deb-novnc/utils/websocket.c

/*
 * WebSocket lib with support for "wss://" encryption.
 * Copyright 2010 Joel Martin
 * Licensed under LGPL version 3 (see docs/LICENSE.LGPL-3)
 *
 * You can make a cert/key with openssl using:
 * openssl req -new -x509 -days 365 -nodes -out self.pem -keyout self.pem
 * as taken from http://docs.python.org/dev/library/ssl.html#certificates
 */
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <strings.h>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <signal.h> // daemonizing
#include <fcntl.h>  // daemonizing
#include <openssl/err.h>
#include <openssl/ssl.h>
#include <resolv.h>      /* base64 encode/decode */
#include "websocket.h"

const char server_handshake[] = "HTTP/1.1 101 Web Socket Protocol Handshake\r\n\
Upgrade: WebSocket\r\n\
Connection: Upgrade\r\n\
%sWebSocket-Origin: %s\r\n\
%sWebSocket-Location: %s://%s%s\r\n\
%sWebSocket-Protocol: sample\r\n\
\r\n%s";

const char policy_response[] = "<cross-domain-policy><allow-access-from domain=\"*\" to-ports=\"*\" /></cross-domain-policy>\n";

/*
 * Global state
 *
 *   Warning: not thread safe
 */
int ssl_initialized = 0;
int pipe_error = 0;
char *tbuf, *cbuf, *tbuf_tmp, *cbuf_tmp;
unsigned int bufsize, dbufsize;
settings_t settings;

void traffic(char * token) {
    if ((settings.verbose) && (! settings.daemon)) {
        fprintf(stdout, "%s", token);
        fflush(stdout);
    }
}

void error(char *msg)
{
    perror(msg);
}

void fatal(char *msg)
{
    perror(msg);
    exit(1);
}

/* resolve host with also IP address parsing */ 
int resolve_host(struct in_addr *sin_addr, const char *hostname) 
{ 
    if (!inet_aton(hostname, sin_addr)) { 
        struct addrinfo *ai, *cur; 
        struct addrinfo hints; 
        memset(&hints, 0, sizeof(hints)); 
        hints.ai_family = AF_INET; 
        if (getaddrinfo(hostname, NULL, &hints, &ai)) 
            return -1; 
        for (cur = ai; cur; cur = cur->ai_next) { 
            if (cur->ai_family == AF_INET) { 
                *sin_addr = ((struct sockaddr_in *)cur->ai_addr)->sin_addr; 
                freeaddrinfo(ai); 
                return 0; 
            } 
        } 
        freeaddrinfo(ai); 
        return -1; 
    } 
    return 0; 
} 


/*
 * SSL Wrapper Code
 */

ssize_t ws_recv(ws_ctx_t *ctx, void *buf, size_t len) {
    if (ctx->ssl) {
        //handler_msg("SSL recv\n");
        return SSL_read(ctx->ssl, buf, len);
    } else {
        return recv(ctx->sockfd, buf, len, 0);
    }
}

ssize_t ws_send(ws_ctx_t *ctx, const void *buf, size_t len) {
    if (ctx->ssl) {
        //handler_msg("SSL send\n");
        return SSL_write(ctx->ssl, buf, len);
    } else {
        return send(ctx->sockfd, buf, len, 0);
    }
}

ws_ctx_t *ws_socket(int socket) {
    ws_ctx_t *ctx;
    ctx = malloc(sizeof(ws_ctx_t));
    ctx->sockfd = socket;
    ctx->ssl = NULL;
    ctx->ssl_ctx = NULL;
    return ctx;
}

ws_ctx_t *ws_socket_ssl(int socket, char * certfile) {
    int ret;
    char msg[1024];
    ws_ctx_t *ctx;
    ctx = ws_socket(socket);

    // Initialize the library
    if (! ssl_initialized) {
        SSL_library_init();
        OpenSSL_add_all_algorithms();
        SSL_load_error_strings();
        ssl_initialized = 1;

    }

    ctx->ssl_ctx = SSL_CTX_new(TLSv1_server_method());
    if (ctx->ssl_ctx == NULL) {
        ERR_print_errors_fp(stderr);
        fatal("Failed to configure SSL context");
    }

    if (SSL_CTX_use_PrivateKey_file(ctx->ssl_ctx, certfile,
                                     SSL_FILETYPE_PEM) <= 0) {
        sprintf(msg, "Unable to load private key file %s\n", certfile);
        fatal(msg);
    }

    if (SSL_CTX_use_certificate_file(ctx->ssl_ctx, certfile,
                                     SSL_FILETYPE_PEM) <= 0) {
        sprintf(msg, "Unable to load certificate file %s\n", certfile);
        fatal(msg);
    }

//    if (SSL_CTX_set_cipher_list(ctx->ssl_ctx, "DEFAULT") != 1) {
//        sprintf(msg, "Unable to set cipher\n");
//        fatal(msg);
//    }

    // Associate socket and ssl object
    ctx->ssl = SSL_new(ctx->ssl_ctx);
    SSL_set_fd(ctx->ssl, socket);

    ret = SSL_accept(ctx->ssl);
    if (ret < 0) {
        ERR_print_errors_fp(stderr);
        return NULL;
    }

    return ctx;
}

int ws_socket_free(ws_ctx_t *ctx) {
    if (ctx->ssl) {
        SSL_free(ctx->ssl);
        ctx->ssl = NULL;
    }
    if (ctx->ssl_ctx) {
        SSL_CTX_free(ctx->ssl_ctx);
        ctx->ssl_ctx = NULL;
    }
    if (ctx->sockfd) {
        close(ctx->sockfd);
        ctx->sockfd = 0;
    }
    free(ctx);
}

/* ------------------------------------------------------- */


int encode(u_char const *src, size_t srclength, char *target, size_t targsize) {
    int i, sz = 0, len = 0;
    unsigned char chr;
    target[sz++] = '\x00';
    len = __b64_ntop(src, srclength, target+sz, targsize-sz);
    if (len < 0) {
        return len;
    }
    sz += len;
    target[sz++] = '\xff';
    return sz;
}

int decode(char *src, size_t srclength, u_char *target, size_t targsize) {
    char *start, *end, cntstr[4];
    int i, len, framecount = 0, retlen = 0;
    unsigned char chr;
    if ((src[0] != '\x00') || (src[srclength-1] != '\xff')) {
        handler_emsg("WebSocket framing error\n");
        return -1;
    }
    start = src+1; // Skip '\x00' start
    do {
        /* We may have more than one frame */
        end = memchr(start, '\xff', srclength);
        *end = '\x00';
        len = __b64_pton(start, target+retlen, targsize-retlen);
        if (len < 0) {
            return len;
        }
        retlen += len;
        start = end + 2; // Skip '\xff' end and '\x00' start 
        framecount++;
    } while (end < (src+srclength-1));
    if (framecount > 1) {
        snprintf(cntstr, 3, "%d", framecount);
        traffic(cntstr);
    }
    return retlen;
}

int parse_handshake(char *handshake, headers_t *headers) {
    char *start, *end;

    if ((strlen(handshake) < 92) || (bcmp(handshake, "GET ", 4) != 0)) {
        return 0;
    }
    start = handshake+4;
    end = strstr(start, " HTTP/1.1");
    if (!end) { return 0; }
    strncpy(headers->path, start, end-start);
    headers->path[end-start] = '\0';

    start = strstr(handshake, "\r\nHost: ");
    if (!start) { return 0; }
    start += 8;
    end = strstr(start, "\r\n");
    strncpy(headers->host, start, end-start);
    headers->host[end-start] = '\0';

    start = strstr(handshake, "\r\nOrigin: ");
    if (!start) { return 0; }
    start += 10;
    end = strstr(start, "\r\n");
    strncpy(headers->origin, start, end-start);
    headers->origin[end-start] = '\0';
   
    start = strstr(handshake, "\r\n\r\n");
    if (!start) { return 0; }
    start += 4;
    if (strlen(start) == 8) {
        strncpy(headers->key3, start, 8);
        headers->key3[8] = '\0';

        start = strstr(handshake, "\r\nSec-WebSocket-Key1: ");
        if (!start) { return 0; }
        start += 22;
        end = strstr(start, "\r\n");
        strncpy(headers->key1, start, end-start);
        headers->key1[end-start] = '\0';
    
        start = strstr(handshake, "\r\nSec-WebSocket-Key2: ");
        if (!start) { return 0; }
        start += 22;
        end = strstr(start, "\r\n");
        strncpy(headers->key2, start, end-start);
        headers->key2[end-start] = '\0';
    } else {
        headers->key1[0] = '\0';
        headers->key2[0] = '\0';
        headers->key3[0] = '\0';
    }

    return 1;
}

int gen_md5(headers_t *headers, char *target) {
    unsigned int i, spaces1 = 0, spaces2 = 0;
    unsigned long num1 = 0, num2 = 0;
    unsigned char buf[17];
    for (i=0; i < strlen(headers->key1); i++) {
        if (headers->key1[i] == ' ') {
            spaces1 += 1;
        }
        if ((headers->key1[i] >= 48) && (headers->key1[i] <= 57)) {
            num1 = num1 * 10 + (headers->key1[i] - 48);
        }
    }
    num1 = num1 / spaces1;

    for (i=0; i < strlen(headers->key2); i++) {
        if (headers->key2[i] == ' ') {
            spaces2 += 1;
        }
        if ((headers->key2[i] >= 48) && (headers->key2[i] <= 57)) {
            num2 = num2 * 10 + (headers->key2[i] - 48);
        }
    }
    num2 = num2 / spaces2;

    /* Pack it big-endian */
    buf[0] = (num1 & 0xff000000) >> 24;
    buf[1] = (num1 & 0xff0000) >> 16;
    buf[2] = (num1 & 0xff00) >> 8;
    buf[3] =  num1 & 0xff;

    buf[4] = (num2 & 0xff000000) >> 24;
    buf[5] = (num2 & 0xff0000) >> 16;
    buf[6] = (num2 & 0xff00) >> 8;
    buf[7] =  num2 & 0xff;

    strncpy(buf+8, headers->key3, 8);
    buf[16] = '\0';

    md5_buffer(buf, 16, target);
    target[16] = '\0';

    return 1;
}

    

ws_ctx_t *do_handshake(int sock) {
    char handshake[4096], response[4096], trailer[17];
    char *scheme, *pre;
    headers_t headers;
    int len, ret;
    ws_ctx_t * ws_ctx;

    // Peek, but don't read the data
    len = recv(sock, handshake, 1024, MSG_PEEK);
    handshake[len] = 0;
    if (len == 0) {
        handler_msg("ignoring empty handshake\n");
        close(sock);
        return NULL;
    } else if (bcmp(handshake, "<policy-file-request/>", 22) == 0) {
        len = recv(sock, handshake, 1024, 0);
        handshake[len] = 0;
        handler_msg("sending flash policy response\n");
        send(sock, policy_response, sizeof(policy_response), 0);
        close(sock);
        return NULL;
    } else if ((bcmp(handshake, "\x16", 1) == 0) ||
               (bcmp(handshake, "\x80", 1) == 0)) {
        // SSL
        if (! settings.cert) { return NULL; }
        ws_ctx = ws_socket_ssl(sock, settings.cert);
        if (! ws_ctx) { return NULL; }
        scheme = "wss";
        handler_msg("using SSL socket\n");
    } else if (settings.ssl_only) {
        handler_msg("non-SSL connection disallowed\n");
        close(sock);
        return NULL;
    } else {
        ws_ctx = ws_socket(sock);
        if (! ws_ctx) { return NULL; }
        scheme = "ws";
        handler_msg("using plain (not SSL) socket\n");
    }
    len = ws_recv(ws_ctx, handshake, 4096);
    if (len == 0) {
        handler_emsg("Client closed during handshake\n");
        close(sock);
        return NULL;
    }
    handshake[len] = 0;

    if (!parse_handshake(handshake, &headers)) {
        handler_emsg("Invalid WS request\n");
        close(sock);
        return NULL;
    }

    if (headers.key3[0] != '\0') {
        gen_md5(&headers, trailer);
        pre = "Sec-";
        handler_msg("using protocol version 76\n");
    } else {
        trailer[0] = '\0';
        pre = "";
        handler_msg("using protocol version 75\n");
    }
    
    sprintf(response, server_handshake, pre, headers.origin, pre, scheme,
            headers.host, headers.path, pre, trailer);
    //handler_msg("response: %s\n", response);
    ws_send(ws_ctx, response, strlen(response));

    return ws_ctx;
}

void signal_handler(sig) {
    switch (sig) {
        case SIGHUP: break; // ignore for now
        case SIGPIPE: pipe_error = 1; break; // handle inline
        case SIGTERM: exit(0); break;
    }
}

void daemonize(int keepfd) {
    int pid, i;

    umask(0);
    chdir('/');
    setgid(getgid());
    setuid(getuid());

    /* Double fork to daemonize */
    pid = fork();
    if (pid<0) { fatal("fork error"); }
    if (pid>0) { exit(0); }  // parent exits
    setsid();                // Obtain new process group
    pid = fork();
    if (pid<0) { fatal("fork error"); }
    if (pid>0) { exit(0); }  // parent exits

    /* Signal handling */
    signal(SIGHUP, signal_handler);   // catch HUP
    signal(SIGTERM, signal_handler);  // catch kill

    /* Close open files */
    for (i=getdtablesize(); i>=0; --i) {
        if (i != keepfd) {
            close(i);
        } else if (settings.verbose) {
            printf("keeping fd %d\n", keepfd);
        }
    }
    i=open("/dev/null", O_RDWR);  // Redirect stdin
    dup(i);                       // Redirect stdout
    dup(i);                       // Redirect stderr
}


void start_server() {
    int lsock, csock, pid, clilen, sopt = 1, i;
    struct sockaddr_in serv_addr, cli_addr;
    ws_ctx_t *ws_ctx;

    /* Initialize buffers */
    bufsize = 65536;
    if (! (tbuf = malloc(bufsize)) )
            { fatal("malloc()"); }
    if (! (cbuf = malloc(bufsize)) )
            { fatal("malloc()"); }
    if (! (tbuf_tmp = malloc(bufsize)) )
            { fatal("malloc()"); }
    if (! (cbuf_tmp = malloc(bufsize)) )
            { fatal("malloc()"); }

    lsock = socket(AF_INET, SOCK_STREAM, 0);
    if (lsock < 0) { error("ERROR creating listener socket"); }
    bzero((char *) &serv_addr, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(settings.listen_port);

    /* Resolve listen address */
    if (settings.listen_host && (settings.listen_host[0] != '\0')) {
        if (resolve_host(&serv_addr.sin_addr, settings.listen_host) < -1) {
            fatal("Could not resolve listen address");
        }
    } else {
        serv_addr.sin_addr.s_addr = INADDR_ANY;
    }

    setsockopt(lsock, SOL_SOCKET, SO_REUSEADDR, (char *)&sopt, sizeof(sopt));
    if (bind(lsock, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
        fatal("ERROR on binding listener socket");
    }
    listen(lsock,100);

    signal(SIGPIPE, signal_handler);  // catch pipe

    if (settings.daemon) {
        daemonize(lsock);
    }

    // Reep zombies
    signal(SIGCHLD, SIG_IGN);

    printf("Waiting for connections on %s:%d\n",
            settings.listen_host, settings.listen_port);

    while (1) {
        clilen = sizeof(cli_addr);
        pipe_error = 0;
        pid = 0;
        csock = accept(lsock, 
                       (struct sockaddr *) &cli_addr, 
                       &clilen);
        if (csock < 0) {
            error("ERROR on accept");
            continue;
        }
        handler_msg("got client connection from %s\n",
                    inet_ntoa(cli_addr.sin_addr));
        /* base64 is 4 bytes for every 3
         *    20 for WS '\x00' / '\xff' and good measure  */
        dbufsize = (bufsize * 3)/4 - 20;

        handler_msg("forking handler process\n");
        pid = fork();

        if (pid == 0) {  // handler process
            ws_ctx = do_handshake(csock);
            if (ws_ctx == NULL) {
                close(csock);
                handler_msg("No connection after handshake");
                break;   // Child process exits
            }

            settings.handler(ws_ctx);
            if (pipe_error) {
                handler_emsg("Closing due to SIGPIPE\n");
            }
            close(csock);
            handler_msg("handler exit\n");
            break;   // Child process exits
        } else {         // parent process
            settings.handler_id += 1;
        }
    }

}