NiFi Slack Integration issue - 1.26.0

@Vikas-Nifi 

the following error is directly related to failure to establish certificate trust in the TLS exchange between NiFi's putSlack processor and your slack server:

javax.net.ssl.SSLHandshakeException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target "

The putSlack processor utilizes the StandardRestrictedSSLContextService to define keystore and truststore files the putSlack processor will use.  The truststore must contain the complete trustchain for the target slack server's serverAuth certificate.

You can use:

openssl s_client -connect <companyName.slack.com>:443 -showcerts

to get an output of all public certs included with the serverAuth cert.

I noticed with my slack endpoint that was not the complete trust chain (root CA certificate for ISRG Root X1 was missing from the chain).

You can download the missing rootCA public cert directly from let's encrypt and add it to the truststore set in the StandardRestrictedSSLContextService.

https://letsencrypt.org/certificates/

https://letsencrypt.org/certs/isrgrootx1.pem
https://letsencrypt.org/certs/isrg-root-x2.pem

You might also want to make sure all intermediate CAs are also added and not just the intermediate returned by the openssl command just in case server changes that you get directed to.

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Thank you,
Matt