Borrowing it
Nothing to install: this file belongs to greenpau/go-authcrunch. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/greenpau/go-authcrunch/main/.codex/skills/local-password-authentication/SKILL.mdgit clone --depth 1 https://github.com/greenpau/go-authcrunchWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/greenpau/go-authcrunch/local-password-authentication)<a href="https://agentmods.dev/skills/greenpau/go-authcrunch/local-password-authentication"><img src="https://agentmods.dev/badge/skills/greenpau/go-authcrunch/local-password-authentication/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/greenpau/go-authcrunch/local-password-authentication"><img src="https://agentmods.dev/badge/skills/greenpau/go-authcrunch/local-password-authentication.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00046 | $0.02037 |
| Opus 5 | $0.00023 | $0.01019 |
| Sonnet 5 | $0.00009 | $0.00407 |
| Haiku 4.5 | $0.00005 | $0.00204 |
Grade A, and why
local-password-authentication scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 186 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Local Password Authentication
Ownership
pkg/identity/database.go owns Database.AuthenticateUser and identity lookup.
pkg/identity/password_verifier.go owns passwordVerifier,
newPasswordVerifier, and activePasswordCost. Keep enumeration defenses at
this shared database boundary so HTML, JSON, and other authentication callers
receive the same protection.
The local adapter delegates through pkg/ids/local/store.go and
pkg/ids/local/authenticator.go. HTML password challenges reach it from
pkg/authn/handle_http_sandbox.go; JSON challenges use
pkg/authn/handle_json_login.go.
pkg/identity/password.go owns password creation/import and Password.Match.
User.VerifyPassword in pkg/identity/user.go still serves credential-change
checks. Substituting that per-user method for the database's store-wide verifier
would remove work equalization. Client protocol and refresh-evidence lifecycle
changes belong to their separate owning skills.
Password Management
pkg/identity/user.go owns AddPassword, ResetPassword, ChangePassword, and
UpdatePassword. Their shared replacement helper installs a validated active
record and disables retained older records. Keep these mutation semantics
separate from the authentication verifier's raw-plaintext comparison schedule.
- Validate replacement input through NewPassword before mutating credentials. Creation/import trims surrounding whitespace; duplicate comparison uses that same normalized input. Validation must still reject invalid imports and overlength plaintext even if a comparison could match an existing hash.
- For plaintext duplicates, compare against the first active record with Password.Match. For bcrypt imports, compare the parsed encoded hash directly; never verify the serialized import string as though it were plaintext.
- A matching first record is reusable only while enabled and unexpired. AddPassword retains its hash, timestamps, and existing history when reusable. It must still disable other enabled password records. A duplicate is a complete no-op only when there are no such records left to revoke.
- Do not return early from UpdatePassword merely because VerifyPassword accepts the candidate: another active credential may need revocation.
- ResetPassword always installs a fresh active record, even when the plaintext or imported hash is unchanged. Validate before disabling the old credential; a failed reset must leave credentials usable and state unchanged.
- ChangePassword still verifies the old password before replacing credentials. Database mutation wrappers must continue advancing CredentialVersion and persisting it even when the active hash is reused. Hash deduplication does not preserve refresh eligibility.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- yesterday First seen · 186 lines · 46 tokens per session scan A ffdac880341e
local-password-authentication is a skill published in the GitHub repository greenpau/go-authcrunch (59 stars, last pushed yesterday), licensed Apache-2.0. It adds 46 tokens to every session and 2,037 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-13.
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