[PATCH] xfs_metadump: obfuscate remote symlinks on CRC filesystems

[PATCH] xfs_metadump: obfuscate remote symlinks on CRC filesystems

[Eric Sandeen]

On CRC filesystems, the symlink block starts with a header,
which contains magic, "XLSM"

The code happens to "work" today w/o corrupting anything,
because it seems "XSLM" as a string, decides it's too short
to obfuscate, and leaves it alone.

But the real symlink target is untouched.  Fix that by moving
the pointer to the string we want to obfuscate by the size
of the header, and shorten the length to obfuscate accordingly.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

diff --git a/db/metadump.c b/db/metadump.c
index a599571..80a41cd 100644
--- a/db/metadump.c
+++ b/db/metadump.c
@@ -1239,8 +1239,12 @@ static void
 obfuscate_symlink_block(
 	char			*block)
 {
-	/* XXX: need to handle CRC headers */
-	obfuscate_path_components(block, mp->m_sb.sb_blocksize);
+	if (xfs_sb_version_hascrc(&(mp)->m_sb))
+		block += sizeof(struct xfs_dsymlink_hdr);
+
+	obfuscate_path_components(block,
+				  XFS_SYMLINK_BUF_SPACE(mp,
+					mp->m_sb.sb_blocksize));
 }
 
 #define MAX_REMOTE_VALS		4095

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Re: [PATCH] xfs_metadump: obfuscate remote symlinks on CRC filesystems

[Christoph Hellwig]

On Fri, Jun 19, 2015 at 03:30:32PM -0500, Eric Sandeen wrote:
> On CRC filesystems, the symlink block starts with a header,
> which contains magic, "XLSM"
> 
> The code happens to "work" today w/o corrupting anything,
> because it seems "XSLM" as a string, decides it's too short
> to obfuscate, and leaves it alone.
> 
> But the real symlink target is untouched.  Fix that by moving
> the pointer to the string we want to obfuscate by the size
> of the header, and shorten the length to obfuscate accordingly.

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Any chance to get a test for this into xfstests?

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Re: [PATCH] xfs_metadump: obfuscate remote symlinks on CRC filesystems

[Eric Sandeen]

On 6/21/15 4:14 AM, Christoph Hellwig wrote:
> On Fri, Jun 19, 2015 at 03:30:32PM -0500, Eric Sandeen wrote:
>> On CRC filesystems, the symlink block starts with a header,
>> which contains magic, "XLSM"
>>
>> The code happens to "work" today w/o corrupting anything,
>> because it seems "XSLM" as a string, decides it's too short
>> to obfuscate, and leaves it alone.
>>
>> But the real symlink target is untouched.  Fix that by moving
>> the pointer to the string we want to obfuscate by the size
>> of the header, and shorten the length to obfuscate accordingly.
> 
> Looks good,
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> Any chance to get a test for this into xfstests?

I have a larger metadump testcase brewing, it'd cover this too.

Thanks,
-Eric

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