plugins/python: add support for callback errstr arguments

Plugins can raise a sudo.PluginError exception to add context message
for the failure.

The callback's errstr gets filled up with the specified message.
But, as sudo expects a string constant (will not free the string),
we store it in the plugin context at least until next callback
invocation.

plugins/python/python_plugin_common.c

@@ -110,6 +110,37 @@ _import_module(const char *path)
     debug_return_ptr(PyImport_ImportModule(module_name));
 }
 
+void
+python_plugin_handle_plugin_error_exception(struct PluginContext *plugin_ctx)
+{
+    debug_decl(python_plugin_handle_plugin_error_exception, PYTHON_DEBUG_INTERNAL);
+
+    free(plugin_ctx->callback_error);
+    plugin_ctx->callback_error = NULL;
+
+    if (PyErr_Occurred() && PyErr_ExceptionMatches(sudo_exc_PluginError)) {
+        PyObject *py_type = NULL, *py_message = NULL, *py_traceback = NULL;
+        PyErr_Fetch(&py_type, &py_message, &py_traceback);
+
+        char *message = py_message ? py_create_string_rep(py_message) : NULL;
+        sudo_debug_printf(SUDO_DEBUG_INFO, "received sudo.PluginError exception with message '%s'",
+                          message == NULL ? "(null)" : message);
+
+        if (message != NULL && plugin_ctx->sudo_api_version < SUDO_API_MKVERSION(1, 15)) {
+            py_sudo_log(SUDO_CONV_ERROR_MSG, "%s", message);
+            free(message);
+        } else {
+            plugin_ctx->callback_error = message;
+        }
+
+        Py_CLEAR(py_type);
+        Py_CLEAR(py_message);
+        Py_CLEAR(py_traceback);
+    }
+
+    debug_return;
+}
+
 int
 python_plugin_construct_custom(struct PluginContext *plugin_ctx, PyObject *py_kwargs)
 {
@@ -124,15 +155,18 @@ python_plugin_construct_custom(struct PluginContext *plugin_ctx, PyObject *py_kw
                          py_args, py_kwargs, PYTHON_DEBUG_PY_CALLS);
 
     plugin_ctx->py_instance = PyObject_Call(plugin_ctx->py_class, py_args, py_kwargs);
+    python_plugin_handle_plugin_error_exception(plugin_ctx);
 
     py_debug_python_result(python_plugin_name(plugin_ctx), "__init__",
                            plugin_ctx->py_instance, PYTHON_DEBUG_PY_CALLS);
 
+    if (plugin_ctx->py_instance)
         rc = SUDO_RC_OK;
 
 cleanup:
-    if (plugin_ctx->py_instance == NULL) {
+    if (PyErr_Occurred()) {
         py_log_last_error("Failed to construct plugin instance");
+        Py_CLEAR(plugin_ctx->py_instance);
         rc = SUDO_RC_ERROR;
     }
 
@@ -261,7 +295,8 @@ _python_plugin_register_plugin_in_py_ctx(void)
 }
 
 int
-python_plugin_init(struct PluginContext *plugin_ctx, char * const plugin_options[])
+python_plugin_init(struct PluginContext *plugin_ctx, char * const plugin_options[],
+                   unsigned int version)
 {
     debug_decl(python_plugin_init, PYTHON_DEBUG_PLUGIN_LOAD);
 
@@ -270,6 +305,8 @@ python_plugin_init(struct PluginContext *plugin_ctx, char * const plugin_options
     if (_python_plugin_register_plugin_in_py_ctx() != SUDO_RC_OK)
         goto cleanup;
 
+    plugin_ctx->sudo_api_version = version;
+
     plugin_ctx->py_interpreter = Py_NewInterpreter();
     if (plugin_ctx->py_interpreter == NULL) {
         goto cleanup;
@@ -341,6 +378,7 @@ python_plugin_deinit(struct PluginContext *plugin_ctx)
         Py_EndInterpreter(plugin_ctx->py_interpreter);
     }
 
+    free(plugin_ctx->callback_error);
     memset(plugin_ctx, 0, sizeof(*plugin_ctx));
 
     if (py_ctx.open_plugin_count <= 0) {
@@ -390,7 +428,10 @@ python_plugin_api_call(struct PluginContext *plugin_ctx, const char *func_name,
 
     py_debug_python_result(python_plugin_name(plugin_ctx), func_name,
                            py_result, PYTHON_DEBUG_PY_CALLS);
-    if (py_result == NULL) {
+
+    python_plugin_handle_plugin_error_exception(plugin_ctx);
+
+    if (PyErr_Occurred()) {
         py_log_last_error(NULL);
     }
 

plugins/python/python_plugin_common.h

@@ -27,11 +27,16 @@ struct PluginContext {
     PyObject *py_class;
     PyObject *py_instance;
     int call_close;
+    unsigned int sudo_api_version;
+
+    // We use this to let the error string live until sudo and the audit plugins
+    // are using it. Only set for sudo API >= 1.15, otherwise NULL
+    char *callback_error;
 };
 
 int python_plugin_register_logging(sudo_conv_t conversation, sudo_printf_t sudo_printf, char * const settings[]);
 
-int python_plugin_init(struct PluginContext *plugin_ctx, char * const plugin_options[]);
+int python_plugin_init(struct PluginContext *plugin_ctx, char * const plugin_options[], unsigned int version);
 
 int python_plugin_construct_custom(struct PluginContext *plugin_ctx, PyObject *py_kwargs);
 

plugins/python/python_plugin_group.c

@@ -53,7 +53,7 @@ python_plugin_group_init(int version, sudo_printf_t sudo_printf, char *const plu
     if (rc != SUDO_RC_OK)
         debug_return_int(rc);
 
-    rc = python_plugin_init(&plugin_ctx, plugin_options);
+    rc = python_plugin_init(&plugin_ctx, plugin_options, (unsigned int)version);
     if (rc != SUDO_RC_OK)
         debug_return_int(rc);
 

plugins/python/python_plugin_io.c

@@ -44,6 +44,15 @@ struct IOPluginContext
             (void **)&CALLBACK_PLUGINFUNC(function_name)); \
     } while(0)
 
+#define IO_CB_SET_ERROR(errstr) \
+    do { \
+        const char *cb_error = io_ctx->base_ctx.callback_error; \
+        if (cb_error != NULL && errstr != NULL) { \
+            *errstr = cb_error; \
+        } \
+    } while(false)
+
+
 static int
 _call_plugin_open(struct IOPluginContext *io_ctx, int argc, char * const argv[], char * const command_info[])
 {
@@ -95,14 +104,17 @@ python_plugin_io_open(struct IOPluginContext *io_ctx,
         debug_return_int(rc);
 
     struct PluginContext *plugin_ctx = BASE_CTX(io_ctx);
-    rc = python_plugin_init(plugin_ctx, plugin_options);
+    rc = python_plugin_init(plugin_ctx, plugin_options, version);
+
     if (rc != SUDO_RC_OK)
         debug_return_int(rc);
 
     rc = python_plugin_construct(plugin_ctx, PY_IO_PLUGIN_VERSION,
                                  settings, user_info, user_env, plugin_options);
-    if (rc != SUDO_RC_OK)
+    if (rc != SUDO_RC_OK) {
+        IO_CB_SET_ERROR(errstr);
         debug_return_int(rc);
+    }
 
     // skip plugin callbacks which are not mandatory
     MARK_CALLBACK_OPTIONAL(show_version);
@@ -118,6 +130,7 @@ python_plugin_io_open(struct IOPluginContext *io_ctx,
     if (argc > 0)  // we only call open if there is request for running sg
         rc = _call_plugin_open(io_ctx, argc, argv, command_info);
 
+    IO_CB_SET_ERROR(errstr);
     debug_return_int(rc);
 }
 
@@ -151,8 +164,10 @@ python_plugin_io_log_ttyin(struct IOPluginContext *io_ctx, const char *buf, unsi
 {
     debug_decl(python_plugin_io_log_ttyin, PYTHON_DEBUG_CALLBACKS);
     PyThreadState_Swap(BASE_CTX(io_ctx)->py_interpreter);
-    debug_return_int(python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_ttyin),
+    int rc = python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_ttyin),
-                                     Py_BuildValue("(s#)", buf, len)));
+                                       Py_BuildValue("(s#)", buf, len));
+    IO_CB_SET_ERROR(errstr);
+    debug_return_int(rc);
 }
 
 int
@@ -160,8 +175,10 @@ python_plugin_io_log_ttyout(struct IOPluginContext *io_ctx, const char *buf, uns
 {
     debug_decl(python_plugin_io_log_ttyout, PYTHON_DEBUG_CALLBACKS);
     PyThreadState_Swap(BASE_CTX(io_ctx)->py_interpreter);
-    debug_return_int(python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_ttyout),
+    int rc = python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_ttyout),
-                                     Py_BuildValue("(s#)", buf, len)));
+                                       Py_BuildValue("(s#)", buf, len));
+    IO_CB_SET_ERROR(errstr);
+    debug_return_int(rc);
 }
 
 int
@@ -169,8 +186,10 @@ python_plugin_io_log_stdin(struct IOPluginContext *io_ctx, const char *buf, unsi
 {
     debug_decl(python_plugin_io_log_stdin, PYTHON_DEBUG_CALLBACKS);
     PyThreadState_Swap(BASE_CTX(io_ctx)->py_interpreter);
-    debug_return_int(python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_stdin),
+    int rc = python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_stdin),
-                                               Py_BuildValue("(s#)", buf, len)));
+                                               Py_BuildValue("(s#)", buf, len));
+    IO_CB_SET_ERROR(errstr);
+    debug_return_int(rc);
 }
 
 int
@@ -178,8 +197,10 @@ python_plugin_io_log_stdout(struct IOPluginContext *io_ctx, const char *buf, uns
 {
     debug_decl(python_plugin_io_log_stdout, PYTHON_DEBUG_CALLBACKS);
     PyThreadState_Swap(BASE_CTX(io_ctx)->py_interpreter);
-    debug_return_int(python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_stdout),
+    int rc = python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_stdout),
-                                               Py_BuildValue("(s#)", buf, len)));
+                                               Py_BuildValue("(s#)", buf, len));
+    IO_CB_SET_ERROR(errstr);
+    debug_return_int(rc);
 }
 
 int
@@ -187,8 +208,10 @@ python_plugin_io_log_stderr(struct IOPluginContext *io_ctx, const char *buf, uns
 {
     debug_decl(python_plugin_io_log_stderr, PYTHON_DEBUG_CALLBACKS);
     PyThreadState_Swap(BASE_CTX(io_ctx)->py_interpreter);
-    debug_return_int(python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_stderr),
+    int rc = python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_stderr),
-                                               Py_BuildValue("(s#)", buf, len)));
+                                               Py_BuildValue("(s#)", buf, len));
+    IO_CB_SET_ERROR(errstr);
+    debug_return_int(rc);
 }
 
 int
@@ -196,8 +219,10 @@ python_plugin_io_change_winsize(struct IOPluginContext *io_ctx, unsigned int lin
 {
     debug_decl(python_plugin_io_change_winsize, PYTHON_DEBUG_CALLBACKS);
     PyThreadState_Swap(BASE_CTX(io_ctx)->py_interpreter);
-    debug_return_int(python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(change_winsize),
+    int rc = python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(change_winsize),
-                                               Py_BuildValue("(ii)", line, cols)));
+                                       Py_BuildValue("(ii)", line, cols));
+    IO_CB_SET_ERROR(errstr);
+    debug_return_int(rc);
 }
 
 int
@@ -205,8 +230,10 @@ python_plugin_io_log_suspend(struct IOPluginContext *io_ctx, int signo, const ch
 {
     debug_decl(python_plugin_io_log_suspend, PYTHON_DEBUG_CALLBACKS);
     PyThreadState_Swap(BASE_CTX(io_ctx)->py_interpreter);
-    debug_return_int(python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_suspend),
+    int rc = python_plugin_api_rc_call(BASE_CTX(io_ctx), CALLBACK_PYNAME(log_suspend),
-                                     Py_BuildValue("(i)", signo)));
+                                       Py_BuildValue("(i)", signo));
+    IO_CB_SET_ERROR(errstr);
+    debug_return_int(rc);
 }
 
 // generate symbols for loading multiple io plugins:

plugins/python/python_plugin_policy.c

@@ -42,6 +42,14 @@ extern struct policy_plugin python_policy;
             (void **)&CALLBACK_PLUGINFUNC(function_name)); \
     } while(0)
 
+#define CB_SET_ERROR(errstr) \
+    do { \
+        const char *cb_error = plugin_ctx.callback_error; \
+        if (cb_error != NULL && errstr != NULL) { \
+            *errstr = cb_error; \
+        } \
+    } while(0)
+
 static int
 python_plugin_policy_open(unsigned int version, sudo_conv_t conversation,
     sudo_printf_t sudo_printf, char * const settings[],
@@ -60,12 +68,13 @@ python_plugin_policy_open(unsigned int version, sudo_conv_t conversation,
     if (rc != SUDO_RC_OK)
         debug_return_int(rc);
 
-    rc = python_plugin_init(&plugin_ctx, plugin_options);
+    rc = python_plugin_init(&plugin_ctx, plugin_options, version);
     if (rc != SUDO_RC_OK)
         debug_return_int(rc);
 
     rc = python_plugin_construct(&plugin_ctx, PY_POLICY_PLUGIN_VERSION, settings,
                                  user_info, user_env, plugin_options);
+    CB_SET_ERROR(errstr);
     if (rc != SUDO_RC_OK) {
         debug_return_int(rc);
     }
@@ -147,6 +156,7 @@ python_plugin_policy_check(int argc, char * const argv[],
         *user_env_out = py_str_array_from_tuple(py_user_env_out);
 
     rc = python_plugin_rc_to_int(py_rc);
+    CB_SET_ERROR(errstr);
 
 cleanup:
     if (PyErr_Occurred()) {
@@ -185,6 +195,8 @@ python_plugin_policy_list(int argc, char * const argv[], int verbose, const char
         Py_BuildValue("(Oiz)", py_argv, verbose, list_user));
 
     Py_XDECREF(py_argv);
+
+    CB_SET_ERROR(errstr);
     debug_return_int(rc);
 }
 
@@ -209,7 +221,9 @@ python_plugin_policy_validate(const char **errstr)
 {
     debug_decl(python_plugin_policy_validate, PYTHON_DEBUG_CALLBACKS);
     PyThreadState_Swap(plugin_ctx.py_interpreter);
-    debug_return_int(python_plugin_api_rc_call(&plugin_ctx, CALLBACK_PYNAME(validate), NULL));
+    int rc = python_plugin_api_rc_call(&plugin_ctx, CALLBACK_PYNAME(validate), NULL);
+    CB_SET_ERROR(errstr);
+    debug_return_int(rc);
 }
 
 void
@@ -262,6 +276,7 @@ python_plugin_policy_init_session(struct passwd *pwd, char **user_env[], const c
     }
 
     rc = python_plugin_rc_to_int(py_rc);
+    CB_SET_ERROR(errstr);
 
 cleanup:
     Py_XDECREF(py_pwd);

plugins/python/sudo_python_module.c

@@ -31,6 +31,7 @@ PyAPI_FUNC(PyObject *) PyStructSequence_GetItem(PyObject *, Py_ssize_t);
 
 // exceptions:
 PyObject *sudo_exc_SudoException;
+PyObject *sudo_exc_PluginError;
 static PyObject *sudo_exc_ConversationInterrupted;
 
 // the methods exposed in the "sudo" python module
@@ -562,6 +563,7 @@ sudo_module_init(void)
         } while(0);
 
     MODULE_ADD_EXCEPTION(SudoException, NULL);
+    MODULE_ADD_EXCEPTION(PluginError, NULL);
     MODULE_ADD_EXCEPTION(ConversationInterrupted, EXC_VAR(SudoException));
 
     #define MODULE_REGISTER_ENUM(name, key_values) \
@@ -611,6 +613,7 @@ cleanup:
     if (PyErr_Occurred()) {
         Py_CLEAR(py_module);
         Py_CLEAR(sudo_exc_SudoException);
+        Py_CLEAR(sudo_exc_PluginError);
         Py_CLEAR(sudo_exc_ConversationInterrupted);
     }
 

plugins/python/sudo_python_module.h

@@ -21,7 +21,11 @@
 
 #include "pyhelpers.h"
 
-extern PyObject *sudo_exc_SudoException;
+extern PyObject *sudo_exc_SudoException;  // Base exception for the sudo module problems
+
+// This is for the python plugins to report errors for us
+extern PyObject *sudo_exc_PluginError;
+
 extern PyTypeObject *sudo_type_Plugin;
 extern PyTypeObject *sudo_type_ConvMessage;