Bug 77724

Description of Problem:

(Rated this security because it indicates some problem with
tcpwrappers access to tftpd - I have no evidence that an actual
security hole exists.)

When a remote host which is denied access to tftpd by
/etc/hosts.allow, /etc/hosts.deny AND the /etc/xinetd.d/tftp
file attempts to tftp a file off the server it results in
hundreds of messages on the server's /var/log/secure like this:

Nov 12 08:37:00 safserver xinetd[15800]: START:
    tftp pid=23419 from=xxx.xxx.xxx.xxx
Nov 12 08:37:00 safserver xinetd[23419]: FAIL:
    tftp address from=xxx.xxx.xxx.xxx

eventually xinetd kills the tftpd server and restarts it several seconds
later. 

None of this should happen - tftpd access is denied so xinetd should
never even try to start tftpd.  At worst a single "connection rejected"
should show up somewhere.  Instead it seems to try to start it hundreds
of times and only then does it catch the tcpwrappers limit.

Also, in some instances, this throws xinetd into an odd state where it
uses about 3% of the CPU.  However, it must be interrupting or something,
because the server machine slows to a crawl. Restarting xinetd fixes this.

Connections from machines allowed by tcpwrappers work properly and do
not seem to throw xinetd for a loop.

Version-Release number of selected component (if applicable):
xinetd-2.3.9-0.73
RH 7.3
Kernel  2.4.18-10smp
Tyan 2468UGN dual Athlon motherboard

How Reproducible:
The hundreds of messages and tftpd kill/restart: 100%
The CPU crawling problem:  not very,  maybe 5% of the time


Steps to Reproduce:
1. Set up /etc/xinetd.d/tftp like this:

service tftp
{
        disable = no
        socket_type             = dgram
        protocol                = udp
        wait                    = yes
        user                    = root
        server                  = /usr/sbin/in.tftpd
        server_args             = -s /tftpboot
        only_from               = 192.168.1.0
        log_on_success          += HOST
        log_on_failure          += HOST
        per_source              = 11
        cps                     = 100 2
}


2. echo "blah blah" > /tftpboot/message.txt
3. deny all access to a test node (for everything) in /etc/hosts.allow,
   /etc/hosts.deny.  Simplest case:
   % echo "ALL:ALL" >/etc/hosts.deny
   % echo "#empty"  >/etc/hosts.allow
4. from test node use tftp to connect to server and issue command:
   get message.txt

Actual Results:
File is not retrieved.  (correct).  On server  a zillion log messages
appear in /var/log/secure and xinetd may go into the high CPU usage
state (not correct).


Expected Results:
File not retrieved, one "rejected connection" type of log message.


Additional Information: