[linux.git] / fs / crypto / hooks.c

/*
 * fs/crypto/hooks.c
 *
 * Encryption hooks for higher-level filesystem operations.
 */

#include <linux/ratelimit.h>
#include "fscrypt_private.h"

/**
 * fscrypt_file_open - prepare to open a possibly-encrypted regular file
 * @inode: the inode being opened
 * @filp: the struct file being set up
 *
 * Currently, an encrypted regular file can only be opened if its encryption key
 * is available; access to the raw encrypted contents is not supported.
 * Therefore, we first set up the inode's encryption key (if not already done)
 * and return an error if it's unavailable.
 *
 * We also verify that if the parent directory (from the path via which the file
 * is being opened) is encrypted, then the inode being opened uses the same
 * encryption policy.  This is needed as part of the enforcement that all files
 * in an encrypted directory tree use the same encryption policy, as a
 * protection against certain types of offline attacks.  Note that this check is
 * needed even when opening an *unencrypted* file, since it's forbidden to have
 * an unencrypted file in an encrypted directory.
 *
 * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
 */
int fscrypt_file_open(struct inode *inode, struct file *filp)
{
	int err;
	struct dentry *dir;

	err = fscrypt_require_key(inode);
	if (err)
		return err;

	dir = dget_parent(file_dentry(filp));
	if (IS_ENCRYPTED(d_inode(dir)) &&
	    !fscrypt_has_permitted_context(d_inode(dir), inode)) {
		fscrypt_warn(inode->i_sb,
			     "inconsistent encryption contexts: %lu/%lu",
			     d_inode(dir)->i_ino, inode->i_ino);
		err = -EPERM;
	}
	dput(dir);
	return err;
}
EXPORT_SYMBOL_GPL(fscrypt_file_open);

int __fscrypt_prepare_link(struct inode *inode, struct inode *dir)
{
	int err;

	err = fscrypt_require_key(dir);
	if (err)
		return err;

	if (!fscrypt_has_permitted_context(dir, inode))
		return -EPERM;

	return 0;
}
EXPORT_SYMBOL_GPL(__fscrypt_prepare_link);

int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry,
			     struct inode *new_dir, struct dentry *new_dentry,
			     unsigned int flags)
{
	int err;

	err = fscrypt_require_key(old_dir);
	if (err)
		return err;

	err = fscrypt_require_key(new_dir);
	if (err)
		return err;

	if (old_dir != new_dir) {
		if (IS_ENCRYPTED(new_dir) &&
		    !fscrypt_has_permitted_context(new_dir,
						   d_inode(old_dentry)))
			return -EPERM;

		if ((flags & RENAME_EXCHANGE) &&
		    IS_ENCRYPTED(old_dir) &&
		    !fscrypt_has_permitted_context(old_dir,
						   d_inode(new_dentry)))
			return -EPERM;
	}
	return 0;
}
EXPORT_SYMBOL_GPL(__fscrypt_prepare_rename);

int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry)
{
	int err = fscrypt_get_encryption_info(dir);

	if (err)
		return err;

	if (fscrypt_has_encryption_key(dir)) {
		spin_lock(&dentry->d_lock);
		dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY;
		spin_unlock(&dentry->d_lock);
	}

	d_set_d_op(dentry, &fscrypt_d_ops);
	return 0;
}
EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);

int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
			      unsigned int max_len,
			      struct fscrypt_str *disk_link)
{
	int err;

	/*
	 * To calculate the size of the encrypted symlink target we need to know
	 * the amount of NUL padding, which is determined by the flags set in
	 * the encryption policy which will be inherited from the directory.
	 * The easiest way to get access to this is to just load the directory's
	 * fscrypt_info, since we'll need it to create the dir_entry anyway.
	 *
	 * Note: in test_dummy_encryption mode, @dir may be unencrypted.
	 */
	err = fscrypt_get_encryption_info(dir);
	if (err)
		return err;
	if (!fscrypt_has_encryption_key(dir))
		return -ENOKEY;

	/*
	 * Calculate the size of the encrypted symlink and verify it won't
	 * exceed max_len.  Note that for historical reasons, encrypted symlink
	 * targets are prefixed with the ciphertext length, despite this
	 * actually being redundant with i_size.  This decreases by 2 bytes the
	 * longest symlink target we can accept.
	 *
	 * We could recover 1 byte by not counting a null terminator, but
	 * counting it (even though it is meaningless for ciphertext) is simpler
	 * for now since filesystems will assume it is there and subtract it.
	 */
	if (!fscrypt_fname_encrypted_size(dir, len,
					  max_len - sizeof(struct fscrypt_symlink_data),
					  &disk_link->len))
		return -ENAMETOOLONG;
	disk_link->len += sizeof(struct fscrypt_symlink_data);

	disk_link->name = NULL;
	return 0;
}
EXPORT_SYMBOL_GPL(__fscrypt_prepare_symlink);

int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
			      unsigned int len, struct fscrypt_str *disk_link)
{
	int err;
	struct qstr iname = QSTR_INIT(target, len);
	struct fscrypt_symlink_data *sd;
	unsigned int ciphertext_len;

	err = fscrypt_require_key(inode);
	if (err)
		return err;

	if (disk_link->name) {
		/* filesystem-provided buffer */
		sd = (struct fscrypt_symlink_data *)disk_link->name;
	} else {
		sd = kmalloc(disk_link->len, GFP_NOFS);
		if (!sd)
			return -ENOMEM;
	}
	ciphertext_len = disk_link->len - sizeof(*sd);
	sd->len = cpu_to_le16(ciphertext_len);

	err = fname_encrypt(inode, &iname, sd->encrypted_path, ciphertext_len);
	if (err) {
		if (!disk_link->name)
			kfree(sd);
		return err;
	}
	/*
	 * Null-terminating the ciphertext doesn't make sense, but we still
	 * count the null terminator in the length, so we might as well
	 * initialize it just in case the filesystem writes it out.
	 */
	sd->encrypted_path[ciphertext_len] = '\0';

	if (!disk_link->name)
		disk_link->name = (unsigned char *)sd;
	return 0;
}
EXPORT_SYMBOL_GPL(__fscrypt_encrypt_symlink);

/**
 * fscrypt_get_symlink - get the target of an encrypted symlink
 * @inode: the symlink inode
 * @caddr: the on-disk contents of the symlink
 * @max_size: size of @caddr buffer
 * @done: if successful, will be set up to free the returned target
 *
 * If the symlink's encryption key is available, we decrypt its target.
 * Otherwise, we encode its target for presentation.
 *
 * This may sleep, so the filesystem must have dropped out of RCU mode already.
 *
 * Return: the presentable symlink target or an ERR_PTR()
 */
const char *fscrypt_get_symlink(struct inode *inode, const void *caddr,
				unsigned int max_size,
				struct delayed_call *done)
{
	const struct fscrypt_symlink_data *sd;
	struct fscrypt_str cstr, pstr;
	int err;

	/* This is for encrypted symlinks only */
	if (WARN_ON(!IS_ENCRYPTED(inode)))
		return ERR_PTR(-EINVAL);

	/*
	 * Try to set up the symlink's encryption key, but we can continue
	 * regardless of whether the key is available or not.
	 */
	err = fscrypt_get_encryption_info(inode);
	if (err)
		return ERR_PTR(err);

	/*
	 * For historical reasons, encrypted symlink targets are prefixed with
	 * the ciphertext length, even though this is redundant with i_size.
	 */

	if (max_size < sizeof(*sd))
		return ERR_PTR(-EUCLEAN);
	sd = caddr;
	cstr.name = (unsigned char *)sd->encrypted_path;
	cstr.len = le16_to_cpu(sd->len);

	if (cstr.len == 0)
		return ERR_PTR(-EUCLEAN);

	if (cstr.len + sizeof(*sd) - 1 > max_size)
		return ERR_PTR(-EUCLEAN);

	err = fscrypt_fname_alloc_buffer(inode, cstr.len, &pstr);
	if (err)
		return ERR_PTR(err);

	err = fscrypt_fname_disk_to_usr(inode, 0, 0, &cstr, &pstr);
	if (err)
		goto err_kfree;

	err = -EUCLEAN;
	if (pstr.name[0] == '\0')
		goto err_kfree;

	pstr.name[pstr.len] = '\0';
	set_delayed_call(done, kfree_link, pstr.name);
	return pstr.name;

err_kfree:
	kfree(pstr.name);
	return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(fscrypt_get_symlink);
Commit	Line	Data
efcc7ae2 EB	1	/*
	2	* fs/crypto/hooks.c
	3	*
	4	* Encryption hooks for higher-level filesystem operations.
	5	*/
	6
	7	#include <linux/ratelimit.h>
	8	#include "fscrypt_private.h"
	9
	10	/**
	11	* fscrypt_file_open - prepare to open a possibly-encrypted regular file
	12	* @inode: the inode being opened
	13	* @filp: the struct file being set up
	14	*
	15	* Currently, an encrypted regular file can only be opened if its encryption key
	16	* is available; access to the raw encrypted contents is not supported.
	17	* Therefore, we first set up the inode's encryption key (if not already done)
	18	* and return an error if it's unavailable.
	19	*
	20	* We also verify that if the parent directory (from the path via which the file
	21	* is being opened) is encrypted, then the inode being opened uses the same
	22	* encryption policy. This is needed as part of the enforcement that all files
	23	* in an encrypted directory tree use the same encryption policy, as a
	24	* protection against certain types of offline attacks. Note that this check is
	25	* needed even when opening an unencrypted file, since it's forbidden to have
	26	* an unencrypted file in an encrypted directory.
	27	*
	28	* Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
	29	*/
	30	int fscrypt_file_open(struct inode inode, struct file filp)
	31	{
	32	int err;
	33	struct dentry *dir;
	34
	35	err = fscrypt_require_key(inode);
	36	if (err)
	37	return err;
	38
	39	dir = dget_parent(file_dentry(filp));
	40	if (IS_ENCRYPTED(d_inode(dir)) &&
	41	!fscrypt_has_permitted_context(d_inode(dir), inode)) {
544d08fd EB	42	fscrypt_warn(inode->i_sb,
	43	"inconsistent encryption contexts: %lu/%lu",
	44	d_inode(dir)->i_ino, inode->i_ino);
efcc7ae2 EB	45	err = -EPERM;
	46	}
	47	dput(dir);
	48	return err;
	49	}
	50	EXPORT_SYMBOL_GPL(fscrypt_file_open);
0ea87a96 EB	51
	52	int __fscrypt_prepare_link(struct inode inode, struct inode dir)
	53	{
	54	int err;
	55
	56	err = fscrypt_require_key(dir);
	57	if (err)
	58	return err;
	59
	60	if (!fscrypt_has_permitted_context(dir, inode))
	61	return -EPERM;
	62
	63	return 0;
	64	}
	65	EXPORT_SYMBOL_GPL(__fscrypt_prepare_link);
94b26f36 EB	66
	67	int __fscrypt_prepare_rename(struct inode old_dir, struct dentry old_dentry,
	68	struct inode new_dir, struct dentry new_dentry,
	69	unsigned int flags)
	70	{
	71	int err;
	72
	73	err = fscrypt_require_key(old_dir);
	74	if (err)
	75	return err;
	76
	77	err = fscrypt_require_key(new_dir);
	78	if (err)
	79	return err;
	80
	81	if (old_dir != new_dir) {
	82	if (IS_ENCRYPTED(new_dir) &&
	83	!fscrypt_has_permitted_context(new_dir,
	84	d_inode(old_dentry)))
	85	return -EPERM;
	86
	87	if ((flags & RENAME_EXCHANGE) &&
	88	IS_ENCRYPTED(old_dir) &&
	89	!fscrypt_has_permitted_context(old_dir,
	90	d_inode(new_dentry)))
	91	return -EPERM;
	92	}
	93	return 0;
	94	}
	95	EXPORT_SYMBOL_GPL(__fscrypt_prepare_rename);
32c3cf02 EB	96
	97	int __fscrypt_prepare_lookup(struct inode dir, struct dentry dentry)
	98	{
	99	int err = fscrypt_get_encryption_info(dir);
	100
	101	if (err)
	102	return err;
	103
	104	if (fscrypt_has_encryption_key(dir)) {
	105	spin_lock(&dentry->d_lock);
	106	dentry->d_flags \|= DCACHE_ENCRYPTED_WITH_KEY;
	107	spin_unlock(&dentry->d_lock);
	108	}
	109
	110	d_set_d_op(dentry, &fscrypt_d_ops);
	111	return 0;
	112	}
	113	EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);
76e81d6d EB	114
	115	int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
	116	unsigned int max_len,
	117	struct fscrypt_str *disk_link)
	118	{
	119	int err;
	120
	121	/*
	122	* To calculate the size of the encrypted symlink target we need to know
	123	* the amount of NUL padding, which is determined by the flags set in
	124	* the encryption policy which will be inherited from the directory.
	125	* The easiest way to get access to this is to just load the directory's
	126	* fscrypt_info, since we'll need it to create the dir_entry anyway.
	127	*
	128	* Note: in test_dummy_encryption mode, @dir may be unencrypted.
	129	*/
	130	err = fscrypt_get_encryption_info(dir);
	131	if (err)
	132	return err;
	133	if (!fscrypt_has_encryption_key(dir))
	134	return -ENOKEY;
	135
	136	/*
	137	* Calculate the size of the encrypted symlink and verify it won't
	138	* exceed max_len. Note that for historical reasons, encrypted symlink
	139	* targets are prefixed with the ciphertext length, despite this
	140	* actually being redundant with i_size. This decreases by 2 bytes the
	141	* longest symlink target we can accept.
	142	*
	143	* We could recover 1 byte by not counting a null terminator, but
	144	* counting it (even though it is meaningless for ciphertext) is simpler
	145	* for now since filesystems will assume it is there and subtract it.
	146	*/
b9db0b4a EB	147	if (!fscrypt_fname_encrypted_size(dir, len,
	148	max_len - sizeof(struct fscrypt_symlink_data),
	149	&disk_link->len))
76e81d6d	150	return -ENAMETOOLONG;
b9db0b4a EB	151	disk_link->len += sizeof(struct fscrypt_symlink_data);
b9db0b4a EB	152
76e81d6d EB	153	disk_link->name = NULL;
	154	return 0;
	155	}
	156	EXPORT_SYMBOL_GPL(__fscrypt_prepare_symlink);
	157
	158	int __fscrypt_encrypt_symlink(struct inode inode, const char target,
	159	unsigned int len, struct fscrypt_str *disk_link)
	160	{
	161	int err;
0b1dfa4c	162	struct qstr iname = QSTR_INIT(target, len);
76e81d6d EB	163	struct fscrypt_symlink_data *sd;
76e81d6d EB	164	unsigned int ciphertext_len;
76e81d6d EB	165
	166	err = fscrypt_require_key(inode);
	167	if (err)
	168	return err;
	169
	170	if (disk_link->name) {
	171	/* filesystem-provided buffer */
	172	sd = (struct fscrypt_symlink_data *)disk_link->name;
	173	} else {
	174	sd = kmalloc(disk_link->len, GFP_NOFS);
	175	if (!sd)
	176	return -ENOMEM;
	177	}
	178	ciphertext_len = disk_link->len - sizeof(*sd);
	179	sd->len = cpu_to_le16(ciphertext_len);
	180
50c961de	181	err = fname_encrypt(inode, &iname, sd->encrypted_path, ciphertext_len);
76e81d6d EB	182	if (err) {
	183	if (!disk_link->name)
	184	kfree(sd);
	185	return err;
	186	}
76e81d6d EB	187	/*
	188	* Null-terminating the ciphertext doesn't make sense, but we still
	189	* count the null terminator in the length, so we might as well
	190	* initialize it just in case the filesystem writes it out.
	191	*/
	192	sd->encrypted_path[ciphertext_len] = '\0';
	193
	194	if (!disk_link->name)
	195	disk_link->name = (unsigned char *)sd;
	196	return 0;
	197	}
	198	EXPORT_SYMBOL_GPL(__fscrypt_encrypt_symlink);
3b0d8837 EB	199
	200	/**
	201	* fscrypt_get_symlink - get the target of an encrypted symlink
	202	* @inode: the symlink inode
	203	* @caddr: the on-disk contents of the symlink
	204	* @max_size: size of @caddr buffer
	205	* @done: if successful, will be set up to free the returned target
	206	*
	207	* If the symlink's encryption key is available, we decrypt its target.
	208	* Otherwise, we encode its target for presentation.
	209	*
	210	* This may sleep, so the filesystem must have dropped out of RCU mode already.
	211	*
	212	* Return: the presentable symlink target or an ERR_PTR()
	213	*/
	214	const char fscrypt_get_symlink(struct inode inode, const void *caddr,
	215	unsigned int max_size,
	216	struct delayed_call *done)
	217	{
	218	const struct fscrypt_symlink_data *sd;
	219	struct fscrypt_str cstr, pstr;
	220	int err;
	221
	222	/* This is for encrypted symlinks only */
	223	if (WARN_ON(!IS_ENCRYPTED(inode)))
	224	return ERR_PTR(-EINVAL);
	225
	226	/*
	227	* Try to set up the symlink's encryption key, but we can continue
	228	* regardless of whether the key is available or not.
	229	*/
	230	err = fscrypt_get_encryption_info(inode);
	231	if (err)
	232	return ERR_PTR(err);
	233
	234	/*
	235	* For historical reasons, encrypted symlink targets are prefixed with
	236	* the ciphertext length, even though this is redundant with i_size.
	237	*/
	238
	239	if (max_size < sizeof(*sd))
	240	return ERR_PTR(-EUCLEAN);
	241	sd = caddr;
	242	cstr.name = (unsigned char *)sd->encrypted_path;
	243	cstr.len = le16_to_cpu(sd->len);
	244
	245	if (cstr.len == 0)
	246	return ERR_PTR(-EUCLEAN);
	247
	248	if (cstr.len + sizeof(*sd) - 1 > max_size)
	249	return ERR_PTR(-EUCLEAN);
	250
	251	err = fscrypt_fname_alloc_buffer(inode, cstr.len, &pstr);
	252	if (err)
	253	return ERR_PTR(err);
	254
	255	err = fscrypt_fname_disk_to_usr(inode, 0, 0, &cstr, &pstr);
	256	if (err)
	257	goto err_kfree;
	258
	259	err = -EUCLEAN;
	260	if (pstr.name[0] == '\0')
	261	goto err_kfree;
	262
263	pstr.name[pstr.len] = '\0';
264	set_delayed_call(done, kfree_link, pstr.name);
265	return pstr.name;
266
267	err_kfree:
268	kfree(pstr.name);
269	return ERR_PTR(err);
270	}
271	EXPORT_SYMBOL_GPL(fscrypt_get_symlink);