source: code/trunk/certfp.go@ 729

package soju

import (
        "crypto"
        "crypto/ecdsa"
        "crypto/ed25519"
        "crypto/elliptic"
        "crypto/rand"
        "crypto/rsa"
        "crypto/x509"
        "crypto/x509/pkix"
        "math/big"
        "time"
)

func generateCertFP(keyType string, bits int) (privKeyBytes, certBytes []byte, err error) {
        var (
                privKey crypto.PrivateKey
                pubKey  crypto.PublicKey
        )
        switch keyType {
        case "rsa":
                key, err := rsa.GenerateKey(rand.Reader, bits)
                if err != nil {
                        return nil, nil, err
                }
                privKey = key
                pubKey = key.Public()
        case "ecdsa":
                key, err := ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
                if err != nil {
                        return nil, nil, err
                }
                privKey = key
                pubKey = key.Public()
        case "ed25519":
                var err error
                pubKey, privKey, err = ed25519.GenerateKey(rand.Reader)
                if err != nil {
                        return nil, nil, err
                }
        }

        // Using PKCS#8 allows easier extension for new key types.
        privKeyBytes, err = x509.MarshalPKCS8PrivateKey(privKey)
        if err != nil {
                return nil, nil, err
        }

        notBefore := time.Now()
        // Lets make a fair assumption nobody will use the same cert for more than 20 years...
        notAfter := notBefore.Add(24 * time.Hour * 365 * 20)
        serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
        serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
        if err != nil {
                return nil, nil, err
        }
        cert := &x509.Certificate{
                SerialNumber: serialNumber,
                Subject:      pkix.Name{CommonName: "soju auto-generated certificate"},
                NotBefore:    notBefore,
                NotAfter:     notAfter,
                KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
                ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
        }
        certBytes, err = x509.CreateCertificate(rand.Reader, cert, cert, pubKey, privKey)
        if err != nil {
                return nil, nil, err
        }

        return privKeyBytes, certBytes, nil
}