During a two-way SSL handshake, an exception is thrown

Issue

During a two-way SSL handshake, the following exception occurs.

javax.net.ssl|WARNING|DC|tomcat-http--46| EDT|SSLSocketImpl.java:1428|handling exception (
"throwable" : {
     java.lang.NullPointerException
     at org.bouncycastle.crypto.signers.PSSSigner.generateSignature(Unknown Source)
     at org.bouncycastle.jce.provider.JDKPSSSigner.engineSign(Unknown Source)
     at java.security.Signature$Delegate.engineSign(Signature.java:1382)
     at java.security.Signature.sign(Signature.java:698)
     at sun.security.ssl.CertificateVerify$T12CertificateVerifyMessage.<init>(CertificateVerify.java:608)
     at sun.security.ssl.CertificateVerify$T12CertificateVerifyProducer.produce(CertificateVerify.java:760)

Environment

Liferay DXP 7.0
Liferay DXP 7.1
Liferay DXP 7.2

Resolution

Since multiple bundles rely on Bouncy Castle Provider 1.45, which has known vulnerabilities, hence, the listed exceptions are known exceptions in Liferay DXP 7.2, DXP 7.1, and DXP 7.0.
- Bouncy Castle Provider 1.45 has the following known vulnerabilities:
  https://nvd.nist.gov/vuln/detail/CVE-2013-1624
  https://nvd.nist.gov/vuln/detail/CVE-2017-13098
  https://nvd.nist.gov/vuln/detail/CVE-2018-5382
  https://nvd.nist.gov/vuln/detail/CVE-2018-1000613
  Please upgrade Bouncy Castle Provider to version 1.60 or above
However, the following Liferay versions are fixed for the same:
DXP 7.0: liferay-fixpack-de-90-7010
DXP 7.1: liferay-fixpack-dxp-17-7110
DXP 7.2: liferay-fixpack-dxp-4-7210

Additional Information

LPS-104661
If the hotfix is required for this issue, please create a support ticket requesting the hotfix by attaching the patch details.
Installing Fix Packs and Hotfixes on Liferay DXP will guide you to install the Fixpack/Hotfix in your environment.
The two-way SSL handshake usually happens between two servers. This is the type of SSL handshake that is used in server to server kind of communication. All the servers are required to validate the identity of the other server.