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消息加密使用公钥：BER 解码错误

来源：stackoverflow 2024-03-06 17:09:27 0浏览收藏

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问题内容

我在使用公钥加密消息时遇到问题。我想使用字符串中包含的公钥 rsa-4096 加密一个字符串（让我们说 "test"）。让我们说：

-----开始公钥----- miicijanbgkqhkig9w0baqefaaocag8amiiccgkcageam9ggfej3dhazihcvhtna vnu38kbdxvioswyxcjewq8yhlqol6e5he1dxx5uqvnklr7+gamzzbxeqlocrsyi6 nrexgxe4wftjd+pqlh5ba9dio8vbspisg66zymfdztmfgn2dl0euvuiijguqwkja e5p8ebjsnodomx1763p8k50ahhizaubd+iwavdezbew7efopt5wj6c5a1kwkv4bx +viqoc7mfnjqzii+sg/8yjnt++zv5fo+jwe6pyxwzcabwgsbyq9cv2imc4zxafvo glytixok/7rmy6nie+miuafrevbgg8k0yt3u1jn1knqyv++qtnaqqmcvtogc1se6 s8pwihgrgh+zg3ewudzvqjadbdl/cgdz8wnfps8ssant1kcjyq3ogp12fx0axenf vklcm5jlcm1v6/kyqpyk0fvarh6rt7e5qzcwzxaoxmz1bze97cz9+pqgbglyyrqo cqbewkvuei/neboqdifrgok/ku43lmurxbtbybseoxvn4d+3jgn0bs1cmxqsljml kupv87oljzzggqw8lrs3owkqf9trs9fyljujst3f2osyaphedyx9xdkjnhgbh+af 47kocpxg6olpotram5cw/0zwsgtvhxfbldo+xfnzddsklwfyl2jx8wifz6txa/mp /aloyzkx/wadqaeqlhbs3smcaweaaq== -----结束公钥-----

为此，我尝试使用 c++ 中的 cryptopp 库 (https://www.cryptopp.com/wiki/keys_and_formats)，但是当我尝试读取和解码我的公钥时，出现以下错误： ber 解码错误 。这是我正在使用的完整源代码：

#include 
#include  
#include 
#include 
#include 

#include 
using cryptopp::bytequeue;

#include 
using cryptopp::redirector;

#include 
using cryptopp::filesource;
using cryptopp::filesink;

#include 
using cryptopp::privatekey;
using cryptopp::publickey;
using cryptopp::bufferedtransformation;

#include 
#include 
using cryptopp::rsa;

#include 
using cryptopp::base64encoder;
using cryptopp::base64decoder;

#include 
using cryptopp::autoseededrandompool;

using namespace std;

int main(int argc, char** argv) {

    bytequeue queue;

    string rsa_public_key ="-----begin public key-----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-----end public key-----";
    static string header = "-----begin public key-----";
    static string footer = "-----end public key-----";

    size_t pos1 = rsa_public_key.find(header);
    if(pos1 == string::npos) throw runtime_error("pem header not found");

    size_t pos2 = rsa_public_key.find(footer, pos1+1);
    if(pos2 == string::npos) throw runtime_error("pem footer not found");

    // start position and length
    pos1 = pos1 + header.length();
    pos2 = pos2 - pos1;

    string keystr = rsa_public_key.substr(pos1, pos2);    
    /*base64encoder decoder;
    decoder.attach(new redirector(queue));*/
    queue.put((const byte*)keystr.data(), keystr.length());
    queue.messageend();

    cout << keystr << endl;

    try {

        rsa::publickey public_key;
        public_key.berdecodepublickey(queue, false /*paramspresent*/, queue.maxretrievable());

        if(queue.isempty()) {
            cerr << "the queue is empty...";
        }

        autoseededrandompool prng;
        bool valid = public_key.validate(prng, 3);
        if(!valid) cerr << "rsa public key is not valid" << endl;

        cout << "n:" << public_key.getmodulus() << endl;
        cout << "e:" << public_key.getpublicexponent() << endl;

    } catch (exception& e) {

        printf( "caught exception: %s\n", e.what() );
        exit (1);
    } 
}

非常感谢那些可以帮助我理解为什么公钥没有被正确读取的人。对于那些说 golang 的人来说，我基本上是在尝试重现以下功能：

func WriteEncryptedWithPublicKeyInformation(filename string, information string, publicKey string) error {

    f, err := os.Create(filename)

    block, _ := pem.Decode([]byte(publicKey))
    if block == nil {
        return errors.New("Failed to parse PEM block containing the public key")
    }

    pub, err := x509.ParsePKIXPublicKey(block.Bytes)
    if err != nil {
        return errors.New("Failed to parse DER encoded public key: " + err.Error())
    }

    key := pub.(*(rsa.PublicKey))
    ciphertext, err := rsa.EncryptOAEP(sha256.New(), rand.Reader, key, []byte(information), nil)
    if err != nil {
        return err
    }

    _, err = f.WriteString(b64.StdEncoding.EncodeToString(ciphertext))
    if err != nil {
        return err

    }
    f.Close()
    return nil
}

其中 filename 是我的输出文件，information 是我要加密的字符串，publickey 是包含公钥的字符串。

解决方案

您的程序解码 base64 的方式不正确，函数 rsafunction::berdecodepublickey 根据参考

berdecodepublickey() 解码 subjectpublickeyinfo 的 subjectpublickey 部分，不带 bit string 标头。

您应该使用 x509publickey::berdecode 函数，因为类 rsa::publickey 继承自 x509publickey

尝试一下这个程序，它应该可以工作。

#include 
#include 
#include 
#include 
#include 


#include 
using CryptoPP::ByteQueue;

#include 
using CryptoPP::Redirector;

#include 
using CryptoPP::FileSource;
using CryptoPP::FileSink;

#include 
using CryptoPP::PrivateKey;
using CryptoPP::PublicKey;
using CryptoPP::BufferedTransformation;

#include 
#include 
#include 

using CryptoPP::RSA;

#include 
using CryptoPP::Base64Encoder;
using CryptoPP::Base64Decoder;

#include 
using CryptoPP::AutoSeededRandomPool;

using namespace std;

int main() {

    ByteQueue queue;

    string RSA_PUBLIC_KEY ="-----BEGIN PUBLIC KEY-----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-----END PUBLIC KEY-----";
    static string HEADER = "-----BEGIN PUBLIC KEY-----";
    static string FOOTER = "-----END PUBLIC KEY-----";

    size_t pos1 = RSA_PUBLIC_KEY.find(HEADER);
    if(pos1 == string::npos) throw runtime_error("PEM header not found");

    size_t pos2 = RSA_PUBLIC_KEY.find(FOOTER, pos1+1);
    if(pos2 == string::npos) throw runtime_error("PEM footer not found");

    // Start position and length
    pos1 = pos1 + HEADER.length();
    pos2 = pos2 - pos1;

    string keystr = RSA_PUBLIC_KEY.substr(pos1, pos2);

    CryptoPP::StringSource ss{keystr.c_str(), true};

    Base64Decoder decoder;
    decoder.Attach(new Redirector(queue));
    ss.TransferTo(decoder);
    decoder.MessageEnd();

    cout << keystr << endl;

    try {

        RSA::PublicKey public_key;

        if(queue.IsEmpty()) {
            cerr << "The queue is empty...";
        }

        public_key.BERDecode(queue);

        AutoSeededRandomPool prng;
        bool valid = public_key.Validate(prng, 3);
        if(!valid) cerr << "RSA public key is not valid" << endl;

        cout << "N:" << public_key.GetModulus() << endl;
        cout << "E:" << public_key.GetPublicExponent() << endl;

    } catch (exception& e) {

        printf( "Caught exception: %s\n", e.what() );
        exit (1);
    }
}

我没有看到你解码中间的base 64。 ber 是二进制格式，您首先必须转换为二进制才能读取它。

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