[Live-devel] Streaming Redirection

[Jeff Oliver]

Here's the parseTransportHeader() function....due to time constraints in 
the project Im working on and the specific use of the streamer, I've 
used functions that are probably not the best to use for portability, 
etc.  Like strtok(), no one likes using it, but for me it gets the job done.

As far as the destination parameter allowing redirection, you are 
correct, there is a security problem with that.  I would agree to not 
include that feature as part of the mainstream product, but for my 
purposes, I have the luxury of operating in a closed network AND its a 
huge benefit to be able to have a separate RTSP front-end to redirect 
streams to a pre-existing decoder client...especially for testing and 
proof-of-concept.

Jeff Oliver

static void parseTransportHeader(char const* buf,
                                 unsigned short& clientRTPPortNum,
                                 unsigned short& clientRTCPPortNum,
                                 Boolean& isMulticast,
                                 netAddressBits& destAddr,
                                 u_int8_t& destTTL)
{
    char *tmp;

    // Get multicast or unicast
    if (strstr(buf, "multicast") != NULL)
    {
        isMulticast = True;
    }
    else
    {
        isMulticast = False;
    }

    // Get Destination address
    tmp = strstr(buf, "destination=");
    if (tmp != NULL)
    {
        struct in_addr in;
        char *start;
        char *tok;

        start = strDup(tmp);

        tok = strtok(start, "=");
        tok = strtok(NULL, ";");
        if (inet_aton(tok, &in) == 0)
        {
            printf("invalid destination address\n");
        }
        destAddr = in.s_addr;
    }

    // Get the client port numbers
    tmp = strstr(buf, "client");
    if (tmp != NULL)
    {
        unsigned short p1, p2;
        if (sscanf(tmp, "client_port=%hu-%hu", &p1, &p2) == 2)
        {
            clientRTPPortNum  = p1;
            clientRTCPPortNum = p2;
        }
    }
}


Ross Finlayson wrote:

>
>> But here's a list of things I had to change to get this to work.  I 
>> think its fairly straight forward.
>> 1) I completely rewrote the parseTransportHeader to get more 
>> information.  Multicast/Unicast, Destination, TTL, Client_Port.
>
>
> Jeff,
>
> Could you post your modified "parseTransportHeader()" implementation?  
> (It looks like this could be useful.)
>
> (BTW, I just realized that there's a bug in the definition of 
> "ServerMediaSubsession::getStreamParameters()" - the 
> "destinationAddress" and "destinationTTL" parameters are supposed to 
> be 'out' parameters, so they should be passed by reference, not by 
> value.  I'll fix this in the next software release.)
>
> As an aside, note that allowing a RTSP server to transmit to an 
> arbitrary destination (as specified by the "destination" field in a 
> client's "Transport:" header) is a security risk, because it allows a 
> malicious client to launch a denial-of-service attack against an 
> unwitting victim.  (In fact, the RTSP specification discourages this 
> (see section 12.39 of RFC 2326).)  I would be very wary about 
> including support for this in a product, unless you also authenticated 
> clients in some way.
>
>
>     Ross Finlayson
>     LIVE.COM
>     <http://www.live.com/>
>
> _______________________________________________
> live-devel mailing list
> live-devel at lists.live.com
> http://lists.live.com/mailman/listinfo/live-devel
>
>


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