[jira] [Resolved] (CXF-6996) "n" in JWK for RSA should be unsigned, but is signed in JwkUtils.prepareRSAJwk

["Sergey Beryozkin (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CXF-6996?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sergey Beryozkin resolved CXF-6996.
-----------------------------------
       Resolution: Fixed
         Assignee: Sergey Beryozkin
    Fix Version/s: 3.1.8
                   3.2.0

> "n" in JWK for RSA should be unsigned, but is signed in JwkUtils.prepareRSAJwk
> ------------------------------------------------------------------------------
>
>                 Key: CXF-6996
>                 URL: https://issues.apache.org/jira/browse/CXF-6996
>             Project: CXF
>          Issue Type: Bug
>          Components: JAX-RS Security
>    Affects Versions: 3.1.7
>            Reporter: Svein Otto Solem
>            Assignee: Sergey Beryozkin
>            Priority: Minor
>             Fix For: 3.2.0, 3.1.8
>
>
> The length of the "n" value is 257 bytes for a 2048 bits key length. 
> If "n" is handled as an unsigned int, it should be at most 256 bytes. 
> The added null byte is caused by BigInteger.toByteArray() which always handles the integer as a signed integer.
> A fix is just to remove all the first 0-bytes in the encodedModulus, see JwkUtils.prepareRSAJwk.
>  This fix will surely break clients which just decodes the "n" as an unsigned value using new BigInteger(byte[]) . These clients must be changed to either always insert a leading "0-byte" before using the new BigInteger(byte[]) contstructor, or they should use the BigInteger(signum, magnitude) constructor.  
> The extra "sign byte" is mentioned in:
> https://tools.ietf.org/html/rfc7518#page-30 



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