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docs: known_issues.txt: my version of #615, remove "issue numbers", edits, move tahoe-1.1.0 issues to historical

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Zooko O'Whielacronx 2009-02-12 22:16:21 -07:00
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143
docs/historical/historical_known_issues.txt
View File

@ -10,11 +10,114 @@ Tahoe-LAFS can be found at:
http://allmydata.org/source/tahoe/trunk/docs/known_issues.txt http://allmydata.org/source/tahoe/trunk/docs/known_issues.txt
== issues in Tahoe v1.1.0, released 2008-06-11 ==
(Tahoe v1.1.0 was superceded by v1.2.0 which was released 2008-07-21,
and then by v1.3.0 which was released 2009-02-13.)
=== more than one file can match an immutable file cap ===
In Tahoe v1.0 and v1.1, a flaw in the cryptographic integrity check
makes it possible for the original uploader of an immutable file to
produce more than one immutable file matching the same capability, so
that different downloads using the same capability could result in
different files. This flaw can be exploited only by the original
uploader of an immutable file, which means that it is not a severe
vulnerability: you can still rely on the integrity check to make sure
that the file you download with a given capability is a file that the
original uploader intended. The only issue is that you can't assume
that every time you use the same capability to download a file you'll
get the same file.
==== how to manage it ====
This was fixed in Tahoe v1.2.0, released 2008-07-21, under ticket
#491. Upgrade to that release of Tahoe and then you can rely on the
property that there is only one file that you can download using a
given capability. If you are still using Tahoe v1.0 or v1.1, then
remember that the original uploader could produce multiple files that
match the same capability, so for example if someone gives you a
capability, and you use it to download a file, and you give that
capability to your friend, and he uses it to download a file, you and
your friend could get different files.
=== server out of space when writing mutable file ===
If a v1.0 or v1.1 storage server runs out of disk space or is
otherwise unable to write to its local filesystem, then problems can
ensue. For immutable files, this will not lead to any problem (the
attempt to upload that share to that server will fail, the partially
uploaded share will be deleted from the storage server's "incoming
shares" directory, and the client will move on to using another
storage server instead).
If the write was an attempt to modify an existing mutable file,
however, a problem will result: when the attempt to write the new
share fails (e.g. due to insufficient disk space), then it will be
aborted and the old share will be left in place. If enough such old
shares are left, then a subsequent read may get those old shares and
see the file in its earlier state, which is a "rollback" failure.
With the default parameters (3-of-10), six old shares will be enough
to potentially lead to a rollback failure.
==== how to manage it ====
Make sure your Tahoe storage servers don't run out of disk space.
This means refusing storage requests before the disk fills up. There
are a couple of ways to do that with v1.1.
First, there is a configuration option named "sizelimit" which will
cause the storage server to do a "du" style recursive examination of
its directories at startup, and then if the sum of the size of files
found therein is greater than the "sizelimit" number, it will reject
requests by clients to write new immutable shares.
However, that can take a long time (something on the order of a minute
of examination of the filesystem for each 10 GB of data stored in the
Tahoe server), and the Tahoe server will be unavailable to clients
during that time.
Another option is to set the "readonly_storage" configuration option
on the storage server before startup. This will cause the storage
server to reject all requests to upload new immutable shares.
Note that neither of these configurations affect mutable shares: even
if sizelimit is configured and the storage server currently has
greater space used than allowed, or even if readonly_storage is
configured, servers will continue to accept new mutable shares and
will continue to accept requests to overwrite existing mutable shares.
Mutable files are typically used only for directories, and are usually
much smaller than immutable files, so if you use one of these
configurations to stop the influx of immutable files while there is
still sufficient disk space to receive an influx of (much smaller)
mutable files, you may be able to avoid the potential for "rollback"
failure.
A future version of Tahoe will include a fix for this issue. Here is
[http://allmydata.org/pipermail/tahoe-dev/2008-May/000630.html the
mailing list discussion] about how that future version will work.
=== pyOpenSSL/Twisted defect causes false alarms in tests ===
The combination of Twisted v8.0 or Twisted v8.1 with pyOpenSSL v0.7
causes the Tahoe v1.1 unit tests to fail, even though the behavior of
Tahoe itself which is being tested is correct.
==== how to manage it ====
If you are using Twisted v8.0 or Twisted v8.1 and pyOpenSSL v0.7, then
please ignore ERROR "Reactor was unclean" in test_system and
test_introducer. Upgrading to a newer version of Twisted or pyOpenSSL
will cause those false alarms to stop happening (as will downgrading
to an older version of either of those packages).
== issues in Tahoe v1.0.0, released 2008-03-25 == == issues in Tahoe v1.0.0, released 2008-03-25 ==
(Tahoe v1.0 was superceded by v1.1 which was released 2008-06-11.) (Tahoe v1.0 was superceded by v1.1 which was released 2008-06-11.)
=== issue 6: server out of space when writing mutable file === === server out of space when writing mutable file ===
In addition to the problems caused by insufficient disk space In addition to the problems caused by insufficient disk space
described above, v1.0 clients which are writing mutable files when the described above, v1.0 clients which are writing mutable files when the
@ -28,7 +131,7 @@ write to their local filesystem (including that there is space
available) as described in "issue 1" above. available) as described in "issue 1" above.
=== issue 5: server out of space when writing immutable file === === server out of space when writing immutable file ===
Tahoe v1.0 clients are using v1.0 servers which are unable to write to Tahoe v1.0 clients are using v1.0 servers which are unable to write to
their filesystem during an immutable upload will correctly detect the their filesystem during an immutable upload will correctly detect the
@ -45,7 +148,7 @@ always able to write to their local filesystem (including that there
is space available) as described in "issue 1" above. is space available) as described in "issue 1" above.
=== issue 4: large directories or mutable files of certain sizes === === large directories or mutable files of certain sizes ===
If a client attempts to upload a large mutable file with a size If a client attempts to upload a large mutable file with a size
greater than about 3,139,000 and less than or equal to 3,500,000 bytes greater than about 3,139,000 and less than or equal to 3,500,000 bytes
@ -72,7 +175,7 @@ to v1.1 but the client is still v1.0 then the client will still suffer
this failure.) this failure.)
=== issue 3: uploading files greater than 12 GiB === === uploading files greater than 12 GiB ===
If a Tahoe v1.0 client uploads a file greater than 12 GiB in size, the file will If a Tahoe v1.0 client uploads a file greater than 12 GiB in size, the file will
be silently corrupted so that it is not retrievable, but the client will think be silently corrupted so that it is not retrievable, but the client will think
@ -87,7 +190,7 @@ Tahoe storage grid. Tahoe v1.1 clients will refuse to upload files larger than
limitation so that larger files can be uploaded. limitation so that larger files can be uploaded.
=== issue 2: pycryptopp defect resulting in data corruption === === pycryptopp defect resulting in data corruption ===
Versions of pycryptopp earlier than pycryptopp-0.5.0 had a defect Versions of pycryptopp earlier than pycryptopp-0.5.0 had a defect
which, when compiled with some compilers, would cause AES-256 which, when compiled with some compilers, would cause AES-256
@ -104,33 +207,3 @@ Tahoe v1.0 {{{misc/dependencies}}} directory, cd into the resulting
{{{pycryptopp-0.3.0}}} directory, and execute {{{python ./setup.py {{{pycryptopp-0.3.0}}} directory, and execute {{{python ./setup.py
test}}}. If the tests pass, then your compiler does not trigger this test}}}. If the tests pass, then your compiler does not trigger this
failure. failure.
=== issue 1: potential disclosure of a file through embedded
hyperlinks or JavaScript in that file ===
If there is a file stored on a Tahoe storage grid, and that file gets
downloaded and displayed in a web browser, then JavaScript or
hyperlinks within that file can leak the capability to that file to a
third party, which means that third party gets access to the file.
If there is JavaScript in the file, then it could deliberately leak
the capability to the file out to some remote listener.
If there are hyperlinks in the file, and they get followed, then
whichever server they point to receives the capability to the
file. Note that IMG tags are typically followed automatically by web
browsers, so being careful which hyperlinks you click on is not
sufficient to prevent this from happening.
==== how to manage it ====
For future versions of Tahoe, we are considering ways to close off
this leakage of authority while preserving ease of use -- the
discussion of this issue is ticket #127.
For the present, a good work-around is that if you want to store and
view a file on Tahoe and you want that file to remain private, then
remove from that file any hyperlinks pointing to other people's
servers and remove any JavaScript unless you are sure that the
JavaScript is not written to maliciously leak access.

141
docs/known_issues.txt
View File

@ -10,29 +10,32 @@ Tahoe-LAFS can be found at
http://allmydata.org/source/tahoe/trunk/docs/historical/historical_known_issues.txt http://allmydata.org/source/tahoe/trunk/docs/historical/historical_known_issues.txt
== issues in Tahoe v1.3.0, not yet released == == issues in Tahoe v1.3.0, released 2009-02-13 ==
=== unauthorized access by JavaScript in other tabs/frames ===
If you use a web browser to view a javascript-bearing HTML document that is === potential unauthorized access by JavaScript in unrelated files ===
served from a Tahoe node, then that javascript program can learn the access
caps for any other file or directory, served by the same Tahoe node, that you
are currently viewing in other tabs or frames. This is a consequence of the
common "Same Origin Policy" as applied to javascript and inter-frame access,
in which the browser mistakenly believes that two documents retrieved from
the same server should have access to each others DOM state. Note that some
browsers are quite enthusiastic about interpreting <script> tags inside
viewed files, even ones not marked as HTML.
The current recommended workaround is to close all Tahoe-served tabs and If you view a file stored in Tahoe through a web user interface,
frames before opening a Tahoe-served javascript-bearing HTML file. JavaScript embedded in that file might be able to access other files or
directories stored in Tahoe which you view through the same web user
interface. Such a script would be able to send the contents of those
other files or directories to the author of the script, and if you have
the ability to modify the contents of those files or directories, then
that script could modify or delete those files or directories.
Please see ticket #615 for more details: ==== how to manage it ====
http://allmydata.org/trac/tahoe/ticket/615
== issues in Tahoe v1.2.0, released 2008-06-21 == For future versions of Tahoe, we are considering ways to close off
this leakage of authority while preserving ease of use -- the
discussion of this issue is ticket #615.
=== issue 1: potential disclosure of a file through embedded For the present, either do not view files stored in Tahoe through a web
user interface, or turn off JavaScript in your web browser before doing
so, or limit your viewing to files which you know don't contain
malicious JavaScript.
=== potential disclosure of file through embedded
hyperlinks or JavaScript in that file === hyperlinks or JavaScript in that file ===
If there is a file stored on a Tahoe storage grid, and that file gets If there is a file stored on a Tahoe storage grid, and that file gets
@ -62,7 +65,7 @@ servers and remove any JavaScript unless you are sure that the
JavaScript is not written to maliciously leak access. JavaScript is not written to maliciously leak access.
=== issue 10: command-line arguments are leaked to other processes === === command-line arguments are leaked to other local users ===
Remember that command-line arguments are visible to other users Remember that command-line arguments are visible to other users
(through the 'ps' command, or the windows Process Explorer tool), so (through the 'ps' command, or the windows Process Explorer tool), so
@ -84,105 +87,3 @@ vulnerability becomes less significant: they can still see your filenames and
other arguments you type there, but not the caps that Tahoe uses to permit other arguments you type there, but not the caps that Tahoe uses to permit
access to your files and directories. In Tahoe v1.3.0, there is a new access to your files and directories. In Tahoe v1.3.0, there is a new
"tahoe create-aliase" command that does this for you. "tahoe create-aliase" command that does this for you.
== issues in Tahoe v1.1.0, released 2008-06-11 ==
=== issue 9: more than one file can match an immutable file cap ===
In Tahoe v1.0 and v1.1, a flaw in the cryptographic integrity check
makes it possible for the original uploader of an immutable file to
produce more than one immutable file matching the same capability, so
that different downloads using the same capability could result in
different files. This flaw can be exploited only by the original
uploader of an immutable file, which means that it is not a severe
vulnerability: you can still rely on the integrity check to make sure
that the file you download with a given capability is a file that the
original uploader intended. The only issue is that you can't assume
that every time you use the same capability to download a file you'll
get the same file.
==== how to manage it ====
This was fixed in Tahoe v1.2.0, released 2008-07-21, under ticket
#491. Upgrade to that release of Tahoe and then you can rely on the
property that there is only one file that you can download using a
given capability. If you are still using Tahoe v1.0 or v1.1, then
remember that the original uploader could produce multiple files that
match the same capability, so for example if someone gives you a
capability, and you use it to download a file, and you give that
capability to your friend, and he uses it to download a file, you and
your friend could get different files.
=== issue 8: server out of space when writing mutable file ===
If a v1.0 or v1.1 storage server runs out of disk space or is
otherwise unable to write to its local filesystem, then problems can
ensue. For immutable files, this will not lead to any problem (the
attempt to upload that share to that server will fail, the partially
uploaded share will be deleted from the storage server's "incoming
shares" directory, and the client will move on to using another
storage server instead).
If the write was an attempt to modify an existing mutable file,
however, a problem will result: when the attempt to write the new
share fails (e.g. due to insufficient disk space), then it will be
aborted and the old share will be left in place. If enough such old
shares are left, then a subsequent read may get those old shares and
see the file in its earlier state, which is a "rollback" failure.
With the default parameters (3-of-10), six old shares will be enough
to potentially lead to a rollback failure.
==== how to manage it ====
Make sure your Tahoe storage servers don't run out of disk space.
This means refusing storage requests before the disk fills up. There
are a couple of ways to do that with v1.1.
First, there is a configuration option named "sizelimit" which will
cause the storage server to do a "du" style recursive examination of
its directories at startup, and then if the sum of the size of files
found therein is greater than the "sizelimit" number, it will reject
requests by clients to write new immutable shares.
However, that can take a long time (something on the order of a minute
of examination of the filesystem for each 10 GB of data stored in the
Tahoe server), and the Tahoe server will be unavailable to clients
during that time.
Another option is to set the "readonly_storage" configuration option
on the storage server before startup. This will cause the storage
server to reject all requests to upload new immutable shares.
Note that neither of these configurations affect mutable shares: even
if sizelimit is configured and the storage server currently has
greater space used than allowed, or even if readonly_storage is
configured, servers will continue to accept new mutable shares and
will continue to accept requests to overwrite existing mutable shares.
Mutable files are typically used only for directories, and are usually
much smaller than immutable files, so if you use one of these
configurations to stop the influx of immutable files while there is
still sufficient disk space to receive an influx of (much smaller)
mutable files, you may be able to avoid the potential for "rollback"
failure.
A future version of Tahoe will include a fix for this issue. Here is
[http://allmydata.org/pipermail/tahoe-dev/2008-May/000630.html the
mailing list discussion] about how that future version will work.
=== issue 7: pyOpenSSL/Twisted defect causes false alarms in tests ===
The combination of Twisted v8.0 or Twisted v8.1 with pyOpenSSL v0.7
causes the Tahoe v1.1 unit tests to fail, even though the behavior of
Tahoe itself which is being tested is correct.
==== how to manage it ====
If you are using Twisted v8.0 or Twisted v8.1 and pyOpenSSL v0.7, then
please ignore ERROR "Reactor was unclean" in test_system and
test_introducer. Upgrading to a newer version of Twisted or pyOpenSSL
will cause those false alarms to stop happening (as will downgrading
to an older version of either of those packages).