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[warner]

This is the ticket where we will track the details of a failure of assurance of integrity. For now, here is the announcement:

Dear Tahoe-LAFS Users:

Kevan Carstensen of the Tahoe-LAFS core team has discovered a security
vulnerability in Tahoe-LAFS v1.9.0 which would allow a sufficiently clever
attacker to corrupt the retrieval of mutable files or directories which are
retrieved with v1.9.0 or, in some cases, to corrupt the stored copy of
mutable files or directories which are updated with v1.9.0.

The recommended defensive action for all users is to downgrade to v1.8.3, or
to refrain from using mutable files (either SDMF or MDMF) with 1.9.0.

A FAQ about downgrading from 1.9.0 to 1.8.3, which was written before we
discovered this critical security vulnerability, is here:

https://tahoe-lafs.org/pipermail/tahoe-dev/2011-December/006905.html

The FAQ is no longer accurate about 1.9.0 being free of dangerous flaws, but
it is still accurate about 1.8.3 being free of compatibility problems.

We'll be providing a patch soon. We are still writing tests for it and
searching for other similar bugs and so on. Of course, as soon as we release
the patch, this will inform any attackers of exactly what they could do to
users of 1.9.0. Therefore, if there are any users who are especially
security-sensitive, then they should downgrade to 1.8.3 before we release the
patch, or else they should suspend their use of mutable files and directories
until we released the patch and they've applied it.

Once we are ready to publish the details of the issue we will post them to
this issue tracker ticket:

https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1654

Please feel free to contact me with any questions or concerns, using GPG
encryption. Please Cc: Brian Warner, David-Sarah Hopwood, and Kevan
Carstensen on all such email.

Regards,

Zooko Wilcox-O'Hearn, on behalf of the Tahoe-LAFS core team


GPG fingerprints:

Brian Warner <warner-tahoe@lothar.com> 967E FE06 6998 7241 1A77  DF36 D43B 4C9C 7322 5AAF
David-Sarah Hopwood <david-sarah@jacaranda.org> 3D6A 08E9 1262 3E9A 00B2  1BDC 067F 4920 98CF 2762
Kevan Carstensen <kevan@isnotajoke.com> 7E1E 99DB 97B1 DD5F 8154  5973 8E6B 2106 2425 D7AE
Zooko Wilcox-O'Hearn <zooko@zooko.com> A60B 7EE1 7164 D0C5 F137  3868 5F22 F428 242B E85F

[warner]

fixed formatting of announcement, removed pubkeys, removed signature wrapper (not verifiable here)