Create TLS certs (mostly for unit tests)

tls_certs.go

package some_test

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"fmt"
	"math/big"
	"time"
)

func composeCerts() ([]byte, []byte, []byte, error) {
	// Create a CA certificate
	caTemplate := x509.Certificate{
		SerialNumber:          big.NewInt(1),
		Subject:               pkix.Name{CommonName: "CA"},
		NotBefore:             time.Now(),
		NotAfter:              time.Now().AddDate(1, 0, 0),
		KeyUsage:              x509.KeyUsageCertSign,
		BasicConstraintsValid: true,
	}
	caKey, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
	if err != nil {
		return nil, nil, nil, err
	}
	caCertDER, err := x509.CreateCertificate(rand.Reader, &caTemplate, &caTemplate, &caKey.PublicKey, caKey)
	if err != nil {
		return nil, nil, nil, err
	}

	ca := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: caCertDER})

	// Create a user certificate
	userTemplate := x509.Certificate{
		SerialNumber: big.NewInt(2),
		Subject:      pkix.Name{CommonName: "User"},
		NotBefore:    time.Now(),
		NotAfter:     time.Now().AddDate(1, 0, 0), // Valid for 1 year
		KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
	}
	userKey, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
	if err != nil {
		return nil, nil, nil, err
	}
	userCertDER, err := x509.CreateCertificate(rand.Reader, &userTemplate, &caTemplate, &userKey.PublicKey, caKey)
	if err != nil {
		return nil, nil, nil, err
	}

	user := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: userCertDER})

	// Write user private key to file
	privBytes, err := x509.MarshalECPrivateKey(userKey)
	if err != nil {
		fmt.Println("Error marshaling user private key:", err)
		return nil, nil, nil, err
	}
	key := pem.EncodeToMemory(&pem.Block{Type: "EC PRIVATE KEY", Bytes: privBytes})
	return ca, user, key, err
}