Viewing: fname.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.
*/
/*
* Linux commit 219d54332a09
* tags/v5.4
*/
#include <linux/scatterlist.h>
#include <crypto/skcipher.h>
#include "llcrypt_private.h"
static inline bool llcrypt_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;
}
/**
* fname_encrypt() - encrypt a filename
*
* The output buffer must be at least as large as the input buffer.
* Any extra space is filled with NUL padding before encryption.
*
* Return: 0 on success, -errno on failure
*/
int fname_encrypt(struct inode *inode, const struct qstr *iname,
u8 *out, unsigned int olen)
{
struct skcipher_request *req = NULL;
DECLARE_CRYPTO_WAIT(wait);
struct llcrypt_info *ci = llcrypt_info(inode);
struct crypto_skcipher *tfm = ci->ci_ctfm;
union llcrypt_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);
if (tfm == NULL)
return 0;
/* Initialize the IV */
llcrypt_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) {
llcrypt_err(inode, "Filename encryption failed: %d", res);
return res;
}
return 0;
}
/**
* fname_decrypt() - decrypt a filename
*
* The caller must have allocated sufficient memory for the @oname string.
*
* Return: 0 on success, -errno on failure
*/
static int fname_decrypt(struct inode *inode,
const struct llcrypt_str *iname,
struct llcrypt_str *oname)
{
struct skcipher_request *req = NULL;
DECLARE_CRYPTO_WAIT(wait);
struct scatterlist src_sg, dst_sg;
struct llcrypt_info *ci = llcrypt_info(inode);
struct crypto_skcipher *tfm = ci->ci_ctfm;
union llcrypt_iv iv;
int res;
if (tfm == NULL) {
memcpy(oname->name, iname->name, iname->len);
oname->name[iname->len] = '\0';
oname->len = iname->len;
return 0;
}
/* 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 */
llcrypt_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) {
llcrypt_err(inode, "Filename decryption failed: %d", res);
return res;
}
oname->len = strnlen(oname->name, iname->len);
return 0;
}
/*
* Old fashion base64 encoding, taken from Linux 5.4.
*
* This base64 encoding is specific to fscrypt and has been replaced since then
* with an RFC 4648 compliant base64-url encoding, see llcrypt_base64url_*
* below.
* The old fashion base64 encoding is kept for compatibility with older clients.
*/
static const char lookup_table[65] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
#define LLCRYPT_BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
/**
* base64_encode() -
*
* 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 inline int llcrypt_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 inline int llcrypt_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;
}
/*
* New fashion base64 encoding, taken from Linux 5.14.
*
* This base64 encoding is RFC 4648 compliant base64-url encoding.
*/
#define LLCRYPT_BASE64URL_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
/**
* llcrypt_base64url_encode() - base64url-encode some binary data
* @src: the binary data to encode
* @srclen: the length of @src in bytes
* @dst: (output) the base64url-encoded string. Not NUL-terminated.
*
* Encodes data using base64url encoding, i.e. the "Base 64 Encoding with URL
* and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't used,
* as it's unneeded and not required by the RFC. base64url is used instead of
* base64 to avoid the '/' character, which isn't allowed in filenames.
*
* Return: the length of the resulting base64url-encoded string in bytes.
* This will be equal to LLCRYPT_BASE64URL_CHARS(srclen).
*/
static inline int llcrypt_base64url_encode(const u8 *src, int srclen, char *dst)
{
u32 ac = 0;
int bits = 0;
int i;
char *cp = dst;
for (i = 0; i < srclen; i++) {
ac = (ac << 8) | src[i];
bits += 8;
do {
bits -= 6;
*cp++ = base64url_table[(ac >> bits) & 0x3f];
} while (bits >= 6);
}
if (bits)
*cp++ = base64url_table[(ac << (6 - bits)) & 0x3f];
return cp - dst;
}
/**
* llcrypt_base64url_decode() - base64url-decode a string
* @src: the string to decode. Doesn't need to be NUL-terminated.
* @srclen: the length of @src in bytes
* @dst: (output) the decoded binary data
*
* Decodes a string using base64url encoding, i.e. the "Base 64 Encoding with
* URL and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't
* accepted, nor are non-encoding characters such as whitespace.
*
* This implementation hasn't been optimized for performance.
*
* Return: the length of the resulting decoded binary data in bytes,
* or -1 if the string isn't a valid base64url string.
*/
static inline int llcrypt_base64url_decode(const char *src, int srclen, u8 *dst)
{
u32 ac = 0;
int bits = 0;
int i;
u8 *bp = dst;
for (i = 0; i < srclen; i++) {
const char *p = strchr(base64url_table, src[i]);
if (p == NULL || src[i] == 0)
return -1;
ac = (ac << 6) | (p - base64url_table);
bits += 6;
if (bits >= 8) {
bits -= 8;
*bp++ = (u8)(ac >> bits);
}
}
if (ac & ((1 << bits) - 1))
return -1;
return bp - dst;
}
static inline int base64_chars(struct lustre_sb_info *lsi, int nbytes)
{
if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
return LLCRYPT_BASE64URL_CHARS(nbytes);
else
return LLCRYPT_BASE64_CHARS(nbytes);
}
bool llcrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
u32 max_len, u32 *encrypted_len_ret)
{
const struct llcrypt_info *ci = llcrypt_info(inode);
struct crypto_skcipher *tfm = ci->ci_ctfm;
int padding = 4 << (llcrypt_policy_flags(&ci->ci_policy) &
LLCRYPT_POLICY_FLAGS_PAD_MASK);
u32 encrypted_len;
if (orig_len > max_len)
return false;
if (tfm == NULL) {
*encrypted_len_ret = orig_len;
} else {
encrypted_len = max(orig_len, (u32)LL_CRYPTO_BLOCK_SIZE);
encrypted_len = round_up(encrypted_len, padding);
*encrypted_len_ret = min(encrypted_len, max_len);
}
return true;
}
/**
* llcrypt_fname_alloc_buffer - allocate a buffer for presented filenames
*
* 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 llcrypt_fname_alloc_buffer(const struct inode *inode,
u32 max_encrypted_len,
struct llcrypt_str *crypto_str)
{
struct lustre_sb_info *lsi = s2lsi(inode->i_sb);
const u32 max_encoded_len =
max_t(u32,
base64_chars(lsi, LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE),
1 + base64_chars(lsi, sizeof(struct llcrypt_digested_name)));
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(llcrypt_fname_alloc_buffer);
/**
* llcrypt_fname_free_buffer - free the buffer for presented filenames
*
* Free the buffer allocated by llcrypt_fname_alloc_buffer().
*/
void llcrypt_fname_free_buffer(struct llcrypt_str *crypto_str)
{
if (!crypto_str)
return;
kfree(crypto_str->name);
crypto_str->name = NULL;
}
EXPORT_SYMBOL(llcrypt_fname_free_buffer);
/**
* llcrypt_fname_disk_to_usr() - converts a filename from disk space to user
* space
*
* The caller must have allocated sufficient memory for the @oname string.
*
* If the key is available, we'll decrypt the disk name; otherwise, we'll encode
* it for presentation. Short names are directly base64-encoded, while long
* names are encoded in llcrypt_digested_name format.
*
* Return: 0 on success, -errno on failure
*/
int llcrypt_fname_disk_to_usr(struct inode *inode,
u32 hash, u32 minor_hash,
const struct llcrypt_str *iname,
struct llcrypt_str *oname)
{
int (*b64_encode)(const u8 *src, int srclen, char *dst);
struct lustre_sb_info *lsi = s2lsi(inode->i_sb);
const struct qstr qname = LLTR_TO_QSTR(iname);
struct llcrypt_digested_name digested_name;
if (llcrypt_is_dot_dotdot(&qname)) {
oname->name[0] = '.';
oname->name[iname->len - 1] = '.';
oname->len = iname->len;
return 0;
}
if (llcrypt_has_encryption_key(inode)) {
struct llcrypt_info *ci = llcrypt_info(inode);
struct crypto_skcipher *tfm = ci->ci_ctfm;
if (tfm && iname->len < LL_CRYPTO_BLOCK_SIZE)
return -EUCLEAN;
return fname_decrypt(inode, iname, oname);
}
if (!llcrypt_policy_has_filename_enc(inode)) {
memcpy(oname->name, iname->name, iname->len);
oname->name[iname->len] = '\0';
oname->len = iname->len;
return 0;
}
if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
b64_encode = llcrypt_base64url_encode;
else
b64_encode = llcrypt_base64_encode;
if (iname->len <= LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE) {
oname->len = b64_encode(iname->name, iname->len, oname->name);
return 0;
}
if (hash) {
digested_name.hash = hash;
digested_name.minor_hash = minor_hash;
} else {
digested_name.hash = 0;
digested_name.minor_hash = 0;
}
memcpy(digested_name.digest,
LLCRYPT_FNAME_DIGEST(iname->name, iname->len),
LLCRYPT_FNAME_DIGEST_SIZE);
if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
oname->name[0] = LLCRYPT_DIGESTED_CHAR;
else
oname->name[0] = LLCRYPT_DIGESTED_CHAR_OLD;
oname->len = 1 + b64_encode((const u8 *)&digested_name,
sizeof(digested_name), oname->name + 1);
return 0;
}
EXPORT_SYMBOL(llcrypt_fname_disk_to_usr);
/**
* llcrypt_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 either the ciphertext disk_name (for short names) or the
* llcrypt_digested_name (for long names). Non-@lookup operations will be
* impossible in this case, so we fail them with ENOKEY.
*
* If successful, llcrypt_free_filename() must be called later to clean up.
*
* Return: 0 on success, -errno on failure
*/
int llcrypt_setup_filename(struct inode *dir, const struct qstr *iname,
int lookup, struct llcrypt_name *fname)
{
struct lustre_sb_info *lsi = s2lsi(dir->i_sb);
int ret;
int digested;
memset(fname, 0, sizeof(struct llcrypt_name));
fname->usr_fname = iname;
if (!IS_ENCRYPTED(dir) || llcrypt_is_dot_dotdot(iname)) {
fname->disk_name.name = (unsigned char *)iname->name;
fname->disk_name.len = iname->len;
return 0;
}
ret = llcrypt_get_encryption_info(dir);
if (ret)
return ret;
if (llcrypt_has_encryption_key(dir)) {
struct lustre_sb_info *lsi = s2lsi(dir->i_sb);
if (!llcrypt_fname_encrypted_size(dir, iname->len,
lsi ?
lsi->lsi_cop->max_namelen :
NAME_MAX,
&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 = 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;
if (!llcrypt_policy_has_filename_enc(dir)) {
fname->disk_name.name = (unsigned char *)iname->name;
fname->disk_name.len = iname->len;
return 0;
}
fname->is_ciphertext_name = true;
/*
* We don't have the key and we are doing a lookup; decode the
* user-supplied name
*/
if ((!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI) &&
iname->name[0] == LLCRYPT_DIGESTED_CHAR) ||
((lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI) &&
iname->name[0] == LLCRYPT_DIGESTED_CHAR_OLD)) {
if (iname->len != 1 + base64_chars(lsi,
sizeof(struct llcrypt_digested_name))) {
return -ENOENT;
}
digested = 1;
} else {
if (iname->len >
base64_chars(lsi, LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE))
return -ENOENT;
digested = 0;
}
fname->crypto_buf.name =
kmalloc(max_t(size_t, LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE,
sizeof(struct llcrypt_digested_name)),
GFP_KERNEL);
if (fname->crypto_buf.name == NULL)
return -ENOMEM;
if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
ret = llcrypt_base64url_decode(iname->name + digested,
iname->len - digested,
fname->crypto_buf.name);
else
ret = llcrypt_base64_decode(iname->name + digested,
iname->len - digested,
fname->crypto_buf.name);
if (ret < 0) {
ret = -ENOENT;
goto errout;
}
fname->crypto_buf.len = ret;
if (digested) {
const struct llcrypt_digested_name *n =
(const void *)fname->crypto_buf.name;
fname->hash = n->hash;
fname->minor_hash = n->minor_hash;
} else {
fname->disk_name.name = fname->crypto_buf.name;
fname->disk_name.len = fname->crypto_buf.len;
}
return 0;
errout:
kfree(fname->crypto_buf.name);
return ret;
}
EXPORT_SYMBOL(llcrypt_setup_filename);
