Developer workstation security covering SSH key management, GPG signing, credential stores, file permissions, agent forwarding, IDE hardening, and browser extension auditing.

Treat the developer workstation as a critical supply chain node. A compromised dev machine means compromised code, credentials, and infrastructure access. Follow these workflows to harden each surface.

SSH Hardening Workflow

Generate an Ed25519 key per service. One key for GitHub, another for production servers, another for cloud.
Protect the private key with a passphrase. Load it into ssh-agent so you type it once.
Lock permissions on the .ssh directory and all key files.
Configure ~/.ssh/config to use ProxyJump instead of agent forwarding.
Rotate keys annually. Remove old public keys from every authorized service.

# Step 1: Generate a dedicated key
ssh-keygen -t ed25519 -C "github@workstation" -f ~/.ssh/id_ed25519_github

# Step 2: Add to agent with passphrase caching
ssh-add ~/.ssh/id_ed25519_github

# Step 3: Lock permissions
chmod 700 ~/.ssh
chmod 600 ~/.ssh/id_ed25519_*
chmod 644 ~/.ssh/*.pub

# Step 5: Verify fingerprint before trusting a key
ssh-keygen -l -f ~/.ssh/id_ed25519_github.pub

BAD - Single key reused everywhere, no passphrase, open permissions:

ssh-keygen -t rsa -b 2048 -N "" -f ~/.ssh/id_rsa
chmod 755 ~/.ssh
# Same key added to GitHub, AWS, production bastion, personal VPS

GOOD - Dedicated Ed25519 key, passphrase, tight permissions:

ssh-keygen -t ed25519 -C "github@workstation" -f ~/.ssh/id_ed25519_github
chmod 700 ~/.ssh
chmod 600 ~/.ssh/id_ed25519_github

BAD - Agent forwarding to untrusted host:

Host bastion
  HostName bastion.example.com
  ForwardAgent yes

GOOD - ProxyJump through bastion, no agent exposure:

Host bastion
  HostName bastion.example.com

Host production
  HostName 10.0.1.50
  ProxyJump bastion

Windows OpenSSH Agent Setup

# Enable and start the agent service (persists across reboots)
Get-Service ssh-agent | Set-Service -StartupType Automatic
Start-Service ssh-agent

# Add key once
ssh-add $HOME\.ssh\id_ed25519_github

# Point Git to Windows OpenSSH instead of bundled ssh
git config --global core.sshCommand "C:/Windows/System32/OpenSSH/ssh.exe"

# Verify
ssh-add -l

GPG Signing Setup

Install GPG tooling (Gpg4win on Windows, gnupg on Linux/macOS).
Generate a key with RSA 4096 or Ed25519. Set expiration to 1-2 years.
Configure Git to sign all commits automatically.
Export the public key and upload to GitHub/GitLab.
Back up the private key to an encrypted offline location.

# Step 2: Generate key
gpg --full-generate-key

# Step 2b: Find your key ID
gpg --list-secret-keys --keyid-format=long
# Output: sec   ed25519/ABC123DEF456 2024-01-01 [SC] [expires: 2026-01-01]

# Step 3: Configure Git
git config --global commit.gpgsign true
git config --global user.signingkey ABC123DEF456

# Step 4: Export public key (pipe to clipboard or file)
gpg --armor --export ABC123DEF456 > gpg-public.asc

# Windows: point Git to Gpg4win binary
git config --global gpg.program "C:/Program Files (x86)/GnuPG/bin/gpg.exe"

BAD - No expiration, no signing configured:

gpg --gen-key   # Defaults to no expiration
# Never configure git commit.gpgsign
# Commits show as "Unverified" on GitHub

GOOD - Expiring key, auto-signing enabled:

gpg --full-generate-key  # Choose Ed25519, set 2-year expiry
git config --global commit.gpgsign true
git config --global user.signingkey ABC123DEF456
# Commits show "Verified" badge on GitHub

Credential Management

Configure a Git credential helper for your OS.
Eliminate plaintext secrets from shell history, dotfiles, and scripts.
Install gitleaks as a pre-commit hook to catch accidental leaks.
Use a secrets manager for scripts that need credentials at runtime.

# Step 1: Git credential helper
git config --global credential.helper manager   # Windows
git config --global credential.helper osxkeychain  # macOS
git config --global credential.helper store      # Linux (plaintext fallback)

# Step 3: Install gitleaks pre-commit
gitleaks detect --source . --verbose

# Step 4: Inject secrets from 1Password CLI (never in env or code)
op read "op://Development/github-token/credential"

BAD - Token hardcoded in script:

GITHUB_TOKEN="ghp_abc123secrettoken"
curl -H "Authorization: token $GITHUB_TOKEN" https://api.github.com/user

GOOD - Token pulled from credential store at runtime:

GITHUB_TOKEN=$(op read "op://Development/github-token/credential")
curl -H "Authorization: token $GITHUB_TOKEN" https://api.github.com/user

File Permissions Audit

Scan home directory for world-readable sensitive files.
Fix permissions on SSH keys, cloud configs, token files.
Verify after cloning repos. Git does not preserve full Unix permissions.

# Step 1: Find sensitive files with bad permissions
find ~ -maxdepth 3 -name ".netrc" -o -name ".npmrc" -o -name "credentials" \
  -o -name ".env" -o -name "*.pem" | xargs ls -la

# Step 2: Lock down sensitive files
chmod 600 ~/.netrc ~/.npmrc ~/.config/gh/hosts.yml
chmod 600 ~/.aws/credentials ~/.config/gcloud/*.json
chmod 700 ~/.gnupg

# Step 3: Verify SSH directory after any change
ls -la ~/.ssh/

BAD - World-readable credentials:

-rw-r--r-- 1 dev dev 256 Jan 1 ~/.netrc
-rwxrwxrwx 1 dev dev 512 Jan 1 ~/.ssh/id_ed25519
drwxr-xr-x 2 dev dev 4096 Jan 1 ~/.aws

GOOD - Owner-only access:

-rw------- 1 dev dev 256 Jan 1 ~/.netrc
-rw------- 1 dev dev 512 Jan 1 ~/.ssh/id_ed25519
drwx------ 2 dev dev 4096 Jan 1 ~/.aws

IDE and Extension Hardening

List all installed extensions. Remove any unused ones immediately.
Pin extension versions in team workspace settings.
Check .vscode/settings.json and .idea/ for leaked tokens or local paths before committing.
Use remote development (SSH, containers) for sensitive codebases.

# List VS Code extensions
code --list-extensions

# Check workspace settings for leaked paths or tokens
grep -r "token\|secret\|password\|C:\\\\Users" .vscode/ .idea/ 2>/dev/null

Maintenance Schedule

Monthly:   Rotate temp credentials. Review ssh-add -l. Check OS updates.
Quarterly: Audit browser + IDE extensions. Run gitleaks detect on all repos.
Annually:  Rotate SSH and GPG keys. Full permissions audit. Update threat model.
Incident:  Assume compromise. Rotate ALL credentials. Audit access logs.

Use this skill: When setting up a new workstation, onboarding a team member, or after any security incident that may have exposed developer credentials.

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