Commit 13f12430 authored by Daniel P. Berrangé's avatar Daniel P. Berrangé
Browse files

crypto: add support for TLS priority string override 



The gnutls default priority is either "NORMAL" (most historical
versions of gnutls) which is a built-in label in gnutls code,
or "@SYSTEM" (latest gnutls on Fedora at least) which refers
to an admin customizable entry in a gnutls config file.

Regardless of which default is used by a distro, they are both
global defaults applying to all applications using gnutls. If
a single application on the system needs to use a weaker set
of crypto priorities, this potentially forces the weakness onto
all applications. Or conversely if a single application wants a
strong default than all others, it can't do this via the global
config file.

This adds an extra parameter to the tls credential object which
allows the mgmt app / user to explicitly provide a priority
string to QEMU when configuring TLS.

For example, to use the "NORMAL" priority, but disable SSL 3.0
one can now configure QEMU thus:

  $QEMU -object tls-creds-x509,id=tls0,dir=/home/berrange/qemutls,\
                priority="NORMAL:-VERS-SSL3.0" \
        ..other args...

If creating tls-creds-anon, whatever priority the user specifies
will always have "+ANON-DH" appended to it, since that's mandatory
to make the anonymous credentials work.

Signed-off-by: default avatarDaniel P. Berrange <berrange@redhat.com>
parent 9164b897

crypto/tlscreds.c

+26 −0
Original line number Diff line number Diff line
@@ -178,6 +178,27 @@ qcrypto_tls_creds_prop_get_dir(Object *obj, 
}





static void

qcrypto_tls_creds_prop_set_priority(Object *obj,

                                    const char *value,

                                    Error **errp G_GNUC_UNUSED)

{

    QCryptoTLSCreds *creds = QCRYPTO_TLS_CREDS(obj);



    creds->priority = g_strdup(value);

}





static char *

qcrypto_tls_creds_prop_get_priority(Object *obj,

                                    Error **errp G_GNUC_UNUSED)

{

    QCryptoTLSCreds *creds = QCRYPTO_TLS_CREDS(obj);



    return g_strdup(creds->priority);

}





static void

qcrypto_tls_creds_prop_set_endpoint(Object *obj,

                                    int value,
@@ -216,6 +237,10 @@ qcrypto_tls_creds_class_init(ObjectClass *oc, void *data) 
                                   qcrypto_tls_creds_prop_get_endpoint,

                                   qcrypto_tls_creds_prop_set_endpoint,

                                   NULL);

    object_class_property_add_str(oc, "priority",

                                  qcrypto_tls_creds_prop_get_priority,

                                  qcrypto_tls_creds_prop_set_priority,

                                  NULL);

}
@@ -234,6 +259,7 @@ qcrypto_tls_creds_finalize(Object *obj) 
    QCryptoTLSCreds *creds = QCRYPTO_TLS_CREDS(obj);



    g_free(creds->dir);

    g_free(creds->priority);

}

crypto/tlssession.c

+19 −7
Original line number Diff line number Diff line
@@ -132,14 +132,22 @@ qcrypto_tls_session_new(QCryptoTLSCreds *creds, 
    if (object_dynamic_cast(OBJECT(creds),

                            TYPE_QCRYPTO_TLS_CREDS_ANON)) {

        QCryptoTLSCredsAnon *acreds = QCRYPTO_TLS_CREDS_ANON(creds);

        char *prio;



        ret = gnutls_priority_set_direct(session->handle,

                                         "NORMAL:+ANON-DH", NULL);

        if (creds->priority != NULL) {

            prio = g_strdup_printf("%s:+ANON-DH", creds->priority);

        } else {

            prio = g_strdup("NORMAL:+ANON-DH");

        }



        ret = gnutls_priority_set_direct(session->handle, prio, NULL);

        if (ret < 0) {

            error_setg(errp, "Unable to set TLS session priority: %s",

                       gnutls_strerror(ret));

            error_setg(errp, "Unable to set TLS session priority %s: %s",

                       prio, gnutls_strerror(ret));

            g_free(prio);

            goto error;

        }

        g_free(prio);

        if (creds->endpoint == QCRYPTO_TLS_CREDS_ENDPOINT_SERVER) {

            ret = gnutls_credentials_set(session->handle,

                                         GNUTLS_CRD_ANON,
@@ -157,11 +165,15 @@ qcrypto_tls_session_new(QCryptoTLSCreds *creds, 
    } else if (object_dynamic_cast(OBJECT(creds),

                                   TYPE_QCRYPTO_TLS_CREDS_X509)) {

        QCryptoTLSCredsX509 *tcreds = QCRYPTO_TLS_CREDS_X509(creds);

        const char *prio = creds->priority;

        if (!prio) {

            prio = "NORMAL";

        }



        ret = gnutls_set_default_priority(session->handle);

        ret = gnutls_priority_set_direct(session->handle, prio, NULL);

        if (ret < 0) {

            error_setg(errp, "Cannot set default TLS session priority: %s",

                       gnutls_strerror(ret));

            error_setg(errp, "Cannot set default TLS session priority %s: %s",

                       prio, gnutls_strerror(ret));

            goto error;

        }

        ret = gnutls_credentials_set(session->handle,

include/crypto/tlscreds.h

+1 −0
Original line number Diff line number Diff line
@@ -54,6 +54,7 @@ struct QCryptoTLSCreds { 
    gnutls_dh_params_t dh_params;

#endif

    bool verifyPeer;

    char *priority;

};