Implement creation of CACert

go-workspace/src/nebula/nebula.go

@@ -4,6 +4,7 @@ package nebula
 
 import (
 	crypticnet "cryptic-net"
+	"crypto/ed25519"
 	"crypto/rand"
 	"fmt"
 	"io"
@@ -32,6 +33,13 @@ type HostCert struct {
 	HostCert []byte
 }
 
+// CACert contains the certificate and private files which can be used to create
+// HostCerts. Each file is PEM encoded.
+type CACert struct {
+	CACert []byte
+	CAKey  []byte
+}
+
 // NewHostCert generates a new key/cert for a nebula host using the CA key
 // which will be found in the adminFS.
 func NewHostCert(
@@ -123,3 +131,42 @@ func NewHostCert(
 		HostCert: hostCrtPEM,
 	}, nil
 }
+
+// NewCACert generates a CACert. The domain should be the network's root domain,
+// and is included in the signing certificate's Name field.
+func NewCACert(domain string) (CACert, error) {
+
+	pubKey, privKey, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		panic(fmt.Errorf("generating ed25519 key: %w", err))
+	}
+
+	now := time.Now()
+	expireAt := now.Add(2 * 365 * 24 * time.Hour)
+
+	caCrt := cert.NebulaCertificate{
+		Details: cert.NebulaCertificateDetails{
+			Name:      fmt.Sprintf("%s cryptic-net root cert", domain),
+			NotBefore: now,
+			NotAfter:  expireAt,
+			PublicKey: pubKey,
+			IsCA:      true,
+		},
+	}
+
+	if err := caCrt.Sign(privKey); err != nil {
+		return CACert{}, fmt.Errorf("signing caCrt: %w", err)
+	}
+
+	caKeyPEM := cert.MarshalEd25519PrivateKey(privKey)
+
+	caCrtPem, err := caCrt.MarshalToPEM()
+	if err != nil {
+		return CACert{}, fmt.Errorf("marshaling caCrt: %w", err)
+	}
+
+	return CACert{
+		CACert: caCrtPem,
+		CAKey:  caKeyPEM,
+	}, nil
+}