IO::Socket::SSL man page on SuSE

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SSL(3)		      User Contributed Perl Documentation		SSL(3)

NAME
       IO::Socket::SSL -- Nearly transparent SSL encapsulation for
       IO::Socket::INET.

SYNOPSIS
	       use strict;
	       use IO::Socket::SSL;

	       my $client = IO::Socket::SSL->new("www.example.com:https")
		       || warn "I encountered a problem: ".IO::Socket::SSL::errstr();
	       $client->verify_hostname( 'www.example.com','http' )
		       || die "hostname verification failed";

	       print $client "GET / HTTP/1.0\r\n\r\n";
	       print <$client>;

DESCRIPTION
       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.

METHODS
       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:

       new(...)
	   Creates a new IO::Socket::SSL object.  You may use all the friendly
	   options that came bundled with IO::Socket::INET, plus (optionally)
	   the ones that follow:

	   SSL_version
	     Sets the version of the SSL protocol used to transmit data.  The
	     default is SSLv2/3, which auto-negotiates between SSLv2 and
	     SSLv3.    You may specify 'SSLv2', 'SSLv3', or 'TLSv1' (case-
	     insensitive) if you do not want this behavior.

	   SSL_cipher_list
	     If this option is set the cipher list for the connection will be
	     set to the given value, e.g. something like 'ALL:!LOW:!EXP:!ADH'.
	     Look into the OpenSSL documentation
	     (<http://www.openssl.org/docs/apps/ciphers.html#CIPHER_STRINGS>)
	     for more details.	If this option is not used the openssl builtin
	     default is used which is suitable for most cases.

	   SSL_use_cert
	     If this is set, it forces IO::Socket::SSL to use a certificate
	     and key, even if you are setting up an SSL client.	 If this is
	     set to 0 (the default), then you will only need a certificate and
	     key if you are setting up a server.

	     SSL_use_cert will implicitly be set if SSL_server is set.	For
	     convinience it is also set if it was not given but a cert was
	     given for use (SSL_cert_file or similar).

	   SSL_server
	     Use this, if the socket should be used as a server.  If this is
	     not explicitly set it is assumed, if Listen with given when
	     creating the socket.

	   SSL_key_file
	     If your RSA private key is not in default place
	     (certs/server-key.pem for servers, certs/client-key.pem for
	     clients), then this is the option that you would use to specify a
	     different location.  Keys should be PEM formatted, and if they
	     are encrypted, you will be prompted to enter a password before
	     the socket is formed (unless you specified the SSL_passwd_cb
	     option).

	   SSL_key
	     This is an EVP_PKEY* and can be used instead of SSL_key_file.
	     Useful if you don't have your key in a file but create it
	     dynamically or get it from a string (see openssl
	     PEM_read_bio_PrivateKey etc for getting a EVP_PKEY* from a
	     string).

	   SSL_cert_file
	     If your SSL certificate is not in the default place
	     (certs/server-cert.pem for servers, certs/client-cert.pem for
	     clients), then you should use this option to specify the location
	     of your certificate.  Note that a key and certificate are only
	     required for an SSL server, so you do not need to bother with
	     these trifling options should you be setting up an
	     unauthenticated client.

	   SSL_cert
	     This is an X509* or an array of X509*.  The first X509* is the
	     internal representation of the certificate while the following
	     ones are extra certificates. Useful if you create your
	     certificate dynamically (like in a SSL intercepting proxy) or get
	     it from a string (see openssl PEM_read_bio_X509 etc for getting a
	     X509* from a string).

	   SSL_dh_file
	     If you want Diffie-Hellman key exchange you need to supply a
	     suitable file here or use the SSL_dh parameter. See dhparam
	     command in openssl for more information.

	   SSL_dh
	     Like SSL_dh_file, but instead of giving a file you use a
	     preloaded or generated DH*.

	   SSL_passwd_cb
	     If your private key is encrypted, you might not want the default
	     password prompt from Net::SSLeay.	This option takes a reference
	     to a subroutine that should return the password required to
	     decrypt your private key.

	   SSL_ca_file
	     If you want to verify that the peer certificate has been signed
	     by a reputable certificate authority, then you should use this
	     option to locate the file containing the certificate(s) of the
	     reputable certificate authorities if it is not already in the
	     file certs/my-ca.pem.  If you definitly want no SSL_ca_file used
	     you should set it to undef.

	   SSL_ca_path
	     If you are unusually friendly with the OpenSSL documentation, you
	     might have set yourself up a directory containing several trusted
	     certificates as separate files as well as an index of the
	     certificates.  If you want to use that directory for validation
	     purposes, and that directory is not ca/, then use this option to
	     point IO::Socket::SSL to the right place to look.	If you
	     definitly want no SSL_ca_path used you should set it to undef.

	   SSL_verify_mode
	     This option sets the verification mode for the peer certificate.
	     The default (0x00) does no authentication.	    You may combine
	     0x01 (verify peer), 0x02 (fail verification if no peer
	     certificate exists; ignored for clients), and 0x04 (verify client
	     once) to change the default.

	     See OpenSSL man page for SSL_CTX_set_verify for more information.

	   SSL_verify_callback
	     If you want to verify certificates yourself, you can pass a sub
	     reference along with this parameter to do so.  When the callback
	     is called, it will be passed:

	     1. a true/false value that indicates what OpenSSL thinks of the
	     certificate,
	     2. a C-style memory address of the certificate store,
	     3. a string containing the certificate's issuer attributes and
	     owner attributes, and
	     4. a string containing any errors encountered (0 if no errors).
	     5. a C-style memory address of the peer's own certificate
	     (convertible to PEM form with
	     Net::SSLeay::PEM_get_string_X509()).

	     The function should return 1 or 0, depending on whether it thinks
	     the certificate is valid or invalid.  The default is to let
	     OpenSSL do all of the busy work.

	     The callback will be called for each element in the certificate
	     chain.

	     See the OpenSSL documentation for SSL_CTX_set_verify for more
	     information.

	   SSL_verifycn_scheme
	     Set the scheme used to automatically verify the hostname of the
	     peer.  See the information about the verification schemes in
	     verify_hostname.  The default is undef, e.g. to not automatically
	     verify the hostname.

	   SSL_verifycn_name
	     Set the name which is used in verification of hostname. If
	     SSL_verifycn_scheme is set and no SSL_verifycn_name is given it
	     will try to use the PeerHost and PeerAddr settings and fail if no
	     name caan be determined.

	     Using PeerHost or PeerAddr works only if you create the
	     connection directly with "IO::Socket::SSL->new", if an
	     IO::Socket::INET object is upgraded with start_SSL the name has
	     to be given in SSL_verifycn_name.

	   SSL_check_crl
	     If you want to verify that the peer certificate has not been
	     revoked by the signing authority, set this value to true. OpenSSL
	     will search for the CRL in your SSL_ca_path, or use the file
	     specified by SSL_crl_file.	 See the Net::SSLeay documentation for
	     more details.  Note that this functionality appears to be broken
	     with OpenSSL < v0.9.7b, so its use with lower versions will
	     result in an error.

	   SSL_crl_file
	     If you want to specify the CRL file to be used, set this value to
	     the pathname to be used.  This must be used in addition to
	     setting SSL_check_crl.

	   SSL_reuse_ctx
	     If you have already set the above options (SSL_version through
	     SSL_check_crl; this does not include SSL_cipher_list yet) for a
	     previous instance of IO::Socket::SSL, then you can reuse the SSL
	     context of that instance by passing it as the value for the
	     SSL_reuse_ctx parameter.  You may also create a new instance of
	     the IO::Socket::SSL::SSL_Context class, using any context options
	     that you desire without specifying connection options, and pass
	     that here instead.

	     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.

	   SSL_session_cache_size
	     If you make repeated connections to the same host/port and the
	     SSL renegotiation time is an issue, you can turn on client-side
	     session caching with this option by specifying a positive cache
	     size.  For successive connections, pass the SSL_reuse_ctx option
	     to the 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.

	   SSL_session_cache
	     Specifies session cache object which should be used instead of
	     creating a new.  Overrules SSL_session_cache_size.	 This option
	     is useful if you want to reuse the cache, but not the rest of the
	     context.

	     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.

	   SSL_error_trap
	     When using the 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.

       close(...)
	   There are a number of nasty traps that lie in wait if you are not
	   careful about using close().	 The first of these will bite you if
	   you have been using 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:

	   SSL_no_shutdown
	     If set to a true value, this option will make 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_fast_shutdown
	     If set to true only a unidirectional shutdown will be done, e.g.
	     only the close_notify (see 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.

	   SSL_ctx_free
	     If you want to make sure that the SSL context of the socket is
	     destroyed when you close it, set this option to a true value.

       peek(...)
	   This function has exactly the same syntax as sysread(), and
	   performs nearly the same task (reading data from the socket) but
	   will not advance the read position so that successive calls to
	   peek() with the same arguments will return the same results.	 This
	   function requires OpenSSL 0.9.6a or later to work.

       pending()
	   This function will let you know how many bytes of data are
	   immediately ready for reading from the socket.  This is especially
	   handy if you are doing reads on a blocking socket or just want to
	   know if new data has been sent over the socket.

       get_cipher()
	   Returns the string form of the cipher that the IO::Socket::SSL
	   object is using.

       dump_peer_certificate()
	   Returns a parsable string with select fields from the peer SSL
	   certificate.	     This method directly returns the result of the
	   dump_peer_certificate() method of Net::SSLeay.

       peer_certificate($field)
	   If a peer certificate exists, this function can retrieve values
	   from it.  If no field is given the internal representation of
	   certificate from Net::SSLeay is returned.  The following fields can
	   be queried:

	   authority (alias issuer)
		   The certificate authority which signed the certificate.

	   owner (alias subject)
		   The owner of the certificate.

	   commonName (alias cn) - only for Net::SSLeay version >=1.30
		   The common name, usually the server name for SSL
		   certificates.

	   subjectAltNames - only for Net::SSLeay version >=1.33
		   Alternative names for the subject, usually different names
		   for the same server, like example.org, example.com,
		   *.example.com.

		   It returns a list of (typ,value) with typ GEN_DNS,
		   GEN_IPADD etc (these constants are exported from
		   IO::Socket::SSL).  See
		   Net::SSLeay::X509_get_subjectAltNames.

       verify_hostname($hostname,$scheme)
	   This verifies the given hostname against the peer certificate using
	   the given scheme. Hostname is usually what you specify within the
	   PeerAddr.

	   Verification of hostname against a certificate is different between
	   various applications and RFCs. Some scheme allow wildcards for
	   hostnames, some only in subjectAltNames, and even their different
	   wildcard schemes are possible.

	   To ease the verification the following schemes are predefined:

	   ldap (rfc4513), pop3,imap,acap (rfc2995), nntp (rfc4642)
		   Simple wildcards in subjectAltNames are possible, e.g.
		   *.example.org matches www.example.org but not
		   lala.www.example.org. If nothing from subjectAltNames match
		   it checks against the common name, but there are no
		   wildcards allowed.

	   http (rfc2818), alias is www
		   Extended wildcards in subjectAltNames are possible, e.g.
		   *.example.org or even www*.example.org. Wildcards in the
		   common name are not allowed. The common name will be only
		   checked if no names are given in subjectAltNames.

	   smtp (rfc3207)
		   This RFC doesn't say much useful about the verification so
		   it just assumes that subjectAltNames are possible, but no
		   wildcards are possible anywhere.

	   The scheme can be given either by specifying the name for one of
	   the above predefined schemes, by using a callback (see below) or by
	   using a hash which can have the following keys and values:

	   check_cn:  0|'always'|'when_only'
		   Determines if the common name gets checked. If 'always' it
		   will always be checked (like in ldap), if 'when_only' it
		   will only be checked if no names are given in
		   subjectAltNames (like in http), for any other values the
		   common name will not be checked.

	   wildcards_in_alt: 0|'leftmost'|'anywhere'
		   Determines if and where wildcards in subjectAltNames are
		   possible. If 'leftmost' only cases like *.example.org will
		   be possible (like in ldap), for 'anywhere' www*.example.org
		   is possible too (like http), dangerous things like but
		   www.*.org or even '*' will not be allowed.

	   wildcards_in_cn: 0|'leftmost'|'anywhere'
		   Similar to wildcards_in_alt, but checks the common name.
		   There is no predefined scheme which allows wildcards in
		   common names.

	   If you give a subroutine for verification it will be called with
	   the arguments ($hostname,$commonName,@subjectAltNames), where
	   hostname is the name given for verification, commonName is the
	   result from peer_certificate('cn') and subjectAltNames is the
	   result from peer_certificate('subjectAltNames').

       errstr()
	   Returns the last error (in string form) that occurred. If you do
	   not have a real object to perform this method on, call
	   IO::Socket::SSL::errstr() instead.

	   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.

       opened()
	   This returns false if the socket could not be opened, 1 if the
	   socket could be opened and the SSL handshake was successful done
	   and -1 if the underlying IO::Handle is open, but the SSL handshake
	   failed.

       IO::Socket::SSL->start_SSL($socket, ... )
	   This will convert a glob reference or a socket that you provide to
	   an IO::Socket::SSL object.	 You may also pass parameters to
	   specify context or connection options as with a call to new().  If
	   you are using this function on an accept()ed socket, you must set
	   the parameter "SSL_server" to 1, i.e.
	   IO::Socket::SSL->start_SSL($socket, SSL_server => 1).  If you have
	   a class that inherits from IO::Socket::SSL and you want the $socket
	   to be blessed into your own class instead, use
	   MyClass->start_SSL($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.

       stop_SSL(...)
	   This is the opposite of start_SSL(), e.g. it will shutdown the SSL
	   connection and return to the class before start_SSL(). It gets the
	   same arguments as close(), in fact 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.

       IO::Socket::SSL->new_from_fd($fd, ...)
	   This will convert a socket identified via a file descriptor into an
	   SSL socket.	Note that the argument list does not include a "MODE"
	   argument; if you supply one, it will be thoughtfully ignored (for
	   compatibility with IO::Socket::INET).  Instead, a mode of '+<' is
	   assumed, and the file descriptor passed must be able to handle such
	   I/O because the initial SSL handshake requires bidirectional
	   communication.

       IO::Socket::SSL::set_default_context(...)
	   You may use this to make IO::Socket::SSL automatically re-use a
	   given context (unless specifically overridden in a call to new()).
	   It accepts one argument, which should be either an IO::Socket::SSL
	   object or an IO::Socket::SSL::SSL_Context object.   See the
	   SSL_reuse_ctx option of new() for more details.	Note that this
	   sets the default context globally, so use with caution (esp. in
	   mod_perl scripts).

       IO::Socket::SSL::set_default_session_cache(...)
	   You may use this to make IO::Socket::SSL automatically re-use a
	   given session cache (unless specifically overridden in a call to
	   new()).  It accepts one argument, which should be an
	   IO::Socket::SSL::Session_Cache object or similar (e.g something
	   which implements get_session and add_session like
	   IO::Socket::SSL::Session_Cache does).  See the SSL_session_cache
	   option of new() for more details.   Note that this sets the default
	   cache globally, so use with caution.

       IO::Socket::SSL::set_ctx_defaults(%args)
	   With this function one can set defaults for all SSL_* parameter
	   used for creation of the context, like the SSL_verify* parameter.

	   mode - set default SSL_verify_mode
	   callback - set default SSL_verify_callback
	   scheme - set default SSL_verifycn_scheme
	   name - set default SSL_verifycn_name
		   If not given and scheme is hash reference with key callback
		   it will be set to 'unknown'

       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:

       truncate
       stat
       ungetc
       setbuf
       setvbuf
       fdopen
       send/recv
	   Note that 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.

IPv6
       Support for IPv6 with IO::Socket::SSL is expected to work and basic
       testing is done.	 If IO::Socket::INET6 is available it will
       automatically use it instead of IO::Socket::INET4.

       Please be aware of the associated problems: If you give a name as a
       host and the host resolves to both IPv6 and IPv4 it will try IPv6 first
       and if there is no IPv6 connectivity it will fail.

       To avoid these problems you can either force IPv4 by specifying and
       AF_INET as the Domain (this is per socket) or load IO::Socket::SSL with
       the option 'inet4' (This is a global setting, e.g. affects all
       IO::Socket::SSL objects in the program).

RETURN VALUES
       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.

DEBUGGING
       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 3) to IO::Socket::SSL when
       calling it.  The debug level will also be propagated to
       Net::SSLeay::trace, see also Net::SSLeay:

       use IO::Socket::SSL qw(debug0);
	   No debugging (default).

       use IO::Socket::SSL qw(debug1);
	   Print out errors from IO::Socket::SSL and ciphers from Net::SSLeay.

       use IO::Socket::SSL qw(debug2);
	   Print also information about call flow from IO::Socket::SSL and
	   progress information from Net::SSLeay.

       use IO::Socket::SSL qw(debug3);
	   Print also some data dumps from IO::Socket::SSL and from
	   Net::SSLeay.

EXAMPLES
       See the 'example' directory.

BUGS
       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_callback 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.

       Non-blocking and timeouts (which are based on non-blocking) are not
       supported on Win32, because the underlying IO::Socket::INET does not
       support non-blocking on this platform.

LIMITATIONS
       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.

DEPRECATIONS
       The following functions are deprecated and are only retained for
       compatibility:

       context_init()
	 use the SSL_reuse_ctx option if you want to re-use a context

       socketToSSL() and socket_to_SSL()
	 use IO::Socket::SSL->start_SSL() instead

       kill_socket()
	 use close() instead

       get_peer_certificate()
	 use the 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()
	 use peer_certificate( 'issuer' ) instead

       subject_name()
	 use peer_certificate( 'subject' ) instead

       The following classes have been removed:

       SSL_SSL
	 (not that you should have been directly accessing this anyway):

       X509_Certificate
	 (but get_peer_certificate() will still Do The Right Thing)

SEE ALSO
       IO::Socket::INET, IO::Socket::INET6, Net::SSLeay.

AUTHORS
       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.

COPYRIGHT
       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.

Appendix: Using SSL
       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 Long of It (Detail)

       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.

       The Short of It (Summary)

       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>.

perl v5.10.0			  2011-01-18				SSL(3)
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