Handle PKINIT DH replies with no certs

If a PKINIT Diffie-Hellman reply contains no certificates in the
SignedData object, that may be because the signer certificate was a
trust anchor as transmitted to the KDC.  Heimdal's KDC, for instance,
filters client trust anchors out of the returned set of certificates.
Match against idctx->trustedCAs and idctx->intermediateCAs to handle
this case.  This fix only works with OpenSSL 1.0 or later; when built
against OpenSSL 0.9.x, the client will still require a cert in the
reply.

Code changes suggested by nalin@redhat.com.

ticket: 7183

1 files changed, 8 insertions, 1 deletions

diff --git a/src/plugins/preauth/pkinit/pkinit_crypto_openssl.c b/src/plugins/preauth/pkinit/pkinit_crypto_openssl.c
index 0136d4f47..7120ecf47 100644
--- a/src/plugins/preauth/pkinit/pkinit_crypto_openssl.c
+++ b/src/plugins/preauth/pkinit/pkinit_crypto_openssl.c
@@ -1398,8 +1398,15 @@ cms_signeddata_verify(krb5_context context,
         X509_STORE_set_verify_cb_func(store, openssl_callback_ignore_crls);
     X509_STORE_set_flags(store, vflags);
 
-    /* get the signer's information from the CMS message */
+    /*
+     * Get the signer's information from the CMS message.  Match signer ID
+     * against anchors and intermediate CAs in case no certs are present in the
+     * SignedData.  If we start sending kdcPkId values in requests, we'll need
+     * to match against the source of that information too.
+     */
     CMS_set1_signers_certs(cms, NULL, 0);
+    CMS_set1_signers_certs(cms, idctx->trustedCAs, CMS_NOINTERN);
+    CMS_set1_signers_certs(cms, idctx->intermediateCAs, CMS_NOINTERN);
     if (((si_sk = CMS_get0_SignerInfos(cms)) == NULL) ||
         ((si = sk_CMS_SignerInfo_value(si_sk, 0)) == NULL)) {
         /* Not actually signed; anonymous case */