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  1. Commons Lang
  2. LANG-1400

StringUtils: Add method for masking strings



    • Type: Improvement
    • Status: Open
    • Priority: Minor
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: lang.*
    • Labels:
    • Flags:


      It would be great to have a function which allows to mask the original str by replacing it's
      characters with the specified character-mask. For eaxmple to mask credit card:

      mask("3566002020360505", 4, 4, '*') = "3566********0505"

      Thus the number was hidden by asterisks while first and last four digits are unmasked and seen.

      Common use case is to hide sensitive information from logs, by using it in toString() of classes or in inputs to log calls.

      I think this is "must have" functionality for Commons Lang library because from my experience in almost all bit projects what I saw was their home grown masking function.
      I think this is very important also because this is required for masking credit card numbers by PCI compliance. Also new GDPR rules requires to hide personal info as much as possible so masking of First and Last names now is required by laws.
      To make the world safer place the utility for masking should be already existing in platform to avoid situations when developer think "this is better to mask but I don't have enough time now so let's do this latter" until leak happens.
      IMHO this should be implemented even in `String` class itself.

      From my experience what I saw was usually few masking usages and styles:
      1. masking of passwords and names: only first and last symbols are shown, mask char is `*`
      2. masking of credit cards: only first and last 4 or 6 symbols are shown, mask char is `*`.
      3. credit card number shortest masking of last symbols i.e. `mask("4242424242424242") == " *4242"` but it's not so often used, I just wanted to mention.
      4. not masking but showing a length just so see that value was passed. This can be easily achieved by usual `String.legth()` method.

      There is already some pull request https://github.com/apache/commons-lang/pull/332 but I decided to create the ticket because we also need to support masking for ToStringBuilder and I would like to propose PR with my own implementation of mask() function.
      If you accept my PR then I'll send another one with a new annotation @ToStringMasked in accordance to @ToStringExclude which will mark that fields should be masked. Possible usage I see like:

      @ToStringMasked(unmaskedStart = 4, unmaskedEnd = 4) 
      String creditCardNumber;
      @ToStringMasked(unmaskedStart = 1, unmaskedEnd = 1) 
      String password;





            • Assignee:
              stokito Sergey Ponomarev
            • Votes:
              1 Vote for this issue
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