This is a short introduction to authenticating with Azure Active Directory (AAD) with AzureAuth.
The main function in AzureAuth is
get_azure_token, which obtains an OAuth token from AAD:
The function has the following arguments:
resource: The resource or scope for which you want a token. For AAD v1.0, this should be a single URL (eg “https://example.com”) or a GUID. For AAD v2.0, this should be a vector of scopes (see below).
tenant: The AAD tenant.
app: The app ID or service principal ID to authenticate with.
certificate: Your authentication credentials.
auth_type: The OAuth authentication method to use. See the next section.
version: The version of AAD for which you want a token, either 1 or 2. The default is version 1. Note that the OAuth scheme is always 2.0.
Scopes in AAD v2.0 consist of a URL or a GUID, along with a path that designates the scope. If a scope doesn’t have a path,
get_azure_token will append the
/.default path with a warning. A special scope is
offline_access, which requests a refresh token from AAD along with the access token: without this, you will have to reauthenticate if you want to refresh the token.
# request an AAD v1.0 token for Resource Manager token1 <- get_azure_token("https://management.azure.com/", "mytenant", "app_id") # same request to AAD v2.0, along with a refresh token token2 <- get_azure_token(c("https://management.azure.com/.default", "offline_access"), "mytenant", "app_id", version=2) # requesting multiple scopes in AAD v2.0 (Microsoft Graph) scopes <- c("https://graph.microsoft.com/User.Read", "https://graph.microsoft.com/Files.Read", "https://graph.microsoft.com/Mail.Read", "offline_access") token3 <- get_azure_token(scopes, "mytenant", "app_id", version=2)
AzureAuth supports the following methods for authenticating with AAD: authorization_code, device_code, client_credentials, resource_owner and on_behalf_of.
get_azure_tokenopens 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_tokenretrieves this authorization code and sends it to the AAD access endpoint, which returns the OAuth token. The httpuv package must be installed to use this method, as it requires a web server to listen on the (local) redirect URI. Since it opens a browser to load the AAD authorization page, your machine must also have an Internet browser installed that can be run from inside R. In particular, if you are using a Linux Data Science Virtual Machine in Azure, you may run into difficulties; use one of the other methods instead.
get_azure_tokencontacts 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_tokenpolls the AAD access endpoint for a token, which is provided once you have entered the code.
get_azure_tokencontacts the access endpoint, passing it the credentials. This can be either a client secret or a certificate, which you supply in the
certificateargument respectively. Once the credentials are verified, the endpoint returns the token. This is the method typically used by service accounts.
# 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")
get_azure_tokenpasses your (personal) username and password to the AAD access endpoint, which validates your credentials and returns the token.
# 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 client_credentials method get_azure_token("myresource", "mytenant", "app_id", password="client_secret") # this will use on_behalf_of method get_azure_token("myresource", "mytenant", "app_id", password="client_secret", on_behalf_of=token)
get_managed_token to obtain tokens from within a managed identity. This is a VM, service or container in Azure that can authenticate as itself, which removes the need to save secret passwords or certificates.
Using the interactive flows (authorization_code and device_code) from within a Shiny app requires separating the authorization (logging in to Azure) step from the token acquisition step. For this purpose, AzureAuth provides the
get_device_creds functions. You can use these from within your app to carry out the authorization, and then pass the resulting credentials to
get_azure_token itself. See the “Authenticating from Shiny” vignette for an example app.
AzureAuth caches tokens based on all the inputs to
get_azure_token, as listed above. It defines its own directory for cached tokens, using the rappdirs package. On recent Windows versions, this will usually be in the location
C:\Users\(username)\AppData\Local\AzureR. On Linux, it will be in
~/.local/share/AzureR, and on MacOS, it will be in
~/Library/Application Support/AzureR. Note that a single directory is used for all tokens, and the working directory is not touched (which significantly lessens the risk of accidentally introducing cached tokens into source control).
For reasons of CRAN policy, the first time that AzureAuth is loaded, it will prompt 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. The prompt only appears in an interactive session; if AzureAuth is loaded in a batch script, the directory is not created if it doesn’t already exist.
To list all cached tokens on disk, use
list_azure_tokens. This returns a list of token objects, named according to their MD5 hashes.
To load a token from the cache using its MD5 hash, use
load_azure_token. To delete a cached token, use
delete_azure_token. This takes the same inputs as
get_azure_token, or you can supply an MD5 hash via the
hash argument. To delete all cached tokens, use
If you want to bypass the cache, specify
use_cache=FALSE in the call to
get_azure_token. This will always obtain a new token from AAD, and also prevent it being saved to the cache.
A token object can be refreshed by calling its
refresh() method. If the token’s credentials contain a refresh token, this is used; otherwise a new access token is obtained by reauthenticating. In most situations you don’t need to worry about this, as the AzureR packages will check if the credentials have expired and automatically refresh them for you.
One scenario where you might want to refresh manually is using a token for one resource to obtain a token for another resource. Note that in AAD, a refresh token can be used to obtain an access token for any resource or scope that you have permissions for. Thus, for example, you could use a refresh token issued on a request for
https://management.azure.com to obtain a new access token for
https://graph.microsoft.com (assuming you’ve been granted permission).
To obtain an access token for a new resource, change the object’s
resource (for an AAD v1.0 token) or
scope field (for an AAD v2.0 token) before calling
refresh(). If you also want to retain the token for the old resource, you should call the
clone() method first to create a copy.
# use a refresh token from one resource to get an access token for another resource tok <- get_azure_token("https://myresource", "mytenant", "app_id") tok2 <- tok$clone() tok2$resource <- "https://anotherresource" tok2$refresh() # same for AAD v2.0 tok <- get_azure_token(c("https://myresource/.default", "offline_access"), "mytenant", "app_id", version=2) tok2 <- tok$clone() tok2$scope <- c("https://anotherresource/.default", "offline_access") tok2$refresh()
For the details on Azure Active Directory, consult the Microsoft documentation.