Bash script to check the certificate expirations in your kubeconfig file

check_kubeconfig.sh

#!/bin/bash

# Function to extract and decode certificate
extract_cert() {
    echo "$1" | base64 -d 2>/dev/null | openssl x509 -noout -enddate 2>/dev/null | cut -d= -f2
}

# Function to calculate days until expiry
days_until_expiry() {
    local expiry_date="$1"
    local current_date=$(date -u +"%b %d %H:%M:%S %Y GMT")
    local expiry_seconds=$(date -j -f "%b %d %H:%M:%S %Y GMT" "$expiry_date" "+%s")
    local current_seconds=$(date -j -f "%b %d %H:%M:%S %Y GMT" "$current_date" "+%s")
    echo $(( (expiry_seconds - current_seconds) / 86400 ))
}

# Extract all user data including names and certificate data
user_data=$(kubectl config view --raw -o json | jq -c '.users[]')

# Check each user's certificate
echo "$user_data" | while read -r user; do
    name=$(echo "$user" | jq -r '.name')
    cert=$(echo "$user" | jq -r '.user."client-certificate-data"')
    
    if [ "$cert" != "null" ] && [ -n "$cert" ]; then
        expiry_date=$(extract_cert "$cert")
        if [ -n "$expiry_date" ]; then
            days_left=$(days_until_expiry "$expiry_date")
            
            echo "User: $name"
            echo "Certificate expires on: $expiry_date"
            echo "Days until expiry: $days_left"
            echo "---"
        else
            echo "User: $name"
            echo "Failed to extract expiry date from certificate."
            echo "---"
        fi
    fi
done