mcpbeat

Secret Handling

microsoft/generative-ai-for-beginners-dotnet-secret-handling

Never read .env files or write secrets to .squad/ committed files

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on the repository, not the skill itself

Install

one command, takes just this skill from the repository
npx skills add https://github.com/microsoft/Generative-AI-for-beginners-dotnet --skill secret-handling

The instruction itself

11 sections, as written by the author

Context

Spawned agents have read access to the entire repository, including .env files containing live credentials. If an agent reads secrets and writes them to .squad/ files (decisions, logs, history), Scribe auto-commits them to git, exposing them in remote history. This skill codifies absolute prohibitions and safe alternatives.

Patterns

Prohibited File Reads

NEVER read these files:

  • .env (production secrets)
  • .env.local (local dev secrets)
  • .env.production (production environment)
  • .env.development (development environment)
  • .env.staging (staging environment)
  • .env.test (test environment with real credentials)
  • Any file matching .env.* UNLESS explicitly allowed (see below)

Allowed alternatives:

  • .env.example (safe — contains placeholder values, no real secrets)
  • .env.sample (safe — documentation template)
  • .env.template (safe — schema/structure reference)

If you need config info:

  • Ask the user directly — "What's the database connection string?"
  • Read .env.example — shows structure without exposing secrets
  • Read documentation — check README.md, docs/, config guides

NEVER assume you can "just peek at .env to understand the schema." Use .env.example or ask.

Prohibited Output Patterns

NEVER write these to .squad/ files:

| Pattern Type | Examples | Regex Pattern (for scanning) |

|--------------|----------|-------------------------------|

| API Keys | OPENAI_API_KEY=sk-proj-..., GITHUB_TOKEN=ghp_... | [A-Z_]+(?:KEY|TOKEN|SECRET)=[^\s]+ |

| Passwords | DB_PASSWORD=super_secret_123, password: "..." | (?:PASSWORD|PASS|PWD)[:=]\s*["']?[^\s"']+ |

| Connection Strings | postgres://user:pass@host:5432/db, Server=...;Password=... | (?:postgres|mysql|mongodb)://[^@]+@|(?:Server|Host)=.*(?:Password|Pwd)= |

| JWT Tokens | eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9... | eyJ[A-Za-z0-9_-]+\.eyJ[A-Za-z0-9_-]+\.[A-Za-z0-9_-]+ |

| Private Keys | -----BEGIN PRIVATE KEY-----, -----BEGIN RSA PRIVATE KEY----- | -----BEGIN [A-Z ]+PRIVATE KEY----- |

| AWS Credentials | AKIA..., aws_secret_access_key=... | AKIA[0-9A-Z]{16}|aws_secret_access_key=[^\s]+ |

| Email Addresses | [email protected] (PII violation per team decision) | [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,} |

What to write instead:

  • Placeholder values: DATABASE_URL=<set in .env>
  • Redacted references: API key configured (see .env.example)
  • Architecture notes: "App uses JWT auth — token stored in session"
  • Schema documentation: "Requires OPENAI_API_KEY, GITHUB_TOKEN (see .env.example for format)"

Scribe Pre-Commit Validation

Before committing .squad/ changes, Scribe MUST:

  • Scan all staged files for secret patterns (use regex table above)
  • Check for prohibited file names (don't commit .env even if manually staged)
  • If secrets detected:
  • STOP the commit (do NOT proceed)
  • Remove the file from staging: git reset HEAD <file>
  • Report to user:
     🚨 SECRET DETECTED — commit blocked
     
     File: .squad/decisions/inbox/river-db-config.md
     Pattern: DATABASE_URL=postgres://user:password@localhost:5432/prod
     
     This file contains credentials and MUST NOT be committed.
     Please remove the secret, replace with placeholder, and try again.
  • Exit with error (never silently skip)
  • If no secrets detected:
  • Proceed with commit as normal

Implementation note for Scribe:

  • Run validation AFTER staging files, BEFORE calling git commit
  • Use PowerShell Select-String or git diff --cached to scan staged content
  • Fail loud — secret leaks are unacceptable, blocking the commit is correct behavior

Remediation — If a Secret Was Already Committed

If you discover a secret in git history:

  • STOP immediately — do not make more commits
  • Alert the user:
   🚨 CREDENTIAL LEAK DETECTED
   
   A secret was found in git history:
   Commit: abc1234
   File: .squad/decisions/inbox/agent-config.md
   Pattern: API_KEY=sk-proj-...
   
   This requires immediate remediation:
   1. Revoke the exposed credential (regenerate API key, rotate password)
   2. Remove from git history (git filter-repo or BFG)
   3. Force-push the cleaned history
   
   Do NOT proceed with new work until this is resolved.
  • Do NOT attempt to fix it yourself — secret removal requires specialized tools
  • Wait for user confirmation before resuming work

Examples

✓ Correct: Reading Config Schema

Agent needs to know what environment variables are required:

Agent: "What environment variables does this app need?"
→ Reads `.env.example`:
    OPENAI_API_KEY=sk-...
    DATABASE_URL=postgres://user:pass@localhost:5432/db
    REDIS_URL=redis://localhost:6379

→ Writes to .squad/decisions/inbox/river-env-setup.md:
    "App requires three environment variables:
    - OPENAI_API_KEY (OpenAI API key, format: sk-...)
    - DATABASE_URL (Postgres connection string)
    - REDIS_URL (Redis connection string)
    See .env.example for full schema."

✗ Incorrect: Reading Live Credentials

Agent needs to know database schema:

Agent: (reads .env)
    DATABASE_URL=postgres://admin:[email protected]:5432/appdb

→ Writes to .squad/decisions/inbox/river-db-schema.md:
    "Database connection: postgres://admin:[email protected]:5432/appdb"
    
🚨 VIOLATION: Live credential written to committed file

Correct approach:

Agent: (reads .env.example OR asks user)
User: "It's a Postgres database, schema is in migrations/"

→ Writes to .squad/decisions/inbox/river-db-schema.md:
    "Database: Postgres (connection configured in .env). Schema defined in db/migrations/."

✓ Correct: Scribe Pre-Commit Validation

Scribe is about to commit:

# Stage files
git add .squad/

# Scan staged content for secrets
$stagedContent = git diff --cached
$secretPatterns = @(
    '[A-Z_]+(?:KEY|TOKEN|SECRET)=[^\s]+',
    '(?:PASSWORD|PASS|PWD)[:=]\s*["'']?[^\s"'']+',
    'eyJ[A-Za-z0-9_-]+\.eyJ[A-Za-z0-9_-]+\.[A-Za-z0-9_-]+'
)

$detected = $false
foreach ($pattern in $secretPatterns) {
    if ($stagedContent -match $pattern) {
        $detected = $true
        Write-Host "🚨 SECRET DETECTED: $($matches[0])"
        break
    }
}

if ($detected) {
    # Remove from staging, report, exit
    git reset HEAD .squad/
    Write-Error "Commit blocked — secret detected in staged files"
    exit 1
}

# Safe to commit
git commit -F $msgFile

Anti-Patterns

  • ❌ Reading .env "just to check the schema" — use .env.example instead
  • ❌ Writing "sanitized" connection strings that still contain credentials
  • ❌ Assuming "it's just a dev environment" makes secrets safe to commit
  • ❌ Committing first, scanning later — validation MUST happen before commit
  • ❌ Silently skipping secret detection — fail loud, never silent
  • ❌ Trusting agents to "know better" — enforce at multiple layers (prompt, hook, architecture)
  • ❌ Writing secrets to "temporary" files in .squad/ — Scribe commits ALL .squad/ changes
  • ❌ Extracting "just the host" from a connection string — still leaks infrastructure topology

Repackaged in 1 other repositories

same content, different owner
microsoft/waza open on GitHub →

How to use it

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