/*
   * Copyright (C) 2010 IBM Corporation
   * Copyright (C) 2010 Politecnico di Torino, Italy
   *                    TORSEC group -- http://security.polito.it
   *
   * Authors:
   * Mimi Zohar <zohar@us.ibm.com>
   * Roberto Sassu <roberto.sassu@polito.it>
   *
   * 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, version 2 of the License.
   *
   * See Documentation/security/keys-trusted-encrypted.txt
   */
  
  #include <linux/uaccess.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/parser.h>
  #include <linux/string.h>
  #include <linux/err.h>
  #include <keys/user-type.h>
  #include <keys/trusted-type.h>
  #include <keys/encrypted-type.h>
  #include <linux/key-type.h>
  #include <linux/random.h>
  #include <linux/rcupdate.h>
  #include <linux/scatterlist.h>
  #include <linux/crypto.h>
  #include <linux/ctype.h>
  #include <crypto/hash.h>
  #include <crypto/sha.h>
  #include <crypto/aes.h>
  
  #include "encrypted.h"
  #include "ecryptfs_format.h"
  
  static const char KEY_TRUSTED_PREFIX[] = "trusted:";
  static const char KEY_USER_PREFIX[] = "user:";
  static const char hash_alg[] = "sha256";
  static const char hmac_alg[] = "hmac(sha256)";
  static const char blkcipher_alg[] = "cbc(aes)";
  static const char key_format_default[] = "default";
  static const char key_format_ecryptfs[] = "ecryptfs";
  static unsigned int ivsize;
  static int blksize;
  
  #define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
  #define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
  #define KEY_ECRYPTFS_DESC_LEN 16
  #define HASH_SIZE SHA256_DIGEST_SIZE
  #define MAX_DATA_SIZE 4096
  #define MIN_DATA_SIZE  20
  
  struct sdesc {
  	struct shash_desc shash;
  	char ctx[];
  };
  
  static struct crypto_shash *hashalg;
  static struct crypto_shash *hmacalg;
  
  enum {
  	Opt_err = -1, Opt_new, Opt_load, Opt_update
  };
  
  enum {
  	Opt_error = -1, Opt_default, Opt_ecryptfs
  };
  
  static const match_table_t key_format_tokens = {
  	{Opt_default, "default"},
  	{Opt_ecryptfs, "ecryptfs"},
  	{Opt_error, NULL}
  };
  
  static const match_table_t key_tokens = {
  	{Opt_new, "new"},
  	{Opt_load, "load"},
  	{Opt_update, "update"},
  	{Opt_err, NULL}
  };
  
  static int aes_get_sizes(void)
  {
  	struct crypto_blkcipher *tfm;
  
  	tfm = crypto_alloc_blkcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
  	if (IS_ERR(tfm)) {
  		pr_err("encrypted_key: failed to alloc_cipher (%ld)
  ",
  		       PTR_ERR(tfm));
  		return PTR_ERR(tfm);
  	}
  	ivsize = crypto_blkcipher_ivsize(tfm);
  	blksize = crypto_blkcipher_blocksize(tfm);
  	crypto_free_blkcipher(tfm);
  	return 0;
  }
  
  /*
   * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key
   *
   * The description of a encrypted key with format 'ecryptfs' must contain
   * exactly 16 hexadecimal characters.
   *
   */
  static int valid_ecryptfs_desc(const char *ecryptfs_desc)
  {
  	int i;
  
  	if (strlen(ecryptfs_desc) != KEY_ECRYPTFS_DESC_LEN) {
  		pr_err("encrypted_key: key description must be %d hexadecimal "
  		       "characters long
  ", KEY_ECRYPTFS_DESC_LEN);
  		return -EINVAL;
  	}
  
  	for (i = 0; i < KEY_ECRYPTFS_DESC_LEN; i++) {
  		if (!isxdigit(ecryptfs_desc[i])) {
  			pr_err("encrypted_key: key description must contain "
  			       "only hexadecimal characters
  ");
  			return -EINVAL;
  		}
  	}
  
  	return 0;
  }
  
  /*
   * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
   *
   * key-type:= "trusted:" | "user:"
   * desc:= master-key description
   *
   * Verify that 'key-type' is valid and that 'desc' exists. On key update,
   * only the master key description is permitted to change, not the key-type.
   * The key-type remains constant.
   *
   * On success returns 0, otherwise -EINVAL.
   */
  static int valid_master_desc(const char *new_desc, const char *orig_desc)
  {
  	if (!memcmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) {
  		if (strlen(new_desc) == KEY_TRUSTED_PREFIX_LEN)
  			goto out;
  		if (orig_desc)
  			if (memcmp(new_desc, orig_desc, KEY_TRUSTED_PREFIX_LEN))
  				goto out;
  	} else if (!memcmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) {
  		if (strlen(new_desc) == KEY_USER_PREFIX_LEN)
  			goto out;
  		if (orig_desc)
  			if (memcmp(new_desc, orig_desc, KEY_USER_PREFIX_LEN))
  				goto out;
  	} else
  		goto out;
  	return 0;
  out:
  	return -EINVAL;
  }
  
  /*
   * datablob_parse - parse the keyctl data
   *
   * datablob format:
   * new [<format>] <master-key name> <decrypted data length>
   * load [<format>] <master-key name> <decrypted data length>
   *     <encrypted iv + data>
   * update <new-master-key name>
   *
   * Tokenizes a copy of the keyctl data, returning a pointer to each token,
   * which is null terminated.
   *
   * On success returns 0, otherwise -EINVAL.
   */
  static int datablob_parse(char *datablob, const char **format,
  			  char **master_desc, char **decrypted_datalen,
  			  char **hex_encoded_iv)
  {
  	substring_t args[MAX_OPT_ARGS];
  	int ret = -EINVAL;
  	int key_cmd;
  	int key_format;
  	char *p, *keyword;
  
  	keyword = strsep(&datablob, " \t");
  	if (!keyword) {
  		pr_info("encrypted_key: insufficient parameters specified
  ");
  		return ret;
  	}
  	key_cmd = match_token(keyword, key_tokens, args);
  
  	/* Get optional format: default | ecryptfs */
  	p = strsep(&datablob, " \t");
  	if (!p) {
  		pr_err("encrypted_key: insufficient parameters specified
  ");
  		return ret;
  	}
  
  	key_format = match_token(p, key_format_tokens, args);
  	switch (key_format) {
  	case Opt_ecryptfs:
  	case Opt_default:
  		*format = p;
  		*master_desc = strsep(&datablob, " \t");
  		break;
  	case Opt_error:
  		*master_desc = p;
  		break;
  	}
  
  	if (!*master_desc) {
  		pr_info("encrypted_key: master key parameter is missing
  ");
  		goto out;
  	}
  
  	if (valid_master_desc(*master_desc, NULL) < 0) {
  		pr_info("encrypted_key: master key parameter \'%s\' "
  			"is invalid
  ", *master_desc);
  		goto out;
  	}
  
  	if (decrypted_datalen) {
  		*decrypted_datalen = strsep(&datablob, " \t");
  		if (!*decrypted_datalen) {
  			pr_info("encrypted_key: keylen parameter is missing
  ");
  			goto out;
  		}
  	}
  
  	switch (key_cmd) {
  	case Opt_new:
  		if (!decrypted_datalen) {
  			pr_info("encrypted_key: keyword \'%s\' not allowed "
  				"when called from .update method
  ", keyword);
  			break;
  		}
  		ret = 0;
  		break;
  	case Opt_load:
  		if (!decrypted_datalen) {
  			pr_info("encrypted_key: keyword \'%s\' not allowed "
  				"when called from .update method
  ", keyword);
  			break;
  		}
  		*hex_encoded_iv = strsep(&datablob, " \t");
  		if (!*hex_encoded_iv) {
  			pr_info("encrypted_key: hex blob is missing
  ");
  			break;
  		}
  		ret = 0;
  		break;
  	case Opt_update:
  		if (decrypted_datalen) {
  			pr_info("encrypted_key: keyword \'%s\' not allowed "
  				"when called from .instantiate method
  ",
  				keyword);
  			break;
  		}
  		ret = 0;
  		break;
  	case Opt_err:
  		pr_info("encrypted_key: keyword \'%s\' not recognized
  ",
  			keyword);
  		break;
  	}
  out:
  	return ret;
  }
  
  /*
   * datablob_format - format as an ascii string, before copying to userspace
   */
  static char *datablob_format(struct encrypted_key_payload *epayload,
  			     size_t asciiblob_len)
  {
  	char *ascii_buf, *bufp;
  	u8 *iv = epayload->iv;
  	int len;
  	int i;
  
  	ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
  	if (!ascii_buf)
  		goto out;
  
  	ascii_buf[asciiblob_len] = '\0';
  
  	/* copy datablob master_desc and datalen strings */
  	len = sprintf(ascii_buf, "%s %s %s ", epayload->format,
  		      epayload->master_desc, epayload->datalen);
  
  	/* convert the hex encoded iv, encrypted-data and HMAC to ascii */
  	bufp = &ascii_buf[len];
  	for (i = 0; i < (asciiblob_len - len) / 2; i++)
  		bufp = hex_byte_pack(bufp, iv[i]);
  out:
  	return ascii_buf;
  }
  
  /*
   * request_user_key - request the user key
   *
   * Use a user provided key to encrypt/decrypt an encrypted-key.
   */
  static struct key *request_user_key(const char *master_desc, u8 **master_key,
  				    size_t *master_keylen)
  {
  	struct user_key_payload *upayload;
  	struct key *ukey;
  
  	ukey = request_key(&key_type_user, master_desc, NULL);
  	if (IS_ERR(ukey))
  		goto error;
  
  	down_read(&ukey->sem);
  	upayload = ukey->payload.data;
  	*master_key = upayload->data;
  	*master_keylen = upayload->datalen;
  error:
  	return ukey;
  }
  
  static struct sdesc *alloc_sdesc(struct crypto_shash *alg)
  {
  	struct sdesc *sdesc;
  	int size;
  
  	size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);
  	sdesc = kmalloc(size, GFP_KERNEL);
  	if (!sdesc)
  		return ERR_PTR(-ENOMEM);
  	sdesc->shash.tfm = alg;
  	sdesc->shash.flags = 0x0;
  	return sdesc;
  }
  
  static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
  		     const u8 *buf, unsigned int buflen)
  {
  	struct sdesc *sdesc;
  	int ret;
  
  	sdesc = alloc_sdesc(hmacalg);
  	if (IS_ERR(sdesc)) {
  		pr_info("encrypted_key: can't alloc %s
  ", hmac_alg);
  		return PTR_ERR(sdesc);
  	}
  
  	ret = crypto_shash_setkey(hmacalg, key, keylen);
  	if (!ret)
  		ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
  	kfree(sdesc);
  	return ret;
  }
  
  static int calc_hash(u8 *digest, const u8 *buf, unsigned int buflen)
  {
  	struct sdesc *sdesc;
  	int ret;
  
  	sdesc = alloc_sdesc(hashalg);
  	if (IS_ERR(sdesc)) {
  		pr_info("encrypted_key: can't alloc %s
  ", hash_alg);
  		return PTR_ERR(sdesc);
  	}
  
  	ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
  	kfree(sdesc);
  	return ret;
  }
  
  enum derived_key_type { ENC_KEY, AUTH_KEY };
  
  /* Derive authentication/encryption key from trusted key */
  static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
  			   const u8 *master_key, size_t master_keylen)
  {
  	u8 *derived_buf;
  	unsigned int derived_buf_len;
  	int ret;
  
  	derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
  	if (derived_buf_len < HASH_SIZE)
  		derived_buf_len = HASH_SIZE;
  
  	derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
  	if (!derived_buf) {
  		pr_err("encrypted_key: out of memory
  ");
  		return -ENOMEM;
  	}
  	if (key_type)
  		strcpy(derived_buf, "AUTH_KEY");
  	else
  		strcpy(derived_buf, "ENC_KEY");
  
  	memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
  	       master_keylen);
  	ret = calc_hash(derived_key, derived_buf, derived_buf_len);
  	kfree(derived_buf);
  	return ret;
  }
  
  static int init_blkcipher_desc(struct blkcipher_desc *desc, const u8 *key,
  			       unsigned int key_len, const u8 *iv,
  			       unsigned int ivsize)
  {
  	int ret;
  
  	desc->tfm = crypto_alloc_blkcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
  	if (IS_ERR(desc->tfm)) {
  		pr_err("encrypted_key: failed to load %s transform (%ld)
  ",
  		       blkcipher_alg, PTR_ERR(desc->tfm));
  		return PTR_ERR(desc->tfm);
  	}
  	desc->flags = 0;
  
  	ret = crypto_blkcipher_setkey(desc->tfm, key, key_len);
  	if (ret < 0) {
  		pr_err("encrypted_key: failed to setkey (%d)
  ", ret);
  		crypto_free_blkcipher(desc->tfm);
  		return ret;
  	}
  	crypto_blkcipher_set_iv(desc->tfm, iv, ivsize);
  	return 0;
  }
  
  static struct key *request_master_key(struct encrypted_key_payload *epayload,
  				      u8 **master_key, size_t *master_keylen)
  {
  	struct key *mkey = NULL;
  
  	if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
  		     KEY_TRUSTED_PREFIX_LEN)) {
  		mkey = request_trusted_key(epayload->master_desc +
  					   KEY_TRUSTED_PREFIX_LEN,
  					   master_key, master_keylen);
  	} else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
  			    KEY_USER_PREFIX_LEN)) {
  		mkey = request_user_key(epayload->master_desc +
  					KEY_USER_PREFIX_LEN,
  					master_key, master_keylen);
  	} else
  		goto out;
  
  	if (IS_ERR(mkey)) {
  		int ret = PTR_ERR(mkey);
  
  		if (ret == -ENOTSUPP)
  			pr_info("encrypted_key: key %s not supported",
  				epayload->master_desc);
  		else
  			pr_info("encrypted_key: key %s not found",
  				epayload->master_desc);
  		goto out;
  	}
  
  	dump_master_key(*master_key, *master_keylen);
  out:
  	return mkey;
  }
  
  /* Before returning data to userspace, encrypt decrypted data. */
  static int derived_key_encrypt(struct encrypted_key_payload *epayload,
  			       const u8 *derived_key,
  			       unsigned int derived_keylen)
  {
  	struct scatterlist sg_in[2];
  	struct scatterlist sg_out[1];
  	struct blkcipher_desc desc;
  	unsigned int encrypted_datalen;
  	unsigned int padlen;
  	char pad[16];
  	int ret;
  
  	encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
  	padlen = encrypted_datalen - epayload->decrypted_datalen;
  
  	ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
  				  epayload->iv, ivsize);
  	if (ret < 0)
  		goto out;
  	dump_decrypted_data(epayload);
  
  	memset(pad, 0, sizeof pad);
  	sg_init_table(sg_in, 2);
  	sg_set_buf(&sg_in[0], epayload->decrypted_data,
  		   epayload->decrypted_datalen);
  	sg_set_buf(&sg_in[1], pad, padlen);
  
  	sg_init_table(sg_out, 1);
  	sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
  
  	ret = crypto_blkcipher_encrypt(&desc, sg_out, sg_in, encrypted_datalen);
  	crypto_free_blkcipher(desc.tfm);
  	if (ret < 0)
  		pr_err("encrypted_key: failed to encrypt (%d)
  ", ret);
  	else
  		dump_encrypted_data(epayload, encrypted_datalen);
  out:
  	return ret;
  }
  
  static int datablob_hmac_append(struct encrypted_key_payload *epayload,
  				const u8 *master_key, size_t master_keylen)
  {
  	u8 derived_key[HASH_SIZE];
  	u8 *digest;
  	int ret;
  
  	ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
  	if (ret < 0)
  		goto out;
  
  	digest = epayload->format + epayload->datablob_len;
  	ret = calc_hmac(digest, derived_key, sizeof derived_key,
  			epayload->format, epayload->datablob_len);
  	if (!ret)
  		dump_hmac(NULL, digest, HASH_SIZE);
  out:
  	return ret;
  }
  
  /* verify HMAC before decrypting encrypted key */
  static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
  				const u8 *format, const u8 *master_key,
  				size_t master_keylen)
  {
  	u8 derived_key[HASH_SIZE];
  	u8 digest[HASH_SIZE];
  	int ret;
  	char *p;
  	unsigned short len;
  
  	ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
  	if (ret < 0)
  		goto out;
  
  	len = epayload->datablob_len;
  	if (!format) {
  		p = epayload->master_desc;
  		len -= strlen(epayload->format) + 1;
  	} else
  		p = epayload->format;
  
  	ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
  	if (ret < 0)
  		goto out;
  	ret = memcmp(digest, epayload->format + epayload->datablob_len,
  		     sizeof digest);
  	if (ret) {
  		ret = -EINVAL;
  		dump_hmac("datablob",
  			  epayload->format + epayload->datablob_len,
  			  HASH_SIZE);
  		dump_hmac("calc", digest, HASH_SIZE);
  	}
  out:
  	return ret;
  }
  
  static int derived_key_decrypt(struct encrypted_key_payload *epayload,
  			       const u8 *derived_key,
  			       unsigned int derived_keylen)
  {
  	struct scatterlist sg_in[1];
  	struct scatterlist sg_out[2];
  	struct blkcipher_desc desc;
  	unsigned int encrypted_datalen;
  	char pad[16];
  	int ret;
  
  	encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
  	ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
  				  epayload->iv, ivsize);
  	if (ret < 0)
  		goto out;
  	dump_encrypted_data(epayload, encrypted_datalen);
  
  	memset(pad, 0, sizeof pad);
  	sg_init_table(sg_in, 1);
  	sg_init_table(sg_out, 2);
  	sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
  	sg_set_buf(&sg_out[0], epayload->decrypted_data,
  		   epayload->decrypted_datalen);
  	sg_set_buf(&sg_out[1], pad, sizeof pad);
  
  	ret = crypto_blkcipher_decrypt(&desc, sg_out, sg_in, encrypted_datalen);
  	crypto_free_blkcipher(desc.tfm);
  	if (ret < 0)
  		goto out;
  	dump_decrypted_data(epayload);
  out:
  	return ret;
  }
  
  /* Allocate memory for decrypted key and datablob. */
  static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
  							 const char *format,
  							 const char *master_desc,
  							 const char *datalen)
  {
  	struct encrypted_key_payload *epayload = NULL;
  	unsigned short datablob_len;
  	unsigned short decrypted_datalen;
  	unsigned short payload_datalen;
  	unsigned int encrypted_datalen;
  	unsigned int format_len;
  	long dlen;
  	int ret;
  
  	ret = strict_strtol(datalen, 10, &dlen);
  	if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
  		return ERR_PTR(-EINVAL);
  
  	format_len = (!format) ? strlen(key_format_default) : strlen(format);
  	decrypted_datalen = dlen;
  	payload_datalen = decrypted_datalen;
  	if (format && !strcmp(format, key_format_ecryptfs)) {
  		if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
  			pr_err("encrypted_key: keylen for the ecryptfs format "
  			       "must be equal to %d bytes
  ",
  			       ECRYPTFS_MAX_KEY_BYTES);
  			return ERR_PTR(-EINVAL);
  		}
  		decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
  		payload_datalen = sizeof(struct ecryptfs_auth_tok);
  	}
  
  	encrypted_datalen = roundup(decrypted_datalen, blksize);
  
  	datablob_len = format_len + 1 + strlen(master_desc) + 1
  	    + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
  
  	ret = key_payload_reserve(key, payload_datalen + datablob_len
  				  + HASH_SIZE + 1);
  	if (ret < 0)
  		return ERR_PTR(ret);
  
  	epayload = kzalloc(sizeof(*epayload) + payload_datalen +
  			   datablob_len + HASH_SIZE + 1, GFP_KERNEL);
  	if (!epayload)
  		return ERR_PTR(-ENOMEM);
  
  	epayload->payload_datalen = payload_datalen;
  	epayload->decrypted_datalen = decrypted_datalen;
  	epayload->datablob_len = datablob_len;
  	return epayload;
  }
  
  static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
  				 const char *format, const char *hex_encoded_iv)
  {
  	struct key *mkey;
  	u8 derived_key[HASH_SIZE];
  	u8 *master_key;
  	u8 *hmac;
  	const char *hex_encoded_data;
  	unsigned int encrypted_datalen;
  	size_t master_keylen;
  	size_t asciilen;
  	int ret;
  
  	encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
  	asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
  	if (strlen(hex_encoded_iv) != asciilen)
  		return -EINVAL;
  
  	hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
  	ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
  	if (ret < 0)
  		return -EINVAL;
  	ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
  		      encrypted_datalen);
  	if (ret < 0)
  		return -EINVAL;
  
  	hmac = epayload->format + epayload->datablob_len;
  	ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
  		      HASH_SIZE);
  	if (ret < 0)
  		return -EINVAL;
  
  	mkey = request_master_key(epayload, &master_key, &master_keylen);
  	if (IS_ERR(mkey))
  		return PTR_ERR(mkey);
  
  	ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
  	if (ret < 0) {
  		pr_err("encrypted_key: bad hmac (%d)
  ", ret);
  		goto out;
  	}
  
  	ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
  	if (ret < 0)
  		goto out;
  
  	ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
  	if (ret < 0)
  		pr_err("encrypted_key: failed to decrypt key (%d)
  ", ret);
  out:
  	up_read(&mkey->sem);
  	key_put(mkey);
  	return ret;
  }
  
  static void __ekey_init(struct encrypted_key_payload *epayload,
  			const char *format, const char *master_desc,
  			const char *datalen)
  {
  	unsigned int format_len;
  
  	format_len = (!format) ? strlen(key_format_default) : strlen(format);
  	epayload->format = epayload->payload_data + epayload->payload_datalen;
  	epayload->master_desc = epayload->format + format_len + 1;
  	epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
  	epayload->iv = epayload->datalen + strlen(datalen) + 1;
  	epayload->encrypted_data = epayload->iv + ivsize + 1;
  	epayload->decrypted_data = epayload->payload_data;
  
  	if (!format)
  		memcpy(epayload->format, key_format_default, format_len);
  	else {
  		if (!strcmp(format, key_format_ecryptfs))
  			epayload->decrypted_data =
  				ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
  
  		memcpy(epayload->format, format, format_len);
  	}
  
  	memcpy(epayload->master_desc, master_desc, strlen(master_desc));
  	memcpy(epayload->datalen, datalen, strlen(datalen));
  }
  
  /*
   * encrypted_init - initialize an encrypted key
   *
   * For a new key, use a random number for both the iv and data
   * itself.  For an old key, decrypt the hex encoded data.
   */
  static int encrypted_init(struct encrypted_key_payload *epayload,
  			  const char *key_desc, const char *format,
  			  const char *master_desc, const char *datalen,
  			  const char *hex_encoded_iv)
  {
  	int ret = 0;
  
  	if (format && !strcmp(format, key_format_ecryptfs)) {
  		ret = valid_ecryptfs_desc(key_desc);
  		if (ret < 0)
  			return ret;
  
  		ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
  				       key_desc);
  	}
  
  	__ekey_init(epayload, format, master_desc, datalen);
  	if (!hex_encoded_iv) {
  		get_random_bytes(epayload->iv, ivsize);
  
  		get_random_bytes(epayload->decrypted_data,
  				 epayload->decrypted_datalen);
  	} else
  		ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
  	return ret;
  }
  
  /*
   * encrypted_instantiate - instantiate an encrypted key
   *
   * Decrypt an existing encrypted datablob or create a new encrypted key
   * based on a kernel random number.
   *
   * On success, return 0. Otherwise return errno.
   */
  static int encrypted_instantiate(struct key *key,
  				 struct key_preparsed_payload *prep)
  {
  	struct encrypted_key_payload *epayload = NULL;
  	char *datablob = NULL;
  	const char *format = NULL;
  	char *master_desc = NULL;
  	char *decrypted_datalen = NULL;
  	char *hex_encoded_iv = NULL;
  	size_t datalen = prep->datalen;
  	int ret;
  
  	if (datalen <= 0 || datalen > 32767 || !prep->data)
  		return -EINVAL;
  
  	datablob = kmalloc(datalen + 1, GFP_KERNEL);
  	if (!datablob)
  		return -ENOMEM;
  	datablob[datalen] = 0;
  	memcpy(datablob, prep->data, datalen);
  	ret = datablob_parse(datablob, &format, &master_desc,
  			     &decrypted_datalen, &hex_encoded_iv);
  	if (ret < 0)
  		goto out;
  
  	epayload = encrypted_key_alloc(key, format, master_desc,
  				       decrypted_datalen);
  	if (IS_ERR(epayload)) {
  		ret = PTR_ERR(epayload);
  		goto out;
  	}
  	ret = encrypted_init(epayload, key->description, format, master_desc,
  			     decrypted_datalen, hex_encoded_iv);
  	if (ret < 0) {
  		kfree(epayload);
  		goto out;
  	}
  
  	rcu_assign_keypointer(key, epayload);
  out:
  	kfree(datablob);
  	return ret;
  }
  
  static void encrypted_rcu_free(struct rcu_head *rcu)
  {
  	struct encrypted_key_payload *epayload;
  
  	epayload = container_of(rcu, struct encrypted_key_payload, rcu);
  	memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
  	kfree(epayload);
  }
  
  /*
   * encrypted_update - update the master key description
   *
   * Change the master key description for an existing encrypted key.
   * The next read will return an encrypted datablob using the new
   * master key description.
   *
   * On success, return 0. Otherwise return errno.
   */
  static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
  {
  	struct encrypted_key_payload *epayload = key->payload.data;
  	struct encrypted_key_payload *new_epayload;
  	char *buf;
  	char *new_master_desc = NULL;
  	const char *format = NULL;
  	size_t datalen = prep->datalen;
  	int ret = 0;
  
  	if (datalen <= 0 || datalen > 32767 || !prep->data)
  		return -EINVAL;
  
  	buf = kmalloc(datalen + 1, GFP_KERNEL);
  	if (!buf)
  		return -ENOMEM;
  
  	buf[datalen] = 0;
  	memcpy(buf, prep->data, datalen);
  	ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
  	if (ret < 0)
  		goto out;
  
  	ret = valid_master_desc(new_master_desc, epayload->master_desc);
  	if (ret < 0)
  		goto out;
  
  	new_epayload = encrypted_key_alloc(key, epayload->format,
  					   new_master_desc, epayload->datalen);
  	if (IS_ERR(new_epayload)) {
  		ret = PTR_ERR(new_epayload);
  		goto out;
  	}
  
  	__ekey_init(new_epayload, epayload->format, new_master_desc,
  		    epayload->datalen);
  
  	memcpy(new_epayload->iv, epayload->iv, ivsize);
  	memcpy(new_epayload->payload_data, epayload->payload_data,
  	       epayload->payload_datalen);
  
  	rcu_assign_keypointer(key, new_epayload);
  	call_rcu(&epayload->rcu, encrypted_rcu_free);
  out:
  	kfree(buf);
  	return ret;
  }
  
  /*
   * encrypted_read - format and copy the encrypted data to userspace
   *
   * The resulting datablob format is:
   * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
   *
   * On success, return to userspace the encrypted key datablob size.
   */
  static long encrypted_read(const struct key *key, char __user *buffer,
  			   size_t buflen)
  {
  	struct encrypted_key_payload *epayload;
  	struct key *mkey;
  	u8 *master_key;
  	size_t master_keylen;
  	char derived_key[HASH_SIZE];
  	char *ascii_buf;
  	size_t asciiblob_len;
  	int ret;
  
  	epayload = rcu_dereference_key(key);
  
  	/* returns the hex encoded iv, encrypted-data, and hmac as ascii */
  	asciiblob_len = epayload->datablob_len + ivsize + 1
  	    + roundup(epayload->decrypted_datalen, blksize)
  	    + (HASH_SIZE * 2);
  
  	if (!buffer || buflen < asciiblob_len)
  		return asciiblob_len;
  
  	mkey = request_master_key(epayload, &master_key, &master_keylen);
  	if (IS_ERR(mkey))
  		return PTR_ERR(mkey);
  
  	ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
  	if (ret < 0)
  		goto out;
  
  	ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
  	if (ret < 0)
  		goto out;
  
  	ret = datablob_hmac_append(epayload, master_key, master_keylen);
  	if (ret < 0)
  		goto out;
  
  	ascii_buf = datablob_format(epayload, asciiblob_len);
  	if (!ascii_buf) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	up_read(&mkey->sem);
  	key_put(mkey);
  
  	if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0)
  		ret = -EFAULT;
  	kfree(ascii_buf);
  
  	return asciiblob_len;
  out:
  	up_read(&mkey->sem);
  	key_put(mkey);
  	return ret;
  }
  
  /*
   * encrypted_destroy - before freeing the key, clear the decrypted data
   *
   * Before freeing the key, clear the memory containing the decrypted
   * key data.
   */
  static void encrypted_destroy(struct key *key)
  {
  	struct encrypted_key_payload *epayload = key->payload.data;
  
  	if (!epayload)
  		return;
  
  	memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
  	kfree(key->payload.data);
  }
  
  struct key_type key_type_encrypted = {
  	.name = "encrypted",
  	.instantiate = encrypted_instantiate,
  	.update = encrypted_update,
  	.match = user_match,
  	.destroy = encrypted_destroy,
  	.describe = user_describe,
  	.read = encrypted_read,
  };
  EXPORT_SYMBOL_GPL(key_type_encrypted);
  
  static void encrypted_shash_release(void)
  {
  	if (hashalg)
  		crypto_free_shash(hashalg);
  	if (hmacalg)
  		crypto_free_shash(hmacalg);
  }
  
  static int __init encrypted_shash_alloc(void)
  {
  	int ret;
  
  	hmacalg = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC);
  	if (IS_ERR(hmacalg)) {
  		pr_info("encrypted_key: could not allocate crypto %s
  ",
  			hmac_alg);
  		return PTR_ERR(hmacalg);
  	}
  
  	hashalg = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC);
  	if (IS_ERR(hashalg)) {
  		pr_info("encrypted_key: could not allocate crypto %s
  ",
  			hash_alg);
  		ret = PTR_ERR(hashalg);
  		goto hashalg_fail;
  	}
  
  	return 0;
  
  hashalg_fail:
  	crypto_free_shash(hmacalg);
  	return ret;
  }
  
  static int __init init_encrypted(void)
  {
  	int ret;
  
  	ret = encrypted_shash_alloc();
  	if (ret < 0)
  		return ret;
  	ret = aes_get_sizes();
  	if (ret < 0)
  		goto out;
  	ret = register_key_type(&key_type_encrypted);
  	if (ret < 0)
  		goto out;
  	return 0;
  out:
  	encrypted_shash_release();
  	return ret;
  
  }
  
  static void __exit cleanup_encrypted(void)
  {
  	encrypted_shash_release();
  	unregister_key_type(&key_type_encrypted);
  }
  
  late_initcall(init_encrypted);
  module_exit(cleanup_encrypted);
  
  MODULE_LICENSE("GPL");