Solved: Managing short-lived tokens on VMs — a small open-source config-driven solution

The Perpetual Headache: Managing Short-Lived Tokens on VMs

Short-lived access tokens are a security best practice, but they introduce operational complexities for applications running on Virtual Machines (VMs) that require access to external resources. Without automated refresh mechanisms, applications can experience outages and security vulnerabilities.

Why This Matters

Ideal security models leverage short-lived tokens, but the reality is maintaining these tokens introduces significant operational overhead. Manual token renewal is prone to errors and doesn’t scale, while poorly implemented automation can create new security risks. The cost of application downtime due to expired tokens can easily reach tens of thousands of dollars per hour for critical services.

Key Insights

• Manual scripting for token renewal is a high-risk practice: It often involves hardcoding secrets and lacks scalability.
• Cloud provider IAM roles offer a secure alternative: AWS Instance Profiles, Azure Managed Identities, and GCP Service Accounts automatically manage token rotation without storing long-lived keys on the VM.
• TokenRelay addresses hybrid environments: A config-driven agent can securely fetch tokens from various sources for diverse external services.

Working Example

#!/bin/bash
# Configuration
CLIENT_ID="your_client_id"
CLIENT_SECRET="your_client_secret" # In a real scenario, fetch this from a secure store
TOKEN_ENDPOINT="https://oauth.example.com/token"
TOKEN_FILE="/opt/app/current_token.txt"
LOG_FILE="/var/log/token_renew.log"
# Function to log messages
log_message() {
echo "$(date '+%Y-%m-%d %H:%M:%S') - $1" >> "$LOG_FILE"
}
log_message "Starting token renewal process..."
# Request a new token
RESPONSE=$(curl -s -X POST "$TOKEN_ENDPOINT" \
-H "Content-Type: application/x-www-form-urlencoded" \
-d "grant_type=client_credentials&client_id=$CLIENT_ID&client_secret=$CLIENT_SECRET")
ACCESS_TOKEN=$(echo "$RESPONSE" | jq -r '.access_token')
if [[ -z "$ACCESS_TOKEN" || "$ACCESS_TOKEN" == "null" ]]; then
log_message "ERROR: Failed to retrieve access token. Response: $RESPONSE"
exit 1
fi
# Store the new token
echo "$ACCESS_TOKEN" > "$TOKEN_FILE"
chmod 600 "$TOKEN_FILE" # Restrict permissions
log_message "Successfully renewed token. Stored in $TOKEN_FILE."
# Optional: Signal or restart the application
# For example, if your application picks up environment variables on restart:
# systemctl restart my-application.service
# Or, if your application has a reload endpoint:
# curl -X POST http://localhost:8080/reload-token
log_message "Token renewal process completed."

Practical Applications

• Financial Institution: Using cloud IAM roles to grant VMs access to a database without storing database credentials on the VM itself, ensuring PCI compliance.
• Pitfall: Hardcoding API keys directly into application code, leading to potential exposure if the code is compromised or accidentally committed to a public repository.

References:

• https://dev.to/techresolve/solved-managing-short-lived-tokens-on-vms-a-small-open-source-config-driven-solution-2lj3