Set krb5 ccache only if krb5 is used

Check if the krb5 mechanism is present and only then set the cache, this
avoid wasteful operations if we are not even using krb5.

Signed-off-by: Simo Sorce <simo@redhat.com>

Author: simo5

src/mod_auth_gssapi.c

@@ -411,27 +411,9 @@ static bool mag_auth_basic(request_rec *req,
     gss_OID_set actual_mechs = GSS_C_NO_OID_SET;
     uint32_t init_flags = 0;
     uint32_t maj, min;
+    int present = 0;
     bool ret = false;
 
-#ifdef HAVE_GSS_KRB5_CCACHE_NAME
-    rs = apr_generate_random_bytes((unsigned char *)(&rndname),
-                                   sizeof(long long unsigned int));
-    if (rs != APR_SUCCESS) {
-        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, req,
-                      "Failed to generate random ccache name");
-        goto done;
-    }
-    user_ccache = apr_psprintf(req->pool, "MEMORY:user_%qu", rndname);
-    maj = gss_krb5_ccache_name(&min, user_ccache, &orig_ccache);
-    if (GSS_ERROR(maj)) {
-        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, req,
-                      "In Basic Auth, %s",
-                      mag_error(req, "gss_krb5_ccache_name() "
-                                "failed", maj, min));
-        goto done;
-    }
-#endif
-
     maj = gss_import_name(&min, &ba_user, GSS_C_NT_USER_NAME, &user);
     if (GSS_ERROR(maj)) {
         ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, req,
@@ -493,6 +475,42 @@ static bool mag_auth_basic(request_rec *req,
         allowed_mechs = filtered_mechs;
     }
 
+#ifdef HAVE_GSS_KRB5_CCACHE_NAME
+    /* If we are using the krb5 mechanism make sure to set a per thread
+     * memory ccache so that there can't be interferences between threads.
+     * Also make sure we have  new cache so no cached results end up being
+     * used. Some implementations of gss_acquire_cred_with_password() do
+     * not reacquire creds if cached ones are around, failing to check
+     * again for the password. */
+    maj = gss_test_oid_set_member(&min, discard_const(gss_mech_krb5),
+                                  allowed_mechs, &present);
+    if (GSS_ERROR(maj)) {
+        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, req,
+                      "In Basic Auth, %s",
+                      mag_error(req, "gss_test_oid_set_member() failed",
+                                maj, min));
+        goto done;
+    }
+    if (present) {
+        rs = apr_generate_random_bytes((unsigned char *)(&rndname),
+                                       sizeof(long long unsigned int));
+        if (rs != APR_SUCCESS) {
+            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, req,
+                          "Failed to generate random ccache name");
+            goto done;
+        }
+        user_ccache = apr_psprintf(req->pool, "MEMORY:user_%qu", rndname);
+        maj = gss_krb5_ccache_name(&min, user_ccache, &orig_ccache);
+        if (GSS_ERROR(maj)) {
+            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, req,
+                          "In Basic Auth, %s",
+                          mag_error(req, "gss_krb5_ccache_name() "
+                                    "failed", maj, min));
+            goto done;
+        }
+    }
+#endif
+
     maj = gss_acquire_cred_with_password(&min, user, &ba_pwd,
                                          GSS_C_INDEFINITE,
                                          allowed_mechs,