BugTraq
CAN-2004-0155: The KAME IKE Daemon Racoon does not verify RSASignatures during Phase 1, allows man-in-the-middle attacks andunauthorized connections Apr 07 2004 04:54PM
Ralf Spenneberg (ralf spenneberg net)
Security Advisory: The KAME IKE Daemon Racoon does not verify RSA
Signatures during Phase 1, allows man-in-the-middle attacks and
unauthorized connections

Author: Ralf Spenneberg <ralf (at) spenneberg (dot) net [email concealed]>

Revision: 1

Last Updated: April 07, 2004 18:00

CAN-2004-0155

Summary:
The KAME IKE Daemon racoon authenticates the peer in Phase 1 using
either preshared keys, RSA signatures or GSS-API. When RSA signatures
are used, racoon validates the X.509 certificate send by the peer but
not the RSA signature.
If the peer sends a valid and trusted X.509 certificate during Phase 1
any private key can be used to generate the RSA signature. The
authentication will still
succeed.

Impact:
Very High: Since racoon is the an often used IKE daemon on the *BSD
platform and on the native Linux kernel 2.6 IPsec stack.
If the attacker has access to a valid and trusted X.509 certificate he
can establish an IPsec connection to racoon or can start a
man-in-the-middle attack.

Exploit:
No exploit code is needed. Racoon itself can be used to exploit this
security bug. The important configuration line:
certificate_type x509 certificate badprivatekey;
If the certificate is valid and trusted by the attacked racoon the
attacker can
connect using any 'badprivatekey'

Vulnerable:
Tested:
Linux: ipsec-tools <=0.2.4; <=0.3rc4
FreeBSD 4.9 using racoon-20030711
Not-tested but probable looking at the code:
All KAME/racoon version published before April 06 2004
I do not have access to the Apple/racoon version, but it is highly
probable that this version is vulnerable, too.

Technical description:
In function eay_rsa_verify() in file crypto_openssl.c:
[...]
evp = d2i_PUBKEY(NULL, &bp, pubkey->l);
if (evp == NULL)
return 0;
[...]
In this context the function d2i_PUBKEY always returns NULL. The
function therefore exits with the returncode 0 (success). The actual
verification of the signature does not take place.

Solution:
Upgrade is needed. No workaround is known!
The attached patch fixed the problem on Linux using the ipsec-tools
package.
Updated packages are already available for some distributions:

ipsec-tools: http://ipsec-tools.sf.net
KAME: Updates are available in their CVS
Gentoo: Has already published their Security Advisory

Credits:
Michal Ludvig
Hans Hacker

--
Ralf Spenneberg
UNIX/Linux Trainer and Consultant, RHCE, RHCX
Waldring 34 48565 Steinfurt Germany
Fon: +49(0)2552 638 755 Fax: +49(0)2552 638 757
Mobil: +49(0)177 567 27 40

Markt+Technik Buch: Intrusion Detection für Linux Server
Addison-Wesley Buch: VPN mit Linux
IPsec-Howto: http://www.ipsec-howto.org
IPsec/PPTP Kernels for Red Hat Linux: http://www.spenneberg.com/.net/.org/.de
Honeynet Project Mirror: http://honeynet.spenneberg.org
Snort Mirror: http://snort.spenneberg.org

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