VIMCRYPT2 vim plugin - encrypt your files with openssl

Warning!

Turns out i have been slightly reinventing the wheel.

vim has the -x command line option to work with encrypted files.

See :help encryption inside vim.

Intro

I had my adaptation for encrypting/decrypting files with vim VIMCRYPT, now it has a problem: you need to enter the encryption key every time that the file is read/decrypted and every time that the file is saved/encryted.

Now it is quite possible to make a typo, while saving the file. In this event you might have lost your precious file, as you may no longer be aware of the current encryption key.

One fix might be to make a backup before saving the file, in this event you may be lucky with the backup. That's what VIMCRYPT is doing.

The VIMCRYPT2 plugin solves this issue as follows:

After decrypting a file, we take the decryption key and keep it in memory. Now the key is not kept in plain text form, it is encrypted with a master key, the master key is a random key that is generated per editor session. The encrypted key is kept as a buffer variable.
The very same key that has been used for decryption is then used for encryption, when the file is saved back to disk.
The key is passed to openssl via a pipe, and not via a command line option. It would be visible to anyone, as a command line option, it is less exposed, as it is passed via a pipe. Now this can't be done with vimscript, that's were we need to use python3;

Other changes, relative to openssl.vim

use aes-256-ecb instead of aes-256-cbc. Reason: if the file gets damaged, then all the data after the damage point is lost, when using cipher block chaining (CBC). The damage would be limited to the AES block with the damaged byte, when using ECB
turn off vim options shelltemp and undofile when working with encrypted stuff.
exclude vulnerable ciphers from the list of supported file extensions (each supported file extension maps to a cipher type)
Now the following file extensions map to the following ciphers:
- .aes file extension uses -aes-256-ecb
- .cast file extension uses -cast
- .rc5 file extension uses -rc5
- .desx file extension uses -desx
before saving to an existing file with any of these extensions it backs up the old file.
throw out the password safe stuff, I don't need it.

Install details

Install from git

mkdir -p ~/.vim/pack/vendor/start/vimcrypt2; git clone --depth 1 https://github.com/MoserMichael/vimcrypt2 ~/.vim/pack/vendor/start/vimcrypt2

Download zip from www.vim.org mkdir -p ~/.vim/pack/vendor/start/vimcrypt2; unzip vimcrypt2.zip -d ~/.vim/pack/vendor/start/vimcrypt2

global parameters

g:vimcrypt2_cipher

By default it is: aes-256-ecb

g:vimcrypt2_addopt

Additional options passed to openssl By default: setting -md md5 - that's the old key derivation schema.

OSX Gotchas.

I got the following issues on OsX Catalina (10.15.7):

default vim does not have python3 enabled

VIM is installed by default on OSX it is located in /usr/bin/vim, however that version currently has no support for the python3, you can install a proper vim with brew

brew install vim

Now that one is put to /usr/local/bin/vim.

multiple versions of openssl

On OSX you do have openssl installed by default, however they use the LibreSSL fork

$ which openssl
/usr/bin/openssl

$ openssl version
LibreSSL 2.8.3

Now you can install openssl with brew, this gives you a real openssl

$ brew install openssl

Let's find where openssl is installed

brew list openssl

...
/usr/local/opt/openssl/bin/openssl

...



$ /usr/local/opt/openssl/bin/openssl version
OpenSSL 3.0.0 7 sep 2021 (Library: OpenSSL 3.0.0 7 sep 2021)

Now the interesting detail: the output of these two utilities can't be mixed.

The following command encrypts and decrypts a string with the same password, while using the same version of openssl

echo '123' | /usr/bin/openssl enc -e -aes-256-ecb -pass pass:blabla | /usr/bin/openssl enc -d -aes-256-ecb -pass pass:blabla
123

echo '123' | /usr/local/opt/openssl/bin/openssl enc -e -aes-256-ecb -pass pass:blabla | /usr/local/opt/openssl/bin/openssl enc -d -aes-256-ecb -pass pass:blabla
123

However the same does not work, if you try to decrypt the output of the libre ssl fork with a different utility from OpenSSL.

echo '123' | /usr/local/opt/openssl/bin/openssl enc -e -aes-256-ecb -pass pass:blabla | /usr/bin/openssl enc -d -aes-256-ecb -pass pass:blabla
<error error error>

echo '123' | /usr/bin/openssl enc -e -aes-256-ecb -pass pass:blabla | /usr/local/opt/openssl/bin/openssl enc -d -aes-256-ecb -pass pass:blabla
<error error error>

What's the reason? it appears that libressl has a different way of deriving the AES encryption key from the password. In older versions of libressl they used MD5 for deriving the AES key from the password, then they changed it to SHA256.

Adding the -md sha256 or -md md5 parameter to both versions of openssl will force them to use the same algorithm!!!


echo '123' | /usr/local/opt/openssl/bin/openssl enc -e -aes-256-ecb -pass pass:blabla -md md5 | /usr/bin/openssl enc -d -aes-256-ecb -md md5  -pass pass:blabla

echo '123' | /usr/local/opt/openssl/bin/openssl enc -e -aes-256-ecb -pass pass:blabla -md sha256 | /usr/bin/openssl enc -d -aes-256-ecb -md sha256  -pass pass:blabla

This is something that should be remembered, when moving encrypted files between different locations.

(meanwhile added the -md md5 option to the plugin, as i had to deal with a file from an old location).

Beware of openssl upgrades!!!! They can change this salt derivation business at any notice, so a newer openssl version may not decrypt a file encrypted with an older one!!! (I think that's outrageous, but that is life, apparently...)

/maybe one should better use the builtin encryption feature of vim./

However be aware that once the encrypted file has been read into memory, then it stays in memory in clear text, unencrypted! This means that any process that running on the same machine with access to your account would be able to get all of your secrets, while you view it in the editor. We learn from this that security is all in all a relative thing. Is your encrypted vim file at rest secure? I guess it is. However the whole situation a bit different, when the file is being viewed or edited.

Supported ciphers

you can get the list of supported ciphers as follows

/usr/bin/openssl enc -list

/usr/local/opt/openssl/bin/openssl enc -list

The OpenSSL version supports more ciphers than the LibreSSL version; For example OpenSSL has chacha20 , whereas LibreSSL doesn't.

Acknowledgement

This plugin is based on openssl.vim by Noah Spurrier link

MoserMichael / vimcrypt2