secihttp HTTP logging and information retrieval tool

		 Copyright (c) 2015-2015 zhulinu<zhulinu@163.com>

       For modification and redistribution information, see COPYING file

在httpry基础上进行了修改，httpry的授权协议为GNU GENERAL PUBLIC LICENSE Version 2, June 1991
不知道应该如何描述此文件，所以用中文做了描述，依然遵循授权协议GNU GENERAL PUBLIC LICENSE Version 2, June 1991
增加了发送syslog审计记录。

add -g output syslog mode 
--{ ABOUT }--

secihttp is a tool designed for displaying and logging HTTP traffic. It is not
intended to perform analysis itself, but instead to capture, parse and/or
log the traffic for later analysis. It can be run in real-time displaying
the live traffic on the wire, or as a daemon process that logs to an output
file. It is written to be as lightweight and flexible as possible, so that
it can be easily adaptable to different applications. It does not display
the raw HTTP data transferred, but instead focuses on parsing and displaying
the request/response line along with associated header fields.

"How is this tool useful?" you may ask. Here's just a few ideas:

 > See what users on your network are browsing online
 > Check for proper server configuration (or improper, as the case may be)
 > Research patterns in HTTP usage
 > Watch for dangerous downloaded files
 > Verify the enforcement of HTTP policy on your network
 > Extract HTTP statistics out of saved capture files
 > It's just plain fun to watch in realtime

In addition to the core program, there are several Perl scripts included
for processing secihttp log files. They should be useful for a number of
generic situations, and can serve as a useful starting point for your own
log parsing toolset. More information about these scripts can be found in
the doc/perl-tools file.


--{ INSTALLATION }--

secihttp should compile on almost any *nix based OS with a relatively recent
version of libpcap (specifically tested against 1.1.1 and newer). To compile
and install, run these commands in the base secihttp directory:

 $ make
 # make install

which compiles the program and copies the binary and man page to their
appropriate locations. You can run the binary from the compilation directory
if you don't want to install it. To uninstall the program, run:

 # make uninstall

from the installation directory, or manually delete the executable and man
page.


--{ USAGE }--

Running secihttp with no options will cause it to listen on the first network
device and output to the console with some sane defaults. The -h switch will
print out an abbreviated description of the available options to change the
defaults. This section describes these options in greater detail.

secihttp [ -dFhpqs ] [ -b file ] [ -f format ] [ -i device ] [ -l threshold ]
       [ -m methods ] [ -n count ] [ -o file ] [ -P file ] [ -r file ]
       [ -S bytes ] [ -t seconds ] [ -u user ] [ 'expression' ]

-b file
Write all processed HTTP packets to a binary pcap dump file. Useful for
further analysis of logged data.

-d
Run the program as a daemon process. All program status output will be sent
to syslog. A pid file is created for the process in /var/run/secihttp.pid by
default. Requires an output file specified with -o.

-f format
Provide a comma-delimited string specifying the parsed HTTP data to output.
See the doc/format-string file for further information regarding available
options and syntax.

-F
Disable all output buffering. This may be helpful when piping secihttp output
into another program.

-h
Display a brief summary of these options.

-i device
Specify an ethernet interface for the program to listen on. If not specified,
the program will poll the system for a list of interfaces and select the
first one found.

-l threshold
Specify a requests per second rate threshold value when running in rate
statistics mode (-s). Only hosts with a rps value greater than or equal to
this number will be displayed. Defaults to 1.

-m methods
Provide a comma-delimited string that specifies the request methods to parse.
The program defaults to parsing all of the standard RFC2616 method strings if
this option is not set. See the doc/method-string file for more information.

-n count
Parse this number of HTTP packets and then exit. Defaults to 0, which means
loop forever.

-o file
Specify an output file for writing parsed packet data.

-p
Do not put the NIC in promiscuous mode on startup. Note that the NIC could
already be in that mode for another reason.

-P file
Specify a path and filename for creating the PID file in daemon mode.

-q
Suppress non-critical output (startup banner, statistics, etc.).

-r file
Provide an input capture file to read from instead of performing
a live capture. This option does not require root privileges.

-s
Run secihttp in an HTTP request per second display mode. This periodically
displays the rate per active host and total rate at a specified interval.

-S
Specify a number of bytes to skip in the ethernet header. This allows for
custom header offsets to be accounted for.

-t seconds
Specify the host statistics display interval in seconds when running in
rate statistics mode (-s). Defaults to 5 seconds.

-u user
Specify an alternate user to take ownership of the process and any output
files. You will need root privileges to do this; it will switch to the new
user after initialization.

-g
output syslog

'expression'
Specify a bpf-style capture filter, overriding the default. Here are a few
basic examples, starting with the default filter:

 'tcp port 80 or 8080'
 'tcp dst port 80'
 'tcp dst port 80 and src host 192.168.1.1'

These filters will capture all web traffic both directions on two common
ports, capture only requests made to port 80, and capture requests to port
80 by a particular host, respectively. See 'man tcpdump' for further
information on the syntax and available primitives.


--{ KNOWN ISSUES }--

It is worth noting that secihttp is rather naive when it comes to parsing HTTP
packets. It does not perform any reordering or reassembly of packets and
simply searches the start of each packet for HTTP data and ignores the packet
if it does not find valid data. HTTP packets that are fragmented within the
request/response line will be parsed to the end of the packet and any header
data present in subsequent packets will not be parsed.