c++ 使用 openssl api 读取 pem x.509 文件

来源： chatGPT

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

std::string readPEMFile(const std::string& filePath) {
    std::string pemContent;

    // 打开 PEM 文件
    FILE* file = fopen(filePath.c_str(), "r");
    if (!file) {
        std::cerr << "Failed to open PEM file: " << filePath << std::endl;
        return pemContent;
    }

    // 读取 PEM 文件内容
    EVP_PKEY* pkey = PEM_read_PrivateKey(file, nullptr, nullptr, nullptr);
    if (!pkey) {
        std::cerr << "Failed to read PEM file: " << filePath << std::endl;
        fclose(file);
        return pemContent;
    }

    // 将 PEM 文件内容转换为字符串
    BIO* bio = BIO_new(BIO_s_mem());
    if (!bio) {
        std::cerr << "Failed to create BIO." << std::endl;
        fclose(file);
        EVP_PKEY_free(pkey);
        return pemContent;
    }

    if (PEM_write_bio_PrivateKey(bio, pkey, nullptr, nullptr, 0, nullptr, nullptr) != 1) {
        std::cerr << "Failed to write PEM to BIO." << std::endl;
        fclose(file);
        EVP_PKEY_free(pkey);
        BIO_free_all(bio);
        return pemContent;
    }

    char* buffer;
    long length = BIO_get_mem_data(bio, &buffer);
    pemContent.assign(buffer, length);

    // 清理资源
    fclose(file);
    EVP_PKEY_free(pkey);
    BIO_free_all(bio);

    return pemContent;
}

int main() {
    std::string pemFilePath = "path/to/pem/file.pem";
    std::string pemContent = readPEMFile(pemFilePath);
    if (!pemContent.empty()) {
        std::cout << "PEM content:\n" << pemContent << std::endl;
    } else {
        std::cerr << "Failed to read PEM file." << std::endl;
    }

    return 0;
}

编译：

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