/*
   * linux/fs/f2fs/crypto_key.c
   *
   * Copied from linux/fs/f2fs/crypto_key.c
   *
   * Copyright (C) 2015, Google, Inc.
   *
   * This contains encryption key functions for f2fs
   *
   * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
   */
  #include <keys/encrypted-type.h>
  #include <keys/user-type.h>
  #include <linux/random.h>
  #include <linux/scatterlist.h>
  #include <uapi/linux/keyctl.h>
  #include <crypto/hash.h>
  #include <linux/f2fs_fs.h>
  
  #include "f2fs.h"
  #include "xattr.h"
  
  static void derive_crypt_complete(struct crypto_async_request *req, int rc)
  {
  	struct f2fs_completion_result *ecr = req->data;
  
  	if (rc == -EINPROGRESS)
  		return;
  
  	ecr->res = rc;
  	complete(&ecr->completion);
  }
  
  /**
   * f2fs_derive_key_aes() - Derive a key using AES-128-ECB
   * @deriving_key: Encryption key used for derivatio.
   * @source_key:   Source key to which to apply derivation.
   * @derived_key:  Derived key.
   *
   * Return: Zero on success; non-zero otherwise.
   */
  static int f2fs_derive_key_aes(char deriving_key[F2FS_AES_128_ECB_KEY_SIZE],
  				char source_key[F2FS_AES_256_XTS_KEY_SIZE],
  				char derived_key[F2FS_AES_256_XTS_KEY_SIZE])
  {
  	int res = 0;
  	struct ablkcipher_request *req = NULL;
  	DECLARE_F2FS_COMPLETION_RESULT(ecr);
  	struct scatterlist src_sg, dst_sg;
  	struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0,
  								0);
  
  	if (IS_ERR(tfm)) {
  		res = PTR_ERR(tfm);
  		tfm = NULL;
  		goto out;
  	}
  	crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
  	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
  	if (!req) {
  		res = -ENOMEM;
  		goto out;
  	}
  	ablkcipher_request_set_callback(req,
  			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
  			derive_crypt_complete, &ecr);
  	res = crypto_ablkcipher_setkey(tfm, deriving_key,
  				F2FS_AES_128_ECB_KEY_SIZE);
  	if (res < 0)
  		goto out;
  
  	sg_init_one(&src_sg, source_key, F2FS_AES_256_XTS_KEY_SIZE);
  	sg_init_one(&dst_sg, derived_key, F2FS_AES_256_XTS_KEY_SIZE);
  	ablkcipher_request_set_crypt(req, &src_sg, &dst_sg,
  					F2FS_AES_256_XTS_KEY_SIZE, NULL);
  	res = crypto_ablkcipher_encrypt(req);
  	if (res == -EINPROGRESS || res == -EBUSY) {
  		BUG_ON(req->base.data != &ecr);
  		wait_for_completion(&ecr.completion);
  		res = ecr.res;
  	}
  out:
  	if (req)
  		ablkcipher_request_free(req);
  	if (tfm)
  		crypto_free_ablkcipher(tfm);
  	return res;
  }
  
  static void f2fs_free_crypt_info(struct f2fs_crypt_info *ci)
  {
  	if (!ci)
  		return;
  
  	key_put(ci->ci_keyring_key);
  	crypto_free_ablkcipher(ci->ci_ctfm);
  	kmem_cache_free(f2fs_crypt_info_cachep, ci);
  }
  
  void f2fs_free_encryption_info(struct inode *inode, struct f2fs_crypt_info *ci)
  {
  	struct f2fs_inode_info *fi = F2FS_I(inode);
  	struct f2fs_crypt_info *prev;
  
  	if (ci == NULL)
  		ci = ACCESS_ONCE(fi->i_crypt_info);
  	if (ci == NULL)
  		return;
  	prev = cmpxchg(&fi->i_crypt_info, ci, NULL);
  	if (prev != ci)
  		return;
  
  	f2fs_free_crypt_info(ci);
  }
  
  int _f2fs_get_encryption_info(struct inode *inode)
  {
  	struct f2fs_inode_info *fi = F2FS_I(inode);
  	struct f2fs_crypt_info *crypt_info;
  	char full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
  				(F2FS_KEY_DESCRIPTOR_SIZE * 2) + 1];
  	struct key *keyring_key = NULL;
  	struct f2fs_encryption_key *master_key;
  	struct f2fs_encryption_context ctx;
  	const struct user_key_payload *ukp;
  	struct crypto_ablkcipher *ctfm;
  	const char *cipher_str;
  	char raw_key[F2FS_MAX_KEY_SIZE];
  	char mode;
  	int res;
  
  	res = f2fs_crypto_initialize();
  	if (res)
  		return res;
  retry:
  	crypt_info = ACCESS_ONCE(fi->i_crypt_info);
  	if (crypt_info) {
  		if (!crypt_info->ci_keyring_key ||
  				key_validate(crypt_info->ci_keyring_key) == 0)
  			return 0;
  		f2fs_free_encryption_info(inode, crypt_info);
  		goto retry;
  	}
  
  	res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
  				F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
  				&ctx, sizeof(ctx), NULL);
  	if (res < 0)
  		return res;
  	else if (res != sizeof(ctx))
  		return -EINVAL;
  	res = 0;
  
  	crypt_info = kmem_cache_alloc(f2fs_crypt_info_cachep, GFP_NOFS);
  	if (!crypt_info)
  		return -ENOMEM;
  
  	crypt_info->ci_flags = ctx.flags;
  	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
  	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
  	crypt_info->ci_ctfm = NULL;
  	crypt_info->ci_keyring_key = NULL;
  	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
  				sizeof(crypt_info->ci_master_key));
  	if (S_ISREG(inode->i_mode))
  		mode = crypt_info->ci_data_mode;
  	else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
  		mode = crypt_info->ci_filename_mode;
  	else
  		BUG();
  
  	switch (mode) {
  	case F2FS_ENCRYPTION_MODE_AES_256_XTS:
  		cipher_str = "xts(aes)";
  		break;
  	case F2FS_ENCRYPTION_MODE_AES_256_CTS:
  		cipher_str = "cts(cbc(aes))";
  		break;
  	default:
  		printk_once(KERN_WARNING
  			    "f2fs: unsupported key mode %d (ino %u)
  ",
  			    mode, (unsigned) inode->i_ino);
  		res = -ENOKEY;
  		goto out;
  	}
  
  	memcpy(full_key_descriptor, F2FS_KEY_DESC_PREFIX,
  					F2FS_KEY_DESC_PREFIX_SIZE);
  	sprintf(full_key_descriptor + F2FS_KEY_DESC_PREFIX_SIZE,
  					"%*phN", F2FS_KEY_DESCRIPTOR_SIZE,
  					ctx.master_key_descriptor);
  	full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
  					(2 * F2FS_KEY_DESCRIPTOR_SIZE)] = '\0';
  	keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
  	if (IS_ERR(keyring_key)) {
  		res = PTR_ERR(keyring_key);
  		keyring_key = NULL;
  		goto out;
  	}
  	crypt_info->ci_keyring_key = keyring_key;
  	BUG_ON(keyring_key->type != &key_type_logon);
  	ukp = user_key_payload(keyring_key);
  	if (ukp->datalen != sizeof(struct f2fs_encryption_key)) {
  		res = -EINVAL;
  		goto out;
  	}
  	master_key = (struct f2fs_encryption_key *)ukp->data;
  	BUILD_BUG_ON(F2FS_AES_128_ECB_KEY_SIZE !=
  				F2FS_KEY_DERIVATION_NONCE_SIZE);
  	BUG_ON(master_key->size != F2FS_AES_256_XTS_KEY_SIZE);
  	res = f2fs_derive_key_aes(ctx.nonce, master_key->raw,
  				  raw_key);
  	if (res)
  		goto out;
  
  	ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
  	if (!ctfm || IS_ERR(ctfm)) {
  		res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
  		printk(KERN_DEBUG
  		       "%s: error %d (inode %u) allocating crypto tfm
  ",
  		       __func__, res, (unsigned) inode->i_ino);
  		goto out;
  	}
  	crypt_info->ci_ctfm = ctfm;
  	crypto_ablkcipher_clear_flags(ctfm, ~0);
  	crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
  			     CRYPTO_TFM_REQ_WEAK_KEY);
  	res = crypto_ablkcipher_setkey(ctfm, raw_key,
  					f2fs_encryption_key_size(mode));
  	if (res)
  		goto out;
  
  	memzero_explicit(raw_key, sizeof(raw_key));
  	if (cmpxchg(&fi->i_crypt_info, NULL, crypt_info) != NULL) {
  		f2fs_free_crypt_info(crypt_info);
  		goto retry;
  	}
  	return 0;
  
  out:
  	if (res == -ENOKEY && !S_ISREG(inode->i_mode))
  		res = 0;
  
  	f2fs_free_crypt_info(crypt_info);
  	memzero_explicit(raw_key, sizeof(raw_key));
  	return res;
  }
  
  int f2fs_has_encryption_key(struct inode *inode)
  {
  	struct f2fs_inode_info *fi = F2FS_I(inode);
  
  	return (fi->i_crypt_info != NULL);
  }