git-annex/doc/todo/terminal_escapes_in_filenames.mdwn
Joey Hess cd544e548b
filter out control characters in error messages
giveup changed to filter out control characters. (It is too low level to
make it use StringContainingQuotedPath.)

error still does not, but it should only be used for internal errors,
where the message is not attacker-controlled.

Changed a lot of existing error to giveup when it is not strictly an
internal error.

Of course, other exceptions can still be thrown, either by code in
git-annex, or a library, that include some attacker-controlled value.
This does not guard against those.

Sponsored-by: Noam Kremen on Patreon
2023-04-10 13:50:51 -04:00

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touch $(echo -e "\e[31mfoo\e[0m")
git-annex add
git-annex whereis
That displays "foo" in red twice. Compare with behavior of git commands that
display that filename, which display it escaped.
git-annex should probably do the same, when displaying filenames that it's
working on or in messages.
`git-annex find` is an interesting case because it's expected to be
pipeable, and so should have raw filenames. Note that `find` actually
escapes such filenames when outputting to a terminal, but not a pipe.
git porcelain also accepts the escaped form of files as input, necessary for
round-tripping though. git-annex currently does not. (git plumbing doesn't
either)
While terminals mostly protect against escape sequences doing very bad
things, there are security holes in terminals still being found.
Of course, such files in git repos can also be exploited by other commands
eg `echo *`.
So this does not seem like a security hole in git-annex, but it would be
useful defense in depth against terminal security holes, and also good to
behave more like git.
--[[Joey]]
> Git.Filename.encode is implemented, and only needs to be used.
> Note that core.quotePath controls whether git quotes unicode characters
> (by default it does), so once this gets implemented, some users may want
> to set that config to false. --[[Joey]]
> Update: Most git-annex commands now quote filenames, due to work on
> ActionItem display. `git-annex find`, `git-annex info $file`,
> and everywhere filenames get
> embedded in warnings, info messages, still need to be done.
----
Also:
It's possible that keys can also contain an escape sequence, eg in the
extension of a SHA-E key. So commands like `git-annex lookupkey`
and `git-annex find` that output keys might need to handle
that, when outputting to a terminal?
Also:
`git-annex metadata` could also contain an escape sequence. So could
`git-annex config --get` and `git-annex schedule` and `git-annex wanted`
and `git-annex required` and `git-annex group`. And so could the
description of a repository. It seems that git-annex could just filter out
control characters from all of these, since they are not filenames, and
any control characters in them are surely malicious.
Also: git-annex importfeed displays urls from the feed, and should filter
out control characters. If such an url even can be parsed?
Also: git-annex initremote with autoenable may be able to cause a remote
with a malicious name to be set up?
Also: Any place that an exception is thrown with an attacker-controlled value.
`giveup` has been made to filter out control characters, but that leave
other exceptions, including ones thrown by libraries. Catch all exceptions
at top-level (of program and/or worker threads) and filter out control
characters?