Unable to decrypt text files with openssl on Ubuntu 18.04

Question

I am unable to decrypt a number of text files I encrypted with openssl on Ubuntu 16.04. I always get this error message:

$ openssl des3 -d < ~/ISRIC/credentials.txt.des3.old > ~/temp/credentials.txt.old.2
enter des-ede3-cbc decryption password:
bad decrypt
139771261990464:error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt:../crypto/evp/evp_enc.c:536:

I am pretty sure the password is correct. What is the problem?

Solution 1

The password based encryption algorithm used in openssl changed from MD5 in version 1.0.2 (shipped with Ubuntu 16.04) to SHA256 in version 1.1.0 (Ubuntu 18.04). For that reason, any files encrypted on Ubuntu 16.04 fail to be decrypted on Ubuntu 18.04. The solution is to install the previous version of openssl, decrypt the files and encryt them back again with the newer version. Step by step:

Start by downloading the older version of openssl (this is the amd64 build, for other builds check packages.ubuntu.com):

wget http://security.ubuntu.com/ubuntu/pool/main/o/openssl/openssl_1.0.2g-1ubuntu13.6_amd64.deb

Now install the package directly with dpkg, this will disable the newer version:

$ sudo dpkg -i openssl_1.0.2g-1ubuntu13.6_amd64.deb

Make sure you got the right version:

$ openssl version
OpenSSL 1.0.2g  1 Mar 2016 (Library: OpenSSL 1.0.2n  7 Dec 2017)

And now decrypt the file:

$ openssl des3 -d < secret.des3 > secret.txt

Then install the latest openssl build, apt is an option:

$ sudo apt install openssl

Making sure it is the latest version:

$ openssl version
OpenSSL 1.1.0g  2 Nov 2017

And then encrypt the file again with the latest version:

$ openssl des3 < secret.txt > secret.des3

Finally remove the .deb file downloaded in the begining:

$ rm openssl_1.0.2g-1ubuntu13.6_amd64.deb

Solution 2

For files which are already encrypted, you can use the md option to force the old md5 password method.

This fixed my issue with files encrypted with 1.0.2 with aes-256-cbc which would not decrypt on 18.04 (openssl 1.1.0+).

My previous decrypt:

cat encfile | openssl enc -d -aes-256-cbc -base64 >plainfile

My new decrypt on 18.04:

cat encfile | openssl enc -md md5 -d -aes-256-cbc -base64 >plainfile

Note:
This will not work with files encrypted on 18.04 (openssl 1.1.0g+) as those will have used the newer SHA password method by default as Luis de Sousa notes.

References:
https://askubuntu.com/a/1067765/873241 (Luis de Sousa's answer)
https://bugzilla.redhat.com/show_bug.cgi?id=1520084
https://github.com/fastlane/fastlane/issues/9542

Comments

[N0rbert]

Do not forget to pin (lock) old OpenSSL version to prevent its upgrading.

[untill]

Check out unix.stackexchange.com/questions/448459/…. It might work with the latest openssl and the -md md5 option.

[Mark]

Downgrading the version was the solution for me! If you're comfortable with Docker, it may be easier to use docker run -vhost_dir:/data -it ubuntu:xenial bash and decrypt from inside the container.

[Mark]

This pointed me in the right direction (version differences). But for some reason -md wasn't enough, I needed a fully downgraded version.