[lwip-devel] [bug #36300] PPP CHAP stack requirements reduction

[Sylvain Rochet]

URL:
  <http://savannah.nongnu.org/bugs/?36300>

                 Summary: PPP CHAP stack requirements reduction
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: gradator
            Submitted on: Wed 25 Apr 2012 01:02:35 PM GMT
                Category: None
                Severity: 3 - Normal
              Item Group: Change Request
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 
            lwIP version: CVS Head

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Details:

The current PPP CHAP implementation requires a lot of stack memory, let's say,
about 1 KiB stack memory is required to complete the challenge:

static void ChapReceiveResponse(...) {
  ...
  char secret[MAXSECRETLEN]; // 256
  char rhostname[256];
  MD5_CTX mdContext; // 64+16+4*4+2*4 = 104

static void ChapSendResponse(...) {
  ...
  char msg[256]; /* @todo: this can be a char*, no strcpy needed */

This can be an issue with system without much memory, if Ethernet input is
done through a thread that call ethernet_input() from etharp.c, then this
thread is going to require about 1 KiB of static stack size only necessary for
CHAP, which is only used from time to time (ideally, only one time).

Here is a patch that use mem_malloc() and mem_free() for heavy CHAP
authentication data, so that it use memory from the mem/packet pool and
doesn't waste memory.

It also uses the MAXNAMELEN define instead of the literal 256 there and
there.

Sylvain



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File Attachments:


-------------------------------------------------------
Date: Wed 25 Apr 2012 01:02:35 PM GMT  Name: chap-less-stack-memory.patch 
Size: 8kB   By: gradator

<http://savannah.nongnu.org/bugs/download.php?file_id=25731>

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