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

[Ravikumar Chennaparapu]

Hi Andreas,

Thanks for the quick reply.

Could you point out the code where peer remote cert validation happens for
CERT payload?

Regards,
Ravi



On Thu, Jan 4, 2018 at 2:18 AM, Andreas Steffen <
andreas.steffen at strongswan.org> wrote:

> 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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