I have a message, I know the password and the cipher that was used to encrypt it, but I can't figure out how to ask openssl to decrypt it.
I see the cipher in the output from the ciphers command, and the man page lists a enc command for Encoding with Ciphers, but I can't find how I would do the opposite, decode a message.
I think you're looking for something like this:
openssl yourcipher -d < yourfile
For example if the file was encrypted using des3 cipher, and the file is /path/to/file.des3 then:
openssl des3 -d < /path/to/file.des3
It will ask you for the passphrase.
If the file is base64 encoded, then you should be able decode and decrypt like this:
openssl enc -base64 -d < /path/to/file | openssl yourcipher -d
base64 -d [input] > [output] and then openssl [cipher] -d < [output] as well as deciphering the file as is, and I get the same "bad magic number" in both cases.
file command tell you? Is the file binary?
data about the decoded file. I assume that your answer is correct and that something is wrong on my end. Possibly I've corrupted the input or similar. I'll try to work that out and get back.
openssl cipherslists ciphersuites for SSL/TLS, which is in practice never password based, and doesn't leave messages anywhere you could later decrypt (i.e. if you have a file, it's not SSL/TLS).openssl encis one commonly used password-based encryption scheme, but there are CMS and (rarely) S/MIME PBEs and a common PGP PBE, and also PBE schemes for keys which are not accurately described as messages, as well as other PBEs.