因在做license注册机制当中，有对根据本地RSA pem密钥文件判断出RSA的公私密钥长度的需求（即：根据pem内容判断出RSA密钥是1024位或者2048位，或者其他位数等），因此个人通过思考，摸索整理出一个方法，予以记录，备用，分享。
package mainimport ('crypto/rsa''crypto/x509''encoding/pem''errors''fmt''io/ioutil''os')//全局变量var privateKey, publicKey []bytefunc init() {var err errorpublicKey, err = ioutil.ReadFile('public.pem')if err != nil {os.Exit(-1)}privateKey, err = ioutil.ReadFile('private.pem')if err != nil {os.Exit(-1)}}/** * @brief 获取RSA公钥长度 * @param[in] PubKey RSA公钥 * @return 成功返回 RSA公钥长度，失败返回error错误信息 */func GetPubKeyLen(PubKey []byte) (int, error) {if PubKey == nil {return 0, errors.New('input arguments error')}block, _ := pem.Decode(PubKey)if block == nil {return 0, errors.New('public rsaKey error')}pubInterface, err := x509.ParsePKIXPublicKey(block.Bytes)if err != nil {return 0, err}pub := pubInterface.(*rsa.PublicKey)return pub.N.BitLen(), nil}/** * @brief 获取RSA私钥长度 * @param[in] PriKey RSA私钥 * @return 成功返回 RSA私钥长度，失败返回error错误信息 */func GetPriKeyLen(PriKey []byte) (int, error) {if PriKey == nil {return 0, errors.New('input arguments error')}block, _ := pem.Decode(PriKey)if block == nil {return 0, errors.New('private rsaKey error!')}priv, err := x509.ParsePKCS1PrivateKey(block.Bytes)if err != nil {return 0, err}return priv.N.BitLen(), nil}func main() {//获取rsa 公钥长度PubKeyLen, _ := GetPubKeyLen(publicKey)fmt.Println('pbulic key len is ', PubKeyLen)//获取rsa 私钥长度PriKeyLen, _ := GetPriKeyLen(privateKey)fmt.Println('private key len is ', PriKeyLen)}
附录：以下程序是产生RSA公私密钥的程序，附件，方便测试。
package mainimport ( 'crypto/rand' 'crypto/rsa' 'crypto/x509' 'encoding/pem' 'flag' 'log' 'os')func main() { var bits int flag.IntVar(&bits, 'b', 1024, '密钥长度，默认为1024位') flag.Parse() if err := GenRsaKey(bits); err != nil { log.Fatal('密钥文件生成失败！') } log.Println('密钥文件生成成功！')}func GenRsaKey(bits int) error { // 生成私钥文件 privateKey, err := rsa.GenerateKey(rand.Reader, bits) if err != nil { return err } derStream := x509.MarshalPKCS1PrivateKey(privateKey) block := &pem.Block{ Type: '私钥', Bytes: derStream, } file, err := os.Create('private.pem') if err != nil { return err } err = pem.Encode(file, block) if err != nil { return err } // 生成公钥文件 publicKey := &privateKey.PublicKey derPkix, err := x509.MarshalPKIXPublicKey(publicKey) if err != nil { return err } block = &pem.Block{ Type: '公钥', Bytes: derPkix, } file, err = os.Create('public.pem') if err != nil { return err } err = pem.Encode(file, block) if err != nil { return err } return nil}
补充：golang 使用RSA生成公私钥，加密，解密，并使用SHA256进行签名，验证
话不多说直接上代码：
package mainimport ('crypto''crypto/rand''crypto/rsa''crypto/sha256''crypto/x509''encoding/hex''encoding/pem''errors''fmt')func main() {//rsa 密钥文件产生fmt.Println('-------------------------------获取RSA公私钥-----------------------------------------')prvKey, pubKey := GenRsaKey()fmt.Println(string(prvKey))fmt.Println(string(pubKey))fmt.Println('-------------------------------进行签名与验证操作-----------------------------------------')var data = '卧了个槽，这么神奇的吗？？！！！ ԅ(¯﹃¯ԅ) ！！！！！！）'fmt.Println('对消息进行签名操作...')signData := RsaSignWithSha256([]byte(data), prvKey)fmt.Println('消息的签名信息： ', hex.EncodeToString(signData))fmt.Println('n对签名信息进行验证...')if RsaVerySignWithSha256([]byte(data), signData, pubKey) {fmt.Println('签名信息验证成功，确定是正确私钥签名！！')}fmt.Println('-------------------------------进行加密解密操作-----------------------------------------')ciphertext := RsaEncrypt([]byte(data), pubKey)fmt.Println('公钥加密后的数据：', hex.EncodeToString(ciphertext))sourceData := RsaDecrypt(ciphertext, prvKey)fmt.Println('私钥解密后的数据：', string(sourceData))}//RSA公钥私钥产生func GenRsaKey() (prvkey, pubkey []byte) {// 生成私钥文件privateKey, err := rsa.GenerateKey(rand.Reader, 1024)if err != nil {panic(err)}derStream := x509.MarshalPKCS1PrivateKey(privateKey)block := &pem.Block{Type: 'RSA PRIVATE KEY',Bytes: derStream,}prvkey = pem.EncodeToMemory(block)publicKey := &privateKey.PublicKeyderPkix, err := x509.MarshalPKIXPublicKey(publicKey)if err != nil {panic(err)}block = &pem.Block{Type: 'PUBLIC KEY',Bytes: derPkix,}pubkey = pem.EncodeToMemory(block)return}//签名func RsaSignWithSha256(data []byte, keyBytes []byte) []byte {h := sha256.New()h.Write(data)hashed := h.Sum(nil)block, _ := pem.Decode(keyBytes)if block == nil {panic(errors.New('private key error'))}privateKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)if err != nil {fmt.Println('ParsePKCS8PrivateKey err', err)panic(err)}signature, err := rsa.SignPKCS1v15(rand.Reader, privateKey, crypto.SHA256, hashed)if err != nil {fmt.Printf('Error from signing: %sn', err)panic(err)}return signature}//验证func RsaVerySignWithSha256(data, signData, keyBytes []byte) bool {block, _ := pem.Decode(keyBytes)if block == nil {panic(errors.New('public key error'))}pubKey, err := x509.ParsePKIXPublicKey(block.Bytes)if err != nil {panic(err)}hashed := sha256.Sum256(data)err = rsa.VerifyPKCS1v15(pubKey.(*rsa.PublicKey), crypto.SHA256, hashed[:], signData)if err != nil {panic(err)}return true}// 公钥加密func RsaEncrypt(data, keyBytes []byte) []byte {//解密pem格式的公钥block, _ := pem.Decode(keyBytes)if block == nil {panic(errors.New('public key error'))}// 解析公钥pubInterface, err := x509.ParsePKIXPublicKey(block.Bytes)if err != nil {panic(err)}// 类型断言pub := pubInterface.(*rsa.PublicKey)//加密ciphertext, err := rsa.EncryptPKCS1v15(rand.Reader, pub, data)if err != nil {panic(err)}return ciphertext}// 私钥解密func RsaDecrypt(ciphertext, keyBytes []byte) []byte {//获取私钥block, _ := pem.Decode(keyBytes)if block == nil {panic(errors.New('private key error!'))}//解析PKCS1格式的私钥priv, err := x509.ParsePKCS1PrivateKey(block.Bytes)if err != nil {panic(err)}// 解密data, err := rsa.DecryptPKCS1v15(rand.Reader, priv, ciphertext)if err != nil {panic(err)}return data}
运行结果：
-------------------------------获取RSA公私钥----------------------------------------------BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY----------BEGIN PUBLIC KEY-----MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCgPwlGJrWqTYaoMkI8jXkEI8ewQ7E57G2Fi91WTXMMK7X6GsT9VmnRcq++Rk/VS+4IPBlfWyVRg0NfQDyuKjed21fUPa9AIbpYWHgP/tojyeYC1+RaXncrt9kLp7nW4FZMJmzwU9hfxIB0nhDQqhJenjdBZuYZfkICfMqyqbVkAwIDAQAB-----END PUBLIC KEY------------------------------------进行签名与验证操作-----------------------------------------对消息进行签名操作...消息的签名信息： 24a29efbc27e7b84c3b0eed683af28915381b2a0312f5383143cd2006b804d3a16c2b4750fb1857445b46664b795b6cefd402c5cf25e0f28116b7b50f5c16e80af9f9481def0161c6dac7a5d05c56595b891d84091e444ef4012ba1a0efd5cd2ff17c6dfdc109a2a3349ae2523217706a03042ea16d84fcf7d3dae37ee36d2e8对签名信息进行验证...签名信息验证成功，确定是正确私钥签名！！-------------------------------进行加密解密操作-----------------------------------------公钥加密后的数据： 2b34d46a62317f4f5e5c8618671831c0970cef2eeddc0d3aca02e1d5b411a067844e1250a1f69cbb1cbcb0cb1964af85836faa346f9ce9fac2710d4fa18e49ee1c4c73496183952fa95a54dd2d633b115504f0a365bac6d022399059a53f51c474e5e4f0f8eefde61bb85d5d812b67114f5d419c33496acaf11d3d84828733f7私钥解密后的数据： 卧了个槽，这么神奇的吗？？！！！ ԅ(¯﹃¯ԅ) ！！！！！！）
以上为个人经验，希望能给大家一个参考，也希望大家多多支持乐呵呵网。如有错误或未考虑完全的地方，望不吝赐教。
