| IO::Socket::SSL -- Nearly transparent SSL encapsulation for IO::Socket::INET. |
IO::Socket::SSL -- Nearly transparent SSL encapsulation for IO::Socket::INET.
use IO::Socket::SSL;
my $client = IO::Socket::SSL->new("www.example.com:https");
if ($client) {
print $client "GET / HTTP/1.0\r\n\r\n";
print <$client>;
close $client;
} else {
warn "I encountered a problem: ",
IO::Socket::SSL::errstr();
}
This module is a true drop-in replacement for IO::Socket::INET that uses SSL to encrypt data before it is transferred to a remote server or client. IO::Socket::SSL supports all the extra features that one needs to write a full-featured SSL client or server application: multiple SSL contexts, cipher selection, certificate verification, and SSL version selection. As an extra bonus, it works perfectly with mod_perl.
If you have never used SSL before, you should read the appendix labelled 'Using SSL' before attempting to use this module.
If you have used this module before, read on, as versions 0.93 and above have several changes from the previous IO::Socket::SSL versions (especially see the note about return values).
If you are using non-blocking sockets read on, as version 0.98 added better support for non-blocking.
If you are trying to use it with threads see the BUGS section.
IO::Socket::SSL inherits its methods from IO::Socket::INET, overriding them as necessary. If there is an SSL error, the method or operation will return an empty list (false in all contexts). The methods that have changed from the perspective of the user are re-documented here:
If you use this option, all other context-related options that you pass
in the same call to new() will be ignored unless the context supplied was invalid.
Note that, contrary to versions of IO::Socket::SSL below v0.90, a global SSL context
will not be implicitly used unless you use the set_default_context() function.
new() calls (or use set_default_context()) to make use of the cached sessions.
The session cache size refers to the number of unique host/port pairs that can be
stored at one time; the oldest sessions in the cache will be removed if new ones are
added.
A session cache object can be created using
IO::Socket::SSL::Session_Cache->new( cachesize ).
Use set_default_session_cache() to set a global cache object.
accept() or connect() methods, it may be the case that the
actual socket connection works but the SSL negotiation fails, as in the case of
an HTTP client connecting to an HTTPS server. Passing a subroutine ref attached
to this parameter allows you to gain control of the orphaned socket instead of having it
be closed forcibly. The subroutine, if called, will be passed two parameters:
a reference to the socket on which the SSL negotiation failed and and the full
text of the error message.
shutdown() on your
sockets. Since the SSL protocol mandates that a SSL ``close notify'' message be
sent before the socket is closed, a shutdown() that closes the socket's write channel
will cause the close() call to hang. For a similar reason, if you try to close a
copy of a socket (as in a forking server) you will affect the original socket as well.
To get around these problems, call close with an object-oriented syntax
(e.g. $socket->close(SSL_no_shutdown => 1))
and one or more of the following parameters:
close() not use the SSL_shutdown() call
on the socket in question so that the close operation can complete without problems
if you have used shutdown() or are working on a copy of a socket.
SSL_shutdown(3)) will be called. Otherwise a bidrectional
shutdown will be done. If used within close() it defaults to true, if used
within stop_SSL() it defaults to false.
peek() with the same arguments will return the same results.
This function requires OpenSSL 0.9.6a or later to work.
dump_peer_certificate() method of Net::SSLeay.
For read and write errors on non-blocking sockets, this method may include the string
SSL wants a read first! or SSL wants a write first! meaning that the other side
is expecting to read from or write to the socket and wants to be satisfied before you
get to do anything. But with version 0.98 you are better comparing the global exported
variable $SSL_ERROR against the exported symbols SSL_WANT_READ and SSL_WANT_WRITE.
start_SSL($socket) to achieve the desired effect.
Note that if start_SSL() fails in SSL negotiation, $socket will remain blessed in its
original class. For non-blocking sockets you better just upgrade the socket to
IO::Socket::SSL and call accept_SSL or connect_SSL and the upgraded object. To
just upgrade the socket set SSL_startHandshake explicitly to 0. If you call start_SSL
w/o this parameter it will revert to blocking behavior for accept_SSL and connect_SSL.
If given the parameter ``Timeout'' it will stop if after the timeout no SSL connection was established. This parameter is only used for blocking sockets, if it is not given the default Timeout from the underlying IO::Socket will be used.
close() calls stop_SSL() (but without downgrading the class).
Will return true if it suceeded and undef if failed. This might be the case for non-blocking sockets. In this case $! is set to EAGAIN and the ssl error to SSL_WANT_READ or SSL_WANT_WRITE. In this case the call should be retried again with the same arguments once the socket is ready is until it succeeds.
new() for more details. Note that this sets the default
context globally, so use with caution (esp. in mod_perl scripts).
new() for more details. Note that this sets the default
cache globally, so use with caution.
The following methods are unsupported (not to mention futile!) and IO::Socket::SSL
will emit a large CROAK() if you are silly enough to use them:
send() and recv() cannot be reliably trapped by a tied filehandle (such as
that used by IO::Socket::SSL) and so may send unencrypted data over the socket. Object-oriented
calls to these functions will fail, telling you to use the print/printf/syswrite
and read/sysread families instead.
A few changes have gone into IO::Socket::SSL v0.93 and later with respect to
return values. The behavior on success remains unchanged, but for all functions,
the return value on error is now an empty list. Therefore, the return value will be
false in all contexts, but those who have been using the return values as arguments
to subroutines (like mysub(IO::Socket::SSL(...)-new, ...)>) may run into problems.
The moral of the story: always check the return values of these functions before
using them in any way that you consider meaningful.
Support for IPv6 with IO::Socket::SSL is expected to work, but is experimental, as
none of the author's machines use IPv6 and hence he cannot test IO::Socket::SSL with
them. However, a few brave people have used it without incident, so if you wish to
make IO::Socket::SSL IPv6 aware, pass the 'inet6' option to IO::Socket::SSL when
calling it (i.e. use IO::Socket::SSL qw(inet6);). You will need IO::Socket::INET6
and Socket6 to use this option, and you will also need to write use Socket6; before
using IO::Socket::SSL. If you absolutely do not want to use this (or want a quick
change back to IPv4), pass the 'inet4' option instead.
Currently, there is no support for using IPv4 and IPv6 simultaneously in a single program, but it is planned for a future release.
If you are having problems using IO::Socket::SSL despite the fact that can recite backwards the section of this documentation labelled 'Using SSL', you should try enabling debugging. To specify the debug level, pass 'debug#' (where # is a number from 0 to 4) to IO::Socket::SSL when calling it:
You can also set $IO::Socket::SSL::DEBUG to 0-4, but that's a bit of a mouthful, isn't it?
See the 'example' directory.
IO::Socket::SSL is not threadsafe. This is because IO::Socket::SSL is based on Net::SSLeay which uses a global object to access some of the API of openssl and is therefore not threadsafe. It might probably work if you don't use SSL_verify_cb and SSL_password_cb.
IO::Socket::SSL does not work together with Storable::fd_retrieve/fd_store. See BUGS file for more information and how to work around the problem.
IO::Socket::SSL uses Net::SSLeay as the shiny interface to OpenSSL, which is the shiny interface to the ugliness of SSL. As a result, you will need both Net::SSLeay and OpenSSL on your computer before using this module.
If you have Scalar::Util (standard with Perl 5.8.0 and above) or WeakRef, IO::Socket::SSL sockets will auto-close when they go out of scope, just like IO::Socket::INET sockets. If you do not have one of these modules, then IO::Socket::SSL sockets will stay open until the program ends or you explicitly close them. This is due to the fact that a circular reference is required to make IO::Socket::SSL sockets act simultaneously like objects and glob references.
The following functions are deprecated and are only retained for compatibility:
context_init()socketToSSL() and socket_to_SSL()start_SSL() instead
get_peer_certificate()peer_certificate() function instead.
Used to return X509_Certificate with methods subject_name and issuer_name.
Now simply returns $self which has these methods (although depreceated).
issuer_name()subject_name()The following classes have been removed:
get_peer_certificate() will still Do The Right Thing)
IO::Socket::INET, IO::Socket::INET6, Net::SSLeay.
Steffen Ullrich, <steffen at genua.de> is the current maintainer.
Peter Behroozi, <behrooz at fas.harvard.edu> (Note the lack of an ``i'' at the end of ``behrooz'')
Marko Asplund, <marko.asplund at kronodoc.fi>, was the original author of IO::Socket::SSL.
Patches incorporated from various people, see file Changes.
Working support for non-blocking was added by Steffen Ullrich.
The rewrite of this module is Copyright (C) 2002-2005 Peter Behroozi.
The original versions of this module are Copyright (C) 1999-2002 Marko Asplund.
This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
If you are unfamiliar with the way OpenSSL works, good references may be found in both the book ``Network Security with OpenSSL'' (Oreilly & Assoc.) and the web site http://www.tldp.org/HOWTO/SSL-Certificates-HOWTO/. Read on for a quick overview.
The usual reason for using SSL is to keep your data safe. This means that not only do you have to encrypt the data while it is being transported over a network, but you also have to make sure that the right person gets the data. To accomplish this with SSL, you have to use certificates. A certificate closely resembles a Government-issued ID (at least in places where you can trust them). The ID contains some sort of identifying information such as a name and address, and is usually stamped with a seal of Government Approval. Theoretically, this means that you may trust the information on the card and do business with the owner of the card. The same ideas apply to SSL certificates, which have some identifying information and are ``stamped'' [most people refer to this as signing instead] by someone (a Certificate Authority) who you trust will adequately verify the identifying information. In this case, because of some clever number theory, it is extremely difficult to falsify the stamping process. Another useful consequence of number theory is that the certificate is linked to the encryption process, so you may encrypt data (using information on the certificate) that only the certificate owner can decrypt.
What does this mean for you? It means that at least one person in the party has to have an ID to get drinks :-). Seriously, it means that one of the people communicating has to have a certificate to ensure that your data is safe. For client/server interactions, the server must always have a certificate. If the server wants to verify that the client is safe, then the client must also have a personal certificate. To verify that a certificate is safe, one compares the stamped ``seal'' [commonly called an encrypted digest/hash/signature] on the certificate with the official ``seal'' of the Certificate Authority to make sure that they are the same. To do this, you will need the [unfortunately named] certificate of the Certificate Authority. With all these in hand, you can set up a SSL connection and be reasonably confident that no-one is reading your data.
For servers, you will need to generate a cryptographic private key and a certificate request. You will need to send the certificate request to a Certificate Authority to get a real certificate back, after which you can start serving people. For clients, you will not need anything unless the server wants validation, in which case you will also need a private key and a real certificate. For more information about how to get these, see http://www.modssl.org/docs/2.8/ssl_faq.html#ToC24.
| IO::Socket::SSL -- Nearly transparent SSL encapsulation for IO::Socket::INET. |