feat(rsa): generate RSA if it doesnt exists

.gitignore

@@ -1,4 +1,5 @@
 build/
 id_rsa
+id_rsa.pub
 .DS_Store
 

cmd/vexd/main.go

@@ -70,6 +70,10 @@ func main() {
 		*httplistenaddr = "0.0.0.0:2000"
 	}
 
+	if _, err := os.Stat(*privatekeyfile); os.IsNotExist(err) {
+		vexserver.GenerateRSA()
+	}
+
 	config := &vexserver.Config{
 		Domain:         *domain,
 		PrivateKeyFile: *privatekeyfile,

server/rsa.go

@@ -0,0 +1,73 @@
+package vexserver
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/asn1"
+	"encoding/gob"
+	"encoding/pem"
+	"fmt"
+	"os"
+)
+
+func GenerateRSA() {
+	reader := rand.Reader
+	bitSize := 2048
+
+	key, err := rsa.GenerateKey(reader, bitSize)
+	checkError(err)
+
+	publicKey := key.PublicKey
+
+	savePEMKey("id_rsa", key)
+	savePublicPEMKey("id_rsa.pub", publicKey)
+}
+
+func saveGobKey(fileName string, key interface{}) {
+	outFile, err := os.Create(fileName)
+	checkError(err)
+	defer outFile.Close()
+
+	encoder := gob.NewEncoder(outFile)
+	err = encoder.Encode(key)
+	checkError(err)
+}
+
+func savePEMKey(fileName string, key *rsa.PrivateKey) {
+	outFile, err := os.Create(fileName)
+	checkError(err)
+	defer outFile.Close()
+
+	var privateKey = &pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(key),
+	}
+
+	err = pem.Encode(outFile, privateKey)
+	checkError(err)
+}
+
+func savePublicPEMKey(fileName string, pubkey rsa.PublicKey) {
+	asn1Bytes, err := asn1.Marshal(pubkey)
+	checkError(err)
+
+	var pemkey = &pem.Block{
+		Type:  "RSA PUBLIC KEY",
+		Bytes: asn1Bytes,
+	}
+
+	pemfile, err := os.Create(fileName)
+	checkError(err)
+	defer pemfile.Close()
+
+	err = pem.Encode(pemfile, pemkey)
+	checkError(err)
+}
+
+func checkError(err error) {
+	if err != nil {
+		fmt.Println("Fatal error ", err.Error())
+		os.Exit(1)
+	}
+}