trivial: Add a fu_memread_uint24_safe() to make some code more correct

libfwupdplugin/fu-efi-firmware-section.c

@@ -123,14 +123,13 @@ fu_efi_firmware_section_parse(FuFirmware *firmware,
 	const guint8 *buf = g_bytes_get_data(fw, &bufsz);
 	g_autoptr(GBytes) blob = NULL;
 
-	if (!fu_memread_uint32_safe(buf,
-				    bufsz, /* uint24_t! */
+	if (!fu_memread_uint24_safe(buf,
+				    bufsz,
 				    FU_EFI_FIRMWARE_SECTION_OFFSET_SIZE,
 				    &size,
 				    G_LITTLE_ENDIAN,
 				    error))
 		return FALSE;
-	size &= 0xFFFFFF;
 	if (size < FU_EFI_FIRMWARE_SECTION_SIZE) {
 		g_set_error(error,
 			    FWUPD_ERROR,

libfwupdplugin/fu-mem.c

@@ -578,6 +578,52 @@ fu_memread_uint16_safe(const guint8 *buf,
 	return TRUE;
 }
 
+/**
+ * fu_memread_uint24_safe:
+ * @buf: source buffer
+ * @bufsz: maximum size of @buf, typically `sizeof(buf)`
+ * @offset: offset in bytes into @buf to copy from
+ * @value: (out) (nullable): the parsed value
+ * @endian: an endian type, e.g. %G_LITTLE_ENDIAN
+ * @error: (nullable): optional return location for an error
+ *
+ * Read a value from a buffer using a specified endian in a safe way.
+ *
+ * You don't need to use this function in "obviously correct" cases, nor should
+ * you use it when performance is a concern. Only us it when you're not sure if
+ * malicious data from a device or firmware could cause memory corruption.
+ *
+ * Returns: %TRUE if @value was set, %FALSE otherwise
+ *
+ * Since: 1.8.3
+ **/
+gboolean
+fu_memread_uint24_safe(const guint8 *buf,
+		       gsize bufsz,
+		       gsize offset,
+		       guint32 *value,
+		       FuEndianType endian,
+		       GError **error)
+{
+	guint8 dst[3] = {0x0};
+
+	g_return_val_if_fail(buf != NULL, FALSE);
+	g_return_val_if_fail(error == NULL || *error == NULL, FALSE);
+
+	if (!fu_memcpy_safe(dst,
+			    sizeof(dst),
+			    0x0, /* dst */
+			    buf,
+			    bufsz,
+			    offset, /* src */
+			    sizeof(dst),
+			    error))
+		return FALSE;
+	if (value != NULL)
+		*value = fu_memread_uint24(dst, endian);
+	return TRUE;
+}
+
 /**
  * fu_memread_uint32_safe:
  * @buf: source buffer

libfwupdplugin/fu-mem.h

@@ -42,6 +42,13 @@ fu_memread_uint16_safe(const guint8 *buf,
 		       FuEndianType endian,
 		       GError **error) G_GNUC_WARN_UNUSED_RESULT;
 gboolean
+fu_memread_uint24_safe(const guint8 *buf,
+		       gsize bufsz,
+		       gsize offset,
+		       guint32 *value,
+		       FuEndianType endian,
+		       GError **error) G_GNUC_WARN_UNUSED_RESULT;
+gboolean
 fu_memread_uint32_safe(const guint8 *buf,
 		       gsize bufsz,
 		       gsize offset,

libfwupdplugin/fwupdplugin.map

@@ -1059,3 +1059,9 @@ LIBFWUPDPLUGIN_1.8.2 {
     fu_volume_new_esp_for_path;
   local: *;
 } LIBFWUPDPLUGIN_1.8.1;
+
+LIBFWUPDPLUGIN_1.8.3 {
+  global:
+    fu_memread_uint24_safe;
+  local: *;
+} LIBFWUPDPLUGIN_1.8.2;