linux/fs/crypto/fname.c
Eric Biggers 27e47a6342 fscrypt: inline fscrypt_free_filename()
fscrypt_free_filename() only needs to do a kfree() of crypto_buf.name,
which works well as an inline function.  We can skip setting the various
pointers to NULL, since no user cares about it (the name is always freed
just before it goes out of scope).

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: David Gstir <david@sigma-star.at>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2017-06-23 19:59:08 -04:00

456 lines
12 KiB
C

/*
* 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/scatterlist.h>
#include <linux/ratelimit.h>
#include "fscrypt_private.h"
/**
* fname_crypt_complete() - completion callback for filename crypto
* @req: The asynchronous cipher request context
* @res: The result of the cipher operation
*/
static void fname_crypt_complete(struct crypto_async_request *req, int res)
{
struct fscrypt_completion_result *ecr = req->data;
if (res == -EINPROGRESS)
return;
ecr->res = res;
complete(&ecr->completion);
}
/**
* fname_encrypt() - encrypt a filename
*
* The caller must have allocated sufficient memory for the @oname string.
*
* Return: 0 on success, -errno on failure
*/
static int fname_encrypt(struct inode *inode,
const struct qstr *iname, struct fscrypt_str *oname)
{
struct skcipher_request *req = NULL;
DECLARE_FS_COMPLETION_RESULT(ecr);
struct fscrypt_info *ci = inode->i_crypt_info;
struct crypto_skcipher *tfm = ci->ci_ctfm;
int res = 0;
char iv[FS_CRYPTO_BLOCK_SIZE];
struct scatterlist sg;
int padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
unsigned int lim;
unsigned int cryptlen;
lim = inode->i_sb->s_cop->max_namelen(inode);
if (iname->len <= 0 || iname->len > lim)
return -EIO;
/*
* Copy the filename to the output buffer for encrypting in-place and
* pad it with the needed number of NUL bytes.
*/
cryptlen = max_t(unsigned int, iname->len, FS_CRYPTO_BLOCK_SIZE);
cryptlen = round_up(cryptlen, padding);
cryptlen = min(cryptlen, lim);
memcpy(oname->name, iname->name, iname->len);
memset(oname->name + iname->len, 0, cryptlen - iname->len);
/* Initialize the IV */
memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
/* Set up the encryption request */
req = skcipher_request_alloc(tfm, GFP_NOFS);
if (!req) {
printk_ratelimited(KERN_ERR
"%s: skcipher_request_alloc() failed\n", __func__);
return -ENOMEM;
}
skcipher_request_set_callback(req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
fname_crypt_complete, &ecr);
sg_init_one(&sg, oname->name, cryptlen);
skcipher_request_set_crypt(req, &sg, &sg, cryptlen, iv);
/* Do the encryption */
res = crypto_skcipher_encrypt(req);
if (res == -EINPROGRESS || res == -EBUSY) {
/* Request is being completed asynchronously; wait for it */
wait_for_completion(&ecr.completion);
res = ecr.res;
}
skcipher_request_free(req);
if (res < 0) {
printk_ratelimited(KERN_ERR
"%s: Error (error code %d)\n", __func__, res);
return res;
}
oname->len = cryptlen;
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 fscrypt_str *iname,
struct fscrypt_str *oname)
{
struct skcipher_request *req = NULL;
DECLARE_FS_COMPLETION_RESULT(ecr);
struct scatterlist src_sg, dst_sg;
struct fscrypt_info *ci = inode->i_crypt_info;
struct crypto_skcipher *tfm = ci->ci_ctfm;
int res = 0;
char iv[FS_CRYPTO_BLOCK_SIZE];
unsigned lim;
lim = inode->i_sb->s_cop->max_namelen(inode);
if (iname->len <= 0 || iname->len > lim)
return -EIO;
/* Allocate request */
req = skcipher_request_alloc(tfm, GFP_NOFS);
if (!req) {
printk_ratelimited(KERN_ERR
"%s: crypto_request_alloc() failed\n", __func__);
return -ENOMEM;
}
skcipher_request_set_callback(req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
fname_crypt_complete, &ecr);
/* Initialize IV */
memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
/* 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_skcipher_decrypt(req);
if (res == -EINPROGRESS || res == -EBUSY) {
wait_for_completion(&ecr.completion);
res = ecr.res;
}
skcipher_request_free(req);
if (res < 0) {
printk_ratelimited(KERN_ERR
"%s: Error (error code %d)\n", __func__, res);
return res;
}
oname->len = strnlen(oname->name, iname->len);
return 0;
}
static const char *lookup_table =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
#define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
/**
* digest_encode() -
*
* Encodes the input digest using characters from the set [a-zA-Z0-9_+].
* The encoded string is roughly 4/3 times the size of the input string.
*/
static int digest_encode(const char *src, int len, char *dst)
{
int i = 0, bits = 0, ac = 0;
char *cp = dst;
while (i < len) {
ac += (((unsigned char) src[i]) << bits);
bits += 8;
do {
*cp++ = lookup_table[ac & 0x3f];
ac >>= 6;
bits -= 6;
} while (bits >= 6);
i++;
}
if (bits)
*cp++ = lookup_table[ac & 0x3f];
return cp - dst;
}
static int digest_decode(const char *src, int len, char *dst)
{
int i = 0, bits = 0, ac = 0;
const char *p;
char *cp = dst;
while (i < len) {
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;
}
i++;
}
if (ac)
return -1;
return cp - dst;
}
u32 fscrypt_fname_encrypted_size(const struct inode *inode, u32 ilen)
{
int padding = 32;
struct fscrypt_info *ci = inode->i_crypt_info;
if (ci)
padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
ilen = max(ilen, (u32)FS_CRYPTO_BLOCK_SIZE);
return round_up(ilen, padding);
}
EXPORT_SYMBOL(fscrypt_fname_encrypted_size);
/**
* fscrypt_fname_crypto_alloc_obuff() -
*
* Allocates an output buffer that is sufficient for the crypto operation
* specified by the context and the direction.
*/
int fscrypt_fname_alloc_buffer(const struct inode *inode,
u32 ilen, struct fscrypt_str *crypto_str)
{
u32 olen = fscrypt_fname_encrypted_size(inode, ilen);
const u32 max_encoded_len =
max_t(u32, BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE),
1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name)));
crypto_str->len = olen;
olen = max(olen, max_encoded_len);
/*
* Allocated buffer can hold one more character to null-terminate the
* string
*/
crypto_str->name = kmalloc(olen + 1, GFP_NOFS);
if (!(crypto_str->name))
return -ENOMEM;
return 0;
}
EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);
/**
* fscrypt_fname_crypto_free_buffer() -
*
* Frees the buffer allocated for crypto operation.
*/
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() - 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 fscrypt_digested_name format.
*
* Return: 0 on success, -errno on failure
*/
int fscrypt_fname_disk_to_usr(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_digested_name digested_name;
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 (inode->i_crypt_info)
return fname_decrypt(inode, iname, oname);
if (iname->len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) {
oname->len = digest_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,
FSCRYPT_FNAME_DIGEST(iname->name, iname->len),
FSCRYPT_FNAME_DIGEST_SIZE);
oname->name[0] = '_';
oname->len = 1 + digest_encode((const char *)&digested_name,
sizeof(digested_name), oname->name + 1);
return 0;
}
EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
/**
* fscrypt_fname_usr_to_disk() - converts a filename from user space to disk
* space
*
* The caller must have allocated sufficient memory for the @oname string.
*
* Return: 0 on success, -errno on failure
*/
int fscrypt_fname_usr_to_disk(struct inode *inode,
const struct qstr *iname,
struct fscrypt_str *oname)
{
if (fscrypt_is_dot_dotdot(iname)) {
oname->name[0] = '.';
oname->name[iname->len - 1] = '.';
oname->len = iname->len;
return 0;
}
if (inode->i_crypt_info)
return fname_encrypt(inode, iname, oname);
/*
* Without a proper key, a user is not allowed to modify the filenames
* in a directory. Consequently, a user space name cannot be mapped to
* a disk-space name
*/
return -ENOKEY;
}
EXPORT_SYMBOL(fscrypt_fname_usr_to_disk);
/**
* 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 either the ciphertext disk_name (for short names) or the
* fscrypt_digested_name (for long names). 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)
{
int ret;
int digested;
memset(fname, 0, sizeof(struct fscrypt_name));
fname->usr_fname = iname;
if (!dir->i_sb->s_cop->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 && ret != -EOPNOTSUPP)
return ret;
if (dir->i_crypt_info) {
ret = fscrypt_fname_alloc_buffer(dir, iname->len,
&fname->crypto_buf);
if (ret)
return ret;
ret = fname_encrypt(dir, iname, &fname->crypto_buf);
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;
/*
* We don't have the key and we are doing a lookup; decode the
* user-supplied name
*/
if (iname->name[0] == '_') {
if (iname->len !=
1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name)))
return -ENOENT;
digested = 1;
} else {
if (iname->len >
BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE))
return -ENOENT;
digested = 0;
}
fname->crypto_buf.name =
kmalloc(max_t(size_t, FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE,
sizeof(struct fscrypt_digested_name)),
GFP_KERNEL);
if (fname->crypto_buf.name == NULL)
return -ENOMEM;
ret = digest_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 fscrypt_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:
fscrypt_fname_free_buffer(&fname->crypto_buf);
return ret;
}
EXPORT_SYMBOL(fscrypt_setup_filename);