Manage encrypted secrets in Service Fabric applications

Alt
08/22/2024

This guide walks you through the steps of managing secrets in a Service Fabric application. Secrets can be any sensitive information, such as storage connection strings, passwords, or other values that should not be handled in plain text.

Using encrypted secrets in a Service Fabric application involves three steps:

Set up an encryption certificate and encrypt secrets.
Specify encrypted secrets in an application.
Decrypt encrypted secrets from service code.

Set up an encryption certificate and encrypt secrets

Setting up an encryption certificate and using it to encrypt secrets varies between Windows and Linux.

Specify encrypted secrets in an application

The previous step describes how to encrypt a secret with a certificate and produce a base-64 encoded string for use in an application. This base-64 encoded string can be specified as an encrypted parameter in a service's Settings.xml or as an encrypted environment variable in a service's ServiceManifest.xml.

Specify an encrypted parameter in your service's Settings.xml configuration file with the IsEncrypted attribute set to true:

<?xml version="1.0" encoding="utf-8" ?>
<Settings xmlns:xsd="https://www.w3.org/2001/XMLSchema" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/2011/01/fabric">
  <Section Name="MySettings">
    <Parameter Name="MySecret" IsEncrypted="true" Value="I6jCCAeYCAxgFhBXABFxzAt ... gNBRyeWFXl2VydmjZNwJIM=" />
  </Section>
</Settings>

Specify an encrypted environment variable in your service's ServiceManifest.xml file with the Type attribute set to Encrypted:

<CodePackage Name="Code" Version="1.0.0">
  <EnvironmentVariables>
    <EnvironmentVariable Name="MyEnvVariable" Type="Encrypted" Value="I6jCCAeYCAxgFhBXABFxzAt ... gNBRyeWFXl2VydmjZNwJIM=" />
  </EnvironmentVariables>
</CodePackage>

The secrets should also be included in your Service Fabric application by specifying a certificate in the application manifest. Add a SecretsCertificate element to ApplicationManifest.xml and include the desired certificate's thumbprint.

<ApplicationManifest … >
  ...
  <Certificates>
    <SecretsCertificate Name="MyCert" X509FindType="FindByThumbprint" X509FindValue="[YourCertThumbrint]"/>
  </Certificates>
</ApplicationManifest>

Note

Upon activating an application which specifies a SecretsCertificate, Service Fabric will find the matching certificate, and grant the identity the application is running under full permissions to the certificate's private key. Service Fabric will also monitor the certificate for changes, and re-apply the permissions accordingly. To detect changes for certificates declared by common name, Service Fabric runs a periodic task which finds all matching certificates, and compares it with a cached list of thumbprints. When a new thumbprint is detected, it means that a certificate by that subject has been renewed. The task runs once per minute on each node of the cluster.

While the SecretsCertificate does allow subject-based declarations, do note that the encrypted settings are tied to the key pair which was used to encrypt the setting on the client. You must ensure that the original encryption certificate (or an equivalent) matches the subject-based declaration, and that it is installed, including its corresponding private key, on every node of the cluster which could host the application. All time-valid certificates matching the subject-based declaration and built from the same the key pair as the original encryption certificate are considered equivalents.

Inject application secrets into application instances

Ideally, deployment to different environments should be as automated as possible. This can be accomplished by performing secret encryption in a build environment and providing the encrypted secrets as parameters when creating application instances.

Use overridable parameters in Settings.xml

The Settings.xml configuration file allows overridable parameters that can be provided at application creation time. Use the MustOverride attribute instead of providing a value for a parameter:

<?xml version="1.0" encoding="utf-8" ?>
<Settings xmlns:xsd="https://www.w3.org/2001/XMLSchema" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/2011/01/fabric">
  <Section Name="MySettings">
    <Parameter Name="MySecret" IsEncrypted="true" Value="" MustOverride="true" />
  </Section>
</Settings>

To override values in Settings.xml, declare an override parameter for the service in ApplicationManifest.xml:

<ApplicationManifest ... >
  <Parameters>
    <Parameter Name="MySecret" DefaultValue="" />
  </Parameters>
  <ServiceManifestImport>
    <ServiceManifestRef ServiceManifestName="Stateful1Pkg" ServiceManifestVersion="1.0.0" />
    <ConfigOverrides>
      <ConfigOverride Name="Config">
        <Settings>
          <Section Name="MySettings">
            <Parameter Name="MySecret" Value="[MySecret]" IsEncrypted="true" />
          </Section>
        </Settings>
      </ConfigOverride>
    </ConfigOverrides>
  </ServiceManifestImport>

Now the value can be specified as an application parameter when creating an instance of the application. Creating an application instance can be scripted using PowerShell, or written in C#, for easy integration in a build process.

Using PowerShell, the parameter is supplied to the New-ServiceFabricApplication command as a hash table:

New-ServiceFabricApplication -ApplicationName fabric:/MyApp -ApplicationTypeName MyAppType -ApplicationTypeVersion 1.0.0 -ApplicationParameter @{"MySecret" = "I6jCCAeYCAxgFhBXABFxzAt ... gNBRyeWFXl2VydmjZNwJIM="}

Using C#, application parameters are specified in an ApplicationDescription as a NameValueCollection:

FabricClient fabricClient = new FabricClient();

NameValueCollection applicationParameters = new NameValueCollection();
applicationParameters["MySecret"] = "I6jCCAeYCAxgFhBXABFxzAt ... gNBRyeWFXl2VydmjZNwJIM=";

ApplicationDescription applicationDescription = new ApplicationDescription(
    applicationName: new Uri("fabric:/MyApp"),
    applicationTypeName: "MyAppType",
    applicationTypeVersion: "1.0.0",
    applicationParameters: applicationParameters)
);

await fabricClient.ApplicationManager.CreateApplicationAsync(applicationDescription);

Decrypt encrypted secrets from service code

The APIs for accessing parameters and environment variables allow for easy decryption of encrypted values. Since the encrypted string contains information about the certificate used for encryption, you do not need to manually specify the certificate. The certificate just needs to be installed on the node that the service is running on.

// Access decrypted parameters from Settings.xml
ConfigurationPackage configPackage = FabricRuntime.GetActivationContext().GetConfigurationPackageObject("Config");
bool MySecretIsEncrypted = configPackage.Settings.Sections["MySettings"].Parameters["MySecret"].IsEncrypted;
if (MySecretIsEncrypted)
{
    SecureString MySecretDecryptedValue = configPackage.Settings.Sections["MySettings"].Parameters["MySecret"].DecryptValue();
}

// Access decrypted environment variables from ServiceManifest.xml
// Note: you do not have to call any explicit API to decrypt the environment variable.
string MyEnvVariable = Environment.GetEnvironmentVariable("MyEnvVariable");

Next steps

Service Fabric Secrets Store
Learn more about application and service security

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