gnu: openssh: Fix CVE-2016-8858.

* gnu/packages/patches/openssh-memory-exhaustion.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/ssh.scm (openssh)[source]: Use it.

gnu/local.mk

@@ -734,6 +734,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/openjpeg-CVE-2016-5157.patch		\
   %D%/packages/patches/openjpeg-CVE-2016-7163.patch		\
   %D%/packages/patches/openjpeg-use-after-free-fix.patch	\
+  %D%/packages/patches/openssh-memory-exhaustion.patch		\
   %D%/packages/patches/openssl-runpath.patch			\
   %D%/packages/patches/openssl-1.1.0-c-rehash-in.patch		\
   %D%/packages/patches/openssl-c-rehash-in.patch		\

gnu/packages/patches/openssh-memory-exhaustion.patch

@@ -0,0 +1,39 @@
+Fix a memory exhaustion bug in the key exchange, whereby an unauthenticated user
+could potentially consume 38400 MB of memory on the server:
+
+http://seclists.org/oss-sec/2016/q4/185
+
+Patch adapted from upstream source repository:
+
+https://github.com/openssh/openssh-portable/commit/ec165c392ca54317dbe3064a8c200de6531e89ad
+
+From ec165c392ca54317dbe3064a8c200de6531e89ad Mon Sep 17 00:00:00 2001
+From: "markus@openbsd.org" <markus@openbsd.org>
+Date: Mon, 10 Oct 2016 19:28:48 +0000
+Subject: [PATCH] upstream commit
+
+Unregister the KEXINIT handler after message has been
+received. Otherwise an unauthenticated peer can repeat the KEXINIT and cause
+allocation of up to 128MB -- until the connection is closed. Reported by
+shilei-c at 360.cn
+
+Upstream-ID: 43649ae12a27ef94290db16d1a98294588b75c05
+---
+ kex.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/kex.c b/kex.c
+index 3f97f8c..6a94bc5 100644
+--- a/kex.c
++++ b/kex.c
+@@ -481,6 +481,7 @@ kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
+ 	if (kex == NULL)
+ 		return SSH_ERR_INVALID_ARGUMENT;
+ 
++	ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
+ 	ptr = sshpkt_ptr(ssh, &dlen);
+ 	if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
+ 		return r;
+-- 
+2.10.1
+

gnu/packages/ssh.scm

@@ -121,6 +121,7 @@ (define-public openssh
                                         tail)
                          (string-append "http://ftp2.fr.openbsd.org/pub/OpenBSD/OpenSSH/portable/"
                                         tail))))
+            (patches (search-patches "openssh-memory-exhaustion.patch"))
             (sha256 (base32
                      "1k5y1wi29d47cgizbryxrhc1fbjsba2x8l5mqfa9b9nadnd9iyrz"))))
    (build-system gnu-build-system)