c++ 使用 openssl API RSA 加密文件

来源： chatGPT

#include <iostream>
#include <fstream>
#include <openssl/rsa.h>
#include <openssl/pem.h>

bool encryptFile(const char* inputFile, const char* outputFile, RSA* rsaPublicKey) {
    FILE* in = fopen(inputFile, "rb");
    if (!in) {
        std::cerr << "Failed to open input file." << std::endl;
        return false;
    }

    FILE* out = fopen(outputFile, "wb");
    if (!out) {
        std::cerr << "Failed to open output file." << std::endl;
        fclose(in);
        return false;
    }

    const int RSA_KEY_LENGTH = RSA_size(rsaPublicKey);
    const int ENCRYPTED_BLOCK_SIZE = RSA_KEY_LENGTH - 42;
    const int DECRYPTED_BLOCK_SIZE = RSA_KEY_LENGTH;

    unsigned char decryptedData[DECRYPTED_BLOCK_SIZE];
    unsigned char encryptedData[ENCRYPTED_BLOCK_SIZE];

    int bytesRead;
    while ((bytesRead = fread(decryptedData, sizeof(unsigned char), DECRYPTED_BLOCK_SIZE, in)) > 0) {
        int encryptedSize = RSA_public_encrypt(bytesRead, decryptedData, encryptedData, rsaPublicKey, RSA_PKCS1_PADDING);
        if (encryptedSize == -1) {
            std::cerr << "Failed to encrypt data." << std::endl;
            fclose(in);
            fclose(out);
            return false;
        }
        fwrite(encryptedData, sizeof(unsigned char), encryptedSize, out);
    }

    fclose(in);
    fclose(out);
    return true;
}

bool decryptFile(const char* inputFile, const char* outputFile, RSA* rsaPrivateKey) {
    FILE* in = fopen(inputFile, "rb");
    if (!in) {
        std::cerr << "Failed to open input file." << std::endl;
        return false;
    }

    FILE* out = fopen(outputFile, "wb");
    if (!out) {
        std::cerr << "Failed to open output file." << std::endl;
        fclose(in);
        return false;
    }

    const int RSA_KEY_LENGTH = RSA_size(rsaPrivateKey);
    const int ENCRYPTED_BLOCK_SIZE = RSA_KEY_LENGTH;
    const int DECRYPTED_BLOCK_SIZE = RSA_KEY_LENGTH - 42;

    unsigned char decryptedData[DECRYPTED_BLOCK_SIZE];
    unsigned char encryptedData[ENCRYPTED_BLOCK_SIZE];

    int bytesRead;
    while ((bytesRead = fread(encryptedData, sizeof(unsigned char), ENCRYPTED_BLOCK_SIZE, in)) > 0) {
        int decryptedSize = RSA_private_decrypt(bytesRead, encryptedData, decryptedData, rsaPrivateKey, RSA_PKCS1_PADDING);
        if (decryptedSize == -1) {
            std::cerr << "Failed to decrypt data." << std::endl;
            fclose(in);
            fclose(out);
            return false;
        }
        fwrite(decryptedData, sizeof(unsigned char), decryptedSize, out);
    }

    fclose(in);
    fclose(out);
    return true;
}

int main() {
    const char* publicKeyFile = "public_key.pem";
    const char* privateKeyFile = "private_key.pem";
    const char* inputFile = "input.txt";
    const char* encryptedFile = "encrypted.bin";
    const char* decryptedFile = "decrypted.txt";

    // 读取公钥
    FILE* publicKeyFP = fopen(publicKeyFile, "rb");
    if (!publicKeyFP) {
        std::cerr << "Failed to open public key file." << std::endl;
        return 1;
    }
    RSA* rsaPublicKey = PEM_read_RSA_PUBKEY(publicKeyFP, nullptr, nullptr, nullptr);
    fclose(publicKeyFP);
    if (!rsaPublicKey) {
        std::cerr << "Failed to load public key." << std::endl;
        return 1;
    }

    // 读取私钥
    FILE* privateKeyFP = fopen(privateKeyFile, "rb");
    if (!privateKeyFP) {
        std::cerr << "Failed to open private key file." << std::endl;
        RSA_free(rsaPublicKey);
        return 1;
    }
    RSA* rsaPrivateKey = PEM_read_RSAPrivateKey(privateKeyFP, nullptr, nullptr, nullptr);
    fclose(privateKeyFP);
    if (!rsaPrivateKey) {
        std::cerr << "Failed to load private key." << std::endl;
        RSA_free(rsaPublicKey);
        return 1;
    }

    // 加密文件
    if (encryptFile(inputFile, encryptedFile, rsaPublicKey)) {
        std::cout << "File encrypted successfully." << std::endl;
    } else {
        std::cerr << "Failed to encrypt file." << std::endl;
    }

    // 解密文件
    if (decryptFile(encryptedFile, decryptedFile, rsaPrivateKey)) {
        std::cout << "File decrypted successfully." << std::endl;
    } else {
        std::cerr << "Failed to decrypt file." << std::endl;
    }

    // 释放内存
    RSA_free(rsaPublicKey);
    RSA_free(rsaPrivateKey);

    return 0;
}

编译

g++ -o rsa_example rsa_example.cpp -lssl -lcrypto