[Swan] [Swan-announce] libreswan-3.18 released for CVE-2016-5391
Nick Howitt
nick at howitts.co.uk
Sat Jul 30 15:01:37 UTC 2016
Hi,
There is a permission error with the el6 binary,
https://download.libreswan.org/binaries/rhel/6/x86_64/libreswan-3.18-1.el6.x86_64.rpm.
It returns a 403 - Forbidden
Regards,
Nick
On 27/07/2016 15:34, The Libreswan Project wrote:
>
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA512
>
>
> Release date: Monday Jul 25, 2016
>
> CVE-2016-5391 IKEv2 bogus proposal lacking DH transform causes restart
>
> URL: http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=2016-5391
>
> This alert (and any possible updates) is available at the following URLs:
> https: //libreswan.org/security/CVE-2016-5391/
>
> The Libreswan Project has found a vulnerability in processing IKEv2
> proposals that miss a Diffie-Hellman transform for the IKE SA. A NULL
> pointer dererefence causes the pluto IKE daemon to crash and restart.
> No remote code execution is possible.
>
> Vulnerable versions: libreswan 3.17
> Not vulnerable : all other versions of libreswan
>
> If you cannot upgrade to 3.18, please see the above link for a patch for
> this issue.
>
> Vulnerability information
> =========================
>
> The IKE SA negotiation requires a Diffie-Hellman group to be agreed upon.
> This payload is mandatory for all IKE SA proposals during the IKE_INIT
> Exchange Type. It is only optional for the CREATE_CHILD_SA Exchange
> Type, where PFS is optional.
>
> Libreswan version 3.17 does not properly reject a proposal in IKE_INIT
> Exchange that lacks a Diffie-Hellman group. It dereferences a NULL
> pointer causing a crash and restart.
>
> Exploitation
> ============
>
> A denial of service can be launched by anyone repeatedly sending such
> IKE packets.
>
> No authentication credentials are required. No remote code execution is
> possible through this vulnerability. Libreswan automatically restarts
> when
> it crashes.
>
> Workaround
> ==========
>
> There is no workaround. Either upgrade or use the supplied patch in the
> above listed resource URL.
>
> Credits
> =======
>
> This vulnerability was found by the Libreswan Project when performing
> interop tests with strongswan version 5.4.0 which can transmit these
> bogus proposals. It has been assigned strongSwan issue #2051
>
> About libreswan (https://libreswan.org/)
> ========================================
>
> Libreswan is a free implementation of the Internet Protocol Security
> (IPsec) suite and Internet Key Exchange (IKE) protocols. It is a
> descendant (fork) of openswan 2.6.38.
>
> IPsec uses strong cryptography to provide both authentication and
> encryption services. These services allow you to build secure tunnels
> through untrusted networks. Everything passing through the untrusted
> network is encrypted by the IPsec gateway machine, and decrypted by
> the gateway at the other end of the tunnel. The resulting tunnel is a
> virtual private network (VPN).
>
> Patch
> ======================================================================
>
> diff --git a/programs/pluto/ikev2_spdb_struct.c
> b/programs/pluto/ikev2_spdb_struct.c
> index 753c26e..f46b5a5 100644
> - ---- a/programs/pluto/ikev2_spdb_struct.c
> +++ b/programs/pluto/ikev2_spdb_struct.c
> @@ -769,17 +769,44 @@ static int process_transforms(pb_stream
> *prop_pbs, struct print *remote_print_bu
> DBG(DBG_CONTROL, DBG_log("allowing no NULL
> integrity"));
> continue;
> }
> - -- int type_proposed = ((transform_types_found &
> LELEM(type)) != 0);
> - -- int type_matched =
> matching_local_proposal->matching_transform[type]->valid;
> - -- if (type_proposed != type_matched) {
> - -- DBG(DBG_CONTROLMORE, DBG_log("local proposal %d
> type %s failed: %s and %s",
> + bool local_transform_type_present =
> local_transforms->transform[0].valid;
> + bool remote_transform_type_present =
> ((transform_types_found & LELEM(type)) != 0);
> + /*
> + * Check that the local and remote end are
> + * consistent about the transform being
> + * present.
> + *
> + * Transform matching is not optional.
> + * Instead, for something like ESP/AH, DH is
> + * made "optional" by sending two proposals.
> + * One with the transform (DH) present and one
> + * with it absent.
> + */
> + if (local_transform_type_present !=
> remote_transform_type_present) {
> + DBG(DBG_CONTROLMORE, DBG_log("local proposal %d
> transform type %s failed: local %s and remote %s",
> + local_propnum, trans_type_name(type),
> + local_transform_type_present ? "present" : "absent",
> + remote_transform_type_present ? "present" : "absent"));
> + break;
> + }
> + /*
> + * Check that when the transform type is
> + * required it also matches and vice versa.
> + *
> + * Since !local_transform_type_present implies
> + * !remote_transform_type_matched, the above
> + * test is also required.
> + */
> + bool remote_transform_type_matched =
> matching_local_proposal->matching_transform[type]->valid;
> + if (local_transform_type_present !=
> remote_transform_type_matched) {
> + DBG(DBG_CONTROLMORE, DBG_log("local proposal %d
> transform type %s failed: local %s and remote %s",
> local_propnum, trans_type_name(type),
> - -- type_proposed ? "proposed" :
> "not-proposed",
> - -- type_matched ? "matched" :
> "not-matched"));
> + local_transform_type_present ? "present" : "absent",
> + remote_transform_type_matched ? "matched" : "different"));
> break;
> }
> }
> - -- /* loop finished? */
> + /* loop finished cleanly? */
> if (type == IKEv2_TRANS_TYPE_ROOF) {
> DBG(DBG_CONTROL,
> DBG_log("remote proposal %u matches local proposal %d",
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