生成OpenSSH兼容的密钥对代码

openssh_keygen.go

package main

import(
	"fmt"
	"io/ioutil"
	"bytes"
	"encoding/binary"
	"crypto/rsa"
	"crypto/rand"
	"crypto/x509"
	"encoding/base64"
	"encoding/pem"
	"math/big"
)

func main(){
	privateKey,err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		fmt.Printf("Error %s", err)
		return
	}

	derBytes := x509.MarshalPKCS1PrivateKey(privateKey)

	pemBlock := pem.Block{Bytes:derBytes,Type:"RSA PRIVATE KEY"}
	bytes := pem.EncodeToMemory(&pemBlock)
	//fmt.Printf("%s\n\n", string(bytes))

	ioutil.WriteFile("id_rsa", bytes, 0600)


	txt,err := EncodePublicKey(privateKey.PublicKey, "")
	if err != nil {
		fmt.Print("Invalid public key %s", err)
		return
	}
	txt += "\n"

	fmt.Printf("%s\n", txt)
	ioutil.WriteFile("id_rsa.pub", []byte(txt), 0644)
}

func EncodePublicKey(key interface{}, comment string) (string, error) {
	if rsaKey, ok := key.(rsa.PublicKey); ok {
		key_type := "ssh-rsa"

		modulus_bytes := rsaKey.N.Bytes()


		intLen := binary.Size(int32(rsaKey.E))
		needLen := (big.NewInt(int64(rsaKey.E)).BitLen() + 7) / 8

		eBuf := make([]byte, intLen)
		binary.BigEndian.PutUint32(eBuf, uint32(rsaKey.E))

		eBuf  = eBuf[intLen-needLen:]
		fmt.Println(eBuf)


		var data = []interface{} {
			uint32(len(key_type)),
			[]byte(key_type),
			uint32(needLen), //size of rsaKey.E
			eBuf,
			uint32(len(modulus_bytes)+1),//size of modulus_bytes
			byte(0),//padding
			modulus_bytes,
		}

		buf := new(bytes.Buffer)
		for _, v := range data {
			err := binary.Write(buf, binary.BigEndian, v)
			if err != nil { return "", err }
		}

		if comment!="" {
			comment = " " + comment
		}
		return fmt.Sprintf("%s %s"+comment, key_type, base64.StdEncoding.EncodeToString(buf.Bytes())), nil
	}

	return "", fmt.Errorf("Unknown key type: %T\n", key)
}