fs/crypto/fname.c - kernel/msm - Gitiles

 /*
  * This contains functions for filename crypto management
  *
  * Copyright (C) 2015, Google, Inc.
  * Copyright (C) 2015, Motorola Mobility
  *
  * Written by Uday Savagaonkar, 2014.
  * Modified by Jaegeuk Kim, 2015.
  *
  * This has not yet undergone a rigorous security audit.
  */

 #include <crypto/hash.h>
 #include <crypto/sha.h>
 #include <keys/encrypted-type.h>
 #include <keys/user-type.h>
 #include <linux/crypto.h>
 #include <linux/scatterlist.h>
 #include <linux/ratelimit.h>
 #include <linux/fscrypto.h>

 static u32 size_round_up(size_t size, size_t blksize)
 {
 	return ((size + blksize - 1) / blksize) * blksize;
 }

 /**
  * dir_crypt_complete() -
  */
 static void dir_crypt_complete(struct crypto_async_request *req, int res)
 {
 	struct fscrypt_completion_result *ecr = req->data;

 	if (res == -EINPROGRESS)
 		return;
 	ecr->res = res;
 	complete(&ecr->completion);
 }

 /**
  * fname_encrypt() -
  *
  * This function encrypts the input filename, and returns the length of the
  * ciphertext. Errors are returned as negative numbers.  We trust the caller to
  * allocate sufficient memory to oname string.
  */
 static int fname_encrypt(struct inode *inode,
 			const struct qstr *iname, struct fscrypt_str *oname)
 {
 	u32 ciphertext_len;
 	struct ablkcipher_request *req = NULL;
 	DECLARE_FS_COMPLETION_RESULT(ecr);
 	struct fscrypt_info *ci = inode->i_crypt_info;
 	struct crypto_ablkcipher *tfm = ci->ci_ctfm;
 	int res = 0;
 	char iv[FS_CRYPTO_BLOCK_SIZE];
 	struct scatterlist src_sg, dst_sg;
 	int padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
 	char *workbuf, buf[32], *alloc_buf = NULL;
 	unsigned lim;

 	lim = inode->i_sb->s_cop->max_namelen(inode);
 	if (iname->len <= 0 || iname->len > lim)
 		return -EIO;

 	ciphertext_len = (iname->len < FS_CRYPTO_BLOCK_SIZE) ?
 					FS_CRYPTO_BLOCK_SIZE : iname->len;
 	ciphertext_len = size_round_up(ciphertext_len, padding);
 	ciphertext_len = (ciphertext_len > lim) ? lim : ciphertext_len;

 	if (ciphertext_len <= sizeof(buf)) {
 		workbuf = buf;
 	} else {
 		alloc_buf = kmalloc(ciphertext_len, GFP_NOFS);
 		if (!alloc_buf)
 			return -ENOMEM;
 		workbuf = alloc_buf;
 	}

 	/* Allocate request */
 	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req) {
 		printk_ratelimited(KERN_ERR
 			"%s: crypto_request_alloc() failed\n", __func__);
 		kfree(alloc_buf);
 		return -ENOMEM;
 	}
 	ablkcipher_request_set_callback(req,
 			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 			dir_crypt_complete, &ecr);

 	/* Copy the input */
 	memcpy(workbuf, iname->name, iname->len);
 	if (iname->len < ciphertext_len)
 		memset(workbuf + iname->len, 0, ciphertext_len - iname->len);

 	/* Initialize IV */
 	memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);

 	/* Create encryption request */
 	sg_init_one(&src_sg, workbuf, ciphertext_len);
 	sg_init_one(&dst_sg, oname->name, ciphertext_len);
 	ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, ciphertext_len, iv);
 	res = crypto_ablkcipher_encrypt(req);
 	if (res == -EINPROGRESS || res == -EBUSY) {
 		wait_for_completion(&ecr.completion);
 		res = ecr.res;
 	}
 	kfree(alloc_buf);
 	ablkcipher_request_free(req);
 	if (res < 0)
 		printk_ratelimited(KERN_ERR
 				"%s: Error (error code %d)\n", __func__, res);

 	oname->len = ciphertext_len;
 	return res;
 }

 /*
  * fname_decrypt()
  *	This function decrypts the input filename, and returns
  *	the length of the plaintext.
  *	Errors are returned as negative numbers.
  *	We trust the caller to allocate sufficient memory to oname string.
  */
 static int fname_decrypt(struct inode *inode,
 				const struct fscrypt_str *iname,
 				struct fscrypt_str *oname)
 {
 	struct ablkcipher_request *req = NULL;
 	DECLARE_FS_COMPLETION_RESULT(ecr);
 	struct scatterlist src_sg, dst_sg;
 	struct fscrypt_info *ci = inode->i_crypt_info;
 	struct crypto_ablkcipher *tfm = ci->ci_ctfm;
 	int res = 0;
 	char iv[FS_CRYPTO_BLOCK_SIZE];
 	unsigned lim;

 	lim = inode->i_sb->s_cop->max_namelen(inode);
 	if (iname->len <= 0 || iname->len > lim)
 		return -EIO;

 	/* Allocate request */
 	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req) {
 		printk_ratelimited(KERN_ERR
 			"%s: crypto_request_alloc() failed\n",  __func__);
 		return -ENOMEM;
 	}
 	ablkcipher_request_set_callback(req,
 		CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 		dir_crypt_complete, &ecr);

 	/* Initialize IV */
 	memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);

 	/* Create decryption request */
 	sg_init_one(&src_sg, iname->name, iname->len);
 	sg_init_one(&dst_sg, oname->name, oname->len);
 	ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv);
 	res = crypto_ablkcipher_decrypt(req);
 	if (res == -EINPROGRESS || res == -EBUSY) {
 		wait_for_completion(&ecr.completion);
 		res = ecr.res;
 	}
 	ablkcipher_request_free(req);
 	if (res < 0) {
 		printk_ratelimited(KERN_ERR
 				"%s: Error (error code %d)\n", __func__, res);
 		return res;
 	}

 	oname->len = strnlen(oname->name, iname->len);
 	return oname->len;
 }

 static const char *lookup_table =
 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";

 /**
  * digest_encode() -
  *
  * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
  * The encoded string is roughly 4/3 times the size of the input string.
  */
 static int digest_encode(const char *src, int len, char *dst)
 {
 	int i = 0, bits = 0, ac = 0;
 	char *cp = dst;

 	while (i < len) {
 		ac += (((unsigned char) src[i]) << bits);
 		bits += 8;
 		do {
 			*cp++ = lookup_table[ac & 0x3f];
 			ac >>= 6;
 			bits -= 6;
 		} while (bits >= 6);
 		i++;
 	}
 	if (bits)
 		*cp++ = lookup_table[ac & 0x3f];
 	return cp - dst;
 }

 static int digest_decode(const char *src, int len, char *dst)
 {
 	int i = 0, bits = 0, ac = 0;
 	const char *p;
 	char *cp = dst;

 	while (i < len) {
 		p = strchr(lookup_table, src[i]);
 		if (p == NULL || src[i] == 0)
 			return -2;
 		ac += (p - lookup_table) << bits;
 		bits += 6;
 		if (bits >= 8) {
 			*cp++ = ac & 0xff;
 			ac >>= 8;
 			bits -= 8;
 		}
 		i++;
 	}
 	if (ac)
 		return -1;
 	return cp - dst;
 }

 u32 fscrypt_fname_encrypted_size(struct inode *inode, u32 ilen)
 {
 	int padding = 32;
 	struct fscrypt_info *ci = inode->i_crypt_info;

 	if (ci)
 		padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
 	if (ilen < FS_CRYPTO_BLOCK_SIZE)
 		ilen = FS_CRYPTO_BLOCK_SIZE;
 	return size_round_up(ilen, padding);
 }
 EXPORT_SYMBOL(fscrypt_fname_encrypted_size);

 /**
  * fscrypt_fname_crypto_alloc_obuff() -
  *
  * Allocates an output buffer that is sufficient for the crypto operation
  * specified by the context and the direction.
  */
 int fscrypt_fname_alloc_buffer(struct inode *inode,
 				u32 ilen, struct fscrypt_str *crypto_str)
 {
 	unsigned int olen = fscrypt_fname_encrypted_size(inode, ilen);

 	crypto_str->len = olen;
 	if (olen < FS_FNAME_CRYPTO_DIGEST_SIZE * 2)
 		olen = FS_FNAME_CRYPTO_DIGEST_SIZE * 2;
 	/*
 	 * Allocated buffer can hold one more character to null-terminate the
 	 * string
 	 */
 	crypto_str->name = kmalloc(olen + 1, GFP_NOFS);
 	if (!(crypto_str->name))
 		return -ENOMEM;
 	return 0;
 }
 EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);

 /**
  * fscrypt_fname_crypto_free_buffer() -
  *
  * Frees the buffer allocated for crypto operation.
  */
 void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
 {
 	if (!crypto_str)
 		return;
 	kfree(crypto_str->name);
 	crypto_str->name = NULL;
 }
 EXPORT_SYMBOL(fscrypt_fname_free_buffer);

 /**
  * fscrypt_fname_disk_to_usr() - converts a filename from disk space to user
  * space
  */
 int fscrypt_fname_disk_to_usr(struct inode *inode,
 			u32 hash, u32 minor_hash,
 			const struct fscrypt_str *iname,
 			struct fscrypt_str *oname)
 {
 	const struct qstr qname = FSTR_TO_QSTR(iname);
 	char buf[24];
 	int ret;

 	if (fscrypt_is_dot_dotdot(&qname)) {
 		oname->name[0] = '.';
 		oname->name[iname->len - 1] = '.';
 		oname->len = iname->len;
 		return oname->len;
 	}

 	if (iname->len < FS_CRYPTO_BLOCK_SIZE)
 		return -EUCLEAN;

 	if (inode->i_crypt_info)
 		return fname_decrypt(inode, iname, oname);

 	if (iname->len <= FS_FNAME_CRYPTO_DIGEST_SIZE) {
 		ret = digest_encode(iname->name, iname->len, oname->name);
 		oname->len = ret;
 		return ret;
 	}
 	if (hash) {
 		memcpy(buf, &hash, 4);
 		memcpy(buf + 4, &minor_hash, 4);
 	} else {
 		memset(buf, 0, 8);
 	}
 	memcpy(buf + 8, iname->name + iname->len - 16, 16);
 	oname->name[0] = '_';
 	ret = digest_encode(buf, 24, oname->name + 1);
 	oname->len = ret + 1;
 	return ret + 1;
 }
 EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);

 /**
  * fscrypt_fname_usr_to_disk() - converts a filename from user space to disk
  * space
  */
 int fscrypt_fname_usr_to_disk(struct inode *inode,
 			const struct qstr *iname,
 			struct fscrypt_str *oname)
 {
 	if (fscrypt_is_dot_dotdot(iname)) {
 		oname->name[0] = '.';
 		oname->name[iname->len - 1] = '.';
 		oname->len = iname->len;
 		return oname->len;
 	}
 	if (inode->i_crypt_info)
 		return fname_encrypt(inode, iname, oname);
 	/*
 	 * Without a proper key, a user is not allowed to modify the filenames
 	 * in a directory. Consequently, a user space name cannot be mapped to
 	 * a disk-space name
 	 */
 	return -EACCES;
 }
 EXPORT_SYMBOL(fscrypt_fname_usr_to_disk);

 int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 			      int lookup, struct fscrypt_name *fname)
 {
 	int ret = 0, bigname = 0;

 	memset(fname, 0, sizeof(struct fscrypt_name));
 	fname->usr_fname = iname;

 	if (!dir->i_sb->s_cop->is_encrypted(dir) ||
 				fscrypt_is_dot_dotdot(iname)) {
 		fname->disk_name.name = (unsigned char *)iname->name;
 		fname->disk_name.len = iname->len;
 		return 0;
 	}
 	ret = get_crypt_info(dir);
 	if (ret && ret != -EOPNOTSUPP)
 		return ret;

 	if (dir->i_crypt_info) {
 		ret = fscrypt_fname_alloc_buffer(dir, iname->len,
 							&fname->crypto_buf);
 		if (ret < 0)
 			return ret;
 		ret = fname_encrypt(dir, iname, &fname->crypto_buf);
 		if (ret < 0)
 			goto errout;
 		fname->disk_name.name = fname->crypto_buf.name;
 		fname->disk_name.len = fname->crypto_buf.len;
 		return 0;
 	}
 	if (!lookup)
 		return -EACCES;

 	/*
 	 * We don't have the key and we are doing a lookup; decode the
 	 * user-supplied name
 	 */
 	if (iname->name[0] == '_')
 		bigname = 1;
 	if ((bigname && (iname->len != 33)) || (!bigname && (iname->len > 43)))
 		return -ENOENT;

 	fname->crypto_buf.name = kmalloc(32, GFP_KERNEL);
 	if (fname->crypto_buf.name == NULL)
 		return -ENOMEM;

 	ret = digest_decode(iname->name + bigname, iname->len - bigname,
 				fname->crypto_buf.name);
 	if (ret < 0) {
 		ret = -ENOENT;
 		goto errout;
 	}
 	fname->crypto_buf.len = ret;
 	if (bigname) {
 		memcpy(&fname->hash, fname->crypto_buf.name, 4);
 		memcpy(&fname->minor_hash, fname->crypto_buf.name + 4, 4);
 	} else {
 		fname->disk_name.name = fname->crypto_buf.name;
 		fname->disk_name.len = fname->crypto_buf.len;
 	}
 	return 0;

 errout:
 	fscrypt_fname_free_buffer(&fname->crypto_buf);
 	return ret;
 }
 EXPORT_SYMBOL(fscrypt_setup_filename);

 void fscrypt_free_filename(struct fscrypt_name *fname)
 {
 	kfree(fname->crypto_buf.name);
 	fname->crypto_buf.name = NULL;
 	fname->usr_fname = NULL;
 	fname->disk_name.name = NULL;
 }
 EXPORT_SYMBOL(fscrypt_free_filename);
	/*
	* This contains functions for filename crypto management
	*
	* Copyright (C) 2015, Google, Inc.
	* Copyright (C) 2015, Motorola Mobility
	*
	* Written by Uday Savagaonkar, 2014.
	* Modified by Jaegeuk Kim, 2015.
	*
	* This has not yet undergone a rigorous security audit.
	*/

	#include <crypto/hash.h>
	#include <crypto/sha.h>
	#include <keys/encrypted-type.h>
	#include <keys/user-type.h>
	#include <linux/crypto.h>
	#include <linux/scatterlist.h>
	#include <linux/ratelimit.h>
	#include <linux/fscrypto.h>

	static u32 size_round_up(size_t size, size_t blksize)
	{
	return ((size + blksize - 1) / blksize) * blksize;
	}

	/**
	* dir_crypt_complete() -
	*/
	static void dir_crypt_complete(struct crypto_async_request *req, int res)
	{
	struct fscrypt_completion_result *ecr = req->data;

	if (res == -EINPROGRESS)
	return;
	ecr->res = res;
	complete(&ecr->completion);
	}

	/**
	* fname_encrypt() -
	*
	* This function encrypts the input filename, and returns the length of the
	* ciphertext. Errors are returned as negative numbers. We trust the caller to
	* allocate sufficient memory to oname string.
	*/
	static int fname_encrypt(struct inode *inode,
	const struct qstr iname, struct fscrypt_str oname)
	{
	u32 ciphertext_len;
	struct ablkcipher_request *req = NULL;
	DECLARE_FS_COMPLETION_RESULT(ecr);
	struct fscrypt_info *ci = inode->i_crypt_info;
	struct crypto_ablkcipher *tfm = ci->ci_ctfm;
	int res = 0;
	char iv[FS_CRYPTO_BLOCK_SIZE];
	struct scatterlist src_sg, dst_sg;
	int padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
	char workbuf, buf[32], alloc_buf = NULL;
	unsigned lim;

	lim = inode->i_sb->s_cop->max_namelen(inode);
	if (iname->len <= 0 \|\| iname->len > lim)
	return -EIO;

	ciphertext_len = (iname->len < FS_CRYPTO_BLOCK_SIZE) ?
	FS_CRYPTO_BLOCK_SIZE : iname->len;
	ciphertext_len = size_round_up(ciphertext_len, padding);
	ciphertext_len = (ciphertext_len > lim) ? lim : ciphertext_len;

	if (ciphertext_len <= sizeof(buf)) {
	workbuf = buf;
	} else {
	alloc_buf = kmalloc(ciphertext_len, GFP_NOFS);
	if (!alloc_buf)
	return -ENOMEM;
	workbuf = alloc_buf;
	}

	/* Allocate request */
	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
	if (!req) {
	printk_ratelimited(KERN_ERR
	"%s: crypto_request_alloc() failed\n", __func__);
	kfree(alloc_buf);
	return -ENOMEM;
	}
	ablkcipher_request_set_callback(req,
	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	dir_crypt_complete, &ecr);

	/* Copy the input */
	memcpy(workbuf, iname->name, iname->len);
	if (iname->len < ciphertext_len)
	memset(workbuf + iname->len, 0, ciphertext_len - iname->len);

	/* Initialize IV */
	memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);

	/* Create encryption request */
	sg_init_one(&src_sg, workbuf, ciphertext_len);
	sg_init_one(&dst_sg, oname->name, ciphertext_len);
	ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, ciphertext_len, iv);
	res = crypto_ablkcipher_encrypt(req);
	if (res == -EINPROGRESS \|\| res == -EBUSY) {
	wait_for_completion(&ecr.completion);
	res = ecr.res;
	}
	kfree(alloc_buf);
	ablkcipher_request_free(req);
	if (res < 0)
	printk_ratelimited(KERN_ERR
	"%s: Error (error code %d)\n", __func__, res);

	oname->len = ciphertext_len;
	return res;
	}

	/*
	* fname_decrypt()
	* This function decrypts the input filename, and returns
	* the length of the plaintext.
	* Errors are returned as negative numbers.
	* We trust the caller to allocate sufficient memory to oname string.
	*/
	static int fname_decrypt(struct inode *inode,
	const struct fscrypt_str *iname,
	struct fscrypt_str *oname)
	{
	struct ablkcipher_request *req = NULL;
	DECLARE_FS_COMPLETION_RESULT(ecr);
	struct scatterlist src_sg, dst_sg;
	struct fscrypt_info *ci = inode->i_crypt_info;
	struct crypto_ablkcipher *tfm = ci->ci_ctfm;
	int res = 0;
	char iv[FS_CRYPTO_BLOCK_SIZE];
	unsigned lim;

	lim = inode->i_sb->s_cop->max_namelen(inode);
	if (iname->len <= 0 \|\| iname->len > lim)
	return -EIO;

	/* Allocate request */
	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
	if (!req) {
	printk_ratelimited(KERN_ERR
	"%s: crypto_request_alloc() failed\n", __func__);
	return -ENOMEM;
	}
	ablkcipher_request_set_callback(req,
	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	dir_crypt_complete, &ecr);

	/* Initialize IV */
	memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);

	/* Create decryption request */
	sg_init_one(&src_sg, iname->name, iname->len);
	sg_init_one(&dst_sg, oname->name, oname->len);
	ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv);
	res = crypto_ablkcipher_decrypt(req);
	if (res == -EINPROGRESS \|\| res == -EBUSY) {
	wait_for_completion(&ecr.completion);
	res = ecr.res;
	}
	ablkcipher_request_free(req);
	if (res < 0) {
	printk_ratelimited(KERN_ERR
	"%s: Error (error code %d)\n", __func__, res);
	return res;
	}

	oname->len = strnlen(oname->name, iname->len);
	return oname->len;
	}

	static const char *lookup_table =
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";

	/**
	* digest_encode() -
	*
	* Encodes the input digest using characters from the set [a-zA-Z0-9_+].
	* The encoded string is roughly 4/3 times the size of the input string.
	*/
	static int digest_encode(const char src, int len, char dst)
	{
	int i = 0, bits = 0, ac = 0;
	char *cp = dst;

	while (i < len) {
	ac += (((unsigned char) src[i]) << bits);
	bits += 8;
	do {
	*cp++ = lookup_table[ac & 0x3f];
	ac >>= 6;
	bits -= 6;
	} while (bits >= 6);
	i++;
	}
	if (bits)
	*cp++ = lookup_table[ac & 0x3f];
	return cp - dst;
	}

	static int digest_decode(const char src, int len, char dst)
	{
	int i = 0, bits = 0, ac = 0;
	const char *p;
	char *cp = dst;

	while (i < len) {
	p = strchr(lookup_table, src[i]);
	if (p == NULL \|\| src[i] == 0)
	return -2;
	ac += (p - lookup_table) << bits;
	bits += 6;
	if (bits >= 8) {
	*cp++ = ac & 0xff;
	ac >>= 8;
	bits -= 8;
	}
	i++;
	}
	if (ac)
	return -1;
	return cp - dst;
	}

	u32 fscrypt_fname_encrypted_size(struct inode *inode, u32 ilen)
	{
	int padding = 32;
	struct fscrypt_info *ci = inode->i_crypt_info;

	if (ci)
	padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
	if (ilen < FS_CRYPTO_BLOCK_SIZE)
	ilen = FS_CRYPTO_BLOCK_SIZE;
	return size_round_up(ilen, padding);
	}
	EXPORT_SYMBOL(fscrypt_fname_encrypted_size);

	/**
	* fscrypt_fname_crypto_alloc_obuff() -
	*
	* Allocates an output buffer that is sufficient for the crypto operation
	* specified by the context and the direction.
	*/
	int fscrypt_fname_alloc_buffer(struct inode *inode,
	u32 ilen, struct fscrypt_str *crypto_str)
	{
	unsigned int olen = fscrypt_fname_encrypted_size(inode, ilen);

	crypto_str->len = olen;
	if (olen < FS_FNAME_CRYPTO_DIGEST_SIZE * 2)
	olen = FS_FNAME_CRYPTO_DIGEST_SIZE * 2;
	/*
	* Allocated buffer can hold one more character to null-terminate the
	* string
	*/
	crypto_str->name = kmalloc(olen + 1, GFP_NOFS);
	if (!(crypto_str->name))
	return -ENOMEM;
	return 0;
	}
	EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);

	/**
	* fscrypt_fname_crypto_free_buffer() -
	*
	* Frees the buffer allocated for crypto operation.
	*/
	void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
	{
	if (!crypto_str)
	return;
	kfree(crypto_str->name);
	crypto_str->name = NULL;
	}
	EXPORT_SYMBOL(fscrypt_fname_free_buffer);

	/**
	* fscrypt_fname_disk_to_usr() - converts a filename from disk space to user
	* space
	*/
	int fscrypt_fname_disk_to_usr(struct inode *inode,
	u32 hash, u32 minor_hash,
	const struct fscrypt_str *iname,
	struct fscrypt_str *oname)
	{
	const struct qstr qname = FSTR_TO_QSTR(iname);
	char buf[24];
	int ret;

	if (fscrypt_is_dot_dotdot(&qname)) {
	oname->name[0] = '.';
	oname->name[iname->len - 1] = '.';
	oname->len = iname->len;
	return oname->len;
	}

	if (iname->len < FS_CRYPTO_BLOCK_SIZE)
	return -EUCLEAN;

	if (inode->i_crypt_info)
	return fname_decrypt(inode, iname, oname);

	if (iname->len <= FS_FNAME_CRYPTO_DIGEST_SIZE) {
	ret = digest_encode(iname->name, iname->len, oname->name);
	oname->len = ret;
	return ret;
	}
	if (hash) {
	memcpy(buf, &hash, 4);
	memcpy(buf + 4, &minor_hash, 4);
	} else {
	memset(buf, 0, 8);
	}
	memcpy(buf + 8, iname->name + iname->len - 16, 16);
	oname->name[0] = '_';
	ret = digest_encode(buf, 24, oname->name + 1);
	oname->len = ret + 1;
	return ret + 1;
	}
	EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);

	/**
	* fscrypt_fname_usr_to_disk() - converts a filename from user space to disk
	* space
	*/
	int fscrypt_fname_usr_to_disk(struct inode *inode,
	const struct qstr *iname,
	struct fscrypt_str *oname)
	{
	if (fscrypt_is_dot_dotdot(iname)) {
	oname->name[0] = '.';
	oname->name[iname->len - 1] = '.';
	oname->len = iname->len;
	return oname->len;
	}
	if (inode->i_crypt_info)
	return fname_encrypt(inode, iname, oname);
	/*
	* Without a proper key, a user is not allowed to modify the filenames
	* in a directory. Consequently, a user space name cannot be mapped to
	* a disk-space name
	*/
	return -EACCES;
	}
	EXPORT_SYMBOL(fscrypt_fname_usr_to_disk);

	int fscrypt_setup_filename(struct inode dir, const struct qstr iname,
	int lookup, struct fscrypt_name *fname)
	{
	int ret = 0, bigname = 0;

	memset(fname, 0, sizeof(struct fscrypt_name));
	fname->usr_fname = iname;

	if (!dir->i_sb->s_cop->is_encrypted(dir) \|\|
	fscrypt_is_dot_dotdot(iname)) {
	fname->disk_name.name = (unsigned char *)iname->name;
	fname->disk_name.len = iname->len;
	return 0;
	}
	ret = get_crypt_info(dir);
	if (ret && ret != -EOPNOTSUPP)
	return ret;

	if (dir->i_crypt_info) {
	ret = fscrypt_fname_alloc_buffer(dir, iname->len,
	&fname->crypto_buf);
	if (ret < 0)
	return ret;
	ret = fname_encrypt(dir, iname, &fname->crypto_buf);
	if (ret < 0)
	goto errout;
	fname->disk_name.name = fname->crypto_buf.name;
	fname->disk_name.len = fname->crypto_buf.len;
	return 0;
	}
	if (!lookup)
	return -EACCES;

	/*
	* We don't have the key and we are doing a lookup; decode the
	* user-supplied name
	*/
	if (iname->name[0] == '_')
	bigname = 1;
	if ((bigname && (iname->len != 33)) \|\| (!bigname && (iname->len > 43)))
	return -ENOENT;

	fname->crypto_buf.name = kmalloc(32, GFP_KERNEL);
	if (fname->crypto_buf.name == NULL)
	return -ENOMEM;

	ret = digest_decode(iname->name + bigname, iname->len - bigname,
	fname->crypto_buf.name);
	if (ret < 0) {
	ret = -ENOENT;
	goto errout;
	}
	fname->crypto_buf.len = ret;
	if (bigname) {
	memcpy(&fname->hash, fname->crypto_buf.name, 4);
	memcpy(&fname->minor_hash, fname->crypto_buf.name + 4, 4);
	} else {
	fname->disk_name.name = fname->crypto_buf.name;
	fname->disk_name.len = fname->crypto_buf.len;
	}
	return 0;

	errout:
	fscrypt_fname_free_buffer(&fname->crypto_buf);
	return ret;
	}
	EXPORT_SYMBOL(fscrypt_setup_filename);

	void fscrypt_free_filename(struct fscrypt_name *fname)
	{
	kfree(fname->crypto_buf.name);
	fname->crypto_buf.name = NULL;
	fname->usr_fname = NULL;
	fname->disk_name.name = NULL;
	}
	EXPORT_SYMBOL(fscrypt_free_filename);