Strange \n in base64 encoded string in Ruby

Question

The inbuilt Base64 library in Ruby is adding some '\n's. I'm unable to find out the reason. For this special example:

irb(main):001:0> require 'rubygems'
=> true
irb(main):002:0> require 'base64'
=> true
irb(main):003:0> str =  "1110--ad6ca0b06e1fbeb7e6518a0418a73a6e04a67054"
=> "1110--ad6ca0b06e1fbeb7e6518a0418a73a6e04a67054"
irb(main):004:0> Base64.encode64(str)
=> "MTExMC0tYWQ2Y2EwYjA2ZTFmYmViN2U2NTE4YTA0MThhNzNhNmUwNGE2NzA1\nNA==\n"

The \n's are at the last and 6th position from end. The decoder (Base64.decode64) returns back the old string perfectly. Strange thing is, these \n's don't add any value to the encoded string. When I remove the newlines from the output string, the decoder decodes it again perfectly.

irb(main):005:0> Base64.decode64(Base64.encode64(str).gsub("\n", '')) == str
=> true

More of this, I used an another JS library to produce the base64 encoded output of the same input string, the output comes without the \n's.

Is this a bug or anything else? Has anybody faced this issue before?

FYI,

$ ruby -v
ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]

Answer 1

The docs are somewhat confusing, the b64encode method is supposed to add a newline for every 60th character, and the example for the encode64 method is actually using the b64encode method.

It seems the pack("m") method for the Array class used by encode64 also adds the newlines. I would consider it a design bug that this is not optional.

You could either remove the newlines yourself, or if you're using rails, there's ActiveSupport::CoreExtensions::Base64::Encoding with the encode64s method.

Answer 2

Yeah, this is quite normal. The doc gives an example demonstrating the line-splitting. base64 does the same thing in other languages too (eg. Python).

The reason content-free newlines are added at the encode stage is because base64 was originally devised as an encoding mechanism for sending binary content in e-mail, where the line length is limited. Feel free to replace them away if you don't need them.