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cp, ln, mv, install: check for vulnerable target directories


From: Paul Eggert
Subject: cp, ln, mv, install: check for vulnerable target directories
Date: Tue, 19 Sep 2017 00:25:46 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0

For years cp and friends have been subject to a symlink attack, in that seemingly-ordinary commands like 'cp a b' can overwrite arbitrary directories that the user has access to, if b's parent directory is world-writable and is not sticky and is manipulated by a malicious user. To help ameliorate this problem, I've installed the attached patch into coreutils. Although it does not detect every instance of this problem, the goal is that its heuristic should avoid false positives while catching and reporting and refusing to act on most instances.

As this is not an upward-compatible change, I installed this patch right after a coreutils release, in the hope that we will have time to shake out any problems with it (including reverting it entirely :-) before the next release.

Attachment: 0001-copy-check-for-vulnerable-target-dirs.patch
Description: Text Data


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