Is it possible in openssl to store the signature in a signed file?

Question

OpenSSL

There is a file.txt , when it is signed with a private key (for example, rsa or any other), is it possible to save the signature in the same file.txt ?

Answer 1

I'm afraid this is problematic, because after adding the signature, the file will change, and the signature will become invalid. And even if we bite out the signature before checking it (and not the fact that we will immediately understand where the signature is!), then little things like an extra line feed can still prevent us from restoring the original look of the file.