Date: Tue, 31 Mar 2015 21:07:19 +0200 From: Denys Vlasenko <vda.linux@...glemail.com> To: Rich Felker <dalias@...c.org> Cc: busybox <busybox@...ybox.net>, musl <musl@...ts.openwall.com> Subject: Re: Busybox on musl is affected by CVE-2015-1817 On Mon, Mar 30, 2015 at 7:31 AM, Rich Felker <dalias@...c.org> wrote: > For details on CVE-2015-1817, see: > http://www.openwall.com/lists/musl/2015/03/30/1 > > With musl-linked Busybox installed setuid and ping enabled, exploiting > this issue is trivial. > > While CVE-2015-1817 is certainly musl's fault, there are two changes > to Busybox I'd like to propose that would have prevented it from being > exploitable: > > 1. Having setuid utilities like ping obtain the resource they need (in > the case of ping, SOCK_RAW) without processing user input at all, > then fully dropping root (setuid(getuid())) before doing anything. > This has been standard practice for setuid programs since the 90s > and it feels bad that busybox is not doing it. In general this is acceptable, but with this particular case and CVE, it wouldn't help. create_icmp_socket(lsa) needs to know of which address family the socket should be: if (lsa->u.sa.sa_family == AF_INET6) sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6); else sock = socket(AF_INET, SOCK_RAW, 1); /* 1 == ICMP */ This is only known after HOST is parsed. And CVE is in DNS resolving code :( > 2. Reconsider the rejection of the patch to add SOCK_DGRAM support for > ping, which allows it to run without root. This seems to lead to a significantly larger code.
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