// SPDX-License-Identifier: GPL-2.0-or-later

  /*
     Linux loop encryption enabling module
  
     Copyright (C)  2002 Herbert Valerio Riedel <hvr@gnu.org>
     Copyright (C)  2003 Fruhwirth Clemens <clemens@endorphin.org>

   */
  
  #include <linux/module.h>

  #include <crypto/skcipher.h>

  #include <linux/init.h>
  #include <linux/string.h>

  #include <linux/blkdev.h>

  #include <linux/scatterlist.h>

  #include <linux/uaccess.h>

  #include "loop.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;

  	int cipher_len;
  	int mode_len;

  	char cms[LO_NAME_SIZE];			/* cipher-mode string */

  	char *mode;
  	char *cmsp = cms;			/* c-m string pointer */

  	struct crypto_sync_skcipher *tfm;

  
  	/* 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_len = strcspn(cmsp, "-");
  
  	mode = cmsp + cipher_len;
  	mode_len = 0;
  	if (*mode) {
  		mode++;
  		mode_len = strcspn(mode, "-");
  	}
  
  	if (!mode_len) {
  		mode = "cbc";
  		mode_len = 3;
  	}
  
  	if (cipher_len + mode_len + 3 > LO_NAME_SIZE)

  		return -EINVAL;

  	memmove(cms, mode, mode_len);
  	cmsp = cms + mode_len;
  	*cmsp++ = '(';
  	memcpy(cmsp, info->lo_crypt_name, cipher_len);
  	cmsp += cipher_len;
  	*cmsp++ = ')';
  	*cmsp = 0;

  	tfm = crypto_alloc_sync_skcipher(cms, 0, 0);

  	if (IS_ERR(tfm))
  		return PTR_ERR(tfm);

  	err = crypto_sync_skcipher_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_sync_skcipher(tfm);

  
   out:
  	return err;
  }

  typedef int (*encdec_cbc_t)(struct skcipher_request *req);

  static int

  cryptoloop_transfer(struct loop_device *lo, int cmd,
  		    struct page *raw_page, unsigned raw_off,
  		    struct page *loop_page, unsigned loop_off,
  		    int size, sector_t IV)

  {

  	struct crypto_sync_skcipher *tfm = lo->key_data;
  	SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm);

  	struct scatterlist sg_out;
  	struct scatterlist sg_in;

  
  	encdec_cbc_t encdecfunc;
  	struct page *in_page, *out_page;
  	unsigned in_offs, out_offs;

  	int err;

  	skcipher_request_set_sync_tfm(req, tfm);

  	skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,
  				      NULL, NULL);

  	sg_init_table(&sg_out, 1);
  	sg_init_table(&sg_in, 1);

  	if (cmd == READ) {
  		in_page = raw_page;
  		in_offs = raw_off;
  		out_page = loop_page;
  		out_offs = loop_off;

  		encdecfunc = crypto_skcipher_decrypt;

  	} else {
  		in_page = loop_page;
  		in_offs = loop_off;
  		out_page = raw_page;
  		out_offs = raw_off;

  		encdecfunc = crypto_skcipher_encrypt;

  	}
  
  	while (size > 0) {
  		const int sz = min(size, LOOP_IV_SECTOR_SIZE);
  		u32 iv[4] = { 0, };
  		iv[0] = cpu_to_le32(IV & 0xffffffff);

  		sg_set_page(&sg_in, in_page, sz, in_offs);
  		sg_set_page(&sg_out, out_page, sz, out_offs);

  		skcipher_request_set_crypt(req, &sg_in, &sg_out, sz, iv);
  		err = encdecfunc(req);

  		if (err)

  			goto out;

  
  		IV++;
  		size -= sz;
  		in_offs += sz;
  		out_offs += sz;
  	}

  	err = 0;
  
  out:
  	skcipher_request_zero(req);
  	return err;

  }
  
  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_sync_skcipher *tfm = lo->key_data;

  	if (tfm != NULL) {

  		crypto_free_sync_skcipher(tfm);

  		lo->key_data = NULL;
  		return 0;
  	}
  	printk(KERN_ERR "cryptoloop_release(): tfm == NULL?
  ");
  	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
  ");
  	return rc;
  }
  
  static void __exit
  cleanup_cryptoloop(void)
  {
  	if (loop_unregister_transfer(LO_CRYPT_CRYPTOAPI))
  		printk(KERN_ERR
  			"cryptoloop: loop_unregister_transfer failed
  ");
  }
  
  module_init(init_cryptoloop);
  module_exit(cleanup_cryptoloop);