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 client
13 my $cl = IO::Socket::SSL->new('www.google.com:443');
14 print $cl "GET / HTTP/1.0\r\n\r\n";
15 print <$cl>;
16 # simple server
18 my $srv = IO::Socket::SSL->new(
19 LocalAddr => '0.0.0.0:1234',
20 Listen => 10,
21 SSL_cert_file => 'server-cert.pem',
22 SSL_key_file => 'server-key.pem',
23 );
24 $srv->accept;
25
27 IO::Socket::SSL makes using SSL/TLS much easier by wrapping the
28 necessary functionality into the familiar IO::Socket interface and
29 providing secure defaults whenever possible. This way, existing
30 applications can be made SSL-aware without much effort, at least if you
31 do blocking I/O and don't use select or poll.
32 But, under the hood, SSL is a complex beast. So there are lots of
34 methods to make it do what you need if the default behavior is not
35 adequate. Because it is easy to inadvertently introduce critical
36 security bugs or just hard to debug problems, I would recommend
37 studying the following documentation carefully.
38 The documentation consists of the following parts:
40 • "Essential Information About SSL/TLS"
42 • "Basic SSL Client"
44 • "Basic SSL Server"
46 • "Common Usage Errors"
48 • "Common Problems with SSL"
50 • "Using Non-Blocking Sockets"
52 • "Advanced Usage"
54 • "Integration Into Own Modules"
56 • "Description Of Methods"
58 Additional documentation can be found in
60 • IO::Socket::SSL::Intercept - Doing Man-In-The-Middle with SSL
62 • IO::Socket::SSL::Utils - Useful functions for certificates etc
64
66 SSL (Secure Socket Layer) or its successor TLS (Transport Layer
67 Security) are protocols to facilitate end-to-end security. These
68 protocols are used when accessing web sites (https), delivering or
69 retrieving email, and in lots of other use cases. In the following
70 documentation we will refer to both SSL and TLS as simply 'SSL'.
71 SSL enables end-to-end security by providing two essential functions:
73 Encryption
75 This part encrypts the data for transit between the communicating
76 parties, so that nobody in between can read them. It also provides
77 tamper resistance so that nobody in between can manipulate the
78 data.
79 Identification
81 This part makes sure that you talk to the right peer. If the
82 identification is done incorrectly it is easy to mount man-in-the-
83 middle attacks, e.g. if Alice wants to talk to Bob it would be
84 possible for Mallory to put itself in the middle, so that Alice
85 talks to Mallory and Mallory to Bob. All the data would still be
86 encrypted, but not end-to-end between Alice and Bob, but only
87 between Alice and Mallory and then between Mallory and Bob. Thus
88 Mallory would be able to read and modify all traffic between Alice
89 and Bob.
90 Identification is the part which is the hardest to understand and the
92 easiest to get wrong.
93 With SSL, the Identification is usually done with certificates inside a
95 PKI (Public Key Infrastructure). These Certificates are comparable to
96 an identity card, which contains information about the owner of the
97 card. The card then is somehow signed by the issuer of the card, the CA
98 (Certificate Agency).
99 To verify the identity of the peer the following must be done inside
101 SSL:
102 • Get the certificate from the peer. If the peer does not present a
104 certificate we cannot verify it.
105 • Check if we trust the certificate, e.g. make sure it's not a
107 forgery.
108 We believe that a certificate is not a fake if we either know the
110 certificate already or if we trust the issuer (the CA) and can
111 verify the issuers signature on the certificate. In reality there
112 is often a hierarchy of certificate agencies and we only directly
113 trust the root of this hierarchy. In this case the peer not only
114 sends his own certificate, but also all intermediate certificates.
115 Verification will be done by building a trust path from the trusted
116 root up to the peers certificate and checking in each step if the
117 we can verify the issuer's signature.
118 This step often causes problems because the client does not know
120 the necessary trusted root certificates. These are usually stored
121 in a system dependent CA store, but often the browsers have their
122 own CA store.
123 • Check if the certificate is still valid. Each certificate has a
125 lifetime and should not be used after that time because it might be
126 compromised or the underlying cryptography got broken in the mean
127 time.
128 • Check if the subject of the certificate matches the peer. This is
130 like comparing the picture on the identity card against the person
131 representing the identity card.
132 When connecting to a server this is usually done by comparing the
134 hostname used for connecting against the names represented in the
135 certificate. A certificate might contain multiple names or
136 wildcards, so that it can be used for multiple hosts (e.g.
137 *.example.com and *.example.org).
138 Although nobody sane would accept an identity card where the
140 picture does not match the person we see, it is a common
141 implementation error with SSL to omit this check or get it wrong.
142 • Check if the certificate was revoked by the issuer. This might be
144 the case if the certificate was compromised somehow and now
145 somebody else might use it to claim the wrong identity. Such
146 revocations happened a lot after the heartbleed attack.
147 For SSL there are two ways to verify a revocation, CRL and OCSP.
149 With CRLs (Certificate Revocation List) the CA provides a list of
150 serial numbers for revoked certificates. The client somehow has to
151 download the list (which can be huge) and keep it up to date. With
152 OCSP (Online Certificate Status Protocol) the client can check a
153 single certificate directly by asking the issuer.
154 Revocation is the hardest part of the verification and none of
156 today's browsers get it fully correct. But, they are still better
157 than most other implementations which don't implement revocation
158 checks or leave the hard parts to the developer.
159 When accessing a web site with SSL or delivering mail in a secure way
161 the identity is usually only checked one way, e.g. the client wants to
162 make sure it talks to the right server, but the server usually does not
163 care which client it talks to. But, sometimes the server wants to
164 identify the client too and will request a certificate from the client
165 which the server must verify in a similar way.
166
168 A basic SSL client is simple:
169 my $client = IO::Socket::SSL->new('www.example.com:443')
171 or die "error=$!, ssl_error=$SSL_ERROR";
172 This will take the OpenSSL default CA store as the store for the
174 trusted CA. This usually works on UNIX systems. If there are no
175 certificates in the store it will try use Mozilla::CA which provides
176 the default CAs of Firefox.
177 In the default settings, IO::Socket::SSL will use a safer cipher set
179 and SSL version, do a proper hostname check against the certificate,
180 and use SNI (server name indication) to send the hostname inside the
181 SSL handshake. This is necessary to work with servers which have
182 different certificates behind the same IP address. It will also check
183 the revocation of the certificate with OCSP, but currently only if the
184 server provides OCSP stapling (for deeper checks see "ocsp_resolver"
185 method).
186 Lots of options can be used to change ciphers, SSL version, location of
188 CA and much more. See documentation of methods for details.
189 With protocols like SMTP it is necessary to upgrade an existing socket
191 to SSL. This can be done like this:
192 my $client = IO::Socket::INET->new('mx.example.com:25') or die $!;
194 # .. read greeting from server
195 # .. send EHLO and read response
196 # .. send STARTTLS command and read response
197 # .. if response was successful we can upgrade the socket to SSL now:
198 IO::Socket::SSL->start_SSL($client,
199 # explicitly set hostname we should use for SNI
200 SSL_hostname => 'mx.example.com'
201 ) or die $SSL_ERROR;
202 A more complete example for a simple HTTP client:
204 my $client = IO::Socket::SSL->new(
206 # where to connect
207 PeerHost => "www.example.com",
208 PeerPort => "https",
209 # certificate verification - VERIFY_PEER is default
211 SSL_verify_mode => SSL_VERIFY_PEER,
212 # location of CA store
214 # need only be given if default store should not be used
215 SSL_ca_path => '/etc/ssl/certs', # typical CA path on Linux
216 SSL_ca_file => '/etc/ssl/cert.pem', # typical CA file on BSD
217 # or just use default path on system:
219 IO::Socket::SSL::default_ca(), # either explicitly
220 # or implicitly by not giving SSL_ca_*
221 # easy hostname verification
223 # It will use PeerHost as default name a verification
224 # scheme as default, which is safe enough for most purposes.
225 SSL_verifycn_name => 'foo.bar',
226 SSL_verifycn_scheme => 'http',
227 # SNI support - defaults to PeerHost
229 SSL_hostname => 'foo.bar',
230 ) or die "failed connect or ssl handshake: $!,$SSL_ERROR";
232 # send and receive over SSL connection
234 print $client "GET / HTTP/1.0\r\n\r\n";
235 print <$client>;
236 And to do revocation checks with OCSP (only available with OpenSSL
238 1.0.0 or higher and Net::SSLeay 1.59 or higher):
239 # default will try OCSP stapling and check only leaf certificate
241 my $client = IO::Socket::SSL->new($dst);
242 # better yet: require checking of full chain
244 my $client = IO::Socket::SSL->new(
245 PeerAddr => $dst,
246 SSL_ocsp_mode => SSL_OCSP_FULL_CHAIN,
247 );
248 # even better: make OCSP errors fatal
250 # (this will probably fail with lots of sites because of bad OCSP setups)
251 # also use common OCSP response cache
252 my $ocsp_cache = IO::Socket::SSL::OCSP_Cache->new;
253 my $client = IO::Socket::SSL->new(
254 PeerAddr => $dst,
255 SSL_ocsp_mode => SSL_OCSP_FULL_CHAIN|SSL_OCSP_FAIL_HARD,
256 SSL_ocsp_cache => $ocsp_cache,
257 );
258 # disable OCSP stapling in case server has problems with it
260 my $client = IO::Socket::SSL->new(
261 PeerAddr => $dst,
262 SSL_ocsp_mode => SSL_OCSP_NO_STAPLE,
263 );
264 # check any certificates which are not yet checked by OCSP stapling or
266 # where we have already cached results. For your own resolving combine
267 # $ocsp->requests with $ocsp->add_response(uri,response).
268 my $ocsp = $client->ocsp_resolver();
269 my $errors = $ocsp->resolve_blocking();
270 if ($errors) {
271 warn "OCSP verification failed: $errors";
272 close($client);
273 }
274
276 A basic SSL server looks similar to other IO::Socket servers, only that
277 it also contains settings for certificate and key:
278 # simple server
280 my $server = IO::Socket::SSL->new(
281 # where to listen
282 LocalAddr => '127.0.0.1',
283 LocalPort => 8080,
284 Listen => 10,
285 # which certificate to offer
287 # with SNI support there can be different certificates per hostname
288 SSL_cert_file => 'cert.pem',
289 SSL_key_file => 'key.pem',
290 ) or die "failed to listen: $!";
291 # accept client
293 my $client = $server->accept or die
294 "failed to accept or ssl handshake: $!,$SSL_ERROR";
295 This will automatically use a secure set of ciphers and SSL version and
297 also supports Forward Secrecy with (Elliptic-Curve) Diffie-Hellmann Key
298 Exchange.
299 If you are doing a forking or threading server, we recommend that you
301 do the SSL handshake inside the new process/thread so that the master
302 is free for new connections. We recommend this because a client with
303 improper or slow SSL handshake could make the server block in the
304 handshake which would be bad to do on the listening socket:
305 # inet server
307 my $server = IO::Socket::INET->new(
308 # where to listen
309 LocalAddr => '127.0.0.1',
310 LocalPort => 8080,
311 Listen => 10,
312 );
313 # accept client
315 my $client = $server->accept or die;
316 # SSL upgrade client (in new process/thread)
318 IO::Socket::SSL->start_SSL($client,
319 SSL_server => 1,
320 SSL_cert_file => 'cert.pem',
321 SSL_key_file => 'key.pem',
322 ) or die "failed to ssl handshake: $SSL_ERROR";
323 Like with normal sockets, neither forking nor threading servers scale
325 well. It is recommended to use non-blocking sockets instead, see
326 "Using Non-Blocking Sockets"
327
329 This is a list of typical errors seen with the use of IO::Socket::SSL:
330 • Disabling verification with "SSL_verify_mode".
332 As described in "Essential Information About SSL/TLS", a proper
334 identification of the peer is essential and failing to verify makes
335 Man-In-The-Middle attacks possible.
336 Nevertheless, lots of scripts and even public modules or
338 applications disable verification, because it is probably the
339 easiest way to make the thing work and usually nobody notices any
340 security problems anyway.
341 If the verification does not succeed with the default settings, one
343 can do the following:
344 • Make sure the needed CAs are in the store, maybe use
346 "SSL_ca_file" or "SSL_ca_path" to specify a different CA
347 store.
348 • If the validation fails because the certificate is self-
350 signed and that's what you expect, you can use the
351 "SSL_fingerprint" option to accept specific leaf
352 certificates by their certificate or pubkey fingerprint.
353 • If the validation failed because the hostname does not
355 match and you cannot access the host with the name given in
356 the certificate, you can use "SSL_verifycn_name" to specify
357 the hostname you expect in the certificate.
358 A common error pattern is also to disable verification if they
360 found no CA store (different modules look at different "default"
361 places). Because IO::Socket::SSL is now able to provide a usable
362 CA store on most platforms (UNIX, Mac OSX and Windows) it is better
363 to use the defaults provided by IO::Socket::SSL. If necessary
364 these can be checked with the "default_ca" method.
365 • Polling of SSL sockets (e.g. select, poll and other event loops).
367 If you sysread one byte on a normal socket it will result in a
369 syscall to read one byte. Thus, if more than one byte is available
370 on the socket it will be kept in the network stack of your OS and
371 the next select or poll call will return the socket as readable.
372 But, with SSL you don't deliver single bytes. Multiple data bytes
373 are packaged and encrypted together in an SSL frame. Decryption can
374 only be done on the whole frame, so a sysread for one byte actually
375 reads the complete SSL frame from the socket, decrypts it and
376 returns the first decrypted byte. Further sysreads will return more
377 bytes from the same frame until all bytes are returned and the next
378 SSL frame will be read from the socket.
379 Thus, in order to decide if you can read more data (e.g. if sysread
381 will block) you must check if there are still data in the current
382 SSL frame by calling "pending" and if there are no data pending you
383 might check the underlying socket with select or poll. Another way
384 might be if you try to sysread at least 16kByte all the time.
385 16kByte is the maximum size of an SSL frame and because sysread
386 returns data from only a single SSL frame you can guarantee that
387 there are no pending data.
388 Additionally, contrary to plain sockets the data delivered on the
390 socket are not necessarily application payload. It might be a TLS
391 handshake, it might just be the beginning of a TLS record or it
392 might be TLS session tickets which are send after the TLS handshake
393 in TLS 1.3. In such situations select will return that data are
394 available for read since it only looks at the plain socket. A
395 sysread on the IO::Socket::SSL socket will not return any data
396 though since it is an abstraction which only returns application
397 data. This causes the sysread to hang in case the socket was
398 blocking or to return an error with EAGAIN on non-blocking sockets.
399 Applications using select or similar should therefore set the
400 socket to non-blocking and also expect that the sysread might
401 temporarily fail with EAGAIN.
402 See also "Using Non-Blocking Sockets".
404 • Expecting exactly the same behavior as plain sockets.
406 IO::Socket::SSL tries to emulate the usual socket behavior as good
408 as possible, but full emulation can not be done. Specifically a
409 read on the SSL socket might also result in a write on the TCP
410 socket or a write on the SSL socket might result in a read on the
411 TCP socket. Also "accept" and close on the SSL socket will result
412 in writing and reading data to the TCP socket too.
413 Especially the hidden writes might result in a connection reset if
415 the underlying TCP socket is already closed by the peer. Unless
416 signal PIPE is explicitly handled by the application this will
417 usually result in the application crashing. It is thus recommended
418 to explicitly IGNORE signal PIPE so that the errors get propagated
419 as EPIPE instead of causing a crash of the application.
420 • Set 'SSL_version' or 'SSL_cipher_list' to a "better" value.
422 IO::Socket::SSL tries to set these values to reasonable, secure
424 values which are compatible with the rest of the world. But, there
425 are some scripts or modules out there which tried to be smart and
426 get more secure or compatible settings. Unfortunately, they did
427 this years ago and never updated these values, so they are still
428 forced to do only 'TLSv1' (instead of also using TLSv12 or TLSv11).
429 Or they set 'HIGH' as the cipher list and thought they were secure,
430 but did not notice that 'HIGH' includes anonymous ciphers, e.g.
431 without identification of the peer.
432 So it is recommended to leave the settings at the secure defaults
434 which IO::Socket::SSL sets and which get updated from time to time
435 to better fit the real world.
436 • Make SSL settings inaccessible by the user, together with bad
438 builtin settings.
439 Some modules use IO::Socket::SSL, but don't make the SSL settings
441 available to the user. This is often combined with bad builtin
442 settings or defaults (like switching verification off).
443 Thus the user needs to hack around these restrictions by using
445 "set_args_filter_hack" or similar.
446 • Use of constants as strings.
448 Constants like "SSL_VERIFY_PEER" or "SSL_WANT_READ" should be used
450 as constants and not be put inside quotes, because they represent
451 numerical values.
452 • Forking and handling the socket in parent and child.
454 A fork of the process will duplicate the internal user space SSL
456 state of the socket. If both master and child interact with the
457 socket by using their own SSL state strange error messages will
458 happen. Such interaction includes explicit or implicit close of the
459 SSL socket. To avoid this the socket should be explicitly closed
460 with SSL_no_shutdown.
461 • Forking and executing a new process.
463 Since the SSL state is stored in user space it will be duplicated
465 by a fork but it will be lost when doing exec. This means it is not
466 possible to simply redirect stdin and stdout for the new process to
467 the SSL socket by duplicating the relevant file handles. Instead
468 explicitly exchanging plain data between child-process and SSL
469 socket are needed.
470
472 SSL is a complex protocol with multiple implementations and each of
473 these has their own quirks. While most of these implementations work
474 together, it often gets problematic with older versions, minimal
475 versions in load balancers, or plain wrong setups.
476 Unfortunately these problems are hard to debug. Helpful for debugging
478 are a knowledge of SSL internals, wireshark and the use of the debug
479 settings of IO::Socket::SSL and Net::SSLeay, which can both be set with
480 $IO::Socket::SSL::DEBUG. The following debugs levels are defined, but
481 used not in any consistent way:
482 • 0 - No debugging (default).
484 • 1 - Print out errors from IO::Socket::SSL and ciphers from
486 Net::SSLeay.
487 • 2 - Print also information about call flow from IO::Socket::SSL and
489 progress information from Net::SSLeay.
490 • 3 - Print also some data dumps from IO::Socket::SSL and from
492 Net::SSLeay.
493 Also, "analyze-ssl.pl" from the ssl-tools repository at
495 <https://github.com/noxxi/p5-ssl-tools> might be a helpful tool when
496 debugging SSL problems, as do the "openssl" command line tool and a
497 check with a different SSL implementation (e.g. a web browser).
498 The following problems are not uncommon:
500 • Bad server setup: missing intermediate certificates.
502 It is a regular problem that administrators fail to include all
504 necessary certificates into their server setup, e.g. everything
505 needed to build the trust chain from the trusted root. If they
506 check the setup with the browser everything looks ok, because
507 browsers work around these problems by caching any intermediate
508 certificates and apply them to new connections if certificates are
509 missing.
510 But, fresh browser profiles which have never seen these
512 intermediates cannot fill in the missing certificates and fail to
513 verify; the same is true with IO::Socket::SSL.
514 • Old versions of servers or load balancers which do not understand
516 specific TLS versions or croak on specific data.
517 From time to time one encounters an SSL peer, which just closes the
519 connection inside the SSL handshake. This can usually be worked
520 around by downgrading the SSL version, e.g. by setting
521 "SSL_version". Modern Browsers usually deal with such servers by
522 automatically downgrading the SSL version and repeat the connection
523 attempt until they succeed.
524 Worse servers do not close the underlying TCP connection but
526 instead just drop the relevant packet. This is harder to detect
527 because it looks like a stalled connection. But downgrading the SSL
528 version often works here too.
529 A cause of such problems are often load balancers or security
531 devices, which have hardware acceleration and only a minimal (and
532 less robust) SSL stack. They can often be detected because they
533 support much fewer ciphers than other implementations.
534 • Bad or old OpenSSL versions.
536 IO::Socket::SSL uses OpenSSL with the help of the Net::SSLeay
538 library. It is recommend to have a recent version of this library,
539 because it has more features and usually fewer known bugs.
540 • Validation of client certificates fail.
542 Make sure that the purpose of the certificate allows use as ssl
544 client (check with "openssl x509 -purpose", that the necessary root
545 certificate is in the path specified by "SSL_ca*" (or the default
546 path) and that any intermediate certificates needed to build the
547 trust chain are sent by the client.
548 • Validation of self-signed certificate fails even if it is given
550 with "SSL_ca*" argument.
551 The "SSL_ca*" arguments do not give a general trust store for
553 arbitrary certificates but only specify a store for CA certificates
554 which then can be used to verify other certificates. This
555 especially means that certificates which are not a CA get simply
556 ignored, notably self-signed certificates which do not also have
557 the CA-flag set.
558 This behavior of OpenSSL differs from the more general trust-store
560 concept which can be found in browsers and where it is possible to
561 simply added arbitrary certificates (CA or not) as trusted.
562
564 If you have a non-blocking socket, the expected behavior on read,
565 write, accept or connect is to set $! to EWOULDBLOCK if the operation
566 cannot be completed immediately. Note that EWOULDBLOCK is the same as
567 EAGAIN on UNIX systems, but is different on Windows.
568 With SSL, handshakes might occur at any time, even within an
570 established connection. In these cases it is necessary to finish the
571 handshake before you can read or write data. This might result in
572 situations where you want to read but must first finish the write of a
573 handshake or where you want to write but must first finish a read. In
574 these cases $! is set to EAGAIN like expected, and additionally
575 $SSL_ERROR is set to either SSL_WANT_READ or SSL_WANT_WRITE. Thus if
576 you get EWOULDBLOCK on a SSL socket you must check $SSL_ERROR for
577 SSL_WANT_* and adapt your event mask accordingly.
578 Using readline on non-blocking sockets does not make much sense and I
580 would advise against using it. And, while the behavior is not
581 documented for other IO::Socket classes, it will try to emulate the
582 behavior seen there, e.g. to return the received data instead of
583 blocking, even if the line is not complete. If an unrecoverable error
584 occurs it will return nothing, even if it already received some data.
585 Also, I would advise against using "accept" with a non-blocking SSL
587 object because it might block and this is not what most would expect.
588 The reason for this is that "accept" on a non-blocking TCP socket (e.g.
589 IO::Socket::IP, IO::Socket::INET..) results in a new TCP socket which
590 does not inherit the non-blocking behavior of the master socket. And
591 thus, the initial SSL handshake on the new socket inside
592 "IO::Socket::SSL::accept" will be done in a blocking way. To work
593 around this you are safer by doing a TCP accept and later upgrade the
594 TCP socket in a non-blocking way with "start_SSL" and "accept_SSL".
595 my $cl = IO::Socket::SSL->new($dst);
597 $cl->blocking(0);
598 my $sel = IO::Select->new($cl);
599 while (1) {
600 # with SSL a call for reading n bytes does not result in reading of n
601 # bytes from the socket, but instead it must read at least one full SSL
602 # frame. If the socket has no new bytes, but there are unprocessed data
603 # from the SSL frame can_read will block!
604 # wait for data on socket
606 $sel->can_read();
607 # new data on socket or eof
609 READ:
610 # this does not read only 1 byte from socket, but reads the complete SSL
611 # frame and then just returns one byte. On subsequent calls it than
612 # returns more byte of the same SSL frame until it needs to read the
613 # next frame.
614 my $n = sysread( $cl,my $buf,1);
615 if ( ! defined $n ) {
616 die $! if not $!{EWOULDBLOCK};
617 next if $SSL_ERROR == SSL_WANT_READ;
618 if ( $SSL_ERROR == SSL_WANT_WRITE ) {
619 # need to write data on renegotiation
620 $sel->can_write;
621 next;
622 }
623 die "something went wrong: $SSL_ERROR";
624 } elsif ( ! $n ) {
625 last; # eof
626 } else {
627 # read next bytes
628 # we might have still data within the current SSL frame
629 # thus first process these data instead of waiting on the underlying
630 # socket object
631 goto READ if $cl->pending; # goto sysread
632 next; # goto $sel->can_read
633 }
634 }
635 Additionally there are differences to plain sockets when using select,
637 poll, kqueue or similar technologies to get notified if data are
638 available. Relying only on these calls is not sufficient in all cases
639 since unread data might be internally buffered in the SSL stack. To
640 detect such buffering pending() need to be used. Alternatively the
641 buffering can be avoided by using sysread with the maximum size of an
642 SSL frame. See "Common Usage Errors" for details.
643
645 SNI Support
646 Newer extensions to SSL can distinguish between multiple hostnames on
647 the same IP address using Server Name Indication (SNI).
648 Support for SNI on the client side was added somewhere in the OpenSSL
650 0.9.8 series, but with 1.0 a bug was fixed when the server could not
651 decide about its hostname. Therefore client side SNI is only supported
652 with OpenSSL 1.0 or higher in IO::Socket::SSL. With a supported
653 version, SNI is used automatically on the client side, if it can
654 determine the hostname from "PeerAddr" or "PeerHost" (which are
655 synonyms in the underlying IO::Socket:: classes and thus should never
656 be set both or at least not to different values). On unsupported
657 OpenSSL versions it will silently not use SNI. The hostname can also
658 be given explicitly given with "SSL_hostname", but in this case it will
659 throw in error, if SNI is not supported. To check for support you
660 might call "IO::Socket::SSL->can_client_sni()".
661 On the server side, earlier versions of OpenSSL are supported, but only
663 together with Net::SSLeay version >= 1.50. To check for support you
664 might call "IO::Socket::SSL->can_server_sni()". If server side SNI is
665 supported, you might specify different certificates per host with
666 "SSL_cert*" and "SSL_key*", and check the requested name using
667 "get_servername".
668 Talk Plain and SSL With The Same Socket
670 It is often required to first exchange some plain data and then upgrade
671 the socket to SSL after some kind of STARTTLS command. Protocols like
672 FTPS even need a way to downgrade the socket again back to plain.
673 The common way to do this would be to create a normal socket and use
675 "start_SSL" to upgrade and stop_SSL to downgrade:
676 my $sock = IO::Socket::INET->new(...) or die $!;
678 ... exchange plain data on $sock until starttls command ...
679 IO::Socket::SSL->start_SSL($sock,%sslargs) or die $SSL_ERROR;
680 ... now $sock is an IO::Socket::SSL object ...
681 ... exchange data with SSL on $sock until stoptls command ...
682 $sock->stop_SSL or die $SSL_ERROR;
683 ... now $sock is again an IO::Socket::INET object ...
684 But, lots of modules just derive directly from IO::Socket::INET. While
686 this base class can be replaced with IO::Socket::SSL, these modules
687 cannot easily support different base classes for SSL and plain data and
688 switch between these classes on a starttls command.
689 To help in this case, IO::Socket::SSL can be reduced to a plain socket
691 on startup, and connect_SSL/accept_SSL/start_SSL can be used to enable
692 SSL and "stop_SSL" to talk plain again:
693 my $sock = IO::Socket::SSL->new(
695 PeerAddr => ...
696 SSL_startHandshake => 0,
697 %sslargs
698 ) or die $!;
699 ... exchange plain data on $sock until starttls command ...
700 $sock->connect_SSL or die $SSL_ERROR;
701 ... now $sock is an IO::Socket::SSL object ...
702 ... exchange data with SSL on $sock until stoptls command ...
703 $sock->stop_SSL or die $SSL_ERROR;
704 ... $sock is still an IO::Socket::SSL object ...
705 ... but data exchanged again in plain ...
706
708 IO::Socket::SSL behaves similarly to other IO::Socket modules and thus
709 could be integrated in the same way, but you have to take special care
710 when using non-blocking I/O (like for handling timeouts) or using
711 select or poll. Please study the documentation on how to deal with
712 these differences.
713 Also, it is recommended to not set or touch most of the "SSL_*"
715 options, so that they keep their secure defaults. It is also
716 recommended to let the user override these SSL specific settings
717 without the need of global settings or hacks like
718 "set_args_filter_hack".
719 The notable exception is "SSL_verifycn_scheme". This should be set to
721 the hostname verification scheme required by the module or protocol.
722
724 IO::Socket::SSL inherits from another IO::Socket module. The choice of
725 the super class depends on the installed modules:
726 • If IO::Socket::IP with at least version 0.20 is installed it will
728 use this module as super class, transparently providing IPv6 and
729 IPv4 support.
730 • If IO::Socket::INET6 is installed it will use this module as super
732 class, transparently providing IPv6 and IPv4 support.
733 • Otherwise it will fall back to IO::Socket::INET, which is a perl
735 core module. With IO::Socket::INET you only get IPv4 support.
736 Please be aware that with the IPv6 capable super classes, it will look
738 first for the IPv6 address of a given hostname. If the resolver
739 provides an IPv6 address, but the host cannot be reached by IPv6, there
740 will be no automatic fallback to IPv4. To avoid these problems you can
741 enforce IPv4 for a specific socket by using the "Domain" or "Family"
742 option with the value AF_INET as described in IO::Socket::IP.
743 Alternatively you can enforce IPv4 globally by loading IO::Socket::SSL
744 with the option 'inet4', in which case it will use the IPv4 only class
745 IO::Socket::INET as the super class.
746 IO::Socket::SSL will provide all of the methods of its super class, but
748 sometimes it will override them to match the behavior expected from SSL
749 or to provide additional arguments.
750 The new or changed methods are described below, but please also read
752 the section about SSL specific error handling.
753 Error Handling
755 If an SSL specific error occurs, the global variable $SSL_ERROR
756 will be set. If the error occurred on an existing SSL socket, the
757 method "errstr" will give access to the latest socket specific
758 error. Both $SSL_ERROR and the "errstr" method give a dualvar
759 similar to $!, e.g. providing an error number in numeric context
760 or an error description in string context.
761 new(...)
763 Creates a new IO::Socket::SSL object. You may use all the friendly
764 options that came bundled with the super class (e.g.
765 IO::Socket::IP, IO::Socket::INET, ...) plus (optionally) the ones
766 described below. If you don't specify any SSL related options it
767 will do its best in using secure defaults, e.g. choosing good
768 ciphers, enabling proper verification, etc.
769 SSL_server
771 Set this option to a true value if the socket should be used as a
772 server. If this is not explicitly set it is assumed if the
773 "Listen" parameter is given when creating the socket.
774 SSL_hostname
776 This can be given to specify the hostname used for SNI, which is
777 needed if you have multiple SSL hostnames on the same IP address.
778 If not given it will try to determine the hostname from
779 "PeerAddr", which will fail if only an IP was given or if this
780 argument is used within "start_SSL".
781 If you want to disable SNI, set this argument to ''.
783 Currently only supported for the client side and will be ignored
785 for the server side.
786 See section "SNI Support" for details of SNI the support.
788 SSL_startHandshake
790 If this option is set to false (defaults to true) it will not
791 start the SSL handshake yet. This has to be done later with
792 "accept_SSL" or "connect_SSL". Before the handshake is started
793 read/write/etc. can be used to exchange plain data.
794 SSL_keepSocketOnError
796 If this option is set to true (defaults to false) it will not
797 close the underlying TCP socket on errors. In most cases there is
798 no real use for this behavior since both sides of the TCP
799 connection will probably have a different idea of the current
800 state of the connection.
801 SSL_ca | SSL_ca_file | SSL_ca_path
803 Usually you want to verify that the peer certificate has been
804 signed by a trusted certificate authority. In this case you
805 should use this option to specify the file ("SSL_ca_file") or
806 directory ("SSL_ca_path") containing the certificate(s) of the
807 trusted certificate authorities.
808 "SSL_ca_path" can also be an array or a string containing
810 multiple path, where the path are separated by the platform
811 specific separator. This separator is ";" on DOS, Windows,
812 Netware, "," on VMS and ":" for all the other systems. If
813 multiple path are given at least one of these must be accessible.
814 You can also give a list of X509* certificate handles (like you
816 get from Net::SSLeay or IO::Socket::SSL::Utils::PEM_xxx2cert)
817 with "SSL_ca". These will be added to the CA store before path
818 and file and thus take precedence. If neither SSL_ca, nor
819 SSL_ca_file or SSL_ca_path are set it will use "default_ca()" to
820 determine the user-set or system defaults. If you really don't
821 want to set a CA set SSL_ca_file or SSL_ca_path to "\undef" or
822 SSL_ca to an empty list. (unfortunately '' is used by some
823 modules using IO::Socket::SSL when CA is not explicitly given).
824 SSL_client_ca | SSL_client_ca_file
826 If verify_mode is VERIFY_PEER on the server side these options
827 can be used to set the list of acceptable CAs for the client.
828 This way the client can select they required certificate from a
829 list of certificates. The value for these options is similar to
830 "SSL_ca" and "SSL_ca_file".
831 SSL_fingerprint
833 Sometimes you have a self-signed certificate or a certificate
834 issued by an unknown CA and you really want to accept it, but
835 don't want to disable verification at all. In this case you can
836 specify the fingerprint of the certificate as
837 'algo$hex_fingerprint'. "algo" is a fingerprint algorithm
838 supported by OpenSSL, e.g. 'sha1','sha256'... and
839 "hex_fingerprint" is the hexadecimal representation of the binary
840 fingerprint. Any colons inside the hex string will be ignored.
841 If you want to use the fingerprint of the pubkey inside the
843 certificate instead of the certificate use the syntax
844 'algo$pub$hex_fingerprint' instead. To get the fingerprint of an
845 established connection you can use "get_fingerprint".
846 It is also possible to skip "algo$", i.e. only specify the
848 fingerprint. In this case the likely algorithms will be
849 automatically detected based on the length of the digest string.
850 You can specify a list of fingerprints in case you have several
852 acceptable certificates. If a fingerprint matches the topmost
853 (i.e. leaf) certificate no additional validations can make the
854 verification fail.
855 SSL_cert_file | SSL_cert | SSL_key_file | SSL_key
857 If you create a server you usually need to specify a server
858 certificate which should be verified by the client. Same is true
859 for client certificates, which should be verified by the server.
860 The certificate can be given as a file with SSL_cert_file or as
861 an internal representation of an X509* object (like you get from
862 Net::SSLeay or IO::Socket::SSL::Utils::PEM_xxx2cert) with
863 SSL_cert. If given as a file it will automatically detect the
864 format. Supported file formats are PEM, DER and PKCS#12, where
865 PEM and PKCS#12 can contain the certificate and the chain to use,
866 while DER can only contain a single certificate.
867 If given as a list of X509* please note, that the all the chain
869 certificates (e.g. all except the first) will be "consumed" by
870 openssl and will be freed if the SSL context gets destroyed - so
871 you should never free them yourself. But the servers certificate
872 (e.g. the first) will not be consumed by openssl and thus must be
873 freed by the application.
874 For each certificate a key is need, which can either be given as
876 a file with SSL_key_file or as an internal representation of an
877 EVP_PKEY* object with SSL_key (like you get from Net::SSLeay or
878 IO::Socket::SSL::Utils::PEM_xxx2key). If a key was already given
879 within the PKCS#12 file specified by SSL_cert_file it will ignore
880 any SSL_key or SSL_key_file. If no SSL_key or SSL_key_file was
881 given it will try to use the PEM file given with SSL_cert_file
882 again, maybe it contains the key too.
883 If your SSL server should be able to use different certificates
885 on the same IP address, depending on the name given by SNI, you
886 can use a hash reference instead of a file with "<hostname ="
887 cert_file>>.
888 If your SSL server should be able to use both RSA and ECDSA
890 certificates for the same domain/IP a similar hash reference like
891 with SNI is given. The domain names used to specify the
892 additional certificates should be "hostname%whatever", i.e.
893 "hostname%ecc" or similar. This needs at least OpenSSL 1.0.2. To
894 let the server pick the certificate based on the clients cipher
895 preference "SSL_honor_cipher_order" should be set to false.
896 In case certs and keys are needed but not given it might fall
898 back to builtin defaults, see "Defaults for Cert, Key and CA".
899 Examples:
901 SSL_cert_file => 'mycert.pem',
903 SSL_key_file => 'mykey.pem',
904 SSL_cert_file => {
906 "foo.example.org" => 'foo-cert.pem',
907 "foo.example.org%ecc" => 'foo-ecc-cert.pem',
908 "bar.example.org" => 'bar-cert.pem',
909 # used when nothing matches or client does not support SNI
910 '' => 'default-cert.pem',
911 '%ecc' => 'default-ecc-cert.pem',
912 },
913 SSL_key_file => {
914 "foo.example.org" => 'foo-key.pem',
915 "foo.example.org%ecc" => 'foo-ecc-key.pem',
916 "bar.example.org" => 'bar-key.pem',
917 # used when nothing matches or client does not support SNI
918 '' => 'default-key.pem',
919 '%ecc' => 'default-ecc-key.pem',
920 }
921 SSL_passwd_cb
923 If your private key is encrypted, you might not want the default
924 password prompt from Net::SSLeay. This option takes a reference
925 to a subroutine that should return the password required to
926 decrypt your private key.
927 SSL_use_cert
929 If this is true, it forces IO::Socket::SSL to use a certificate
930 and key, even if you are setting up an SSL client. If this is
931 set to 0 (the default), then you will only need a certificate and
932 key if you are setting up a server.
933 SSL_use_cert will implicitly be set if SSL_server is set. For
935 convenience it is also set if it was not given but a cert was
936 given for use (SSL_cert_file or similar).
937 SSL_version
939 Sets the version of the SSL protocol used to transmit data.
940 'SSLv23' uses a handshake compatible with SSL2.0, SSL3.0 and
941 TLS1.x, while 'SSLv2', 'SSLv3', 'TLSv1', 'TLSv1_1', 'TLSv1_2', or
942 'TLSv1_3' restrict handshake and protocol to the specified
943 version. All values are case-insensitive. Instead of 'TLSv1_1',
944 'TLSv1_2', and 'TLSv1_3' one can also use 'TLSv11', 'TLSv12', and
945 'TLSv13'. Support for 'TLSv1_1', 'TLSv1_2', and 'TLSv1_3'
946 requires recent versions of Net::SSLeay and openssl. The default
947 SSL_version is defined by the underlying cryptographic library.
948 Independent from the handshake format you can limit to set of
950 accepted SSL versions by adding !version separated by ':'.
951 For example, 'SSLv23:!SSLv3:!SSLv2' means that the handshake
953 format is compatible to SSL2.0 and higher, but that the
954 successful handshake is limited to TLS1.0 and higher, that is no
955 SSL2.0 or SSL3.0 because both of these versions have serious
956 security issues and should not be used anymore. You can also use
957 !TLSv1_1 and !TLSv1_2 to disable TLS versions 1.1 and 1.2 while
958 still allowing TLS version 1.0.
959 Setting the version instead to 'TLSv1' might break interaction
961 with older clients, which need and SSL2.0 compatible handshake.
962 On the other side some clients just close the connection when
963 they receive a TLS version 1.1 request. In this case setting the
964 version to 'SSLv23:!SSLv2:!SSLv3:!TLSv1_1:!TLSv1_2' might help.
965 SSL_cipher_list
967 If this option is set the cipher list for the connection will be
968 set to the given value, e.g. something like
969 'ALL:!LOW:!EXP:!aNULL'. Look into the OpenSSL documentation
970 (<https://www.openssl.org/docs/manmaster/man1/openssl-ciphers.html#CIPHER-STRINGS>)
971 for more details.
972 Unless you fail to contact your peer because of no shared ciphers
974 it is recommended to leave this option at the default setting,
975 which honors the system-wide PROFILE=SYSTEM cipher list.
976 In case different cipher lists are needed for different SNI hosts
978 a hash can be given with the host as key and the cipher suite as
979 value, similar to SSL_cert*.
980 SSL_honor_cipher_order
982 If this option is true the cipher order the server specified is
983 used instead of the order proposed by the client. This option
984 defaults to true to make use of our secure cipher list setting.
985 SSL_dh_file
987 To create a server which provides forward secrecy you need to
988 either give the DH parameters or (better, because faster) the
989 ECDH curve. This setting cares about DH parameters.
990 To support non-elliptic Diffie-Hellman key exchange a suitable
992 file needs to be given here or the SSL_dh should be used with an
993 appropriate value. See dhparam command in openssl for more
994 information.
995 If neither "SSL_dh_file" nor "SSL_dh" are set a builtin DH
997 parameter with a length of 2048 bit is used to offer DH key
998 exchange by default. If you don't want this (e.g. disable DH key
999 exchange) explicitly set this or the "SSL_dh" parameter to undef.
1000 SSL_dh
1002 Like SSL_dh_file, but instead of giving a file you use a
1003 preloaded or generated DH*.
1004 SSL_ecdh_curve
1006 To create a server which provides forward secrecy you need to
1007 either give the DH parameters or (better, because faster) the
1008 ECDH curve. This setting cares about the ECDH curve(s).
1009 To support Elliptic Curve Diffie-Hellmann key exchange the OID or
1011 NID of at least one suitable curve needs to be provided here.
1012 With OpenSSL 1.1.0+ this parameter defaults to "auto", which
1014 means that it lets OpenSSL pick the best settings. If support for
1015 CTX_set_ecdh_auto is implemented in Net::SSLeay (needs at least
1016 version 1.86) it will use this to implement the same default.
1017 Otherwise it will default to "prime256v1" (builtin of OpenSSL) in
1018 order to offer ECDH key exchange by default.
1019 If setting groups or curves is supported by Net::SSLeay (needs at
1021 least version 1.86) then multiple curves can be given here in the
1022 order of the preference, i.e. "P-521:P-384:P-256". When used at
1023 the client side this will include the supported curves as
1024 extension in the TLS handshake.
1025 If you don't want to have ECDH key exchange this could be set to
1027 undef or set "SSL_ciphers" to exclude all of these ciphers.
1028 You can check if ECDH support is available by calling
1030 "IO::Socket::SSL->can_ecdh".
1031 SSL_verify_mode
1033 This option sets the verification mode for the peer certificate.
1034 You may combine SSL_VERIFY_PEER (verify_peer),
1035 SSL_VERIFY_FAIL_IF_NO_PEER_CERT (fail verification if no peer
1036 certificate exists; ignored for clients), SSL_VERIFY_CLIENT_ONCE
1037 (verify client once; ignored for clients). See OpenSSL man page
1038 for SSL_CTX_set_verify for more information.
1039 The default is SSL_VERIFY_NONE for server (e.g. no check for
1041 client certificate) and SSL_VERIFY_PEER for client (check server
1042 certificate).
1043 SSL_verify_callback
1045 If you want to verify certificates yourself, you can pass a sub
1046 reference along with this parameter to do so. When the callback
1047 is called, it will be passed:
1048 1. a true/false value that indicates what OpenSSL thinks of the
1050 certificate,
1051 2. a C-style memory address of the certificate store,
1052 3. a string containing the certificate's issuer attributes and
1053 owner attributes, and
1054 4. a string containing any errors encountered (0 if no errors).
1055 5. a C-style memory address of the peer's own certificate
1056 (convertible to PEM form with
1057 Net::SSLeay::PEM_get_string_X509()).
1058 6. The depth of the certificate in the chain. Depth 0 is the leaf
1059 certificate.
1060 The function should return 1 or 0, depending on whether it thinks
1062 the certificate is valid or invalid. The default is to let
1063 OpenSSL do all of the busy work.
1064 The callback will be called for each element in the certificate
1066 chain.
1067 See the OpenSSL documentation for SSL_CTX_set_verify for more
1069 information.
1070 SSL_verifycn_scheme
1072 The scheme is used to correctly verify the identity inside the
1073 certificate by using the hostname of the peer. See the
1074 information about the verification schemes in verify_hostname.
1075 If you don't specify a scheme it will use 'default', but only
1077 complain loudly if the name verification fails instead of letting
1078 the whole certificate verification fail. THIS WILL CHANGE, e.g.
1079 it will let the certificate verification fail in the future if
1080 the hostname does not match the certificate !!!! To override the
1081 name used in verification use SSL_verifycn_name.
1082 The scheme 'default' is a superset of the usual schemes, which
1084 will accept the hostname in common name and subjectAltName and
1085 allow wildcards everywhere. While using this scheme is way more
1086 secure than no name verification at all you better should use the
1087 scheme specific to your application protocol, e.g. 'http',
1088 'ftp'...
1089 If you are really sure, that you don't want to verify the
1091 identity using the hostname you can use 'none' as a scheme. In
1092 this case you'd better have alternative forms of verification,
1093 like a certificate fingerprint or do a manual verification later
1094 by calling verify_hostname yourself.
1095 SSL_verifycn_publicsuffix
1097 This option is used to specify the behavior when checking
1098 wildcards certificates for public suffixes, e.g. no wildcard
1099 certificates for *.com or *.co.uk should be accepted, while
1100 *.example.com or *.example.co.uk is ok.
1101 If not specified it will simply use the builtin default of
1103 IO::Socket::SSL::PublicSuffix, you can create another object with
1104 from_string or from_file of this module.
1105 To disable verification of public suffix set this option to ''.
1107 SSL_verifycn_name
1109 Set the name which is used in verification of hostname. If
1110 SSL_verifycn_scheme is set and no SSL_verifycn_name is given it
1111 will try to use SSL_hostname or PeerHost and PeerAddr settings
1112 and fail if no name can be determined. If SSL_verifycn_scheme is
1113 not set it will use a default scheme and warn if it cannot
1114 determine a hostname, but it will not fail.
1115 Using PeerHost or PeerAddr works only if you create the
1117 connection directly with "IO::Socket::SSL->new", if an
1118 IO::Socket::INET object is upgraded with start_SSL the name has
1119 to be given in SSL_verifycn_name or SSL_hostname.
1120 SSL_check_crl
1122 If you want to verify that the peer certificate has not been
1123 revoked by the signing authority, set this value to true. OpenSSL
1124 will search for the CRL in your SSL_ca_path, or use the file
1125 specified by SSL_crl_file. See the Net::SSLeay documentation for
1126 more details. Note that this functionality appears to be broken
1127 with OpenSSL < v0.9.7b, so its use with lower versions will
1128 result in an error.
1129 SSL_crl_file
1131 If you want to specify the CRL file to be used, set this value to
1132 the pathname to be used. This must be used in addition to
1133 setting SSL_check_crl.
1134 SSL_ocsp_mode
1136 Defines how certificate revocation is done using OCSP (Online
1137 Status Revocation Protocol). The default is to send a request for
1138 OCSP stapling to the server and if the server sends an OCSP
1139 response back the result will be used.
1140 Any other OCSP checking needs to be done manually with
1142 "ocsp_resolver".
1143 The following flags can be combined with "|":
1145 SSL_OCSP_NO_STAPLE
1147 Don't ask for OCSP stapling. This is the default if
1148 SSL_verify_mode is VERIFY_NONE.
1149 SSL_OCSP_TRY_STAPLE
1151 Try OCSP stapling, but don't complain if it gets no
1152 stapled response back. This is the default if
1153 SSL_verify_mode is VERIFY_PEER (the default).
1154 SSL_OCSP_MUST_STAPLE
1156 Consider it a hard error, if the server does not send a
1157 stapled OCSP response back. Most servers currently send
1158 no stapled OCSP response back.
1159 SSL_OCSP_FAIL_HARD
1161 Fail hard on response errors, default is to fail soft
1162 like the browsers do. Soft errors mean, that the OCSP
1163 response is not usable, e.g. no response, error response,
1164 no valid signature etc. Certificate revocations inside a
1165 verified response are considered hard errors in any case.
1166 Soft errors inside a stapled response are never
1168 considered hard, e.g. it is expected that in this case an
1169 OCSP request will be send to the responsible OCSP
1170 responder.
1171 SSL_OCSP_FULL_CHAIN
1173 This will set up the "ocsp_resolver" so that all
1174 certificates from the peer chain will be checked,
1175 otherwise only the leaf certificate will be checked
1176 against revocation.
1177 SSL_ocsp_staple_callback
1179 If this callback is defined, it will be called with the SSL
1180 object and the OCSP response handle obtained from the peer, e.g.
1181 "<$cb-"($ssl,$resp)>>. If the peer did not provide a stapled
1182 OCSP response the function will be called with "$resp=undef".
1183 Because the OCSP response handle is no longer valid after leaving
1184 this function it should not by copied or freed. If access to the
1185 response is necessary after leaving this function it can be
1186 serialized with "Net::SSLeay::i2d_OCSP_RESPONSE".
1187 If no such callback is provided, it will use the default one,
1189 which verifies the response and uses it to check if the
1190 certificate(s) of the connection got revoked.
1191 SSL_ocsp_cache
1193 With this option a cache can be given for caching OCSP responses,
1194 which could be shared between different SSL contexts. If not
1195 given a cache specific to the SSL context only will be used.
1196 You can either create a new cache with
1198 "IO::Socket::SSL::OCSP_Cache->new([size])" or implement your own
1199 cache, which needs to have methods "put($key,\%entry)" and
1200 "get($key)" (returning "\%entry") where entry is the hash
1201 representation of the OCSP response with fields like
1202 "nextUpdate". The default implementation of the cache will
1203 consider responses valid as long as "nextUpdate" is less then the
1204 current time.
1205 SSL_reuse_ctx
1207 If you have already set the above options for a previous instance
1208 of IO::Socket::SSL, then you can reuse the SSL context of that
1209 instance by passing it as the value for the SSL_reuse_ctx
1210 parameter. You may also create a new instance of the
1211 IO::Socket::SSL::SSL_Context class, using any context options
1212 that you desire without specifying connection options, and pass
1213 that here instead.
1214 If you use this option, all other context-related options that
1216 you pass in the same call to new() will be ignored unless the
1217 context supplied was invalid. Note that, contrary to versions of
1218 IO::Socket::SSL below v0.90, a global SSL context will not be
1219 implicitly used unless you use the set_default_context()
1220 function.
1221 SSL_create_ctx_callback
1223 With this callback you can make individual settings to the
1224 context after it got created and the default setup was done. The
1225 callback will be called with the CTX object from Net::SSLeay as
1226 the single argument.
1227 Example for limiting the server session cache size:
1229 SSL_create_ctx_callback => sub {
1231 my $ctx = shift;
1232 Net::SSLeay::CTX_sess_set_cache_size($ctx,128);
1233 }
1234 SSL_session_cache_size
1236 If you make repeated connections to the same host/port and the
1237 SSL renegotiation time is an issue, you can turn on client-side
1238 session caching with this option by specifying a positive cache
1239 size. For successive connections, pass the SSL_reuse_ctx option
1240 to the new() calls (or use set_default_context()) to make use of
1241 the cached sessions. The session cache size refers to the number
1242 of unique host/port pairs that can be stored at one time; the
1243 oldest sessions in the cache will be removed if new ones are
1244 added.
1245 This option does not effect the session cache a server has for
1247 it's clients, e.g. it does not affect SSL objects with SSL_server
1248 set.
1249 Note that session caching with TLS 1.3 needs at least Net::SSLeay
1251 1.86.
1252 SSL_session_cache
1254 Specifies session cache object which should be used instead of
1255 creating a new. Overrules SSL_session_cache_size. This option
1256 is useful if you want to reuse the cache, but not the rest of the
1257 context.
1258 A session cache object can be created using
1260 "IO::Socket::SSL::Session_Cache->new( cachesize )".
1261 Use set_default_session_cache() to set a global cache object.
1263 SSL_session_key
1265 Specifies a key to use for lookups and inserts into client-side
1266 session cache. Per default ip:port of destination will be used,
1267 but sometimes you want to share the same session over multiple
1268 ports on the same server (like with FTPS).
1269 SSL_session_id_context
1271 This gives an id for the servers session cache. It's necessary if
1272 you want clients to connect with a client certificate. If not
1273 given but SSL_verify_mode specifies the need for client
1274 certificate a context unique id will be picked.
1275 SSL_error_trap
1277 When using the accept() or connect() methods, it may be the case
1278 that the actual socket connection works but the SSL negotiation
1279 fails, as in the case of an HTTP client connecting to an HTTPS
1280 server. Passing a subroutine ref attached to this parameter
1281 allows you to gain control of the orphaned socket instead of
1282 having it be closed forcibly. The subroutine, if called, will be
1283 passed two parameters: a reference to the socket on which the SSL
1284 negotiation failed and the full text of the error message.
1285 SSL_npn_protocols
1287 If used on the server side it specifies list of protocols
1288 advertised by SSL server as an array ref, e.g.
1289 ['spdy/2','http1.1']. On the client side it specifies the
1290 protocols offered by the client for NPN as an array ref. See
1291 also method "next_proto_negotiated".
1292 Next Protocol Negotiation (NPN) is available with Net::SSLeay
1294 1.46+ and openssl-1.0.1+. NPN is unavailable in TLSv1.3 protocol.
1295 To check support you might call "IO::Socket::SSL->can_npn()". If
1296 you use this option with an unsupported Net::SSLeay/OpenSSL it
1297 will throw an error.
1298 SSL_alpn_protocols
1300 If used on the server side it specifies list of protocols
1301 supported by the SSL server as an array ref, e.g. ['http/2.0',
1302 'spdy/3.1','http/1.1']. On the client side it specifies the
1303 protocols advertised by the client for ALPN as an array ref. See
1304 also method "alpn_selected".
1305 Application-Layer Protocol Negotiation (ALPN) is available with
1307 Net::SSLeay 1.56+ and openssl-1.0.2+. More details about the
1308 extension are in RFC7301. To check support you might call
1309 "IO::Socket::SSL->can_alpn()". If you use this option with an
1310 unsupported Net::SSLeay/OpenSSL it will throw an error.
1311 Note that some client implementations may encounter problems if
1313 both NPN and ALPN are specified. Since ALPN is intended as a
1314 replacement for NPN, try providing ALPN protocols then fall back
1315 to NPN if that fails.
1316 SSL_ticket_keycb => [$sub,$data] | $sub
1318 This is a callback used for stateless session reuse (Session
1319 Tickets, RFC 5077).
1320 This callback will be called as "$sub->($data,[$key_name])" where
1322 $data is the argument given to SSL_ticket_keycb (or undef) and
1323 $key_name depends on the mode:
1324 encrypt ticket
1326 If a ticket needs to be encrypted the callback will be
1327 called without $key_name. In this case it should return
1328 "($current_key,$current_key_name") where $current_key is
1329 the current key (32 byte random data) and
1330 $current_key_name the name associated with this key
1331 (exactly 16 byte). This $current_key_name will be
1332 incorporated into the ticket.
1333 decrypt ticket
1335 If a ticket needs to be decrypted the callback will be
1336 called with $key_name as found in the ticket. It should
1337 return "($key,$current_key_name") where $key is the key
1338 associated with the given $key_name and $current_key_name
1339 the name associated with the currently active key. If
1340 $current_key_name is different from the given $key_name
1341 the callback will be called again to re-encrypt the
1342 ticket with the currently active key.
1343 If no key can be found which matches the given $key_name
1345 then this function should return nothing (empty list).
1346 This mechanism should be used to limit the life time for
1348 each key encrypting the ticket. Compromise of a ticket
1349 encryption key might lead to decryption of SSL sessions
1350 which used session tickets protected by this key.
1351 Example:
1353 Net::SSLeay::RAND_bytes(my $oldkey,32);
1355 Net::SSLeay::RAND_bytes(my $newkey,32);
1356 my $oldkey_name = pack("a16",'oldsecret');
1357 my $newkey_name = pack("a16",'newsecret');
1358 my @keys = (
1360 [ $newkey_name, $newkey ], # current active key
1361 [ $oldkey_name, $oldkey ], # already expired
1362 );
1363 my $keycb = [ sub {
1365 my ($mykeys,$name) = @_;
1366 # return (current_key, current_key_name) if no name given
1368 return ($mykeys->[0][1],$mykeys->[0][0]) if ! $name;
1369 # return (matching_key, current_key_name) if we find a key matching
1371 # the given name
1372 for(my $i = 0; $i<@$mykeys; $i++) {
1373 next if $name ne $mykeys->[$i][0];
1374 return ($mykeys->[$i][1],$mykeys->[0][0]);
1375 }
1376 # no matching key found
1378 return;
1379 },\@keys ];
1380 my $srv = IO::Socket::SSL->new(..., SSL_ticket_keycb => $keycb);
1382 SSL_mode_release_buffers 1|0
1384 This enables or disables the SSL_MODE_RELEASE_BUFFERS option on
1385 the SSL object. With this option the read buffer will be
1386 released after each SSL_read but will need to be reallocated for
1387 each new SSL_read. If memory usage is a concern this might save
1388 lots of memory in the mean time though, about 34k per idle SSL
1389 connection according to the documentation in
1390 SSL_CTX_set_mode(3ssl).
1391 accept
1393 This behaves similar to the accept function of the underlying
1394 socket class, but additionally does the initial SSL handshake. But
1395 because the underlying socket class does return a blocking file
1396 handle even when accept is called on a non-blocking socket, the SSL
1397 handshake on the new file object will be done in a blocking way.
1398 Please see the section about non-blocking I/O for details. If you
1399 don't like this behavior you should do accept on the TCP socket and
1400 then upgrade it with "start_SSL" later.
1401 connect(...)
1403 This behaves similar to the connect function but also does an SSL
1404 handshake. Because you cannot give SSL specific arguments to this
1405 function, you should better either use "new" to create a connect
1406 SSL socket or "start_SSL" to upgrade an established TCP socket to
1407 SSL.
1408 close(...)
1410 Contrary to a close for a simple INET socket a close in SSL also
1411 mandates a proper shutdown of the SSL part. This is done by sending
1412 a close notify message by both peers.
1413 A naive implementation would thus wait until it receives the close
1415 notify message from the peer - which conflicts with the commonly
1416 expected semantic that a close will not block. The default behavior
1417 is thus to only send a close notify but not wait for the close
1418 notify of the peer. If this is required "SSL_fast_shutdown" need to
1419 be explicitly set to false.
1420 There are also cases where a SSL shutdown should not be done at
1422 all. This is true for example when forking to let a child deal with
1423 the socket and closing the socket in the parent process. A naive
1424 explicit "close" or an implicit close when destroying the socket in
1425 the parent would send a close notify to the peer which would make
1426 the SSL socket in the client process unusable. In this case an
1427 explicit "close" with "SSL_no_shutdown" set to true should be done
1428 in the parent process.
1429 For more details and other arguments see "stop_SSL" which gets
1431 called from "close" to shutdown the SSL state of the socket.
1432 sysread( BUF, LEN, [ OFFSET ] )
1434 This function behaves from the outside the same as sysread in other
1435 IO::Socket objects, e.g. it returns at most LEN bytes of data. But
1436 in reality it reads not only LEN bytes from the underlying socket,
1437 but at a single SSL frame. It then returns up to LEN bytes it
1438 decrypted from this SSL frame. If the frame contained more data
1439 than requested it will return only LEN data, buffer the rest and
1440 return it on further read calls. This means, that it might be
1441 possible to read data, even if the underlying socket is not
1442 readable, so using poll or select might not be sufficient.
1443 sysread will only return data from a single SSL frame, e.g. either
1445 the pending data from the already buffered frame or it will read a
1446 frame from the underlying socket and return the decrypted data. It
1447 will not return data spanning several SSL frames in a single call.
1448 Also, calls to sysread might fail, because it must first finish an
1450 SSL handshake.
1451 To understand these behaviors is essential, if you write
1453 applications which use event loops and/or non-blocking sockets.
1454 Please read the specific sections in this documentation.
1455 syswrite( BUF, [ LEN, [ OFFSET ]] )
1457 This functions behaves from the outside the same as syswrite in
1458 other IO::Socket objects, e.g. it will write at most LEN bytes to
1459 the socket, but there is no guarantee, that all LEN bytes are
1460 written. It will return the number of bytes written. Because it
1461 basically just calls SSL_write from OpenSSL syswrite will write at
1462 most a single SSL frame. This means, that no more than 16.384
1463 bytes, which is the maximum size of an SSL frame, will be written
1464 at once.
1465 For non-blocking sockets SSL specific behavior applies. Pease read
1467 the specific section in this documentation.
1468 peek( BUF, LEN, [ OFFSET ])
1470 This function has exactly the same syntax as sysread, and performs
1471 nearly the same task but will not advance the read position so that
1472 successive calls to peek() with the same arguments will return the
1473 same results. This function requires OpenSSL 0.9.6a or later to
1474 work.
1475 pending()
1477 This function gives you the number of bytes available without
1478 reading from the underlying socket object. This function is
1479 essential if you work with event loops, please see the section
1480 about polling SSL sockets.
1481 get_fingerprint([algo,certificate,pubkey])
1483 This methods returns the fingerprint of the given certificate in
1484 the form "algo$digest_hex", where "algo" is the used algorithm,
1485 default 'sha256'. If no certificate is given the peer certificate
1486 of the connection is used. If "pubkey" is true it will not return
1487 the fingerprint of the certificate but instead the fingerprint of
1488 the pubkey inside the certificate as "algo$pub$digest_hex".
1489 get_fingerprint_bin([algo,certificate,pubkey])
1491 This methods returns the binary fingerprint of the given
1492 certificate by using the algorithm "algo", default 'sha256'. If no
1493 certificate is given the peer certificate of the connection is
1494 used. If "pubkey" is true it will not return the fingerprint of
1495 the certificate but instead the fingerprint of the pubkey inside
1496 the certificate.
1497 get_cipher()
1499 Returns the string form of the cipher that the IO::Socket::SSL
1500 object is using.
1501 get_sslversion()
1503 Returns the string representation of the SSL version of an
1504 established connection.
1505 get_sslversion_int()
1507 Returns the integer representation of the SSL version of an
1508 established connection.
1509 get_session_reused()
1511 This returns true if the session got reused and false otherwise.
1512 Note that with a reused session no certificates are send within the
1513 handshake and no ciphers are offered and thus functions which rely
1514 on this might not work.
1515 dump_peer_certificate()
1517 Returns a parsable string with select fields from the peer SSL
1518 certificate. This method directly returns the result of the
1519 dump_peer_certificate() method of Net::SSLeay.
1520 peer_certificate($field;[$refresh])
1522 If a peer certificate exists, this function can retrieve values
1523 from it. If no field is given the internal representation of
1524 certificate from Net::SSLeay is returned. If refresh is true it
1525 will not used a cached version, but check again in case the
1526 certificate of the connection has changed due to renegotiation.
1527 The following fields can be queried:
1529 authority (alias issuer)
1531 The certificate authority which signed the certificate.
1532 owner (alias subject)
1534 The owner of the certificate.
1535 commonName (alias cn) - only for Net::SSLeay version >=1.30
1537 The common name, usually the server name for SSL
1538 certificates.
1539 subjectAltNames - only for Net::SSLeay version >=1.33
1541 Alternative names for the subject, usually different names
1542 for the same server, like example.org, example.com,
1543 *.example.com.
1544 It returns a list of (typ,value) with typ GEN_DNS,
1546 GEN_IPADD etc (these constants are exported from
1547 IO::Socket::SSL). See
1548 Net::SSLeay::X509_get_subjectAltNames.
1549 sock_certificate($field)
1551 This is similar to "peer_certificate" but will return the sites own
1552 certificate. The same arguments for $field can be used. If no
1553 $field is given the certificate handle from the underlying OpenSSL
1554 will be returned. This handle will only be valid as long as the SSL
1555 connection exists and if used afterwards it might result in strange
1556 crashes of the application.
1557 peer_certificates
1559 This returns all the certificates send by the peer, e.g. first the
1560 peers own certificate and then the rest of the chain. You might use
1561 CERT_asHash from IO::Socket::SSL::Utils to inspect each of the
1562 certificates.
1563 This function depends on a version of Net::SSLeay >= 1.58 .
1565 get_servername
1567 This gives the name requested by the client if Server Name
1568 Indication (SNI) was used.
1569 verify_hostname($hostname,$scheme,$publicsuffix)
1571 This verifies the given hostname against the peer certificate using
1572 the given scheme. Hostname is usually what you specify within the
1573 PeerAddr. See the "SSL_verifycn_publicsuffix" parameter for an
1574 explanation of suffix checking and for the possible values.
1575 Verification of hostname against a certificate is different between
1577 various applications and RFCs. Some scheme allow wildcards for
1578 hostnames, some only in subjectAltNames, and even their different
1579 wildcard schemes are possible. RFC 6125 provides a good overview.
1580 To ease the verification the following schemes are predefined (both
1582 protocol name and rfcXXXX name can be used):
1583 rfc2818, xmpp (rfc3920), ftp (rfc4217)
1585 Extended wildcards in subjectAltNames and common name are
1586 possible, e.g. *.example.org or even www*.example.org. The
1587 common name will be only checked if no DNS names are given
1588 in subjectAltNames.
1589 http (alias www)
1591 While name checking is defined in rfc2818 the current
1592 browsers usually accept also an IP address (w/o wildcards)
1593 within the common name as long as no subjectAltNames are
1594 defined. Thus this is rfc2818 extended with this feature.
1595 smtp (rfc2595), imap, pop3, acap (rfc4642), netconf (rfc5538),
1597 syslog (rfc5425), snmp (rfc5953)
1598 Simple wildcards in subjectAltNames are possible, e.g.
1599 *.example.org matches www.example.org but not
1600 lala.www.example.org. If nothing from subjectAltNames match
1601 it checks against the common name, where wildcards are also
1602 allowed to match the full leftmost label.
1603 ldap (rfc4513)
1605 Simple wildcards are allowed in subjectAltNames, but not in
1606 common name. Common name will be checked even if
1607 subjectAltNames exist.
1608 sip (rfc5922)
1610 No wildcards are allowed and common name is checked even if
1611 subjectAltNames exist.
1612 gist (rfc5971)
1614 Simple wildcards are allowed in subjectAltNames and common
1615 name, but common name will only be checked if their are no
1616 DNS names in subjectAltNames.
1617 default This is a superset of all the rules and is automatically
1619 used if no scheme is given but a hostname (instead of IP)
1620 is known. Extended wildcards are allowed in
1621 subjectAltNames and common name and common name is checked
1622 always.
1623 none No verification will be done. Actually is does not make
1625 any sense to call verify_hostname in this case.
1626 The scheme can be given either by specifying the name for one of
1628 the above predefined schemes, or by using a hash which can have the
1629 following keys and values:
1630 check_cn: 0|'always'|'when_only'
1632 Determines if the common name gets checked. If 'always' it
1633 will always be checked (like in ldap), if 'when_only' it
1634 will only be checked if no names are given in
1635 subjectAltNames (like in http), for any other values the
1636 common name will not be checked.
1637 wildcards_in_alt: 0|'full_label'|'anywhere'
1639 Determines if and where wildcards in subjectAltNames are
1640 possible. If 'full_label' only cases like *.example.org
1641 will be possible (like in ldap), for 'anywhere'
1642 www*.example.org is possible too (like http), dangerous
1643 things like but www.*.org or even '*' will not be allowed.
1644 For compatibility with older versions 'leftmost' can be
1645 given instead of 'full_label'.
1646 wildcards_in_cn: 0|'full_label'|'anywhere'
1648 Similar to wildcards_in_alt, but checks the common name.
1649 There is no predefined scheme which allows wildcards in
1650 common names.
1651 ip_in_cn: 0|1|4|6
1653 Determines if an IP address is allowed in the common name
1654 (no wildcards are allowed). If set to 4 or 6 it only allows
1655 IPv4 or IPv6 addresses, any other true value allows both.
1656 callback: \&coderef
1658 If you give a subroutine for verification it will be called
1659 with the arguments
1660 ($hostname,$commonName,@subjectAltNames), where hostname is
1661 the name given for verification, commonName is the result
1662 from peer_certificate('cn') and subjectAltNames is the
1663 result from peer_certificate('subjectAltNames').
1664 All other arguments for the verification scheme will be
1666 ignored in this case.
1667 next_proto_negotiated()
1669 This method returns the name of negotiated protocol - e.g.
1670 'http/1.1'. It works for both client and server side of SSL
1671 connection.
1672 NPN support is available with Net::SSLeay 1.46+ and openssl-1.0.1+.
1674 To check support you might call "IO::Socket::SSL->can_npn()".
1675 alpn_selected()
1677 Returns the protocol negotiated via ALPN as a string, e.g.
1678 'http/1.1', 'http/2.0' or 'spdy/3.1'.
1679 ALPN support is available with Net::SSLeay 1.56+ and
1681 openssl-1.0.2+. To check support, use
1682 "IO::Socket::SSL->can_alpn()".
1683 errstr()
1685 Returns the last error (in string form) that occurred. If you do
1686 not have a real object to perform this method on, call
1687 IO::Socket::SSL::errstr() instead.
1688 For read and write errors on non-blocking sockets, this method may
1690 include the string "SSL wants a read first!" or "SSL wants a write
1691 first!" meaning that the other side is expecting to read from or
1692 write to the socket and wants to be satisfied before you get to do
1693 anything. But with version 0.98 you are better comparing the global
1694 exported variable $SSL_ERROR against the exported symbols
1695 SSL_WANT_READ and SSL_WANT_WRITE.
1696 opened()
1698 This returns false if the socket could not be opened, 1 if the
1699 socket could be opened and the SSL handshake was successful done
1700 and -1 if the underlying IO::Handle is open, but the SSL handshake
1701 failed.
1702 IO::Socket::SSL->start_SSL($socket, ... )
1704 This will convert a glob reference or a socket that you provide to
1705 an IO::Socket::SSL object. You may also pass parameters to
1706 specify context or connection options as with a call to new(). If
1707 you are using this function on an accept()ed socket, you must set
1708 the parameter "SSL_server" to 1, i.e.
1709 IO::Socket::SSL->start_SSL($socket, SSL_server => 1). If you have
1710 a class that inherits from IO::Socket::SSL and you want the $socket
1711 to be blessed into your own class instead, use
1712 MyClass->start_SSL($socket) to achieve the desired effect.
1713 Note that if start_SSL() fails in SSL negotiation, $socket will
1715 remain blessed in its original class. For non-blocking sockets
1716 you better just upgrade the socket to IO::Socket::SSL and call
1717 accept_SSL or connect_SSL and the upgraded object. To just upgrade
1718 the socket set SSL_startHandshake explicitly to 0. If you call
1719 start_SSL w/o this parameter it will revert to blocking behavior
1720 for accept_SSL and connect_SSL.
1721 If given the parameter "Timeout" it will stop if after the timeout
1723 no SSL connection was established. This parameter is only used for
1724 blocking sockets, if it is not given the default Timeout from the
1725 underlying IO::Socket will be used.
1726 stop_SSL(...)
1728 This is the opposite of start_SSL(), connect_SSL() and
1729 accept_SSL(), e.g. it will shutdown the SSL connection and return
1730 to the class before start_SSL(). It gets the same arguments as
1731 close(), in fact close() calls stop_SSL() (but without downgrading
1732 the class).
1733 Will return true if it succeeded and undef if failed. This might be
1735 the case for non-blocking sockets. In this case $! is set to
1736 EWOULDBLOCK and the ssl error to SSL_WANT_READ or SSL_WANT_WRITE.
1737 In this case the call should be retried again with the same
1738 arguments once the socket is ready.
1739 For calling from "stop_SSL" "SSL_fast_shutdown" default to false,
1741 e.g. it waits for the close_notify of the peer. This is necessary
1742 in case you want to downgrade the socket and continue to use it as
1743 a plain socket.
1744 After stop_SSL the socket can again be used to exchange plain data.
1746 connect_SSL, accept_SSL
1748 These functions should be used to do the relevant handshake, if the
1749 socket got created with "new" or upgraded with "start_SSL" and
1750 "SSL_startHandshake" was set to false. They will return undef
1751 until the handshake succeeded or an error got thrown. As long as
1752 the function returns undef and $! is set to EWOULDBLOCK one could
1753 retry the call after the socket got readable (SSL_WANT_READ) or
1754 writeable (SSL_WANT_WRITE).
1755 ocsp_resolver
1757 This will create an OCSP resolver object, which can be used to
1758 create OCSP requests for the certificates of the SSL connection.
1759 Which certificates are verified depends on the setting of
1760 "SSL_ocsp_mode": by default only the leaf certificate will be
1761 checked, but with SSL_OCSP_FULL_CHAIN all chain certificates will
1762 be checked.
1763 Because to create an OCSP request the certificate and its issuer
1765 certificate need to be known it is not possible to check
1766 certificates when the trust chain is incomplete or if the
1767 certificate is self-signed.
1768 The OCSP resolver gets created by calling "$ssl->ocsp_resolver" and
1770 provides the following methods:
1771 hard_error
1773 This returns the hard error when checking the OCSP
1774 response. Hard errors are certificate revocations. With
1775 the "SSL_ocsp_mode" of SSL_OCSP_FAIL_HARD any soft error
1776 (e.g. failures to get signed information about the
1777 certificates) will be considered a hard error too.
1778 The OCSP resolving will stop on the first hard error.
1780 The method will return undef as long as no hard errors
1782 occurred and still requests to be resolved. If all requests
1783 got resolved and no hard errors occurred the method will
1784 return ''.
1785 soft_error
1787 This returns the soft error(s) which occurred when asking
1788 the OCSP responders.
1789 requests
1791 This will return a hash consisting of
1792 "(url,request)"-tuples, e.g. which contain the OCSP request
1793 string and the URL where it should be sent too. The usual
1794 way to send such a request is as HTTP POST request with a
1795 content-type of "application/ocsp-request" or as a GET
1796 request with the base64 and url-encoded request is added to
1797 the path of the URL.
1798 After you've handled all these requests and added the
1800 response with "add_response" you should better call this
1801 method again to make sure, that no more requests are
1802 outstanding. IO::Socket::SSL will combine multiple OCSP
1803 requests for the same server inside a single request, but
1804 some server don't give a response to all these requests, so
1805 that one has to ask again with the remaining requests.
1806 add_response($uri,$response)
1808 This method takes the HTTP body of the response which got
1809 received when sending the OCSP request to $uri. If no
1810 response was received or an error occurred one should
1811 either retry or consider $response as empty which will
1812 trigger a soft error.
1813 The method returns the current value of "hard_error", e.g.
1815 a defined value when no more requests need to be done.
1816 resolve_blocking(%args)
1818 This combines "requests" and "add_response" which
1819 HTTP::Tiny to do all necessary requests in a blocking way.
1820 %args will be given to HTTP::Tiny so that you can put proxy
1821 settings etc here. HTTP::Tiny will be called with
1822 "verify_SSL" of false, because the OCSP responses have
1823 their own signatures so no extra SSL verification is
1824 needed.
1825 If you don't want to use blocking requests you need to roll
1827 your own user agent with "requests" and "add_response".
1828 IO::Socket::SSL->new_from_fd($fd, [mode], %sslargs)
1830 This will convert a socket identified via a file descriptor into an
1831 SSL socket. Note that the argument list does not include a "MODE"
1832 argument; if you supply one, it will be thoughtfully ignored (for
1833 compatibility with IO::Socket::INET). Instead, a mode of '+<' is
1834 assumed, and the file descriptor passed must be able to handle such
1835 I/O because the initial SSL handshake requires bidirectional
1836 communication.
1837 Internally the given $fd will be upgraded to a socket object using
1839 the "new_from_fd" method of the super class (IO::Socket::INET or
1840 similar) and then "start_SSL" will be called using the given
1841 %sslargs. If $fd is already an IO::Socket object you should better
1842 call "start_SSL" directly.
1843 IO::Socket::SSL::default_ca([ path|dir| SSL_ca_file = ..., SSL_ca_path
1845 => ... ])>
1846 Determines or sets the default CA path. If existing path or dir or
1847 a hash is given it will set the default CA path to this value and
1848 never try to detect it automatically. If "undef" is given it will
1849 forget any stored defaults and continue with detection of system
1850 defaults. If no arguments are given it will start detection of
1851 system defaults, unless it has already stored user-set or
1852 previously detected values.
1853 The detection of system defaults works similar to OpenSSL, e.g. it
1855 will check the directory specified in environment variable
1856 SSL_CERT_DIR or the path OPENSSLDIR/certs (SSLCERTS: on VMS) and
1857 the file specified in environment variable SSL_CERT_FILE or the
1858 path OPENSSLDIR/cert.pem (SSLCERTS:cert.pem on VMS). Contrary to
1859 OpenSSL it will check if the SSL_ca_path contains PEM files with
1860 the hash as file name and if the SSL_ca_file looks like PEM. If no
1861 usable system default can be found it will try to load and use
1862 Mozilla::CA and if not available give up detection. The result of
1863 the detection will be saved to speed up future calls.
1864 The function returns the saved default CA as hash with SSL_ca_file
1866 and SSL_ca_path.
1867 IO::Socket::SSL::set_default_context(...)
1869 You may use this to make IO::Socket::SSL automatically re-use a
1870 given context (unless specifically overridden in a call to new()).
1871 It accepts one argument, which should be either an IO::Socket::SSL
1872 object or an IO::Socket::SSL::SSL_Context object. See the
1873 SSL_reuse_ctx option of new() for more details. Note that this
1874 sets the default context globally, so use with caution (esp. in
1875 mod_perl scripts).
1876 IO::Socket::SSL::set_default_session_cache(...)
1878 You may use this to make IO::Socket::SSL automatically re-use a
1879 given session cache (unless specifically overridden in a call to
1880 new()). It accepts one argument, which should be an
1881 IO::Socket::SSL::Session_Cache object or similar (e.g. something
1882 which implements get_session, add_session and del_session like
1883 IO::Socket::SSL::Session_Cache does). See the SSL_session_cache
1884 option of new() for more details. Note that this sets the default
1885 cache globally, so use with caution.
1886 IO::Socket::SSL::set_defaults(%args)
1888 With this function one can set defaults for all SSL_* parameter
1889 used for creation of the context, like the SSL_verify* parameter.
1890 Any SSL_* parameter can be given or the following short versions:
1891 mode - SSL_verify_mode
1893 callback - SSL_verify_callback
1894 scheme - SSL_verifycn_scheme
1895 name - SSL_verifycn_name
1896 IO::Socket::SSL::set_client_defaults(%args)
1897 Similar to "set_defaults", but only sets the defaults for client
1898 mode.
1899 IO::Socket::SSL::set_server_defaults(%args)
1901 Similar to "set_defaults", but only sets the defaults for server
1902 mode.
1903 IO::Socket::SSL::set_args_filter_hack(\&code|'use_defaults')
1905 Sometimes one has to use code which uses unwanted or invalid
1906 arguments for SSL, typically disabling SSL verification or setting
1907 wrong ciphers or SSL versions. With this hack it is possible to
1908 override these settings and restore sanity. Example:
1909 IO::Socket::SSL::set_args_filter_hack( sub {
1911 my ($is_server,$args) = @_;
1912 if ( ! $is_server ) {
1913 # client settings - enable verification with default CA
1914 # and fallback hostname verification etc
1915 delete @{$args}{qw(
1916 SSL_verify_mode
1917 SSL_ca_file
1918 SSL_ca_path
1919 SSL_verifycn_scheme
1920 SSL_version
1921 )};
1922 # and add some fingerprints for known certs which are signed by
1923 # unknown CAs or are self-signed
1924 $args->{SSL_fingerprint} = ...
1925 }
1926 });
1927 With the short setting "set_args_filter_hack('use_defaults')" it
1929 will prefer the default settings in all cases. These default
1930 settings can be modified with "set_defaults", "set_client_defaults"
1931 and "set_server_defaults".
1932 The following methods are unsupported (not to mention futile!) and
1934 IO::Socket::SSL will emit a large CROAK() if you are silly enough to
1935 use them:
1936 truncate
1938 stat
1939 ungetc
1940 setbuf
1941 setvbuf
1942 fdopen
1943 send/recv
1944 Note that send() and recv() cannot be reliably trapped by a tied
1945 filehandle (such as that used by IO::Socket::SSL) and so may send
1946 unencrypted data over the socket. Object-oriented calls to these
1947 functions will fail, telling you to use the print/printf/syswrite
1948 and read/sysread families instead.
1949
1951 The following functions are deprecated and are only retained for
1952 compatibility:
1953 context_init()
1955 use the SSL_reuse_ctx option if you want to re-use a context
1956 socketToSSL() and socket_to_SSL()
1958 use IO::Socket::SSL->start_SSL() instead
1959 kill_socket()
1961 use close() instead
1962 get_peer_certificate()
1964 use the peer_certificate() function instead. Used to return
1965 X509_Certificate with methods subject_name and issuer_name. Now
1966 simply returns $self which has these methods (although deprecated).
1967 issuer_name()
1969 use peer_certificate( 'issuer' ) instead
1970 subject_name()
1972 use peer_certificate( 'subject' ) instead
1973
1975 See the 'example' directory, the tests in 't' and also the tools in
1976 'util'.
1977
1979 If you use IO::Socket::SSL together with threads you should load it
1980 (e.g. use or require) inside the main thread before creating any other
1981 threads which use it. This way it is much faster because it will be
1982 initialized only once. Also there are reports that it might crash the
1983 other way.
1984 Creating an IO::Socket::SSL object in one thread and closing it in
1986 another thread will not work.
1987 IO::Socket::SSL does not work together with
1989 Storable::fd_retrieve/fd_store. See BUGS file for more information and
1990 how to work around the problem.
1991 Non-blocking and timeouts (which are based on non-blocking) are not
1993 supported on Win32, because the underlying IO::Socket::INET does not
1994 support non-blocking on this platform.
1995 If you have a server and it looks like you have a memory leak you might
1997 check the size of your session cache. Default for Net::SSLeay seems to
1998 be 20480, see the example for SSL_create_ctx_callback for how to limit
1999 it.
2000 TLS 1.3 support regarding session reuse is incomplete.
2002
2004 IO::Socket::INET, IO::Socket::INET6, IO::Socket::IP, Net::SSLeay.
2005
2007 Many thanks to all who added patches or reported bugs or helped
2008 IO::Socket::SSL another way. Please keep reporting bugs and help with
2009 patches, even if they just fix the documentation.
2010 Special thanks to the team of Net::SSLeay for the good cooperation.
2012
2014 Steffen Ullrich, <sullr at cpan.org> is the current maintainer.
2015 Peter Behroozi, <behrooz at fas.harvard.edu> (Note the lack of an "i"
2017 at the end of "behrooz")
2018 Marko Asplund, <marko.asplund at kronodoc.fi>, was the original author
2020 of IO::Socket::SSL.
2021 Patches incorporated from various people, see file Changes.
2023
2025 The original versions of this module are Copyright (C) 1999-2002 Marko
2026 Asplund.
2027 The rewrite of this module is Copyright (C) 2002-2005 Peter Behroozi.
2029 Versions 0.98 and newer are Copyright (C) 2006-2014 Steffen Ullrich.
2031 This module is free software; you can redistribute it and/or modify it
2033 under the same terms as Perl itself.
2034perl v5.32.1 2021-03-19 IO::Socket::SSL(3)