Add snprintf_safe() and sprintf_safe helpers

Blows up when sprintf encounters an error, the result string is empty or the
result string is truncated.

Note: sprintf_safe only works on static buffers, it uses ARRAY_LENGTH.

Fixes #14

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

src/hidpp20.c

@@ -63,7 +63,7 @@ hidpp20_feature_get_name(uint16_t feature)
 	CASE_RETURN_STRING(HIDPP_PAGE_ONBOARD_PROFILES);
 	CASE_RETURN_STRING(HIDPP_PAGE_MOUSE_BUTTON_SPY);
 	default:
-		sprintf(numeric, "%#4x", feature);
+		sprintf_safe(numeric, "%#4x", feature);
 		str = numeric;
 		break;
 	}

src/libratbag-util.h

@@ -25,6 +25,7 @@
 #define LIBRATBAG_UTIL_H
 
 #include <stdlib.h>
+#include <stdio.h>
 #include <string.h>
 #include <unistd.h>
 #include <libudev.h>
@@ -117,6 +118,25 @@ strdup_safe(const char *str)
 	return s;
 }
 
+static inline int
+snprintf_safe(char *buf, size_t n, const char *fmt, ...)
+{
+	va_list args;
+	int rc;
+
+	va_start(args, fmt);
+	rc = vsnprintf(buf, n, fmt, args);
+	va_end(args);
+
+	if (rc < 0 || n < (size_t)rc)
+		abort();
+
+	return rc;
+}
+
+#define sprintf_safe(buf, fmt, ...) \
+	snprintf_safe(buf, ARRAY_LENGTH(buf), fmt, __VA_ARGS__)
+
 static inline void
 msleep(unsigned int ms)
 {

src/libratbag.c

@@ -106,10 +106,10 @@ log_buffer(struct ratbag *ratbag,
 	output_buf = zalloc(buf_len);
 	n = 0;
 	if (header)
-		n += sprintf(output_buf, "%s", header);
+		n += snprintf_safe(output_buf, buf_len - n, "%s", header);
 
 	for (i = 0; i < len; ++i) {
-		n += sprintf(&output_buf[n], "%s%02x", sep, buf[i] & 0xFF);
+		n += snprintf_safe(&output_buf[n], buf_len - n, "%s%02x", sep, buf[i] & 0xFF);
 		sep = " ";
 	}
 

tools/ratbag-command.c

@@ -706,7 +706,7 @@ ratbag_cmd_list_supported_devices(const struct ratbag_cmd *cmd,
 
 	i = -1;
 	while (++i < n) {
-		sprintf(path, "/dev/input/%s", input_list[i]->d_name);
+		sprintf_safe(path, "/dev/input/%s", input_list[i]->d_name);
 		device = ratbag_cmd_open_device(ratbag, path);
 		if (device) {
 			printf("%s:\t%s\n", path, ratbag_device_get_name(device));

tools/shared.c

@@ -129,7 +129,7 @@ button_action_button_to_str(struct ratbag_button *button)
 {
 	char str[96];
 
-	sprintf(str, "button %d", ratbag_button_get_button(button));
+	sprintf_safe(str, "button %d", ratbag_button_get_button(button));
 
 	return strdup_safe(str);
 }