HARBleed: When History Doesn't Repeat, But It Does Rhyme


The cybersecurity landscape is often marked by high-profile incidents that serve as learning pivots. The recent security incident involving Okta, a leading identity management provider, underscores this fact. While it’s not a vulnerability in the code itself, the incident shares a thematic lineage with one of the most notorious security lapses in history: Heartbleed. For clarity, let’s delve into this concept that I choose to term “HARBleed,” highlighting its procedural kinship with Heartbleed and emphasizing the lurking danger represented by bearer tokens.

Heartbleed: A Flashback

In 2014, Heartbleed, a serious vulnerability in the OpenSSL cryptographic library, grabbed headlines. It allowed attackers to read sensitive data from the memory of millions of web servers, exposing user passwords, server private keys, and notably, bearer tokens—those digital keys that authenticate interactions between users and servers. This wasn’t just a code flaw; it was a systemic failure that exposed the foundational cracks in how we manage data transactions.

The Okta Incident: A Procedural Misstep, Not a Code Flaw

Fast forward to the present day, and we find ourselves examining the Okta incident through a similar lens, though the technicalities differ substantially. Here’s what happened: Okta’s support team, aiming to expedite resolution of user issues, asked customers to upload HAR (HTTP Archive) files. These files, unbeknownst to many, contained session cookies—effectively bearer tokens—that authenticate a user to the Okta Administrative Portal.

The crux of the incident wasn’t a nefarious code vulnerability. Instead, it was a perilous oversight in the workflow, where sensitive files could be—and were—accessed by attackers. These threat actors then impersonated administrative users, penetrating customer environments via the Okta Admin Portal. It’s a stark reminder that sometimes, the chinks in our cybersecurity armor are people and process, and not specifically technology.

This incident, which I propose we refer to as “HARBleed,” isn’t about the technical bleed but rather the conceptual bleed of security stemming from bearer tokens’ exposure. Though the means differ—Heartbleed was a code vulnerability, HARBleed a procedural misstep—the effect, particularly the risk posed by unsecured bearer tokens, rhymes with historical context.

Bearer tokens, the actual enemy here, are a relic of a bygone era, inadequate for today’s security demands. They represent an Achilles’ heel, given that any party in possession of these tokens can misuse them, authenticated by the very systems meant to protect access.

Why the Focus Should Be on Bearer Tokens, Not HAR Files

Some might argue that sanitizing HAR files could be the solution. However, this is a red herring. The true issue isn’t the HAR files themselves but the authentication tokens within them. Focusing on sanitizing these files is akin to treating a symptom, ignoring the disease. Moreover, the concept of sanitization relies heavily on end-users’ vigilance, an inconsistent variable and, frankly, an unrealistic expectation.

Looking Ahead: The Asymmetric Cryptography Salvation

In the aftermath of breaches like HARBleed, it becomes clear that our current security frameworks, particularly those relying on bearer tokens, are fragile. They operate under an assumption of confidentiality that doesn’t hold in the real world. Herein lies the beauty of asymmetric cryptography offered by mechanisms like newly standardized RFC 9449 OAuth 2.0 Demonstrating Proof of Possession (everyone just calls it DPoP for short!), serving as a robust line of defense against token misuse and replay attacks.

The Mechanics of DPoP

With DPoP, we introduce a cryptographic signature to the standard OAuth 2.0 protocol, wherein tokens are bound to a specific browser and device. While the RFC is written in the context of OAuth 2.0 flows, it can easily be used as a reference guide for general purpose application session management. Clients, in this case, the user’s browser or app, must provide a public key, with each request carrying a signature created using the corresponding private key. This signature is unique per request, encompassing the request’s specific details (issuance time, HTTP method, target URL, etc.), and is passed along in the DPoP header.  

But here’s the kicker: servers respond to these requests by issuing a unique nonce, a temporary opaque value that must accompany subsequent communications. This nonce, combined with the tracking of jti (JWT ID) values that are intrinsic to each DPoP proof, ensures that no token can be illicitly replayed. In simpler terms, even if an attacker manages to intercept a HAR file and extract a token, they cannot misuse it, as they lack the private key required to generate a valid new signature for further requests.

Why This Matters for HARBleed and Heartbleed:

Let’s take a step back and consider Heartbleed. This notorious incident allowed attackers to read an incredible amount of the web’s encrypted traffic, compromising session tokens left and right. If DPoP had been standard practice, the tokens, even if intercepted, would have been useless without the accompanying private keys and nonce to authorize further transactions or requests.

Fast forward to HARBleed, where the sharing of HAR files inadvertently shared sensitive session details. DPoP would have rendered this breach a non-issue. Attackers, upon obtaining any tokens from these HAR files, would be stone-walled, unable to generate the unique signatures necessary for additional requests, thanks to the absence of the necessary private keys and the server-side nonce.

The Road Ahead: DPoP is not easy

The implementation of DPoP does indeed require dedicated efforts on both the client and server sides. While JavaScript or mobile clients would need to handle DPoP header construction and signing, servers must manage nonce creation and jti tracking, ensuring they accept only appropriately signed requests. This collaboration fortifies the request-response cycle, making it resistant to both interception and replay.The cost of building and maintaining state for DPoP style schemes might be too high for every session, in every part of every application, but the computer costs are easily justified for our most sensitive applications, or on sessions with administrative privileges.

Admittedly, we’re tackling sophisticated issues without the luxury of browser-native support, akin to the seamless operation of WebAuthn/FIDO2.  A proposal like WebSessions might make this implementation materially easier, but it is still an immature proposal. The community’s ambition, though, should be advocating for similar standardization and integration for DPoP. Until that day comes, leveraging existing RFC protocols like DPoP isn’t just a makeshift solution; it’s a proactive, security-enhancing choice.

By embracing DPoP, we’re not just putting a band-aid on the vulnerabilities exposed by HARBleed and Heartbleed. We’re restructuring the very foundations of secure web traffic, championing a future where data interception doesn’t equate to a security breach.

Concluding Thoughts: Learning from Incidents, Not Assigning Blame

The “HARBleed” incident, exposing flaws within Okta’s support processes, dragged several high-profile names into the fray. Cloudflare, 1Password, BeyondTrust, and others found themselves collateral victims of a larger issue they could do little to prevent.  They have a right to be upset with Okta.  The response could have been handled better, and there is a thread of least privilege and threat detection that must also improve.

But here’s the crux: while it’s easy to fault Okta for their response, the real adversary is the outdated security practice of using bearer tokens. It’s a widespread issue, extending far beyond individual companies. “HARBleed” is merely a symptom of a more extensive systemic vulnerability.

It’s time for an industry-wide upgrade, championing preventative measures over reactive solutions. By adopting proven standards like RFC 9449, we’re future-proofing, taking strides toward making incidents like “HARBleed” relics of the past.