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Message-ID: <20241107000819.z6Ygg103@steffen%sdaoden.eu>
Date: Thu, 07 Nov 2024 01:08:19 +0100
From: Steffen Nurpmeso <steffen@...oden.eu>
To: oss-security@...ts.openwall.com
Subject: Re: shell wildcard expansion (un)safety
David A. Wheeler wrote in
<F60236E0-F65A-4441-9E62-64EE55016B2C@...eeler.com>:
|> On Nov 5, 2024, at 11:12 PM, Solar Designer <solar@...nwall.com> wrote:
|> Alexander Hu, CC'ed here, sent a message titled "shell expansion bug" to
|> the distros list and a few other distro security contacts and shell
|> maintainers. The message described known and correct behavior (not a
|> bug), even if unexpected by some and risky. ...
|
|> Since this issue and other related ones were known for decades,
|> getopt(3) and getopt_long(3), which are used by many programs, will stop
|> processing options upon seeing a plain "--" argument.
|
|However, many programs do *not* use getopt or getopt_long to process \
|arguments.
|Many programs support "--", but "not* all do,so using "--" as the sole \
|countermeasure
|requires careful review of every command's documentation.
|
|I urge always using "./" to prefix wildcards if the first character \
|is a wildcard,
|e.g., "./*.pdf", because this ALWAYS works.
|
|> ... over the years we gained things like ...
|>
|> find . -mindepth 1 -maxdepth 1 -type f -print0 | xargs -0 grep text --
|
|The "-print0" and "-0" options have been widely implemented, but
|POSIX 2024 finally formally adds them. So I urge using them where they
|make sense, as they counter embedded linefeed characters in filenames.
To add that the POSIX core developers mention (APPLICATION USAGE):
It should be noted that using find with −print0 to pipe input to
xargs −r0 is less safe than using find with −exec because if
find −print0 is terminated after it has written a partial
pathname, the partial pathname may be processed as if it was
a complete pathname.
...
--steffen
|
|Der Kragenbaer, The moon bear,
|der holt sich munter he cheerfully and one by one
|einen nach dem anderen runter wa.ks himself off
|(By Robert Gernhardt)
|
|And in Fall, feel "The Dropbear Bard"s ball(s).
|
|The banded bear
|without a care,
|Banged on himself fore'er and e'er
|
|Farewell, dear collar bear
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