tlshd: Add a YAML parser

The TLS session tag definitions are to be specified using YAML.

Signed-off-by: Chuck Lever <[email protected]>

Author: chucklever

src/tlshd/tags.c

@@ -31,9 +31,64 @@
 #include <gnutls/abstract.h>
 
 #include <glib.h>
+#include <yaml.h>
 
 #include "tlshd.h"
 
+/** @name tagsLibYamlHelpers
+ *
+ * libyaml helpers
+ */
+
+///@{
+
+/**
+ * @brief Show a human-readable YAML event symbol
+ * @param[in]     event  A YAML parser event
+ *
+ * This implementation depends on the yaml_event_type_t enum being
+ * densely packed.
+ *
+ * @returns a constant NUL-terminated C string.
+ */
+static const char *show_yaml_event_type(const yaml_event_t *event)
+{
+	static const char *labels[] = {
+		[YAML_NO_EVENT]			= "YAML_NO_EVENT",
+		[YAML_STREAM_START_EVENT]	= "YAML_STREAM_START_EVENT",
+		[YAML_STREAM_END_EVENT]		= "YAML_STREAM_END_EVENT",
+		[YAML_DOCUMENT_START_EVENT]	= "YAML_DOCUMENT_START_EVENT",
+		[YAML_DOCUMENT_END_EVENT]	= "YAML_DOCUMENT_END_EVENT",
+		[YAML_ALIAS_EVENT]		= "YAML_ALIAS_EVENT",
+		[YAML_SCALAR_EVENT]		= "YAML_SCALAR_EVENT",
+		[YAML_SEQUENCE_START_EVENT]	= "YAML_SEQUENCE_START_EVENT",
+		[YAML_SEQUENCE_END_EVENT]	= "YAML_SEQUENCE_END_EVENT",
+		[YAML_MAPPING_START_EVENT]	= "YAML_MAPPING_START_EVENT",
+		[YAML_MAPPING_END_EVENT]	= "YAML_MAPPING_END_EVENT",
+	};
+
+	if (!event || event->type < 0 || event->type > ARRAY_SIZE(labels))
+		return "invalid YAML event";
+	return labels[event->type];
+}
+
+///@}
+
+/**
+ * @enum tlshd_tags_fsm_state_index
+ * YAML parser finite states
+ */
+enum tlshd_tags_fsm_state_index {
+	PS_STOP,
+	PS_START,
+	PS_STREAM,
+	PS_DOCUMENT,
+	PS_TOP_LEVEL,
+
+	PS_UNEXPECTED_INPUT_TOKEN,
+	PS_FAILURE,
+};
+
 struct tlshd_tags_filter;
 
 /**
@@ -53,6 +108,244 @@ struct tlshd_tags_filter_type {
  */
 static GHashTable *tlshd_tags_filter_type_hash;
 
+/**
+ * @struct tlshd_tags_parser_state
+ * @brief Global parser state
+ */
+struct tlshd_tags_parser_state {
+	yaml_event_t			ps_yaml_event;
+
+	enum tlshd_tags_fsm_state_index	ps_fsm_state;
+};
+
+static enum tlshd_tags_fsm_state_index
+tlshd_tags_top_level(struct tlshd_tags_parser_state *current)
+{
+	const yaml_event_t *event = &current->ps_yaml_event;
+	const char *mapping = (const char *)event->data.scalar.value;
+
+	tlshd_log_error("Unexpected mapping name: %s\n", mapping);
+	return PS_UNEXPECTED_INPUT_TOKEN;
+}
+
+/** @name tagsYamlFsm
+ *
+ * YAML parser finite state machine
+ */
+
+///@{
+
+typedef enum tlshd_tags_fsm_state_index
+	(*tlshd_tags_action_fn)(struct tlshd_tags_parser_state *current);
+
+/**
+ * @struct tlshd_tags_fsm_transition
+ * @brief One edge of the FSM transition graph
+ */
+struct tlshd_tags_fsm_transition {
+	yaml_event_type_t		pt_yaml_event;
+	enum tlshd_tags_fsm_state_index	pt_next_state;
+	tlshd_tags_action_fn		pt_action;
+};
+
+#define NEXT_STATE(event, state) \
+	{ \
+		.pt_yaml_event		= event, \
+		.pt_next_state		= state, \
+	}
+
+#define NEXT_ACTION(event, action) \
+	{ \
+		.pt_yaml_event		= event, \
+		.pt_action		= action, \
+	}
+
+static const struct tlshd_tags_fsm_transition tlshd_tags_transitions_start[] = {
+	NEXT_STATE(YAML_STREAM_START_EVENT, PS_STREAM),
+};
+
+static const struct tlshd_tags_fsm_transition tlshd_tags_transitions_stream[] = {
+	NEXT_STATE(YAML_DOCUMENT_START_EVENT, PS_DOCUMENT),
+	NEXT_STATE(YAML_STREAM_END_EVENT, PS_STOP),
+};
+
+static const struct tlshd_tags_fsm_transition tlshd_tags_transitions_document[] = {
+	NEXT_STATE(YAML_MAPPING_START_EVENT, PS_TOP_LEVEL),
+	NEXT_STATE(YAML_DOCUMENT_END_EVENT, PS_STREAM),
+};
+
+static const struct tlshd_tags_fsm_transition tlshd_tags_transitions_top_level[] = {
+	NEXT_ACTION(YAML_SCALAR_EVENT, tlshd_tags_top_level),
+	NEXT_STATE(YAML_MAPPING_END_EVENT, PS_DOCUMENT),
+};
+
+struct tlshd_tags_fsm_state {
+	const char			*ts_name;
+	const struct tlshd_tags_fsm_transition *ts_transitions;
+	size_t				ts_transition_count;
+};
+
+#define FSM_STATE(name, array) \
+	[name] = { \
+		.ts_name		= #name, \
+		.ts_transitions		= array, \
+		.ts_transition_count	= ARRAY_SIZE(array), \
+	}
+
+#define TERMINAL_STATE(name) \
+	[name] = { \
+		.ts_name		= #name, \
+		.ts_transition_count	= 0, \
+	}
+
+/**
+ * @var tlshd_tags_fsm_state_table
+ * @brief YAML parser finite state machine table
+ */
+static const struct tlshd_tags_fsm_state tlshd_tags_fsm_state_table[] = {
+	TERMINAL_STATE(PS_STOP),
+	FSM_STATE(PS_START, tlshd_tags_transitions_start),
+	FSM_STATE(PS_STREAM, tlshd_tags_transitions_stream),
+	FSM_STATE(PS_DOCUMENT, tlshd_tags_transitions_document),
+	FSM_STATE(PS_TOP_LEVEL, tlshd_tags_transitions_top_level),
+	TERMINAL_STATE(PS_UNEXPECTED_INPUT_TOKEN),
+	TERMINAL_STATE(PS_FAILURE),
+};
+
+/**
+ * @brief Process a YAML parsing event
+ * @param [in,out]  current  Current YAML parser state
+ *
+ * Each libyaml event produces zero or one input tokens.
+ * tlshd_tags_process_yaml_event() evaluates the event token based
+ * on the current parser state, then advances to the next FSM state.
+ */
+static void
+tlshd_tags_process_yaml_event(struct tlshd_tags_parser_state *current)
+{
+	const struct tlshd_tags_fsm_state *fsm_state =
+		&tlshd_tags_fsm_state_table[current->ps_fsm_state];
+	const yaml_event_t *event = &current->ps_yaml_event;
+	const struct tlshd_tags_fsm_transition *transition;
+	size_t i;
+
+	if (fsm_state->ts_transition_count == 0)
+		return;
+
+	transition = NULL;
+	for (i = 0; i < fsm_state->ts_transition_count; ++i) {
+		if (fsm_state->ts_transitions[i].pt_yaml_event == event->type) {
+			transition = &fsm_state->ts_transitions[i];
+			break;
+		}
+	}
+	if (transition == NULL) {
+		tlshd_log_debug("ps_state=%s, unexpected event: %s\n",
+			fsm_state->ts_name,
+			show_yaml_event_type(event));
+		current->ps_fsm_state = PS_FAILURE;
+		return;
+	}
+
+	if (tlshd_debug > 3)
+		tlshd_log_debug("ps_state=%s yaml event=%s",
+			fsm_state->ts_name,
+			show_yaml_event_type(event));
+
+	if (transition->pt_action)
+		current->ps_fsm_state = transition->pt_action(current);
+	else
+		current->ps_fsm_state = transition->pt_next_state;
+}
+
+/**
+ * @brief Read in one tag definition file
+ * @param[in]      filename pathname of file containing tag specifications
+ */
+static void tlshd_tags_parse_file(const char *filename)
+{
+	struct tlshd_tags_parser_state current;
+	yaml_parser_t parser;
+	FILE *fh;
+
+	if (!yaml_parser_initialize(&parser)) {
+		tlshd_log_error("Failed to initialize parser!\n");
+		return;
+	}
+
+	fh = fopen(filename, "r");
+	if (!fh) {
+		tlshd_log_perror("fopen");
+		yaml_parser_delete(&parser);
+		return;
+	}
+	yaml_parser_set_input_file(&parser, fh);
+
+	tlshd_log_debug("Parsing tags config file '%s'", filename);
+
+	current.ps_fsm_state = PS_START;
+	do {
+		if (!yaml_parser_parse(&parser, &current.ps_yaml_event)) {
+			tlshd_log_error("Parser error %d\n",
+					parser.error);
+			break;
+		}
+		tlshd_tags_process_yaml_event(&current);
+		yaml_event_delete(&current.ps_yaml_event);
+
+		if (current.ps_fsm_state == PS_FAILURE ||
+		    current.ps_fsm_state == PS_UNEXPECTED_INPUT_TOKEN) {
+			tlshd_log_error("Tag parsing failed, line: %zu column: %zu file: %s\n",
+					parser.mark.line + 1,
+					parser.mark.column,
+					filename);
+			break;
+		}
+	} while (current.ps_fsm_state != PS_STOP);
+
+	yaml_parser_delete(&parser);
+	fclose(fh);
+}
+
+/**
+ * @brief Read all the tag definition files in one directory
+ * @param[in]      tagsdir pathname of directory containing files that define tags
+ *
+ * @retval true   Directory has been read without a permanent error
+ * @retval false  A permanent error occurred
+ */
+static bool tlshd_tags_read_directory(const char *tagsdir)
+{
+	const gchar *filename;
+	GError *error;
+	GDir *dir;
+
+	error = NULL;
+	dir = g_dir_open(tagsdir, 0, &error);
+	if (!dir) {
+		tlshd_log_gerror("Failed to open the tags directory", error);
+		g_error_free(error);
+		return false;
+	}
+
+	while ((filename = g_dir_read_name(dir)) != NULL) {
+		gchar *pathname;
+
+		if (!g_str_has_suffix(filename, ".yml") &&
+		    !g_str_has_suffix(filename, ".yaml"))
+			continue;
+		pathname = g_build_filename(tagsdir, filename, NULL);
+
+		tlshd_tags_parse_file(pathname);
+		g_free(pathname);
+	}
+
+	g_dir_close(dir);
+	return true;
+}
+
+///@}
+
 /** @name tagsFilterTypes
  *
  * Add tag filter types to a hash table for fast lookup by type name.
@@ -183,9 +476,20 @@ static bool tlshd_tags_filter_type_hash_init(void)
  * @retval true   Subsystem initialization succeeded
  * @retval false  Subsystem initialization failed
  */
-bool tlshd_tags_config_init(__attribute__ ((unused)) const char *tagsdir)
+bool tlshd_tags_config_init(const char *tagsdir)
 {
-	return tlshd_tags_filter_type_hash_init();
+	if (!tlshd_tags_filter_type_hash_init())
+		goto out;
+
+	if (!tlshd_tags_read_directory(tagsdir))
+		goto filter_type_hash;
+
+	return true;
+
+filter_type_hash:
+	tlshd_tags_filter_type_hash_destroy();
+out:
+	return false;
 }
 
 /**