html-vault – create self-contained HTML for password protected content

html-vault

Create self-contained HTML pages protecting secret information. Usage:

html-vault ~/Document/secret.txt protected.html

Here's an example HTML file (password is "thisisanexample")

When called, the program requires you to enter a password. It will then generate the HTML output file. This may take a moment. Once completed, the generated protected.html file is is a self-contained HTML file with the content of secret.txt embedded in a way that it can only be accessed if the password is known. You might then place this file on a hidden url for later access.

This works by using browser based crypto. A derived password is generated using 20 million rounds of PBKDF2. The secret file content is AES-CBC encrypted using this derived password.

What it can and can't do

• The generated HTML can of course not detect if it was copied. So you cannot known if your file is in the hands of an attacker. Placing the file on a secret https URL might make this a bit more unlikely but of course cannot prevent it.

• If the browser or OS used to view the HTML file cannot be trusted, the encryption is useless as the plain password could be logged by a keylogger for later decryption and the password might still be in memory somewhere. This also includes rogue browser extensions with full DOM access.

• If the password it too weak, bruteforcing the content might still be viable. PBKDF2 somewhat helps and the large number of rounds was chosen to make bruteforcing more difficult.

• A server-side attacker might modify the HTML and inject code that exfiltrates the entered password. This might be mitigated by inspecting the HTML source code prior to entering the password. The generated HTML is reasonably small to make this easy.

• It does not authenticate the decrypted content. This would be rather useless anyway as that implies that someone was able to modify the HTML file in which case you might have bigger problems.

• There have been no reviews yet, but the source code should be (and stay!) easy to understand.

Status

Unreviewed - use with caution. Feedback is welcome.

Requirements

• Tested with a recent Chrome/Firefox version. Requires SubtleCrypto API.

• Python2 or Python3 with pyCrypto

License

BSD 2-clause