[jira] [Created] (SSHD-1107) Diffie Hellmann group exchange minimum key size should be configurable for security reasons

["Achim Hügen (Jira)" <ji...@apache.org>]

Achim Hügen created SSHD-1107:
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             Summary: Diffie Hellmann group exchange minimum key size should be configurable for security reasons
                 Key: SSHD-1107
                 URL: https://issues.apache.org/jira/browse/SSHD-1107
             Project: MINA SSHD
          Issue Type: Bug
    Affects Versions: 2.5.1
            Reporter: Achim Hügen


Currently the minimum key size for DH group exchange is 1024 bit (for example when using diffie-hellman-group-exchange-sha256 for KEX)

This is below the current recommendations of 2048 bit (see [NIST|https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57Pt3r1.pdf], Table 2-1 and [https://tools.ietf.org/id/draft-ietf-curdle-ssh-kex-sha2-09.html#rfc.section.3.4).]

For compatibility reasons it is still essential to support diffie-hellman-group-exchange-sha256, but the minimum key size should be configurable, so that a server operator can harden its server.

The minimum size is hardcoded in org.apache.sshd.common.util.security.SecurityUtils#MIN_DHGEX_KEY_SIZE

This could be made configurable via a system property like one already exists for the maximum (see MAX_DHGEX_KEY_SIZE_PROP)

 



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