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HTTP Handlers | |
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Home / Documentation / 2.0 / User's guide / | |
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HTTP Handlers | |
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Embedding Perl in HTML with Mason
By Dave Rolsky, Ken Williams |
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The mod_perl Developer's Cookbook
By Geoffrey Young, Paul Lindner, Randy Kobes |
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mod_perl Pocket Reference
By Andrew Ford |
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Writing Apache Modules with Perl and C
By Lincoln Stein, Doug MacEachern |
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All HTTP Request handlers have the following structure:
package MyApache2::MyHandlerName;
# load modules that are going to be used
use ...;
# compile (or import) constants
use Apache2::Const -compile => qw(OK);
sub handler {
my $r = shift;
# handler code comes here
return Apache2::Const::OK; # or another status constant
}
1;
First, the package is declared. Next, the modules that are going to be used are loaded and constants compiled.
The handler itself coming next and usually it receives the only
argument: the
Apache2::RequestRec object.
If the handler is declared as a method handler :
sub handler : method {
my ($class, $r) = @_;
the handler receives two arguments: the class name and the
Apache2::RequestRec object.
The handler ends with a return code and the file
is ended with 1; to return true when it gets loaded.
Those familiar with mod_perl 1.0 will find the HTTP request cycle in mod_perl 2.0 to be almost identical to the mod_perl 1.0's model. The different things are:
a new directive PerlMapToStorageHandler
was added to match the new phase map_to_storage added by Apache
2.0.
the PerlHandler directive has been renamed to
PerlResponseHandler to better match the corresponding Apache phase
name (response).
the response phase now includes filtering.
The following diagram depicts the HTTP request life cycle and highlights which handlers are available to mod_perl 2.0:
From the diagram it can be seen that an HTTP request is processed by 12 phases, executed in the following order:
It's possible that the cycle will not be completed if any of the
phases terminates it, usually when an error happens. In that case
Apache skips to the logging phase (mod_perl executes all registered
PerlLogHandler handlers) and finally the cleanup phase happens.
Notice that when the response handler is reading the input data it can be filtered through request input filters, which are preceded by connection input filters if any. Similarly the generated response is first run through request output filters and eventually through connection output filters before it's sent to the client. We will talk about filters in detail later in the dedicated to filters chapter.
Before discussing each handler in detail remember that if you use
the stacked handlers feature all
handlers in the chain will be run as long as they return Apache2::Const::OK
or Apache2::Const::DECLINED. Because stacked handlers is a special case. So
don't be surprised if you've returned Apache2::Const::OK and the next
handler was still executed. This is a feature, not a bug.
Now let's discuss each of the mentioned handlers in detail.
The post_read_request phase is the first request phase and happens immediately after the request has been read and HTTP headers were parsed.
This phase is usually used to do processing that must happen once per
request. For example Apache2::Reload is usually invoked at this
phase to reload modified Perl modules.
This phase is of type
RUN_ALL.
The handler's configuration scope is
SRV, because at this
phase the request has not yet been associated with a particular
filename or directory.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
Now, let's look at an example. Consider the following registry script:
#file:touch.pl
#-------------
use strict;
use warnings;
use Apache2::ServerUtil ();
use Apache2::RequestIO ();
use File::Spec::Functions qw(catfile);
my $r = shift;
$r->content_type('text/plain');
my $conf_file = catfile Apache2::ServerUtil::server_root,
"conf", "httpd.conf";
printf "$conf_file is %0.2f minutes old\n", 60*24*(-M $conf_file);
This registry script is supposed to print when the last time httpd.conf has been modified, compared to the start of the request process time. If you run this script several times you might be surprised that it reports the same value all the time. Unless the request happens to be served by a recently started child process which will then report a different value. But most of the time the value won't be reported correctly.
This happens because the -M operator reports the difference between
file's modification time and the value of a special Perl variable
$^T. When we run scripts from the command line, this variable is
always set to the time when the script gets invoked. Under mod_perl
this variable is getting preset once when the child process starts and
doesn't change since then, so all requests see the same time, when
operators like -M, -C and -A are used.
Armed with this knowledge, in order to make our code behave similarly
to the command line programs we need to reset $^T to the request's
start time, before -M is used. We can change the script itself, but
what if we need to do the same change for several other scripts and
handlers? A simple PerlPostReadRequestHandler handler, which will
be executed as the very first thing of each requests, comes handy
here:
#file:MyApache2/TimeReset.pm
#--------------------------
package MyApache2::TimeReset;
use strict;
use warnings;
use Apache2::RequestRec ();
use Apache2::Const -compile => 'OK';
sub handler {
my $r = shift;
$^T = $r->request_time;
return Apache2::Const::OK;
}
1;
We could do:
$^T = time();
But to make things more efficient we use $r->request_time since
the request object $r already stores the request's start time, so
we get it without performing an additional system call.
To enable it just add to httpd.conf:
PerlPostReadRequestHandler MyApache2::TimeReset
either to the global section, or to the <VirtualHost>
section if you want this handler to be run only for a specific virtual
host.
The translate phase is used to perform the manipulation of a
request's URI. If no custom handler is provided, the server's standard
translation rules (e.g., Alias directives, mod_rewrite, etc.) will
be used. A PerlTransHandler handler can alter the default
translation mechanism or completely override it. This is also a good
place to register new handlers for the following phases based on the
URI. PerlMapToStorageHandler is to be
used to override the URI to filename translation.
This phase is of type
RUN_FIRST.
The handler's configuration scope is
SRV, because at this
phase the request has not yet been associated with a particular
filename or directory.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
There are many useful things that can be performed at this stage. Let's look at the example handler that rewrites request URIs, similar to what mod_rewrite does. For example, if your web-site was originally made of static pages, and now you have moved to a dynamic page generation chances are that you don't want to change the old URIs, because you don't want to break links for those who link to your site. If the URI:
http://example.com/news/20021031/09/index.html
is now handled by:
http://example.com/perl/news.pl?date=20021031;id=09;page=index.html
the following handler can do the rewriting work transparent to news.pl, so you can still use the former URI mapping:
#file:MyApache2/RewriteURI.pm
#---------------------------
package MyApache2::RewriteURI;
use strict;
use warnings;
use Apache2::RequestRec ();
use Apache2::Const -compile => qw(DECLINED);
sub handler {
my $r = shift;
my ($date, $id, $page) = $r->uri =~ m|^/news/(\d+)/(\d+)/(.*)|;
$r->uri("/perl/news.pl");
$r->args("date=$date;id=$id;page=$page");
return Apache2::Const::DECLINED;
}
1;
The handler matches the URI and assigns a new URI via $r->uri()
and the query string via $r->args(). It then returns
Apache2::Const::DECLINED, so the next translation handler will get
invoked, if more rewrites and translations are needed.
Of course if you need to do a more complicated rewriting, this handler can be easily adjusted to do so.
To configure this module simply add to httpd.conf:
PerlTransHandler +MyApache2::RewriteURI
The map_to_storage phase is used to perform the translation of a request's URI into a corresponding filename. If no custom handler is provided, the server will try to walk the filesystem trying to find what file or directory corresponds to the request's URI. Since usually mod_perl handler don't have corresponding files on the filesystem, you will want to shortcut this phase and save quite a few CPU cycles.
This phase is of type
RUN_FIRST.
The handler's configuration scope is
SRV, because at this
phase the request has not yet been associated with a particular
filename or directory.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
For example if you don't want Apache to try to attempt to translate URI into a filename, just add a handler:
PerlMapToStorageHandler MyApache2::NoTranslation
using the following code:
#file:MyApache2/NoTranslation.pm
#------------------------------
package MyApache2::NoTranslation;
use strict;
use warnings FATAL => 'all';
use Apache2::Const -compile => qw(OK);
sub handler {
my $r = shift;
# skip ap_directory_walk stat() calls
return Apache2::Const::OK;
}
1;
But this can be done from httpd.conf too!
PerlMapToStorageHandler Apache2::Const::OK
If you haven't already compiled Apache2::Const::OK elsewhere, you
should add:
<Perl>
use Apache2::Const -compile => qw(OK);
</Perl>
Apache also uses this phase to handle TRACE requests. So if you
shortcut it, TRACE calls will be not handled. In case you need to
handle such, you may rewrite it as:
#file:MyApache2/NoTranslation2.pm
#-------------------------------
package MyApache2::NoTranslation2;
use strict;
use warnings FATAL => 'all';
use Apache2::RequestRec ();
use Apache2::Const -compile => qw(DECLINED OK M_TRACE);
sub handler {
my $r = shift;
return Apache2::Const::DECLINED
if $r->method_number == Apache2::Const::M_TRACE;
# skip ap_directory_walk stat() calls
return Apache2::Const::OK;
}
1;
BTW, the HTTP TRACE method asks a web server to echo the contents of the request back to the client for debugging purposes. i.e., the complete request, including HTTP headers, is returned in the entity-body of a TRACE response. Attackers may abuse HTTP TRACE functionality to gain access to information in HTTP headers such as cookies and authentication data. In the presence of other cross-domain vulnerabilities in web browsers, sensitive header information could be read from any domains that support the HTTP TRACE method.
Another way to prevent the core translation is to set
$r->filename() to some value, which can also be done in the
PerlTransHandler, if you are already using it.
The header_parser phase is the first phase to happen after the
request has been mapped to its <Location> (or an equivalent
container). At this phase the handler can examine the request headers
and to take a special action based on these. For example this phase
can be used to block evil clients targeting certain resources, while
little resources were wasted so far.
This phase is of type
RUN_ALL.
The handler's configuration scope is
DIR.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
This phase is very similar to
PerlPostReadRequestHandler, with the
only difference that it's run after the request has been mapped to the
resource. Both phases are useful for doing something once per request,
as early as possible. And usually you can take any
PerlPostReadRequestHandler and turn
it into PerlHeaderParserHandler by
simply changing the directive name in httpd.conf and moving it
inside the container where it should be executed. Moreover, because of
this similarity mod_perl provides a special directive
PerlInitHandler which if found outside resource
containers behaves as
PerlPostReadRequestHandler,
otherwise as PerlHeaderParserHandler.
You already know that Apache handles the HEAD, GET, POST and
several other HTTP methods. But did you know that you can invent your
own HTTP method as long as there is a client that supports it. If you
think of emails, they are very similar to HTTP messages: they have a
set of headers and a body, sometimes a multi-part body. Therefore we
can develop a handler that extends HTTP by adding a support for the
EMAIL method. We can enable this protocol extension and push the
real content handler during the
PerlHeaderParserHandler phase:
<Location /email>
PerlHeaderParserHandler MyApache2::SendEmail
</Location>
and here is the MyApache2::SendEmail handler:
#file:MyApache2/SendEmail.pm
#--------------------------
package MyApache2::SendEmail;
use strict;
use warnings;
use Apache2::RequestRec ();
use Apache2::RequestIO ();
use Apache2::RequestUtil ();
use Apache2::ServerUtil ();
use Apache2::ServerRec ();
use Apache2::Process ();
use APR::Table ();
use Apache2::Const -compile => qw(DECLINED OK);
use constant METHOD => 'EMAIL';
use constant SMTP_HOSTNAME => "localhost";
sub handler {
my $r = shift;
return Apache2::Const::DECLINED unless $r->method eq METHOD;
$r->server->method_register(METHOD);
$r->handler("perl-script");
$r->push_handlers(PerlResponseHandler => \&send_email_handler);
return Apache2::Const::OK;
}
sub send_email_handler {
my $r = shift;
my %headers = map {$_ => $r->headers_in->get($_)}
qw(To From Subject);
my $content = content($r);
my $status = send_email(\%headers, \$content);
$r->content_type('text/plain');
$r->print($status ? "ACK" : "NACK");
return Apache2::Const::OK;
}
sub send_email {
my ($rh_headers, $r_body) = @_;
require MIME::Lite;
MIME::Lite->send("smtp", SMTP_HOSTNAME, Timeout => 60);
my $msg = MIME::Lite->new(%$rh_headers, Data => $$r_body);
#warn $msg->as_string;
$msg->send;
}
use APR::Brigade ();
use APR::Bucket ();
use Apache2::Const -compile => qw(MODE_READBYTES);
use APR::Const -compile => qw(SUCCESS BLOCK_READ);
use constant IOBUFSIZE => 8192;
sub content {
my $r = shift;
my $bb = APR::Brigade->new($r->pool, $r->connection->bucket_alloc);
my $data = '';
my $seen_eos = 0;
do {
$r->input_filters->get_brigade($bb,
Apache2::Const::MODE_READBYTES,
APR::Const::BLOCK_READ, IOBUFSIZE);
for (my $b = $bb->first; $b; $b = $bb->next($b)) {
if ($b->is_eos) {
$seen_eos++;
last;
}
if ($b->read(my $buf)) {
$data .= $buf;
}
$b->remove; # optimization to reuse memory
}
} while (!$seen_eos);
$bb->destroy;
return $data;
}
1;
Let's get the less interesting code out of the way. The function
content() grabs the request body. The function send_email() sends the
email over SMTP. You should adjust the constant SMTP_HOSTNAME to
point to your outgoing SMTP server. You can replace this function with
your own if you prefer to use a different method to send email.
Now to the more interesting functions. The function handler()
returns immediately and passes the control to the next handler if the
request method is not equal to EMAIL (set in the METHOD
constant):
return Apache2::Const::DECLINED unless $r->method eq METHOD;
Next it tells Apache that this new method is a valid one and that the
perl-script handler will do the processing.
$r->server->method_register(METHOD);
$r->handler("perl-script");
Finally it pushes the function send_email_handler() to the
PerlResponseHandler list of handlers:
$r->push_handlers(PerlResponseHandler => \&send_email_handler);
The function terminates the header_parser phase by:
return Apache2::Const::OK;
All other phases run as usual, so you can reuse any HTTP protocol hooks, such as authentication and fixup phases.
When the response phase starts send_email_handler() is invoked,
assuming that no other response handlers were inserted before it. The
response handler consists of three parts. Retrieve the email headers
To, From and Subject, and the body of the message:
my %headers = map {$_ => $r->headers_in->get($_)}
qw(To From Subject);
my $content = $r->content;
Then send the email:
my $status = send_email(\%headers, \$content);
Finally return to the client a simple response acknowledging that
email has been sent and finish the response phase by returning
Apache2::Const::OK:
$r->content_type('text/plain');
$r->print($status ? "ACK" : "NACK");
return Apache2::Const::OK;
Of course you will want to add extra validations if you want to use this code in production. This is just a proof of concept implementation.
As already mentioned when you extend an HTTP protocol you need to have
a client that knows how to use the extension. So here is a simple
client that uses LWP::UserAgent to issue an EMAIL method request
over HTTP protocol:
#file:send_http_email.pl
#-----------------------
#!/usr/bin/perl
use strict;
use warnings;
require LWP::UserAgent;
my $url = "http://localhost:8000/email/";
my %headers = (
From => 'example@example.com',
To => 'example@example.com',
Subject => '3 weeks in Tibet',
);
my $content = <<EOI;
I didn't have an email software,
but could use HTTP so I'm sending it over HTTP
EOI
my $headers = HTTP::Headers->new(%headers);
my $req = HTTP::Request->new("EMAIL", $url, $headers, $content);
my $res = LWP::UserAgent->new->request($req);
print $res->is_success ? $res->content : "failed";
most of the code is just a custom data. The code that does something
consists of four lines at the very end. Create HTTP::Headers and
HTTP::Request object. Issue the request and get the
response. Finally print the response's content if it was successful or
just "failed" if not.
Now save the client code in the file send_http_email.pl, adjust the To field, make the file executable and execute it, after you have restarted the server. You should receive an email shortly to the address set in the To field.
When configured inside any container directive, except
<VirtualHost>, this handler is an alias for
PerlHeaderParserHandler described
earlier. Otherwise it acts as an alias for
PerlPostReadRequestHandler described
earlier.
It is the first handler to be invoked when serving a request.
This phase is of type
RUN_ALL.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
The best example here would be to use
Apache2::Reload which takes the
benefit of this directive. Usually
Apache2::Reload is configured
as:
PerlInitHandler Apache2::Reload PerlSetVar ReloadAll Off PerlSetVar ReloadModules "MyApache2::*"
which during the current HTTP request will monitor and reload all
MyApache2::* modules that have been modified since the last HTTP
request. However if we move the global configuration into a
<Location> container:
<Location /devel>
PerlInitHandler Apache2::Reload
PerlSetVar ReloadAll Off
PerlSetVar ReloadModules "MyApache2::*"
SetHandler perl-script
PerlResponseHandler ModPerl::Registry
Options +ExecCGI
</Location>
Apache2::Reload will reload the
modified modules, only when a request to the /devel namespace is
issued, because PerlInitHandler plays the role
of PerlHeaderParserHandler here.
The access_checker phase is the first of three handlers that are involved in what's known as AAA: Authentication, Authorization, and Access control.
This phase can be used to restrict access from a certain IP address, time of the day or any other rule not connected to the user's identity.
This phase is of type
RUN_ALL.
The handler's configuration scope is
DIR.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
The concept behind access checker handler is very simple, return
Apache2::Const::FORBIDDEN if the access is not allowed, otherwise
return Apache2::Const::OK.
The following example handler denies requests made from IPs on the blacklist.
#file:MyApache2/BlockByIP.pm
#--------------------------
package MyApache2::BlockByIP;
use strict;
use warnings;
use Apache2::RequestRec ();
use Apache2::Connection ();
use Apache2::Const -compile => qw(FORBIDDEN OK);
my %bad_ips = map {$_ => 1} qw(127.0.0.1 10.0.0.4);
sub handler {
my $r = shift;
return exists $bad_ips{$r->connection->remote_ip}
? Apache2::Const::FORBIDDEN
: Apache2::Const::OK;
}
1;
The handler retrieves the connection's IP address, looks it up in the hash of blacklisted IPs and forbids the access if found. If the IP is not blacklisted, the handler returns control to the next access checker handler, which may still block the access based on a different rule.
To enable the handler simply add it to the container that needs to be protected. For example to protect an access to the registry scripts executed from the base location /perl add:
<Location /perl/>
SetHandler perl-script
PerlResponseHandler ModPerl::Registry
PerlAccessHandler MyApache2::BlockByIP
Options +ExecCGI
</Location>
It's important to notice that PerlAccessHandler can be configured
for any subsection of the site, no matter whether it's served by a
mod_perl response handler or not. For example to run the handler from
our example for all requests to the server simply add to
httpd.conf:
<Location />
PerlAccessHandler MyApache2::BlockByIP
</Location>
The check_user_id (authen) phase is called whenever the
requested file or directory is password protected. This, in turn,
requires that the directory be associated with AuthName,
AuthType and at least one require directive.
This phase is usually used to verify a user's identification
credentials. If the credentials are verified to be correct, the
handler should return Apache2::Const::OK. Otherwise the handler
returns Apache2::Const::HTTP_UNAUTHORIZED to indicate that the user
has not authenticated successfully. When Apache sends the HTTP header
with this code, the browser will normally pop up a dialog box that
prompts the user for login information.
This phase is of type
RUN_FIRST.
The handler's configuration scope is
DIR.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
The following handler authenticates users by asking for a username and
a password and lets them in only if the length of a string made from
the supplied username and password and a single space equals to the
secret length, specified by the constant SECRET_LENGTH.
#file:MyApache2/SecretLengthAuth.pm
#---------------------------------
package MyApache2::SecretLengthAuth;
use strict;
use warnings;
use Apache2::Access ();
use Apache2::RequestUtil ();
use Apache2::Const -compile => qw(OK DECLINED HTTP_UNAUTHORIZED);
use constant SECRET_LENGTH => 14;
sub handler {
my $r = shift;
my ($status, $password) = $r->get_basic_auth_pw;
return $status unless $status == Apache2::Const::OK;
return Apache2::Const::OK
if SECRET_LENGTH == length join " ", $r->user, $password;
$r->note_basic_auth_failure;
return Apache2::Const::HTTP_UNAUTHORIZED;
}
1;
First the handler retrieves the status of the authentication and the
password in plain text. The status will be set to
Apache2::Const::OK only when the user has supplied the username and
the password credentials. If the status is different, we just let
Apache handle this situation for us, which will usually challenge the
client so it'll supply the credentials.
Note that get_basic_auth_pw() does a few things behind the scenes,
which are important to understand if you plan on implementing your own
authentication mechanism that does not use get_basic_auth_pw().
First, is checks the value of the configured AuthType for the
request, making sure it is Basic. Then it makes sure that the
Authorization (or Proxy-Authorization) header is formatted for
Basic authentication. Finally, after isolating the user and
password from the header, it populates the ap_auth_type slot in the
request record with Basic. For the first and last parts of this
process, mod_perl offers an API. $r->auth_type returns the
configured authentication type for the current request - whatever was
set via the AuthType configuration directive.
$r->ap_auth_type populates the ap_auth_type slot in the
request record, which should be done after it has been confirmed that
the request is indeed using Basic authentication. (Note:
$r->ap_auth_type was $r->connection->auth_type in
the mod_perl 1.0 API.)
Once we know that we have the username and the password supplied by
the client, we can proceed with the authentication. Our authentication
algorithm is unusual. Instead of validating the username/password pair
against a password file, we simply check that the string built from
these two items plus a single space is SECRET_LENGTH long (14 in
our example). So for example the pair mod_perl/rules authenticates
correctly, whereas secret/password does not, because the latter
pair will make a string of 15 characters. Of course this is not a
strong authentication scheme and you shouldn't use it for serious
things, but it's fun to play with. Most authentication validations
simply verify the username/password against a database of valid pairs,
usually this requires the password to be encrypted first, since
storing passwords in clear is a bad idea.
Finally if our authentication fails the handler calls
note_basic_auth_failure() and returns
Apache2::Const::HTTP_UNAUTHORIZED, which sets the proper HTTP
response headers that tell the client that its user that the
authentication has failed and the credentials should be supplied
again.
It's not enough to enable this handler for the authentication to
work. You have to tell Apache what authentication scheme to use
(Basic or Digest), which is specified by the AuthType
directive, and you should also supply the AuthName -- the
authentication realm, which is really just a string that the client
usually uses as a title in the pop-up box, where the username and the
password are inserted. Finally the Require directive is needed to
specify which usernames are allowed to authenticate. If you set it to
valid-user any username will do.
Here is the whole configuration section that requires users to authenticate before they are allowed to run the registry scripts from /perl/:
<Location /perl/>
SetHandler perl-script
PerlResponseHandler ModPerl::Registry
PerlAuthenHandler MyApache2::SecretLengthAuth
Options +ExecCGI
AuthType Basic
AuthName "The Gate"
Require valid-user
</Location>
Just like PerlAccessHandler and other mod_perl handlers,
PerlAuthenHandler can be configured for any subsection of the site,
no matter whether it's served by a mod_perl response handler or
not. For example to use the authentication handler from the last
example for any requests to the site, simply use:
<Location />
PerlAuthenHandler MyApache2::SecretLengthAuth
AuthType Basic
AuthName "The Gate"
Require valid-user
</Location>
The auth_checker (authz) phase is used for authorization control. This phase requires a successful authentication from the previous phase, because a username is needed in order to decide whether a user is authorized to access the requested resource.
As this phase is tightly connected to the authentication phase, the
handlers registered for this phase are only called when the requested
resource is password protected, similar to the auth phase. The handler
is expected to return Apache2::Const::DECLINED to defer the
decision, Apache2::Const::OK to indicate its acceptance of the
user's authorization, or Apache2::Const::HTTP_UNAUTHORIZED to
indicate that the user is not authorized to access the requested
document.
This phase is of type
RUN_FIRST.
The handler's configuration scope is
DIR.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
Here is the MyApache2::SecretResourceAuthz handler which grants
access to certain resources only to certain users who have already
properly authenticated:
#file:MyApache2/SecretResourceAuthz.pm
#------------------------------------
package MyApache2::SecretResourceAuthz;
use strict;
use warnings;
use Apache2::Access ();
use Apache2::RequestUtil ();
use Apache2::Const -compile => qw(OK HTTP_UNAUTHORIZED);
my %protected = (
'admin' => ['stas'],
'report' => [qw(stas boss)],
);
sub handler {
my $r = shift;
my $user = $r->user;
if ($user) {
my ($section) = $r->uri =~ m|^/company/(\w+)/|;
if (defined $section && exists $protected{$section}) {
my $users = $protected{$section};
return Apache2::Const::OK if grep { $_ eq $user } @$users;
}
else {
return Apache2::Const::OK;
}
}
$r->note_basic_auth_failure;
return Apache2::Const::HTTP_UNAUTHORIZED;
}
1;
This authorization handler is very similar to the authentication handler from the previous section. Here we rely on the previous phase to get users authenticated, and now as we have the username we can make decisions whether to let the user access the resource it has asked for or not. In our example we have a simple hash which maps which users are allowed to access what resources. So for example anything under /company/admin/ can be accessed only by the user stas, /company/report/ can be accessed by users stas and boss, whereas any other resources under /company/ can be accessed by everybody who has reached so far. If for some reason we don't get the username, we or the user is not authorized to access the resource the handler does the same thing as it does when the authentication fails, i.e, calls:
$r->note_basic_auth_failure;
return Apache2::Const::HTTP_UNAUTHORIZED;
The configuration is similar to the one in the previous section, this time we just add the
PerlAuthzHandler setting. The rest doesn't change.
Alias /company/ /home/httpd/httpd-2.0/perl/
<Location /company/>
SetHandler perl-script
PerlResponseHandler ModPerl::Registry
PerlAuthenHandler MyApache2::SecretLengthAuth
PerlAuthzHandler MyApache2::SecretResourceAuthz
Options +ExecCGI
AuthType Basic
AuthName "The Secret Gate"
Require valid-user
</Location>
And if you want to run the authentication and authorization for the whole site, simply add:
<Location />
PerlAuthenHandler MyApache2::SecretLengthAuth
PerlAuthzHandler MyApache2::SecretResourceAuthz
AuthType Basic
AuthName "The Secret Gate"
Require valid-user
</Location>
The type_checker phase is used to set the response MIME type
(Content-type) and sometimes other bits of document type
information like the document language.
For example mod_autoindex, which performs automatic directory
indexing, uses this phase to map the filename extensions to the
corresponding icons which will be later used in the listing of files.
Of course later phases may override the mime type set in this phase.
This phase is of type
RUN_FIRST.
The handler's configuration scope is
DIR.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
The most important thing to remember when overriding the default
type_checker handler, which is usually the mod_mime handler, is
that you have to set the handler that will take care of the response
phase and the response callback function or the code won't
work. mod_mime does that based on SetHandler and AddHandler
directives, and file extensions. So if you want the content handler to
be run by mod_perl, set either:
$r->handler('perl-script');
$r->set_handlers(PerlResponseHandler => \&handler);
or:
$r->handler('modperl');
$r->set_handlers(PerlResponseHandler => \&handler);
depending on which type of response handler is wanted.
Writing a PerlTypeHandler handler which sets the content-type value
and returns Apache2::Const::DECLINED so that the default handler
will do the rest of the work, is not a good idea, because mod_mime
will probably override this and other settings.
Therefore it's the easiest to leave this stage alone and do any desired settings in the fixups phase.
The fixups phase is happening just before the content handling
phase. It gives the last chance to do things before the response is
generated. For example in this phase mod_env populates the
environment with variables configured with SetEnv and PassEnv
directives.
This phase is of type
RUN_ALL.
The handler's configuration scope is
DIR.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
The following fixup handler example tells Apache at run time which handler and callback should be used to process the request based on the file extension of the request's URI.
#file:MyApache2/FileExtDispatch.pm
#--------------------------------
package MyApache2::FileExtDispatch;
use strict;
use warnings;
use Apache2::RequestIO ();
use Apache2::RequestRec ();
use Apache2::RequestUtil ();
use Apache2::Const -compile => 'OK';
use constant HANDLER => 0;
use constant CALLBACK => 1;
my %exts = (
cgi => ['perl-script', \&cgi_handler],
pl => ['modperl', \&pl_handler ],
tt => ['perl-script', \&tt_handler ],
txt => ['default-handler', undef ],
);
sub handler {
my $r = shift;
my ($ext) = $r->uri =~ /\.(\w+)$/;
$ext = 'txt' unless defined $ext and exists $exts{$ext};
$r->handler($exts{$ext}->[HANDLER]);
if (defined $exts{$ext}->[CALLBACK]) {
$r->set_handlers(PerlResponseHandler => $exts{$ext}->[CALLBACK]);
}
return Apache2::Const::OK;
}
sub cgi_handler { content_handler($_[0], 'cgi') }
sub pl_handler { content_handler($_[0], 'pl') }
sub tt_handler { content_handler($_[0], 'tt') }
sub content_handler {
my ($r, $type) = @_;
$r->content_type('text/plain');
$r->print("A handler of type '$type' was called");
return Apache2::Const::OK;
}
1;
In the example we have used the following mapping.
my %exts = (
cgi => ['perl-script', \&cgi_handler],
pl => ['modperl', \&pl_handler ],
tt => ['perl-script', \&tt_handler ],
txt => ['default-handler', undef ],
);
So that .cgi requests will be handled by the perl-script handler
and the cgi_handler() callback, .pl requests by modperl and
pl_handler(), .tt (template toolkit) by perl-script and the
tt_handler(), finally .txt request by the default-handler
handler, which requires no callback.
Moreover the handler assumes that if the request's URI has no file
extension or it does, but it's not in its mapping, the
default-handler will be used, as if the txt extension was used.
After doing the mapping, the handler assigns the handler:
$r->handler($exts{$ext}->[HANDLER]);
and the callback if needed:
if (defined $exts{$ext}->[CALLBACK]) {
$r->set_handlers(
PerlResponseHandler => $exts{$ext}->[CALLBACK]);
}
In this simple example the callback functions don't do much but calling the same content handler which simply prints the name of the extension if handled by mod_perl, otherwise Apache will serve the other files using the default handler. In real world you will use callbacks to real content handlers that do real things.
Here is how this handler is configured:
Alias /dispatch/ /home/httpd/httpd-2.0/htdocs/
<Location /dispatch/>
PerlFixupHandler MyApache2::FileExtDispatch
</Location>
Notice that there is no need to specify anything, but the fixup handler. It applies the rest of the settings dynamically at run-time.
The handler (response) phase is used for generating the response. This is arguably the most important phase and most of the existing Apache modules do most of their work at this phase.
This is the only phase that requires two directives under mod_perl. For example:
<Location /perl>
SetHandler perl-script
PerlResponseHandler MyApache2::WorldDomination
</Location>
SetHandler set to
perl-script or
modperl tells Apache
that mod_perl is going to handle the response
generation. PerlResponseHandler tells mod_perl which callback is
going to do the job.
This phase is of type
RUN_FIRST.
The handler's configuration scope is
DIR.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
Most of the Apache:: modules on CPAN are dealing with this
phase. In fact most of the developers spend the majority of their time
working on handlers that generate response content.
Let's write a simple response handler, that just generates some content. This time let's do something more interesting than printing "Hello world". Let's write a handler that prints itself:
#file:MyApache2/Deparse.pm
#------------------------
package MyApache2::Deparse;
use strict;
use warnings;
use Apache2::RequestRec ();
use Apache2::RequestIO ();
use B::Deparse ();
use Apache2::Const -compile => 'OK';
sub handler {
my $r = shift;
$r->content_type('text/plain');
$r->print('sub handler ', B::Deparse->new->coderef2text(\&handler));
return Apache2::Const::OK;
}
1;
To enable this handler add to httpd.conf:
<Location /deparse>
SetHandler modperl
PerlResponseHandler MyApache2::Deparse
</Location>
Now when the server is restarted and we issue a request to http://localhost/deparse we get the following response:
sub handler {
package MyApache2::Deparse;
use warnings;
use strict 'refs';
my $r = shift @_;
$r->content_type('text/plain');
$r->print('sub handler ', 'B::Deparse'->new->coderef2text(\&handler));
return 0;
}
If you compare it to the source code, it's pretty much the same
code. B::Deparse is fun to play with!
The log_transaction phase happens no matter how the previous phases have ended up. If one of the earlier phases has aborted a request, e.g., failed authentication or 404 (file not found) errors, the rest of the phases up to and including the response phases are skipped. But this phase is always executed.
By this phase all the information about the request and the response is known, therefore the logging handlers usually record this information in various ways (e.g., logging to a flat file or a database).
This phase is of type
RUN_ALL.
The handler's configuration scope is
DIR.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
Imagine a situation where you have to log requests into individual files, one per user. Assuming that all requests start with /~username/, so it's easy to categorize requests by the username. Here is the log handler that does that:
#file:MyApache2/LogPerUser.pm
#---------------------------
package MyApache2::LogPerUser;
use strict;
use warnings;
use Apache2::RequestRec ();
use Apache2::Connection ();
use Fcntl qw(:flock);
use File::Spec::Functions qw(catfile);
use Apache2::Const -compile => qw(OK DECLINED);
sub handler {
my $r = shift;
my ($username) = $r->uri =~ m|^/~([^/]+)|;
return Apache2::Const::DECLINED unless defined $username;
my $entry = sprintf qq(%s [%s] "%s" %d %d\n),
$r->connection->remote_ip, scalar(localtime),
$r->uri, $r->status, $r->bytes_sent;
my $log_path = catfile Apache2::ServerUtil::server_root,
"logs", "$username.log";
open my $fh, ">>$log_path" or die "can't open $log_path: $!";
flock $fh, LOCK_EX;
print $fh $entry;
close $fh;
return Apache2::Const::OK;
}
1;
First the handler tries to figure out what username the request is
issued for, if it fails to match the URI, it simply returns
Apache2::Const::DECLINED, letting other log handlers to do the
logging. Though it could return Apache2::Const::OK since all other
log handlers will be run anyway.
Next it builds the log entry, similar to the default access_log entry. It's comprised of remote IP, the current time, the uri, the return status and how many bytes were sent to the client as a response body.
Finally the handler appends this entry to the log file for the user the request was issued for. Usually it's safe to append short strings to the file without being afraid of messing up the file, when two files attempt to write at the same time, but just to be on the safe side the handler exclusively locks the file before performing the writing.
To configure the handler simply enable the module with the
PerlLogHandler directive, for the desired URI namespace (starting
with : /~ in our example):
<LocationMatch "^/~">
SetHandler perl-script
PerlResponseHandler ModPerl::Registry
PerlLogHandler MyApache2::LogPerUser
Options +ExecCGI
</LocationMatch>
After restarting the server and issuing requests to the following URIs:
http://localhost/~stas/test.pl http://localhost/~eric/test.pl http://localhost/~stas/date.pl
The MyApache2::LogPerUser handler will append to logs/stas.log:
127.0.0.1 [Sat Aug 31 01:50:38 2002] "/~stas/test.pl" 200 8 127.0.0.1 [Sat Aug 31 01:50:40 2002] "/~stas/date.pl" 200 44
and to logs/eric.log:
127.0.0.1 [Sat Aug 31 01:50:39 2002] "/~eric/test.pl" 200 8
It's important to notice that PerlLogHandler can be configured for
any subsection of the site, no matter whether it's served by a
mod_perl response handler or not. For example to run the handler from
our example for all requests to the server, simply add to
httpd.conf:
<Location />
PerlLogHandler MyApache2::LogPerUser
</Location>
Since the PerlLogHandler phase is of type
RUN_ALL, all other
logging handlers will be called as well.
There is no cleanup Apache phase, it exists only inside mod_perl. It is used to execute some code immediately after the request has been served (the client went away) and before the request object is destroyed.
There are several usages for this use phase. The obvious one is to run
a cleanup code, for example removing temporarily created files. The
less obvious is to use this phase instead of
PerlLogHandler if the logging operation is time
consuming. This approach allows to free the client as soon as the
response is sent.
This phase is of type
RUN_ALL.
The handler's configuration scope is
DIR.
Arguments
See the HTTP Request Handler Skeleton for a description of handler arguments.
Return
See Stacked Handlers for a description of handler return codes.
Examples
There are two ways to register and run cleanup handlers:
PerlCleanupHandler phase
PerlCleanupHandler MyApache2::Cleanup
or:
$r->push_handlers(PerlCleanupHandler => \&cleanup);
This method is identical to all other handlers.
In this technique the cleanup() callback accepts $r as its only
argument.
cleanup_register() acting on the request object's pool
Since a request object pool is destroyed at the end of each request,
we can use
cleanup_register
to register a cleanup callback which will be executed just before the
pool is destroyed. For example:
$r->pool->cleanup_register(\&cleanup, $arg);
The important difference from using the PerlCleanupHandler handler,
is that here you can pass an optional arbitrary argument to the
callback function, and no $r argument is passed by
default. Therefore if you need to pass any data other than $r you
may want to use this technique.
Here is an example where the cleanup handler is used to delete a
temporary file. The response handler is running ls -l and stores
the output in temporary file, which is then used by
$r->sendfile to send the file's contents. We use
push_handlers() to push PerlCleanupHandler to unlink the file at
the end of the request.
#file:MyApache2/Cleanup1.pm
#-------------------------
package MyApache2::Cleanup1;
use strict;
use warnings FATAL => 'all';
use File::Spec::Functions qw(catfile);
use Apache2::RequestRec ();
use Apache2::RequestIO ();
use Apache2::RequestUtil ();
use Apache2::Const -compile => qw(OK DECLINED);
use APR::Const -compile => 'SUCCESS';
my $file = catfile "/tmp", "data";
sub handler {
my $r = shift;
$r->content_type('text/plain');
local @ENV{qw(PATH BASH_ENV)};
qx(/bin/ls -l > $file);
my $status = $r->sendfile($file);
die "sendfile has failed" unless $status == APR::Const::SUCCESS;
$r->push_handlers(PerlCleanupHandler => \&cleanup);
return Apache2::Const::OK;
}
sub cleanup {
my $r = shift;
die "Can't find file: $file" unless -e $file;
unlink $file or die "failed to unlink $file";
return Apache2::Const::OK;
}
1;
Next we add the following configuration:
<Location /cleanup1>
SetHandler modperl
PerlResponseHandler MyApache2::Cleanup1
</Location>
Now when a request to /cleanup1 is made, the contents of the current directory will be printed and once the request is over the temporary file is deleted.
This response handler has a problem of running in a multi-process
environment, since it uses the same file, and several processes may
try to read/write/delete that file at the same time, wrecking
havoc. We could have appended the process id $$ to the file's name,
but remember that mod_perl 2.0 code may run in the threaded
environment, meaning that there will be many threads running in the
same process and the $$ trick won't work any longer. Therefore one
really has to use this code to create unique, but predictable, file
names across threads and processes:
sub unique_id {
require Apache2::MPM;
require APR::OS;
return Apache2::MPM->is_threaded
? "$$." . ${ APR::OS::current_thread_id() }
: $$;
}
In the threaded environment it will return a string containing the
process ID, followed by a thread ID. In the non-threaded environment
only the process ID will be returned. However since it gives us a
predictable string, they may still be a non-satisfactory
solution. Therefore we need to use a random string. We can either
either Perl's rand, some CPAN module or the APR's APR::UUID:
sub unique_id {
require APR::UUID;
return APR::UUID->new->format;
}
Now the problem is how do we tell the cleanup handler what file should
be cleaned up? We could have stored it in the $r->notes table
in the response handler and then retrieve it in the cleanup
handler. However there is a better way - as mentioned earlier, we can
register a callback for request pool cleanup, and when using this
method we can pass an arbitrary argument to it. Therefore in our case
we choose to pass the file name, based on random string. Here is a
better version of the response and cleanup handlers, that uses this
technique:
#file: MyApache2/Cleanup2.pm
#-------------------------
package MyApache2::Cleanup2;
use strict;
use warnings FATAL => 'all';
use File::Spec::Functions qw(catfile);
use Apache2::RequestRec ();
use Apache2::RequestIO ();
use Apache2::RequestUtil ();
use APR::UUID ();
use APR::Pool ();
use Apache2::Const -compile => qw(OK DECLINED);
use APR::Const -compile => 'SUCCESS';
my $file_base = catfile "/tmp", "data-";
sub handler {
my $r = shift;
$r->content_type('text/plain');
my $file = $file_base . APR::UUID->new->format;
local @ENV{qw(PATH BASH_ENV)};
qx(/bin/ls -l > $file);
my $status = $r->sendfile($file);
die "sendfile has failed" unless $status == APR::Const::SUCCESS;
$r->pool->cleanup_register(\&cleanup, $file);
return Apache2::Const::OK;
}
sub cleanup {
my $file = shift;
die "Can't find file: $file" unless -e $file;
unlink $file or die "failed to unlink $file";
return Apache2::Const::OK;
}
1;
Similarly to the first handler, we add the configuration:
<Location /cleanup2>
SetHandler modperl
PerlResponseHandler MyApache2::Cleanup2
</Location>
And now when requesting /cleanup2 we still get the same output -- the listing of the current directory -- but this time this code will work correctly in the multi-processes/multi-threaded environment and temporary files get cleaned up as well.
PerlCleanupHandler may fail to be completed on server
shutdown/graceful restart since Apache will kill the registered
handlers via SIGTERM, before they had a chance to run or even in the
middle of its execution. See:
http://marc.theaimsgroup.com/?t=106387845200003&r=1&w=2
http://marc.theaimsgroup.com/?l=apache-modperl-dev&m=106427616108596&w=2
In order to avoid the overhead of sending the data to the client when the request is of type HEAD in mod_perl 1.0 we used to return early from the handler:
return Apache2::Const::OK if $r->header_only;
This logic should not be used in mod_perl 2.0, because Apache 2.0 automatically discards the response body for HEAD requests. It expects the full body to generate the correct set of response headers, if you don't send the body you may encounter problems.
(You can also read the comment in for ap_http_header_filter() in
modules/http/http_protocol.c in the Apache 2.0 source.)
Content-Length Response HeaderYou may encounter some issues with the C-L (Content-Length)
header. Some of them are discussed here.
Content-Length: 0
Since Apache proclaims itself governor of the C-L header via the C-L
filter (ap_content_length_filter at httpd-2.0/server/protocol.c),
for the most part GET and HEAD behave exactly the same.
However, when Apache sees a HEAD request with a C-L header of zero
it takes special action and removes the C-L header. This is done to
protect against handlers that called $r->header_only (which was ok in 1.3 but is not in 2.0). Therefore,
GET and HEAD behave identically, except when the content
handler (and/or filters) end up sending no content. For more details
refer to the lengthy comments in ap_http_header_filter() in
httpd-2.0/modules/http/http_protocol.c).
For more discussion on why it is important to get HEAD requests right, see these threads from the mod_perl list:
http://marc.theaimsgroup.com/?l=apache-modperl&m=108647669726915&w=2 http://marc.theaimsgroup.com/?t=109122984600001&r=1&w=2
as well as this bug report from mozilla, which shows how HEAD
requests are used in the wild:
http://bugzilla.mozilla.org/show_bug.cgi?id=245447
Content-Length header with HEAD requests
Even though the spec says that content handlers should send an identical response for GET and HEAD requests, some folks try to avoid the overhead of generating the response body, which Apache is going to discard anyway for HEAD requests. The following discussion assumes that we deal with a HEAD request.
When Apache sees EOS and no headers and no response body were sent,
ap_content_length_filter() (httpd-2.0/server/protocol.c) sets
C-L to 0. Later on ap_http_header_filter()
(httpd-2.0/modules/http/http_protocol.c) removes the C-L header for
the HEAD requests.
The workaround is to force the sending of the response headers, before
EOS was sent (which happens when the response handler returns). The
simplest solution is to use rflush():
if ($r->header_only) { # HEAD
$body_len = calculate_body_len();
$r->set_content_length($body_len);
$r->rflush;
}
else { # GET
# generate and send the body
}
now if the handler sets the C-L header it'll be delivered to the client unmodified.
These items will need to be extended and integrated in this or other HTTP related documents:
apache-1.3:
frontend: mod_proxy_add_forward http://develooper.com/code/mpaf/
backend: mod_rpaf (reverse proxy add forward): http://stderr.net/apache/rpaf/
apache-2.x:
frontend: mod_proxy
backend: mod_rpaf: http://stderr.net/apache/rpaf/
Extending HTTP under mod_perl is a trivial task. Look at the example of adding a new method EMAIL for
details.
The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. It is a generic, stateless, protocol which can be used for many tasks beyond its use for hypertext, such as name servers and distributed object management systems, through extension of its request methods, error codes and headers. A feature of HTTP is the typing and negotiation of data representation, allowing systems to be built independently of the data being transferred.
HTTP 1.0 is described in Requests For Comments (RFC) 1945. HTTP 1.1 is the latest version of the specifications and as of this writing HTTP 1.1 is covered in RFC 2616.
When writing mod_perl applications, usually only a small subset of HTTP response codes is used, but sometimes you need to know others as well. We will give a short description of each code and you will find the extended explanation in the appropriate RFC. (Section 9 in RFC 1945 and section 10 in RFC 2616). You can always find the latest link to these RFCs at the Web Consortium site, http://www.w3.org/Protocols/.
While HTTP 1.1 is widely supported, HTTP 1.0 still remains the mainstream standard. Therefore we will supply a summary of the both versions including the corresponding Apache constants.
In mod_perl these constants can be accessed the
Apache::Constants
package (e.g., to access the HTTP_OK constant use
Apache::Constants::HTTP_OK). See the
Apache::Constants manpage
for more information.
In mod_perl2 these constants can be accessed the
Apache2::Const
package (e.g., to access the HTTP_OK constant use
Apache2::Const::HTTP_OK). See the
Apache2::Const manpage
for more information.
Successful 2xx:
200 HTTP_OK OK 201 HTTP_CREATED Created 202 HTTP_ACCEPTED Accepted 204 HTTP_NO_CONTENT No Content
Redirection 3xx:
301 HTTP_MOVED_PERMANENTLY Multiple Choices 302 HTTP_MOVED_TEMPORARILY Moved Permanently 303 HTTP_SEE_OTHER Moved Temporarily 304 HTTP_NOT_MODIFIED Not Modified
Client Error 4xx:
400 HTTP_BAD_REQUEST Bad Request 401 HTTP_UNAUTHORIZED Unauthorized 403 HTTP_FORBIDDEN Forbidden 404 HTTP_NOT_FOUND Not Found
Server Error 5xx:
500 HTTP_INTERNAL_SERVER_ERROR Internal Server Error 501 HTTP_NOT_IMPLEMENTED Not Implemented 502 HTTP_BAD_GATEWAY Bad Gateway 503 HTTP_SERVICE_UNAVAILABLE Service UnavailableStatus Codes
Informational 1xx:
100 HTTP_CONTINUE Continue 101 HTTP_SWITCHING_PROTOCOLS Switching Protocols
Successful 2xx:
200 HTTP_OK OK 201 HTTP_CREATED Created 202 HTTP_ACCEPTED Accepted 203 HTTP_NON_AUTHORITATIVE Non-Authoritative Information 204 HTTP_NO_CONTENT No Content 205 HTTP_RESET_CONTENT Reset Content 206 HTTP_PARTIAL_CONTENT Partial Content
Redirection 3xx:
300 HTTP_MULTIPLE_CHOICES Multiple Choices 301 HTTP_MOVED_PERMANENTLY Moved Permanently 302 HTTP_MOVED_TEMPORARILY Found 303 HTTP_SEE_OTHER See Other 304 HTTP_NOT_MODIFIED Not Modified 305 HTTP_USE_PROXY Use Proxy 306 (Unused) 307 HTTP_TEMPORARY_REDIRECT Temporary Redirect
Client Error 4xx:
400 HTTP_BAD_REQUEST Bad Request 401 HTTP_UNAUTHORIZED Unauthorized 402 HTTP_PAYMENT_REQUIRED Payment Required 403 HTTP_FORBIDDEN Forbidden 404 HTTP_NOT_FOUND Not Found 405 HTTP_METHOD_NOT_ALLOWED Method Not Allowed 406 HTTP_NOT_ACCEPTABLE Not Acceptable 407 HTTP_PROXY_AUTHENTICATION_REQUIRED Proxy Authentication Required 408 HTTP_REQUEST_TIMEOUT Request Timeout 409 HTTP_CONFLICT Conflict 410 HTTP_GONE Gone 411 HTTP_LENGTH REQUIRED Length Required 412 HTTP_PRECONDITION_FAILED Precondition Failed 413 HTTP_REQUEST_ENTITY_TOO_LARGE Request Entity Too Large 414 HTTP_REQUEST_URI_TOO_LARGE Request-URI Too Long 415 HTTP_UNSUPPORTED_MEDIA_TYPE Unsupported Media Type 416 HTTP_RANGE_NOT_SATISFIABLE Requested Range Not Satisfiable 417 HTTP_EXPECTATION_FAILED Expectation Failed
Server Error 5xx:
500 HTTP_INTERNAL_SERVER_ERROR Internal Server Error 501 HTTP_NOT IMPLEMENTED Not Implemented 502 HTTP_BAD_GATEWAY Bad Gateway 503 HTTP_SERVICE_UNAVAILABLE Service Unavailable 504 HTTP_GATEWAY_TIME_OUT Gateway Timeout 505 HTTP_VERSION_NOT_SUPPORTED HTTP Version Not Supported
All the information related to web protocols can be found at the World Wide Web Consortium site, http://www.w3.org/Protocols/.
There are many mirrors of the RFCs all around the world. One of the good starting points might be http://www.rfc-editor.org/.
The Eagle Book provided much of the HTTP constants material shown here http://www.modperl.com/book/chapters/ch9.html#The_Apache_Constants_Class
Stas Bekman [http://stason.org/]
Only the major authors are listed above. For contributors see the Changes file.
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Last modified Sun Jul 30 09:57:58 2017
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