C http proxy remote server issues

**alexhollis** · 04-16-2014

I'm having an issue with my attempt at a single threaded proxy server. It appears I have established a proper connection with the remote server specified by the client (ex: "http://server.ip.addr:8083/www.google.com" connects to google)

The issue is I don't seem to be getting anything from the website, which results in my browser getting stuck on loading, and nothing happening, or so it seems...

Here's what I've written so far, I'd greatly any solutions and feedback.

[ProxyV2.c]

Code:

#include <stdio.h>#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <err.h>
#include <string.h>


/********************************************************           
    *         HTTP Web Proxy coded in C                       *   
    *                                                      *   
    * Authors: Alexander Hollis, Isaias Delgado               *   
    *                                                      *   
    * Purpose:  Demonstration of a HTTP Proxy in C            *   
    *                                                      *   
    * Usage:                                               *   
    *      Refer to included manual for proper usage.      *   
    ********************************************************/




    












int main() {
    
    char response[] = "HTTP/1.1 200 OK\r\n"
    "Content-Type: text/html; charset=UTF-8\r\n\r\n"
    "<doctype !html>\r\n";
    
    char error[] = "HTTP/1.1 404 Not Found\r\n"
    "Content-Type: text/html; charset=UTF-8\r\n\r\n"
    "<doctype !html><html><head><title>HTML Generator Sample Page</title>"
    "</head><body><h2>404: Page Not Found</h2><p>The page you requested was not able to be located, please check your address!</p>"
    "</body></html>\r\n\n";
    
    char buffer[256], *token;
    char tokens [256][25];
    int one = 1, client_fd;
    struct sockaddr_in svr_addr, cli_addr, out_addr;
    socklen_t sin_len = sizeof(cli_addr);
    
    int sock = socket(AF_INET, SOCK_STREAM, 0);
    int remote = socket(AF_INET, SOCK_STREAM, 0);
    
    if (sock < 0)
    err(1, "can't open socket");


    setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(int));
    setsockopt(remote, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(int));
    
    int port = 8083;
    svr_addr.sin_family = AF_INET;
    svr_addr.sin_addr.s_addr = INADDR_ANY;
    svr_addr.sin_port = htons(port);
    
    out_addr.sin_family = AF_INET;
    out_addr.sin_addr.s_addr = INADDR_ANY;
    out_addr.sin_port = htons(80);


    if (bind(sock, (struct sockaddr *) &svr_addr, sizeof(svr_addr)) == -1) {
        close(sock);
        err(1, "Can't bind");
    }


    listen(sock, 5);
    int bytesread, byteswritten;
    
    char *url;
    
    struct hostent *h;
    
    int remote_fd;
    
    char page[2000];
    char *html;
    
    char get[] = "GET /index.html HTTP/1.1\r\n\r\n";
    
    while(1) {
        
        bytesread =0; 
        byteswritten=0;
        
        
        
        client_fd = accept(sock, (struct sockaddr *) &cli_addr, &sin_len);
        
        read(client_fd, buffer, 256);
        //write(client_fd, error, sizeof(error));
        //send(client_fd, &error, sizeof(error)-1, 0);
        
        int x=0;
        for(token = strtok(buffer, " "); token!=NULL; token = strtok(NULL, " ") )
        {
            strcpy(tokens[x],token);
            x++;
        }
        url = tokens[1] +1;
        printf("url: %s\n", url);
        if(strcmp(url, "index.html") != 0) {
        h = gethostbyname(url);
        bcopy ( h->h_addr, &(out_addr.sin_addr.s_addr), h->h_length);
        remote_fd = connect(remote, (struct sockaddr *) &out_addr,(socklen_t)sizeof(out_addr));
        printf("remote_fd = %d\n",remote_fd);
        
        send(remote_fd, &get, sizeof(get)-1,0);
        bytesread = read(remote_fd, &page, 2000);
        
        html = (char *)malloc(sizeof(char) * bytesread);
        int k=0;
        for(k=0; k< bytesread; k++) {
        html[k] = page[k];
        printf("%c",html[k]);
        }
        printf("\n");
        
        printf("page[3]=%c\n",page[3]);
        //write(client_fd, response, sizeof(response)-1);
        write(client_fd, html, sizeof(html));
        }
        
        
    
    
    
    
    
    }
}

Thank You for reading!

~Alex

**alexhollis** · 04-18-2014

I've gotten it to now connect to external websites, but they keep sending back a 404 page, or bad request.

I'm using the get request "GET /index.html HTTP/1.0\r\n\r\n"

Here's the new code:

[ProxyV2.c]

Code:

#include <stdio.h>#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <err.h>
#include <string.h>


/********************************************************           
    * Multithreaded HTTP Web Proxy coded in C               *   
    *                                                      *   
    * Authors: Alexander Hollis, Isaias Delgado               *   
    *                                                      *   
    * Purpose:  Demonstration of a Multi-Thread Proxy in C *   
    *                                                      *   
    * Usage:                                               *   
    *      Refer to included manual for proper usage.      *   
    ********************************************************/




    












int main() {
    
    char response[] = "HTTP/1.1 200 OK\r\n"
    "Content-Type: text/html; charset=UTF-8\r\n\r\n"
    "<doctype !html>\r\n";
    
    char error[] = "HTTP/1.1 404 Not Found\r\n"
    "Content-Type: text/html; charset=UTF-8\r\n\r\n"
    "<doctype !html><html><head><title>HTML Generator Sample Page</title>"
    "</head><body><h2>404: Page Not Found</h2><p>The page you requested was not able to be located, please check your address!</p>"
    "</body></html>\r\n\n";
    
    char buffer[256], *token;
    char tokens [256][25];
    int one = 1, client_fd;
    struct sockaddr_in svr_addr, cli_addr, out_addr;
    socklen_t sin_len = sizeof(cli_addr);
    
    int sock = socket(AF_INET, SOCK_STREAM, 0);
    int remote;
    
    if (sock < 0)
    err(1, "can't open socket");


    setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(int));
    //setsockopt(remote, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(int));
    
    int port = 8083;
    svr_addr.sin_family = AF_INET;
    svr_addr.sin_addr.s_addr = INADDR_ANY;
    svr_addr.sin_port = htons(port);
    
    out_addr.sin_family = AF_INET;
    out_addr.sin_addr.s_addr = INADDR_ANY;
    out_addr.sin_port = htons(80);


    if (bind(sock, (struct sockaddr *) &svr_addr, sizeof(svr_addr)) == -1) {
        close(sock);
        err(1, "Can't bind");
    }


    listen(sock, 5);
    int bytesread, byteswritten;
    
    char *url;
    
    //struct hostent *h;
    
    struct addrinfo hints, *res, *p;
    
    int remote_fd;
    
    char page[2000];
    char *html;
    int err;
    char get[] = "GET /index.html HTTP/1.0\r\n\r\n";
    
    while(1) {
        
        bytesread =0; 
        byteswritten=0;
        
        memset(&hints, 0, sizeof(hints));
        hints.ai_socktype = SOCK_STREAM;
        hints.ai_family = AF_INET;
        
        client_fd = accept(sock, (struct sockaddr *) &cli_addr, &sin_len);
        
        read(client_fd, buffer, 256);
        //write(client_fd, error, sizeof(error));
        //send(client_fd, &error, sizeof(error)-1, 0);
        
        int x=0;
        for(token = strtok(buffer, " "); token!=NULL; token = strtok(NULL, " ") )
        {
            strcpy(tokens[x],token);
            x++;
        }
        url = tokens[1] +1;
        
        //strcat(get,url);
        //strcat(get,"/index.html HTTP/1.0\n\n");
        
        //printf("GET: %s\n",get);
        
        if(strcmp(url, "index.html") != 0) {
        //h = gethostbyname(url);
        
        
        if((err = getaddrinfo(url, "http", &hints, &res)) != 0) printf("Error finding address, addrinfo returned %d.\n",err);
        
        //out_addr.s_addr = ((struct sockaddr_in *)(res->ai_addr))->sin_addr.s_addr;
        //bcopy ( (char *)res->ai_addr, (char *)&(out_addr.sin_addr.s_addr), res->ai_addrlen);
        
        for(p = res; p!= NULL; p = p->ai_next) {
        
            if((remote_fd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
            
                perror("socket");
                continue;
            
            }
            
            if(connect(remote_fd, p->ai_addr, p->ai_addrlen) == -1) {
        
                close(remote);
                perror("connect");
                continue;
        }
        
        break;
        }
        
        while (1) {
        printf("url: %s\n", url);
        
        
        
        
        
        
        
        
        
        
        
        
        
        //if(remote_fd = connect(remote, (struct sockaddr *) &out_addr, sizeof(out_addr)) < 0) printf("Connection Failed!\n");
        //printf("remote_fd = %d\n",remote_fd);
        if(send(remote_fd, get, sizeof(get),0) < 0) printf("Send Failed!\n");
        bytesread = recv(remote_fd, page, 2000,0);
        if(bytesread > 0) printf("Receiving Data from Host...\n\n\n");
        puts(page);
        
        /*html = (char *)malloc(sizeof(char) * bytesread);
        int k=0;
        for(k=0; k< bytesread; k++) {
        html[k] = page[k];
        printf("%c",html[k]);
        }
        printf("\n");
        
        printf("page[3]=%c\n",page[3]);
        */
        
        //clearwrite(client_fd, response, sizeof(response)-1);
        write(client_fd, page, sizeof(page));
        break;
        }
        
        
    
    
    
    
    
    }
}
}

**Salem** · 04-18-2014

https://www.wireshark.org/
An invaluable tool for debugging network programs.
Just use it to compare the normal traffic with the proxied traffic to figure out what your proxy failed to do.

FWIW, implementing a reliable transparent proxy is a good first step, before you try to modify the behaviour.

Thread: C http proxy remote server issues

Thread Tools

Search Thread

Display

C http proxy remote server issues

Updated Code:

Similar Threads

I am writing a (http) proxy server in windows, it doesn't work I expect?

How to make a conection to a http proxy with sockets

Small HTTP proxy

Download File through HTTP Proxy

http proxy - receive problem

Tags for this Thread