loop_buf, int size,
 				    sector_t real_block);
-	char		lo_name[LO_NAME_SIZE];
+	char		lo_file_name[LO_NAME_SIZE];
+	char		lo_crypt_name[LO_NAME_SIZE];
 	char		lo_encrypt_key[LO_KEY_SIZE];
 	int		lo_encrypt_key_size;
 	struct loop_func_table *lo_encryption;
@@ -49,7 +50,6 @@ struct loop_device {
 	struct block_device *lo_device;
 	unsigned	lo_blocksize;
 	void		*key_data; 
-	char		key_reserved[48]; /* for use by the filter modules */
 
 	int		old_gfp_mask;
 
@@ -102,7 +102,8 @@ struct loop_info64 {
 	__u32		   lo_encrypt_type;
 	__u32		   lo_encrypt_key_size;		/* ioctl w/o */
 	__u32		   lo_flags;			/* ioctl r/o */
-	__u8		   lo_name[LO_NAME_SIZE];
+	__u8		   lo_file_name[LO_NAME_SIZE];
+	__u8		   lo_crypt_name[LO_NAME_SIZE];
 	__u8		   lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
 	__u64		   lo_init[2];
 };