config: Fix ast_config_text_file_save writability check for missing files

A patch I did back in 2014 modified ast_config_text_file_save to check the
writability of the main file and include files before truncating and re-writing
them.  An unintended side-effect of this was that if a file doesn't exist,
the check fails and the write is aborted.

This patch causes ast_config_text_file_save to check the writability of the
parent directory of missing files instead of checking the file itself.  This
allows missing files to be created again.  A unit test was also added to
test_config to test saving of config files.

The regression was discovered when app_voicemail's passwordlocation=spooldir
feature stopped working.

ASTERISK-25917 #close
Reported-by: Jonathan Rose

Change-Id: Ic4dbe58c277a47b674679e49daed5fc6de349f80

main/config.c

@@ -39,6 +39,8 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #include <time.h>
 #include <sys/stat.h>
 
+#include <string.h>
+#include <libgen.h>
 #include <math.h>	/* HUGE_VAL */
 
 #define AST_INCLUDE_GLOB 1
@@ -2128,6 +2130,25 @@ int config_text_file_save(const char *configfile, const struct ast_config *cfg,
 	return ast_config_text_file_save(configfile, cfg, generator);
 }
 
+static int is_writable(const char *fn)
+{
+	if (access(fn, F_OK)) {
+		char *dn = dirname(ast_strdupa(fn));
+
+		if (access(dn, R_OK | W_OK)) {
+			ast_log(LOG_ERROR, "Unable to write to directory %s (%s)\n", dn, strerror(errno));
+			return 0;
+		}
+	} else {
+		if (access(fn, R_OK | W_OK)) {
+			ast_log(LOG_ERROR, "Unable to write %s (%s)\n", fn, strerror(errno));
+			return 0;
+		}
+	}
+
+	return 1;
+}
+
 int ast_config_text_file_save(const char *configfile, const struct ast_config *cfg, const char *generator)
 {
 	FILE *f;
@@ -2150,20 +2171,20 @@ int ast_config_text_file_save(const char *configfile, const struct ast_config *c
 	for (incl = cfg->includes; incl; incl = incl->next) {
 		/* reset all the output flags in case this isn't our first time saving this data */
 		incl->output = 0;
-		/* now make sure we have write access */
+
 		if (!incl->exec) {
+			/* now make sure we have write access to the include file or its parent directory */
 			make_fn(fn, sizeof(fn), incl->included_file, configfile);
-			if (access(fn, R_OK | W_OK)) {
-				ast_log(LOG_ERROR, "Unable to write %s (%s)\n", fn, strerror(errno));
+			/* If the file itself doesn't exist, make sure we have write access to the directory */
+			if (!is_writable(fn)) {
 				return -1;
 			}
 		}
 	}
 
-	/* now make sure we have write access to the main config file */
+	/* now make sure we have write access to the main config file or its parent directory */
 	make_fn(fn, sizeof(fn), 0, configfile);
-	if (access(fn, R_OK | W_OK)) {
-		ast_log(LOG_ERROR, "Unable to write %s (%s)\n", fn, strerror(errno));
+	if (!is_writable(fn)) {
 		return -1;
 	}
 

tests/test_config.c

@@ -34,6 +34,7 @@
 ASTERISK_FILE_VERSION(__FILE__, "$Revision$");
 
 #include <math.h> /* HUGE_VAL */
+#include <sys/stat.h>
 
 #include "asterisk/config.h"
 #include "asterisk/module.h"
@@ -47,6 +48,7 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$");
 #include "asterisk/logger.h"
 
 #define CONFIG_FILE "test_config.conf"
+#define CONFIG_INCLUDE_FILE "test_config_include.conf"
 
 /*
  * This builds the folowing config:
@@ -293,6 +295,77 @@ static int hook_cb(struct ast_config *cfg)
 	return 0;
 }
 
+AST_TEST_DEFINE(config_save)
+{
+	enum ast_test_result_state res = AST_TEST_FAIL;
+	struct ast_flags config_flags = { 0 };
+	struct ast_config *cfg;
+	char config_filename[PATH_MAX];
+	char include_filename[PATH_MAX];
+	struct stat config_stat;
+	off_t before_save;
+
+	switch (cmd) {
+	case TEST_INIT:
+		info->name = "config_save";
+		info->category = "/main/config/";
+		info->summary = "Test config save";
+		info->description =
+			"Test configuration save.";
+		return AST_TEST_NOT_RUN;
+	case TEST_EXECUTE:
+		break;
+	}
+
+	if (write_config_file()) {
+		ast_test_status_update(test, "Could not write initial config files\n");
+		return res;
+	}
+
+	snprintf(config_filename, PATH_MAX, "%s/%s", ast_config_AST_CONFIG_DIR, CONFIG_FILE);
+	snprintf(include_filename, PATH_MAX, "%s/%s", ast_config_AST_CONFIG_DIR, CONFIG_INCLUDE_FILE);
+
+	cfg = ast_config_load(CONFIG_FILE, config_flags);
+	if (!cfg) {
+		ast_test_status_update(test, "Could not load config\n");
+		goto out;
+	}
+
+	/* We need to re-save to get the generator header */
+	if (ast_config_text_file_save(CONFIG_FILE, cfg, "TEST")) {
+		ast_test_status_update(test, "Unable to write files\n");
+		goto out;
+	}
+
+	stat(config_filename, &config_stat);
+	before_save = config_stat.st_size;
+
+	if (!ast_include_new(cfg, CONFIG_FILE, CONFIG_INCLUDE_FILE, 0, NULL, 4, include_filename, PATH_MAX)) {
+		ast_test_status_update(test, "Could not create include\n");
+		goto out;
+	}
+
+	if (ast_config_text_file_save(CONFIG_FILE, cfg, "TEST")) {
+		ast_test_status_update(test, "Unable to write files\n");
+		goto out;
+	}
+
+	stat(config_filename, &config_stat);
+	if (config_stat.st_size <= before_save) {
+		ast_test_status_update(test, "Did not save config file with #include\n");
+		goto out;
+	}
+
+	res = AST_TEST_PASS;
+
+out:
+	ast_config_destroy(cfg);
+	unlink(config_filename);
+	unlink(include_filename);
+
+	return res;
+}
+
 AST_TEST_DEFINE(config_hook)
 {
 	enum ast_test_result_state res = AST_TEST_FAIL;
@@ -934,6 +1007,7 @@ AST_TEST_DEFINE(config_options_test)
 
 static int unload_module(void)
 {
+	AST_TEST_UNREGISTER(config_save);
 	AST_TEST_UNREGISTER(copy_config);
 	AST_TEST_UNREGISTER(config_hook);
 	AST_TEST_UNREGISTER(ast_parse_arg_test);
@@ -943,6 +1017,7 @@ static int unload_module(void)
 
 static int load_module(void)
 {
+	AST_TEST_REGISTER(config_save);
 	AST_TEST_REGISTER(copy_config);
 	AST_TEST_REGISTER(config_hook);
 	AST_TEST_REGISTER(ast_parse_arg_test);