How Hardcoded AWS Secret Access Keys Happen in Configuration Files and How to Fix Them

How Hardcoded AWS Secret Access Keys Happen in Configuration Files and How to Fix Them

Vulnerability at a Glance

Summary

A hardcoded AWS Secret Access Key pattern was detected in the settings.example configuration file of an nginx AWS credentials module. While the value itself was a placeholder string, its format matched a real AWS secret key pattern, making it a dangerous template that could mislead developers into committing real credentials. The fix replaces the lookalike secret value with an unambiguous placeholder that cannot be mistaken for or used as a real credential.

Introduction

The settings.example file in this nginx AWS credentials library exists for one purpose: to show developers exactly what their environment configuration should look like before they deploy. That's a useful thing to have. But there's a subtle trap hiding in example files — if the placeholder values you choose look too much like real secrets, you've created a template that trains developers to put real secrets in the wrong place.

That's precisely what happened here. At line 3 of settings.example, the AWS_SECRET_ACCESS_KEY variable was set to:

AWS_SECRET_ACCESS_KEY=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

That 40-character all-lowercase string is not a real AWS credential — but it is formatted exactly like one. AWS Secret Access Keys are 40-character base64 strings. Semgrep's rule generic.secrets.security.detected-aws-secret-access-key matched it immediately, and for good reason: any automated tool scanning a repository that inherits this file would flag it as a potential live credential.

This matters especially because this is a Node.js library — vulnerabilities and patterns in it propagate to every downstream project that uses it as a dependency or copies its configuration as a starting point.

The Vulnerability Explained

What Made This Risky?

AWS Secret Access Keys follow a well-known format: exactly 40 characters, alphanumeric, base64-encoded. Secret scanning tools — including Semgrep, TruffleHog, GitLeaks, and GitHub's own push protection — use regular expressions to match this pattern. The original placeholder:

# settings.example — BEFORE the fix (line 3)
AWS_SECRET_ACCESS_KEY=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

passes that regex check. The string is 40 characters long and composed entirely of valid base64 characters. From a scanner's perspective, this is indistinguishable from a real secret.

The Exploit Primitive

The term "exploit primitive" is apt here. The value itself isn't exploitable — aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa won't authenticate against any real AWS account. But this pattern creates two concrete risks:

Risk 1: Developer Confusion
A developer sets up the project for the first time, copies settings.example to .env, and replaces the obviously fake values — but misses AWS_SECRET_ACCESS_KEY because it already looks like it has a value. They paste their real key next to it in a comment, or accidentally leave a real key in a file they thought was already sanitized.

Risk 2: Downstream Scanner Fatigue
Projects that inherit or copy this configuration will have Semgrep, TruffleHog, or their CI pipeline flag this line on every scan. Teams that see this false positive repeatedly may begin to suppress or ignore the rule — exactly the behavior that allows real secrets to slip through undetected.

Real-World Context: awscredentials.js

This settings.example file is the configuration template for common/etc/nginx/include/awscredentials.js — a module that handles AWS credential fetching via IMDS, ECS, EKS Pod Identity Agent, and STS. The credentials configured here are used to authenticate outbound calls to AWS services. A real secret key in this position would grant full programmatic AWS access scoped to the associated IAM role or user.

The full context of the vulnerable file:

# settings.example — BEFORE the fix
S3_BUCKET_NAME=my-bucket
AWS_ACCESS_KEY_ID=ZZZZZZZZZZZZZZZZZZZZ
AWS_SECRET_ACCESS_KEY=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa   # ← flagged
AWS_SESSION_TOKEN=bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
S3_SERVER=s3.us-east-1.amazonaws.com
S3_SERVER_PORT=443

Notice that AWS_ACCESS_KEY_ID uses ZZZZZZZZZZZZZZZZZZZZ — clearly fake, all uppercase Z's — and AWS_SESSION_TOKEN uses bbb... — also clearly fake. Only AWS_SECRET_ACCESS_KEY used a value that could pass a format check as real.

The Fix

The fix is a single-line change in settings.example, but it carries meaningful security weight:

- AWS_SECRET_ACCESS_KEY=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+ AWS_SECRET_ACCESS_KEY=<YOUR_AWS_SECRET_ACCESS_KEY>

Why This Specific Change Works

The replacement value <YOUR_AWS_SECRET_ACCESS_KEY> has three properties that make it unambiguously safe:

1. Syntactically invalid as a credential: The angle brackets < and > are not valid base64 characters. No AWS SDK, CLI, or API will accept this as a real secret key.

2. Immediately recognizable as a placeholder: The <YOUR_...> convention is a well-established documentation pattern. Any developer reading this file knows they need to replace it.

3. Won't trigger secret scanners: Regex patterns for AWS Secret Access Keys require 40 alphanumeric characters. The angle brackets break the match, so this value will not generate false positives in Semgrep, TruffleHog, or GitHub's push protection.

Before and After

# BEFORE — settings.example line 3
AWS_SECRET_ACCESS_KEY=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

# AFTER — settings.example line 3
AWS_SECRET_ACCESS_KEY=<YOUR_AWS_SECRET_ACCESS_KEY>

The change is minimal in size but significant in intent: it removes an exploit primitive that could contribute to credential exposure in downstream projects.

Key Takeaways

• The format of a placeholder matters as much as its value: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa is 40 alphanumeric characters — the exact shape of a real AWS Secret Access Key — and will trigger secret scanners even though it's fake.
• Example configuration files are a common vector for accidental credential exposure: Developers copy them verbatim; if the placeholder looks real, a real value might end up next to it or replacing it without scrutiny.
• Angle-bracket placeholders (<YOUR_VALUE>) are the safest choice: They are syntactically invalid for every credential format, visually obvious, and universally recognized as "replace this."
• This library's settings.example configures credentials for awscredentials.js, which makes outbound calls to AWS IMDS, ECS, EKS, and STS — meaning a real leaked key here could expose significant AWS infrastructure.
• False positives from fake-but-realistic placeholders cause scanner fatigue, which is itself a security risk: teams that suppress noisy rules stop catching real secrets.

How Orbis AppSec Detected This

• Source: The AWS_SECRET_ACCESS_KEY variable assignment at settings.example:3, where the placeholder value matched the 40-character alphanumeric pattern of a real AWS Secret Access Key
• Sink: The value as written could be directly copied into a real .env file and used to authenticate AWS API calls via the awscredentials.js credential fetching module
• Missing control: No unambiguous signal in the placeholder value that it must be replaced; the format was indistinguishable from a real credential to both automated scanners and human reviewers
• CWE: CWE-798 — Use of Hard-coded Credentials
• Fix: Replaced aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa with <YOUR_AWS_SECRET_ACCESS_KEY>, an angle-bracket token that is syntactically invalid as a credential and clearly communicates intent to the reader

Orbis AppSec automatically detected this vulnerability and opened a pull request with the fix. Try Orbis AppSec on your repositories to find and fix issues like this automatically.

Conclusion

A single line in an example configuration file — AWS_SECRET_ACCESS_KEY=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa — illustrates how easy it is to inadvertently introduce a security risk through well-intentioned documentation. The value was never meant to be a real credential, but its format made it indistinguishable from one to both automated tools and developers under time pressure.

The fix is as simple as it is effective: replace any placeholder that could pass a format check for a real credential with one that cannot. <YOUR_AWS_SECRET_ACCESS_KEY> communicates the same information to a developer setting up the project, but eliminates the risk of scanner fatigue, accidental credential commits, and downstream confusion in projects that inherit this configuration.

For teams building libraries and frameworks — especially those that handle authentication and cloud credentials like awscredentials.js — the example files you ship are part of your security surface. Treat them accordingly.