NAME¶
POE::Filter::HTTPD - parse simple HTTP requests, and serialize HTTP::Response
SYNOPSIS¶
#!perl
use warnings;
use strict;
use POE qw(Component::Server::TCP Filter::HTTPD);
use HTTP::Response;
POE::Component::Server::TCP->new(
Port => 8088,
ClientFilter => 'POE::Filter::HTTPD', ### <-- HERE WE ARE!
ClientInput => sub {
my $request = $_[ARG0];
# It's a response for the client if there was a problem.
if ($request->isa("HTTP::Response")) {
my $response = $request;
$request = $response->request;
warn "ERROR: ", $request->message if $request;
$_[HEAP]{client}->put($response);
$_[KERNEL]->yield("shutdown");
return;
}
my $request_fields = '';
$request->headers()->scan(
sub {
my ($header, $value) = @_;
$request_fields .= (
"<tr><td>$header</td><td>$value</td></tr>"
);
}
);
my $response = HTTP::Response->new(200);
$response->push_header( 'Content-type', 'text/html' );
$response->content(
"<html><head><title>Your Request</title></head>" .
"<body>Details about your request:" .
"<table border='1'>$request_fields</table>" .
"</body></html>"
);
$_[HEAP]{client}->put($response);
$_[KERNEL]->yield("shutdown");
}
);
print "Aim your browser at port 8088 of this host.\n";
POE::Kernel->run();
exit;
DESCRIPTION¶
POE::Filter::HTTPD interprets input streams as HTTP 0.9, 1.0 or 1.1 requests. It
returns a HTTP::Request objects upon successfully parsing a request.
On failure, it returns an HTTP::Response object describing the failure. The
intention is that application code will notice the HTTP::Response and send it
back without further processing. The erroneous request object is sometimes
available via the "$r->request" in HTTP::Response method. This is
illustrated in the "SYNOPSIS".
For output, POE::Filter::HTTPD accepts HTTP::Response objects and returns their
corresponding streams.
Please see HTTP::Request and HTTP::Response for details about how to use these
objects.
HTTP headers are not allowed to have UTF-8 characters; they must be ISO-8859-1.
POE::Filter::HTTPD will convert all UTF-8 into the MIME encoded equivalent. It
uses utf8::is_utf8 for detection-8 and Email::MIME::RFC2047::Encoder for
convertion. If utf8 is not installed, no conversion happens. If
Email::MIME::RFC2047::Encoder is not installed, utf8::downgrade is used
instead. In this last case, you will see a warning if you try to send UTF-8
headers.
PUBLIC FILTER METHODS¶
POE::Filter::HTTPD implements the basic POE::Filter interface.
new¶
new() accepts a list of named parameters.
"MaxBuffer" sets the maximum amount of data the filter will hold in
memory. Defaults to 512 MB (536870912 octets). Because POE::Filter::HTTPD
copies all data into memory, setting this number to high would allow a
malicious HTTPD client to fill all server memory and swap.
"MaxContent" sets the maximum size of the content of an HTTP request.
Defaults to 1 MB (1038336 octets). Because POE::Filter::HTTPD copies all data
into memory, setting this number to high would allow a malicious HTTPD client
to fill all server memory and swap. Ignored if "Streaming" is set.
"Streaming" turns on request streaming mode. Defaults to off. In
streaming mode this filter will return either an HTTP::Request object or a
block of content. The HTTP::Request object's content will return empty. The
blocks of content will be parts of the request's body, up to Content-Length in
size. You distinguish between request objects and content blocks using
"Scalar::Util/bless" (See "Streaming request" below). This
option superceeds "MaxContent".
CAVEATS¶
Some versions of libwww are known to generate invalid HTTP. For example, this
code (adapted from the HTTP::Request::Common documentation) will cause an
error in a POE::Filter::HTTPD daemon:
NOTE: Using this test with libwww-perl/5.834 showed that it added the proper
HTTP/1.1 data! We're not sure which version of LWP fixed this. This example is
valid for older LWP installations, beware!
use HTTP::Request::Common;
use LWP::UserAgent;
my $ua = LWP::UserAgent->new();
$ua->request(POST 'http://example.com', [ foo => 'bar' ]);
By default, HTTP::Request is HTTP version agnostic. It makes no attempt to add
an HTTP version header unless you specifically declare a protocol using
"$request->protocol('HTTP/1.0')".
According to the HTTP 1.0 RFC (1945), when faced with no HTTP version header,
the parser is to default to HTTP/0.9. POE::Filter::HTTPD follows this
convention. In the transaction detailed above, the Filter::HTTPD based daemon
will return a 400 error since POST is not a valid HTTP/0.9 request type.
Upon handling a request error, it is most expedient and reliable to respond with
the error and shut down the connection. Invalid HTTP requests may corrupt the
request stream. For example, the absence of a Content-Length header signals
that a request has no content. Requests with content but without that header
will be broken into a content-less request and invalid data. The invalid data
may also appear to be a request! Hilarity will ensue, possibly repeatedly,
until the filter can find the next valid request. By shutting down the
connection on the first sign of error, the client can retry its request with a
clean connection and filter.
Streaming Request¶
Normally POE::Filter::HTTPD reads the entire request content into memory before
returning the HTTP::Request to your code. In streaming mode, it will return
the content seprately, as unblessed scalars. The content may be split up into
blocks of varying sizes, depending on OS and transport constraints. Your code
can distinguish the request object from the content blocks using
"blessed" in Scalar::Util.
use Scalar::Util;
use POE::Wheel::ReadWrite;
use POE::Filter:HTTPD;
$heap->{wheel} = POE::Wheel::ReadWrite->new(
InputEvent => 'http_input',
Filter => POE::Filter::HTTPD->new( Streaming => 1 ),
# ....
);
sub http_input_handler
{
my( $heap, $req_or_data ) = @_[ HEAP, ARG0 ];
if( blessed $req_or_data ) {
my $request = $req_or_data;
if( $request->isa( 'HTTP::Response') ) {
# HTTP error
$heap->{wheel}->put( $request );
}
else {
# HTTP request
# ....
}
}
else {
my $data = $req_or_data;
# ....
}
}
You may trivally create a DoS bug if you hold all content in memory but do not
impose a maximum Content-Length. An attacker could send "Content-Length:
1099511627776" (aka 1 TB) and keep sending data until all your system's
memory and swap is filled.
Content-Length has been sanitized by POE::Filter::HTTPD so checking it is
trivial :
if( $request->headers( 'Content-Length' ) > 1024*1024 ) {
my $resp = HTTP::Response->new( RC_REQUEST_ENTITY_TOO_LARGE ),
"So much content!" )
$heap->{wheel}->put( $resp );
return;
}
If you want to handle large amounts of data, you should save the content to a
file before processing it. You still need to check Content-Length or an
attacker might fill up the partition.
use File::Temp qw(tempfile);
if( blessed $_[ARG0] ) {
$heap->{request} = $_[ARG0];
if( $heap->{request}->method eq 'GET' ) {
handle_get( $heap );
delete $heap->{request};
return;
}
my( $fh, $file ) = tempfile( "httpd-XXXXXXXX", TMPDIR=>1 );
$heap->{content_file} = $file;
$heap->{content_fh} = $fh;
$heap->{content_size} = 0;
}
else {
return unless $heap->{request};
$heap->{content_size} += length( $_[ARG0] );
$heap->{content_fh}->print( $_[ARG0] );
if( $heap->{content_size} >= $heap->{request}->headers( 'content-length' ) ) {
delete $heap->{content_fh};
delete $heap->{content_size};
# Now we can parse $heap->{content_file}
if( $heap->{request}->method eq 'POST' ) {
handle_post( $heap );
}
else {
# error ...
}
}
}
sub handle_post
{
my( $heap ) = @_;
# Now we have to load and parse $heap->{content_file}
# Next 6 lines make the data available to CGI->init
local $ENV{REQUEST_METHOD} = 'POST';
local $CGI::PERLEX = $CGI::PERLEX = "CGI-PerlEx/Fake";
local $ENV{CONTENT_TYPE} = $heap->{req}->header( 'content-type' );
local $ENV{CONTENT_LENGTH} = $heap->{req}->header( 'content-length' );
my $keep = IO::File->new( "<&STDIN" ) or die "Unable to reopen STDIN: $!";
open STDIN, "<$heap->{content_file}" or die "Reopening STDIN failed: $!";
my $qcgi = CGI->new();
# cleanup
open STDIN, "<&".$keep->fileno or die "Unable to reopen $keep: $!";
undef $keep;
unlink delete $heap->{content_file};
# now use $q as you would normaly
my $file = $q->upload( 'field_name' );
# ....
}
sub handle_get
{
my( $heap ) = @_;
# 4 lines to get data into CGI->init
local $ENV{REQUEST_METHOD} = 'GET';
local $CGI::PERLEX = $CGI::PERLEX = "CGI-PerlEx/Fake";
local $ENV{CONTENT_TYPE} = $heap->{req}->header( 'content-type' );
local $ENV{'QUERY_STRING'} = $heap->{req}->uri->query;
my $q = CGI->new();
# now use $q as you would normaly
# ....
}
Streaming Response¶
It is possible to use POE::Filter::HTTPD for streaming content, but an
application can use it to send headers and then switch to POE::Filter::Stream.
From the input handler (the InputEvent handler if you're using wheels, or the
ClientInput handler for POE::Component::Server::TCP):
my $response = HTTP::Response->new(200);
$response->push_header('Content-type', 'audio/x-mpeg');
$_[HEAP]{client}->put($response);
$_[HEAP]{client}->set_output_filter(POE::Filter::Stream->new());
Then the output-flushed handler (FlushEvent for POE::Wheel::ReadWrite, or
ClientFlushed for POE::Component::Server::TCP) can
put() chunks of the
stream as needed.
my $bytes_read = sysread(
$_[HEAP]{file_to_stream}, my $buffer = '', 4096
);
if ($bytes_read) {
$_[HEAP]{client}->put($buffer);
}
else {
delete $_[HEAP]{file_to_stream};
$_[KERNEL]->yield("shutdown");
}
SEE ALSO¶
Please see POE::Filter for documentation regarding the base interface.
The SEE ALSO section in POE contains a table of contents covering the entire POE
distribution.
HTTP::Request and HTTP::Response explain all the wonderful things you can do
with these classes.
BUGS¶
Many aspects of HTTP 1.0 and higher are not supported, such as keep-alive. A
simple I/O filter can't support keep-alive, for example. A number of more
feature-rich POE HTTP servers are on the CPAN. See
<
http://search.cpan.org/search?query=POE+http+server&mode=dist>
AUTHORS & COPYRIGHTS¶
POE::Filter::HTTPD was contributed by Artur Bergman. Documentation is provided
by Rocco Caputo.
Please see POE for more information about authors and contributors.