Attempt to detect credentials from the system.
Inspired from the `DefaultAzureCredential` in the Azure C++ SDK, this
credential type detects credentials from the following sources (in this
order):
* environment variables (SP credentials - same variables as in Azure C++ SDK)
* Azure CLI
* IMDS
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
Implement token request with Azure CLI.
Inspired from the Azure C++ SDK's `AzureCliCredential`, this credential
type attempts to run the Azure CLI in a shell and parse the token from
its output. This is meant for development purposes, where a user has
already installed the Azure CLI and logged in with their user account.
Pass the following environment to the process:
* PATH
* HOME
* AZURE_CONFIG_DIR
Add a token factory to construct a token from the process output. Unlike
in Azure Entra and IMDS, the CLI's JSON output does not contain
'expires_in', and the token key is in camel case.
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
Implement token request from IMDS.
No credentials are required for that - just a plain HTTP request on the
IMDS token endpoint.
Since the IMDS endpoint is a raw IP, it's not possible to reliably
determine whether IMDS is accessible or not (i.e., whether the node is
an Azure VM). Azure provides no node-local indication either. In lack of
a better choice, attempt to connect and declare failure if the
connection is not established within 3 seconds. Use a raw TCP socket for
this check, as the HTTP client currently lacks timeout or cancellation
support. Perform the check only once, during the first token refresh.
For the time being, do not support nodes with multiple user-assigned
managed identities. Expect the token request to fail in this case (IMDS
requires the identifier of the desired Managed Identity).
Add a token factory to correctly parse the HTTP response. This addresses
a discrepancy between token requests on IMDS and Azure Entra - the
'expires_in' field is a string in the former and an integer in the
latter.
Finally, implement a fail-fast retry policy for short-lived transient
errors.
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
Implement token request for Service Principals with a certificate.
The request is the same as with a secret, except that the secret is
replaced with an assertion. The assertion is a JWT that is signed with
the certificate.
To be consistent with the Azure C++ SDK, expect the certificate and the
associated private key to be encoded in PEM format and be provided in a
single file.
The docs suggest using 'PS256' for the JWT's 'alg' claim. Since this is
not supported by our current JWT library (jwt-cpp), use 'RS256' instead.
The JWT also requires a unique identifier for the 'jti' claim. Use a
random UUID for that (it should suffice for our use cases).
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
Implement token request for Service Principals with a secret.
The token request requires a TLS connection. When closing the
connection, do not wait for a response to the TLS `close_notify` alert.
Azure's OAuth server would ignore it and the Seastar `connected_socket`
would hang for 10 seconds.
Add log redaction logic to not expose sensitive data from the request
and response payloads.
Add a token factory to parse the HTTP response. This cannot be shared
with other credential types because the JSON format is not consistent.
Finally, implement a fail-fast retry policy for short-lived transient
errors.
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
The goal is to mimic the Azure C++ SDK, which offers a variety of
credentials, depending on their type and source.
Declare the following credentials:
* Service Principal credentials
* Managed Identity credentials
* Azure CLI credentials
* Default credentials
Also, define a common exception for SP and MI credentials which are
network-based.
This patch only defines the API.
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
Azure authentication is token based - the client obtains an access token
with their credentials, and uses it as a bearer token to authorize
requests to Azure services.
Define a common API for all credential types. The API will consist of a
single `get_access_token()` function that will be returning a new or a
cached access token for some resource URI (defines token scope).
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
