common: validate and properly parse floats

Fixes: #1665.

include/common/parse-double.h

@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef LABWC_PARSE_DOUBLE_H
+#define LABWC_PARSE_DOUBLE_H
+#include <assert.h>
+#include <stdbool.h>
+
+/**
+ * set_double() - Parse double-precision value of string.
+ * @str: String to parse
+ * @val: Storage for parsed value
+ *
+ * Return: true if string was parsed, false if not
+ *
+ * NOTE: If this function returns false, the value at *val will be untouched.
+ */
+bool set_double(const char *str, double *val);
+
+static inline bool
+set_float(const char *str, float *val)
+{
+	assert(val);
+
+	double d;
+	if (set_double(str, &d)) {
+		*val = d;
+		return true;
+	}
+
+	return false;
+}
+
+#endif /* LABWC_PARSE_DOUBLE_H */

src/common/meson.build

@@ -10,6 +10,7 @@ labwc_sources += files(
   'mem.c',
   'nodename.c',
   'parse-bool.c',
+  'parse-double.c',
   'scaled_font_buffer.c',
   'scaled_scene_buffer.c',
   'scene-helpers.c',

src/common/parse-double.c

@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <locale.h>
+#include <stdlib.h>
+#include <string.h>
+#include <wlr/util/log.h>
+#include "common/mem.h"
+#include "common/parse-double.h"
+
+struct dec_separator {
+	int index;
+	bool multiple;
+};
+
+struct converted_double {
+	double value;
+	bool valid;
+};
+
+static struct dec_separator
+find_dec_separator(const char *str)
+{
+	struct dec_separator loc = {
+		.index = -1,
+		.multiple = false
+	};
+
+	for (int i = 0; *str; i++, str++) {
+		switch (*str) {
+		case ',':
+		case '.':
+			if (loc.index >= 0) {
+				loc.multiple = true;
+				return loc;
+			} else {
+				loc.index = i;
+			}
+			break;
+		}
+	}
+
+	return loc;
+}
+
+static struct converted_double
+convert_double(const char *str)
+{
+	struct converted_double result = {
+		.value = 0,
+		.valid = true,
+	};
+
+	char *eptr = NULL;
+
+	errno = 0;
+	result.value = strtod(str, &eptr);
+
+	if (errno) {
+		wlr_log(WLR_ERROR, "value '%s' is out of range", str);
+		result.valid = false;
+	}
+
+	if (*eptr) {
+		wlr_log(WLR_ERROR, "value '%s' contains trailing garbage", str);
+		result.valid = false;
+	}
+
+	return result;
+}
+
+bool
+set_double(const char *str, double *val)
+{
+	assert(str);
+	assert(val);
+
+	struct dec_separator dloc = find_dec_separator(str);
+	if (dloc.multiple) {
+		wlr_log(WLR_ERROR,
+			"value '%s' contains multiple decimal markers", str);
+		return false;
+	}
+
+	char *lstr = NULL;
+
+	if (dloc.index >= 0) {
+		lstr = xstrdup(str);
+		struct lconv *lc = localeconv();
+		lstr[dloc.index] = *lc->decimal_point;
+		str = lstr;
+	}
+
+	struct converted_double conv = convert_double(str);
+	if (conv.valid) {
+		*val = conv.value;
+	}
+
+	free(lstr);
+	return conv.valid;
+}

src/config/rcxml.c

@@ -21,6 +21,7 @@
 #include "common/mem.h"
 #include "common/nodename.h"
 #include "common/parse-bool.h"
+#include "common/parse-double.h"
 #include "common/string-helpers.h"
 #include "config/default-bindings.h"
 #include "config/keybind.h"
@@ -537,7 +538,7 @@ fill_libinput_category(char *nodename, char *content)
 	} else if (!strcasecmp(nodename, "leftHanded")) {
 		set_bool_as_int(content, &current_libinput_category->left_handed);
 	} else if (!strcasecmp(nodename, "pointerSpeed")) {
-		current_libinput_category->pointer_speed = atof(content);
+		set_float(content, &current_libinput_category->pointer_speed);
 		if (current_libinput_category->pointer_speed < -1) {
 			current_libinput_category->pointer_speed = -1;
 		} else if (current_libinput_category->pointer_speed > 1) {
@@ -883,7 +884,7 @@ entry(xmlNode *node, char *nodename, char *content)
 			wlr_log(WLR_ERROR, "invalid doubleClickTime");
 		}
 	} else if (!strcasecmp(nodename, "scrollFactor.mouse")) {
-		rc.scroll_factor = atof(content);
+		set_double(content, &rc.scroll_factor);
 	} else if (!strcasecmp(nodename, "name.context.mouse")) {
 		current_mouse_context = content;
 		current_mousebind = NULL;

src/config/tablet.c

@@ -4,6 +4,7 @@
 #include <stdint.h>
 #include <strings.h>
 #include <wlr/util/log.h>
+#include "common/parse-double.h"
 #include "config/tablet.h"
 #include "config/rcxml.h"
 #include "input/tablet_pad.h"
@@ -11,7 +12,8 @@
 double
 tablet_get_dbl_if_positive(const char *content, const char *name)
 {
-	double value = atof(content);
+	double value = 0;
+	set_double(content, &value);
 	if (value < 0) {
 		wlr_log(WLR_ERROR, "Invalid value for tablet area %s", name);
 		return 0;