错误：无法将参数'1'的'std :: string'转换为'X509 *'到'EVP_PKEY * X509_get_pubkey（X509 *）'

Question

I want to verify if the certificate is valid in its format, so i wrote this code but it seems that there is an error

if (validConfigFile()) {    
    INIReader reader(CONFIG_FILE);
    string certFile= reader.Get("Server", "cert-file", "None");
    if (certFile == "None") {
        syslog(LOG_ERR, "cert-file in configuration file is not properly adjusted");
        exit(EXIT_FAILURE); }
    else {
        std::string fileName(certFile);
        ifstream fin(fileName.c_str());
        if(fin.fail()) {
            syslog(LOG_ERR, "cert-file not found in its file path");
            exit(EXIT_FAILURE); }
        else {
            OpenSSL_add_all_digests();
            SSL_CTX *sslctx = SSL_CTX_new(SSLv23_server_method());
            SSL_CTX_use_certificate_file(sslctx, certFile, SSL_FILETYPE_PEM);
            SSL *ssl = SSL_new(sslctx);
            X509 *CERT = SSL_get_certificate(ssl);
            if (X509_verify(CERT,X509_get_pubkey(CERT)) == -1) {
                syslog(LOG_ERR, "cert-file not valid");
                exit(EXIT_FAILURE); }
        }
    }
}

when compiling i get this error

/main.cpp:68: error: cannot convert ‘std::string’ to ‘const char*’ for argument ‘2’ to ‘int SSL_CTX_use_certificate_file(SSL_CTX*, const char*, int)’

and also

main.cpp:70: error: expected unqualified-id before ‘char’ for that line  : X509 *CERT = SSL_get_certificate(ssl);

Answer 1

std :: string没有隐式转换为char *（C风格的字符串），因此请使用方法c_str()代替：

SSL_CTX_use_certificate_file(sslctx, certFile.c_str(), SSL_FILETYPE_PEM);

Answer 2

Change

SSL_CTX_use_certificate_file(sslctx, certFile, SSL_FILETYPE_PEM);

into

SSL_CTX_use_certificate_file(sslctx, certFile.c_str(), SSL_FILETYPE_PEM);

Answer 3

Try using c_str()

  SSL_CTX_use_certificate_file(sslctx, certFile.c_str(), SSL_FILETYPE_PEM);
                                                ^
                                                ^

instead to get a char* from the string