fs/crypto/keyinfo.c - kernel/msm-4.19 - Gitiles

 /*
  * 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 <linux/fscrypto.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,
 			u8 *prefix, int prefix_size)
 {
 	u8 *full_key_descriptor;
 	struct key *keyring_key;
 	struct fscrypt_key *master_key;
 	const struct user_key_payload *ukp;
 	int full_key_len = prefix_size + (FS_KEY_DESCRIPTOR_SIZE * 2) + 1;
 	int res;

 	full_key_descriptor = kmalloc(full_key_len, GFP_NOFS);
 	if (!full_key_descriptor)
 		return -ENOMEM;

 	memcpy(full_key_descriptor, prefix, prefix_size);
 	sprintf(full_key_descriptor + prefix_size,
 			"%*phN", FS_KEY_DESCRIPTOR_SIZE,
 			ctx->master_key_descriptor);
 	full_key_descriptor[full_key_len - 1] = '\0';
 	keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
 	kfree(full_key_descriptor);
 	if (IS_ERR(keyring_key))
 		return PTR_ERR(keyring_key);

 	if (keyring_key->type != &key_type_logon) {
 		printk_once(KERN_WARNING
 				"%s: key type must be logon\n", __func__);
 		res = -ENOKEY;
 		goto out;
 	}
 	down_read(&keyring_key->sem);
 	ukp = user_key_payload(keyring_key);
 	if (ukp->datalen != sizeof(struct fscrypt_key)) {
 		res = -EINVAL;
 		up_read(&keyring_key->sem);
 		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;
 		up_read(&keyring_key->sem);
 		goto out;
 	}
 	res = derive_key_aes(ctx->nonce, master_key->raw, raw_key);
 	up_read(&keyring_key->sem);
 	if (res)
 		goto out;

 	crypt_info->ci_keyring_key = keyring_key;
 	return 0;
 out:
 	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;

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

 int get_crypt_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[FS_MAX_KEY_SIZE];
 	int res;

 	res = fscrypt_initialize();
 	if (res)
 		return res;

 	if (!inode->i_sb->s_cop->get_context)
 		return -EOPNOTSUPP;
 retry:
 	crypt_info = ACCESS_ONCE(inode->i_crypt_info);
 	if (crypt_info) {
 		if (!crypt_info->ci_keyring_key ||
 				key_validate(crypt_info->ci_keyring_key) == 0)
 			return 0;
 		fscrypt_put_encryption_info(inode, crypt_info);
 		goto retry;
 	}

 	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
 	if (res < 0) {
 		if (!fscrypt_dummy_context_enabled(inode))
 			return res;
 		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;
 		ctx.flags = 0;
 	} 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;
 	crypt_info->ci_keyring_key = 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;

 	if (fscrypt_dummy_context_enabled(inode)) {
 		memset(raw_key, 0x42, FS_AES_256_XTS_KEY_SIZE);
 		goto got_key;
 	}

 	res = validate_user_key(crypt_info, &ctx, raw_key,
 			FS_KEY_DESC_PREFIX, FS_KEY_DESC_PREFIX_SIZE);
 	if (res && inode->i_sb->s_cop->key_prefix) {
 		u8 *prefix = NULL;
 		int prefix_size, res2;

 		prefix_size = inode->i_sb->s_cop->key_prefix(inode, &prefix);
 		res2 = validate_user_key(crypt_info, &ctx, raw_key,
 							prefix, prefix_size);
 		if (res2) {
 			if (res2 == -ENOKEY)
 				res = -ENOKEY;
 			goto out;
 		}
 	} else if (res) {
 		goto out;
 	}
 got_key:
 	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;

 	memzero_explicit(raw_key, sizeof(raw_key));
 	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) != NULL) {
 		put_crypt_info(crypt_info);
 		goto retry;
 	}
 	return 0;

 out:
 	if (res == -ENOKEY)
 		res = 0;
 	put_crypt_info(crypt_info);
 	memzero_explicit(raw_key, sizeof(raw_key));
 	return res;
 }

 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);

 int fscrypt_get_encryption_info(struct inode *inode)
 {
 	struct fscrypt_info *ci = inode->i_crypt_info;

 	if (!ci ||
 		(ci->ci_keyring_key &&
 		 (ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) |
 					       (1 << KEY_FLAG_REVOKED) |
 					       (1 << KEY_FLAG_DEAD)))))
 		return get_crypt_info(inode);
 	return 0;
 }
 EXPORT_SYMBOL(fscrypt_get_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 <linux/fscrypto.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,
	u8 *prefix, int prefix_size)
	{
	u8 *full_key_descriptor;
	struct key *keyring_key;
	struct fscrypt_key *master_key;
	const struct user_key_payload *ukp;
	int full_key_len = prefix_size + (FS_KEY_DESCRIPTOR_SIZE * 2) + 1;
	int res;

	full_key_descriptor = kmalloc(full_key_len, GFP_NOFS);
	if (!full_key_descriptor)
	return -ENOMEM;

	memcpy(full_key_descriptor, prefix, prefix_size);
	sprintf(full_key_descriptor + prefix_size,
	"%*phN", FS_KEY_DESCRIPTOR_SIZE,
	ctx->master_key_descriptor);
	full_key_descriptor[full_key_len - 1] = '\0';
	keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
	kfree(full_key_descriptor);
	if (IS_ERR(keyring_key))
	return PTR_ERR(keyring_key);

	if (keyring_key->type != &key_type_logon) {
	printk_once(KERN_WARNING
	"%s: key type must be logon\n", __func__);
	res = -ENOKEY;
	goto out;
	}
	down_read(&keyring_key->sem);
	ukp = user_key_payload(keyring_key);
	if (ukp->datalen != sizeof(struct fscrypt_key)) {
	res = -EINVAL;
	up_read(&keyring_key->sem);
	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;
	up_read(&keyring_key->sem);
	goto out;
	}
	res = derive_key_aes(ctx->nonce, master_key->raw, raw_key);
	up_read(&keyring_key->sem);
	if (res)
	goto out;

	crypt_info->ci_keyring_key = keyring_key;
	return 0;
	out:
	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;

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

	int get_crypt_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[FS_MAX_KEY_SIZE];
	int res;

	res = fscrypt_initialize();
	if (res)
	return res;

	if (!inode->i_sb->s_cop->get_context)
	return -EOPNOTSUPP;
	retry:
	crypt_info = ACCESS_ONCE(inode->i_crypt_info);
	if (crypt_info) {
	if (!crypt_info->ci_keyring_key \|\|
	key_validate(crypt_info->ci_keyring_key) == 0)
	return 0;
	fscrypt_put_encryption_info(inode, crypt_info);
	goto retry;
	}

	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
	if (res < 0) {
	if (!fscrypt_dummy_context_enabled(inode))
	return res;
	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;
	ctx.flags = 0;
	} 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;
	crypt_info->ci_keyring_key = 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;

	if (fscrypt_dummy_context_enabled(inode)) {
	memset(raw_key, 0x42, FS_AES_256_XTS_KEY_SIZE);
	goto got_key;
	}

	res = validate_user_key(crypt_info, &ctx, raw_key,
	FS_KEY_DESC_PREFIX, FS_KEY_DESC_PREFIX_SIZE);
	if (res && inode->i_sb->s_cop->key_prefix) {
	u8 *prefix = NULL;
	int prefix_size, res2;

	prefix_size = inode->i_sb->s_cop->key_prefix(inode, &prefix);
	res2 = validate_user_key(crypt_info, &ctx, raw_key,
	prefix, prefix_size);
	if (res2) {
	if (res2 == -ENOKEY)
	res = -ENOKEY;
	goto out;
	}
	} else if (res) {
	goto out;
	}
	got_key:
	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;

	memzero_explicit(raw_key, sizeof(raw_key));
	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) != NULL) {
	put_crypt_info(crypt_info);
	goto retry;
	}
	return 0;

	out:
	if (res == -ENOKEY)
	res = 0;
	put_crypt_info(crypt_info);
	memzero_explicit(raw_key, sizeof(raw_key));
	return res;
	}

	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);

	int fscrypt_get_encryption_info(struct inode *inode)
	{
	struct fscrypt_info *ci = inode->i_crypt_info;

	if (!ci \|\|
	(ci->ci_keyring_key &&
	(ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) \|
	(1 << KEY_FLAG_REVOKED) \|
	(1 << KEY_FLAG_DEAD)))))
	return get_crypt_info(inode);
	return 0;
	}
	EXPORT_SYMBOL(fscrypt_get_encryption_info);