Repository Security Purge

Permanently removes sensitive data from git history using git-filter-repo. This is a DESTRUCTIVE operation that rewrites commit history.

⚠️ DANGER ZONE ⚠️

This skill:

• Rewrites git history — all commit hashes will change
• Requires force push — will break other clones/forks
• Is irreversible — cannot be undone after force push
• Affects all branches — entire repository history is rewritten

Invocation

/repo-security-purge
"purge secrets from git history"
"remove sensitive data from history"
"clean the git history"

Prerequisites

git-filter-repo

Check if installed:

git-filter-repo --version

If not installed:

# macOS
brew install git-filter-repo

# pip
pip install git-filter-repo

# Linux
apt install git-filter-repo  # or package manager equivalent

Fresh Clone Recommended

git-filter-repo works best on a fresh clone:

git clone --mirror <repo-url> repo-mirror
cd repo-mirror

Workflow

Step 1: Verify Prerequisites

# Check git-filter-repo is installed
git-filter-repo --version

# Check we're in a git repo
git rev-parse --is-inside-work-tree

# Check for uncommitted changes
git status --porcelain

If uncommitted changes exist: Stop and ask user to commit or stash first.

If git-filter-repo not installed: Provide installation instructions and stop.

Step 2: Get Security Scan with History

This skill depends on /repo-security-scan --history for findings. Check for an existing scan:

# Look for today's scan report
ls -t security/*-scan.md 2>/dev/null | head -1

If recent scan exists (today):

• Read the report
• Check if it includes history findings (look for "History scanned: Yes")
• If history was scanned, use this report
• If history was NOT scanned, need to re-run with history

If no recent scan OR history not scanned:

• Inform user: "Running security scan with history to identify items to purge..."
• Invoke /repo-security-scan --history
• Wait for scan to complete
• Read the generated report

Step 3: Parse Scan Report for History Items

Read the scan report and extract items marked as "History" or "HISTORY":

From scan report, extract:
- Files to remove (marked as History - e.g., "certs/server.key (HISTORY)")
- Patterns to scrub (secrets found in history)
- Commit references where secrets were introduced

Build a purge list from the report's history findings.

If no history findings:

No secrets found in git history.

Current file issues (if any) can be fixed with /repo-security-clean.
Nothing to purge from history.

Exit gracefully.

Step 4: Identify Items to Purge

Build a list of:

1. Files to remove entirely:

   • Private keys (.pem, .key)
   • Credential files (.env, credentials.json)
   • Certificates with keys (.p12, .pfx)

2. Patterns to scrub from content:

   • Specific API keys/tokens
   • Passwords
   • Connection strings

Present findings:

Secrets found in git history:

Files to remove:
  - certs/server.key (added in abc123, 15 commits ago)
  - config/.env (added in def456, 42 commits ago)
  - secrets/credentials.json (removed in ghi789, but still in history)

Patterns to scrub:
  - API key "sk-abc123..." found in 3 commits
  - Password "hunter2" found in 2 commits

Step 5: LOUD WARNING

Display prominent warning:

╔══════════════════════════════════════════════════════════════════╗
║                    ⚠️  DESTRUCTIVE OPERATION ⚠️                    ║
╠══════════════════════════════════════════════════════════════════╣
║                                                                  ║
║  You are about to REWRITE GIT HISTORY.                          ║
║                                                                  ║
║  This will:                                                      ║
║    • Change ALL commit hashes in the repository                  ║
║    • Break existing clones, forks, and pull requests             ║
║    • Require FORCE PUSH to update remote                         ║
║    • Be IRREVERSIBLE after force push                            ║
║                                                                  ║
║  Items to purge:                                                 ║
║    • 3 files (certs/server.key, config/.env, ...)               ║
║    • 2 secret patterns                                           ║
║                                                                  ║
║  Affected:                                                       ║
║    • 847 commits will be rewritten                               ║
║    • All branches and tags                                       ║
║                                                                  ║
╚══════════════════════════════════════════════════════════════════╝

Step 6: Require Explicit Confirmation

Do not proceed with a simple yes/no. Require the user to type a specific phrase:

To proceed, type exactly: PURGE HISTORY

> _

Only continue if input matches exactly PURGE HISTORY.

If user types anything else, abort:

Aborted. No changes made.

To clean secrets without rewriting history, use /repo-security-clean instead.

Step 7: Create Backup

Before purging, create a backup:

# Create a backup branch/tag
git tag backup-before-purge-$(date +%Y%m%d)

# Or create full backup
git clone --mirror . ../repo-backup-$(date +%Y%m%d)

Inform user:

Backup created: ../repo-backup-20260118

If something goes wrong, you can restore from this backup.

Step 8: Execute Purge

Remove Files Entirely

# Remove specific files from all history
git-filter-repo --invert-paths --path certs/server.key --path config/.env

# Remove by pattern
git-filter-repo --invert-paths --path-glob '*.pem' --path-glob '*.key'

Scrub Sensitive Content

Create a replacements file (replacements.txt):

sk-abc123def456ghi789jkl012mno345pqr678==>[REDACTED_API_KEY]
hunter2==>[REDACTED_PASSWORD]
mongodb://user:pass@host:27017/db==>mongodb://[REDACTED]@host:27017/db

Apply replacements:

git-filter-repo --replace-text replacements.txt

Remove Large Files (bonus)

# Remove files larger than 10MB from history
git-filter-repo --strip-blobs-bigger-than 10M

Step 9: Verify Purge

# Verify secrets are gone
git log -p --all | grep -E "(sk-abc123|hunter2)" || echo "✓ Secrets removed"

# Check file is gone from all history
git log --all --full-history -- certs/server.key || echo "✓ File purged"

# Run security scan again
# (invoke /repo-security-scan --history)

Step 10: Post-Purge Instructions

╔══════════════════════════════════════════════════════════════════╗
║                     ✓ HISTORY REWRITTEN                          ║
╚══════════════════════════════════════════════════════════════════╝

Purged from history:
  ✓ certs/server.key
  ✓ config/.env
  ✓ secrets/credentials.json
  ✓ 2 secret patterns scrubbed

Backup location: ../repo-backup-20260118

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

⚠️  REQUIRED NEXT STEPS:

1. ROTATE ALL EXPOSED CREDENTIALS
   The secrets were public. Assume they are compromised.
   - [ ] Rotate API key sk-abc123...
   - [ ] Change password for database
   - [ ] Revoke and regenerate any tokens

2. FORCE PUSH TO REMOTE
   ⚠️  This will break existing clones and forks!

   git push --force --all origin
   git push --force --tags origin

3. NOTIFY COLLABORATORS
   All team members must re-clone or run:

   git fetch origin
   git reset --hard origin/master

4. UPDATE FORKS (if applicable)
   Fork owners need to sync with upstream.

5. CLEAN UP BACKUPS
   After verifying everything works:

   rm -rf ../repo-backup-20260118
   git tag -d backup-before-purge-20260118

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Report saved: security/YYYYMMDD-purge.md

Step 11: Generate Report

Write to security/YYYYMMDD-purge.md:

# Security Purge Report

**Repository:** <repo-name>
**Date:** YYYY-MM-DD HH:MM
**Operation:** Git history rewrite

## ⚠️ Destructive Operation Completed

This report documents a git history rewrite operation.

## Items Purged

### Files Removed from History

| File | Originally Added | Commits Affected |
|------|------------------|------------------|
| certs/server.key | abc1234 | 15 |
| config/.env | def5678 | 42 |
| secrets/credentials.json | ghi9012 | 8 |

### Patterns Scrubbed

| Pattern | Replacement | Occurrences |
|---------|-------------|-------------|
| sk-abc123... | [REDACTED_API_KEY] | 3 |
| hunter2 | [REDACTED_PASSWORD] | 2 |

## Statistics

- Commits rewritten: 847
- Branches affected: 5
- Tags affected: 12

## Backup

Location: `../repo-backup-20260118`

## Required Actions

- [ ] Rotate all exposed credentials
- [ ] Force push to remote
- [ ] Notify collaborators
- [ ] Clean up backup after verification

## Verification

```bash
# Verify purge was successful
git log -p --all | grep "sk-abc123" # Should return nothing

## Error Handling

| Error | Resolution |
|-------|------------|
| git-filter-repo not installed | Provide installation instructions |
| Uncommitted changes | Ask user to commit or stash |
| Not a git repository | Abort with message |
| Protected branch on remote | Warn about force push restrictions |
| Confirmation not matched | Abort, no changes made |

## Alternatives

If history rewrite is too disruptive:

1. **Accept the exposure** — rotate credentials, add to .gitignore going forward
2. **Create fresh repo** — copy current files to new repo, lose history
3. **Use BFG Repo-Cleaner** — alternative tool, similar results

## Safety Notes

- This skill will **NEVER** force push automatically
- This skill will **NEVER** proceed without explicit typed confirmation
- This skill will **ALWAYS** create a backup first
- This skill will **ALWAYS** warn about collaborator impact