Fix possible illegal memory access

Coverity says:
"CID 47629 (#1 of 1): Buffer not null terminated
(BUFFER_SIZE_WARNING)11. buffer_size_warning: Calling strncpy with a
maximum size argument of 255 bytes on destination array
config->configfile of size 255 bytes might leave the destination string
unterminated."

Instead of strncpy, the code now uses safe_strdup. This also lifts the
255 characters limit. While file names are indeed limitted to 255
chars on some file systems, path length is typically unlimitted.

Author: mhaas

src/commandline.c

@@ -106,7 +106,7 @@ void parse_commandline(int argc, char **argv) {
 
 			case 'c':
 				if (optarg) {
-					strncpy(config->configfile, optarg, sizeof(config->configfile));
+					config->configfile = safe_strdup(optarg);
 				}
 				break;
 

src/conf.c

@@ -170,7 +170,7 @@ void
 config_init(void)
 {
     debug(LOG_DEBUG, "Setting default config parameters");
-    strncpy(config.configfile, DEFAULT_CONFIGFILE, sizeof(config.configfile));
+    config.configfile = safe_strdup(DEFAULT_CONFIGFILE);
     config.htmlmsgfile = safe_strdup(DEFAULT_HTMLMSGFILE);
     config.debuglevel = DEFAULT_DEBUGLEVEL;
     config.httpdmaxconn = DEFAULT_HTTPDMAXCONN;

src/conf.h

@@ -147,7 +147,7 @@ typedef struct _trusted_mac_t {
  * Configuration structure
  */
 typedef struct {
-    char configfile[255];       /**< @brief name of the config file */
+    char *configfile;       /**< @brief name of the config file */
     char *htmlmsgfile;          /**< @brief name of the HTML file used for messages */
     char *wdctl_sock;           /**< @brief wdctl path to socket */
     char *internal_sock;                /**< @brief internal path to socket */