>From 728090ba1413eef2b0fa2b727a337ebf9078c86d Mon Sep 17 00:00:00 2001 From: Michael Orlitzky Date: Thu, 4 Jan 2018 11:38:21 -0500 Subject: [PATCH] doc: warn about following symlinks recursively in chown/chgrp In both chown and chgrp (which shares its code with chown), operating on symlinks recursively has a window of vulnerability where the destination user or group can change the target of the operation. Warn about combining the --dereference, --recursive, and -L flags. * doc/coreutils.texi (warnOptDerefWithRec): Add macro. (node chown invocation): Add it to --dereference and -L. (node chgrp invocation): Likewise. --- doc/coreutils.texi | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/doc/coreutils.texi b/doc/coreutils.texi index 6bb9f0906..9f5f95b69 100644 --- a/doc/coreutils.texi +++ b/doc/coreutils.texi @@ -1428,6 +1428,19 @@ a command line argument is a symbolic link to a directory, traverse it. In a recursive traversal, traverse every symbolic link to a directory that is encountered. @end macro + +@c Append the following warning to -L where appropriate (e.g. chown). +@macro warnOptDerefWithRec + +Combining this dereferencing option with the @option{--recursive} option +may create a security risk: +During the traversal of the directory tree, an attacker may be able to +introduce a symlink to an arbitrary target; when the tool reaches that, +the operation will be performed on the target of that symlink, +possibly allowing the attacker to escalate privileges. + +@end macro + @choptL @macro choptP @@ -10995,6 +11008,7 @@ chown -h -R --from=OLDUSER NEWUSER / @findex lchown Do not act on symbolic links themselves but rather on what they point to. This is the default when not operating recursively. +@warnOptDerefWithRec @item -h @itemx --no-dereference @@ -11051,6 +11065,7 @@ Recursively change ownership of directories and their contents. @xref{Traversing symlinks}. @choptL +@warnOptDerefWithRec @xref{Traversing symlinks}. @choptP @@ -11125,6 +11140,7 @@ changed. @findex lchown Do not act on symbolic links themselves but rather on what they point to. This is the default when not operating recursively. +@warnOptDerefWithRec @item -h @itemx --no-dereference @@ -11180,6 +11196,7 @@ Recursively change the group ownership of directories and their contents. @xref{Traversing symlinks}. @choptL +@warnOptDerefWithRec @xref{Traversing symlinks}. @choptP -- 2.15.1