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Message-ID: <alpine.DEB.2.00.1204031334460.4560@eristoteles.iwoars.net>
Date: Tue, 3 Apr 2012 13:35:02 +0200 (CEST)
From: Joel Reardon <joel@...mbassador.com>
To: Guillaume LECERF <glecerf@...il.com>
cc: Artem Bityutskiy <dedekind1@...il.com>,
linux-fsdevel@...r.kernel.org, linux-mtd@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [patch] UBIFS: Add cryptographic functionality when a key is
passed to the compress / decompress functions
Without the goto:
Signed-off-by: Joel Reardon <reardonj@....ethz.ch>
---
fs/ubifs/compress.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++---
fs/ubifs/ubifs.h | 8 +++++-
2 files changed, 77 insertions(+), 5 deletions(-)
diff --git a/fs/ubifs/compress.c b/fs/ubifs/compress.c
index b796b8d..61fe584 100644
--- a/fs/ubifs/compress.c
+++ b/fs/ubifs/compress.c
@@ -27,9 +27,12 @@
* decompression.
*/
-#include <linux/crypto.h>
#include "ubifs.h"
+#include <linux/crypto.h>
+#include <linux/scatterlist.h>
+
+
/* Fake description object for the "none" compressor */
static struct ubifs_compressor none_compr = {
.compr_type = UBIFS_COMPR_NONE,
@@ -75,6 +78,53 @@ static struct ubifs_compressor zlib_compr = {
struct ubifs_compressor *ubifs_compressors[UBIFS_COMPR_TYPES_CNT];
/**
+ * ubifs_aes_crypt - encrypt / decrypt data.
+ * @str: data to crypt
+ * @len: length of the data
+ * @crypto_key: the cryptographic key to use to crypt the data
+ * @iv: the initialization vector to use
+ *
+ * This function applies aes encryption to the data. It is done in counter
+ * mode, which means that encryption and decryption are the same operation,
+ * i.e., it XORs the same generated bitstream, so it can be used both for
+ * encryption / decryption. The operation is done in-place, so str mutates.
+ * Both crypto_key and iv are valid pointers to a buffer of length
+ * UBIFS_CRYPTO_KEYSIZE.
+ */
+int ubifs_aes_crypt(void *str, int len, u8 *crypto_key, u8 *iv)
+{
+ struct crypto_blkcipher *tfm;
+ struct blkcipher_desc desc;
+ struct scatterlist sg;
+ int err = 0;
+
+ tfm = crypto_alloc_blkcipher(UBIFS_CRYPTO_ALGORITHM, 0, 0);
+ if (IS_ERR(tfm)) {
+ ubifs_err("failed to load transform for aes: %ld",
+ PTR_ERR(tfm));
+ return err;
+ }
+
+ err = crypto_blkcipher_setkey(tfm, crypto_key, UBIFS_CRYPTO_KEYSIZE);
+ desc.tfm = tfm;
+ desc.flags = 0;
+ if (err) {
+ ubifs_err("crypto_blkcipher_setkey() failed flags=%#x",
+ crypto_blkcipher_get_flags(tfm));
+ return err;
+ }
+
+ memset(&sg, 0, sizeof(struct scatterlist));
+ sg_set_buf(&sg, str, len);
+ desc.info = iv;
+ err = crypto_blkcipher_encrypt(&desc, &sg, &sg, len);
+ crypto_free_blkcipher(tfm);
+ if (err)
+ return err;
+ return 0;
+}
+
+/**
* ubifs_compress - compress data.
* @in_buf: data to compress
* @in_len: length of the data to compress
@@ -126,13 +176,20 @@ void ubifs_compress(const void *in_buf, int in_len, void *out_buf, int *out_len,
*/
if (in_len - *out_len < UBIFS_MIN_COMPRESS_DIFF)
goto no_compr;
-
- return;
+ goto encrypt;
no_compr:
memcpy(out_buf, in_buf, in_len);
*out_len = in_len;
*compr_type = UBIFS_COMPR_NONE;
+
+encrypt:
+ if (crypto_key) {
+ u8 iv[UBIFS_CRYPTO_KEYSIZE];
+
+ memset(iv, 0, UBIFS_CRYPTO_KEYSIZE);
+ ubifs_aes_crypt(out_buf, *out_len, crypto_key, iv);
+ }
}
/**
@@ -148,8 +205,10 @@ no_compr:
* This function decompresses data from buffer @in_buf into buffer @out_buf.
* The length of the uncompressed data is returned in @out_len. This functions
* returns %0 on success or a negative error code on failure.
+ *
+ * WARNING: this function may modify the contents of in_buf when executing.
*/
-int ubifs_decompress(const void *in_buf, int in_len, void *out_buf,
+int ubifs_decompress(void *in_buf, int in_len, void *out_buf,
int *out_len, int compr_type, u8 *crypto_key)
{
int err;
@@ -167,6 +226,13 @@ int ubifs_decompress(const void *in_buf, int in_len, void *out_buf,
return -EINVAL;
}
+ if (crypto_key) {
+ u8 iv[UBIFS_CRYPTO_KEYSIZE];
+
+ memset(iv, 0, UBIFS_CRYPTO_KEYSIZE);
+ ubifs_aes_crypt(in_buf, in_len, crypto_key, iv);
+ }
+
if (compr_type == UBIFS_COMPR_NONE) {
memcpy(out_buf, in_buf, in_len);
*out_len = in_len;
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 3ed12be..84d2c49 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -160,6 +160,11 @@
/* Maximum number of data nodes to bulk-read */
#define UBIFS_MAX_BULK_READ 32
+/* 128 bit key size in bytes for UBIFS */
+#define UBIFS_CRYPTO_KEYSIZE 16
+/* AES in counter mode is the encryption algorithm. */
+#define UBIFS_CRYPTO_ALGORITHM "ctr(aes)"
+
/*
* Lockdep classes for UBIFS inode @ui_mutex.
*/
@@ -1771,9 +1776,10 @@ long ubifs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
/* compressor.c */
int __init ubifs_compressors_init(void);
void ubifs_compressors_exit(void);
+int ubifs_aes_crypt(void *str, int len, u8 *crypto_key, u8 *iv);
void ubifs_compress(const void *in_buf, int in_len, void *out_buf, int *out_len,
int *compr_type, u8 *crypto_key);
-int ubifs_decompress(const void *buf, int len, void *out, int *out_len,
+int ubifs_decompress(void *buf, int len, void *out, int *out_len,
int compr_type, u8 *crypto_key);
#include "debug.h"
--
1.7.5.4
--
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