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On 11/02/2014 03:23, 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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> |
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Yes, you can do that. You can also rm with gainful abandon all over the |
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place and wreak havoc like that. There are many attack vectors involving |
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user doing dumb things, and no software is ever going to deal fully with |
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user stupidity or mischief. Modifying an ebuild is no difference |
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attack-wise to putting it in a local overlay, and you can already do that. |
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What software security attempts to provide you is protection against |
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unexpected side-effects like a malformed path (eg unquoted spaces) in an |
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rm statement run as root, or bad guys out there banging on the door. |
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Once an attacker can run yoru shell, it's basically game over at that |
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point wrt security and just a matter of time. So you have a choice |
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between syncing as a regular user or syncing as root, there are pros and |
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cons to each. Experience shows that in the general case the former |
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offers more and better protection. But, if the latter really does suit |
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your specific needs, then you have the choice to do it that way. |
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You don't *have* to follow recommendations in man pages at all, but it's |
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highly recommended you be well informed when making your personal choice. |
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-- |
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Alan McKinnon |
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alan.mckinnon@×××××.com |
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