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We need to be careful to follow proper quoting rules. For example, if an
argument contains spaces, we have to quote them. Double-quotes need to
be escaped. Backslashes need to be escaped, but only if they are
followed by a double-quote character.
We need to be _extra_ careful to consider the case where an argument
ends in a backslash _and_ needs to be quoted: in this case, we append a
double-quote character, i.e. the backslash now has to be escaped!
The current code, however, fails to recognize that, and therefore can
turn an argument that ends in a single backslash into a quoted argument
that now ends in an escaped double-quote character. This allows
subsequent command-line parameters to be split and part of them being
mistaken for command-line options, e.g. through a maliciously-crafted
submodule URL during a recursive clone.
Technically, we would not need to quote _all_ arguments which end in a
backslash _unless_ the argument needs to be quoted anyway. For example,
`test\` would not need to be quoted, while `test \` would need to be.
To keep the code simple, however, and therefore easier to reason about
and ensure its correctness, we now _always_ quote an argument that ends
in a backslash.
This addresses CVE-2019-1350.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
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The previous commit taught the submodule code to invoke our
"git clone $url $path" with a "--" separator so that we
aren't confused by urls or paths that start with dashes.
However, that's just one code path. It's not clear if there
are others, and it would be an easy mistake to add one in
the future. Moreover, even with the fix in the previous
commit, it's quite hard to actually do anything useful with
such an entry. Any url starting with a dash must fall into
one of three categories:
- it's meant as a file url, like "-path". But then any
clone is not going to have the matching path, since it's
by definition relative inside the newly created clone. If
you spell it as "./-path", the submodule code sees the
"/" and translates this to an absolute path, so it at
least works (assuming the receiver has the same
filesystem layout as you). But that trick does not apply
for a bare "-path".
- it's meant as an ssh url, like "-host:path". But this
already doesn't work, as we explicitly disallow ssh
hostnames that begin with a dash (to avoid option
injection against ssh).
- it's a remote-helper scheme, like "-scheme::data". This
_could_ work if the receiver bends over backwards and
creates a funny-named helper like "git-remote--scheme".
But normally there would not be any helper that matches.
Since such a url does not work today and is not likely to do
anything useful in the future, let's simply disallow them
entirely. That protects the existing "git clone" path (in a
belt-and-suspenders way), along with any others that might
exist.
Our tests cover two cases:
1. A file url with "./" continues to work, showing that
there's an escape hatch for people with truly silly
repo names.
2. A url starting with "-" is rejected.
Note that we expect case (2) to fail, but it would have done
so even without this commit, for the reasons given above.
So instead of just expecting failure, let's also check for
the magic word "ignoring" on stderr. That lets us know that
we failed for the right reason.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Johannes Schindelin
Jeff King