AzureAuth

AzureAuth provides Azure Active Directory (AAD) authentication functionality for R users of Microsoft's Azure cloud. Use this package to obtain OAuth 2.0 tokens for Azure services including Azure Resource Manager, Azure Storage and others. Both AAD v1.0 and v2.0 are supported.

You can install the development version of the package from GitHub, with devtools::install_github("cloudyr/AzureAuth").

Obtaining tokens

The main function in AzureAuth is get_azure_token, which obtains an OAuth token from AAD. The token is cached in a user-specific directory using the rappdirs package, and future requests will use the cached token without needing you to reauthenticate.

For reasons of CRAN policy, AzureAuth will ask you for permission to create this directory. Unless you have a specific reason otherwise, it's recommended that you allow the directory to be created. Note that most other cloud engineering tools save credentials in this way, including Docker, Kubernetes, and the Azure CLI itself.

library(AzureAuth)

token <- get_azure_token(resource="myresource", tenant="mytenant", app="app_id", ...)

Other supplied functions include list_azure_tokens, delete_azure_token and clean_token_directory, to let you manage the token cache.

AzureAuth supports the following methods for authenticating with AAD: authorization_code, device_code, client_credentials, resource_owner and on_behalf_of.

1. Using the authorization_code method is a multi-step process. First, get_azure_token opens a login window in your browser, where you can enter your AAD credentials. In the background, it loads the httpuv package to listen on a local port. Once you have logged in, the AAD server redirects your browser to a local URL that contains an authorization code. get_azure_token retrieves this authorization code and sends it to the AAD access endpoint, which returns the OAuth token.

# obtain a token using authorization_code
# no user credentials needed
get_azure_token("myresource", "mytenant", "app_id", auth_type="authorization_code")

2. The device_code method is similar in concept to authorization_code, but is meant for situations where you are unable to browse the Internet -- for example if you don't have a browser installed or your computer has input constraints. First, get_azure_token contacts the AAD devicecode endpoint, which responds with a login URL and an access code. You then visit the URL and enter the code, possibly using a different computer. Meanwhile, get_azure_token polls the AAD access endpoint for a token, which is provided once you have entered the code.

# obtain a token using device_code
# no user credentials needed
get_azure_token("myresource", "mytenant", "app_id", auth_type="device_code")

3. The client_credentials method is much simpler than the above methods, requiring only one step. get_azure_token contacts the access endpoint, passing it the credentials. This can be either a client secret or a certificate, which you supply in the password or certificate argument respectively. Once the credentials are verified, the endpoint returns the token.

# obtain a token using client_credentials
# supply credentials in password arg
get_azure_token("myresource", "mytenant", "app_id",
                password="client_secret", auth_type="client_credentials")

# can also supply a client certificate as a PEM/PFX file...
get_azure_token("myresource", "mytenant", "app_id",
                certificate="mycert.pem", auth_type="client_credentials")

# ... or as an object in Azure Key Vault
cert <- AzureKeyVault::key_vault("myvault")$certificates$get("mycert")
get_azure_token("myresource", "mytenant", "app_id",
                certificate=cert, auth_type="client_credentials")

4. The resource_owner method also requires only one step. In this method, get_azure_token passes your (personal) username and password to the AAD access endpoint, which validates your credentials and returns the token.

# obtain a token using resource_owner
# supply credentials in username and password args
get_azure_token("myresource", "mytenant", "app_id",
                username="myusername", password="mypassword", auth_type="resource_owner")

5. The on_behalf_of method is used to authenticate with an Azure resource by passing a token obtained beforehand. It is mostly used by intermediate apps to authenticate for users. In particular, you can use this method to obtain tokens for multiple resources, while only requiring the user to authenticate once.

# obtaining multiple tokens: authenticate (interactively) once...
tok0 <- get_azure_token("serviceapp_id", "mytenant", "clientapp_id", auth_type="authorization_code")
# ...then get tokens for each resource with on_behalf_of
tok1 <- get_azure_token("resource1", "mytenant," "serviceapp_id",
                        password="serviceapp_secret", auth_type="on_behalf_of", on_behalf_of=tok0)
tok2 <- get_azure_token("resource2", "mytenant," "serviceapp_id",
                        password="serviceapp_secret", auth_type="on_behalf_of", on_behalf_of=tok0)

If you don't specify the method, get_azure_token makes a best guess based on the presence or absence of the other authentication arguments, and whether httpuv is installed.

# this will default to authorization_code if httpuv is installed, and device_code if not
get_azure_token("myresource", "mytenant", "app_id")

# this will use on_behalf_of method
get_azure_token("myresource", "mytenant", "app_id",
                password="client_secret", on_behalf_of=token)

Acknowledgements

The AzureAuth interface is based on the OAuth framework in the httr package, customised and streamlined for Azure. It is an independent implementation of OAuth, but benefited greatly from the work done by Hadley Wickham and the rest of the httr development team.