general/3571: Simple and effective DoS: children "reading"

[Jesus Cea <jc...@argo.es>]

>Number:         3571
>Category:       general
>Synopsis:       Simple and effective DoS: children "reading"
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    apache
>State:          open
>Class:          sw-bug
>Submitter-Id:   apache
>Arrival-Date:   Mon Dec 21 10:40:01 PST 1998
>Last-Modified:
>Originator:     jcea@argo.es
>Organization:
apache
>Release:        1.3.3
>Environment:
Solaris 2.5.1
Server: Apache/1.3.3 (Unix) PHP/3.0.5
gcc version 2.7.2
>Description:
You can have a very simple but effective Denial of Service simply opening
several connections in parallel (telnet/NetCat). Each connection move a child
to "Reading" state, disabling it until the connection is closed or timeout
arrives.

You can launch easily 10 connects per second from a dialup connection,
eating all the Apache children. The service would be dead until timeouts
expire.
>How-To-Repeat:
Simply open as many telnet connections as Apache children you had configured.
>Fix:
None correct, but possible temporal workaround):
* Limit simultaneous connections from a single IP.
* An unique dispatcher. When you have several request, serve first:
  * Older requests
  and
  * Request with the least concurrency (simultaneous requests)
>Audit-Trail:
>Unformatted:
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