ExternalVendorCode/tahoe-lafs
1
0
Fork 0
mirror of https://github.com/tahoe-lafs/tahoe-lafs.git synced 2025-06-24 01:28:47 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

retrieve.py: unconditionally check share-hash-tree. Fixes #1654.

Browse Source 
Add Kevan's unit test, update known_issues.rst
This commit is contained in:
Brian Warner
2012-01-12 13:35:53 -08:00
parent 2efcdc93fa
commit d10f260f36
3 changed files with 202 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

46
docs/known_issues.rst
View File

@ -14,7 +14,7 @@ want to read `the "historical known issues" document`_.
.. _the "historical known issues" document: historical/historical_known_issues.txt
Known Issues in Tahoe-LAFS v1.9.0, released 31-Oct-2011
Known Issues in Tahoe-LAFS v1.9.1, released 12-Jan-2012
=======================================================
* `Unauthorized access by JavaScript in unrelated files`_
@ -248,6 +248,50 @@ time are likely to be related even if they are not linked in the directory
structure. Also, users that access the same files may be related to each other.
----
Known Issues in Tahoe-LAFS v1.9.0, released 31-Oct-2011
=======================================================
Integrity Failure during Mutable Downloads
------------------------------------------
Under certain circumstances, the integrity-verification code of the mutable
downloader could be bypassed. Clients who receive carefully crafted shares
(from attackers) will emit incorrect file contents, and the usual
share-corruption errors would not be raised. This only affects mutable files
(not immutable), and only affects downloads that use doctored shares. It is
not persistent: the threat is resolved once you upgrade your client to a
version without the bug. However, read-modify-write operations (such as
directory manipulations) performed by vulnerable clients could cause the
attacker's modifications to be written back out to the mutable file, making
the corruption permanent.
The attacker's ability to manipulate the file contents is limited. They can
modify FEC-encoded ciphertext in all but one share. This gives them the
ability to blindly flip bits in roughly 2/3rds of the file (for the default
k=3 encoding parameter). Confidentiality remains intact, unless the attacker
can deduce the file's contents by observing your reactions to corrupted
downloads.
This bug was introduced in 1.9.0, as part of the MDMF-capable downloader, and
affects both SDMF and MDMF files. It was not present in 1.8.3.
*how to manage it*
There are three options:
* Upgrade to 1.9.1, which fixes the bug
* Downgrade to 1.8.3, which does not contain the bug
* If using 1.9.0, do not trust the contents of mutable files (whether SDMF or
MDMF) that the 1.9.0 client emits, and do not modify directories (which
could write the corrupted data back into place, making the damage
persistent)
.. _#1654: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1654
----
Known Issues in Tahoe-LAFS v1.8.2, released 30-Jan-2011