1IO::Socket::SSL(3) User Contributed Perl Documentation IO::Socket::SSL(3)
2
6 IO::Socket::SSL -- SSL sockets with IO::Socket interface
7
9 use strict;
10 use IO::Socket::SSL;
11 # simple HTTP client -----------------------------------------------
13 my $sock = IO::Socket::SSL->new(
14 # where to connect
15 PeerHost => "www.example.com",
16 PeerPort => "https",
17 # certificate verification
19 SSL_verify_mode => SSL_VERIFY_PEER,
20 # location of CA store
22 # need only be given if default store should not be used
23 SSL_ca_path => '/etc/ssl/certs', # typical CA path on Linux
24 SSL_ca_file => '/etc/ssl/cert.pem', # typical CA file on BSD
25 # easy hostname verification
27 SSL_verifycn_name => 'foo.bar', # defaults to PeerHost
28 SSL_verifycn_schema => 'http',
29 # SNI support
31 SSL_hostname => 'foo.bar', # defaults to PeerHost
32 ) or die "failed connect or ssl handshake: $!,$SSL_ERROR";
34 # send and receive over SSL connection
36 print $client "GET / HTTP/1.0\r\n\r\n";
37 print <$client>;
38 # simple server ----------------------------------------------------
40 my $server = IO::Socket::SSL->new(
41 # where to listen
42 LocalAddr => '127.0.0.1',
43 LocalPort => 8080,
44 Listen => 10,
45 # which certificate to offer
47 # with SNI support there can be different certificates per hostname
48 SSL_cert_file => 'cert.pem',
49 SSL_key_file => 'key.pem',
50 ) or die "failed to listen: $!";
51 # accept client
53 my $client = $server->accept or die
54 "failed to accept or ssl handshake: $!,$SSL_ERROR";
55 # Upgrade existing socket to SSL ---------------------------------
57 my $sock = IO::Socket::INET->new('imap.example.com:imap');
58 # ... receive greeting, send STARTTLS, receive ok ...
59 IO::Socket::SSL->start_SSL($sock,
60 SSL_verify_mode => SSL_VERIFY_PEER,
61 SSL_ca_path => '/etc/ssl/certs',
62 ...
63 ) or die "failed to upgrade to SSL: $SSL_ERROR";
64 # manual name verification, could also be done in start_SSL with
66 # SSL_verifycn_name etc
67 $client->verify_hostname( 'imap.example.com','imap' )
68 or die "hostname verification failed";
69 # all data are now SSL encrypted
71 print $sock ....
72
74 This module provides an interface to SSL sockets, similar to other
75 IO::Socket modules. Because of that, it can be used to make existing
76 programs using IO::Socket::INET or similar modules to provide SSL
77 encryption without much effort. IO::Socket::SSL supports all the extra
78 features that one needs to write a full-featured SSL client or server
79 application: multiple SSL contexts, cipher selection, certificate
80 verification, Server Name Indication (SNI), Next Protocol Negotiation
81 (NPN), SSL version selection and more.
82 If you have never used SSL before, you should read the appendix
84 labelled 'Using SSL' before attempting to use this module.
85 If you are trying to use it with threads see the BUGS section.
87
89 IO::Socket::SSL inherits from another IO::Socket module. The choice of
90 the super class depends on the installed modules:
91 · If IO::Socket::IP with at least version 0.20 is installed it will
93 use this module as super class, transparently providing IPv6 and
94 IPv4 support.
95 · If IO::Socket::INET6 is installed it will use this module as super
97 class, transparently providing IPv6 and IPv4 support.
98 · Otherwise it will fall back to IO::Socket::INET, which is a perl
100 core module. With IO::Socket::INET you only get IPv4 support.
101 Please be aware, that with the IPv6 capable super classes, it will
103 lookup first for the IPv6 address of a given hostname. If the resolver
104 provides an IPv6 address, but the host cannot be reached by IPv6, there
105 will be no automatic fallback to IPv4. To avoid these problems you can
106 either force IPv4 by specifying and AF_INET as "Domain" of the socket
107 or globally enforce IPv4 by loading IO::Socket::SSL with the option
108 'inet4'.
109 IO::Socket::SSL will provide all of the methods of its super class, but
111 sometimes it will override them to match the behavior expected from SSL
112 or to provide additional arguments.
113 The new or changed methods are described below, but please read also
115 the section about SSL specific error handling.
116 new(...)
118 Creates a new IO::Socket::SSL object. You may use all the friendly
119 options that came bundled with IO::Socket::INET, plus (optionally)
120 the ones that follow:
121 SSL_hostname
123 This can be given to specify the hostname used for SNI, which is
124 needed if you have multiple SSL hostnames on the same IP address.
125 If not given it will try to determine hostname from PeerAddr,
126 which will fail if only IP was given or if this argument is used
127 within start_SSL.
128 If you want to disable SNI set this argument to ''.
130 Currently only supported for the client side and will be ignored
132 for the server side.
133 See section "SNI Support" for details of SNI the support.
135 SSL_version
137 Sets the version of the SSL protocol used to transmit data.
138 'SSLv23' auto-negotiates between SSLv2 and SSLv3, while 'SSLv2',
139 'SSLv3', 'TLSv1', 'TLSv1_1' or 'TLSv1_2' restrict the protocol to
140 the specified version. All values are case-insensitive. Instead
141 of 'TLSv1_1' and 'TLSv1_2' one can also use 'TLSv11' and
142 'TLSv12'. Support for 'TLSv1_1' and 'TLSv1_2' requires recent
143 versions of Net::SSLeay and openssl.
144 You can limit to set of supported protocols by adding !version
146 separated by ':'.
147 The default SSL_version is defined by underlying cryptographic
149 library. E.g. 'SSLv23:!SSLv2' means, that SSLv2, SSLv3 and TLSv1
150 are supported for initial protocol handshakes, but SSLv2 will not
151 be accepted, leaving only SSLv3 and TLSv1. You can also use
152 !TLSv1_1 and !TLSv1_2 to disable TLS versions 1.1 and 1.2 while
153 allowing TLS version 1.0.
154 Setting the version instead to 'TLSv1' will probably break
156 interaction with lots of clients which start with SSLv2 and then
157 upgrade to TLSv1. On the other side some clients just close the
158 connection when they receive a TLS version 1.1 request. In this
159 case setting the version to 'SSLv23:!SSLv2:!TLSv1_1:!TLSv1_2'
160 might help.
161 SSL_cipher_list
163 If this option is set the cipher list for the connection will be
164 set to the given value, e.g. something like 'ALL:!LOW:!EXP:!ADH'.
165 Look into the OpenSSL documentation
166 (<http://www.openssl.org/docs/apps/ciphers.html#CIPHER_STRINGS>)
167 for more details.
168 If this option is not set or is set to '', OpenSSL builtin
170 default (whatever this is) will be used.
171 SSL_honor_cipher_order
173 If this option is true the cipher order the server specified is
174 used instead of the order proposed by the client. To mitigate
175 BEAST attack you might use something like
176 SSL_honor_cipher_order => 1,
178 SSL_cipher_list => 'RC4-SHA:ALL:!ADH:!LOW',
179 SSL_use_cert
181 If this is true, it forces IO::Socket::SSL to use a certificate
182 and key, even if you are setting up an SSL client. If this is
183 set to 0 (the default), then you will only need a certificate and
184 key if you are setting up a server.
185 SSL_use_cert will implicitly be set if SSL_server is set. For
187 convenience it is also set if it was not given but a cert was
188 given for use (SSL_cert_file or similar).
189 SSL_server
191 Set this option to a true value, if the socket should be used as
192 a server. If this is not explicitly set it is assumed, if the
193 Listen parameter is given when creating the socket.
194 SSL_cert_file
196 If your SSL certificate is not in the default place
197 (certs/server-cert.pem for servers, certs/client-cert.pem for
198 clients), then you should use this option to specify the location
199 of your certificate. A certificate is usually needed for an SSL
200 server, but might also be needed, if the client should authorize
201 itself with a certificate.
202 If your SSL server should be able to use different certificates
204 on the same IP address, depending on the name given by SNI, you
205 can use a hash reference instead of a file with "<hostname ="
206 cert_file>>.
207 Examples:
209 SSL_cert_file => 'mycert.pem'
211 SSL_cert_file => {
213 "foo.example.org" => 'foo.pem',
214 "bar.example.org" => 'bar.pem',
215 # used when nothing matches or client does not support SNI
216 '' => 'default.pem',
217 }
218 SSL_cert
220 This option can be used instead of "SSL_cert_file" to specify the
221 certificate.
222 Instead with a file the certificate is given as an X509* object
224 or array of X509* objects, where the first X509* is the internal
225 representation of the certificate while the following ones are
226 extra certificates. The option is useful if you create your
227 certificate dynamically (like in a SSL intercepting proxy) or get
228 it from a string (see openssl PEM_read_bio_X509 etc for getting a
229 X509* from a string).
230 For SNI support a hash reference can be given, similar to the
232 "SSL_cert_file" option.
233 SSL_key_file
235 If your RSA private key is not in default place
236 (certs/server-key.pem for servers, certs/client-key.pem for
237 clients), then this is the option that you would use to specify a
238 different location. Keys should be PEM formatted, and if they
239 are encrypted, you will be prompted to enter a password before
240 the socket is formed (unless you specified the SSL_passwd_cb
241 option).
242 For SNI support a hash reference can be given, similar to the
244 "SSL_cert_file" option.
245 SSL_key
247 This option can be used instead of "SSL_key" to specify the
248 certificate. Instead of a file an EVP_PKEY* should be given.
249 This option is useful if you don't have your key in a file but
250 create it dynamically or get it from a string (see openssl
251 PEM_read_bio_PrivateKey etc for getting a EVP_PKEY* from a
252 string).
253 For SNI support a hash reference can be given, similar to the
255 "SSL_key" option.
256 SSL_dh_file
258 If you want Diffie-Hellman key exchange you need to supply a
259 suitable file here or use the SSL_dh parameter. See dhparam
260 command in openssl for more information. To create a server
261 which provides perfect forward secrecy you need to either give
262 the DH parameters or (better, because faster) the ECDH curve.
263 SSL_dh
265 Like SSL_dh_file, but instead of giving a file you use a
266 preloaded or generated DH*.
267 SSL_ecdh_curve
269 If you want Elliptic Curve Diffie-Hellmann key exchange you need
270 to supply the OID or NID of a suitable curve (like 'prime256v1')
271 here. To create a server which provides perfect forward secrecy
272 you need to either give the DH parameters or (better, because
273 faster) the ECDH curve.
274 SSL_passwd_cb
276 If your private key is encrypted, you might not want the default
277 password prompt from Net::SSLeay. This option takes a reference
278 to a subroutine that should return the password required to
279 decrypt your private key.
280 SSL_ca_file
282 If you want to verify that the peer certificate has been signed
283 by a reputable certificate authority, then you can use this
284 option to locate the file containing the certificate(s) of the
285 reputable certificate authorities if it is not already in the
286 file certs/my-ca.pem or in a system-wide certificate authority
287 certificates store. If you definitely want no SSL_ca_file used
288 you should set it to undef.
289 SSL_ca_path
291 If you are unusually friendly with the OpenSSL documentation, you
292 might have set yourself up a directory containing several trusted
293 certificates as separate files as well as an index of the
294 certificates. If you want to use that directory for validation
295 purposes, and that directory is not ca/, then use this option to
296 point IO::Socket::SSL to the right place to look. If you
297 definitely want no SSL_ca_path used you should set it to undef.
298 SSL_verify_mode
300 This option sets the verification mode for the peer certificate.
301 You may combine SSL_VERIFY_PEER (verify_peer),
302 SSL_VERIFY_FAIL_IF_NO_PEER_CERT (fail verification if no peer
303 certificate exists; ignored for clients), SSL_VERIFY_CLIENT_ONCE
304 (verify client once; ignored for clients). See OpenSSL man page
305 for SSL_CTX_set_verify for more information.
306 The default is SSL_VERIFY_NONE for server (e.g. no check for
308 client certificate). For historical reasons the default for
309 client is currently also SSL_VERIFY_NONE, but this will change to
310 SSL_VERIFY_PEER in the near future. To aid transition a warning
311 is issued if the client is used with the default SSL_VERIFY_NONE,
312 unless SSL_verify_mode was explicitly set by the application.
313 SSL_verify_callback
315 If you want to verify certificates yourself, you can pass a sub
316 reference along with this parameter to do so. When the callback
317 is called, it will be passed:
318 1. a true/false value that indicates what OpenSSL thinks of the
320 certificate,
321 2. a C-style memory address of the certificate store,
322 3. a string containing the certificate's issuer attributes and
323 owner attributes, and
324 4. a string containing any errors encountered (0 if no errors).
325 5. a C-style memory address of the peer's own certificate
326 (convertible to PEM form with
327 Net::SSLeay::PEM_get_string_X509()).
328 The function should return 1 or 0, depending on whether it thinks
330 the certificate is valid or invalid. The default is to let
331 OpenSSL do all of the busy work.
332 The callback will be called for each element in the certificate
334 chain.
335 See the OpenSSL documentation for SSL_CTX_set_verify for more
337 information.
338 SSL_verifycn_scheme
340 Set the scheme used to automatically verify the hostname of the
341 peer. See the information about the verification schemes in
342 verify_hostname.
343 The default is undef, e.g. to not automatically verify the
345 hostname. If no verification is done the other SSL_verifycn_*
346 options have no effect, but you might still do manual
347 verification by calling verify_hostname.
348 SSL_verifycn_name
350 Set the name which is used in verification of hostname. If
351 SSL_verifycn_scheme is set and no SSL_verifycn_name is given it
352 will try to use the PeerHost and PeerAddr settings and fail if no
353 name can be determined.
354 Using PeerHost or PeerAddr works only if you create the
356 connection directly with "IO::Socket::SSL->new", if an
357 IO::Socket::INET object is upgraded with start_SSL the name has
358 to be given in SSL_verifycn_name.
359 SSL_check_crl
361 If you want to verify that the peer certificate has not been
362 revoked by the signing authority, set this value to true. OpenSSL
363 will search for the CRL in your SSL_ca_path, or use the file
364 specified by SSL_crl_file. See the Net::SSLeay documentation for
365 more details. Note that this functionality appears to be broken
366 with OpenSSL < v0.9.7b, so its use with lower versions will
367 result in an error.
368 SSL_crl_file
370 If you want to specify the CRL file to be used, set this value to
371 the pathname to be used. This must be used in addition to
372 setting SSL_check_crl.
373 SSL_reuse_ctx
375 If you have already set the above options (SSL_version through
376 SSL_check_crl; this does not include SSL_cipher_list yet) for a
377 previous instance of IO::Socket::SSL, then you can reuse the SSL
378 context of that instance by passing it as the value for the
379 SSL_reuse_ctx parameter. You may also create a new instance of
380 the IO::Socket::SSL::SSL_Context class, using any context options
381 that you desire without specifying connection options, and pass
382 that here instead.
383 If you use this option, all other context-related options that
385 you pass in the same call to new() will be ignored unless the
386 context supplied was invalid. Note that, contrary to versions of
387 IO::Socket::SSL below v0.90, a global SSL context will not be
388 implicitly used unless you use the set_default_context()
389 function.
390 SSL_create_ctx_callback
392 With this callback you can make individual settings to the
393 context after it got created and the default setup was done. The
394 callback will be called with the CTX object from Net::SSLeay as
395 the single argument.
396 Example for limiting the server session cache size:
398 SSL_create_ctx_callback => sub {
400 my $ctx = shift;
401 Net::SSLeay::CTX_sess_set_cache_size($ctx,128);
402 }
403 SSL_session_cache_size
405 If you make repeated connections to the same host/port and the
406 SSL renegotiation time is an issue, you can turn on client-side
407 session caching with this option by specifying a positive cache
408 size. For successive connections, pass the SSL_reuse_ctx option
409 to the new() calls (or use set_default_context()) to make use of
410 the cached sessions. The session cache size refers to the number
411 of unique host/port pairs that can be stored at one time; the
412 oldest sessions in the cache will be removed if new ones are
413 added.
414 This option does not effect the session cache a server has for
416 it's clients, e.g. it does not affect SSL objects with SSL_server
417 set.
418 SSL_session_cache
420 Specifies session cache object which should be used instead of
421 creating a new. Overrules SSL_session_cache_size. This option
422 is useful if you want to reuse the cache, but not the rest of the
423 context.
424 A session cache object can be created using
426 "IO::Socket::SSL::Session_Cache->new( cachesize )".
427 Use set_default_session_cache() to set a global cache object.
429 SSL_session_id_context
431 This gives an id for the servers session cache. It's necessary if
432 you want clients to connect with a client certificate. If not
433 given but SSL_verify_mode specifies the need for client
434 certificate a context unique id will be picked.
435 SSL_error_trap
437 When using the accept() or connect() methods, it may be the case
438 that the actual socket connection works but the SSL negotiation
439 fails, as in the case of an HTTP client connecting to an HTTPS
440 server. Passing a subroutine ref attached to this parameter
441 allows you to gain control of the orphaned socket instead of
442 having it be closed forcibly. The subroutine, if called, will be
443 passed two parameters: a reference to the socket on which the SSL
444 negotiation failed and the full text of the error message.
445 SSL_npn_protocols
447 If used on the server side it specifies list of protocols
448 advertised by SSL server as an array ref, e.g.
449 ['spdy/2','http1.1']. On the client side it specifies the
450 protocols offered by the client for NPN as an array ref. See
451 also method next_proto_negotiated.
452 Next Protocol Negotioation (NPN) is available with Net::SSLeay
454 1.46+ and openssl-1.0.1+. To check support you might call
455 "IO::Socket::SSL-"can_npn()>. If you use this option with an
456 unsupported Net::SSLeay/OpenSSL it will throw an error.
457 close(...)
459 There are a number of nasty traps that lie in wait if you are not
460 careful about using close(). The first of these will bite you if
461 you have been using shutdown() on your sockets. Since the SSL
462 protocol mandates that a SSL "close notify" message be sent before
463 the socket is closed, a shutdown() that closes the socket's write
464 channel will cause the close() call to hang. For a similar reason,
465 if you try to close a copy of a socket (as in a forking server) you
466 will affect the original socket as well. To get around these
467 problems, call close with an object-oriented syntax (e.g.
468 $socket->close(SSL_no_shutdown => 1)) and one or more of the
469 following parameters:
470 SSL_no_shutdown
472 If set to a true value, this option will make close() not use the
473 SSL_shutdown() call on the socket in question so that the close
474 operation can complete without problems if you have used
475 shutdown() or are working on a copy of a socket.
476 SSL_fast_shutdown
478 If set to true only a unidirectional shutdown will be done, e.g.
479 only the close_notify (see SSL_shutdown(3)) will be called.
480 Otherwise a bidirectional shutdown will be done. If used within
481 close() it defaults to true, if used within stop_SSL() it
482 defaults to false.
483 SSL_ctx_free
485 If you want to make sure that the SSL context of the socket is
486 destroyed when you close it, set this option to a true value.
487 peek(...)
489 This function has exactly the same syntax as sysread(), and
490 performs nearly the same task (reading data from the socket) but
491 will not advance the read position so that successive calls to
492 peek() with the same arguments will return the same results. This
493 function requires OpenSSL 0.9.6a or later to work.
494 pending()
496 This function will let you know how many bytes of data are
497 immediately ready for reading from the socket. This is especially
498 handy if you are doing reads on a blocking socket or just want to
499 know if new data has been sent over the socket.
500 get_cipher()
502 Returns the string form of the cipher that the IO::Socket::SSL
503 object is using.
504 dump_peer_certificate()
506 Returns a parsable string with select fields from the peer SSL
507 certificate. This method directly returns the result of the
508 dump_peer_certificate() method of Net::SSLeay.
509 peer_certificate($field)
511 If a peer certificate exists, this function can retrieve values
512 from it. If no field is given the internal representation of
513 certificate from Net::SSLeay is returned. The following fields can
514 be queried:
515 authority (alias issuer)
517 The certificate authority which signed the certificate.
518 owner (alias subject)
520 The owner of the certificate.
521 commonName (alias cn) - only for Net::SSLeay version >=1.30
523 The common name, usually the server name for SSL
524 certificates.
525 subjectAltNames - only for Net::SSLeay version >=1.33
527 Alternative names for the subject, usually different names
528 for the same server, like example.org, example.com,
529 *.example.com.
530 It returns a list of (typ,value) with typ GEN_DNS,
532 GEN_IPADD etc (these constants are exported from
533 IO::Socket::SSL). See
534 Net::SSLeay::X509_get_subjectAltNames.
535 get_servername
537 This gives the name requested by the client if Server Name
538 Indication (SNI) was used.
539 verify_hostname($hostname,$scheme)
541 This verifies the given hostname against the peer certificate using
542 the given scheme. Hostname is usually what you specify within the
543 PeerAddr.
544 Verification of hostname against a certificate is different between
546 various applications and RFCs. Some scheme allow wildcards for
547 hostnames, some only in subjectAltNames, and even their different
548 wildcard schemes are possible.
549 To ease the verification the following schemes are predefined:
551 ldap (rfc4513), pop3,imap,acap (rfc2995), nntp (rfc4642)
553 Simple wildcards in subjectAltNames are possible, e.g.
554 *.example.org matches www.example.org but not
555 lala.www.example.org. If nothing from subjectAltNames match
556 it checks against the common name, but there are no
557 wildcards allowed.
558 http (rfc2818), alias is www
560 Extended wildcards in subjectAltNames and common name are
561 possible, e.g. *.example.org or even www*.example.org. The
562 common name will be only checked if no names are given in
563 subjectAltNames.
564 smtp (rfc3207)
566 This RFC doesn't say much useful about the verification so
567 it just assumes that subjectAltNames are possible, but no
568 wildcards are possible anywhere.
569 none No verification will be done. Actually is does not make
571 any sense to call verify_hostname in this case.
572 The scheme can be given either by specifying the name for one of
574 the above predefined schemes, or by using a hash which can have the
575 following keys and values:
576 check_cn: 0|'always'|'when_only'
578 Determines if the common name gets checked. If 'always' it
579 will always be checked (like in ldap), if 'when_only' it
580 will only be checked if no names are given in
581 subjectAltNames (like in http), for any other values the
582 common name will not be checked.
583 wildcards_in_alt: 0|'leftmost'|'anywhere'
585 Determines if and where wildcards in subjectAltNames are
586 possible. If 'leftmost' only cases like *.example.org will
587 be possible (like in ldap), for 'anywhere' www*.example.org
588 is possible too (like http), dangerous things like but
589 www.*.org or even '*' will not be allowed.
590 wildcards_in_cn: 0|'leftmost'|'anywhere'
592 Similar to wildcards_in_alt, but checks the common name.
593 There is no predefined scheme which allows wildcards in
594 common names.
595 callback: \&coderef
597 If you give a subroutine for verification it will be called
598 with the arguments
599 ($hostname,$commonName,@subjectAltNames), where hostname is
600 the name given for verification, commonName is the result
601 from peer_certificate('cn') and subjectAltNames is the
602 result from peer_certificate('subjectAltNames').
603 All other arguments for the verification scheme will be
605 ignored in this case.
606 next_proto_negotiated()
608 This method returns the name of negotiated protocol - e.g.
609 'http/1.1'. It works for both client and server side of SSL
610 connection.
611 NPN support is available with Net::SSLeay 1.46+ and openssl-1.0.1+.
613 To check support you might call "IO::Socket::SSL-"can_npn()>.
614 errstr()
616 Returns the last error (in string form) that occurred. If you do
617 not have a real object to perform this method on, call
618 IO::Socket::SSL::errstr() instead.
619 For read and write errors on non-blocking sockets, this method may
621 include the string "SSL wants a read first!" or "SSL wants a write
622 first!" meaning that the other side is expecting to read from or
623 write to the socket and wants to be satisfied before you get to do
624 anything. But with version 0.98 you are better comparing the global
625 exported variable $SSL_ERROR against the exported symbols
626 SSL_WANT_READ and SSL_WANT_WRITE.
627 opened()
629 This returns false if the socket could not be opened, 1 if the
630 socket could be opened and the SSL handshake was successful done
631 and -1 if the underlying IO::Handle is open, but the SSL handshake
632 failed.
633 IO::Socket::SSL->start_SSL($socket, ... )
635 This will convert a glob reference or a socket that you provide to
636 an IO::Socket::SSL object. You may also pass parameters to
637 specify context or connection options as with a call to new(). If
638 you are using this function on an accept()ed socket, you must set
639 the parameter "SSL_server" to 1, i.e.
640 IO::Socket::SSL->start_SSL($socket, SSL_server => 1). If you have
641 a class that inherits from IO::Socket::SSL and you want the $socket
642 to be blessed into your own class instead, use
643 MyClass->start_SSL($socket) to achieve the desired effect.
644 Note that if start_SSL() fails in SSL negotiation, $socket will
646 remain blessed in its original class. For non-blocking sockets
647 you better just upgrade the socket to IO::Socket::SSL and call
648 accept_SSL or connect_SSL and the upgraded object. To just upgrade
649 the socket set SSL_startHandshake explicitly to 0. If you call
650 start_SSL w/o this parameter it will revert to blocking behavior
651 for accept_SSL and connect_SSL.
652 If given the parameter "Timeout" it will stop if after the timeout
654 no SSL connection was established. This parameter is only used for
655 blocking sockets, if it is not given the default Timeout from the
656 underlying IO::Socket will be used.
657 stop_SSL(...)
659 This is the opposite of start_SSL(), e.g. it will shutdown the SSL
660 connection and return to the class before start_SSL(). It gets the
661 same arguments as close(), in fact close() calls stop_SSL() (but
662 without downgrading the class).
663 Will return true if it succeeded and undef if failed. This might be
665 the case for non-blocking sockets. In this case $! is set to EAGAIN
666 and the ssl error to SSL_WANT_READ or SSL_WANT_WRITE. In this case
667 the call should be retried again with the same arguments once the
668 socket is ready is until it succeeds.
669 IO::Socket::SSL->new_from_fd($fd, ...)
671 This will convert a socket identified via a file descriptor into an
672 SSL socket. Note that the argument list does not include a "MODE"
673 argument; if you supply one, it will be thoughtfully ignored (for
674 compatibility with IO::Socket::INET). Instead, a mode of '+<' is
675 assumed, and the file descriptor passed must be able to handle such
676 I/O because the initial SSL handshake requires bidirectional
677 communication.
678 IO::Socket::SSL::set_default_context(...)
680 You may use this to make IO::Socket::SSL automatically re-use a
681 given context (unless specifically overridden in a call to new()).
682 It accepts one argument, which should be either an IO::Socket::SSL
683 object or an IO::Socket::SSL::SSL_Context object. See the
684 SSL_reuse_ctx option of new() for more details. Note that this
685 sets the default context globally, so use with caution (esp. in
686 mod_perl scripts).
687 IO::Socket::SSL::set_default_session_cache(...)
689 You may use this to make IO::Socket::SSL automatically re-use a
690 given session cache (unless specifically overridden in a call to
691 new()). It accepts one argument, which should be an
692 IO::Socket::SSL::Session_Cache object or similar (e.g something
693 which implements get_session and add_session like
694 IO::Socket::SSL::Session_Cache does). See the SSL_session_cache
695 option of new() for more details. Note that this sets the default
696 cache globally, so use with caution.
697 IO::Socket::SSL::set_defaults(%args)
699 With this function one can set defaults for all SSL_* parameter
700 used for creation of the context, like the SSL_verify* parameter.
701 mode - set default SSL_verify_mode
703 callback - set default SSL_verify_callback
704 scheme - set default SSL_verifycn_scheme
705 name - set default SSL_verifycn_name
706 If not given and scheme is hash reference with key callback
707 it will be set to 'unknown'
708 The following methods are unsupported (not to mention futile!) and
710 IO::Socket::SSL will emit a large CROAK() if you are silly enough to
711 use them:
712 truncate
714 stat
715 ungetc
716 setbuf
717 setvbuf
718 fdopen
719 send/recv
720 Note that send() and recv() cannot be reliably trapped by a tied
721 filehandle (such as that used by IO::Socket::SSL) and so may send
722 unencrypted data over the socket. Object-oriented calls to these
723 functions will fail, telling you to use the print/printf/syswrite
724 and read/sysread families instead.
725
727 If an SSL specific error occurs the global variable $SSL_ERROR will be
728 set. If the error occurred on an existing SSL socket the method
729 "errstr" will give access to the latest socket specific error. Both
730 $SSL_ERROR and "errstr" method give a dualvar similar to $!, e.g.
731 providing an error number in numeric context or an error description in
732 string context.
733
735 If you have a non-blocking socket, the expected behavior on read,
736 write, accept or connect is to set $! to EAGAIN if the operation can
737 not be completed immediately.
738 With SSL there are cases, like with SSL handshakes, where the write
740 operation can not be completed until it can read from the socket or
741 vice versa. In these cases $! is set to EGAIN like expected, and
742 additionally $SSL_ERROR is set to either SSL_WANT_READ or
743 SSL_WANT_WRITE. Thus if you get EAGAIN on a SSL socket you must check
744 $SSL_ERROR for SSL_WANT_* and adapt your event mask accordingly.
745 Using readline on non-blocking sockets does not make much sense and I
747 would advise against using it. And, while the behavior is not
748 documented for other IO::Socket classes, it will try to emulate the
749 behavior seen there, e.g. to return the received data instead of
750 blocking, even if the line is not complete. If an unrecoverable error
751 occurs it will return nothing, even if it already received some data.
752
754 Newer extensions to SSL can distinguish between multiple hostnames on
755 the same IP address using Server Name Indication (SNI).
756 Support for SNI on the client side was added somewhere in the OpenSSL
758 0.9.8 series, but only with 1.0 a bug was fixed when the server could
759 not decide about its hostname. Therefore client side SNI is only
760 supported with OpenSSL 1.0 or higher in IO::Socket::SSL. With a
761 supported version, SNI is used automatically on the client side, if it
762 can determine the hostname from "PeerAddr" or "PeerHost". On
763 unsupported OpenSSL versions it will silently not use SNI. The
764 hostname can also be given explicitly given with "SSL_hostname", but in
765 this case it will throw in error, if SNI is not supported. To check
766 for support you might call "IO::Socket::SSL-"can_client_sni()>.
767 On the server side earlier versions of OpenSSL are supported, but only
769 together with Net::SSLeay version >= 1.50. To check for support you
770 might call "IO::Socket::SSL-"can_server_sni()>. If server side SNI is
771 supported, you might specify different certificates per host with
772 "SSL_cert*" and "SSL_key*", and check the requested name using
773 "get_servername".
774
776 A few changes have gone into IO::Socket::SSL v0.93 and later with
777 respect to return values. The behavior on success remains unchanged,
778 but for all functions, the return value on error is now an empty
779 list. Therefore, the return value will be false in all contexts, but
780 those who have been using the return values as arguments to subroutines
781 (like "mysub(IO::Socket::SSL(...)-"new, ...)>) may run into problems.
782 The moral of the story: always check the return values of these
783 functions before using them in any way that you consider meaningful.
784
786 If you are having problems using IO::Socket::SSL despite the fact that
787 can recite backwards the section of this documentation labelled 'Using
788 SSL', you should try enabling debugging. To specify the debug level,
789 pass 'debug#' (where # is a number from 0 to 3) to IO::Socket::SSL when
790 calling it. The debug level will also be propagated to
791 Net::SSLeay::trace, see also Net::SSLeay:
792 use IO::Socket::SSL qw(debug0);
794 No debugging (default).
795 use IO::Socket::SSL qw(debug1);
797 Print out errors from IO::Socket::SSL and ciphers from Net::SSLeay.
798 use IO::Socket::SSL qw(debug2);
800 Print also information about call flow from IO::Socket::SSL and
801 progress information from Net::SSLeay.
802 use IO::Socket::SSL qw(debug3);
804 Print also some data dumps from IO::Socket::SSL and from
805 Net::SSLeay.
806
808 See the 'example' directory.
809
811 IO::Socket::SSL depends on Net::SSLeay. Up to version 1.43 of
812 Net::SSLeay it was not thread safe, although it did probably work if
813 you did not use SSL_verify_callback and SSL_password_cb.
814 If you use IO::Socket::SSL together with threads you should load it
816 (e.g. use or require) inside the main thread before creating any other
817 threads which use it. This way it is much faster because it will be
818 initialized only once. Also there are reports that it might crash the
819 other way.
820 Creating an IO::Socket::SSL object in one thread and closing it in
822 another thread will not work.
823 IO::Socket::SSL does not work together with
825 Storable::fd_retrieve/fd_store. See BUGS file for more information and
826 how to work around the problem.
827 Non-blocking and timeouts (which are based on non-blocking) are not
829 supported on Win32, because the underlying IO::Socket::INET does not
830 support non-blocking on this platform.
831 If you have a server and it looks like you have a memory leak you might
833 check the size of your session cache. Default for Net::SSLeay seems to
834 be 20480, see the example for SSL_create_ctx_callback for how to limit
835 it.
836 The default for SSL_verify_mode on the client is currently
838 SSL_VERIFY_NONE, which is a very bad idea, thus the default will change
839 in the near future. See documentation for SSL_verify_mode for more
840 information.
841
843 IO::Socket::SSL uses Net::SSLeay as the shiny interface to OpenSSL,
844 which is the shiny interface to the ugliness of SSL. As a result, you
845 will need both Net::SSLeay and OpenSSL on your computer before using
846 this module.
847 If you have Scalar::Util (standard with Perl 5.8.0 and above) or
849 WeakRef, IO::Socket::SSL sockets will auto-close when they go out of
850 scope, just like IO::Socket::INET sockets. If you do not have one
851 of these modules, then IO::Socket::SSL sockets will stay open until the
852 program ends or you explicitly close them. This is due to the fact
853 that a circular reference is required to make IO::Socket::SSL sockets
854 act simultaneously like objects and glob references.
855
857 The following functions are deprecated and are only retained for
858 compatibility:
859 context_init()
861 use the SSL_reuse_ctx option if you want to re-use a context
862 socketToSSL() and socket_to_SSL()
864 use IO::Socket::SSL->start_SSL() instead
865 kill_socket()
867 use close() instead
868 get_peer_certificate()
870 use the peer_certificate() function instead. Used to return
871 X509_Certificate with methods subject_name and issuer_name. Now
872 simply returns $self which has these methods (although deprecated).
873 issuer_name()
875 use peer_certificate( 'issuer' ) instead
876 subject_name()
878 use peer_certificate( 'subject' ) instead
879
881 IO::Socket::INET, IO::Socket::INET6, IO::Socket::IP, Net::SSLeay.
882
884 Steffen Ullrich, <steffen at genua.de> is the current maintainer.
885 Peter Behroozi, <behrooz at fas.harvard.edu> (Note the lack of an "i"
887 at the end of "behrooz")
888 Marko Asplund, <marko.asplund at kronodoc.fi>, was the original author
890 of IO::Socket::SSL.
891 Patches incorporated from various people, see file Changes.
893
895 The original versions of this module are Copyright (C) 1999-2002 Marko
896 Asplund.
897 The rewrite of this module is Copyright (C) 2002-2005 Peter Behroozi.
899 Versions 0.98 and newer are Copyright (C) 2006-2013 Steffen Ullrich.
901 This module is free software; you can redistribute it and/or modify it
903 under the same terms as Perl itself.
904
906 If you are unfamiliar with the way OpenSSL works, good references may
907 be found in both the book "Network Security with OpenSSL" (Oreilly &
908 Assoc.) and the web site
909 <http://www.tldp.org/HOWTO/SSL-Certificates-HOWTO/>. Read on for a
910 quick overview.
911 The Long of It (Detail)
913 The usual reason for using SSL is to keep your data safe. This means
914 that not only do you have to encrypt the data while it is being
915 transported over a network, but you also have to make sure that the
916 right person gets the data. To accomplish this with SSL, you have to
917 use certificates. A certificate closely resembles a Government-issued
918 ID (at least in places where you can trust them). The ID contains
919 some sort of identifying information such as a name and address, and is
920 usually stamped with a seal of Government Approval. Theoretically,
921 this means that you may trust the information on the card and do
922 business with the owner of the card. The same ideas apply to SSL
923 certificates, which have some identifying information and are "stamped"
924 [most people refer to this as signing instead] by someone (a
925 Certificate Authority) who you trust will adequately verify the
926 identifying information. In this case, because of some clever number
927 theory, it is extremely difficult to falsify the stamping
928 process. Another useful consequence of number theory is that the
929 certificate is linked to the encryption process, so you may encrypt
930 data (using information on the certificate) that only the certificate
931 owner can decrypt.
932 What does this mean for you? It means that at least one person in the
934 party has to have an ID to get drinks :-). Seriously, it means that
935 one of the people communicating has to have a certificate to ensure
936 that your data is safe. For client/server interactions, the server
937 must always have a certificate. If the server wants to verify that
938 the client is safe, then the client must also have a personal
939 certificate. To verify that a certificate is safe, one compares the
940 stamped "seal" [commonly called an encrypted digest/hash/signature] on
941 the certificate with the official "seal" of the Certificate Authority
942 to make sure that they are the same. To do this, you will need the
943 [unfortunately named] certificate of the Certificate Authority. With
944 all these in hand, you can set up a SSL connection and be reasonably
945 confident that no-one is reading your data.
946 The Short of It (Summary)
948 For servers, you will need to generate a cryptographic private key and
949 a certificate request. You will need to send the certificate request
950 to a Certificate Authority to get a real certificate back, after which
951 you can start serving people. For clients, you will not need anything
952 unless the server wants validation, in which case you will also need a
953 private key and a real certificate. For more information about how
954 to get these, see <http://www.modssl.org/docs/2.8/ssl_faq.html#ToC24>.
955perl v5.16.3 2018-04-10 IO::Socket::SSL(3)