From: Harald Becker <ralda@gmx.de>
To: musl@lists.openwall.com
Cc: Matt Johnston <matt@ucc.asn.au>
Subject: Re: Re: Security advisory for musl libc - stack-based buffer overflow in ipv6 literal parsing [CVE-2015-1817]
Date: Sat, 18 Apr 2015 19:07:31 +0200 [thread overview]
Message-ID: <55328F53.1070705@gmx.de> (raw)
In-Reply-To: <20150418163702.GI6817@brightrain.aerifal.cx>
On 18.04.2015 18:37, Rich Felker wrote:
>> @Rich: I still get DNS error (Mozilla Thunderbird) for
>> dalias@libc.org, when tying to send mail :(
>
> Odd. I just verified that Google's 8.8.8.8 resolves it right, so I
> don't know what's wrong, but it seems to be on your end. Let me know
> if you find anything that looks like a problem on my side.
AFAIK, you use a CNAME as MX, which is resolved on some, but not all
systems / programs. You need to add an absolute IP address for your MX,
not a CNAME, to be accessible for all.
A-record lookup is ok (resolved recursive), but MX lookup fails (doesn't
do recursive lookup everywhere).
>> On 18.04.2015 17:58, Rich Felker wrote:
> Well anything that gets code execution in the dropbear session process
> would be able to steal the key still. The only added protection you'd
> get is is against heartbleed-type attacks (arbitrary memory read but
> no code exeution).
ACK, ... isn't that bad, to protect against that kind of key steeling,
with a very simple solution, and no need to further code restructuring?
IMO it is a quick intermediate solution, until someone may be able to
restructure key creation code, still giving the possibility to let
dropbear drop root privileges completely (except pty/utmp question).
>> 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)
>
> If this external process is setuid/setgid, I consider that a much
> bigger vuln.
Just to mention: My statement 'separate process' doesn't included or
intended a separate suid/sgid program.
> It would have to somehow verify that it's being invoked
> by a valid dropbear session process and not some other caller that
> just wants to use it to steal keys/forge key negotiations, and you
> have all the usual issues with setuid programs having to be defensive
> about the state they inherit when invoked.
I didn't think of an exec to a separate program, but just fork and let a
process for key management run in the back. So a bit simpler to verify
authentication of caller, but still somehow required ... or what else
did you suggest?
> If on the other hand the session process just kept gid=dropbear to
> open and reload the key, it wouldn't be so bad.
That's it, the key creator part doesn't need root privileges for it's
operation either. That is just a combination of the two approaches.
Harald
next prev parent reply other threads:[~2015-04-18 17:07 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-17 13:10 Matt Johnston
2015-04-17 17:23 ` Rich Felker
2015-04-17 18:03 ` Rich Felker
2015-04-17 18:09 ` Solar Designer
2015-04-18 13:32 ` Matt Johnston
2015-04-18 15:25 ` Rich Felker
2015-04-18 15:49 ` Harald Becker
2015-04-18 15:58 ` Rich Felker
2015-04-18 16:27 ` Harald Becker
2015-04-18 16:37 ` Rich Felker
2015-04-18 17:07 ` Harald Becker [this message]
2015-04-18 18:27 ` Laurent Bercot
2015-04-18 18:47 ` Harald Becker
2015-04-18 18:13 ` Harald Becker
2015-04-18 19:56 ` Rich Felker
2015-04-18 21:02 ` Laurent Bercot
2015-04-19 3:44 ` Rich Felker
2015-04-20 10:17 ` Harald Becker
2015-04-20 11:20 ` Kurt H Maier
2015-04-20 11:35 ` Harald Becker
2015-04-20 11:50 ` Harald Becker
2015-04-20 14:14 ` Kurt H Maier
2015-04-20 14:21 ` Harald Becker
2015-04-18 18:25 ` Harald Becker
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=55328F53.1070705@gmx.de \
--to=ralda@gmx.de \
--cc=matt@ucc.asn.au \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).