Date: Sat, 18 Apr 2015 18:27:48 +0200 From: Harald Becker <ralda@....de> To: musl@...ts.openwall.com CC: Matt Johnston <matt@....asn.au> Subject: Re: Re: Security advisory for musl libc - stack-based buffer overflow in ipv6 literal parsing [CVE-2015-1817] Hi ! @Rich: I still get DNS error (Mozilla Thunderbird) for dalias@...c.org, when tying to send mail :( On 18.04.2015 17:58, Rich Felker wrote: > On Sat, Apr 18, 2015 at 05:49:51PM +0200, Harald Becker wrote: >> On 18.04.2015 17:25, Rich Felker wrote: >>>> The server hostkey will remain in process memory since it's >>>> required for rekeying - not as bad as root code execution >>>> though. >>> >>> Ugly. I don't see how this can be solved without a more advanced >>> privsep model. I agree it's lower-severity though. >> >> IMO you may put the host keys in a file readable (not writable) >> with a dropbear group, and only using that group for dropbear (no >> other users or programs using that group). So you may read the keys >> even if not root, if you add this dropbear group to setgroups (not >> setgid) before dropping root privileges. > > The key is already in memory. As far as I understand it, the question was, *not to have* the key hanging around in memory, but still have access without requirement to keep root privileges. My suggestion is to solve this, with a very simple and easy to implement solution. I consider it a slight increased security, as the dropbear process can drop root privileges (and has to do so), but still has access to the host keys. > A design like the above would not significantly improve security > (except for heartbleed type issues); it would be just like the > situation now where the key is already in memory. ACK, as told it's intention is a simple solution to give dropbear access to the host keys without letting them hang in memory all the time. > To make it more secure, the session process would not have any access > to the key and would have to communicate with an existing privileged > process to rekey. ACK, much better, but this would need major restructuring, wouldn't it? So consider my suggestion a simpler to implement solution, in between having full root privileges or hanging keys in memory, and an external process to do the rekey steps (in addition: with the possibility to let that process use the dropbear group and not root to access keys - even better than let that process hang around as root) Harald
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