Logo Search packages:      
Sourcecode: nmap version File versions  Download package

ncat_proxy.c

/***************************************************************************
 * ncat_proxy.c -- HTTP proxy server.                                      *
 ***********************IMPORTANT NMAP LICENSE TERMS************************
 *                                                                         *
 * The Nmap Security Scanner is (C) 1996-2009 Insecure.Com LLC. Nmap is    *
 * also a registered trademark of Insecure.Com LLC.  This program is free  *
 * software; you may redistribute and/or modify it under the terms of the  *
 * GNU General Public License as published by the Free Software            *
 * Foundation; Version 2 with the clarifications and exceptions described  *
 * below.  This guarantees your right to use, modify, and redistribute     *
 * this software under certain conditions.  If you wish to embed Nmap      *
 * technology into proprietary software, we sell alternative licenses      *
 * (contact sales@insecure.com).  Dozens of software vendors already       *
 * license Nmap technology such as host discovery, port scanning, OS       *
 * detection, and version detection.                                       *
 *                                                                         *
 * Note that the GPL places important restrictions on "derived works", yet *
 * it does not provide a detailed definition of that term.  To avoid       *
 * misunderstandings, we consider an application to constitute a           *
 * "derivative work" for the purpose of this license if it does any of the *
 * following:                                                              *
 * o Integrates source code from Nmap                                      *
 * o Reads or includes Nmap copyrighted data files, such as                *
 *   nmap-os-db or nmap-service-probes.                                    *
 * o Executes Nmap and parses the results (as opposed to typical shell or  *
 *   execution-menu apps, which simply display raw Nmap output and so are  *
 *   not derivative works.)                                                * 
 * o Integrates/includes/aggregates Nmap into a proprietary executable     *
 *   installer, such as those produced by InstallShield.                   *
 * o Links to a library or executes a program that does any of the above   *
 *                                                                         *
 * The term "Nmap" should be taken to also include any portions or derived *
 * works of Nmap.  This list is not exclusive, but is meant to clarify our *
 * interpretation of derived works with some common examples.  Our         *
 * interpretation applies only to Nmap--we don't speak for other people's  *
 * GPL works.                                                              *
 *                                                                         *
 * If you have any questions about the GPL licensing restrictions on using *
 * Nmap in non-GPL works, we would be happy to help.  As mentioned above,  *
 * we also offer alternative license to integrate Nmap into proprietary    *
 * applications and appliances.  These contracts have been sold to dozens  *
 * of software vendors, and generally include a perpetual license as well  *
 * as providing for priority support and updates as well as helping to     *
 * fund the continued development of Nmap technology.  Please email        *
 * sales@insecure.com for further information.                             *
 *                                                                         *
 * As a special exception to the GPL terms, Insecure.Com LLC grants        *
 * permission to link the code of this program with any version of the     *
 * OpenSSL library which is distributed under a license identical to that  *
 * listed in the included COPYING.OpenSSL file, and distribute linked      *
 * combinations including the two. You must obey the GNU GPL in all        *
 * respects for all of the code used other than OpenSSL.  If you modify    *
 * this file, you may extend this exception to your version of the file,   *
 * but you are not obligated to do so.                                     *
 *                                                                         *
 * If you received these files with a written license agreement or         *
 * contract stating terms other than the terms above, then that            *
 * alternative license agreement takes precedence over these comments.     *
 *                                                                         *
 * Source is provided to this software because we believe users have a     *
 * right to know exactly what a program is going to do before they run it. *
 * This also allows you to audit the software for security holes (none     *
 * have been found so far).                                                *
 *                                                                         *
 * Source code also allows you to port Nmap to new platforms, fix bugs,    *
 * and add new features.  You are highly encouraged to send your changes   *
 * to nmap-dev@insecure.org for possible incorporation into the main       *
 * distribution.  By sending these changes to Fyodor or one of the         *
 * Insecure.Org development mailing lists, it is assumed that you are      *
 * offering the Nmap Project (Insecure.Com LLC) the unlimited,             *
 * non-exclusive right to reuse, modify, and relicense the code.  Nmap     *
 * will always be available Open Source, but this is important because the *
 * inability to relicense code has caused devastating problems for other   *
 * Free Software projects (such as KDE and NASM).  We also occasionally    *
 * relicense the code to third parties as discussed above.  If you wish to *
 * specify special license conditions of your contributions, just say so   *
 * when you send them.                                                     *
 *                                                                         *
 * This program is distributed in the hope that it will be useful, but     *
 * WITHOUT ANY WARRANTY; without even the implied warranty of              *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU       *
 * General Public License v2.0 for more details at                         *
 * http://www.gnu.org/licenses/gpl-2.0.html , or in the COPYING file       *
 * included with Nmap.                                                     *
 *                                                                         *
 ***************************************************************************/

/* $Id: ncat_proxy.c 15802 2009-10-10 02:41:06Z david $ */

#include "base64.h"
#include "http.h"
#include "nsock.h"
#include "ncat.h"
#include "sys_wrap.h"

#ifndef WIN32
#include <unistd.h>
#endif

#ifndef WIN32
/* SIG_CHLD handler */
static void proxyreaper(int signo)
{
    while (waitpid(-1, NULL, WNOHANG) > 0);
}
#endif

/* send a '\0'-terminated string. */
static int send_string(int sock, const char *s)
{
    return send(sock, s, strlen(s), 0);
}

static void http_server_handler(int c);
static char *http_code2str(int code);

static void fork_handler(int s, int c);

static int handle_connect(struct socket_buffer *client_sock,
    struct http_request *request);
static int handle_method(struct socket_buffer *client_sock,
    struct http_request *request);

/*
 * Simple forking HTTP proxy. It is an HTTP/1.0 proxy with knowledge of
 * HTTP/1.1. (The things lacking for HTTP/1.1 are the chunked transfer encoding
 * and the expect mechanism.) The proxy supports the CONNECT, GET, HEAD, and
 * POST methods. It supports Basic authentication of clients (use the
 * --proxy-auth option).
 *
 * HTTP/1.1 is defined in RFC 2616. Many comments refer to that document.
 * http://tools.ietf.org/html/rfc2616
 *
 * HTTP authentication is discussed in RFC 2617.
 * http://tools.ietf.org/html/rfc2617
 *
 * The CONNECT method is documented in an Internet draft and is specified as the
 * way to proxy HTTPS in RFC 2817, section 5.
 * http://tools.ietf.org/html/draft-luotonen-web-proxy-tunneling-01
 * http://tools.ietf.org/html/rfc2817#section-5
 *
 * The CONNECT method is not limited to HTTP, but is potentially capable of
 * connecting to any TCP port on any host. The proxy connection is requested
 * with an HTTP request, but after that, the proxy does no interpretation of the
 * data passing through it. See section 6 of the above mentioned draft for the
 * security implications.
 */
int ncat_http_server(void)
{
    int c, s;
    size_t sslen;
    union sockaddr_u conn;

#ifndef WIN32
    Signal(SIGCHLD, proxyreaper);
#endif

    s = do_listen(SOCK_STREAM, IPPROTO_TCP);

    for (;;) {
        sslen = sizeof(conn.storage);

        c = accept(s, &conn.sockaddr, (socklen_t *) &sslen);

        if (c == -1) {
            if (errno == EINTR)
                continue;
            die("accept");
        }

        if (!allow_access(&conn)) {
            Close(c);
            continue;
        }

        fork_handler(s, c);
    }

    return 0;
}

#ifdef WIN32
/* On Windows we don't actually fork but rather start a thread. */

static DWORD WINAPI handler_thread_func(void *data)
{
    http_server_handler(*((int *) data));
    free(data);

    return 0;
}

static void fork_handler(int s, int c)
{
    int *data;
    HANDLE thread;

    data = (int *) malloc(sizeof(int));
    *data = c;
    thread = CreateThread(NULL, 0, handler_thread_func, data, 0, NULL);
    if (thread == NULL) {
        if (o.verbose)
            logdebug("Error in CreateThread: %d\n", GetLastError());
        free(data);
        return;
    }
    CloseHandle(thread);
}
#else
static void fork_handler(int s, int c)
{
    int rc;

    rc = fork();
    if (rc == -1) {
        return;
    } else if (rc == 0) {
        Close(s);

        if (!o.debug) {
            Close(STDIN_FILENO);
            Close(STDOUT_FILENO);
            Close(STDERR_FILENO);
        }

        http_server_handler(c);
        exit(0);
    } else {
        Close(c);
    }
}
#endif

/* Is this one of the methods we can handle? */
static int method_is_known(const char *method)
{
    return strcmp(method, "CONNECT") == 0
        || strcmp(method, "GET") == 0
        || strcmp(method, "HEAD") == 0
        || strcmp(method, "POST") == 0;
}

static void http_server_handler(int c)
{
    int code;
    struct socket_buffer sock;
    struct http_request request;
    char *buf;

    socket_buffer_init(&sock, c);

    code = http_read_request_line(&sock, &buf);
    if (code != 0) {
        if (o.verbose)
            logdebug("Error reading Request-Line.\n");
        send_string(c, http_code2str(code));
        Close(c);
        return;
    }
    if (o.debug > 1)
        logdebug("Request-Line: %s", buf);
    code = http_parse_request_line(buf, &request);
    free(buf);
    if (code != 0) {
        if (o.verbose)
            logdebug("Error parsing Request-Line.\n");
        send_string(c, http_code2str(code));
        Close(c);
        return;
    }

    if (!method_is_known(request.method)) {
        if (o.debug > 1)
            logdebug("Bad method: %s.\n", request.method);
        http_request_free(&request);
        send_string(c, http_code2str(405));
        Close(c);
        return;
    }

    code = http_read_header(&sock, &buf);
    if (code != 0) {
        if (o.verbose)
            logdebug("Error reading header.\n");
        http_request_free(&request);
        send_string(c, http_code2str(code));
        Close(c);
        return;
    }
    if (o.debug > 1)
        logdebug("Header:\n%s", buf);
    code = http_request_parse_header(&request, buf);
    free(buf);
    if (code != 0) {
        if (o.verbose)
            logdebug("Error parsing header.\n");
        http_request_free(&request);
        send_string(c, http_code2str(code));
        Close(c);
        return;
    }

    /* Check authentication. */
    if (o.proxy_auth) {
        char *auth;
        int ret;

        auth = http_header_get_first(request.header, "Proxy-Authorization");
        if (auth == NULL) {
            /* No authentication sent. */
            http_request_free(&request);
            send_string(c, http_code2str(407));
            Close(c);
            return;
        }

        ret = http_check_auth_basic(o.proxy_auth, auth);
        free(auth);
        if (!ret) {
            /* Password doesn't match. */
            http_request_free(&request);
            /* RFC 2617, section 1.2: "If a proxy does not accept the
               credentials sent with a request, it SHOULD return a 407 (Proxy
               Authentication Required). */
            send_string(c, http_code2str(407));
            Close(c);
            return;
        }
    }

    if (strcmp(request.method, "CONNECT") == 0) {
        code = handle_connect(&sock, &request);
    } else if (strcmp(request.method, "GET") == 0
        || strcmp(request.method, "HEAD") == 0
        || strcmp(request.method, "POST") == 0) {
        code = handle_method(&sock, &request);
    } else {
        code = 500;
    }
    http_request_free(&request);

    if (code != 0) {
        send_string(c, http_code2str(code));
        Close(c);
        return;
    }

    Close(c);
}

static int handle_connect(struct socket_buffer *client_sock,
    struct http_request *request)
{
    union sockaddr_u su;
    size_t sslen = sizeof(su.storage);
    int maxfd, s;
    char *line;
    size_t len;
    fd_set m, r;

    if (request->uri.port == -1) {
        if (o.verbose)
            logdebug("No port number in CONNECT URI.\n");
        return 400;
    }
    if (o.debug > 1)
        logdebug("CONNECT to %s:%hu.\n", request->uri.host, request->uri.port);

    if (!resolve(request->uri.host, request->uri.port, &su.storage, &sslen, o.af)) {
        if (o.debug)
            logdebug("Can't resolve name %s.\n", request->uri.host);
        return 504;
    }

    s = Socket(su.storage.ss_family, SOCK_STREAM, IPPROTO_TCP);

    if (connect(s, &su.sockaddr, sslen) == -1) {
        if (o.debug)
            logdebug("Can't connect to %s.\n", inet_socktop(&su));
        Close(s);
        return 504;
    }

    send_string(client_sock->sd, http_code2str(200));

    /* Clear out whatever is left in the socket buffer. The client may have
       already sent the first part of its request to the origin server. */
    line = socket_buffer_remainder(client_sock, &len);
    if (send(s, line, len, 0) < 0) {
        if (o.debug)
            logdebug("Error sending %u leftover bytes: %s.\n", len, strerror(errno));
        Close(s);
        return 0;
    }

    maxfd = client_sock->sd < s ? s : client_sock->sd;
    FD_ZERO(&m);
    FD_SET(client_sock->sd, &m);
    FD_SET(s, &m);

    errno = 0;

    while (!socket_errno() || socket_errno() == EINTR) {
        char buf[DEFAULT_TCP_BUF_LEN];
        int len, numready;

        r = m;

        numready = fselect(maxfd + 1, &r, NULL, NULL, NULL);

        zmem(buf, sizeof(buf));

        if (FD_ISSET(client_sock->sd, &r)) {
            if ((len = recv(client_sock->sd, buf, sizeof(buf), 0)) < 0)
                continue;

            if (!len)
                break;

            if (send(s, buf, len, 0) < 0)
                continue;
        }

        if (FD_ISSET(s, &r)) {
            if ((len = recv(s, buf, sizeof(buf), 0)) < 0)
                continue;

            if (!len)
                break;

            if (send(client_sock->sd, buf, len, 0) < 0)
                continue;
        }
    }

    close(s);

    return 0;
}

static int do_transaction(struct http_request *request,
    struct socket_buffer *client_sock, struct socket_buffer *server_sock);

/* Generic handler for GET, HEAD, and POST methods. */
static int handle_method(struct socket_buffer *client_sock,
    struct http_request *request)
{
    struct socket_buffer server_sock;
    union sockaddr_u su;
    size_t sslen = sizeof(su.storage);
    int code;
    int s;

    if (strcmp(request->uri.scheme, "http") != 0) {
        if (o.verbose)
            logdebug("Unknown scheme in URI: %s.\n", request->uri.scheme);
        return 400;
    }
    if (request->uri.port == -1) {
        if (o.verbose)
            logdebug("Unknown port in URI.\n");
        return 400;
    }

    if (!resolve(request->uri.host, request->uri.port, &su.storage, &sslen, o.af)) {
        if (o.debug)
            logdebug("Can't resolve name %s:%d.\n", request->uri.host, request->uri.port);
        return 504;
    }

    /* RFC 2616, section 5.1.2: "In order to avoid request loops, a proxy MUST
       be able to recognize all of its server names, including any aliases,
       local variations, and the numeric IP address. */
    if (request->uri.port == o.portno && addr_is_local(&su)) {
        if (o.verbose)
            logdebug("Proxy loop detected: %s:%d\n", request->uri.host, request->uri.port);
        return 403;
    }

    s = Socket(su.storage.ss_family, SOCK_STREAM, IPPROTO_TCP);

    if (connect(s, &su.sockaddr, sslen) == -1) {
        if (o.debug)
            logdebug("Can't connect to %s.\n", inet_socktop(&su));
        Close(s);
        return 504;
    }

    socket_buffer_init(&server_sock, s);

    code = do_transaction(request, client_sock, &server_sock);

    close(server_sock.sd);

    if (code != 0)
        return code;

    return 0;
}

/* Do a GET, HEAD, or POST transaction. */
static int do_transaction(struct http_request *request,
    struct socket_buffer *client_sock, struct socket_buffer *server_sock)
{
    char buf[BUFSIZ];
    struct http_response response;
    char *line;
    char *request_str, *response_str;
    size_t len;
    int code, n;

    /* We don't handle the chunked transfer encoding, which in the absence of a
       Content-Length is the only way we know the end of a request body. RFC
       2616, section 4.4 says, "If a request contains a message-body and a
       Content-Length is not given, the server SHOULD respond with 400 (bad
       request) if it cannot determine the length of the message, or with 411
       (length required) if it wishes to insist on receiving a valid
       Content-Length." */
    if (strcmp(request->method, "POST") == 0 && request->content_length == 0) {
        if (o.debug)
            logdebug("POST request with no Content-Length.\n");
        return 400;
    }

    /* The version we use to talk to the server. */
    request->version = HTTP_10;

    /* Remove headers that only apply to our connection with the client. */
    code = http_header_remove_hop_by_hop(&request->header);
    if (code != 0) {
        if (o.verbose)
            logdebug("Error removing hop-by-hop headers.\n");
        return code;
    }

    /* Build the Host header. */
    if (request->uri.port == -1 || request->uri.port == 80)
        n = Snprintf(buf, sizeof(buf), "%s", request->uri.host);
    else
        n = Snprintf(buf, sizeof(buf), "%s:%hu", request->uri.host, request->uri.port);
    if (n < 0 || n >= sizeof(buf)) {
        /* Request Entity Too Large. */
        return 501;
    }
    request->header = http_header_set(request->header, "Host", buf);

    request->header = http_header_set(request->header, "Connection", "close");

    /* Send the request to the server. */
    request_str = http_request_to_string(request, &len);
    n = send(server_sock->sd, request_str, len, 0);
    free(request_str);
    if (n < 0)
        return 504;
    /* Send the request body, if any. Count up to Content-Length. */
    while (request->bytes_transferred < request->content_length) {
        n = socket_buffer_read(client_sock, buf, MIN(sizeof(buf), request->content_length - request->bytes_transferred));
        if (n < 0)
            return 504;
        if (n == 0)
            break;
        request->bytes_transferred += n;
        n = send(server_sock->sd, buf, n, 0);
        if (n < 0)
            return 504;
    }
    if (o.debug && request->bytes_transferred < request->content_length)
        logdebug("Received only %lu request body bytes (Content-Length was %lu).\n", request->bytes_transferred, request->content_length);


    /* Read the response. */
    code = http_read_status_line(server_sock, &line);
    if (o.debug > 1)
        logdebug("Status-Line: %s", line);
    if (code != 0) {
        if (o.verbose)
            logdebug("Error reading Status-Line.\n");
        return 0;
    }
    code = http_parse_status_line(line, &response);
    free(line);
    if (code != 0) {
        if (o.verbose)
            logdebug("Error parsing Status-Line.\n");
        return 0;
    }

    code = http_read_header(server_sock, &line);
    if (code != 0) {
        if (o.verbose)
            logdebug("Error reading header.\n");
        return 0;
    }
    if (o.debug > 1)
        logdebug("Response header:\n%s", line);

    code = http_response_parse_header(&response, line);
    free(line);
    if (code != 0) {
        if (o.verbose)
            logdebug("Error parsing response header.\n");
        return 0;
    }


    /* The version we use to talk to the client. */
    response.version = HTTP_10;

    /* Remove headers that only apply to our connection with the server. */
    code = http_header_remove_hop_by_hop(&response.header);
    if (code != 0) {
        if (o.verbose)
            logdebug("Error removing hop-by-hop headers.\n");
        return code;
    }

    response.header = http_header_set(response.header, "Connection", "close");

    /* Send the response to the client. */
    response_str = http_response_to_string(&response, &len);
    n = send(client_sock->sd, response_str, len, 0);
    free(response_str);
    if (n < 0) {
        http_response_free(&response);
        return 504;
    }
    /* If the Content-Length is 0, read until the connection is closed.
       Otherwise read until the Content-Length. At this point it's too late to
       return our own error code so return 0 in case of any error. */
    while (response.content_length == 0
        || response.bytes_transferred < response.content_length) {
        size_t remaining = response.content_length - response.bytes_transferred;
        size_t count;

        count = sizeof(buf);
        if (response.content_length > 0 && remaining < count)
            count = remaining;
        n = socket_buffer_read(server_sock, buf, count);
        if (n <= 0)
            break;
        response.bytes_transferred += n;
        n = send(client_sock->sd, buf, n, 0);
        if (n < 0)
            break;
    }

    http_response_free(&response);

    return 0;
}

static char *http_code2str(int code)
{
    /* See RFC 2616, section 6.1.1 for status codes. */
    switch (code) {
    case 200:
        return "HTTP/1.0 200 OK\r\n\r\n";
    case 400:
        return "HTTP/1.0 400 Bad Request\r\n\r\n";
    case 403:
        return "HTTP/1.0 403 Forbidden\r\n\r\n";
    case 405:
        /* RFC 2616, section 14.7 for Allow. */
        return "\
HTTP/1.0 405 Method Not Allowed\r\n\
Allow: CONNECT, GET, HEAD, POST\r\n\
\r\n";
    case 407:
        return "\
HTTP/1.0 407 Proxy Authentication Required\r\n\
Proxy-Authenticate: Basic realm=\"Ncat\"\r\n\
\r\n";
    case 413:
        return "HTTP/1.0 413 Request Entity Too Large\r\n\r\n";
    case 501:
        return "HTTP/1.0 501 Not Implemented\r\n\r\n";
    case 504:
        return "HTTP/1.0 504 Gateway Timeout\r\n\r\n";
    default:
        return "HTTP/1.0 500 Internal Server Error\r\n\r\n";
    }

    return NULL;
}

/*
 * Return an HTTP/1.1 CONNECT proxy request to send to an HTTP proxy server. If
 * proxy_auth is NULL, HTTP Proxy-Authorization headers are not included in the
 * request.
 */
char *http_proxy_client_request(char *proxy_auth)
{
    char *b64_auth;
    static char proxy_request[DEFAULT_BUF_LEN];
    int pos;
    const char *proxyhost;
    char hostbuf[INET6_ADDRSTRLEN + 9]; /* [ + address + ] + : + port + \0 */
    const char *host = inet_socktop(&httpconnect);
    unsigned short port = inet_port(&httpconnect);
    char *s6s = o.af == AF_INET6 ? "[" : "", *s6e = o.af == AF_INET6 ? "]" : "";

    if (port)
        Snprintf(hostbuf, sizeof hostbuf, "%s%s%s:%hu", s6s, host, s6e, port);
    else
        Snprintf(hostbuf, sizeof hostbuf, "%s%s%s", s6s, host, s6e);

    proxyhost = inet_socktop(&targetss);

    if (o.debug)
        logdebug("Proxy CONNECT target: %s\n", hostbuf);

    pos = Snprintf(proxy_request, sizeof(proxy_request),
                   "CONNECT %s HTTP/1.1\r\n", hostbuf);

    if (proxy_auth != NULL) {
        b64_auth = b64enc((unsigned char *) proxy_auth, strlen((char *)proxy_auth));

        if (o.debug)
            logdebug("Proxy auth (base64enc): %s\n", b64_auth);

        pos += Snprintf(proxy_request + pos, sizeof(proxy_request) - pos,
                        "Proxy-Authorization: Basic %s\r\n", b64_auth);

        free(b64_auth);
    }

    Snprintf(proxy_request + pos, sizeof(proxy_request) - pos,
             "Host: %s\r\n\r\n", proxyhost);

    return (proxy_request);
}

/*
 * Handle SOCKS4 CD field error reporting. Return the error message to be used
 * in the final Ncat output. (It's final because these are all fatal errors.)
 *
 * See: http://archive.socks.permeo.com/protocol/socks4.protocol
 *
 * These error messages are taken verbatim from socks4.protocol (above)
 */
char *socks4_error(char cd)
{
    switch (cd) {
        case SOCKS_CONN_REF:
            return "request rejected or failed";
            break;

        case SOCKS_CONN_IDENT:
            return "request rejected because SOCKS4 server cannot connect to identd";
            break;

        case SOCKS_CONN_IDENTDIFF:
            return "request rejected because SOCKS4 client and identd reported different userid's";
            break;

        default:
            return "Invalid SOCKS4 error code. Broken SOCKS4 implementation?";
    }
}

Generated by  Doxygen 1.6.0   Back to index