[strongSwan-dev] CERT payload (X.509 certificates) validation issue

[Andreas Steffen]

Hi Ravi,

we are not adding received certificates to any trusted cache.
Per default remote certificates are never trusted and are temporarily
added to the auth_cfg object of the IKE_SA. Full X.509 trust chain
verification then happens at a later stage.

Regards

Andreas

On 03.01.2018 14:47, Ravikumar Chennaparapu wrote:
> Hi,
>
> We found an issue with strongswan 5.2.2; peer is accepting CERT payload
> even though  digital signature field in CERT payload is tampered.
>
> As per the below code, there is no validation for the peer's pub key
> certificate; peer's public key is added to the cache without any
> validation. We do see this as a security vulnerability, could you check
> this? Is our understanding correct ?
>
>
> static void process_x509(cert_payload_t *payload, auth_cfg_t *auth,
> cert_encoding_t encoding, bool *first)
> {
> certificate_t *cert;
> char *url;
>
> cert = try_get_cert(payload);
> if (cert)
> {
> if (*first)
> { /* the first is an end entity certificate */
> DBG1(DBG_IKE, "received end entity cert \"%Y\"",
> cert->get_subject(cert));
> auth->add(auth, AUTH_HELPER_SUBJECT_CERT, cert);
> *first = FALSE;
> }
> else
> {
> DBG1(DBG_IKE, "received issuer cert \"%Y\"",
> cert->get_subject(cert));
> auth->add(auth, AUTH_HELPER_IM_CERT, cert);
> }
> }
> else if (encoding == ENC_X509_HASH_AND_URL)
> {
> /* we fetch the certificate not yet, but only if
> * it is really needed during authentication */
> url = payload->get_url(payload);
> if (!url)
> {
> DBG1(DBG_IKE, "received invalid hash-and-url "
> "encoded cert, ignore");
> return;
> }
> url = strdup(url);
> if (*first)
> { /* first URL is for an end entity certificate */
> DBG1(DBG_IKE, "received hash-and-url for end entity cert \"%s\"",
> url);
> auth->add(auth, AUTH_HELPER_SUBJECT_HASH_URL, url);
> *first = FALSE;
> }
> else
> {
> DBG1(DBG_IKE, "received hash-and-url for issuer cert \"%s\"", url);
> auth->add(auth, AUTH_HELPER_IM_HASH_URL, url);
> }
> }
> }
>
> Thanks and Regards,
> Ravi

-- 
======================================================================
Andreas Steffen                         andreas.steffen at strongswan.org
strongSwan - the Open Source VPN Solution!          www.strongswan.org
Institute for Networked Solutions
University of Applied Sciences Rapperswil
CH-8640 Rapperswil (Switzerland)
===========================================================[INS-HSR]==

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