Commit Graph

3 Commits

Author SHA1 Message Date
Bill Paul
a6e95b4420 Improve DoS avoidance in RPC stream oriented transports. The TCP transport
uses readtcp() to gather data from the network; readtcp() uses select(),
with a timeout of 35 seconds. The problem with this is that if you
connect to a TCP server, send two bytes of data, then just pause, the
server will remain blocked in readtcp() for up to 35 seconds, which is
sort of a long time. If you keep doing this every 35 seconds, you can
keep the server occupied indefinitely.

To fix this, I modified readtcp() (and its cousin, readunix() in svc_unix.c)
to monitor all service transport handles instead of just the current socket.
This allows the server to keep handling new connections that arrive while
readtcp() is running. This prevents one client from potentially monopolizing
a server.

Also, while I was here, I fixed a bug in the timeout calculations. Someone
attempted to adjust the timeout so that if select() returned EINTR and the
loop was restarted, the timeout would be reduced so that rather than waiting
for another 35 seconds, you could never wait for more than 35 seconds total.
Unfortunately, the calculation was wrong, and the timeout could expire much
sooner than 35 seconds.
1998-05-18 16:12:13 +00:00
Bill Paul
9c69f26836 Patch RPC library to avoid possible denial of service attacks as described
recently in BUGTRAQ. If a stream oriented transport fails to properly decode
an RPC message header structure where there should be one, it should mark
the stream as dead so that the connection will be dropped.
1998-05-15 22:53:47 +00:00
Bill Paul
e8636dfd57 Now the biggest step: import the changes to the main RPC code.
Note: you'll need to rinstalkl all your includes before compiling libc
the next time you update your sources in order for all this to work.

Reviewed by:	Mark Murray
1997-05-28 05:00:11 +00:00