What is the difference between base64 and MIME base 64? [closed]

Question

I just spent way too much time banging my head against an SMTP server because it didn't like the base64 encoded credentials I was using. Turns out that when I chose NOT to use perl like so many instructions on the internet say to use, I was making a big mistake. Why is this? I thought base64 was a single standard.

Consider:

$ perl -MMIME::Base64 -e 'print encode_base64("ASDF1234asdf")'
QVNERjEyMzRhc2Rm

$ base64 <<<"ASDF1234asdf"
QVNERjEyMzRhc2RmCg==

$ python3.6 -m base64 <<<"ASDF1234asdf"
QVNERjEyMzRhc2RmCg==

$ python2.7 -m base64 <<<"ASDF1234asdf"
QVNERjEyMzRhc2RmCg==

$ perl -MMIME::Base64 -e "print encode_base64('my_user_name@my_domain.com')"
bXlfdXNlcl9uYW1lQG15X2RvbWFpbi5jb20=

$ base64 <<<"my_user_name@my_domain.com"
bXlfdXNlcl9uYW1lQG15X2RvbWFpbi5jb20K

So, perl is unique in its output and my server requires it that way.

Why am I getting different results?

How do you get the MIME/SMTP friendly output with something other than perl?

Answer 1

This is not a Perl vs. everyone else thing; this is a "using Bash's <<< construct" vs. "not doing that" thing. Though not explicitly documented (at least not in the manpage on Ubuntu Xenial), Bash appends a newline to herestrings (the <<< thing) when passing them to commands. As a result, all of the commands you're invoking with <<< are actually encoding 'ASDF1234asdf\n', while Perl (which isn't invoked with a herestring) is encoding just 'ASDF1234asdf'. Different input, different output.

In order to pass a string without a trailing newline to a command's standard input, use the printf command, e.g.:

$ printf %s ASDF1234asdf | base64
QVNERjEyMzRhc2Rm

Answer 2

There are no different base64 encodings, but encoding a newline character at the end, or not:

$ perl -MMIME::Base64 -e 'print encode_base64("ASDF1234asdf")'
QVNERjEyMzRhc2Rm
$ perl -MMIME::Base64 -e 'print encode_base64("ASDF1234asdf\n")'
QVNERjEyMzRhc2RmCg==
$ echo -ne "my_user_name@my_domain.com" | base64
bXlfdXNlcl9uYW1lQG15X2RvbWFpbi5jb20=
$ echo -ne "my_user_name@my_domain.com\n" | base64
bXlfdXNlcl9uYW1lQG15X2RvbWFpbi5jb20K