Following a tricky upgrade to a Jenkins server it was found that the server was no longer able to communicate with the Git server, although SSH access with private keys was stil working correctly. On invrestigating the Jenkins logs (found at Logs at: http://YOUR-JENKINS-SERVER-URL/log/all) this error was found to be the problem:
Failed to login with creds MYCREDENTIALNAMEHERE sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target at sun.security.provider.certpath.SunCertPathBuilder.build(Unknown Source) at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(Unknown Source) at java.security.cert.CertPathBuilder.build(Unknown Source) Caused: sun.security.validator.ValidatorException: PKIX path building failed at sun.security.validator.PKIXValidator.doBuild(Unknown Source) at sun.security.validator.PKIXValidator.engineValidate(Unknown Source) at sun.security.validator.Validator.validate(Unknown Source) at sun.security.ssl.X509TrustManagerImpl.validate(Unknown Source) at sun.security.ssl.X509TrustManagerImpl.checkTrusted(Unknown Source) at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(Unknown Source) Caused: javax.net.ssl.SSLHandshakeException
The problem here is that the Java runtime is not able to validate the connection as it doesnt have the relevant SSL certificate. To resolve I needed to download the certificate from the site and add it to the Java Keystore.
On the server download the relevant web certificate for connecting to the relevant site (a GitHub server in my instance) that you are trying to access. Next find which Java JRE your Jenkins was using. This can be found in your Jenkins.xml file under the executable element. For example %BASE%\jre\bin\java means c:\Jenkins\JRE\bin\java if you have installed Jenkins to C:\Jenkins on Windows. Now find the cacerts file inside that Java runtime that it was using (for example C:\Jenkins\jre\lib\security\cacerts) where you will need to install the Certificate. To add the cert to the Java Keystore for that Java install run the below in a terminal:
keytool -import -alias INSERT_ALIAS_NAME_HERE -keystore PATH_TO_JRE_HERE\security\cacerts -file CERTIFICATE_FILE_NAME
keytool -import -alias ExampleName -keystore C:\Jenkins\jre\lib\security\cacerts -file exampleCertFile.cer
If you are asked for a password then it will be ‘changeit‘ by default.
Now the JRE Java runtime on the box that Jenkins is now using has the Certificate installed it will be able to make a SSL connection.