The terraform login
command supports performing an OAuth 2.0 authorization
request using configuration provided by the target host. You may wish to
implement this protocol if you are producing a third-party implementation of
any Terraform-native services,
such as a Terraform module registry.
First, Terraform uses
remote service discovery to
find the OAuth configuration for the host. The host must support the service
name login.v1
and define for it an object containing OAuth client
configuration values, like this:
{
"login.v1": {
"client": "terraform-cli",
"grant_types": ["authz_code"],
"authz": "/oauth/authorization",
"token": "/oauth/token",
"ports": [10000, 10010],
}
}
The properties within the discovery object are as follows:
client
(Required): The client_id
value to use when making requests, as
defined in RFC 6749 section 2.2.
Because Terraform is a public client (it is installed on end-user systems
and thus cannot protect an OAuth client secret), the client_id
is purely
advisory and the server must not use it as a guarantee that an authorization
request is truly coming from Terraform.
grant_types
(Optional): A JSON array of strings describing a set of OAuth
2.0 grant types the server is able to support. A "grant type" selects a
specific mechanism by which an OAuth server authenticates the request and
issues an authorization token.
Terraform CLI supports a single grant type:
authz_code
: authorization code grant.
Both the authz
and token
properties are required when authz_code
is
present.If not specified, grant_types
defaults to ["authz_code"]
.
authz
(Required if needed for a given grant type): the server's
authorization endpoint.
If given as a relative URL, it is resolved from the location of the
service discovery document.
token
(Required if needed for a given grant type): the server's
token endpoint.
If given as a relative URL, it is resolved from the location of the
service discovery document.
ports
(Optional): A two-element JSON array giving an inclusive range of
TCP ports that Terraform may use for the temporary HTTP server it will start
to provide the redirection endpoint
for the first step of an authorization code grant. Terraform opens a TCP
listen port on the loopback interface in order to receive the response from
the server's authorization endpoint.
If not specified, Terraform is free to select any TCP port greater than or equal to 1024.
Terraform allows constraining this port range for interoperability with OAuth
server implementations that require each client_id
to be associated with
a fixed set of valid redirection endpoint URLs. Configure such a server
to expect a range of URLs of the form http://localhost:10000/
with different consecutive port numbers, and then specify that port range
using ports
.
We recommend allowing at least 10 distinct port numbers if possible, and assigning them to numbers greater than or equal to 10000, to minimize the risk that all of the possible ports will already be in use on a particular system.
When requesting an authorization code grant, Terraform CLI implements the Proof Key for Code Exchange extension in order to protect against other applications on the system intercepting the incoming request to the redirection endpoint. We strongly recommend that you select an OAuth server implementation that also implements this extension and verifies the code challenge sent to the token endpoint.
Terraform CLI does not support OAuth refresh tokens or token expiration. If your
server issues time-limited tokens, Terraform CLI will simply begin receiving
authorization errors once the token expires, after which the user can run
terraform login
again to obtain a new token.