Azure DNS :: Let’s Encrypt client and ACME library written in Go.
Author: Lego Team
Description: Configuration for Azure DNS.
Date: 2019-03-03T16:39:46+01:00

# Azure DNS

Configuration for Azure DNS.

- Code: `azuredns`
- Since: v4.13.0

Here is an example bash command using the Azure DNS provider:

    ### Using client secret

    AZURE_CLIENT_ID=<your service principal client ID> \
    AZURE_TENANT_ID=<your service principal tenant ID> \
    AZURE_CLIENT_SECRET=<your service principal client secret> \
    lego --email you@example.com --dns azuredns -d '*.example.com' -d example.com run

    ### Using client certificate

    AZURE_CLIENT_ID=<your service principal client ID> \
    AZURE_TENANT_ID=<your service principal tenant ID> \
    AZURE_CLIENT_CERTIFICATE_PATH=<your service principal certificate path> \
    lego --email you@example.com --dns azuredns -d '*.example.com' -d example.com run

    ### Using Azure CLI

    az login \
    lego --email you@example.com --dns azuredns -d '*.example.com' -d example.com run

    ### Using Managed Identity (Azure VM)

    AZURE_TENANT_ID=<your service principal tenant ID> \
    AZURE_RESOURCE_GROUP=<your target zone resource group name> \
    lego --email you@example.com --dns azuredns -d '*.example.com' -d example.com run

    ### Using Managed Identity (Azure Arc)

    AZURE_TENANT_ID=<your service principal tenant ID> \
    IMDS_ENDPOINT=http://localhost:40342 \
    IDENTITY_ENDPOINT=http://localhost:40342/metadata/identity/oauth2/token \
    lego --email you@example.com --dns azuredns -d '*.example.com' -d example.com run

## Credentials

Environment Variable Name | Description
--- | ---
`AZURE_CLIENT_CERTIFICATE_PATH` | Client certificate path
`AZURE_CLIENT_ID` | Client ID
`AZURE_CLIENT_SECRET` | Client secret
`AZURE_TENANT_ID` | Tenant ID

The environment variable names can be suffixed by `_FILE` to reference a file instead of a value. More information here.

## Additional Configuration

Environment Variable Name | Description
--- | ---
`AZURE_AUTH_METHOD` | Specify which authentication method to use
`AZURE_AUTH_MSI_TIMEOUT` | Managed Identity timeout duration
`AZURE_ENVIRONMENT` | Azure environment, one of: public, usgovernment, and china
`AZURE_POLLING_INTERVAL` | Time between DNS propagation check in seconds (Default: 2)
`AZURE_PRIVATE_ZONE` | Set to true to use Azure Private DNS Zones and not public
`AZURE_PROPAGATION_TIMEOUT` | Maximum waiting time for DNS propagation in seconds (Default: 120)
`AZURE_RESOURCE_GROUP` | DNS zone resource group
`AZURE_SERVICEDISCOVERY_FILTER` | Advanced ServiceDiscovery filter using Kusto query condition
`AZURE_SUBSCRIPTION_ID` | DNS zone subscription ID
`AZURE_TTL` | The TTL of the TXT record used for the DNS challenge in seconds (Default: 60)
`AZURE_ZONE_NAME` | Zone name to use inside Azure DNS service to add the TXT record in

The environment variable names can be suffixed by `_FILE` to reference a file instead of a value. More information here.

## Description

Several authentication methods can be used to authenticate against Azure DNS API.

### Default Azure Credentials (default option)

Default Azure Credentials automatically detects in the following locations and prioritized in the following order:

1. Environment variables for client secret: `AZURE_CLIENT_ID`, `AZURE_TENANT_ID`, `AZURE_CLIENT_SECRET`
2. Environment variables for client certificate: `AZURE_CLIENT_ID`, `AZURE_TENANT_ID`, `AZURE_CLIENT_CERTIFICATE_PATH`
3. Workload identity for resources hosted in Azure environment (see below)
4. Shared credentials (defaults to `~/.azure` folder), used by Azure CLI

Link:

- Azure Authentication

### Environment variables

#### Service Discovery

Lego automatically finds all visible Azure (private) DNS zones using Azure ResourceGraph query. This can be limited by specifying environment variable `AZURE_SUBSCRIPTION_ID` and/or `AZURE_RESOURCE_GROUP` which limits the DNS zones to only a subscription or to one resourceGroup.

Additionally environment variable `AZURE_SERVICEDISCOVERY_FILTER` can be used to filter DNS zones with an addition Kusto filter eg:

    resources
    | where type =~ "microsoft.network/dnszones"
    | ${AZURE_SERVICEDISCOVERY_FILTER}
    | project subscriptionId, resourceGroup, name

#### Client secret

The Azure Credentials can be configured using the following environment variables:

- AZURE_CLIENT_ID = “Client ID”
- AZURE_CLIENT_SECRET = “Client secret”
- AZURE_TENANT_ID = “Tenant ID”

This authentication method can be specifically used by setting the `AZURE_AUTH_METHOD` environment variable to `env`.

#### Client certificate

The Azure Credentials can be configured using the following environment variables:

- AZURE_CLIENT_ID = “Client ID”
- AZURE_CLIENT_CERTIFICATE_PATH = “Client certificate path”
- AZURE_TENANT_ID = “Tenant ID”

This authentication method can be specifically used by setting the `AZURE_AUTH_METHOD` environment variable to `env`.

### Workload identity

Workload identity allows workloads running Azure Kubernetes Services (AKS) clusters to authenticate as an Azure AD application identity using federated credentials.

This must be configured in kubernetes workload deployment in one hand and on the Azure AD application registration in the other hand.

Here is a summary of the steps to follow to use it :

- create a `ServiceAccount` resource, add following annotations to reference the targeted Azure AD application registration : `azure.workload.identity/client-id` and `azure.workload.identity/tenant-id`.
- on the `Deployment` resource you must reference the previous `ServiceAccount` and add the following label : `azure.workload.identity/use: "true"`.
- create a federated credentials of type `Kubernetes accessing Azure resources`, add the cluster issuer URL and add the namespace and name of your kubernetes service account.

Link :

- Azure AD Workload identity

This authentication method can be specifically used by setting the `AZURE_AUTH_METHOD` environment variable to `wli`.

### Azure Managed Identity

#### Azure Managed Identity (with Azure workload)

The Azure Managed Identity service allows linking Azure AD identities to Azure resources, without needing to manually manage client IDs and secrets.

Workloads with a Managed Identity can manage their own certificates, with permissions on specific domain names set using IAM assignments. For this to work, the Managed Identity requires the Reader role on the target DNS Zone, and the DNS Zone Contributor on the relevant `_acme-challenge` TXT records.

For example, to allow a Managed Identity to create a certificate for “fw01.lab.example.com”, using Azure CLI:

    export AZURE_SUBSCRIPTION_ID="00000000-0000-0000-0000-000000000000"
    export AZURE_RESOURCE_GROUP="rg1"
    export SERVICE_PRINCIPAL_ID="00000000-0000-0000-0000-000000000000"

    export AZURE_DNS_ZONE="lab.example.com"
    export AZ_HOSTNAME="fw01"
    export AZ_RECORD_SET="_acme-challenge.${AZ_HOSTNAME}"

    az role assignment create \
    --assignee "${SERVICE_PRINCIPAL_ID}" \
    --role "Reader" \
    --scope "/subscriptions/${AZURE_SUBSCRIPTION_ID}/resourceGroups/${AZURE_RESOURCE_GROUP}/providers/Microsoft.Network/dnszones/${AZURE_DNS_ZONE}"

    az role assignment create \
    --assignee "${SERVICE_PRINCIPAL_ID}" \
    --role "DNS Zone Contributor" \
    --scope "/subscriptions/${AZURE_SUBSCRIPTION_ID}/resourceGroups/${AZURE_RESOURCE_GROUP}/providers/Microsoft.Network/dnszones/${AZURE_DNS_ZONE}/TXT/${AZ_RECORD_SET}"

A timeout wrapper is configured for this authentication method. The duration can be configured by setting the `AZURE_AUTH_MSI_TIMEOUT`. The default timeout is 2 seconds. This authentication method can be specifically used by setting the `AZURE_AUTH_METHOD` environment variable to `msi`.

#### Azure Managed Identity (with Azure Arc)

The Azure Arc agent provides the ability to use a Managed Identity on resources hosted outside of Azure (such as on-prem virtual machines, or VMs in another cloud provider).

While the upstream `azidentity` SDK will try to automatically identify and use the Azure Arc metadata service, if you get `azuredns: DefaultAzureCredential: failed to acquire a token.` error messages, you may need to set the environment variables:

- `IMDS_ENDPOINT=http://localhost:40342`
- `IDENTITY_ENDPOINT=http://localhost:40342/metadata/identity/oauth2/token`

A timeout wrapper is configured for this authentication method. The duration can be configured by setting the `AZURE_AUTH_MSI_TIMEOUT`. The default timeout is 2 seconds. This authentication method can be specifically used by setting the `AZURE_AUTH_METHOD` environment variable to `msi`.

### Azure CLI

The Azure CLI is a command-line tool provided by Microsoft to interact with Azure resources. It provides an easy way to authenticate by simply running `az login` command. The generated token will be cached by default in the `~/.azure` folder.

This authentication method can be specifically used by setting the `AZURE_AUTH_METHOD` environment variable to `cli`.

### Open ID Connect

Open ID Connect is a mechanism that establish a trust relationship between a running environment and the Azure AD identity provider. It can be enabled by setting the `AZURE_AUTH_METHOD` environment variable to `oidc`.

## More information

- API documentation
- Go client