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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_hostname
This can be given to specifiy the hostname used for SNI, which is needed if you have multiple
SSL hostnames on the same IP address. If not given it will try to determine hostname from
PeerAddr, which will fail if only IP was given or if this argument is used within start_SSL.
If you want to disable SNI set this argument to ''.
Currently only supported for the client side and will be ignored for the server side.
SSL_version
Sets the version of the SSL protocol used to transmit data. 'SSLv23' auto-negotiates between
SSLv2 and SSLv3, while 'SSLv2', 'SSLv3' or 'TLSv1' restrict the protocol to the specified
version. All values are case-insensitive.
You can limit to set of supported protocols by adding !version separated by ':'.
The default SSL_version is 'SSLv23:!SSLv2' which means, that SSLv2, SSLv3 and TLSv1 are
supported for initial protocol handshakes, but SSLv2 will not be accepted, leaving only SSLv3
and TLSv1. You can also use !TLSv11 and !TLSv12 to disable TLS versions 1.1 and 1.2 while
allowing TLS version 1.0.
Setting the version instead to 'TLSv1' will probably break interaction with lots of clients
which start with SSLv2 and then upgrade to TLSv1. On the other side some clients just close the
connection when they receive a TLS version 1.1 request. In this case setting the version to
'SSLv23:!SSLv2:!TLSv11:!TLSv12' might help.
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 set 'ALL:!LOW' will be used. To use OpenSSL builtin default (whatever
this is) set it to ''.
SSL_honor_cipher_order
If this option is true the cipher order the server specified is used instead of the order
proposed by the client. To mitigate BEAST attack you might use something like
SSL_honor_cipher_order => 1,
SSL_cipher_list => 'RC4-SHA:ALL:!ADH:!LOW',
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_X5_9()).
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. If no verification is
done the other SSL_verifycn_* options have no effect, but you might still do manual
verification by calling verify_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 can 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_create_ctx_callback
With this callback you can make individual settings to the context after it got created and the
default setup was done. The callback will be called with the CTX object from Net::SSLeay as
the single argument.
Example for limiting the server session cache size:
SSL_create_ctx_callback => sub {
my $ctx = shift;
Net::SSLeay::CTX_sess_set_cache_size($ctx,128);
}
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.
This option does not effect the session cache a server has for it's clients, e.g. it does not
affect SSL objects with SSL_server set.
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_session_id_context
This gives an id for the servers session cache. It's necessary if you want clients to connect
with a client certificate. If not given but SSL_verify_mode specifies the need for client
certificate a context unique id will be picked.
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.
SSL_npn_protocols
If used on the server side it specifies list of protocols advertised by SSL server as an array
ref, e.g. ['spdy/2','http1.1']. On the client side it specifies the protocols offered by the
client for NPN as an array ref. See also method next_proto_negotiated.
Next Protocol Negotioation (NPN) is available with Net::SSLeay 1.46+ and openssl-1.0.1+.
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 and common name are possible, e.g. *.example.org
or even www*.example.org. 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.
none No verification will be done. Actually is does not make any sense to call
verify_hostname in this case.
The scheme can be given either by specifying the name for one of the above predefined schemes, 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.
callback: \&coderef
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').
All other arguments for the verification scheme will be ignored in this case.
next_proto_negotiated()
This method returns the name of negotiated protocol - e.g. 'http/1.1'. It works for both client
and server side of SSL connection.
NPN support is available with Net::SSLeay 1.46+ and openssl-1.0.1+.
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 depends on Net::SSLeay. Up to version 1.43 of Net::SSLeay it was not thread safe,
although it did probably work if you did not use SSL_verify_callback and SSL_password_cb.
Creating an IO::Socket::SSL object in one thread and closing it in another thread will not work.
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.
If you have a server and it looks like you have a memory leak you might check the size of your
session cache. Default for Net::SSLeay seems to be 20480, see the example for SSL_create_ctx_callback
for how to limit it.
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/ <http://www .tldp.org/HOWTO/SSL-сертификаты -
ПРАКТИЧЕСКОЕ РУКОВОДСТВО />. 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 v5.16.2 2012-10-04 SSL(3)
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