c++ - 当响应跨数据包拆分但 SSL_pending 为零且 SSL_get_error 返回 SSL_ERROR_NONE 时，如何查找是否有更多数据要读取

Question

我们有一个用 C++ 编码的客户端应用程序，它使用 openssl 通过 SSL 连接到 Java 应用程序服务器。我们使用非阻塞套接字连接模式，可以选择“选择”或“轮询”机制来识别可供读取的数据包。

客户端已经正常工作了很长一段时间，但最近我们注意到一个问题，即响应被拆分成多个数据包，并且 SSL_read 仅返回一个字符“H”，SSL_ERROR_NONE 和 SSL_pending 为零，因此我们的 SSL_read 循环以不完整的响应结束。在随后重新调用 SSL_read [作为 hack] 时，我们得到以“TTP 1.1”开头的剩余响应。

由于 SSL_pending=0 和 SSL_get_error()=SSL_ERROR_NONE，我们没有找到任何其他方法来知道是否有更多数据要读取并因此结束只读取一个字符的“SSL_read”循环。

Here is the relevant pseudo code... 

bool done=false;
int pending=1; bool inited=false;
bool want_read=false; bool want_write=false;
timeval tv;
String response; //internal class for string, legacy            
while(!done) {
if( !inited || want_read || want_write ) {
    try {
        /* Wait a few seconds. */
        if(!inited) {
            tv.tv_sec = timeOutValue.tv_sec;
            tv.tv_usec = timeOutValue.tv_usec;
        } else {
            tv.tv_sec = 0;
            tv.tv_usec = 500000; //hack to reduce the waiting period
        } 
                    #ifdef USE_POLL
            poll the socket
        #else
            call 'select' on the socket
        #endif
        inited=true;
        continue;
    } catch(const XSeption&) {
        close_socket(&sock);
        done=true;
        cout << "Error waiting on select/poll call" << endl;
        break;
    }
}

memset(temp, 0, BUFSIZE);
charsRead = SSL_read(ssl,temp, (sizeof(char)*BUFSIZE));
cout << endl << "charsRead = " << charsRead << endl;    

if(charsRead>0) {
    response.append(temp, charsRead);
}
cout << "Response : " << response << endl;

int sslerror = SSL_get_error(ssl,charsRead);
cout << "SSL_error_code = " << sslerror << endl;

pending=SSL_pending(ssl);
cout << "pending characters in the current SSL buffer : " << endl;

/*
if(charsRead==1) {
    memset(temp, 0, BUFSIZE);
    cout << "read only one character which is odd,hence reading again" << endl;
    charsRead = SSL_read(ssl,temp, (sizeof(char)*BUFSIZE));
    cout << endl << "charsRead in second read = " << charsRead << endl;
    if(charsRead>0) {
        response.append(temp, charsRead);
    }
    cout << "Second Response : " << response << endl;

    sslerror = SSL_get_error(ssl,charsRead);
    cout << "SSL_error_code = " << sslerror << endl;

    pending=SSL_pending(ssl);
    cout << "pending characters in the current SSL buffer : " << endl;
}
*/

switch(sslerror){

    case SSL_ERROR_NONE:
        cout << "No SSL Error" << endl;
        done=true; //ideally, we should mark the process completed here; but if mark this completed here, then we are getting only 1 character 'H'
        break;
    case SSL_ERROR_WANT_READ:
        cout << "In SSL_ERROR_WANT_READ" << endl;
        //SSLread Still pending
        want_read=true;
        //continue;
        break;

    case SSL_ERROR_WANT_WRITE:
        cout << "In SSL_ERROR_WANT_WRITE" << endl;
        //SSLread Still pending
        want_write=true;
        //continue;
        break;

    case SSL_ERROR_SSL:
        done=true;
        cout << "encountered SSL INTERNAL ERROR" << endl;
        close_socket(&sock);
        break;

    case SSL_ERROR_SYSCALL:
        done=true;
        cout << "encountered ERROR SYSCALL" << endl;
        close_socket(&sock);
        break;

    case SSL_ERROR_ZERO_RETURN:
        done=true;
        cout << "encountered SSL ZERO RETURN" << endl;
        close_socket(&sock);
        break;

    default:
        done=true;
        cout << "encountered default error" << endl;
        close_socket(&sock);
        break;
    } //end of switch  
} //end of while  

cout << "Final Response : " << response << endl;  

那么，当 SSL_pending 返回零且 SSL_get_error 为 SSL_ERROR_NONE 并且我不知道响应可以有多长[字节数/字符数时，我如何确定响应是完整的还是待定的？

我的期望错了吗？为什么 SSL_read 第一次返回单个字符，即使我们提供了更大的缓冲区？

非常感谢在这方面的任何帮助...

更新:

while(!done) {
currentTime = getTime();
tval.tv_sec = timeOutValue.tv_sec - (currentTime - beginTime);
tval.tv_usec = timeOutValue.tv_usec;
if ( tval.tv_sec <= 0 ) //the allotted time for processing this request has elapsed
{
    //do not close the socket or SSL session since this is just a timeout issue
    throw Exception::TIMEOUT);
}

#ifdef USE_POLL
    fds.fd = sock;
    fds.events = POLLIN;
#else
    FD_ZERO(&rset);
    FD_SET(sock, &rset);
#endif

if(!inited || want_read || want_write) {
    timeval tv;
    /*
    When we first enter this method or for NON-SSL requests, we would wait till the SELECT call returns a ready file-descriptor but in the case of a SSL requests processing the response message , we just issue SELECT with 0(zero) or very little timeout since SSL_read is giving us a common error code for actual need to check at the socket (SELECT/POLL) and the need to call SSL_read again, if we can find a way to differentiate the need to call SELECT/POLL Vs invoke SSL_read, then this if-else construct needs to be removed and we can then use the complete remaining time for timeout parameter in SELECT/POLL call even for SSL requests
    */
    if(!inited ) {
        tv.tv_sec=tval.tv_sec;
        tv.tv_usec=tval.tv_usec;
    } else {
        tv.tv_sec=0;
        tv.tv_usec=1000;
    }
    try {
        #ifdef USE_POLL
            poll_call(&fds, 1, &tv);
        #else
            select_call(sock+1, &rset, NULL, NULL, &tv);
        #endif
    } catch(const Exception&) {
        /*
        do not close the socket or throw exception; the socket will be closed only if an error occurs or if the server itself the closed the connection
        */
    }
    inited=true;
    want_read=false;
    want_write=false;
}

memset(temp, 0, BUFSIZE);

charsRead = openSSL->SSLread(temp, (sizeof(char)*BUFSIZE));
if(charsRead>0) {
    response.append(temp, charsRead);
    done=is_response_complete(response);
} else {
    int sslerror=openSSL->SSLgetErrorCode(charsRead);
    switch(sslerror){

        case SSL_ERROR_NONE:
            break;

        case SSL_ERROR_WANT_READ:
            want_read=true;
            break;

        case SSL_ERROR_WANT_WRITE:
            want_write=true;
            break;

        case SSL_ERROR_SSL:
            close(openSSL, Exception::SSL_CONNECTION_PROBLEM, 
                    ErrorDescription(sslerror));
            break;

        case SSL_ERROR_SYSCALL:
            close(openSSL,Exception::SERVER_CONNECTION_PROBLEM,
                    ErrorDescription(sslerror));
            break;

        case SSL_ERROR_ZERO_RETURN:
        default:
            close(openSSL,Exception::SSL_CONNECTION_PROBLEM,
                        ErrorDescription(sslerror));
            break;
    } //end of switch
} //end off ssl_error check
}

Answer 1

我也看到了这种行为。处理它的正确方法是您的应用程序应该随时期望任何数量的数据......它是数据的“流”，而不是打包的请求/响应。识别“完整请求/响应”的唯一方法是在应用程序级别对其进行解析。如果您没有完整的数据，请将其缓冲并等待更多数据。传输机制不能也不会告诉您……它只是在说“嘿，我有数据”。