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Mar 17, 2018 - This utility will allow you to fetch and decrypt VNC passwords on a local computer system with VNC Server configured with a password.

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Comments

commented Feb 22, 2018

How To Decrypt Md5 Password

Not documented anywhere in the FAQ; TigerVNC passwords (and likely its authentication methods) are entirely insecure.

  • Passwords are limited to 8 characters in length, even if you specify 20.

    • Extra characters are silently ignored and TigerVNC pretends they're useful.
    • Try it!: Enter only the first 8 characters of your password to log in.
  • Passwords are stored on the server in DES encrypted (effectively plain text).

    • In Windows: HKEY_LOCAL_MACHINESOFTWARETigerVNCWinVNC4Password
  • This weakness has been known for at least 11 years and is readily exploited with common tools.

    • (details) https://www.raymond.cc/blog/crack-or-decrypt-vnc-server-encrypted-password/
    • (download) https://www.raymond.cc/blog/wp-content/plugins/download-monitor/download.php?id=232
    • (download) http://aluigi.org/pwdrec/vncpwd.zip
    • (virustotal) https://www.virustotal.com/#/file/9d773bd8045688eb8fbb0baa0dfe161aef1a1feb1a4a696289b13e99707270c9/detection

Passwords should be stored, at minimum, as a one-way hash that cannot be decrypted. They do not need to be decryptable for any practical purpose. Anyone can brute force an 8 character password, even without gaining momentary access to the local system.

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Member

commented Feb 22, 2018

Vnc Viewer

Server

That would be nice, but the protocol unfortunately requires the password to be known to the server so we cannot hash it. So any improvements here would require a protocol extension, and getting that widely deployed among other VNC implementations.

As for warning about the length, we already have #370 for that. So I'm afraid I'll close this as a duplicate, unless you have something more tangible to suggest for changing the authentication.

Author

commented Feb 22, 2018
edited

If the security of TigerVNC cannot be improved because it must be backwards compatible with intrinsically insecure VNC protocols of 20 years ago, then that should be documented on the head of every article on the website in bold red lettering. I was unable to find any overt or easy to find mentions about the weaknesses mentioned above: DES, 8 character max, stored insecurely where malware regularly scrape passwords.

Does TigerVNC even thwart high-speed brute force password tries and failure attempts?

Similarly, TigerVNC as a project needs to decide whether it wants to stick to being an obsolete backwards compatible program, or a modern and secure program, in a formal statement and liability waiver. There is clearly not enough urgency to discourage people from using TigerVNC. The site requires a statement that implores people to stop using this software, toot sweet.

Contributor

commented Feb 22, 2018

OK, seriously.. This is an open source project, and as the saying goes'free as in speech, not beer'. If this subject is of such vital importanceto you then why not jump in and help instead of making snarky comments?
On Thu, Feb 22, 2018 at 2:27 PM, a-raccoon ***@***.***> wrote: If the security of TigerZNC cannot be improved because it must be backwards compatable with intrinsically insecure ZNC protocols of 20 years ago, then that should be documented on the head of every article on the website in bold red lettering. I was unable to find any overt or easy to find mentions about the weaknesses mentioned above: DES, 8 character max, stored insecurely where malware regularly scrape passwords. Does TigerZNC even thwart high-speed brute force password tries and failure attempts? Similarly, TigerZNC as a project needs to decide whether it wants to stick to being an obsolete backwards compatible program, or a modern and secure program, in a formal statement and liability waiver. There is clearly not enough urgency to discourage people from using TigerZNC. The site requires a statement that implores people to stop using this software, toot sweet. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#601 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AHnWbcjyA_ZUN0celDwuQ-Mmj2NEROmIks5tXb-vgaJpZM4SO9h9> .
Author

commented Feb 22, 2018
edited

Crack

My remarks are anything but snarky. You also mistaken users who submit feedback, bug reports and security advisories as 'programmers who need to fix it for themselves or shut up.' This is not the case.

referenced this issue Feb 23, 2018

Closed

Interface feedback for maximum password length #602

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