Go Fake Certificate test generation

certgen.go

package certgen

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"io/ioutil"
	"math/big"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
)

// generateFakeTLSCertificate this function generates a certificate and a
// private key and stores them in temp files, returning the paths of both files.
// These paths can be passed directly to the tls.LoadX509KeyPair function.
func genereateFakeTLSCertificate(t *testing.T) (string, string) {
	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	assert.NoError(t, err)

	asn1Bytes, err := x509.MarshalECPrivateKey(priv)
	assert.NoError(t, err)
	privBytes := pem.EncodeToMemory(&pem.Block{
		Type:  "EC PRIVATE KEY",
		Bytes: asn1Bytes,
	})

	serialNumber, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	assert.NoError(t, err)
	template := x509.Certificate{
		SerialNumber: serialNumber,
		Subject: pkix.Name{
			Organization: []string{"ACME"},
		},
		NotBefore:             time.Now(),
		NotAfter:              time.Now().Add(365 * 24 * time.Hour),
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
	}

	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, priv.Public(), priv)
	assert.NoError(t, err)
	certBytes := pem.EncodeToMemory(&pem.Block{
		Type:  "CERTIFICATE",
		Bytes: derBytes,
	})

	privFile, err := ioutil.TempFile("", "priv")
	assert.NoError(t, err)
	certFile, err := ioutil.TempFile("", "cert")
	assert.NoError(t, err)

	err = ioutil.WriteFile(privFile.Name(), privBytes, 0644)
	assert.NoError(t, err)

	err = ioutil.WriteFile(certFile.Name(), certBytes, 0644)
	assert.NoError(t, err)

	return certFile.Name(), privFile.Name()
}