/*
   * linux/fs/f2fs/crypto_fname.c
   *
   * Copied from linux/fs/ext4/crypto.c
   *
   * Copyright (C) 2015, Google, Inc.
   * Copyright (C) 2015, Motorola Mobility
   *
   * This contains functions for filename crypto management in f2fs
   *
   * Written by Uday Savagaonkar, 2014.
   *
   * Adjust f2fs dentry structure
   *	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/gfp.h>
  #include <linux/kernel.h>
  #include <linux/key.h>
  #include <linux/list.h>
  #include <linux/mempool.h>
  #include <linux/random.h>
  #include <linux/scatterlist.h>
  #include <linux/spinlock_types.h>
  #include <linux/f2fs_fs.h>
  #include <linux/ratelimit.h>
  
  #include "f2fs.h"
  #include "f2fs_crypto.h"
  #include "xattr.h"
  
  /**
   * f2fs_dir_crypt_complete() -
   */
  static void f2fs_dir_crypt_complete(struct crypto_async_request *req, int res)
  {
  	struct f2fs_completion_result *ecr = req->data;
  
  	if (res == -EINPROGRESS)
  		return;
  	ecr->res = res;
  	complete(&ecr->completion);
  }
  
  bool f2fs_valid_filenames_enc_mode(uint32_t mode)
  {
  	return (mode == F2FS_ENCRYPTION_MODE_AES_256_CTS);
  }
  
  static unsigned max_name_len(struct inode *inode)
  {
  	return S_ISLNK(inode->i_mode) ? inode->i_sb->s_blocksize :
  					F2FS_NAME_LEN;
  }
  
  /**
   * f2fs_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 f2fs_fname_encrypt(struct inode *inode,
  			const struct qstr *iname, struct f2fs_str *oname)
  {
  	u32 ciphertext_len;
  	struct ablkcipher_request *req = NULL;
  	DECLARE_F2FS_COMPLETION_RESULT(ecr);
  	struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
  	struct crypto_ablkcipher *tfm = ci->ci_ctfm;
  	int res = 0;
  	char iv[F2FS_CRYPTO_BLOCK_SIZE];
  	struct scatterlist src_sg, dst_sg;
  	int padding = 4 << (ci->ci_flags & F2FS_POLICY_FLAGS_PAD_MASK);
  	char *workbuf, buf[32], *alloc_buf = NULL;
  	unsigned lim = max_name_len(inode);
  
  	if (iname->len <= 0 || iname->len > lim)
  		return -EIO;
  
  	ciphertext_len = (iname->len < F2FS_CRYPTO_BLOCK_SIZE) ?
  		F2FS_CRYPTO_BLOCK_SIZE : iname->len;
  	ciphertext_len = f2fs_fname_crypto_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
  ", __func__);
  		kfree(alloc_buf);
  		return -ENOMEM;
  	}
  	ablkcipher_request_set_callback(req,
  			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
  			f2fs_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, F2FS_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) {
  		BUG_ON(req->base.data != &ecr);
  		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)
  ", __func__, res);
  	}
  	oname->len = ciphertext_len;
  	return res;
  }
  
  /*
   * f2fs_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 f2fs_fname_decrypt(struct inode *inode,
  			const struct f2fs_str *iname, struct f2fs_str *oname)
  {
  	struct ablkcipher_request *req = NULL;
  	DECLARE_F2FS_COMPLETION_RESULT(ecr);
  	struct scatterlist src_sg, dst_sg;
  	struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
  	struct crypto_ablkcipher *tfm = ci->ci_ctfm;
  	int res = 0;
  	char iv[F2FS_CRYPTO_BLOCK_SIZE];
  	unsigned lim = max_name_len(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
  ",  __func__);
  		return -ENOMEM;
  	}
  	ablkcipher_request_set_callback(req,
  		CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
  		f2fs_dir_crypt_complete, &ecr);
  
  	/* Initialize IV */
  	memset(iv, 0, F2FS_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) {
  		BUG_ON(req->base.data != &ecr);
  		wait_for_completion(&ecr.completion);
  		res = ecr.res;
  	}
  	ablkcipher_request_free(req);
  	if (res < 0) {
  		printk_ratelimited(KERN_ERR
  			"%s: Error in f2fs_fname_decrypt (error code %d)
  ",
  			__func__, res);
  		return res;
  	}
  
  	oname->len = strnlen(oname->name, iname->len);
  	return oname->len;
  }
  
  static const char *lookup_table =
  	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
  
  /**
   * f2fs_fname_encode_digest() -
   *
   * 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;
  }
  
  /**
   * f2fs_fname_crypto_round_up() -
   *
   * Return: The next multiple of block size
   */
  u32 f2fs_fname_crypto_round_up(u32 size, u32 blksize)
  {
  	return ((size + blksize - 1) / blksize) * blksize;
  }
  
  /**
   * f2fs_fname_crypto_alloc_obuff() -
   *
   * Allocates an output buffer that is sufficient for the crypto operation
   * specified by the context and the direction.
   */
  int f2fs_fname_crypto_alloc_buffer(struct inode *inode,
  				   u32 ilen, struct f2fs_str *crypto_str)
  {
  	unsigned int olen;
  	int padding = 16;
  	struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
  
  	if (ci)
  		padding = 4 << (ci->ci_flags & F2FS_POLICY_FLAGS_PAD_MASK);
  	if (padding < F2FS_CRYPTO_BLOCK_SIZE)
  		padding = F2FS_CRYPTO_BLOCK_SIZE;
  	olen = f2fs_fname_crypto_round_up(ilen, padding);
  	crypto_str->len = olen;
  	if (olen < F2FS_FNAME_CRYPTO_DIGEST_SIZE * 2)
  		olen = F2FS_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;
  }
  
  /**
   * f2fs_fname_crypto_free_buffer() -
   *
   * Frees the buffer allocated for crypto operation.
   */
  void f2fs_fname_crypto_free_buffer(struct f2fs_str *crypto_str)
  {
  	if (!crypto_str)
  		return;
  	kfree(crypto_str->name);
  	crypto_str->name = NULL;
  }
  
  /**
   * f2fs_fname_disk_to_usr() - converts a filename from disk space to user space
   */
  int f2fs_fname_disk_to_usr(struct inode *inode,
  			f2fs_hash_t *hash,
  			const struct f2fs_str *iname,
  			struct f2fs_str *oname)
  {
  	const struct qstr qname = FSTR_TO_QSTR(iname);
  	char buf[24];
  	int ret;
  
  	if (is_dot_dotdot(&qname)) {
  		oname->name[0] = '.';
  		oname->name[iname->len - 1] = '.';
  		oname->len = iname->len;
  		return oname->len;
  	}
  
  	if (F2FS_I(inode)->i_crypt_info)
  		return f2fs_fname_decrypt(inode, iname, oname);
  
  	if (iname->len <= F2FS_FNAME_CRYPTO_DIGEST_SIZE) {
  		ret = digest_encode(iname->name, iname->len, oname->name);
  		oname->len = ret;
  		return ret;
  	}
  	if (hash) {
  		memcpy(buf, hash, 4);
  		memset(buf + 4, 0, 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;
  }
  
  /**
   * f2fs_fname_usr_to_disk() - converts a filename from user space to disk space
   */
  int f2fs_fname_usr_to_disk(struct inode *inode,
  			const struct qstr *iname,
  			struct f2fs_str *oname)
  {
  	int res;
  	struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
  
  	if (is_dot_dotdot(iname)) {
  		oname->name[0] = '.';
  		oname->name[iname->len - 1] = '.';
  		oname->len = iname->len;
  		return oname->len;
  	}
  
  	if (ci) {
  		res = f2fs_fname_encrypt(inode, iname, oname);
  		return res;
  	}
  	/* 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;
  }
  
  int f2fs_fname_setup_filename(struct inode *dir, const struct qstr *iname,
  			      int lookup, struct f2fs_filename *fname)
  {
  	struct f2fs_crypt_info *ci;
  	int ret = 0, bigname = 0;
  
  	memset(fname, 0, sizeof(struct f2fs_filename));
  	fname->usr_fname = iname;
  
  	if (!f2fs_encrypted_inode(dir) || is_dot_dotdot(iname)) {
  		fname->disk_name.name = (unsigned char *)iname->name;
  		fname->disk_name.len = iname->len;
  		return 0;
  	}
  	ret = f2fs_get_encryption_info(dir);
  	if (ret)
  		return ret;
  	ci = F2FS_I(dir)->i_crypt_info;
  	if (ci) {
  		ret = f2fs_fname_crypto_alloc_buffer(dir, iname->len,
  						     &fname->crypto_buf);
  		if (ret < 0)
  			return ret;
  		ret = f2fs_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);
  	} else {
  		fname->disk_name.name = fname->crypto_buf.name;
  		fname->disk_name.len = fname->crypto_buf.len;
  	}
  	return 0;
  errout:
  	f2fs_fname_crypto_free_buffer(&fname->crypto_buf);
  	return ret;
  }
  
  void f2fs_fname_free_filename(struct f2fs_filename *fname)
  {
  	kfree(fname->crypto_buf.name);
  	fname->crypto_buf.name = NULL;
  	fname->usr_fname = NULL;
  	fname->disk_name.name = NULL;
  }