Just built a custom query to flag hardcoded AWS keys in our configs

Interesting approach, focusing on the surrounding context lines in config files. That's a smart way to cut down on false positives from documentation or comments.

One thing I'd watch for is the potential for key prefixes to evolve. AWS has introduced other prefixes beyond `AKIA` for IAM roles and specific services. You might want to keep an eye on their documentation and expand your pattern match accordingly over time.

Have you considered integrating this query into a pre-commit hook for those test branches? It could catch the issue before it even hits the SAST scan.

Good point on key prefixes. The current regex pattern also matches `ASIA` for temporary keys, which is critical. Missing those would be a major gap.

Pre-commit hooks are the correct layer for this. Running the SAST query there is too heavy. A simple grep with the same pattern is faster and blocks the commit immediately.

We had to whitelist a few directories for vendor configs to make it usable.

The `ASIA` inclusion is non-negotiable for coverage. I'd also add a check for the secret access key pattern. A standalone `AKIA` without its corresponding 40-character secret is often a false positive in sample configs, but both together is a high-confidence match.

Your whitelist approach is practical. We extended ours to exclude any path containing `/node_modules/` or `/vendor/` by default, which handled most of the noise.

Have you measured the runtime impact of the grep in your pre-commit hook? In a large monorepo, even a simple pattern scan can become noticeable.

The secret key check is a solid improvement. But runtime impact? That's the wrong metric. The real cost is when these keys leak and some crypto miner spins up a fleet of p3.16xlarges in your test account.

Scanning every commit is cheap compared to a surprise $40k bill. If your grep is too slow, you're probably scanning your entire .git history instead of just the staged changes.

Precisely. The commit-stage scan cost is trivial, and focusing on it misses the threat model.

The real failure mode is when a branch with a committed key gets pushed to a public fork, or even just shared internally via a CI log. Automated scrapers don't care if it's a test branch.

You have to grep the staged changes. If you're scanning the whole tree, you're doing it wrong and of course it's slow. `git diff --cached --name-only | xargs grep -E` is the way.

Absolutely correct on the git diff command. It's the only sane way. That said, the grep pattern itself can still be a bottleneck if you get too clever - stick to simple regex.

Also, make sure your hook fails *hard*. No warnings, no exit code 0 on a match. The number of hooks I've seen that just `echo "DON'T DO THIS"` and let the commit sail through... painful.

That context trick with surrounding lines for config keywords is exactly right. It's the difference between a query that fires 500 times and one that fires on the 5 actual leaks.

You can get even tighter by also checking the file path in the query logic - flagging anything under `config/` or `conf/` directories, or with `.yaml/.yml/.json/.properties` extensions, while ignoring `docs/` or `*.md`. It reduces the regex complexity.

Absolutely right on filtering by path and extension - that's where you get signal over noise. The regex engine spends less time sifting through README files full of example code.

One caveat: I've seen teams get burned by over-restricting paths. Someone drops a `terraform.tfvars` in the root or a `.env.production` in an unexpected location, and your filtered scan misses it. Better to maintain a small, focused denylist of actual high-noise directories (like `/vendor/`) rather than trying to predefine every valid config location.

The file extension check is solid though - maybe add `.tfvars` and `.env*` to that list while you're at it.

> the trick was to look for the AWS key pattern... and the secret key pattern, but also to limit the context to configuration-type files

That's clever, but you're still trusting your regex to find the secret. The 40-char secret regex is brittle. It's a lower-case hex string. What about keys that get base64 encoded or wrapped in a variable? You'll miss them.

The config keyword context is good, but relying on a pattern match for the secret creates a false sense of security. The primary signal should be the access key ID. If you find an AKIA or ASIA in a config file, that's the leak. The presence of a matching secret is just a higher severity finding.

You're right that the secret key regex can be brittle, but I think the combo is still valuable. If you flag on AKIA alone, you'll drown in false positives from documentation, example code, and internal tooling that mentions key patterns without actual credentials. The secret check, even if imperfect, raises the confidence level enough to make the alert actionable.

The real failure case isn't a base64-encoded secret, it's a developer seeing 50 "possible key" alerts a day and just ignoring them all. The secret pattern, even with gaps, helps keep the signal-to-noise ratio usable. That said, your point about treating a standalone AKIA in a config file as a leak is correct - maybe it should be a lower severity warning rather than being ignored.

You make a solid point about the stand-alone access key ID being the core leak. The secret just makes it operational.

But that's also why the 40-char secret regex is *functionally* adequate, even if theoretically brittle. The real risk isn't a developer deliberately base64-ing a secret in a config - that's still a plaintext secret. It's the accidental paste from the console. The AWS console and CLI output those secrets as 40-char hex strings, and that's what gets copied 99% of the time.

Treating an AKIA in a config as a P1 leak and a AKIA+secret pattern as a P0 gives you actionable triage. You can batch-review the P1s, but you need to page on the P0s immediately. That's the signal-to-noise management the secret check provides, even with its gaps.

You're correct that the primary leak is the access key ID. But calling the 40-char secret regex "brittle" misses how these leaks actually happen. It's not about an adversary deliberately obfuscating a secret in a config file. It's about a developer pasting the literal output from the AWS console or a CLI command.

If someone is base64-encoding a secret and then putting that into a config, they've already made a conscious decision to hide a plaintext credential. Your grep hook isn't going to save you from that level of intentional circumvention. The threat model is the accidental paste, and for that, the hex string pattern is a perfect match.

That said, I agree that an isolated AKIA in a config file is a high-confidence finding and should be flagged. But you can't treat it with the same urgency as a key-secret pair, or your team will start ignoring all alerts. The secret pattern provides the necessary signal boost to prioritize the truly dangerous commits.

That's a smart approach to narrow the scope. I've found you can extend that config keyword logic even further for languages like Terraform, where the structure is more rigid. For instance, you can look for patterns inside a `provider "aws"` block, which is almost always a config location.

But one issue with that line-based context check is multi-line YAML strings or JSON values split across lines. Your regex might miss the keyword if the line break falls between `aws_access_key_id:` and the actual `AKIA...` value. Sometimes you need to check a few lines before and after, or even consider the entire logical block.

Yep, multi-line YAML is the killer. Your line-based grep just dies there.

The real fix is parsing, not regex. For Terraform, use `terraform fmt` and `terraform validate` - a malformed provider block fails. For YAML, even a simple yamllint call before your grep ensures the structure is sound, so your line checks actually work. Regex on raw source is a last resort.

> treat the entire logical block

Exactly. If you're stuck with grep, use `-A 3 -B 1` to get a few lines of context. But that's just papering over the crack.