Commit 1c5100a2 authored by Eric Biggers's avatar Eric Biggers
Browse files

fscrypt: clean up base64 encoding/decoding 



Some minor cleanups for the code that base64 encodes and decodes
encrypted filenames and long name digests:

- Rename "digest_{encode,decode}()" => "base64_{encode,decode}()" since
  they are used for filenames too, not just for long name digests.
- Replace 'while' loops with more conventional 'for' loops.
- Use 'u8' for binary data.  Keep 'char' for string data.
- Fully constify the lookup table (pointer was not const).
- Improve comment.

No actual change in behavior.

Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
parent 75798f85

fs/crypto/fname.c

+17 −17
Original line number Diff line number Diff line
@@ -127,44 +127,45 @@ static int fname_decrypt(struct inode *inode, 
	return 0;

}



static const char *lookup_table =

static const char lookup_table[65] =

	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";



#define BASE64_CHARS(nbytes)	DIV_ROUND_UP((nbytes) * 4, 3)



/**

 * digest_encode() -

 * base64_encode() -

 *

 * Encodes the input digest using characters from the set [a-zA-Z0-9_+].

 * 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 digest_encode(const char *src, int len, char *dst)

static int base64_encode(const u8 *src, int len, char *dst)

{

	int i = 0, bits = 0, ac = 0;

	int i, bits = 0, ac = 0;

	char *cp = dst;



	while (i < len) {

		ac += (((unsigned char) src[i]) << bits);

	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);

		i++;

	}

	if (bits)

		*cp++ = lookup_table[ac & 0x3f];

	return cp - dst;

}



static int digest_decode(const char *src, int len, char *dst)

static int base64_decode(const char *src, int len, u8 *dst)

{

	int i = 0, bits = 0, ac = 0;

	int i, bits = 0, ac = 0;

	const char *p;

	char *cp = dst;

	u8 *cp = dst;



	while (i < len) {

	for (i = 0; i < len; i++) {

		p = strchr(lookup_table, src[i]);

		if (p == NULL || src[i] == 0)

			return -2;
@@ -175,7 +176,6 @@ static int digest_decode(const char *src, int len, char *dst) 
			ac >>= 8;

			bits -= 8;

		}

		i++;

	}

	if (ac)

		return -1;
@@ -272,7 +272,7 @@ int fscrypt_fname_disk_to_usr(struct inode *inode, 
		return fname_decrypt(inode, iname, oname);



	if (iname->len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) {

		oname->len = digest_encode(iname->name, iname->len,

		oname->len = base64_encode(iname->name, iname->len,

					   oname->name);

		return 0;

	}
@@ -287,7 +287,7 @@ int fscrypt_fname_disk_to_usr(struct inode *inode, 
	       FSCRYPT_FNAME_DIGEST(iname->name, iname->len),

	       FSCRYPT_FNAME_DIGEST_SIZE);

	oname->name[0] = '_';

	oname->len = 1 + digest_encode((const char *)&digested_name,

	oname->len = 1 + base64_encode((const u8 *)&digested_name,

				       sizeof(digested_name), oname->name + 1);

	return 0;

}
@@ -380,7 +380,7 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname, 
	if (fname->crypto_buf.name == NULL)

		return -ENOMEM;



	ret = digest_decode(iname->name + digested, iname->len - digested,

	ret = base64_decode(iname->name + digested, iname->len - digested,

			    fname->crypto_buf.name);

	if (ret < 0) {

		ret = -ENOENT;

CRA Git | Maintained and supported by SUSTech CRA and CCSE