Configure RSA key size 1024 but default getting restores to 2048

Solution Unverified - Updated -

Environment

  • Red Hat Enterprise Linux
    • 8.x

Issue

  • How to configure crypto policy RSA key size to 1024 ?

Resolution

  • Standard default policy requires 2048 key size.
                 LEGACY         DEFAULT          FIPS
RSA          min.1024-bit     min.2048-bit    min.2048-bit

In the Default mode the RSA keys are accepted if they are at least 2048 bits long.

  • If application requires 1024 key size then must need to break the policy and create the custom pmod file as example below.

[root@localhost ~]# cat /etc/crypto-policies/policies/modules/RSA1024.pmod
min_rsa_size = 1024

Then apply it:

[root@localhost ~]# update-crypto-policies --show
DEFAULT
[root@localhost ~]# cat /etc/crypto-policies/back-ends/java.config 
jdk.tls.ephemeralDHKeySize=2048
jdk.certpath.disabledAlgorithms=MD2, MD5, SHA1, DSA, RSA keySize < 2048
jdk.tls.disabledAlgorithms=DH keySize < 2048, TLSv1.1, TLSv1, SSLv3, SSLv2, DHE_DSS, RSA_EXPORT, DHE_DSS_EXPORT, DHE_RSA_EXPORT, DH_DSS_EXPORT, DH_RSA_EXPORT, DH_anon, ECDH_anon, DH_RSA, DH_DSS, ECDH, 3DES_EDE_CBC, DES_CBC, RC4_40, RC4_128, DES40_CBC, RC2, HmacMD5
jdk.tls.legacyAlgorithms=

[root@localhost ~]# update-crypto-policies --set DEFAULT:RSA1024
Setting system policy to DEFAULT:RSA1024

Note: System-wide crypto policies are applied on application start-up.
It is recommended to restart the system for the change of policies
to fully take place.

[root@localhost ~]# shutdown -r now
(log in again after a while)
[root@localhost ~]# update-crypto-policies --show
DEFAULT:RSA1024

Note: It is recommended to update your application to accept 2048 size because 1024 keys size is no longer considered secure due to vulnerabilities.

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