kdc: Allow KDC plugin to handle attempts to authenticate without using hardware authentication

Signed-off-by: Jennifer Sutton <jennifersutton@catalyst.net.nz>

kdc/kdc-plugin.c

@@ -51,7 +51,7 @@ static const char *kdc_plugin_deps[] = {
 static struct heim_plugin_data kdc_plugin_data = {
     "krb5",
     "kdc",
-    KRB5_PLUGIN_KDC_VERSION_10,
+    KRB5_PLUGIN_KDC_VERSION_11,
     kdc_plugin_deps,
     kdc_get_instance
 };
@@ -239,6 +239,33 @@ _kdc_referral_policy(astgs_request_t r)
     return ret;
 }
 
+static krb5_error_code KRB5_LIB_CALL
+hwauth_policy(krb5_context context, const void *plug, void *plugctx, void *userctx)
+{
+    const krb5plugin_kdc_ftable *ft = plug;
+
+    if (ft->hwauth_policy == NULL) {
+        return KRB5_PLUGIN_NO_HANDLE;
+    }
+    return ft->hwauth_policy(rk_UNCONST(plug), userctx);
+}
+
+krb5_error_code
+_kdc_hwauth_policy(astgs_request_t r)
+{
+    krb5_error_code ret = KRB5_PLUGIN_NO_HANDLE;
+
+    if (have_plugin) {
+        ret = _krb5_plugin_run_f(r->context, &kdc_plugin_data, 0, r, hwauth_policy);
+    }
+
+    if (ret != KRB5_PLUGIN_NO_HANDLE) {
+        return ret;
+    }
+
+    return r->client->flags.require_hwauth ? KRB5KDC_ERR_POLICY : 0;
+}
+
 static krb5_error_code KRB5_LIB_CALL
 finalize_reply(krb5_context context, const void *plug, void *plugctx, void *userctx)
 {

kdc/kdc-plugin.h

@@ -95,6 +95,16 @@ typedef krb5_error_code
 typedef krb5_error_code
 (KRB5_CALLCONV *krb5plugin_kdc_referral_policy)(void *, astgs_request_t);
 
+/*
+ * A hardware authentication policy plugin can indicate what is to
+ * happen when a client authenticates using a method other than
+ * hardware authentication. It can return zero to allow the
+ * authentication, or an appropriate error code to deny it.
+ */
+
+typedef krb5_error_code
+(KRB5_CALLCONV *krb5plugin_kdc_hwauth_policy)(void *, astgs_request_t);
+
 /*
  * Update the AS or TGS reply immediately prior to encoding.
  */
@@ -117,7 +127,7 @@ typedef krb5_error_code
  * Plugins should carefully check API contract notes for changes
  * between plugin API versions.
  */
-#define KRB5_PLUGIN_KDC_VERSION_10	10
+#define KRB5_PLUGIN_KDC_VERSION_11	11
 
 typedef struct krb5plugin_kdc_ftable {
     HEIM_PLUGIN_FTABLE_COMMON_ELEMENTS(krb5_context);
@@ -125,6 +135,7 @@ typedef struct krb5plugin_kdc_ftable {
     krb5plugin_kdc_pac_verify		pac_verify;
     krb5plugin_kdc_client_access	client_access;
     krb5plugin_kdc_referral_policy	referral_policy;
+    krb5plugin_kdc_hwauth_policy	hwauth_policy;
     krb5plugin_kdc_finalize_reply	finalize_reply;
     krb5plugin_kdc_audit		audit;
 } krb5plugin_kdc_ftable;

kdc/kerberos5.c

@@ -2270,12 +2270,12 @@ _kdc_as_rep(astgs_request_t r)
                     ret = KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN;
                     goto out;
                 }
-                if (r->client->flags.require_hwauth &&
-                    !(pat[n].flags & PA_HARDWARE_AUTH)) {
-                    kdc_log(r->context, config, 4, "Hardware authentication required for %s", r->cname);
-
-                    ret = KRB5KDC_ERR_POLICY;
-                    goto out;
+                if (!(pat[n].flags & PA_HARDWARE_AUTH)) {
+                    ret = _kdc_hwauth_policy(r);
+                    if (ret) {
+                        kdc_log(r->context, config, 4, "Hardware authentication required for %s", r->cname);
+                        goto out;
+                    }
                 }
 		kdc_audit_addkv((kdc_request_t)r, KDC_AUDIT_VIS, "pa", "%s",
 				pat[n].name);

tests/plugin/kdc_test_plugin.c

@@ -162,13 +162,14 @@ audit(void *ctx, astgs_request_t r)
 }
 
 static krb5plugin_kdc_ftable kdc_plugin = {
-    KRB5_PLUGIN_KDC_VERSION_10,
+    KRB5_PLUGIN_KDC_VERSION_11,
     init,
     fini,
     pac_generate,
     pac_verify,
     client_access,
     NULL, /* referral_policy */
+    NULL, /* hwauth_policy */
     finalize_reply,
     audit
 };