xenconsole: add option to avoid escape sequences in log

Add --replace-escape option to xenconsoled, which replaces ESC with
'.' in console output written to log file. This makes it slightly safer
to do tail -f on a console output of untrusted guest.
The pty output is unaffected by this option.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
[ wei: move variables into a narrower scope ]
Signed-off-by: Wei Liu <wei.liu2@citrix.com>

tools/console/daemon/io.c

@@ -68,6 +68,7 @@ extern int log_time_hv;
 extern int log_time_guest;
 extern char *log_dir;
 extern int discard_overflowed_data;
+extern int replace_escape;
 
 static int log_time_hv_needts = 1;
 static int log_time_guest_needts = 1;
@@ -227,10 +228,34 @@ static inline int console_iter_int_arg3(struct domain *d,
 	return ret;
 }
 
+static void do_replace_escape(const char *src, char *dest, int len)
+{
+	int i;
+
+	for (i = 0; i < len; i++) {
+		if (src[i] == '\033')
+			dest[i] = '.';
+		else
+			dest[i] = src[i];
+	}
+}
+
 static int write_all(int fd, const char* buf, size_t len)
 {
 	while (len) {
-		ssize_t ret = write(fd, buf, len);
+		ssize_t ret;
+		if (replace_escape) {
+			char buf_replaced[1024];
+			size_t this_round;
+
+			if (len > sizeof(buf_replaced))
+				this_round = sizeof(buf_replaced);
+			else
+				this_round = len;
+			do_replace_escape(buf, buf_replaced, this_round);
+			ret = write(fd, buf_replaced, this_round);
+		} else
+			ret = write(fd, buf, len);
 		if (ret == -1 && errno == EINTR)
 			continue;
 		if (ret <= 0)

tools/console/daemon/main.c

@@ -40,6 +40,7 @@ int log_time_hv = 0;
 int log_time_guest = 0;
 char *log_dir = NULL;
 int discard_overflowed_data = 1;
+int replace_escape = 0;
 
 static void handle_hup(int sig)
 {
@@ -48,7 +49,8 @@ static void handle_hup(int sig)
 
 static void usage(char *name)
 {
-	printf("Usage: %s [-h] [-V] [-v] [-i] [--log=none|guest|hv|all] [--log-dir=DIR] [--pid-file=PATH] [-t, --timestamp=none|guest|hv|all] [-o, --overflow-data=discard|keep]\n", name);
+	printf("Usage: %s [-h] [-V] [-v] [-i] [--log=none|guest|hv|all] [--log-dir=DIR] [--pid-file=PATH] [-t, --timestamp=none|guest|hv|all] [-o, --overflow-data=discard|keep] [--replace-escape]\n", name);
+	printf("  --replace-escape  - replace ESC character with dot when writing console log\n");
 }
 
 static void version(char *name)
@@ -104,6 +106,7 @@ int main(int argc, char **argv)
 		{ "pid-file", 1, 0, 'p' },
 		{ "timestamp", 1, 0, 't' },
 		{ "overflow-data", 1, 0, 'o'},
+		{ "replace-escape", 0, 0, 'e'},
 		{ 0 },
 	};
 	bool is_interactive = false;
@@ -168,6 +171,9 @@ int main(int argc, char **argv)
 				discard_overflowed_data = 1;
 			}
 			break;
+		case 'e':
+			replace_escape = 1;
+			break;
 		case '?':
 			fprintf(stderr,
 				"Try `%s --help' for more information\n",