Generate certificates with arbitrary validity

gen.sh

#!/usr/bin/bash

# Usage:
# gen.sh <STARTDATE> <ENDDATE>
# the dates are in YYYYMMDDhhmmssZ format and are UTC timestamps

# Example:
# gen.sh 20250609000000Z 20250630000000Z

STARTDATE="${1:-20250101000000Z}"
ENDDATE="${2:-20250101000000Z}"

# Generate private key
openssl genrsa -out server.key 2048

# Generate CSR with specific hostname
openssl req -new -key server.key -out server.csr -subj "/CN=your-hostname.example.com"

# Generate self-signed certificate with specific expiry
openssl x509 -req \
    -not_before "${STARTDATE}" \
    -not_after "${ENDDATE}" \
    -in server.csr \
    -signkey server.key \
    -out server.crt \
    -extensions v3_req \
    -extfile <(printf "[v3_req]\nsubjectAltName=DNS:your-hostname.example.com")