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 error publicKey, 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.PublicKey derPkix, 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: %s\n", 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-----MIICXAIBAAKBgQCgPwlGJrWqTYaoMkI8jXkEI8ewQ7E57G2Fi91WTXMMK7X6GsT9VmnRcq++Rk/VS+4IPBlfWyVRg0NfQDyuKjed21fUPa9AIbpYWHgP/tojyeYC1+RaXncrt9kLp7nW4FZMJmzwU9hfxIB0nhDQqhJenjdBZuYZfkICfMqyqbVkAwIDAQABAoGAJRcSDXOuPrHdBhdD74ILTaL+eFTis3Z+zxdVbsFUbK+9WhtSFxUmPv1dohviJIuDl9JZSRHurFRGhsh2gxVwc7JXwWfD0DmD8dvdzr8q85Jml9YVZ7uhHFqSO4cYI7dlBOd7Uwjnc39E/d+1E/kWVNfKt7opPHgt02zOHLSxkbECQQDS7H3myu3oLOi0Slpd1MmmHVOo2cqJ1b3H6E8JtEjmHGswWTYvQNAe4yZ+Kffsp5LUYujedncPKvEj4G+iz44bAkEAwn4Bx30FKTri/tybgSnCWKwTGSX479829Xucrm5pYU/3D5/PeJQLRa4YSyg2/hU3ZBrue6CdzYJgGXNGEWhAOQJBALMlOB4A96X+FruidzRA2fBj8j10lakSSHl1H0RfwpbnRkcvTm0+AEZrqbL4lGGFRplrVNw2BBN25o8RPeArp0cCQEhukw0PI1fqhVUzJXqh6a4KT4aDHMWAlMAxi/VuSzKhjDo2Yxbd06DcqFF9JZXUou9WFFDYTUyW7GEuC/85mwkCQCOEjUQX0C3JCSr6fyZIjpEr+znyc9eFHyBp+533Ur4geFu2ewJ3ufJiUBmEj1rEQku8W7h9DS2rXl10IiSwUAA=-----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。如有错误或未考虑完全的地方，望不吝赐教。