For a long time, people have been logging into the apps they use via passwords or password managers. And many open standards and identity providers on the market continue to evolve how users authenticate and authorize with websites and applications. The issue is that the same problem exists for software services—when applications talk to applications, how do we prove the credibility of service-to-service connections?

Enter SPIFFE and SPIRE. SPIFFE is a specification for implementing identity for workloads, and SPIRE is the code that implements this specification in practice. Together, the projects create a standardized, secure way to identify software services and authenticate them. SPIFFE and SPIRE recently reached graduation status with the Cloud Native Computing Foundation (CNCF), solidifying the projects’ maturity as a top open-source standard mechanism to deliver cryptographic runtime identity for both cloud-native and legacy workloads.

SPIFFE and SPIRE are already used across many major public deployments. Yet not all developers are familiar with their intricacies. Below, I’ll take a gander at both projects and how they operate to provide a bit more context. I also spoke with Evan Gilman, SPIFFE/SPIRE maintainer, to gather more insights on the history of the projects and their future goalposts.

What is SPIFFE?

The Secure Production Identity Framework For Everyone (SPIFFE) is a specification for workload identity. According to Gilman, the easiest way to think about SPIFFE is as a passport. Similar to how people are issued passports in a common shape with a barcode and standard information, SPIFFE dictates the standard methods to prove and validate the identity of a service. It’s like bringing the “Sign in with Google” experience to the software services themselves, he adds.

There are three key components in SPIFFE. First, SPIFFE specifies that services shall identify themselves with what’s called a SPIFFE ID, which is defined as a URI in the format of spiffe://trust-domain-name/path. These IDs are then encoded into a SPIFFE Verifiable Identity Document or SVID. SVIDs aren’t so much a document type themselves — instead, they support either X.509 or JWT document types. Last but not least, SPIFFE specifies a workload API that issues and rotates these SVIDs, along with the keys needed to validate them.

What is SPIRE?

SPIRE is the code that implements the SPIFFE specification—you can think of it as a production-ready SPIFFE runtime environment. SPIRE, the “flagship SPIFFE implementation,” is a true end-to-end instantiation of SPIFFE that securely issues SVIDs, renews SVIDS and performs attestation, among other functions. If SPIFFE defines what a passport is, then SPIRE is the agency that issues the passports, said Gilman.

The SPIRE agent runs on a node and exposes the workload API, which hooks into each workload. A workload, as defined by the SPIFFE documentation can be a web server, an instance of a MySQL database, a worker program or a web application composed of independently deployed systems. By communicating in this manner, SPIFFE/SPIRE can solve the issue of “secret zero,” which refers to the conundrum of proving the first credential to newfound systems.

More Background on SPIFFE/SPIRE

Joe Beda, a co-founder of Kubernetes, first proposed SPIFFE at GlueCon in 2016. At the time, Google was considering what internal technology it had that might prove helpful to the broader industry. It’s said that the technology that inspired SPIFFE/SPIRE can trace its roots to security and identity subsystems brought to Google from AT&T and Bell Labs.

Nowadays, SPIFFE/SPIRE is actively maintained by many organizations, and we continue to see impressive production use cases. “SPIRE is deployed in some staggeringly large cases,” explained Gilman. SPIFFE/SPIRE adoption can be seen within GitHub, Netflix, Pinterest, Square, Transferwise, Uber and many other large technology companies. In terms of ownership, Gilman said that SPIRE is most used by platform engineers, infrastructure engineers or security engineers, depending on the organization’s roles.

Future Outlook for SPIFFE and SPIRE

SPIFFE/SPIRE appear to have the resources and backing to maintain a stable implementation, so the future looks bright for both projects. In terms of new features, in mid-2022, a first-class integration with SPIRE was merged into the Istio service mesh as a more flexible alternative to Istio’s built-in SPIFFE implementation. Another recent update is experimental support for SPIRE on Windows. Regarding future plans, SPIFFE/SPIRE maintainers will likely continue to iteratively improve the specification and implementation with frequent updates.