Configure a Java HTTP Client to Accept Self-Signed Certificates

Internal

• HttpClient
• Maven

Overview

If a Java client is attempting to connect to a HTTPS server configured with a self-signed SSL certificate, the Java client will fail with:

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

This article provides a solution to this problem. The solution consist in obtaining the HTTPS server's public key, importing it into a local truststore and configuring the Java client to use the local truststore.

Procedure

Obtain the HTTPS Server's Certificate

Use openssl s_client to obtain the server's certificate as described here. The response will include the server's certificate in PEM format, which should look similarly to:

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

Save it locally in a server-cert.pem file.

Import the Certificate into a Local Truststore

Import the certificate into a local truststore, and declare it trusted while importing it:

keytool -import -alias <server-name> -keystore ./<server-name>.truststore -file server-cert.pem

keytool -import -alias nexus  -keystore ./nexus.truststore -file server-cert.pem

Enter keystore password:
Re-enter new password:
Owner: CN=*.apps.openshift.novaordis.io
Issuer: CN=openshift-signer@1510385842
Serial number: 12
Valid from: Sat Nov 11 00:04:28 PST 2017 until: Mon Nov 11 00:04:29 PST 2019
Certificate fingerprints:
     MD5:  E0:B7:FA:9C:4F:01:66:1C:51:FC:F9:49:56:69:F8:88
     SHA1: FE:27:F4:0F:20:EA:A8:E4:1D:D4:F3:FD:81:4A:C8:06:35:1E:E5:1A
     SHA256: 3B:A8:06:B2:6F:49:27:1B:7A:50:67:42:E0:6B:E4:99:32:CC:22:21:F2:D4:26:B8:9D:21:BB:96:9D:CF:DD:FB
     Signature algorithm name: SHA256withRSA
     Version: 3

Extensions:

#1: ObjectId: 2.5.29.19 Criticality=true
BasicConstraints:[
 CA:false
 PathLen: undefined
]

#2: ObjectId: 2.5.29.37 Criticality=false
ExtendedKeyUsages [
 serverAuth
]

#3: ObjectId: 2.5.29.15 Criticality=true
KeyUsage [
 DigitalSignature
 Key_Encipherment
]

#4: ObjectId: 2.5.29.17 Criticality=false
SubjectAlternativeName [
 DNSName: *.apps.openshift.novaordis.io
 DNSName: apps.openshift.novaordis.io
]

Trust this certificate? [no]:  yes
Certificate was added to keystore

Configure the Java Client to use the Local Truststore

java -Djavax.net.ssl.trustStore=.../nexus.truststore -Djavax.net.ssl.trustStorePassword=<password> ...