fs/crypto/keyinfo.c - arm/linux - Git at Google

 /*
  * key management facility for FS encryption support.
  *
  * Copyright (C) 2015, Google, Inc.
  *
  * This contains encryption key functions.
  *
  * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
  */

 #include <keys/user-type.h>
 #include <linux/scatterlist.h>
 #include "fscrypt_private.h"

 static void derive_crypt_complete(struct crypto_async_request *req, int rc)
 {
 	struct fscrypt_completion_result *ecr = req->data;

 	if (rc == -EINPROGRESS)
 		return;

 	ecr->res = rc;
 	complete(&ecr->completion);
 }

 /**
  * derive_key_aes() - Derive a key using AES-128-ECB
  * @deriving_key: Encryption key used for derivation.
  * @source_key:   Source key to which to apply derivation.
  * @derived_key:  Derived key.
  *
  * Return: Zero on success; non-zero otherwise.
  */
 static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE],
 				u8 source_key[FS_AES_256_XTS_KEY_SIZE],
 				u8 derived_key[FS_AES_256_XTS_KEY_SIZE])
 {
 	int res = 0;
 	struct skcipher_request *req = NULL;
 	DECLARE_FS_COMPLETION_RESULT(ecr);
 	struct scatterlist src_sg, dst_sg;
 	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);

 	if (IS_ERR(tfm)) {
 		res = PTR_ERR(tfm);
 		tfm = NULL;
 		goto out;
 	}
 	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
 	req = skcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req) {
 		res = -ENOMEM;
 		goto out;
 	}
 	skcipher_request_set_callback(req,
 			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 			derive_crypt_complete, &ecr);
 	res = crypto_skcipher_setkey(tfm, deriving_key,
 					FS_AES_128_ECB_KEY_SIZE);
 	if (res < 0)
 		goto out;

 	sg_init_one(&src_sg, source_key, FS_AES_256_XTS_KEY_SIZE);
 	sg_init_one(&dst_sg, derived_key, FS_AES_256_XTS_KEY_SIZE);
 	skcipher_request_set_crypt(req, &src_sg, &dst_sg,
 					FS_AES_256_XTS_KEY_SIZE, NULL);
 	res = crypto_skcipher_encrypt(req);
 	if (res == -EINPROGRESS || res == -EBUSY) {
 		wait_for_completion(&ecr.completion);
 		res = ecr.res;
 	}
 out:
 	skcipher_request_free(req);
 	crypto_free_skcipher(tfm);
 	return res;
 }

 static int validate_user_key(struct fscrypt_info *crypt_info,
 			struct fscrypt_context *ctx, u8 *raw_key,
 			const char *prefix)
 {
 	char *description;
 	struct key *keyring_key;
 	struct fscrypt_key *master_key;
 	const struct user_key_payload *ukp;
 	int res;

 	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
 				FS_KEY_DESCRIPTOR_SIZE,
 				ctx->master_key_descriptor);
 	if (!description)
 		return -ENOMEM;

 	keyring_key = request_key(&key_type_logon, description, NULL);
 	kfree(description);
 	if (IS_ERR(keyring_key))
 		return PTR_ERR(keyring_key);
 	down_read(&keyring_key->sem);

 	if (keyring_key->type != &key_type_logon) {
 		printk_once(KERN_WARNING
 				"%s: key type must be logon\n", __func__);
 		res = -ENOKEY;
 		goto out;
 	}
 	ukp = user_key_payload_locked(keyring_key);
 	if (ukp->datalen != sizeof(struct fscrypt_key)) {
 		res = -EINVAL;
 		goto out;
 	}
 	master_key = (struct fscrypt_key *)ukp->data;
 	BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE);

 	if (master_key->size != FS_AES_256_XTS_KEY_SIZE) {
 		printk_once(KERN_WARNING
 				"%s: key size incorrect: %d\n",
 				__func__, master_key->size);
 		res = -ENOKEY;
 		goto out;
 	}
 	res = derive_key_aes(ctx->nonce, master_key->raw, raw_key);
 out:
 	up_read(&keyring_key->sem);
 	key_put(keyring_key);
 	return res;
 }

 static int determine_cipher_type(struct fscrypt_info *ci, struct inode *inode,
 				 const char **cipher_str_ret, int *keysize_ret)
 {
 	if (S_ISREG(inode->i_mode)) {
 		if (ci->ci_data_mode == FS_ENCRYPTION_MODE_AES_256_XTS) {
 			*cipher_str_ret = "xts(aes)";
 			*keysize_ret = FS_AES_256_XTS_KEY_SIZE;
 			return 0;
 		}
 		pr_warn_once("fscrypto: unsupported contents encryption mode "
 			     "%d for inode %lu\n",
 			     ci->ci_data_mode, inode->i_ino);
 		return -ENOKEY;
 	}

 	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) {
 		if (ci->ci_filename_mode == FS_ENCRYPTION_MODE_AES_256_CTS) {
 			*cipher_str_ret = "cts(cbc(aes))";
 			*keysize_ret = FS_AES_256_CTS_KEY_SIZE;
 			return 0;
 		}
 		pr_warn_once("fscrypto: unsupported filenames encryption mode "
 			     "%d for inode %lu\n",
 			     ci->ci_filename_mode, inode->i_ino);
 		return -ENOKEY;
 	}

 	pr_warn_once("fscrypto: unsupported file type %d for inode %lu\n",
 		     (inode->i_mode & S_IFMT), inode->i_ino);
 	return -ENOKEY;
 }

 static void put_crypt_info(struct fscrypt_info *ci)
 {
 	if (!ci)
 		return;

 	crypto_free_skcipher(ci->ci_ctfm);
 	kmem_cache_free(fscrypt_info_cachep, ci);
 }

 int fscrypt_get_encryption_info(struct inode *inode)
 {
 	struct fscrypt_info *crypt_info;
 	struct fscrypt_context ctx;
 	struct crypto_skcipher *ctfm;
 	const char *cipher_str;
 	int keysize;
 	u8 *raw_key = NULL;
 	int res;

 	if (inode->i_crypt_info)
 		return 0;

 	res = fscrypt_initialize(inode->i_sb->s_cop->flags);
 	if (res)
 		return res;

 	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
 	if (res < 0) {
 		if (!fscrypt_dummy_context_enabled(inode) ||
 		    inode->i_sb->s_cop->is_encrypted(inode))
 			return res;
 		/* Fake up a context for an unencrypted directory */
 		memset(&ctx, 0, sizeof(ctx));
 		ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
 		ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
 		ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
 		memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
 	} else if (res != sizeof(ctx)) {
 		return -EINVAL;
 	}

 	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
 		return -EINVAL;

 	if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
 		return -EINVAL;

 	crypt_info = kmem_cache_alloc(fscrypt_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;
 	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
 				sizeof(crypt_info->ci_master_key));

 	res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize);
 	if (res)
 		goto out;

 	/*
 	 * This cannot be a stack buffer because it is passed to the scatterlist
 	 * crypto API as part of key derivation.
 	 */
 	res = -ENOMEM;
 	raw_key = kmalloc(FS_MAX_KEY_SIZE, GFP_NOFS);
 	if (!raw_key)
 		goto out;

 	res = validate_user_key(crypt_info, &ctx, raw_key, FS_KEY_DESC_PREFIX);
 	if (res && inode->i_sb->s_cop->key_prefix) {
 		int res2 = validate_user_key(crypt_info, &ctx, raw_key,
 					     inode->i_sb->s_cop->key_prefix);
 		if (res2) {
 			if (res2 == -ENOKEY)
 				res = -ENOKEY;
 			goto out;
 		}
 	} else if (res) {
 		goto out;
 	}
 	ctfm = crypto_alloc_skcipher(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\n",
 		       __func__, res, (unsigned) inode->i_ino);
 		goto out;
 	}
 	crypt_info->ci_ctfm = ctfm;
 	crypto_skcipher_clear_flags(ctfm, ~0);
 	crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
 	res = crypto_skcipher_setkey(ctfm, raw_key, keysize);
 	if (res)
 		goto out;

 	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
 		crypt_info = NULL;
 out:
 	if (res == -ENOKEY)
 		res = 0;
 	put_crypt_info(crypt_info);
 	kzfree(raw_key);
 	return res;
 }
 EXPORT_SYMBOL(fscrypt_get_encryption_info);

 void fscrypt_put_encryption_info(struct inode *inode, struct fscrypt_info *ci)
 {
 	struct fscrypt_info *prev;

 	if (ci == NULL)
 		ci = ACCESS_ONCE(inode->i_crypt_info);
 	if (ci == NULL)
 		return;

 	prev = cmpxchg(&inode->i_crypt_info, ci, NULL);
 	if (prev != ci)
 		return;

 	put_crypt_info(ci);
 }
 EXPORT_SYMBOL(fscrypt_put_encryption_info);
	/*
	* key management facility for FS encryption support.
	*
	* Copyright (C) 2015, Google, Inc.
	*
	* This contains encryption key functions.
	*
	* Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
	*/

	#include <keys/user-type.h>
	#include <linux/scatterlist.h>
	#include "fscrypt_private.h"

	static void derive_crypt_complete(struct crypto_async_request *req, int rc)
	{
	struct fscrypt_completion_result *ecr = req->data;

	if (rc == -EINPROGRESS)
	return;

	ecr->res = rc;
	complete(&ecr->completion);
	}

	/**
	* derive_key_aes() - Derive a key using AES-128-ECB
	* @deriving_key: Encryption key used for derivation.
	* @source_key: Source key to which to apply derivation.
	* @derived_key: Derived key.
	*
	* Return: Zero on success; non-zero otherwise.
	*/
	static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE],
	u8 source_key[FS_AES_256_XTS_KEY_SIZE],
	u8 derived_key[FS_AES_256_XTS_KEY_SIZE])
	{
	int res = 0;
	struct skcipher_request *req = NULL;
	DECLARE_FS_COMPLETION_RESULT(ecr);
	struct scatterlist src_sg, dst_sg;
	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);

	if (IS_ERR(tfm)) {
	res = PTR_ERR(tfm);
	tfm = NULL;
	goto out;
	}
	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
	req = skcipher_request_alloc(tfm, GFP_NOFS);
	if (!req) {
	res = -ENOMEM;
	goto out;
	}
	skcipher_request_set_callback(req,
	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	derive_crypt_complete, &ecr);
	res = crypto_skcipher_setkey(tfm, deriving_key,
	FS_AES_128_ECB_KEY_SIZE);
	if (res < 0)
	goto out;

	sg_init_one(&src_sg, source_key, FS_AES_256_XTS_KEY_SIZE);
	sg_init_one(&dst_sg, derived_key, FS_AES_256_XTS_KEY_SIZE);
	skcipher_request_set_crypt(req, &src_sg, &dst_sg,
	FS_AES_256_XTS_KEY_SIZE, NULL);
	res = crypto_skcipher_encrypt(req);
	if (res == -EINPROGRESS \|\| res == -EBUSY) {
	wait_for_completion(&ecr.completion);
	res = ecr.res;
	}
	out:
	skcipher_request_free(req);
	crypto_free_skcipher(tfm);
	return res;
	}

	static int validate_user_key(struct fscrypt_info *crypt_info,
	struct fscrypt_context ctx, u8 raw_key,
	const char *prefix)
	{
	char *description;
	struct key *keyring_key;
	struct fscrypt_key *master_key;
	const struct user_key_payload *ukp;
	int res;

	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
	FS_KEY_DESCRIPTOR_SIZE,
	ctx->master_key_descriptor);
	if (!description)
	return -ENOMEM;

	keyring_key = request_key(&key_type_logon, description, NULL);
	kfree(description);
	if (IS_ERR(keyring_key))
	return PTR_ERR(keyring_key);
	down_read(&keyring_key->sem);

	if (keyring_key->type != &key_type_logon) {
	printk_once(KERN_WARNING
	"%s: key type must be logon\n", __func__);
	res = -ENOKEY;
	goto out;
	}
	ukp = user_key_payload_locked(keyring_key);
	if (ukp->datalen != sizeof(struct fscrypt_key)) {
	res = -EINVAL;
	goto out;
	}
	master_key = (struct fscrypt_key *)ukp->data;
	BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE);

	if (master_key->size != FS_AES_256_XTS_KEY_SIZE) {
	printk_once(KERN_WARNING
	"%s: key size incorrect: %d\n",
	__func__, master_key->size);
	res = -ENOKEY;
	goto out;
	}
	res = derive_key_aes(ctx->nonce, master_key->raw, raw_key);
	out:
	up_read(&keyring_key->sem);
	key_put(keyring_key);
	return res;
	}

	static int determine_cipher_type(struct fscrypt_info ci, struct inode inode,
	const char *cipher_str_ret, int keysize_ret)
	{
	if (S_ISREG(inode->i_mode)) {
	if (ci->ci_data_mode == FS_ENCRYPTION_MODE_AES_256_XTS) {
	*cipher_str_ret = "xts(aes)";
	*keysize_ret = FS_AES_256_XTS_KEY_SIZE;
	return 0;
	}
	pr_warn_once("fscrypto: unsupported contents encryption mode "
	"%d for inode %lu\n",
	ci->ci_data_mode, inode->i_ino);
	return -ENOKEY;
	}

	if (S_ISDIR(inode->i_mode) \|\| S_ISLNK(inode->i_mode)) {
	if (ci->ci_filename_mode == FS_ENCRYPTION_MODE_AES_256_CTS) {
	*cipher_str_ret = "cts(cbc(aes))";
	*keysize_ret = FS_AES_256_CTS_KEY_SIZE;
	return 0;
	}
	pr_warn_once("fscrypto: unsupported filenames encryption mode "
	"%d for inode %lu\n",
	ci->ci_filename_mode, inode->i_ino);
	return -ENOKEY;
	}

	pr_warn_once("fscrypto: unsupported file type %d for inode %lu\n",
	(inode->i_mode & S_IFMT), inode->i_ino);
	return -ENOKEY;
	}

	static void put_crypt_info(struct fscrypt_info *ci)
	{
	if (!ci)
	return;

	crypto_free_skcipher(ci->ci_ctfm);
	kmem_cache_free(fscrypt_info_cachep, ci);
	}

	int fscrypt_get_encryption_info(struct inode *inode)
	{
	struct fscrypt_info *crypt_info;
	struct fscrypt_context ctx;
	struct crypto_skcipher *ctfm;
	const char *cipher_str;
	int keysize;
	u8 *raw_key = NULL;
	int res;

	if (inode->i_crypt_info)
	return 0;

	res = fscrypt_initialize(inode->i_sb->s_cop->flags);
	if (res)
	return res;

	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
	if (res < 0) {
	if (!fscrypt_dummy_context_enabled(inode) \|\|
	inode->i_sb->s_cop->is_encrypted(inode))
	return res;
	/* Fake up a context for an unencrypted directory */
	memset(&ctx, 0, sizeof(ctx));
	ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
	ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
	ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
	memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
	} else if (res != sizeof(ctx)) {
	return -EINVAL;
	}

	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
	return -EINVAL;

	if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
	return -EINVAL;

	crypt_info = kmem_cache_alloc(fscrypt_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;
	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
	sizeof(crypt_info->ci_master_key));

	res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize);
	if (res)
	goto out;

	/*
	* This cannot be a stack buffer because it is passed to the scatterlist
	* crypto API as part of key derivation.
	*/
	res = -ENOMEM;
	raw_key = kmalloc(FS_MAX_KEY_SIZE, GFP_NOFS);
	if (!raw_key)
	goto out;

	res = validate_user_key(crypt_info, &ctx, raw_key, FS_KEY_DESC_PREFIX);
	if (res && inode->i_sb->s_cop->key_prefix) {
	int res2 = validate_user_key(crypt_info, &ctx, raw_key,
	inode->i_sb->s_cop->key_prefix);
	if (res2) {
	if (res2 == -ENOKEY)
	res = -ENOKEY;
	goto out;
	}
	} else if (res) {
	goto out;
	}
	ctfm = crypto_alloc_skcipher(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\n",
	__func__, res, (unsigned) inode->i_ino);
	goto out;
	}
	crypt_info->ci_ctfm = ctfm;
	crypto_skcipher_clear_flags(ctfm, ~0);
	crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
	res = crypto_skcipher_setkey(ctfm, raw_key, keysize);
	if (res)
	goto out;

	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
	crypt_info = NULL;
	out:
	if (res == -ENOKEY)
	res = 0;
	put_crypt_info(crypt_info);
	kzfree(raw_key);
	return res;
	}
	EXPORT_SYMBOL(fscrypt_get_encryption_info);

	void fscrypt_put_encryption_info(struct inode inode, struct fscrypt_info ci)
	{
	struct fscrypt_info *prev;

	if (ci == NULL)
	ci = ACCESS_ONCE(inode->i_crypt_info);
	if (ci == NULL)
	return;

	prev = cmpxchg(&inode->i_crypt_info, ci, NULL);
	if (prev != ci)
	return;

	put_crypt_info(ci);
	}
	EXPORT_SYMBOL(fscrypt_put_encryption_info);