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41 results

encrypted.c

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  • Forked from hardware-enablement / Rockchip upstream enablement efforts / linux
    Source project has a limited visibility.
    encrypted.c 26.00 KiB
    /*
     * 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)\n",
    		       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\n", 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\n");
    			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\n");
    		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\n");
    		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\n");
    		goto out;
    	}
    
    	if (valid_master_desc(*master_desc, NULL) < 0) {
    		pr_info("encrypted_key: master key parameter \'%s\' "
    			"is invalid\n", *master_desc);
    		goto out;
    	}
    
    	if (decrypted_datalen) {
    		*decrypted_datalen = strsep(&datablob, " \t");
    		if (!*decrypted_datalen) {
    			pr_info("encrypted_key: keylen parameter is missing\n");
    			goto out;
    		}
    	}
    
    	switch (key_cmd) {
    	case Opt_new:
    		if (!decrypted_datalen) {
    			pr_info("encrypted_key: keyword \'%s\' not allowed "
    				"when called from .update method\n", keyword);
    			break;
    		}
    		ret = 0;
    		break;
    	case Opt_load:
    		if (!decrypted_datalen) {
    			pr_info("encrypted_key: keyword \'%s\' not allowed "
    				"when called from .update method\n", keyword);
    			break;
    		}
    		*hex_encoded_iv = strsep(&datablob, " \t");
    		if (!*hex_encoded_iv) {
    			pr_info("encrypted_key: hex blob is missing\n");
    			break;
    		}
    		ret = 0;
    		break;
    	case Opt_update:
    		if (decrypted_datalen) {
    			pr_info("encrypted_key: keyword \'%s\' not allowed "
    				"when called from .instantiate method\n",
    				keyword);
    			break;
    		}
    		ret = 0;
    		break;
    	case Opt_err:
    		pr_info("encrypted_key: keyword \'%s\' not recognized\n",
    			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 = rcu_dereference(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\n", 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\n", 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\n");
    		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)\n",
    		       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)\n", 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)\n", 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\n",
    			       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)\n", 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)\n", 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, const void *data,
    				 size_t datalen)
    {
    	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;
    	int ret;
    
    	if (datalen <= 0 || datalen > 32767 || !data)
    		return -EINVAL;
    
    	datablob = kmalloc(datalen + 1, GFP_KERNEL);
    	if (!datablob)
    		return -ENOMEM;
    	datablob[datalen] = 0;
    	memcpy(datablob, 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, const void *data, size_t datalen)
    {
    	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;
    	int ret = 0;
    
    	if (datalen <= 0 || datalen > 32767 || !data)
    		return -EINVAL;
    
    	buf = kmalloc(datalen + 1, GFP_KERNEL);
    	if (!buf)
    		return -ENOMEM;
    
    	buf[datalen] = 0;
    	memcpy(buf, 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\n",
    			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\n",
    			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 = register_key_type(&key_type_encrypted);
    	if (ret < 0)
    		goto out;
    	return aes_get_sizes();
    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");