Date: Fri, 17 Apr 2015 14:03:25 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: Re: Security advisory for musl libc - stack-based buffer overflow in ipv6 literal parsing [CVE-2015-1817] On Fri, Apr 17, 2015 at 01:23:27PM -0400, Rich Felker wrote: > On Fri, Apr 17, 2015 at 09:10:08PM +0800, Matt Johnston wrote: > > Hi, > > > > I think Dropbear probably is vulnerable to CVE-2015-1817 > > post-authentication. TCP forwarding requests will call > > getaddrinfo() > > https://secure.ucc.asn.au/hg/dropbear/file/cbd674d63cd4/dbutil.c#l415 > > (moved to netio.c in head, and PF_UNSPEC has been fixed to > > AF_UNSPEC). Pre-authentication should be OK, only > > getnameinfo() is called (if that's enabled). > > Yes, I agree dropbear is affected. > > And wow, this is an utter mess. Not only does dropbear fail to drop > root before processing forwards; it NEVER drops root at all. The > user's session remains running as root for its full lifetime. Aside > from being a huge risk, it also allows users to bypass uid-based > firewall rules via port forwarding; for example, a rule that forbids > normal users from making outgoing connections on port 25 would not be > honored. > > Is there any reason for not performing the setgroups/setgid/setuid > immediately after authentication succeeds? Have you looked at whether > it would be easy to patch that in? Simply copying/moving the code from svr-chansession.c's execchild to svr-auth.c's send_msg_userauth_success seems to fix the entire issue. I had to disable the (useless on systems with proper pty support) chown/chmod for the pty, but otherwise it seems to be working fine. Rich
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