Add file_size() with error detection

Makefile.am

@@ -22,6 +22,7 @@ libaacs_la_SOURCES=\
 	src/libaacs/mmc.c \
 	src/file/dirs.h \
 	src/file/file.h \
+	src/file/file.c \
 	src/file/filesystem.h \
 	src/file/filesystem.c \
 	src/file/keydbcfg.c \

src/file/file.c

+/*
+ * This file is part of libbluray
+ * Copyright (C) 2014  VideoLAN
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "file.h"
+
+#include <stdio.h>  // SEEK_*
+
+
+int64_t file_size(AACS_FILE_H *fp)
+{
+    int64_t pos    = file_tell(fp);
+    int64_t res1   = file_seek(fp, 0, SEEK_END);
+    int64_t length = file_tell(fp);
+    int64_t res2   = file_seek(fp, pos, SEEK_SET);
+
+    if (res1 < 0 || res2 < 0 || pos < 0 || length < 0) {
+        return -1;
+    }
+
+    return length;
+}

src/file/file.h

@@ -42,7 +42,7 @@
 #define file_seek(X,Y,Z) X->seek(X,Y,Z)
 #define file_tell(X) X->tell(X)
 #define file_read(X,Y,Z) X->read(X,Y,Z)
-
+BD_PRIVATE int64_t file_size(AACS_FILE_H *fp);
 
 BD_PRIVATE extern AACS_FILE_H *(*file_open)(const char* filename, const char *mode);
 

src/libaacs/aacs.c

@@ -413,9 +413,12 @@ static size_t _read_file(AACS *aacs, const char *file, void **data)
         return 0;
     }
 
-    file_seek(fp, 0, SEEK_END);
-    f_size = file_tell(fp);
-    file_seek(fp, 0, SEEK_SET);
+    f_size = file_size(fp);
+    if (f_size <= 0) {
+        BD_DEBUG(DBG_AACS | DBG_CRIT, "Invalid size %"PRId64" for %s\n", file);
+        file_close(fp);
+        return 0;
+    }
 
     *data = malloc(f_size);
     if (*data) {