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Merge pull request #7805 from ThomasWaldmann/fwd-port-tam-cve-fixes-master 

some fwd ports of the archive-TAM/CVE related code/docs
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TW 2023-09-03 20:49:50 +02:00 committed by GitHub
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29
docs/changes_1.x.rst
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@ -29,27 +29,29 @@ places. Borg now considers archives without TAM as garbage or an attack.
We are not aware of others having discovered, disclosed or exploited this vulnerability.
Below, if we speak of borg 1.2.5, we mean a borg version >= 1.2.5 **or** a
Below, if we speak of borg 1.2.6, we mean a borg version >= 1.2.6 **or** a
borg version that has the relevant security patches for this vulnerability applied
(could be also an older version in that case).
Steps you must take to upgrade a repository:
1. Upgrade all clients using this repository to borg 1.2.5.
1. Upgrade all clients using this repository to borg 1.2.6.
Note: it is not required to upgrade a server, except if the server-side borg
is also used as a client (and not just for "borg serve").
Do **not** run ``borg check`` with borg 1.2.5 before completing the upgrade steps.
Do **not** run ``borg check`` with borg > 1.2.4 before completing the upgrade steps.
2. Run ``borg info --debug <repository> 2>&1 | grep TAM | grep -i manifest``.
2. Run ``BORG_WORKAROUNDS=ignore_invalid_archive_tam borg info --debug <repo> 2>&1 | grep TAM | grep -i manifest``.
a) If you get "TAM-verified manifest", continue with 3.
b) If you get "Manifest TAM not found and not required", run
``borg upgrade --tam --force <repository>`` *on every client*.
3. Run ``borg list --format='{name} {time} tam:{tam}{NL}' <repository>``.
3. Run ``BORG_WORKAROUNDS=ignore_invalid_archive_tam borg list --format='{name} {time} tam:{tam}{NL}' <repo>``.
"tam:verified" means that the archive has a valid TAM authentication.
"tam:none" is expected as output for archives created by borg <1.0.9.
"tam:none" is also expected for archives resulting from a borg rename
or borg recreate operation (see #7791).
"tam:none" could also come from archives created by an attacker.
You should verify that "tam:none" archives are authentic and not malicious
(== have good content, have correct timestamp, can be extracted successfully).
@ -57,13 +59,15 @@ Steps you must take to upgrade a repository:
In low-risk, trusted environments, you may decide on your own risk to skip step 3
and just trust in everything being OK.
4. If there are no tam:non archives left at this point, you can skip this step.
Run ``borg upgrade --archives-tam <repository>``.
This will make sure all archives are TAM authenticated (an archive TAM will be added
for all archives still missing one).
``borg check`` would consider TAM-less archives as garbage or a potential attack.
Optionally run the same command as in step 3 to see that all archives now are "tam:verified".
4. If there are no tam:none archives left at this point, you can skip this step.
Run ``BORG_WORKAROUNDS=ignore_invalid_archive_tam borg upgrade --archives-tam <repo>``.
This will unconditionally add a correct archive TAM to all archives not having one.
``borg check`` would consider TAM-less or invalid-TAM archives as garbage or a potential attack.
To see that all archives now are "tam:verified" run: ``borg list --format='{name} {time} tam:{tam}{NL}' <repo>``
5. Please note that you should never use BORG_WORKAROUNDS=ignore_invalid_archive_tam
for normal production operations - it is only needed once to get the archives in a
repository into a good state. All archives have a valid TAM now.
Vulnerability time line:
@ -71,7 +75,8 @@ Vulnerability time line:
* 2023-06-13...: Work on fixing the issue, upgrade procedure, docs.
* 2023-06-30: CVE was assigned via Github CNA
* 2023-06-30 .. 2023-08-29: Fixed issue, code review, docs, testing.
* 2023-08-30: Released fixed version 1.2.5
* 2023-08-30: Released fixed version 1.2.5 (broken upgrade procedure for some repos)
* 2023-08-31: Released fixed version 1.2.6 (fixes upgrade procedure)
.. _hashindex_set_bug:

7
src/borg/archive.py
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@ -1999,13 +1999,17 @@ class ArchiveChecker:
# are likely looking at an archive item here, also check the TAM authentication:
try:
archive, verified, _ = self.key.unpack_and_verify_archive(data, force_tam_not_required=False)
except IntegrityError:
except IntegrityError as integrity_error:
# TAM issues - do not accept this archive!
# either somebody is trying to attack us with a fake archive data or
# we have an ancient archive made before TAM was a thing (borg < 1.0.9) **and** this repo
# was not correctly upgraded to borg 1.2.5 (see advisory at top of the changelog).
# borg can't tell the difference, so it has to assume this archive might be an attack
# and drops this archive.
name = archive.get(b"name", b"<unknown>").decode("ascii", "replace")
logger.error("Archive TAM authentication issue for archive %s: %s", name, integrity_error)
logger.error("This archive will *not* be added to the rebuilt manifest! It will be deleted.")
self.error_found = True
continue
# note: if we get here and verified is False, a TAM is not required.
archive = ArchiveItem(internal_dict=archive)
@ -2271,6 +2275,7 @@ class ArchiveChecker:
# when upgrading to borg 1.2.5, users are expected to TAM-authenticate all archives they
# trust, so there shouldn't be any without TAM.
logger.error("Archive TAM authentication issue for archive %s: %s", info.name, integrity_error)
logger.error("This archive will be *removed* from the manifest! It will be deleted.")
self.error_found = True
del self.manifest.archives[info.name]
continue