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On 11/02/2014 01:23, Walter Dnes wrote: |
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> On Tue, Feb 11, 2014 at 12:28:43AM +0000, Kerin Millar wrote |
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>> On 10/02/2014 23:57, Walter Dnes wrote: |
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>>> |
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>>> What's the point, if you still have to run as root (or su or sudo) for |
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>>> the emerge update process? |
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>> |
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>> It's the principle of least privilege. Is there any specific reason for |
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>> portage to fork and exec rsync as root? Is rsync sandboxed? Should rsync |
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>> have unfettered read/write access to all mounted filesystems? Can it be |
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>> guaranteed that rsync hasn't been compromised? Can it be guaranteed that |
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>> PORTAGE_RSYNC_OPTS will contain safe options at all times? |
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>> |
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>> The answer to all of these questions is "no". Basically, the combination |
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>> of usersync and non-root ownership of PORTDIR hardens the process in a |
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>> sensible way while conferring no disadvantage. |
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> |
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> If /usr/portage is owned by portage:portage, then wouldn't a user |
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> (member of portage) be able to do mischief by tweaking ebuilds? E.g. |
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> modify an ebuild to point to a tarball located on a usb stick, at |
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> http://127.0.0.1/media/sdc1/my_tarball.tgz. This would allow a local |
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> user to supply code that gets built and then installed in /usr/bin, or |
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> /sbin, etc. |
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Yes, but only if the group write bit is set throughout PORTDIR. By |
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default, rsync - as invoked by portage - preserves the permission bits |
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from the remote and the files stored by the mirrors do not have this bit |
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set. |
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What I have described elsewhere is a method for ensuring that the group |
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write bit is set. In that case, your concern is justified; you would |
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definitely not want to grant membership of the portage group to anyone |
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that you couldn't trust in this context. |
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--Kerin |
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