How to override Spring boot keystore/truststore for mutual SSL

Question

I have a Spring Boot application. Its application.yml is fetched from an online resource. It contains the following config for mutual SSL:

server:
  ssl:
    enabled: true
    client-auth: need
    key-store-type: PKCS12
    key-store: http://{config server url}/keystore.p12
    key-store-password: {keystore password}
    trust-store-type: JKS
    trust-store: http://{config server url}/truststore.jks
    trust-store-password: {truststore password}
  port: 8443

When running the application, I have this error:

java.io.IOException: DerInputStream.getLength(): lengthTag=111, too big.
    at sun.security.util.DerInputStream.getLength(DerInputStream.java:599)
    at sun.security.util.DerValue.init(DerValue.java:391)
    at sun.security.util.DerValue.<init>(DerValue.java:332)
    at sun.security.util.DerValue.<init>(DerValue.java:345)
    at sun.security.pkcs12.PKCS12KeyStore.engineLoad(PKCS12KeyStore.java:1938)
    at java.security.KeyStore.load(KeyStore.java:1445)
    at org.apache.tomcat.util.security.KeyStoreUtil.load(KeyStoreUtil.java:69)
    at org.apache.tomcat.util.net.SSLUtilBase.getStore(SSLUtilBase.java:209)
    at org.apache.tomcat.util.net.SSLHostConfigCertificate.getCertificateKeystore(SSLHostConfigCertificate.java:206)
    at org.apache.tomcat.util.net.SSLUtilBase.getKeyManagers(SSLUtilBase.java:272)
    at org.apache.tomcat.util.net.SSLUtilBase.createSSLContext(SSLUtilBase.java:239)
    at org.apache.tomcat.util.net.AbstractJsseEndpoint.createSSLContext(AbstractJsseEndpoint.java:97)
    ... 23 common frames omitted

But I can open the keystore and truststore just fine by doing it programatically. (Shown below)

private KeyStore getKeyStore() {
    KeyStore keyStore = KeyStore.getInstance("PKCS12");
    try (InputStream is = readCertificateFromURL(new URI(keyStoreURL))) {
        keyStore.load(is, keyStorePassword.toCharArray());
    }
    return keyStore();
}

private InputStream readCertificateFromURL(URI uri) throws IOException {
    RequestEntity<Void> requestEntity = RequestEntity.get(uri)
         .accept(org.springframework.http.MediaType.APPLICATION_OCTET_STREAM)
         .build();
    Resource resource = new RestTemplate().exchange(requestEntity,Resource.class).getBody();
    return resource.getInputStream();
}

How can I tell Spring boot to pick these key/truststores instead of the ones defined in application.yml?

The only things I found online were about overriding the keystore/truststore paths, and not the KeyStore objects themselves.

Answer 1

It indeed works on local files as @Toby asked. The thing is that the stores were downloaded from a config server and were not downloaded as binary. I ended up implementing a custom SslStoreProvider:

@Bean
public WebServerFactoryCustomizer<TomcatServletWebServerFactory> tomcatSslCustomizer() {
    return tomcat -> tomcat.setSslStoreProvider(new SslStoreProvider() {

        @Override
        public KeyStore getKeyStore() throws Exception {
            KeyStore keyStore = KeyStore.getInstance(keyStoreType);
            try (InputStream is = readStoreFromURL(new URI(keyStoreURL))) {
                keyStore.load(is, keyStorePassword.toCharArray());
            }
            return keyStore;
        }

        @Override
        public KeyStore getTrustStore() throws Exception {
            KeyStore truststore = KeyStore.getInstance(trustStoreType);
            try (InputStream is = readStoreFromURL(new URI(trustStoreURL))) {
                truststore.load(is, trustStorePassword.toCharArray());
            }
            return truststore;
        }

        private InputStream readStoreFromURL(URI uri) {
            // Download the stores as binary from the config server
        }

    });
}