Age | Commit message (Collapse) | Author |
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If we have a file on disk and the hashes are the same in the new Release
file and the old one we have on disk we know that if we ask the server
for the file, we will at best get an IMS hit – at worse the server
doesn't support this and sends us the (unchanged) file and we have to
run all our checks on it again for nothing. So, we can save ourselves
(and the servers) some unneeded requests if we figure this out on our
own.
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If we e.g. fail on hash verification for Packages.xz its highly unlikely
that it will be any better with Packages.gz, so we just waste download
bandwidth and time. It also causes us always to fallback to the
uncompressed Packages file for which the error will finally be reported,
which in turn confuses users as the file usually doesn't exist on the
mirrors, so a bug in apt is suspected for even trying it…
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Valid-Until protects us from long-living downgrade attacks, but not all
repositories have it and an attacker could still use older but still
valid files to downgrade us. While this makes it sounds like a security
improvement now, its a bit theoretical at best as an attacker with
capabilities to pull this off could just as well always keep us days
(but in the valid period) behind and always knows which state we have,
as we tell him with the If-Modified-Since header. This is also why this
is 'silently' ignored and treated as an IMSHit rather than screamed at
the user as this can at best be an annoyance for attackers.
An error here would 'regularily' be encountered by users by out-of-sync
mirrors serving a single run (e.g. load balancer) or in two consecutive
runs on the other hand, so it would just help teaching people ignore it.
That said, most of the code churn is caused by enforcing this additional
requirement. Crisscross from InRelease to Release.gpg is e.g. very
unlikely in practice, but if we would ignore it an attacker could
sidestep it this way.
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Not all servers we are talking to support If-Modified-Since and some are
not even sending Last-Modified for us, so in an effort to detect such
hits we run a hashsum check on the 'old' compared to the 'new' file, we
got the hashes for the 'new' already for "free" from the methods anyway
and hence just need to calculated the old ones.
This allows us to detect hits even with unsupported servers, which in
turn means we benefit from all the new hit behavior also here.
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We use test{success,failure} now all over the place in the framework, so
its only consequencial to do this in the situations in which we test for
a specific output as well.
Git-Dch: Ignore
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Adds a new testwarning which tests for zero exit and the presents of a
warning in the output, failing if either is not the case or if an error
is found, too. This allows us to change testsuccess to accept only
totally successful executions (= without warnings) which should help
finding regressions.
Git-Dch: Ignore
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Git-Dch: Ignore
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I am pretty sure I did that before committing broken stuff…
Git-Dch: Ignore
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consistently using Item::Failed in all specializec classes helps setting
up some information bits otherwise unset, so some errors had an empty
reason as an error. Ign is upgraded to display the error message we
ignored to further help in understanding what happens.
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The configuration key Acquire::AllowInsecureRepositories controls if
apt allows loading of unsigned repositories at all.
The configuration Acquire::AllowDowngradeToInsecureRepositories
controls if a signed repository can ever become unsigned. This
should really never be needed but we provide it to avoid having
to mess around in /var/lib/apt/lists if there is a use-case for
this (which I can't think of right now).
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