Trusted root certificates for ActiveGate

There can be situations where it is necessary to add additional certificates to the certificate store shipped with ActiveGate. Follow the procedure described below to add an additional certificate to an existing ActiveGate.

Alternatively, add certificates during ActiveGate installation optional

If you prefer, additional trusted root certificates can also be specified during ActiveGate installation, by specifying installation parameters for Linux or Windows.

Determine if you need to add a CA certificate to ActiveGate

ActiveGate connects to other Dynatrace components (clusters, servers) or third-party systems (such as VMware, Cloud Foundry, Kubernetes or OpenShift) using SSL-secured channels. The root CA certificate store shipped with ActiveGate (the default certificate set shipped with Java) is sometimes insufficient to cover all the required use cases. This can happen if, for example, a certificate has been issued by the Certifying Authority inside your own organization, for a proxy, which takes SSL traffic. It is also possible that some servers in your organization, to which ActiveGate needs to connect, generate and use self-signed certificates, and your organization has not replaced them with official certificates.

If such situations occur, there will be an error in the ActiveGate log file, stating that a certificate presented by a server, to which your ActiveGate was trying to connect, was not trusted. In these cases you need to import the missing certificate to the ActiveGate, following the steps shown below.

Follow these steps to provide a customized list of trusted root certificates to ActiveGate, and configure ActiveGate to combine them with the defaults.

Determine the required CA certificates and prepare them as a file

Create a truststore from the CA certificate file

Configure ActiveGate to use the custom truststore file

Restart ActiveGate services and verify certificate configuration

Determine the required CA certificates and prepare them as a file

Before you add a certificate to the ActiveGate, you need to obtain it and place it in the ca.cert file. Obtaining the CA certificate is highly context-specific and there are no simple steps to follow. Consult appropriate sources in your organization to obtain the required certificate(s).

The following general information about CA certificates may help you to determine the required certificates:

To create a trusted SSL connection for your certificate authority, the following conditions must be met:

• Between the certificates presented by the server (API endpoint) and the certificates present in the ActiveGate truststore, a full certificate chain must be created.
• The root certificate of the chain must be included in the ActiveGate truststore, along with any other certificates NOT presented by the server/API endpoint.

To see which certificates the endpoint is presenting you can use the following command:

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openssl s_client -connect <API_ENDPOINT>:<PORT> -showcerts -servername <API_ENDPOINT_HOSTNAME>

Note:
Some applications (for example OpenShift) can present different certificates depending on the SNI. ActiveGates will set the configured endpoint hostname in the SNI.

If the above command presents a full certificate chain then you must add the root certificate to the ActiveGate truststore. You may add the intermediates as well but they are not necessary if the API endpoint presents them.

If the above command does not present a full certificate chain, then the root of the chain must be obtained elsewhere.

For example, the endpoint of the openssl request to this server—see below—only returns the server certificate, and not the root certificate. You know that this server only presents a server certificate and not a root certificate because the error says unable to get local issuer certificate. If the root certificate were present, the error message would say "Self-signed certificate in certificate chain". To create a valid SSL connection to this endpoint, you must obtain the root certificate separately.

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openssl s_client -connect localhost:6443
CONNECTED(00000005)
depth=0 CN = kube-apiserver
verify error:num=20:unable to get local issuer certificate
verify return:1
depth=0 CN = kube-apiserver
verify error:num=21:unable to verify the first certificate
verify return:1
---
Certificate chain
 0 s:CN = apiserver
   i:CN = DynatraceRootAuth
---
Server certificate
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
subject=CN = kube-apiserver

issuer=CN = kubernetes

---
Acceptable client certificate CA names
CN = kubernetes

The certificate below is an example root certificate for the above server certificate. Make sure that you only add root certificates that you trust, to your truststores.
For example:

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cat ca.crt | openssl x509 -text -noout
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 0 (0x0)
        Signature Algorithm: sha256WithRSAEncryption
        Issuer: CN = kubernetes
        Validity
            Not Before: Jan 27 19:35:08 2021 GMT
            Not After : Jan 25 19:35:08 2031 GMT
        Subject: CN = kubernetes
        Subject Public Key Info:

You can see that this is the root certificate you need because the subject and issuer are identical and they match the issuer of the server certificate shown above ('kube-apiserver ').

Create a truststore from the CA certificate file

Create an additional truststore, containing just your CA certificate(s), that will be merged by ActiveGate, at run-time, with the built-in JDK truststore. The truststore should be in the PKCS12 format. The OpenSSL formats are not supported, so use the keytool command to perform the conversion. After the conversion you must place the certificate in the ActiveGate SSL directory.

Note: If you import multiple certificates, make sure that you provide a unique alias for each certificate that you import. If you use the same alias for each certificate, all previously used certificates will be overwritten.

Examples, for Linux, of creating a PKCS12 file, from a CRT file or a PEM file, and placing it either directly in the ActiveGate SSL directory, or in the current directory, to be copied later:

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/opt/dynatrace/gateway/jre/bin/keytool -import -file ca.crt -alias dt_k8s_api -storetype pkcs12 -keystore /var/lib/dynatrace/gateway/ssl/mytrusted.p12

or

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/opt/dynatrace/gateway/jre/bin/keytool -import -file dt_k8s_api.pem -alias myCertAuthority -storetype pkcs12 -keystore mytrusted.p12

Check permissions

For Linux, check that the ActiveGate user, for which the ActiveGate was installed(dtuser by default) has write permission for the ActiveGate SSL directory (/var/lib/dynatrace/gateway/ssl by default), and that the user has read permission for the created truststore.

Configure ActiveGate to use a custom truststore file

To configure ActiveGate to use the custom truststore file mytrusted.p12, make sure that the truststore file is in the ActiveGate SSL directory, and then add the following entries to the custom.properties file in the ActiveGate configuration directory:

inicopydownload
[collector]
trustedstore = mytrusted.p12
# the following entries are optional
trustedstore-password = changeit
trustedstore-type = PKCS12

You can display the configured list of aliases and the certificate descriptions using the keytool -list command on the new truststore.
For example:

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# /opt/dynatrace/gateway/jre/bin/keytool -list -keystore /var/lib/dynatrace/gateway/ssl/mytrusted.p12
Enter keystore password:
Keystore type: PKCS12
Keystore provider: SUN
Your keystore contains 1 entry
dt_k8s_api, Apr 26, 2020,
trustedCertEntry,
Certificate fingerprint (SHA-256): 08:18:9A:F2:29:31:0D:64:F0:1F:93:A1:CC:2E:A9:21:E9:DA:40:82:9B:A8:71:B7:A4:2C:6D:8C:B3:90:31:31

Restart ActiveGate service and verify certificate configuration

Restart ActiveGate main service to make the changes take effect.
If everything has been configured correctly, the ActiveGate log should contain an entry saying:

plaintextcopydownload
Custom certificate configuration created successfully.

Troubleshooting

ActiveGate logs its actions related to the above configuration. The configured truststore will not be used (and the truststore configuration will be left unchanged) if any of the following is true:

• The javax.net.ssl.trustStore system property is specified.
  If this property is specified, it takes precedence over the ActiveGate configuration.
• The configured truststore can't be read using the configured path, password, and type.
• The merged configuration can't be written to the ssl/runtime.cacerts file.