Initial commit

.gitignore

+*~
+\#*#

LICENSE

+The MIT License (MIT)
+
+Copyright (c) 2017 Andreas Olsson
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

+# urandom-restore
+
+If a file has been backed up to **/dev/null** there is a chance that
+you might be able to restore it from **/dev/urandom**. That is what
+_urandom-restore_ is for.
+
+
+## Usage
+
+_urandom-restore_ is called with the name of the file you want to
+restore as its one argument.
+
+    $ ./urandom-restore taxes2016.ods
+    /tmp/tmpiy7xg93r/taxes2016.ods
+
+To test backing up and restoring a file there is the included shell
+script _test-backup-and-restore_.
+
+    $ ./test-backup-and-restore ~/Documents/taxes2017.ods
+    The original /home/andreas/Documents/taxes2017.ods does not match the restored /tmp/tmppxr16hsu/taxes2017.ods
+
+
+## Limitations
+
+The free version of _urandom-restore_ only supports restoring files
+which are 50 MiB or smaller.

test-backup-and-restore

+#!/bin/bash
+set -eu
+
+orgfile="$1"
+cat "$orgfile" > /dev/null
+
+shortname=$(basename "$orgfile")
+restored=$(./urandom-restore "$shortname")
+
+if diff -q "$orgfile" "$restored" > /dev/null; then
+    echo "The original $orgfile matches the restored $restored"; exit 0
+else
+    echo "The original $orgfile does not match the restored $restored"; exit 1
+fi

urandom-restore

+#!/usr/bin/python3
+
+import os
+import sys
+from random import SystemRandom
+from tempfile import mkdtemp
+
+MAX_RESTORE_SIZE = 1024 * 1024 * 50
+
+
+def usage():
+    print('Usage: {} file-to-restore'.format(sys.argv[0]))
+    sys.exit(1)
+
+
+def urestore(path):
+    size = SystemRandom().randint(1, MAX_RESTORE_SIZE)
+    data = os.urandom(size)
+    with open(path, 'wb') as ftr:
+        ftr.write(data)
+    print(path)
+
+
+def main():
+    if len(sys.argv) != 2:
+        usage()
+    filepath = sys.argv[1]
+    shortname = os.path.basename(filepath)
+    outdir = mkdtemp()
+    newpath = os.path.join(outdir, shortname)
+    urestore(newpath)
+
+
+if __name__ == "__main__":
+    main()