Add system view pg_ident_file_mappings

This view is similar to pg_hba_file_rules view, except that it is
associated with the parsing of pg_ident.conf.  Similarly to its cousin,
this view is useful to check via SQL if changes planned in pg_ident.conf
would work upon reload or restart, or to diagnose a previous failure.

Bumps catalog version.

Author: Julien Rouhaud
Reviewed-by: Aleksander Alekseev, Michael Paquier
Discussion: https://postgr.es/m/20220223045959.35ipdsvbxcstrhya@jrouhaud

src/backend/catalog/system_views.sql

@@ -617,6 +617,12 @@ CREATE VIEW pg_hba_file_rules AS
 REVOKE ALL ON pg_hba_file_rules FROM PUBLIC;
 REVOKE EXECUTE ON FUNCTION pg_hba_file_rules() FROM PUBLIC;
 
+CREATE VIEW pg_ident_file_mappings AS
+   SELECT * FROM pg_ident_file_mappings() AS A;
+
+REVOKE ALL ON pg_ident_file_mappings FROM PUBLIC;
+REVOKE EXECUTE ON FUNCTION pg_ident_file_mappings() FROM PUBLIC;
+
 CREATE VIEW pg_timezone_abbrevs AS
     SELECT * FROM pg_timezone_abbrevs();
 

src/backend/libpq/hba.c

@@ -887,25 +887,22 @@ do { \
 } while (0)
 
 /*
- * Macros for handling pg_ident problems.
- * Much as above, but currently the message level is hardwired as LOG
- * and there is no provision for an err_msg string.
+ * Macros for handling pg_ident problems, similar as above.
  *
  * IDENT_FIELD_ABSENT:
- * Log a message and exit the function if the given ident field ListCell is
- * not populated.
+ * Reports when the given ident field ListCell is not populated.
  *
  * IDENT_MULTI_VALUE:
- * Log a message and exit the function if the given ident token List has more
- * than one element.
+ * Reports when the given ident token List has more than one element.
  */
 #define IDENT_FIELD_ABSENT(field) \
 do { \
 	if (!field) { \
-		ereport(LOG, \
+		ereport(elevel, \
 				(errcode(ERRCODE_CONFIG_FILE_ERROR), \
 				 errmsg("missing entry in file \"%s\" at end of line %d", \
 						IdentFileName, line_num))); \
+		*err_msg = psprintf("missing entry at end of line"); \
 		return NULL; \
 	} \
 } while (0)
@@ -913,11 +910,12 @@ do { \
 #define IDENT_MULTI_VALUE(tokens) \
 do { \
 	if (tokens->length > 1) { \
-		ereport(LOG, \
+		ereport(elevel, \
 				(errcode(ERRCODE_CONFIG_FILE_ERROR), \
 				 errmsg("multiple values in ident field"), \
 				 errcontext("line %d of configuration file \"%s\"", \
 							line_num, IdentFileName))); \
+		*err_msg = psprintf("multiple values in ident field"); \
 		return NULL; \
 	} \
 } while (0)
@@ -2306,7 +2304,8 @@ load_hba(void)
  * Parse one tokenised line from the ident config file and store the result in
  * an IdentLine structure.
  *
- * If parsing fails, log a message and return NULL.
+ * If parsing fails, log a message at ereport level elevel, store an error
+ * string in tok_line->err_msg and return NULL.
  *
  * If ident_user is a regular expression (ie. begins with a slash), it is
  * compiled and stored in IdentLine structure.
@@ -2315,10 +2314,11 @@ load_hba(void)
  * to have set a memory context that will be reset if this function returns
  * NULL.
  */
-static IdentLine *
-parse_ident_line(TokenizedAuthLine *tok_line)
+IdentLine *
+parse_ident_line(TokenizedAuthLine *tok_line, int elevel)
 {
 	int			line_num = tok_line->line_num;
+	char	  **err_msg = &tok_line->err_msg;
 	ListCell   *field;
 	List	   *tokens;
 	AuthToken  *token;
@@ -2372,11 +2372,14 @@ parse_ident_line(TokenizedAuthLine *tok_line)
 			char		errstr[100];
 
 			pg_regerror(r, &parsedline->re, errstr, sizeof(errstr));
-			ereport(LOG,
+			ereport(elevel,
 					(errcode(ERRCODE_INVALID_REGULAR_EXPRESSION),
 					 errmsg("invalid regular expression \"%s\": %s",
 							parsedline->ident_user + 1, errstr)));
 
+			*err_msg = psprintf("invalid regular expression \"%s\": %s",
+								parsedline->ident_user + 1, errstr);
+
 			pfree(wstr);
 			return NULL;
 		}
@@ -2627,7 +2630,7 @@ load_ident(void)
 			continue;
 		}
 
-		if ((newline = parse_ident_line(tok_line)) == NULL)
+		if ((newline = parse_ident_line(tok_line, LOG)) == NULL)
 		{
 			/* Parse error; remember there's trouble */
 			ok = false;

src/backend/utils/adt/hbafuncs.c

@@ -28,6 +28,9 @@ static ArrayType *get_hba_options(HbaLine *hba);
 static void fill_hba_line(Tuplestorestate *tuple_store, TupleDesc tupdesc,
 						  int lineno, HbaLine *hba, const char *err_msg);
 static void fill_hba_view(Tuplestorestate *tuple_store, TupleDesc tupdesc);
+static void fill_ident_line(Tuplestorestate *tuple_store, TupleDesc tupdesc,
+							int lineno, IdentLine *ident, const char *err_msg);
+static void fill_ident_view(Tuplestorestate *tuple_store, TupleDesc tupdesc);
 
 
 /*
@@ -426,3 +429,136 @@ pg_hba_file_rules(PG_FUNCTION_ARGS)
 
 	PG_RETURN_NULL();
 }
+
+/* Number of columns in pg_ident_file_mappings view */
+#define NUM_PG_IDENT_FILE_MAPPINGS_ATTS	 5
+
+/*
+ * fill_ident_line: build one row of pg_ident_file_mappings view, add it to
+ * tuplestore
+ *
+ * tuple_store: where to store data
+ * tupdesc: tuple descriptor for the view
+ * lineno: pg_ident.conf line number (must always be valid)
+ * ident: parsed line data (can be NULL, in which case err_msg should be set)
+ * err_msg: error message (NULL if none)
+ *
+ * Note: leaks memory, but we don't care since this is run in a short-lived
+ * memory context.
+ */
+static void
+fill_ident_line(Tuplestorestate *tuple_store, TupleDesc tupdesc,
+				int lineno, IdentLine *ident, const char *err_msg)
+{
+	Datum		values[NUM_PG_IDENT_FILE_MAPPINGS_ATTS];
+	bool		nulls[NUM_PG_IDENT_FILE_MAPPINGS_ATTS];
+	HeapTuple	tuple;
+	int			index;
+
+	Assert(tupdesc->natts == NUM_PG_IDENT_FILE_MAPPINGS_ATTS);
+
+	memset(values, 0, sizeof(values));
+	memset(nulls, 0, sizeof(nulls));
+	index = 0;
+
+	/* line_number */
+	values[index++] = Int32GetDatum(lineno);
+
+	if (ident != NULL)
+	{
+		values[index++] = CStringGetTextDatum(ident->usermap);
+		values[index++] = CStringGetTextDatum(ident->ident_user);
+		values[index++] = CStringGetTextDatum(ident->pg_role);
+	}
+	else
+	{
+		/* no parsing result, so set relevant fields to nulls */
+		memset(&nulls[1], true, (NUM_PG_IDENT_FILE_MAPPINGS_ATTS - 2) * sizeof(bool));
+	}
+
+	/* error */
+	if (err_msg)
+		values[NUM_PG_IDENT_FILE_MAPPINGS_ATTS - 1] = CStringGetTextDatum(err_msg);
+	else
+		nulls[NUM_PG_IDENT_FILE_MAPPINGS_ATTS - 1] = true;
+
+	tuple = heap_form_tuple(tupdesc, values, nulls);
+	tuplestore_puttuple(tuple_store, tuple);
+}
+
+/*
+ * Read the pg_ident.conf file and fill the tuplestore with view records.
+ */
+static void
+fill_ident_view(Tuplestorestate *tuple_store, TupleDesc tupdesc)
+{
+	FILE	   *file;
+	List	   *ident_lines = NIL;
+	ListCell   *line;
+	MemoryContext linecxt;
+	MemoryContext identcxt;
+	MemoryContext oldcxt;
+
+	/*
+	 * In the unlikely event that we can't open pg_ident.conf, we throw an
+	 * error, rather than trying to report it via some sort of view entry.
+	 * (Most other error conditions should result in a message in a view
+	 * entry.)
+	 */
+	file = AllocateFile(IdentFileName, "r");
+	if (file == NULL)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not open usermap file \"%s\": %m",
+						IdentFileName)));
+
+	linecxt = tokenize_auth_file(HbaFileName, file, &ident_lines, DEBUG3);
+	FreeFile(file);
+
+	/* Now parse all the lines */
+	identcxt = AllocSetContextCreate(CurrentMemoryContext,
+									 "ident parser context",
+									 ALLOCSET_SMALL_SIZES);
+	oldcxt = MemoryContextSwitchTo(identcxt);
+	foreach(line, ident_lines)
+	{
+		TokenizedAuthLine *tok_line = (TokenizedAuthLine *) lfirst(line);
+		IdentLine  *identline = NULL;
+
+		/* don't parse lines that already have errors */
+		if (tok_line->err_msg == NULL)
+			identline = parse_ident_line(tok_line, DEBUG3);
+
+		fill_ident_line(tuple_store, tupdesc, tok_line->line_num, identline,
+						tok_line->err_msg);
+	}
+
+	/* Free tokenizer memory */
+	MemoryContextDelete(linecxt);
+	/* Free parse_ident_line memory */
+	MemoryContextSwitchTo(oldcxt);
+	MemoryContextDelete(identcxt);
+}
+
+/*
+ * SQL-accessible SRF to return all the entries in the pg_ident.conf file.
+ */
+Datum
+pg_ident_file_mappings(PG_FUNCTION_ARGS)
+{
+	ReturnSetInfo *rsi;
+
+	/*
+	 * Build tuplestore to hold the result rows.  We must use the Materialize
+	 * mode to be safe against HBA file changes while the cursor is open. It's
+	 * also more efficient than having to look up our current position in the
+	 * parsed list every time.
+	 */
+	SetSingleFuncCall(fcinfo, 0);
+
+	/* Fill the tuplestore */
+	rsi = (ReturnSetInfo *) fcinfo->resultinfo;
+	fill_ident_view(rsi->setResult, rsi->setDesc);
+
+	PG_RETURN_NULL();
+}

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202203272
+#define CATALOG_VERSION_NO	202203291
 
 #endif

src/include/catalog/pg_proc.dat

@@ -6115,6 +6115,12 @@
   proargmodes => '{o,o,o,o,o,o,o,o,o}',
   proargnames => '{line_number,type,database,user_name,address,netmask,auth_method,options,error}',
   prosrc => 'pg_hba_file_rules' },
+{ oid => '9556', descr => 'show pg_ident.conf mappings',
+  proname => 'pg_ident_file_mappings', prorows => '1000', proretset => 't',
+  provolatile => 'v', prorettype => 'record', proargtypes => '',
+  proallargtypes => '{int4,text,text,text,text}', proargmodes => '{o,o,o,o,o}',
+  proargnames => '{line_number,map_name,sys_name,pg_username,error}',
+  prosrc => 'pg_ident_file_mappings' },
 { oid => '1371', descr => 'view system lock information',
   proname => 'pg_lock_status', prorows => '1000', proretset => 't',
   provolatile => 'v', prorettype => 'record', proargtypes => '',

src/include/libpq/hba.h

@@ -171,6 +171,7 @@ extern int	check_usermap(const char *usermap_name,
 						  const char *pg_role, const char *auth_user,
 						  bool case_sensitive);
 extern HbaLine *parse_hba_line(TokenizedAuthLine *tok_line, int elevel);
+extern IdentLine *parse_ident_line(TokenizedAuthLine *tok_line, int elevel);
 extern bool pg_isblank(const char c);
 extern MemoryContext tokenize_auth_file(const char *filename, FILE *file,
 										List **tok_lines, int elevel);

src/test/regress/expected/rules.out

@@ -1347,6 +1347,12 @@ pg_hba_file_rules| SELECT a.line_number,
     a.options,
     a.error
    FROM pg_hba_file_rules() a(line_number, type, database, user_name, address, netmask, auth_method, options, error);
+pg_ident_file_mappings| SELECT a.line_number,
+    a.map_name,
+    a.sys_name,
+    a.pg_username,
+    a.error
+   FROM pg_ident_file_mappings() a(line_number, map_name, sys_name, pg_username, error);
 pg_indexes| SELECT n.nspname AS schemaname,
     c.relname AS tablename,
     i.relname AS indexname,

src/test/regress/expected/sysviews.out

@@ -56,6 +56,14 @@ select count(*) > 0 as ok, count(*) FILTER (WHERE error IS NOT NULL) = 0 AS no_e
  t  | t
 (1 row)
 
+-- There may be no rules, and there should be no errors.
+select count(*) >= 0 as ok, count(*) FILTER (WHERE error IS NOT NULL) = 0 AS no_err
+  from pg_ident_file_mappings;
+ ok | no_err 
+----+--------
+ t  | t
+(1 row)
+
 -- There will surely be at least one active lock
 select count(*) > 0 as ok from pg_locks;
  ok 

src/test/regress/sql/sysviews.sql

@@ -29,6 +29,10 @@ select count(*) >= 0 as ok from pg_file_settings;
 select count(*) > 0 as ok, count(*) FILTER (WHERE error IS NOT NULL) = 0 AS no_err
   from pg_hba_file_rules;
 
+-- There may be no rules, and there should be no errors.
+select count(*) >= 0 as ok, count(*) FILTER (WHERE error IS NOT NULL) = 0 AS no_err
+  from pg_ident_file_mappings;
+
 -- There will surely be at least one active lock
 select count(*) > 0 as ok from pg_locks;