lkml.org 
[lkml]   [2008]   [Nov]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] eCryptfs: Clean up ecryptfs_decode_from_filename()
On Thu, Nov 06, 2008 at 02:12:54PM -0800, Andrew Morton wrote:
> On Tue, 4 Nov 2008 15:41:20 -0600
> Michael Halcrow <mhalcrow@us.ibm.com> wrote:
> > +static unsigned char filename_rev_map[] = {
> > + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 7 */
> > + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 15 */
> > + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 23 */
> > + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 31 */
> > + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 39 */
> > + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* 47 */
> > + 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, /* 55 */
> > + 0x0A, 0x0B, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 63 */
> > + 0x00, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, /* 71 */
> > + 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, /* 79 */
> > + 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, /* 87 */
> > + 0x23, 0x24, 0x25, 0x00, 0x00, 0x00, 0x00, 0x00, /* 95 */
> > + 0x00, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, /* 103 */
> > + 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, /* 111 */
> > + 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, /* 119 */
> > + 0x3D, 0x3E, 0x3F
> > +};
>
> You might as well make this const also if poss. It doesn't make much
> difference, apart from putting the table into write-protected
> memory.
> >
> > ...
> >
> > +int ecryptfs_decode_from_filename(unsigned char *dst, size_t *dst_size,
> > + const unsigned char *src, size_t src_size)
> > +{
> > + u8 current_bit_offset = 0;
> > + size_t src_byte_offset = 0;
> > + size_t dst_byte_offset = 0;
> > + int rc = 0;
> > +
> > + if (dst == NULL) {
> > + /* Not exact; conservatively long */
> > + (*dst_size) = (((src_size + 1) * 3) / 4);
>
> Are you sure about that? The destination will be 0.75 times as long
> as the source? Seems risky.
>
> What's this code doing anyway? At a guess, I'd say that it's a
> special mode to this function which provides the caller with an
> estimate of how much storage needs to be allocated to decode *src.
> Or maybe that guess was completely wrong. A comment is needed,
> methinks.

Flesh out the comments for ecryptfs_decode_from_filename(). Remove the
return condition, since it is always 0.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
---
fs/ecryptfs/crypto.c | 51 +++++++++++++++++++++++--------------------------
1 files changed, 24 insertions(+), 27 deletions(-)
diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index e935a22..c01e043 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -1931,7 +1931,7 @@ static unsigned char *portable_filename_chars = ("-.0123456789ABCD"

/* We could either offset on every reverse map or just pad some 0x00's
* at the front here */
-static unsigned char filename_rev_map[] = {
+static const unsigned char filename_rev_map[] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 7 */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 15 */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 23 */
@@ -2012,16 +2012,30 @@ out:
return;
}

-int ecryptfs_decode_from_filename(unsigned char *dst, size_t *dst_size,
- const unsigned char *src, size_t src_size)
+/**
+ * ecryptfs_decode_from_filename
+ * @dst: If NULL, this function only sets @dst_size and returns. If
+ * non-NULL, this function decodes the encoded octets in @src
+ * into the memory that @dst points to.
+ * @dst_size: Set to the size of the decoded string.
+ * @src: The encoded set of octets to decode.
+ * @src_size: The size of the encoded set of octets to decode.
+ */
+static void
+ecryptfs_decode_from_filename(unsigned char *dst, size_t *dst_size,
+ const unsigned char *src, size_t src_size)
{
u8 current_bit_offset = 0;
size_t src_byte_offset = 0;
size_t dst_byte_offset = 0;
- int rc = 0;

if (dst == NULL) {
- /* Not exact; conservatively long */
+ /* Not exact; conservatively long. Every block of 4
+ * encoded characters decodes into a block of 3
+ * decoded characters. This segment of code provides
+ * the caller with the maximum amount of allocated
+ * space that @dst will need to point to in a
+ * subsequent call. */
(*dst_size) = (((src_size + 1) * 3) / 4);
goto out;
}
@@ -2055,7 +2069,7 @@ int ecryptfs_decode_from_filename(unsigned char *dst, size_t *dst_size,
}
(*dst_size) = dst_byte_offset;
out:
- return rc;
+ return;
}

/**
@@ -2208,16 +2222,8 @@ int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,

name += ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
name_size -= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
- rc = ecryptfs_decode_from_filename(NULL, &decoded_name_size,
- name, name_size);
- if (rc) {
- printk(KERN_ERR "%s: Error attempting to decode "
- "filename; rc = [%d]\n", __func__, rc);
- rc = ecryptfs_copy_filename(plaintext_name,
- plaintext_name_size,
- orig_name, orig_name_size);
- goto out;
- }
+ ecryptfs_decode_from_filename(NULL, &decoded_name_size,
+ name, name_size);
decoded_name = kmalloc(decoded_name_size, GFP_KERNEL);
if (!decoded_name) {
printk(KERN_ERR "%s: Out of memory whilst attempting "
@@ -2226,17 +2232,8 @@ int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,
rc = -ENOMEM;
goto out;
}
- rc = ecryptfs_decode_from_filename(decoded_name,
- &decoded_name_size,
- name, name_size);
- if (rc) {
- printk(KERN_ERR "%s: Error attempting to decode "
- "filename; rc = [%d]\n", __func__, rc);
- rc = ecryptfs_copy_filename(plaintext_name,
- plaintext_name_size,
- orig_name, orig_name_size);
- goto out_free;
- }
+ ecryptfs_decode_from_filename(decoded_name, &decoded_name_size,
+ name, name_size);
rc = ecryptfs_parse_tag_70_packet(plaintext_name,
plaintext_name_size,
&packet_size,
--
1.5.3.7


\
 
 \ /
  Last update: 2008-11-12 18:13    [from the cache]
©2003-2014 Jasper Spaans. hosted at Digital Ocean