Issue #10740 has been reported by Scott Blum.

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Bug #10740: Base64 urlsafe methods are not urlsafe
https://bugs.ruby-lang.org/issues/10740

* Author: Scott Blum
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.1.3p242 (2014-09-19 revision 47630) [x86_64-darwin14.0]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
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Base64.urlsafe_decode64 is not to spec, because it currently REQUIRES appropriate trailing '=' characters.
Base64.urlsafe_encode64 produces trailing '=' characters.

'=' is not web safe, and is not recommended for base64url.  Some specs even disallow.

Suggested fix:

~~~
  # Returns the Base64-encoded version of +bin+.
  # This method complies with ``Base 64 Encoding with URL and Filename Safe
  # Alphabet'' in RFC 4648.
  # The alphabet uses '-' instead of '+' and '_' instead of '/'
  # and has no trailing pad characters.
  def urlsafe_encode64(bin)
    strict_encode64(bin).tr("+/", "-_").tr('=', '')
  end

  # Returns the Base64-decoded version of +str+.
  # This method complies with ``Base 64 Encoding with URL and Filename Safe
  # Alphabet'' in RFC 4648.
  # The alphabet uses '-' instead of '+' and '_' instead of '/'.
  # Trailing pad characters are optional.
  def urlsafe_decode64(str)
    str = str.tr("-_", "+/")
    str = str.ljust((str.length + 3) & ~3, '=')
    strict_decode64(str)
  end
~~~




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