Feed
askapache.com

Post Category

Post Date
Jul 02, 2008 4:42 a.m.

Article Structure
15 paragraphs
27489 characters
6 images
3 outgoing links

Sites mentioned
(click for rank details):

php.net
snoopy.sourceforge.net
wordpress.org
askapache.com

ietf.org

Next Article
Göttingen: „Schwarze Witwe“ zu lebenslanger Haft verurteilt - FOCUS Online

Previous Article
predam sonyericsson P1i - 10 500

Fsockopen Power Plays

Source: http://feeds.askapache.com/~r/apache/htaccess/~3/3...

Displaying mentions in this article, for full text please visit source.

PHP’s function fsockopen lets you open an Internet or Unix domain socket connection for connecting to a resource, and is one of the most powerful functions. fsockopen could be described as creating a direct link to the wire connected to a resource, which means you can send any information (EBCDIC, ASCII, Hex, C arrays, Raw) directly to the target server.

In unix you can send anything to the /dev/null device, for windoze think Recycle Bin, and likewise you can send anything to a socket created with fsockopen. I’ve seen fsockopen code that sends custom exploits to cisco routers, including being used by the metasploit framework. I’ve seen fsockopen telnet emulation, smtp/pop3 login, and a lot of other advanced raw networking that is exciting for me see.

A web server host listens on TCP port 80. When a client host wishes to view a resource on the web server, it establishes a TCP connection with the server host by opening a socket to send the request for the resource. When the connection is established, the client and server exchange requests and responses (respectively) until the connection is closed or aborted.

The Snoopy class is bundled with WordPress distributions and uses fsockopen to achieve most of its cool features. WordPress core, plugins, and other included files and classes also use the fsockopen function to communicate via HTTP.

Note the warning sign, fsockopen is dangerous in the sense that you can crash your server, perform a DOS against your own server or other site, use up all your servers available sockets and fd descriptors, use up your bandwidth, etc.. Shouldn’t be a problem unless you are being malicious or careless.

Here are some BOSS fsockopen functions I hacked together yesterday for use in my AskApache Crazy Cache WordPress Plugin. I’ve used code and ideas from 100’s of authors, projects, and docs to try to make this the very best I can.

This is a working example employing as many of the best-practices, tips, and tricks for using fsockopen on remote streams that I could find.

$request

$resp_headers

Fsockopen failed!'."n[".$errno."] ".$err." (".$errstr.")

If you really want to know more about fsockopen, you can do what I did and read all the relevant php source files, your OS sys, lib, and user files relevant to fsockopen, and of course you can always trace php using the fsockopen function to get an under-the-hood look at what in the world fsockopen is doing. Personally, I was trying to find more error codes and error strings to display when an fsockopen call failed, and I ended up finding over 50..

Once you save the above file on your site, you can use the strace tool to debug it. This is a tad overboard but way cool nevertheless!

strace -e trace=connect php -nef fsockopen-test.php

strace -e trace=network php -nef fsockopen-test.php

strace -q -e trace=all php -nef fsockopen-test.php

GET /wiki/Main_Page HTTP/1"..., 1300


More Fsockopen Info
TCP Multiplexing
RFC 793: To allow for many processes within a single Host to use TCP communication facilities simultaneously, the TCP provides a set of addresses or ports within each host.  Concatenated with the network and host addresses from the internet communication layer, this forms a socket.  A pair of sockets uniquely identifies each connection. That is, a socket may be simultaneously used in multiple connections.
The binding of ports to processes is handled independently by each Host.  However, it proves useful to attach frequently used processes (e.g., a “logger” or timesharing service) to fixed sockets which are made known to the public.  These services can then be accessed through the known addresses.  Establishing and learning the port addresses of other processes may involve more dynamic mechanisms.
TCP Connections
The reliability and flow control mechanisms described above require that TCPs initialize and maintain certain status information for each data stream.  The combination of this information, including sockets, sequence numbers, and window sizes, is called a connection. Each connection is uniquely specified by a pair of sockets identifying its two sides.
When two processes wish to communicate, their TCP’s must first establish a connection (initialize the status information on each side).  When their communication is complete, the connection is terminated or closed to free the resources for other uses.
Since connections must be established between unreliable hosts and over the unreliable internet communication system, a handshake mechanism with clock-based sequence numbers is used to avoid erroneous initialization of connections.
Fsockopen Practical Uses

Download Web Pages, Files, etc.
Upload a file
Send POST data to a form
Emulate cron
Download plugin updates
Scan sites for exploits
Auto Login to Google
Pass wp-nonces via cookie headers, and more

Transfer-Encoding
RFC 2068
19.4.6 Introduction of Transfer-Encoding
 
   HTTP/1.1 introduces the Transfer-Encoding header field (section
   14.40).  Proxies/gateways MUST remove any transfer coding prior to
   forwarding a message via a MIME-compliant protocol.
 
   A process for decoding the "chunked" transfer coding (section 3.6)
   can be represented in pseudo-code as:
 
          length := 0
          read chunk-size, chunk-ext (if any) and CRLF
          while (chunk-size > 0) {
             read chunk-data and CRLF
             append chunk-data to entity-body
             length := length + chunk-size
             read chunk-size and CRLF
          }
          read entity-header
          while (entity-header not empty) {
             append entity-header to existing header fields
             read entity-header
          }
          Content-Length := length
          Remove "chunked" from Transfer-Encoding

Socket-Related Man Pages

DESCRIPTION
This  manual  page  describes the Linux networking socket layer user interface. The BSD compatible sockets are the uniform interface between
the user process and the network protocol stacks in the kernel.  The protocol modules are  grouped  into  protocol  families  like  PF_INET,
PF_IPX, PF_PACKET and socket types like SOCK_STREAM or SOCK_DGRAM.  See socket(2) for more information on families and types.
 
SOCKET LAYER FUNCTIONS
These  functions  are  used by the user process to send or receive packets and to do other socket operations. For more information see their
respective manual pages.
 
socket(2) creates a socket, connect(2) connects a socket to a remote socket address, the bind(2) function binds a socket to a  local  socket
address,  listen(2)  tells  the socket that new connections shall be accepted, and accept(2) is used to get a new socket with a new incoming
connection.  socketpair(2) returns two connected anonymous sockets (only implemented for a few local families like PF_UNIX)
 
send(2), sendto(2), and sendmsg(2) send data over a socket, and recv(2), recvfrom(2), recvmsg(2) receive data from a  socket.   poll(2)  and
select(2)  wait  for  arriving  data  or a readiness to send data.  In addition, the standard I/O operations like write(2), writev(2), send-
file(2), read(2), and readv(2) can be used to read and write data.
 
getsockname(2) returns the local socket address and getpeername(2) returns the remote socket address.  getsockopt(2) and  setsockopt(2)  are
used to set or get socket layer or protocol options.  ioctl(2) can be used to set or read some other options.
 
close(2) is used to close a socket.  shutdown(2) closes parts of a full duplex socket connection.
 
Seeking, or calling pread(2) or pwrite(2) with a non-zero position is not supported on sockets.
 
It  is possible to do non-blocking IO on sockets by setting the O_NONBLOCK flag on a socket file descriptor using fcntl(2).  Then all opera-
tions that would block will (usually) return with EAGAIN (operation should be retried later); connect(2) will return EINPROGRESS error.  The
user can then wait for various events via poll(2) or select(2).

From the FreeBSD man page for socket(2)

Sockets of type SOCK_STREAM are full-duplex byte streams, similar to
pipes.  A stream socket must be in a connected state before any data may
be sent or received on it.  A connection to another socket is created
with a connect(2) system call.  Once connected, data may be transferred
using read(2) and write(2) calls or some variant of the send(2) and
recv(2) functions.  (Some protocol families, such as the Internet family,
support the notion of an ``implied connect'', which permits data to be
sent piggybacked onto a connect operation by using the sendto(2) system
call.)  When a session has been completed a close(2) may be performed.
Out-of-band data may also be transmitted as described in send(2) and
received as described in recv(2).
 
The communications protocols used to implement a SOCK_STREAM insure that
data is not lost or duplicated.  If a piece of data for which the peer
protocol has buffer space cannot be successfully transmitted within a
reasonable length of time, then the connection is considered broken and
calls will indicate an error with -1 returns and with ETIMEDOUT as the
specific code in the global variable errno.  The protocols optionally
keep sockets ``warm'' by forcing transmissions roughly every minute in
the absence of other activity.  An error is then indicated if no response
can be elicited on an otherwise idle connection for an extended period
(e.g. 5 minutes).  A SIGPIPE signal is raised if a process sends on a
broken stream; this causes naive processes, which do not handle the sig-
nal, to exit.

Random Posts

WordPress RewriteRules Viewer
What I think about DreamHost Web Hosting
.htaccess mod_rewrite rewrite examples
301 Redirect with mod_rewrite or RedirectMatch
Security Enhancing with htaccess
Getting flash to show up in front of content
Using FilesMatch and Files in htaccess
DreamHost Site of The Month Contest
LFT traceroute tool
Security with Apache htaccess Tutorial


  

Feeds and posts are not affliated with ://URLFAN.  They are displayed here simply for informational purposes, if you would like to remove your feed, posts, or domain from ranking and analysis, please contact us.