aboutsummaryrefslogtreecommitdiffstats
path: root/lib/ssl/doc/src/new_ssl.xml
blob: a83c2d13837298dd080d90fef7be25808ada35d5 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
<?xml version="1.0" encoding="latin1" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>1999</year>
      <year>2007</year>
      <holder>Ericsson AB, All Rights Reserved</holder>
    </copyright>
    <legalnotice>
  The contents of this file are subject to the Erlang Public License,
  Version 1.1, (the "License"); you may not use this file except in
  compliance with the License. You should have received a copy of the
  Erlang Public License along with this software. If not, it can be
  retrieved aniline's at http://www.erlang.org/.

  Software distributed under the License is distributed on an "AS IS"
  basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
  the License for the specific language governing rights and limitations
  under the License.

  The Initial Developer of the Original Code is Ericsson AB.
    </legalnotice>

    <title>ssl</title>
    <prepared>Ingela Anderton Andin</prepared>
    <responsible>Ingela Anderton Andin</responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date>2003-03-25</date>
    <rev></rev>
    <file>new_ssl.xml</file>
  </header>
  <module>new_ssl</module>
  <modulesummary>Interface Functions for Secure Socket Layer</modulesummary>
  <description>
    <p>This module contains interface functions to the Secure Socket
      Layer. 
    </p>
  </description>
  
  <section>
    <title>NEW SSL</title>

    <p>This manual page describes functions that are defined
      in the ssl module and represents the new ssl implementation
      that coexists with the old one, as the new implementation
      is not yet complete enough to replace the old one.</p>
       
    <p>The new implementation can be
      accessed by providing the option {ssl_imp, new} to the
      ssl:connect and ssl:listen functions.</p>
    
    <p>The new implementation is Erlang based and all logic
      is in Erlang and only payload encryption calculations are
      done in C via the crypto application. The main reason for
      making a new implementation is that the old solution was
      very crippled as the control of the ssl-socket was deep
      down in openssl making it hard if not impossible to
      support all inet options, ipv6 and upgrade of a tcp
      connection to a ssl connection. This version has a
      few limitations that will be removed before the ssl-4.0
      release. Main differences and limitations are listed below.</p>

    <list type="bulleted">
      <item>New ssl requires the crypto
	application.</item>
      <item>The option reuseaddr is
	supported and the default value is false as in gen_tcp.
	Old ssl is patched to accept that the option is set to
	true to provide a smoother migration between the
	versions. In old ssl the option is hard coded to
	true.</item>
      <item>ssl:version/0 is replaced by
            ssl:versions/0</item>
      <item>ssl:ciphers/0 is replaced by
            ssl:cipher_suites/0</item>
      <item>ssl:pid/1 is a
            meaningless function in new ssl and will be deprecated in
            ssl-4.0 until it is removed it will return a valid but
            meaningless pid.</item>
      <item>New API functions are
            ssl:shutdown/2, ssl:cipher_suites/[0,1] and
            ssl:versions/0</item>
      <item>CRL and policy certificate
            extensions are not supported yet. </item>
      <item>Supported SSL/TLS-versions are SSL-3.0 and TLS-1.0 </item>
      <item>For security reasons sslv2 is not supported.</item>
    </list>
 
  </section>
  
  <section>
    <title>COMMON DATA TYPES</title>
    <p>The following data types are used in the functions below:
    </p>

    <p><c>boolean() = true | false</c></p> 
    
    <p><c>property() = atom()</c></p>
    
    <p><c>option() = socketoption() | ssloption() | transportoption()</c></p>

     <p><c>socketoption() = [{property(), term()}] - defaults to
      [{mode,list},{packet, 0},{header, 0},{active, true}].
    </c></p>

    <p>For valid options
      see <seealso marker="kernel:inet">inet(3) </seealso> and
      <seealso marker="kernel:gen_tcp">gen_tcp(3) </seealso>.
    </p>
    
    <p> <c>ssloption() = {verify, verify_type()} |
      {fail_if_no_peer_cert, boolean()}
      {depth, integer()} |
      {certfile, path()} | {keyfile, path()} | {password, string()} |
      {cacertfile, path()} | {dhfile, path()} | {ciphers, ciphers()} |
      {ssl_imp, ssl_imp()} | {reuse_sessions, boolean()} | {reuse_session, fun()} 
    </c></p>

    <p><c>transportoption() = {CallbackModule, DataTag, ClosedTag}
	- defaults to {gen_tcp, tcp, tcp_closed}. Ssl may be
	run over any reliable transport protocol that has
	an equivalent API to gen_tcp's.</c></p>
    
    <p><c>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; CallbackModule =
	atom()</c>
    </p> <p><c>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; DataTag =
	atom() - tag used in socket data message.</c></p>
    <p><c>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ClosedTag = atom() - tag used in
    socket close message.</c></p>

    <p><c>verify_type() = verify_none | verify_peer</c></p>
    
    <p><c>path() = string() - representing a file path.</c></p>
    
    <p><c>host() = hostname() | ipaddress()</c></p>
        
    <p><c>hostname() = string()</c></p>
    
    <p><c>
      ip_address() = {N1,N2,N3,N4}  % IPv4
      | {K1,K2,K3,K4,K5,K6,K7,K8}  % IPv6    </c></p>

    <p><c>sslsocket() - opaque to the user. </c></p>
    
    <p><c>protocol() = sslv3 | tlsv1 </c></p>
    
    <p><c>ciphers() = [ciphersuite()] | sting() (according to old API)</c></p>
    
    <p><c>ciphersuite() =
      {key_exchange(), cipher(), hash(), exportable()}</c></p>
    
    <p><c>key_exchange() =  rsa | dh_dss | dh_rsa | dh_anon | dhe_dss
      | dhe_rsa | krb5 | KeyExchange_export
    </c></p>

   <p><c>cipher() = rc4_128 | idea_cbc | des_cbc | '3des_ede_cbc'
      des40_cbc | dh_dss | aes_128_cbc | aes_256_cbc |
      rc2_cbc_40 | rc4_40  </c></p>

   <p> <c>hash() = md5 | sha
    </c></p>

   <p> <c>exportable() = export | no_export | ignore
    </c></p>

    <p><c>ssl_imp() = new | old - default is old.</c></p>
    
  </section>
  
<section>
    <title>SSL OPTION DESCRIPTIONS</title>
    
    <taglist>
      <tag>{verify, verify_type()}</tag>
      <item> If <c>verify_none</c> is specified x509-certificate
      path validation errors at the client side
      will not  automatically cause the connection to fail, as
      it will if the verify type is <c>verify_peer</c>. See also
      the option verify_fun.
      Servers only do the path validation if <c>verify_peer</c> is set to
      true, as it then will 
      send a certificate request to
      the client (this message is not sent if the verify option is
      <c>verify_none</c>) and you may then also want to specify
      the option <c>fail_if_no_peer_cert</c>.
      </item>

      <tag>{fail_if_no_peer_cert, boolean()}</tag>
      <item>Used together with {verify, verify_peer} by a ssl server.
      If set to true,
      the server will fail if the client does not have a certificate
      to send, e.i sends a empty certificate, if set to false it will
      only fail if the client sends a invalid certificate (an empty
      certificate is considered valid).
      </item>
      
      <tag>{verify_fun, fun(ErrorList) -> boolean()}</tag>
      <item>Used by the ssl client to determine if 
	x509-certificate path validations errors are acceptable or
	if the connection should fail. Defaults to:
       
<code>
fun(ErrorList) ->
	case lists:foldl(fun({bad_cert,unknown_ca}, Acc) ->
						  Acc;
			    (Other, Acc) ->
				 [Other | Acc]
			 end, [], ErrorList) of
	    [] ->
		true;
	    [_|_] ->
		false
	end
end
</code>
       I.e. by default if the only error found was that the CA-certificate
       holder was unknown this will be accepted.

       Possible errors in the error list are: 
       {bad_cert, cert_expired}, {bad_cert, invalid_issuer},
       {bad_cert, invalid_signature}, {bad_cert, name_not_permitted},
       {bad_cert, unknown_ca},
       {bad_cert, cert_expired}, {bad_cert, invalid_issuer},
       {bad_cert, invalid_signature}, {bad_cert, name_not_permitted},
       {bad_cert, cert_revoked} (not implemented yet),
       {bad_cert, unknown_critical_extension} or {bad_cert, term()} (Will
								    be relevant later when an option is added for the user to be able to verify application specific extensions.) 
      </item>
      
      <tag>{depth, integer()}</tag>
      <item>Specifies the maximum
      verification depth, i.e. how far in a chain of certificates the
      verification process can proceed before the verification is
      considered to fail. Peer certificate = 0, CA certificate = 1,
      higher level CA certificate = 2, etc.  The value 2 thus means
      that a chain can at most contain peer cert, CA cert, next CA
      cert, and an additional CA cert. The default value is 1.
      </item>

      <tag>{certfile, path()}</tag>
      <item>Path to a file containing the
          user's certificate. Optional for clients but note
      that some servers requires that the client can certify
      itself. </item>
      <tag>{keyfile, path()}</tag>
      <item>Path to file containing user's
      private PEM encoded key. As PEM-files may contain several
      entries this option defaults to the same file as given by
      certfile option.</item>
      <tag>{password, string()}</tag>
      <item>String containing the user's password.
	Only used if the private keyfile is password protected.
      </item>
      <tag>{cacertfile, path()}</tag>
      <item>Path to file containing PEM encoded
      CA certificates (trusted certificates used for verifying a peer
      certificate). May be omitted if you do not want to verify
      the peer.</item>

      <tag>{dhfile, path()}</tag>
      <item>Path to file containing PEM encoded Diffie Hellman parameters,
      for the server to use if a cipher suite using Diffie Hellman key exchange
      is negotiated. If not specified hardcode parameters will be used.
      </item>
      
      <tag>{ciphers, ciphers()}</tag>
      <item>The function <c>ciphers_suites/0</c> can
	be used to find all available ciphers.
      </item>

      <tag>{ssl_imp, ssl_imp()}</tag>
      <item>Specify which ssl implementation you want to use.
      </item>

      <tag>{reuse_sessions, boolean()}</tag>
      <item>Specifies if ssl sessions should be reused
	when possible.
      </item>

       <tag>{reuse_session, fun(SuggestedSessionId,
       PeerCert, Compression, CipherSuite) -> boolean()}</tag>
      <item>Enables the ssl server to have a local policy
      for deciding if a session should be reused or not,
      only meaning full if <c>reuse_sessions</c> is set to true.
      SuggestedSessionId is a binary(),  PeerCert is a DER encoded
      certificate, Compression is an enumeration integer
      and CipherSuite of type ciphersuite().      
      </item>
    </taglist>
  </section>
  
  <section>
    <title>General</title>
      
    <p>When a ssl socket is in active mode (the default), data from the
      socket is delivered to the owner of the socket in the form of
      messages:
    </p>
    <list type="bulleted">
      <item>{ssl, Socket, Data}
      </item>
      <item>{ssl_closed, Socket}
      </item>
      <item>
        {ssl_error, Socket, Reason}
      </item>
    </list>
    
    <p>A <c>Timeout</c> argument specifies a timeout in milliseconds. The 
      default value for a <c>Timeout</c> argument is <c>infinity</c>.
    </p>
  </section>
  
  <funcs>
    <func>
      <name>cipher_suites() -></name>
      <name>cipher_suites(Type) -> ciphers()</name>
      <fsummary> Returns a list of supported cipher suites</fsummary>
      <type>
        <v>Type = erlang | openssl</v>

      </type>
      <desc><p>Returns a list of supported cipher suites.
	cipher_suites() is equivalent to cipher_suites(erlang).
	Type openssl is provided for backwards compatibility with
	old ssl that used openssl.
	</p>
    </desc>
    </func>
    
    <func>
      <name>connect(Socket, SslOptions) -> </name>
      <name>connect(Socket, SslOptions, Timeout) -> {ok, SslSocket}
	| {error, Reason}</name>
      <fsummary> Upgrades a gen_tcp, or
	equivalent, connected socket to a ssl socket. </fsummary>
      <type>
        <v>Socket = socket()</v>
        <v>SslOptions = [ssloption()]</v>
	<v>Timeout = integer() | infinity</v>
	<v>SslSocket = sslsocket()</v>
	<v>Reason = term()</v>
      </type>
      <desc> <p>Upgrades a gen_tcp, or equivalent,
	  connected socket to a ssl socket e.i performs the
	  client-side ssl handshake.</p>
    </desc>
    </func>

    <func>
      <name>connect(Host, Port, Options) -></name>
      <name>connect(Host, Port, Options, Timeout) ->
	  {ok, SslSocket} | {error, Reason}</name>
      <fsummary>Opens an ssl connection to Host, Port. </fsummary>
      <type>
	  <v>Host = host()</v>
	  <v>Port = integer()</v>
	  <v>Options = [option()]</v>
	  <v>Timeout = integer() | infinity</v>
	  <v>SslSocket = sslsocket()</v>
	  <v>Reason = term()</v>
      </type>
      <desc> <p>Opens an ssl connection to Host, Port.</p> </desc>
    </func>

    <func>
      <name>close(SslSocket) -> ok | {error, Reason}</name>
      <fsummary>Close a ssl connection</fsummary>
      <type>
	  <v>SslSocket = sslsocket()</v>
	  <v>Reason = term()</v>
      </type>
      <desc><p>Close a ssl connection.</p>
      </desc>
    </func>

    <func>
      <name>controlling_process(SslSocket, NewOwner) ->
	ok | {error, Reason}</name>
      
	<fsummary>Assigns a new controlling process to the
	ssl-socket.</fsummary>
      
	<type>
	  <v>SslSocket = sslsocket()</v>
	  <v>NewOwner = pid()</v>
	  <v>Reason = term()</v>
	</type>
	<desc><p>Assigns a new controlling process to the ssl-socket. A
      controlling process is the owner of a ssl-socket, and receives
      all messages from the socket.</p>
      </desc>
    </func>

    <func>
	<name>connection_info(SslSocket) ->
	  {ok, {ProtocolVersion, CipherSuite}} |  {error, Reason} </name>
      <fsummary>Returns the negotiated protocol version and cipher suite.
      </fsummary>
      <type>
        <v>CipherSuite = ciphersuite()</v>
        <v>ProtocolVersion = protocol()</v>
      </type>
      <desc><p>Returns the negotiated protocol version and cipher suite.</p> 
      </desc>
    </func>

    <func>
      <name>getopts(Socket) -> </name>
      <name>getopts(Socket, OptionNames) ->
	{ok, [socketoption()]} | {error, Reason}</name>
      <fsummary>Get the value of the specified options.</fsummary>
      <type>
	<v>Socket = sslsocket()</v>
	<v>OptionNames = [property()]</v>
      </type>
      <desc>
	<p>Get the value of the specified socket options, if no
	  options are specified all options are returned.
	</p>
      </desc>
    </func>

    <func>
      <name>listen(Port, Options) ->
	{ok, ListenSocket} | {error, Reason}</name>
      <fsummary>Creates a ssl listen socket.</fsummary>
      <type>
	<v>Port = integer()</v>
	<v>Options = options()</v>
	<v>ListenSocket = sslsocket()</v>
      </type>
      <desc>
	<p>Creates a ssl listen socket.</p>
      </desc>
    </func>

    <func>
      <name>peercert(Socket) -> {ok, Cert} | {error, Reason}</name>
      <fsummary>Return the peer certificate.</fsummary>
     <type>
        <v>Socket = sslsocket()</v>
        <v>Cert = binary()</v>
        <v>Subject = term()</v>
      </type>
      <desc>
        <p>The peer certificate is returned as a DER encoded binary.
	  The certificate can be decoded with <c>public_key:pkix_decode_cert/2</c>.
        </p>
      </desc>
    </func>
    <func>
      <name>peername(Socket) -> {ok, {Address, Port}} |
	{error, Reason}</name>
      <fsummary>Return peer address and port.</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>Address = ipaddress()</v>
        <v>Port = integer()</v>
      </type>
      <desc>
        <p>Returns the address and port number of the peer.</p>
      </desc>
    </func>
    
    <func>
      <name>recv(Socket, Length) -> </name>
      <name>recv(Socket, Length, Timeout) -> {ok, Data} | {error,
	Reason}</name>
      <fsummary>Receive data on a socket.</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>Length = integer()</v>
        <v>Timeout = integer()</v>
        <v>Data = [char()] | binary()</v>
      </type>
      <desc>
        <p>This function receives a packet from a socket in passive
          mode. A closed socket is indicated by a return value
          <c>{error, closed}</c>.</p>
        <p>The <c>Length</c> argument is only meaningful when
          the socket is in <c>raw</c> mode and denotes the number of
          bytes to read. If <c>Length</c> = 0, all available bytes are
          returned. If <c>Length</c> &gt; 0, exactly <c>Length</c>
          bytes are returned, or an error; possibly discarding less
          than <c>Length</c> bytes of data when the socket gets closed
          from the other side.</p>
        <p>The optional <c>Timeout</c> parameter specifies a timeout in
          milliseconds. The default value is <c>infinity</c>.</p>
      </desc>
    </func>
    
    <func>
      <name>renegotiate(Socket) -> ok</name>
      <fsummary> Initiates a new handshake.</fsummary>
      <type>
	<v>Socket = sslsocket()</v>
      </type>
      <desc><p>Initiates a new handshake.</p>
      </desc>
    </func>
    
    <func>
      <name>send(Socket, Data) -> ok | {error, Reason}</name>
      <fsummary>Write data to a socket.</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>Data = iolist() | binary()</v>
      </type>
      <desc>
        <p>Writes <c>Data</c> to <c>Socket</c>. </p>
        <p>A notable return value is <c>{error, closed}</c> indicating that
          the socket is closed.</p>
      </desc>
    </func>
    <func>
      <name>setopts(Socket, Options) -> ok | {error, Reason}</name>
      <fsummary>Set socket options.</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>Options = [socketoption]()</v>
      </type>
      <desc>
        <p>Sets options according to <c>Options</c> for the socket 
          <c>Socket</c>. </p>
      </desc>
    </func>

    <func>
      <name>shutdown(Socket, How) -> ok | {error, Reason}</name>
      <fsummary>Immediately close a socket</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>How = read | write | read_write</v>
        <v>Reason = reason()</v>
      </type>
      <desc>
        <p>Immediately close a socket in one or two directions.</p>
        <p><c>How == write</c> means closing the socket for writing,
          reading from it is still possible.</p>
        <p>To be able to handle that the peer has done a shutdown on
          the write side, the <c>{exit_on_close, false}</c> option
          is useful.</p>
      </desc>
    </func>
    
    <func>
      <name>ssl_accept(ListenSocket) -> </name>
      <name>ssl_accept(ListenSocket, Timeout) -> ok | {error, Reason}</name>
      <fsummary>Perform server-side SSL handshake</fsummary>
      <type>
        <v>ListenSocket = sslsocket()</v>
        <v>Timeout = integer()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>The <c>ssl_accept</c> function establish the SSL connection
          on the server side. It should be called directly after
          <c>transport_accept</c>, in the spawned server-loop.</p>
      </desc>
    </func>

    <func>
      <name>ssl_accept(ListenSocket, SslOptions) -> </name>
      <name>ssl_accept(ListenSocket, SslOptions, Timeout) -> {ok, Socket} | {error, Reason}</name>
      <fsummary>Perform server-side SSL handshake</fsummary>
      <type>
        <v>ListenSocket = socket()</v>
	<v>SslOptions = ssloptions()</v>
        <v>Timeout = integer()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p> Upgrades a gen_tcp, or
	  equivalent, socket to a ssl socket e.i performs the
	ssl server-side handshake.</p>
      </desc>
    </func>
    
    <func>
      <name>sockname(Socket) -> {ok, {Address, Port}} |
	{error, Reason}</name>
      <fsummary>Return the local address and port.</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>Address = ipaddress()</v>
        <v>Port = integer()</v>
      </type>
      <desc>
        <p>Returns the local address and port number of the socket
          <c>Socket</c>.</p>
      </desc>
    </func>
    
    <func>
      <name>start() -> </name>
      <name>start(Type) -> ok | {error, Reason}</name>
      <fsummary>Starts the Ssl application. </fsummary>
      <type>
        <v>Type =  permanent | transient | temporary</v>
      </type>
      <desc>
        <p>Starts the Ssl application. Default type
          is temporary.
          <seealso marker="kernel:application">application(3)</seealso></p>
      </desc>
    </func>
    <func>
      <name>stop() -> ok </name>
      <fsummary>Stops the Ssl application.</fsummary>
      <desc>
        <p>Stops the Ssl application.
          <seealso marker="kernel:application">application(3)</seealso></p>
      </desc>
    </func>

    <func>
      <name>transport_accept(Socket) -></name>
      <name>transport_accept(Socket, Timeout) ->
	{ok, NewSocket} | {error, Reason}</name>
      <fsummary>Accept an incoming connection and
	prepare for <c>ssl_accept</c></fsummary>
      <type>
        <v>Socket = NewSocket = sslsocket()</v>
        <v>Timeout = integer()</v>
        <v>Reason = reason()</v>
      </type>
      <desc>
        <p>Accepts an incoming connection request on a listen socket.
          <c>ListenSocket</c> must be a socket returned from
          <c>listen/2</c>.  The socket returned should be passed to
          <c>ssl_accept</c> to complete ssl handshaking and
          establishing the connection.</p>
        <warning>
          <p>The socket returned can only be used with <c>ssl_accept</c>,
            no traffic can be sent or received before that call.</p>
        </warning>
        <p>The accepted socket inherits the options set for
          <c>ListenSocket</c> in <c>listen/2</c>.</p>
	<p>The default
          value for <c>Timeout</c> is <c>infinity</c>. If
          <c>Timeout</c> is specified, and no connection is accepted
          within the given time, <c>{error, timeout}</c> is
          returned.</p>
      </desc>
    </func>
    
    <func>
      <name>versions() ->
	[{SslAppVer, SupportedSslVer, AvailableSslVsn}]</name>
      <fsummary>Returns version information relevant for the
	ssl application.</fsummary>
      <type>
	<v>SslAppVer = string()</v>
      	<v>SupportedSslVer = [protocol()]</v>
      	<v>AvailableSslVsn = [protocol()]</v>
      </type>
      <desc>
	<p>
	  Returns version information relevant for the
	  ssl application.</p>
      </desc>
    </func>
  </funcs> 
      
  <section>
    <title>SEE ALSO</title>
    <p><seealso marker="kernel:inet">inet(3) </seealso> and 
      <seealso marker="kernel:gen_tcp">gen_tcp(3) </seealso>
    </p>
  </section>

</erlref>