Azure Auth Method

The azure auth method allows authentication against Vault using Azure Active Directory credentials. It treats Azure as a Trusted Third Party and expects a JSON Web Token (JWT) signed by Azure Active Directory for the configured tenant.

This method supports authentication for system-assigned and user-assigned managed identities. See Azure Managed Service Identity (MSI) for more information about these resources.

Prerequisites:

The following documentation assumes that the method has been mounted at auth/azure.

• A configured Azure AD application which is used as the resource for generating MSI access tokens.
• Client credentials (shared secret) for accessing the Azure Resource Manager with read access to compute endpoints. See Azure AD Service to Service Client Credentials

Required Azure API permissions to be granted to Vault user:

• Microsoft.Compute/virtualMachines/*/read
• Microsoft.Compute/virtualMachineScaleSets/*/read

NOTE: The above permissions are only required when the associated vm* parameters are used on login. Please see the API doc for more details.

If Vault is hosted on Azure, Vault can use MSI to access Azure instead of a shared secret. MSI must be enabled on the VMs hosting Vault.

The next sections review how the authN/Z workflows work. If you have already reviewed these sections, here are some quick links to:

• Usage
• API documentation docs.

Authentication

Via the CLI

The default path is /auth/azure. If this auth method was enabled at a different path, specify auth/my-path/login instead.

$ vault write auth/azure/login \
    role="dev-role" \
    jwt="eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..." \
    subscription_id="12345-..." \
    resource_group_name="test-group" \
    vm_name="test-vm"

The role and jwt parameters are required. When using bound_service_principal_ids and bound_group_ids in the token roles, all the information is required in the JWT (except for vm_name and vmss_name). When using other bound_* parameters, calls to Azure APIs will be made and subscription id, resource group name, and vm name/vmss_name are all required and can be obtained through instance metadata.

For example:

$ vault write auth/azure/login role="dev-role" \
     jwt="$(curl -s 'http://169.254.169.254/metadata/identity/oauth2/token?api-version=2018-02-01&resource=https%3A%2F%2Fmanagement.azure.com%2F' -H Metadata:true | jq -r '.access_token')" \
     subscription_id=$(curl -s -H Metadata:true "http://169.254.169.254/metadata/instance?api-version=2017-08-01" | jq -r '.compute | .subscriptionId')  \
     resource_group_name=$(curl -s -H Metadata:true "http://169.254.169.254/metadata/instance?api-version=2017-08-01" | jq -r '.compute | .resourceGroupName') \
     vm_name=$(curl -s -H Metadata:true "http://169.254.169.254/metadata/instance?api-version=2017-08-01" | jq -r '.compute | .name')

Via the API

The default endpoint is auth/azure/login. If this auth method was enabled at a different path, use that value instead of azure.

$ curl \
    --request POST \
    --data '{"role": "dev-role", "jwt": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..."}' \
    https://127.0.0.1:8200/v1/auth/azure/login

The response will contain the token at auth.client_token:

{
  "auth": {
    "client_token": "f33f8c72-924e-11f8-cb43-ac59d697597c",
    "accessor": "0e9e354a-520f-df04-6867-ee81cae3d42d",
    "policies": ["default", "dev", "prod"],
    "lease_duration": 2764800,
    "renewable": true
  }
}

Configuration

Auth methods must be configured in advance before machines can authenticate. These steps are usually completed by an operator or configuration management tool.

Via the CLI

1. Enable Azure authentication in Vault:

   $ vault auth enable azure
   

2. Configure the Azure auth method:

   $ vault write auth/azure/config \
       tenant_id=7cd1f227-ca67-4fc6-a1a4-9888ea7f388c \
       resource=https://management.azure.com/ \
       client_id=dd794de4-4c6c-40b3-a930-d84cd32e9699 \
       client_secret=IT3B2XfZvWnfB98s1cie8EMe7zWg483Xy8zY004=
   

   For the complete list of configuration options, please see the API documentation.

3. Create a role:

   $ vault write auth/azure/role/dev-role \
       policies="prod,dev" \
       bound_subscription_ids=6a1d5988-5917-4221-b224-904cd7e24a25 \
       bound_resource_groups=vault
   

   Roles are associated with an authentication type/entity and a set of Vault policies. Roles are configured with constraints specific to the authentication type, as well as overall constraints and configuration for the generated auth tokens.

   For the complete list of role options, please see the API documentation.

Via the API

1. Enable Azure authentication in Vault:

   $ curl \
       --header "X-Vault-Token: ..." \
       --request POST \
       --data '{"type": "azure"}' \
       https://127.0.0.1:8200/v1/sys/auth/azure
   

2. Configure the Azure auth method:

   $ curl \
       --header "X-Vault-Token: ..." \
       --request POST \
       --data '{"tenant_id": "...", "resource": "..."}' \
       https://127.0.0.1:8200/v1/auth/azure/config
   

3. Create a role:

   $ curl \
       --header "X-Vault-Token: ..." \
       --request POST \
       --data '{"policies": ["dev", "prod"], ...}' \
       https://127.0.0.1:8200/v1/auth/azure/role/dev-role
   

Plugin Setup

Assuming you have saved the binary vault-plugin-auth-azure to some folder and configured the plugin directory for your server at path/to/plugins:

1. Enable the plugin in the catalog:

   $ vault write sys/plugins/catalog/auth/azure-auth \
       command="vault-plugin-auth-azure" \
       sha256="..."
   

2. Enable the azure auth method as a plugin:

   $ vault auth enable -path=azure azure-auth
   

Azure Debug Logs

The Azure auth plugin supports debug logging which includes additional information about requests and responses from the Azure API.

To enable the Azure debug logs, set the following environment variable on the Vault server:

AZURE_GO_SDK_LOG_LEVEL=DEBUG

API

The Azure Auth Plugin has a full HTTP API. Please see the API documentation for more details.

Code Example

The following code snippet demonstrates the Azure auth method to authenticate with Vault.

package main

import (
    "context"
    "fmt"

    vault "github.com/hashicorp/vault/api"
    auth "github.com/hashicorp/vault/api/auth/azure"
)

// Fetches a key-value secret (kv-v2) after authenticating to Vault via Azure authentication.
// This example assumes you have a configured Azure AD Application.
func getSecretWithAzureAuth() (string, error) {
    config := vault.DefaultConfig() // modify for more granular configuration

    client, err := vault.NewClient(config)
    if err != nil {
        return "", fmt.Errorf("unable to initialize Vault client: %w", err)
    }

    azureAuth, err := auth.NewAzureAuth(
        "dev-role-azure",
    )
    if err != nil {
        return "", fmt.Errorf("unable to initialize Azure auth method: %w", err)
    }

    authInfo, err := client.Auth().Login(context.TODO(), azureAuth)
    if err != nil {
        return "", fmt.Errorf("unable to login to Azure auth method: %w", err)
    }
    if authInfo == nil {
        return "", fmt.Errorf("no auth info was returned after login")
    }

    // get secret
    secret, err := client.Logical().Read("kv-v2/data/creds")
    if err != nil {
        return "", fmt.Errorf("unable to read secret: %w", err)
    }

    data, ok := secret.Data["data"].(map[string]interface{})
    if !ok {
        return "", fmt.Errorf("data type assertion failed: %T %#v", secret.Data["data"], secret.Data["data"])
    }

    // data map can contain more than one key-value pair,
    // in this case we're just grabbing one of them
    key := "password"
    value, ok := data[key].(string)
    if !ok {
        return "", fmt.Errorf("value type assertion failed: %T %#v", data[key], data[key])
    }

    return value, nil
}

using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Text;
using Newtonsoft.Json;
using VaultSharp;
using VaultSharp.V1.AuthMethods;
using VaultSharp.V1.AuthMethods.Azure;
using VaultSharp.V1.Commons;

namespace Examples
{
    public class AzureAuthExample
    {
        public class InstanceMetadata
        {
            public string name { get; set; }
            public string resourceGroupName { get; set; }
            public string subscriptionId { get; set; }
        }

        const string MetadataEndPoint = "http://169.254.169.254/metadata/instance?api-version=2017-08-01";
        const string AccessTokenEndPoint = "http://169.254.169.254/metadata/identity/oauth2/token?api-version=2018-02-01&resource=https://management.azure.com/";

        /// <summary>
        /// Fetches a key-value secret (kv-v2) after authenticating to Vault via Azure authentication.
        /// This example assumes you have a configured Azure AD Application.
        /// </summary>
        public string GetSecretWithAzureAuth()
        {
            string vaultAddr = Environment.GetEnvironmentVariable("VAULT_ADDR");
            if(String.IsNullOrEmpty(vaultAddr))
            {
                throw new System.ArgumentNullException("Vault Address");
            }

            string roleName = Environment.GetEnvironmentVariable("VAULT_ROLE");
            if(String.IsNullOrEmpty(roleName))
            {
                throw new System.ArgumentNullException("Vault Role Name");
            }

            string jwt = GetJWT();
            InstanceMetadata metadata = GetMetadata();

            IAuthMethodInfo authMethod = new AzureAuthMethodInfo(roleName: roleName, jwt: jwt, subscriptionId: metadata.subscriptionId, resourceGroupName: metadata.resourceGroupName, virtualMachineName: metadata.name);
            var vaultClientSettings = new VaultClientSettings(vaultAddr, authMethod);

            IVaultClient vaultClient = new VaultClient(vaultClientSettings);

            // We can retrieve the secret from the VaultClient object
            Secret<SecretData> kv2Secret = null;
            kv2Secret = vaultClient.V1.Secrets.KeyValue.V2.ReadSecretAsync(path: "/creds").Result;

            var password = kv2Secret.Data.Data["password"];

            return password.ToString();
        }

        /// <summary>
        /// Query Azure Resource Manage for metadata about the Azure instance
        /// </summary>
        private InstanceMetadata GetMetadata()
        {
            HttpWebRequest metadataRequest = (HttpWebRequest)WebRequest.Create(MetadataEndPoint);
            metadataRequest.Headers["Metadata"] = "true";
            metadataRequest.Method = "GET";

            HttpWebResponse metadataResponse = (HttpWebResponse)metadataRequest.GetResponse();

            StreamReader streamResponse = new StreamReader(metadataResponse.GetResponseStream());
            string stringResponse = streamResponse.ReadToEnd();
            var resultsDict = JsonConvert.DeserializeObject<Dictionary<string, InstanceMetadata>>(stringResponse);

            return resultsDict["compute"];
        }

        /// <summary>
        /// Query Azure Resource Manager (ARM) for an access token
        /// </summary>
        private string GetJWT()
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(AccessTokenEndPoint);
            request.Headers["Metadata"] = "true";
            request.Method = "GET";

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();

            // Pipe response Stream to a StreamReader and extract access token
            StreamReader streamResponse = new StreamReader(response.GetResponseStream());
            string stringResponse = streamResponse.ReadToEnd();
            var resultsDict = JsonConvert.DeserializeObject<Dictionary<string, string>>(stringResponse);

            return resultsDict["access_token"];
        }
    }
}