611 lines
19 KiB
C
611 lines
19 KiB
C
|
// SPDX-License-Identifier: GPL-2.0
|
||
|
/*
|
||
|
* This contains functions for filename crypto management
|
||
|
*
|
||
|
* Copyright (C) 2015, Google, Inc.
|
||
|
* Copyright (C) 2015, Motorola Mobility
|
||
|
*
|
||
|
* Written by Uday Savagaonkar, 2014.
|
||
|
* Modified by Jaegeuk Kim, 2015.
|
||
|
*
|
||
|
* This has not yet undergone a rigorous security audit.
|
||
|
*/
|
||
|
|
||
|
#include <linux/namei.h>
|
||
|
#include <linux/scatterlist.h>
|
||
|
#include <crypto/hash.h>
|
||
|
#include <crypto/sha.h>
|
||
|
#include <crypto/skcipher.h>
|
||
|
#include "fscrypt_private.h"
|
||
|
|
||
|
/*
|
||
|
* struct fscrypt_nokey_name - identifier for directory entry when key is absent
|
||
|
*
|
||
|
* When userspace lists an encrypted directory without access to the key, the
|
||
|
* filesystem must present a unique "no-key name" for each filename that allows
|
||
|
* it to find the directory entry again if requested. Naively, that would just
|
||
|
* mean using the ciphertext filenames. However, since the ciphertext filenames
|
||
|
* can contain illegal characters ('\0' and '/'), they must be encoded in some
|
||
|
* way. We use base64. But that can cause names to exceed NAME_MAX (255
|
||
|
* bytes), so we also need to use a strong hash to abbreviate long names.
|
||
|
*
|
||
|
* The filesystem may also need another kind of hash, the "dirhash", to quickly
|
||
|
* find the directory entry. Since filesystems normally compute the dirhash
|
||
|
* over the on-disk filename (i.e. the ciphertext), it's not computable from
|
||
|
* no-key names that abbreviate the ciphertext using the strong hash to fit in
|
||
|
* NAME_MAX. It's also not computable if it's a keyed hash taken over the
|
||
|
* plaintext (but it may still be available in the on-disk directory entry);
|
||
|
* casefolded directories use this type of dirhash. At least in these cases,
|
||
|
* each no-key name must include the name's dirhash too.
|
||
|
*
|
||
|
* To meet all these requirements, we base64-encode the following
|
||
|
* variable-length structure. It contains the dirhash, or 0's if the filesystem
|
||
|
* didn't provide one; up to 149 bytes of the ciphertext name; and for
|
||
|
* ciphertexts longer than 149 bytes, also the SHA-256 of the remaining bytes.
|
||
|
*
|
||
|
* This ensures that each no-key name contains everything needed to find the
|
||
|
* directory entry again, contains only legal characters, doesn't exceed
|
||
|
* NAME_MAX, is unambiguous unless there's a SHA-256 collision, and that we only
|
||
|
* take the performance hit of SHA-256 on very long filenames (which are rare).
|
||
|
*/
|
||
|
struct fscrypt_nokey_name {
|
||
|
u32 dirhash[2];
|
||
|
u8 bytes[149];
|
||
|
u8 sha256[SHA256_DIGEST_SIZE];
|
||
|
}; /* 189 bytes => 252 bytes base64-encoded, which is <= NAME_MAX (255) */
|
||
|
|
||
|
/*
|
||
|
* Decoded size of max-size nokey name, i.e. a name that was abbreviated using
|
||
|
* the strong hash and thus includes the 'sha256' field. This isn't simply
|
||
|
* sizeof(struct fscrypt_nokey_name), as the padding at the end isn't included.
|
||
|
*/
|
||
|
#define FSCRYPT_NOKEY_NAME_MAX offsetofend(struct fscrypt_nokey_name, sha256)
|
||
|
|
||
|
static struct crypto_shash *sha256_hash_tfm;
|
||
|
|
||
|
static int fscrypt_do_sha256(const u8 *data, unsigned int data_len, u8 *result)
|
||
|
{
|
||
|
struct crypto_shash *tfm = READ_ONCE(sha256_hash_tfm);
|
||
|
|
||
|
if (unlikely(!tfm)) {
|
||
|
struct crypto_shash *prev_tfm;
|
||
|
|
||
|
tfm = crypto_alloc_shash("sha256", 0, 0);
|
||
|
if (IS_ERR(tfm)) {
|
||
|
fscrypt_err(NULL,
|
||
|
"Error allocating SHA-256 transform: %ld",
|
||
|
PTR_ERR(tfm));
|
||
|
return PTR_ERR(tfm);
|
||
|
}
|
||
|
prev_tfm = cmpxchg(&sha256_hash_tfm, NULL, tfm);
|
||
|
if (prev_tfm) {
|
||
|
crypto_free_shash(tfm);
|
||
|
tfm = prev_tfm;
|
||
|
}
|
||
|
}
|
||
|
{
|
||
|
SHASH_DESC_ON_STACK(desc, tfm);
|
||
|
|
||
|
desc->tfm = tfm;
|
||
|
desc->flags = 0;
|
||
|
|
||
|
return crypto_shash_digest(desc, data, data_len, result);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
|
||
|
{
|
||
|
if (str->len == 1 && str->name[0] == '.')
|
||
|
return true;
|
||
|
|
||
|
if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
|
||
|
return true;
|
||
|
|
||
|
return false;
|
||
|
}
|
||
|
|
||
|
/**
|
||
|
* fscrypt_fname_encrypt() - encrypt a filename
|
||
|
* @inode: inode of the parent directory (for regular filenames)
|
||
|
* or of the symlink (for symlink targets)
|
||
|
* @iname: the filename to encrypt
|
||
|
* @out: (output) the encrypted filename
|
||
|
* @olen: size of the encrypted filename. It must be at least @iname->len.
|
||
|
* Any extra space is filled with NUL padding before encryption.
|
||
|
*
|
||
|
* Return: 0 on success, -errno on failure
|
||
|
*/
|
||
|
int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
|
||
|
u8 *out, unsigned int olen)
|
||
|
{
|
||
|
struct skcipher_request *req = NULL;
|
||
|
DECLARE_CRYPTO_WAIT(wait);
|
||
|
const struct fscrypt_info *ci = inode->i_crypt_info;
|
||
|
struct crypto_skcipher *tfm = ci->ci_key.tfm;
|
||
|
union fscrypt_iv iv;
|
||
|
struct scatterlist sg;
|
||
|
int res;
|
||
|
|
||
|
/*
|
||
|
* Copy the filename to the output buffer for encrypting in-place and
|
||
|
* pad it with the needed number of NUL bytes.
|
||
|
*/
|
||
|
if (WARN_ON(olen < iname->len))
|
||
|
return -ENOBUFS;
|
||
|
memcpy(out, iname->name, iname->len);
|
||
|
memset(out + iname->len, 0, olen - iname->len);
|
||
|
|
||
|
/* Initialize the IV */
|
||
|
fscrypt_generate_iv(&iv, 0, ci);
|
||
|
|
||
|
/* Set up the encryption request */
|
||
|
req = skcipher_request_alloc(tfm, GFP_NOFS);
|
||
|
if (!req)
|
||
|
return -ENOMEM;
|
||
|
skcipher_request_set_callback(req,
|
||
|
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
|
||
|
crypto_req_done, &wait);
|
||
|
sg_init_one(&sg, out, olen);
|
||
|
skcipher_request_set_crypt(req, &sg, &sg, olen, &iv);
|
||
|
|
||
|
/* Do the encryption */
|
||
|
res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
|
||
|
skcipher_request_free(req);
|
||
|
if (res < 0) {
|
||
|
fscrypt_err(inode, "Filename encryption failed: %d", res);
|
||
|
return res;
|
||
|
}
|
||
|
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
/**
|
||
|
* fname_decrypt() - decrypt a filename
|
||
|
* @inode: inode of the parent directory (for regular filenames)
|
||
|
* or of the symlink (for symlink targets)
|
||
|
* @iname: the encrypted filename to decrypt
|
||
|
* @oname: (output) the decrypted filename. The caller must have allocated
|
||
|
* enough space for this, e.g. using fscrypt_fname_alloc_buffer().
|
||
|
*
|
||
|
* Return: 0 on success, -errno on failure
|
||
|
*/
|
||
|
static int fname_decrypt(const struct inode *inode,
|
||
|
const struct fscrypt_str *iname,
|
||
|
struct fscrypt_str *oname)
|
||
|
{
|
||
|
struct skcipher_request *req = NULL;
|
||
|
DECLARE_CRYPTO_WAIT(wait);
|
||
|
struct scatterlist src_sg, dst_sg;
|
||
|
const struct fscrypt_info *ci = inode->i_crypt_info;
|
||
|
struct crypto_skcipher *tfm = ci->ci_key.tfm;
|
||
|
union fscrypt_iv iv;
|
||
|
int res;
|
||
|
|
||
|
/* Allocate request */
|
||
|
req = skcipher_request_alloc(tfm, GFP_NOFS);
|
||
|
if (!req)
|
||
|
return -ENOMEM;
|
||
|
skcipher_request_set_callback(req,
|
||
|
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
|
||
|
crypto_req_done, &wait);
|
||
|
|
||
|
/* Initialize IV */
|
||
|
fscrypt_generate_iv(&iv, 0, ci);
|
||
|
|
||
|
/* Create decryption request */
|
||
|
sg_init_one(&src_sg, iname->name, iname->len);
|
||
|
sg_init_one(&dst_sg, oname->name, oname->len);
|
||
|
skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, &iv);
|
||
|
res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
|
||
|
skcipher_request_free(req);
|
||
|
if (res < 0) {
|
||
|
fscrypt_err(inode, "Filename decryption failed: %d", res);
|
||
|
return res;
|
||
|
}
|
||
|
|
||
|
oname->len = strnlen(oname->name, iname->len);
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
static const char lookup_table[65] =
|
||
|
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
|
||
|
|
||
|
#define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
|
||
|
|
||
|
/**
|
||
|
* base64_encode() - base64-encode some bytes
|
||
|
* @src: the bytes to encode
|
||
|
* @len: number of bytes to encode
|
||
|
* @dst: (output) the base64-encoded string. Not NUL-terminated.
|
||
|
*
|
||
|
* Encodes the input string using characters from the set [A-Za-z0-9+,].
|
||
|
* The encoded string is roughly 4/3 times the size of the input string.
|
||
|
*
|
||
|
* Return: length of the encoded string
|
||
|
*/
|
||
|
static int base64_encode(const u8 *src, int len, char *dst)
|
||
|
{
|
||
|
int i, bits = 0, ac = 0;
|
||
|
char *cp = dst;
|
||
|
|
||
|
for (i = 0; i < len; i++) {
|
||
|
ac += src[i] << bits;
|
||
|
bits += 8;
|
||
|
do {
|
||
|
*cp++ = lookup_table[ac & 0x3f];
|
||
|
ac >>= 6;
|
||
|
bits -= 6;
|
||
|
} while (bits >= 6);
|
||
|
}
|
||
|
if (bits)
|
||
|
*cp++ = lookup_table[ac & 0x3f];
|
||
|
return cp - dst;
|
||
|
}
|
||
|
|
||
|
static int base64_decode(const char *src, int len, u8 *dst)
|
||
|
{
|
||
|
int i, bits = 0, ac = 0;
|
||
|
const char *p;
|
||
|
u8 *cp = dst;
|
||
|
|
||
|
for (i = 0; i < len; i++) {
|
||
|
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;
|
||
|
}
|
||
|
}
|
||
|
if (ac)
|
||
|
return -1;
|
||
|
return cp - dst;
|
||
|
}
|
||
|
|
||
|
bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
|
||
|
u32 max_len, u32 *encrypted_len_ret)
|
||
|
{
|
||
|
const struct fscrypt_info *ci = inode->i_crypt_info;
|
||
|
int padding = 4 << (fscrypt_policy_flags(&ci->ci_policy) &
|
||
|
FSCRYPT_POLICY_FLAGS_PAD_MASK);
|
||
|
u32 encrypted_len;
|
||
|
|
||
|
if (orig_len > max_len)
|
||
|
return false;
|
||
|
encrypted_len = max(orig_len, (u32)FS_CRYPTO_BLOCK_SIZE);
|
||
|
encrypted_len = round_up(encrypted_len, padding);
|
||
|
*encrypted_len_ret = min(encrypted_len, max_len);
|
||
|
return true;
|
||
|
}
|
||
|
|
||
|
/**
|
||
|
* fscrypt_fname_alloc_buffer() - allocate a buffer for presented filenames
|
||
|
* @inode: inode of the parent directory (for regular filenames)
|
||
|
* or of the symlink (for symlink targets)
|
||
|
* @max_encrypted_len: maximum length of encrypted filenames the buffer will be
|
||
|
* used to present
|
||
|
* @crypto_str: (output) buffer to allocate
|
||
|
*
|
||
|
* Allocate a buffer that is large enough to hold any decrypted or encoded
|
||
|
* filename (null-terminated), for the given maximum encrypted filename length.
|
||
|
*
|
||
|
* Return: 0 on success, -errno on failure
|
||
|
*/
|
||
|
int fscrypt_fname_alloc_buffer(const struct inode *inode,
|
||
|
u32 max_encrypted_len,
|
||
|
struct fscrypt_str *crypto_str)
|
||
|
{
|
||
|
const u32 max_encoded_len = BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX);
|
||
|
u32 max_presented_len;
|
||
|
|
||
|
max_presented_len = max(max_encoded_len, max_encrypted_len);
|
||
|
|
||
|
crypto_str->name = kmalloc(max_presented_len + 1, GFP_NOFS);
|
||
|
if (!crypto_str->name)
|
||
|
return -ENOMEM;
|
||
|
crypto_str->len = max_presented_len;
|
||
|
return 0;
|
||
|
}
|
||
|
EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);
|
||
|
|
||
|
/**
|
||
|
* fscrypt_fname_free_buffer() - free a buffer for presented filenames
|
||
|
* @crypto_str: the buffer to free
|
||
|
*
|
||
|
* Free a buffer that was allocated by fscrypt_fname_alloc_buffer().
|
||
|
*/
|
||
|
void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
|
||
|
{
|
||
|
if (!crypto_str)
|
||
|
return;
|
||
|
kfree(crypto_str->name);
|
||
|
crypto_str->name = NULL;
|
||
|
}
|
||
|
EXPORT_SYMBOL(fscrypt_fname_free_buffer);
|
||
|
|
||
|
/**
|
||
|
* fscrypt_fname_disk_to_usr() - convert an encrypted filename to
|
||
|
* user-presentable form
|
||
|
* @inode: inode of the parent directory (for regular filenames)
|
||
|
* or of the symlink (for symlink targets)
|
||
|
* @hash: first part of the name's dirhash, if applicable. This only needs to
|
||
|
* be provided if the filename is located in an indexed directory whose
|
||
|
* encryption key may be unavailable. Not needed for symlink targets.
|
||
|
* @minor_hash: second part of the name's dirhash, if applicable
|
||
|
* @iname: encrypted filename to convert. May also be "." or "..", which
|
||
|
* aren't actually encrypted.
|
||
|
* @oname: output buffer for the user-presentable filename. The caller must
|
||
|
* have allocated enough space for this, e.g. using
|
||
|
* fscrypt_fname_alloc_buffer().
|
||
|
*
|
||
|
* If the key is available, we'll decrypt the disk name. Otherwise, we'll
|
||
|
* encode it for presentation in fscrypt_nokey_name format.
|
||
|
* See struct fscrypt_nokey_name for details.
|
||
|
*
|
||
|
* Return: 0 on success, -errno on failure
|
||
|
*/
|
||
|
int fscrypt_fname_disk_to_usr(const struct inode *inode,
|
||
|
u32 hash, u32 minor_hash,
|
||
|
const struct fscrypt_str *iname,
|
||
|
struct fscrypt_str *oname)
|
||
|
{
|
||
|
const struct qstr qname = FSTR_TO_QSTR(iname);
|
||
|
struct fscrypt_nokey_name nokey_name;
|
||
|
u32 size; /* size of the unencoded no-key name */
|
||
|
int err;
|
||
|
|
||
|
if (fscrypt_is_dot_dotdot(&qname)) {
|
||
|
oname->name[0] = '.';
|
||
|
oname->name[iname->len - 1] = '.';
|
||
|
oname->len = iname->len;
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
if (iname->len < FS_CRYPTO_BLOCK_SIZE)
|
||
|
return -EUCLEAN;
|
||
|
|
||
|
if (fscrypt_has_encryption_key(inode))
|
||
|
return fname_decrypt(inode, iname, oname);
|
||
|
|
||
|
/*
|
||
|
* Sanity check that struct fscrypt_nokey_name doesn't have padding
|
||
|
* between fields and that its encoded size never exceeds NAME_MAX.
|
||
|
*/
|
||
|
BUILD_BUG_ON(offsetofend(struct fscrypt_nokey_name, dirhash) !=
|
||
|
offsetof(struct fscrypt_nokey_name, bytes));
|
||
|
BUILD_BUG_ON(offsetofend(struct fscrypt_nokey_name, bytes) !=
|
||
|
offsetof(struct fscrypt_nokey_name, sha256));
|
||
|
BUILD_BUG_ON(BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX) > NAME_MAX);
|
||
|
|
||
|
if (hash) {
|
||
|
nokey_name.dirhash[0] = hash;
|
||
|
nokey_name.dirhash[1] = minor_hash;
|
||
|
} else {
|
||
|
nokey_name.dirhash[0] = 0;
|
||
|
nokey_name.dirhash[1] = 0;
|
||
|
}
|
||
|
if (iname->len <= sizeof(nokey_name.bytes)) {
|
||
|
memcpy(nokey_name.bytes, iname->name, iname->len);
|
||
|
size = offsetof(struct fscrypt_nokey_name, bytes[iname->len]);
|
||
|
} else {
|
||
|
memcpy(nokey_name.bytes, iname->name, sizeof(nokey_name.bytes));
|
||
|
/* Compute strong hash of remaining part of name. */
|
||
|
err = fscrypt_do_sha256(&iname->name[sizeof(nokey_name.bytes)],
|
||
|
iname->len - sizeof(nokey_name.bytes),
|
||
|
nokey_name.sha256);
|
||
|
if (err)
|
||
|
return err;
|
||
|
size = FSCRYPT_NOKEY_NAME_MAX;
|
||
|
}
|
||
|
oname->len = base64_encode((const u8 *)&nokey_name, size, oname->name);
|
||
|
return 0;
|
||
|
}
|
||
|
EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
|
||
|
|
||
|
/**
|
||
|
* fscrypt_setup_filename() - prepare to search a possibly encrypted directory
|
||
|
* @dir: the directory that will be searched
|
||
|
* @iname: the user-provided filename being searched for
|
||
|
* @lookup: 1 if we're allowed to proceed without the key because it's
|
||
|
* ->lookup() or we're finding the dir_entry for deletion; 0 if we cannot
|
||
|
* proceed without the key because we're going to create the dir_entry.
|
||
|
* @fname: the filename information to be filled in
|
||
|
*
|
||
|
* Given a user-provided filename @iname, this function sets @fname->disk_name
|
||
|
* to the name that would be stored in the on-disk directory entry, if possible.
|
||
|
* If the directory is unencrypted this is simply @iname. Else, if we have the
|
||
|
* directory's encryption key, then @iname is the plaintext, so we encrypt it to
|
||
|
* get the disk_name.
|
||
|
*
|
||
|
* Else, for keyless @lookup operations, @iname is the presented ciphertext, so
|
||
|
* we decode it to get the fscrypt_nokey_name. Non-@lookup operations will be
|
||
|
* impossible in this case, so we fail them with ENOKEY.
|
||
|
*
|
||
|
* If successful, fscrypt_free_filename() must be called later to clean up.
|
||
|
*
|
||
|
* Return: 0 on success, -errno on failure
|
||
|
*/
|
||
|
int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
|
||
|
int lookup, struct fscrypt_name *fname)
|
||
|
{
|
||
|
struct fscrypt_nokey_name *nokey_name;
|
||
|
int ret;
|
||
|
|
||
|
memset(fname, 0, sizeof(struct fscrypt_name));
|
||
|
fname->usr_fname = iname;
|
||
|
|
||
|
if (!IS_ENCRYPTED(dir) || fscrypt_is_dot_dotdot(iname)) {
|
||
|
fname->disk_name.name = (unsigned char *)iname->name;
|
||
|
fname->disk_name.len = iname->len;
|
||
|
return 0;
|
||
|
}
|
||
|
ret = fscrypt_get_encryption_info(dir);
|
||
|
if (ret)
|
||
|
return ret;
|
||
|
|
||
|
if (fscrypt_has_encryption_key(dir)) {
|
||
|
if (!fscrypt_fname_encrypted_size(dir, iname->len,
|
||
|
dir->i_sb->s_cop->max_namelen,
|
||
|
&fname->crypto_buf.len))
|
||
|
return -ENAMETOOLONG;
|
||
|
fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,
|
||
|
GFP_NOFS);
|
||
|
if (!fname->crypto_buf.name)
|
||
|
return -ENOMEM;
|
||
|
|
||
|
ret = fscrypt_fname_encrypt(dir, iname, fname->crypto_buf.name,
|
||
|
fname->crypto_buf.len);
|
||
|
if (ret)
|
||
|
goto errout;
|
||
|
fname->disk_name.name = fname->crypto_buf.name;
|
||
|
fname->disk_name.len = fname->crypto_buf.len;
|
||
|
return 0;
|
||
|
}
|
||
|
if (!lookup)
|
||
|
return -ENOKEY;
|
||
|
fname->is_ciphertext_name = true;
|
||
|
|
||
|
/*
|
||
|
* We don't have the key and we are doing a lookup; decode the
|
||
|
* user-supplied name
|
||
|
*/
|
||
|
|
||
|
if (iname->len > BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX))
|
||
|
return -ENOENT;
|
||
|
|
||
|
fname->crypto_buf.name = kmalloc(FSCRYPT_NOKEY_NAME_MAX, GFP_KERNEL);
|
||
|
if (fname->crypto_buf.name == NULL)
|
||
|
return -ENOMEM;
|
||
|
|
||
|
ret = base64_decode(iname->name, iname->len, fname->crypto_buf.name);
|
||
|
if (ret < (int)offsetof(struct fscrypt_nokey_name, bytes[1]) ||
|
||
|
(ret > offsetof(struct fscrypt_nokey_name, sha256) &&
|
||
|
ret != FSCRYPT_NOKEY_NAME_MAX)) {
|
||
|
ret = -ENOENT;
|
||
|
goto errout;
|
||
|
}
|
||
|
fname->crypto_buf.len = ret;
|
||
|
|
||
|
nokey_name = (void *)fname->crypto_buf.name;
|
||
|
fname->hash = nokey_name->dirhash[0];
|
||
|
fname->minor_hash = nokey_name->dirhash[1];
|
||
|
if (ret != FSCRYPT_NOKEY_NAME_MAX) {
|
||
|
/* The full ciphertext filename is available. */
|
||
|
fname->disk_name.name = nokey_name->bytes;
|
||
|
fname->disk_name.len =
|
||
|
ret - offsetof(struct fscrypt_nokey_name, bytes);
|
||
|
}
|
||
|
return 0;
|
||
|
|
||
|
errout:
|
||
|
kfree(fname->crypto_buf.name);
|
||
|
return ret;
|
||
|
}
|
||
|
EXPORT_SYMBOL(fscrypt_setup_filename);
|
||
|
|
||
|
/**
|
||
|
* fscrypt_match_name() - test whether the given name matches a directory entry
|
||
|
* @fname: the name being searched for
|
||
|
* @de_name: the name from the directory entry
|
||
|
* @de_name_len: the length of @de_name in bytes
|
||
|
*
|
||
|
* Normally @fname->disk_name will be set, and in that case we simply compare
|
||
|
* that to the name stored in the directory entry. The only exception is that
|
||
|
* if we don't have the key for an encrypted directory and the name we're
|
||
|
* looking for is very long, then we won't have the full disk_name and instead
|
||
|
* we'll need to match against a fscrypt_nokey_name that includes a strong hash.
|
||
|
*
|
||
|
* Return: %true if the name matches, otherwise %false.
|
||
|
*/
|
||
|
bool fscrypt_match_name(const struct fscrypt_name *fname,
|
||
|
const u8 *de_name, u32 de_name_len)
|
||
|
{
|
||
|
const struct fscrypt_nokey_name *nokey_name =
|
||
|
(const void *)fname->crypto_buf.name;
|
||
|
u8 sha256[SHA256_DIGEST_SIZE];
|
||
|
|
||
|
if (likely(fname->disk_name.name)) {
|
||
|
if (de_name_len != fname->disk_name.len)
|
||
|
return false;
|
||
|
return !memcmp(de_name, fname->disk_name.name, de_name_len);
|
||
|
}
|
||
|
if (de_name_len <= sizeof(nokey_name->bytes))
|
||
|
return false;
|
||
|
if (memcmp(de_name, nokey_name->bytes, sizeof(nokey_name->bytes)))
|
||
|
return false;
|
||
|
if (fscrypt_do_sha256(&de_name[sizeof(nokey_name->bytes)],
|
||
|
de_name_len - sizeof(nokey_name->bytes), sha256))
|
||
|
return false;
|
||
|
return !memcmp(sha256, nokey_name->sha256, sizeof(sha256));
|
||
|
}
|
||
|
EXPORT_SYMBOL_GPL(fscrypt_match_name);
|
||
|
|
||
|
/**
|
||
|
* fscrypt_fname_siphash() - calculate the SipHash of a filename
|
||
|
* @dir: the parent directory
|
||
|
* @name: the filename to calculate the SipHash of
|
||
|
*
|
||
|
* Given a plaintext filename @name and a directory @dir which uses SipHash as
|
||
|
* its dirhash method and has had its fscrypt key set up, this function
|
||
|
* calculates the SipHash of that name using the directory's secret dirhash key.
|
||
|
*
|
||
|
* Return: the SipHash of @name using the hash key of @dir
|
||
|
*/
|
||
|
u64 fscrypt_fname_siphash(const struct inode *dir, const struct qstr *name)
|
||
|
{
|
||
|
const struct fscrypt_info *ci = dir->i_crypt_info;
|
||
|
|
||
|
WARN_ON(!ci->ci_dirhash_key_initialized);
|
||
|
|
||
|
return siphash(name->name, name->len, &ci->ci_dirhash_key);
|
||
|
}
|
||
|
EXPORT_SYMBOL_GPL(fscrypt_fname_siphash);
|
||
|
|
||
|
/*
|
||
|
* Validate dentries in encrypted directories to make sure we aren't potentially
|
||
|
* caching stale dentries after a key has been added.
|
||
|
*/
|
||
|
int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
|
||
|
{
|
||
|
struct dentry *dir;
|
||
|
int err;
|
||
|
int valid;
|
||
|
|
||
|
/*
|
||
|
* Plaintext names are always valid, since fscrypt doesn't support
|
||
|
* reverting to ciphertext names without evicting the directory's inode
|
||
|
* -- which implies eviction of the dentries in the directory.
|
||
|
*/
|
||
|
if (!(dentry->d_flags & DCACHE_ENCRYPTED_NAME))
|
||
|
return 1;
|
||
|
|
||
|
/*
|
||
|
* Ciphertext name; valid if the directory's key is still unavailable.
|
||
|
*
|
||
|
* Although fscrypt forbids rename() on ciphertext names, we still must
|
||
|
* use dget_parent() here rather than use ->d_parent directly. That's
|
||
|
* because a corrupted fs image may contain directory hard links, which
|
||
|
* the VFS handles by moving the directory's dentry tree in the dcache
|
||
|
* each time ->lookup() finds the directory and it already has a dentry
|
||
|
* elsewhere. Thus ->d_parent can be changing, and we must safely grab
|
||
|
* a reference to some ->d_parent to prevent it from being freed.
|
||
|
*/
|
||
|
|
||
|
if (flags & LOOKUP_RCU)
|
||
|
return -ECHILD;
|
||
|
|
||
|
dir = dget_parent(dentry);
|
||
|
err = fscrypt_get_encryption_info(d_inode(dir));
|
||
|
valid = !fscrypt_has_encryption_key(d_inode(dir));
|
||
|
dput(dir);
|
||
|
|
||
|
if (err < 0)
|
||
|
return err;
|
||
|
|
||
|
return valid;
|
||
|
}
|
||
|
EXPORT_SYMBOL_GPL(fscrypt_d_revalidate);
|