This tutorial shows how to authenticate two SPIFFE-identified workloads that are identified by two different SPIRE Servers.
The first part of this document demonstrates how to configure SPIFFE federation by showing the SPIRE configuration file changes and spire-server commands used to set up a stock quote webapp frontend and service backend. The second part of this document lists the steps you run to show the scenario in action using the Docker Compose files included in this tutorial's directory.
In this tutorial you will learn how to:
- Configure each SPIRE Server to expose its SPIFFE Federation bundle endpoint using SPIFFE authentication and Web PKI authentication.
- Configure the SPIRE Servers to retrieve trust bundles from each other.
- Bootstrap federation between two SPIRE Servers using different trust domains.
- Create registration entries for the workloads so that they can federate with other trust domain.
The baseline components for SPIFFE federation are:
- Two SPIRE Server instances
- Two SPIRE Agents, one connected to one SPIRE Server, and the second connected to the other SPIRE Server
- Two workloads that needs to communicate each other via mTLS, and use the Workload API to get SVIDs and trust bundles
Let's say we have a stock broker's webapp that wants to display stock quotes fetched from a stock market web service provider. The scenario goes as follows:
- The user enters the broker's webapp stock quotes URL in a browser.
- The webapp workload receives the request and makes an HTTP request for quotes to the stock market service using mTLS.
- The stock market service receives the request and sends the quotes in the response.
- The webapp renders the stock quotes page using the returned quotes and sends it to the browser.
- The browser displays the quotes to the user. The webapp includes some JavaScript to refresh the page every 1 second, so every second these steps are executed again.
In addition to the above and for the rest of this tutorial, we are going to assume the following trust domain names for these sample SPIRE installations: broker.example and stockmarket.example. Keep in mind that trust domains do not need to correspond to actual DNS domain names. Also, the applications access the WorkloadAPI directly to get SVIDs and trust bundles, meaning there are no proxies in the scenario described.
To make federation work, and because the webapp and the quotes service are going to use mTLS, both SPIRE Servers need each other's trust bundle. This is done, in part, by configuring a so-called federation endpoint on each SPIRE Server, which provides the API used by SPIRE Servers in other trust domains to get the trust bundle for the trust domain they want to federate with.
The federation endpoint exposed by a SPIRE Server can be configured to use one of two authentication methods: SPIFFE auth or Web PKI auth.
To configure the broker's SPIRE Server bundle endpoint, we use the federation section in the broker's SPIRE Server configuration file, by default server.conf:
server {
.
.
trust_domain = "broker.example"
.
.
federation {
bundle_endpoint {
address = "0.0.0.0"
port = 8443
}
}
}This will publish the federation endpoint in any IP address at port 8443 in the host where the SPIRE Server is running.
On the other side, the stock market service provider's SPIRE Server is configured in a similar fashion:
server {
.
.
trust_domain = "stockmarket.example"
.
.
federation {
bundle_endpoint {
address = "0.0.0.0"
port = 8443
}
}
}At this point, both SPIRE Servers have exposed their federation endpoints to provide their trust bundles, but none of them knows how to reach each other's federation endpoint.
We are going to assume that only the broker's SPIRE Server will use Web PKI authentication for its federation endpoint. The stock market SPIRE Server will still use SPIFFE authentication. Hence, the stock market SPIRE Server configuration remains the same as seen in the previous section.
Then, to configure the broker's SPIRE Server bundle endpoint, we configure the federation section as follows:
server {
.
.
trust_domain = "broker.example"
.
.
federation {
bundle_endpoint {
address = "0.0.0.0"
port = 443
acme {
domain_name = "broker.example"
email = "[email protected]"
tos_accepted = true
}
}
}
}This will publish the federation endpoint in any IP address at port 443. We use port 443 because we're demonstrating the use of Let's Encrypt as our ACME provider (this is used by default, if you want to use a different one then you must set the directory_url configurable). Note that tos_accepted was set to true, meaning that we accept the terms of service of our ACME provider, which in turn is needed when using Let's Encrypt.
For SPIFFE Federation using Web PKI to work, you must own the DNS domain specified for domain_name (broker.example in our example) and the domain must resolve to the SPIRE Server exposing the federation bundle endpoint.
After configuring federation endpoints, the next step to enable SPIFFE federation is to configure the SPIRE Servers to find the trust bundles for other trust domains. The federates_with configuration option in server.conf is where you specify the endpoint of the other trust domain. The configuration of this section has some slight differences when using the different methods of authentication.
As we saw previously, the SPIRE Server of the stock market service provider has its federation endpoint listening on port 8443 at any IP address. We will also assume that spire-server-stock is a DNS name that resolves to the stock market service's SPIRE Server IP address. (The Docker Compose demo here uses the hostname spire-server-stock, but in typical usage you would specify a FQDN.) Then, the broker's SPIRE Server must be configured with the following federates_with section:
server {
.
.
trust_domain = "broker.example"
.
.
federation {
bundle_endpoint {
address = "0.0.0.0"
port = 8443
}
federates_with "stockmarket.example" {
bundle_endpoint {
address = "spire-server-stock"
port = 8443
}
}
}
}Now the broker's SPIRE Server knows where to find a trust bundle that can be used to validate SVIDs containing identities from the stockmarket.example trust domain.
On the other side, the stock market service provider's SPIRE Server must be configured in a similar fashion:
server {
.
.
trust_domain = "stockmarket.example"
.
.
federation {
bundle_endpoint {
address = "0.0.0.0"
port = 8443
}
federates_with "broker.example" {
bundle_endpoint {
address = "spire-server-broker"
port = 8443
}
}
}
}That is it. Specifying the federation section and federates_with subsection of server.conf is all that's needed configure SPIFFE federation. To finish enabling SPIFFE federation, we need to bootstrap the trust bundles and register the workloads using spire-server commands as described below.
As mentioned, in this alternate scenario we are assuming that only the broker's SPIRE Server will use Web PKI authentication for its federation endpoint, so the federates_with configuration for the broker server is the same as seen in the previous section. However, the SPIRE Server of the stock market service provider needs a different configuration:
server {
.
.
trust_domain = "stockmarket.example"
.
.
federation {
bundle_endpoint {
address = "0.0.0.0"
port = 8443
}
federates_with "broker.example" {
bundle_endpoint {
address = "broker.example"
use_web_pki = true
}
}
}
}The differences are:
portwas removed. This is because by default it is set to443, which is the port where the broker's federation bundle endpoint is listening.addressnow is set to the broker's domainbroker.example.use_web_pkiwas added and set totrue. This is mandatory when the bundle endpoint to which we want to federate is using Web PKI authentication.
We have configured the SPIRE Servers with the address of the federation endpoints, but this is not enough to make federation work. To enable the SPIRE Servers to fetch the trust bundles from each other they need each other's trust bundle first, because they have to authenticate the SPIFFE identity of the federated server that is trying to access the federation endpoint. Once federation is bootstrapped, the trust bundle updates are fetched trough the federation endpoint API using the current trust bundle.
The bootstrapping is done using a couple of SPIRE Server commands: bundle show and bundle set.
Let's say we want to get the broker's SPIRE Server trust bundle. On the node where the broker's SPIRE Server is running we run:
broker> spire-server bundle show -format spiffe > broker.example.bundle
This saves the trust bundle in the broker.example.bundle file. Then the broker must give a copy of this file to the stock market service folks, so they can store this trust bundle on their SPIRE Server and associate it with the broker.example trust domain. To achieve this, the stock market service folks must run the following on the node where they have SPIRE Server running:
stock-market> spire-server bundle set -format spiffe -id spiffe://broker.example -path /some/path/broker.example.bundle
At this point the stock market service's SPIRE Server is able to validate SVIDs having SPIFFE IDs with a broker.example trust domain. However, the broker's SPIRE Server is not yet able to validate SVIDs having SPIFFE IDs with a stockmarket.example trust domain. To make this possible, the stock market folks must run the following on the node where they have SPIRE Server running:
stock-market> spire-server bundle show -format spiffe > stockmarket.example.bundle
Then the stock market folks must give a copy of this file to the broker folks, so they can store this trust bundle on their SPIRE Server and associate it with the stockmarket.example trust domain. To achieve this, the broker folks must run the following on the node where they have SPIRE Server running:
broker> spire-server bundle set -format spiffe -id spiffe://stockmarket.example -path /some/path/stockmarket.example.bundle
Now both SPIRE Servers can validate SVIDs having SPIFFE IDs with each other's trust domain, thus both can start fetching trust bundle updates from each other's federation endpoints. Also, as of now they can create registration entries for federating as shown in the next section.
Note that the creation of the broker.example.bundle file (and later importing by the stock market service) is not needed when the broker's SPIRE Server is using Web PKI authentication for its federation bundle endpoint.
Now that the SPIRE Servers have each other's trust bundle, let's see how they can create registration entries to federate with each other.
To simplify things, we are going to suppose that the stock market webapp and the quotes service are both running on Linux boxes, one owned by the stock market organization and the other owned by the broker. Since they are using SPIRE, each Linux box also has a SPIRE Agent installed. In addition to this, the webapp is run using the webapp user, and the quotes service is run using the quotes-service user.
With those assumptions, in the SPIRE Server node of the broker, the broker folks must create a registration entry. The -federatesWith flag is required to enable SPIFFE federation:
broker> spire-server entry create \
-parentID <SPIRE Agent's SPIFFE ID> \
-spiffeID spiffe://broker.example/webapp \
-selector unix:user:webapp \
-federatesWith "spiffe://stockmarket.example"
By specifying the -federatesWith flag, once this registration entry is created, when the webapp's SPIRE Server asks for an SVID it will get one from the broker's SPIRE Server with the spiffe://broker.example/webapp identity, along with the trust bundle associated to the stockmarket.example trust domain.
On the stock market service side, they must create a registration entry as follows:
stock-market> spire-server entry create \
-parentID <SPIRE Agent's SPIFFE ID> \
-spiffeID spiffe://stockmarket.example/quotes-service \
-selector unix:user:quotes-service \
-federatesWith "spiffe://broker.example"
Similarly, once this registration entry is created, when the quotes service asks for an SVID it will get one having the spiffe://stockmarket.example/quotes-service identity, along with the trust bundle associated to the broker.example trust domain.
That is about it. Now all the pieces are in place to make federation work and demonstrate how the webapp is able to communicate with the quotes service despite having identities with different trust domains.
This section explains how to use Docker Compose to try an example implementation of the SPIFFE auth scenario described in this tutorial.
Although not shown here, you could make the changes shown in the Web PKI authentication sections to try the Web PKI scenario. Remember that to configure Web PKI, the FQDN specified for domain_name must be owned by you and resolvable over the internet via DNS.
Required files for this tutorial can be found in the federation directory in https://github.com/spiffe/spire-tutorials. If you didn't already clone the repository please do so now.
Before proceeding, review the following system requirements:
- A 64-bit Linux or macOS environment
- Docker and Docker Compose installed (Docker Compose is included in macOS Docker Desktop)
- Go 1.14.4 or higher installed
Ensure that the current working directory is .../spire-tutorials/federation and run the following command to create the files needed for Docker Compose:
$ ./build.sh
Run the following command to start the SPIRE Servers and the applications:
$ docker-compose up -d
Run the following command to start the SPIRE Agents:
$ ./1-start-spire-agents.sh
Run the following command to bootstrap the federation:
$ ./2-bootstrap-federation.sh
Run the following command to create workload registration entries:
$ ./3-create-registration-entries.sh
After running this script, it may take some seconds for the applications to receive their SVIDs and trust bundles.
Open up a browser to http://localhost:8080/quotes and you should see a grid of randomly generated phony stock quotes that are updated every 1 second.
To see the broker's SPIRE Server configuration you can run:
$ docker-compose exec spire-server-broker cat conf/server/server.conf
You should see:
server {
bind_address = "0.0.0.0"
bind_port = "8081"
registration_uds_path = "/tmp/spire-registration.sock"
trust_domain = "broker.example"
data_dir = "/opt/spire/data/server"
log_level = "DEBUG"
log_file = "/opt/spire/server.log"
default_svid_ttl = "1h"
ca_subject = {
country = ["US"],
organization = ["SPIFFE"],
common_name = "",
}
federation {
bundle_endpoint {
address = "0.0.0.0"
port = 8443
}
federates_with "stockmarket.example" {
bundle_endpoint {
address = "spire-server-stock"
port = 8443
}
}
}
}
plugins {
DataStore "sql" {
plugin_data {
database_type = "sqlite3"
connection_string = "/opt/spire/data/server/datastore.sqlite3"
}
}
NodeAttestor "x509pop" {
plugin_data {
ca_bundle_path = "/opt/spire/conf/server/agent-cacert.pem"
}
}
NodeResolver "noop" {
plugin_data {}
}
KeyManager "memory" {
plugin_data = {}
}
}
To see the stock market's SPIRE Server configuration you can run:
$ docker-compose exec spire-server-stock cat conf/server/server.conf
You should see:
server {
bind_address = "0.0.0.0"
bind_port = "8081"
registration_uds_path = "/tmp/spire-registration.sock"
trust_domain = "stockmarket.example"
data_dir = "/opt/spire/data/server"
log_level = "DEBUG"
log_file = "/opt/spire/server.log"
default_svid_ttl = "1h"
ca_subject = {
country = ["US"],
organization = ["SPIFFE"],
common_name = "",
}
federation {
bundle_endpoint {
address = "0.0.0.0"
port = 8443
}
federates_with "broker.example" {
bundle_endpoint {
address = "spire-server-broker"
port = 8443
}
}
}
}
plugins {
DataStore "sql" {
plugin_data {
database_type = "sqlite3"
connection_string = "/opt/spire/data/server/datastore.sqlite3"
}
}
NodeAttestor "x509pop" {
plugin_data {
ca_bundle_path = "/opt/spire/conf/server/agent-cacert.pem"
}
}
NodeResolver "noop" {
plugin_data {}
}
KeyManager "memory" {
plugin_data = {}
}
}
To see the broker's SPIRE Server registration entries you can run:
$ docker-compose exec spire-server-broker bin/spire-server entry show
You should see something like this:
Found 1 entry
Entry ID : 2d799235-ddca-4088-ba6f-bf54d2af918f
SPIFFE ID : spiffe://broker.example/webapp
Parent ID : spiffe://broker.example/spire/agent/x509pop/4f9238aaa7a93cf96ca3d6060abe27bc51a267e7
Revision : 0
TTL : 3600
Selector : unix:user:root
FederatesWith : spiffe://stockmarket.example
To see the stock martket's SPIRE Server registration entries you can run:
$ docker-compose exec spire-server-stock bin/spire-server entry show
You should see something like this:
Found 1 entry
Entry ID : e42e8d6b-0a0a-4e38-b544-08510c35cbbe
SPIFFE ID : spiffe://stockmarket.example/quotes-service
Parent ID : spiffe://stockmarket.example/spire/agent/x509pop/50686366996ece3ca8e528765af685fe81f81435
Revision : 0
TTL : 3600
Selector : unix:user:root
FederatesWith : spiffe://broker.example
$ docker-compose down