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Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001\documentclass{howto}
2
3\title{Python OpenSSL Manual}
4
Jean-Paul Calderone71ff3682009-04-25 08:30:11 -04005\release{0.9}
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05006
Jean-Paul Calderone0ebe45a2009-04-25 10:40:31 -04007\author{Jean-Paul Calderone}
8\authoraddress{\email{exarkun@twistedmatrix.com}}
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05009
10\usepackage[english]{babel}
11\usepackage[T1]{fontenc}
12
13\begin{document}
14
15\maketitle
16
17\begin{abstract}
18\noindent
19This module is a rather thin wrapper around (a subset of) the OpenSSL library.
20With thin wrapper I mean that a lot of the object methods do nothing more than
21calling a corresponding function in the OpenSSL library.
22\end{abstract}
23
24\tableofcontents
25
26
27\section{Introduction \label{intro}}
28
Jean-Paul Calderone9450d5b2008-09-01 12:04:20 -040029The reason pyOpenSSL was created is that the SSL support in the socket module
30in Python 2.1 (the contemporary version of Python when the pyOpenSSL project
31was begun) was severely limited. Other OpenSSL wrappers for Python at the time
32were also limited, though in different ways. Unfortunately, Python's standard
33library SSL support has remained weak, although other packages (such as
34M2Crypto\footnote{See \url{http://chandlerproject.org/Projects/MeTooCrypto}})
35have made great advances and now equal or exceed pyOpenSSL's functionality.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -050036
Jean-Paul Calderone9450d5b2008-09-01 12:04:20 -040037The reason pyOpenSSL continues to be maintained is that there is a significant
38user community around it, as well as a large amount of software which depends
39on it. It is a great benefit to many people for pyOpenSSL to continue to exist
40and advance.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -050041
42\section{Building and Installing \label{building}}
43
44These instructions can also be found in the file \verb|INSTALL|.
45
46I have tested this on Debian Linux systems (woody and sid), Solaris 2.6 and
472.7. Others have successfully compiled it on Windows and NT.
48
49\subsection{Building the Module on a Unix System \label{building-unix}}
50
51pyOpenSSL uses distutils, so there really shouldn't be any problems. To build
52the library:
53\begin{verbatim}
54python setup.py build
55\end{verbatim}
56
57If your OpenSSL header files aren't in \verb|/usr/include|, you may need to
58supply the \verb|-I| flag to let the setup script know where to look. The same
59goes for the libraries of course, use the \verb|-L| flag. Note that
60\verb|build| won't accept these flags, so you have to run first
61\verb|build_ext| and then \verb|build|! Example:
62\begin{verbatim}
63python setup.py build_ext -I/usr/local/ssl/include -L/usr/local/ssl/lib
64python setup.py build
65\end{verbatim}
66
67Now you should have a directory called \verb|OpenSSL| that contains e.g.
68\verb|SSL.so| and \verb|__init__.py| somewhere in the build dicrectory,
69so just:
70\begin{verbatim}
71python setup.py install
72\end{verbatim}
73
74If you, for some arcane reason, don't want the module to appear in the
75\verb|site-packages| directory, use the \verb|--prefix| option.
76
77You can, of course, do
78\begin{verbatim}
79python setup.py --help
80\end{verbatim}
81
82to find out more about how to use the script.
83
84\subsection{Building the Module on a Windows System \label{building-windows}}
85
86Big thanks to Itamar Shtull-Trauring and Oleg Orlov for their help with
87Windows build instructions. Same as for Unix systems, we have to separate
88the \verb|build_ext| and the \verb|build|.
89
90Building the library:
91
92\begin{verbatim}
93setup.py build_ext -I ...\openssl\inc32 -L ...\openssl\out32dll
94setup.py build
95\end{verbatim}
96
97Where \verb|...\openssl| is of course the location of your OpenSSL installation.
98
99Installation is the same as for Unix systems:
100\begin{verbatim}
101setup.py install
102\end{verbatim}
103
104And similarily, you can do
105\begin{verbatim}
106setup.py --help
107\end{verbatim}
108
109to get more information.
110
111
112\section{\module{OpenSSL} --- Python interface to OpenSSL \label{openssl}}
113
114\declaremodule{extension}{OpenSSL}
115\modulesynopsis{Python interface to OpenSSL}
116
117This package provides a high-level interface to the functions in the
118OpenSSL library. The following modules are defined:
119
120\begin{datadesc}{crypto}
121Generic cryptographic module. Note that if anything is incomplete, this module is!
122\end{datadesc}
123
124\begin{datadesc}{rand}
125An interface to the OpenSSL pseudo random number generator.
126\end{datadesc}
127
128\begin{datadesc}{SSL}
129An interface to the SSL-specific parts of OpenSSL.
130\end{datadesc}
131
132
133% % % crypto moduleOpenSSL
134
135\subsection{\module{crypto} --- Generic cryptographic module \label{openssl-crypto}}
136
137\declaremodule{extension}{crypto}
138\modulesynopsis{Generic cryptographic module}
139
140\begin{datadesc}{X509Type}
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400141See \class{X509}.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500142\end{datadesc}
143
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400144\begin{classdesc}{X509}{}
145A class representing X.509 certificates.
146\end{classdesc}
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500147
148\begin{datadesc}{X509NameType}
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400149See \class{X509Name}.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500150\end{datadesc}
151
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400152\begin{classdesc}{X509Name}{x509name}
153A class representing X.509 Distinguished Names.
154
155This constructor creates a copy of \var{x509name} which should be an
156instance of \class{X509Name}.
157\end{classdesc}
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500158
159\begin{datadesc}{X509ReqType}
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400160See \class{X509Req}.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500161\end{datadesc}
162
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400163\begin{classdesc}{X509Req}{}
164A class representing X.509 certificate requests.
165\end{classdesc}
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500166
167\begin{datadesc}{X509StoreType}
168A Python type object representing the X509Store object type.
169\end{datadesc}
170
171\begin{datadesc}{PKeyType}
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400172See \class{PKey}.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500173\end{datadesc}
174
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400175\begin{classdesc}{PKey}{}
176A class representing DSA or RSA keys.
177\end{classdesc}
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500178
179\begin{datadesc}{PKCS7Type}
180A Python type object representing the PKCS7 object type.
181\end{datadesc}
182
183\begin{datadesc}{PKCS12Type}
184A Python type object representing the PKCS12 object type.
185\end{datadesc}
186
187\begin{datadesc}{X509ExtensionType}
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400188See \class{X509Extension}.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500189\end{datadesc}
190
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400191\begin{classdesc}{X509Extension}{typename, critical, value}
192A class representing an X.509 v3 certificate extensions.
193\end{classdesc}
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500194
195\begin{datadesc}{NetscapeSPKIType}
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400196See \class{NetscapeSPKI}.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500197\end{datadesc}
198
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400199\begin{classdesc}{NetscapeSPKI}{\optional{enc}}
200A class representing Netscape SPKI objects.
201
202If the \var{enc} argument is present, it should be a base64-encoded string
203representing a NetscapeSPKI object, as returned by the \method{b64_encode}
204method.
205\end{classdesc}
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500206
207\begin{datadesc}{FILETYPE_PEM}
208\dataline{FILETYPE_ASN1}
209File type constants.
210\end{datadesc}
211
212\begin{datadesc}{TYPE_RSA}
213\dataline{TYPE_DSA}
214Key type constants.
215\end{datadesc}
216
217\begin{excdesc}{Error}
218Generic exception used in the \module{crypto} module.
219\end{excdesc}
220
221\begin{funcdesc}{dump_certificate}{type, cert}
222Dump the certificate \var{cert} into a buffer string encoded with the type
223\var{type}.
224\end{funcdesc}
225
226\begin{funcdesc}{dump_certificate_request}{type, req}
227Dump the certificate request \var{req} into a buffer string encoded with the
228type \var{type}.
229\end{funcdesc}
230
231\begin{funcdesc}{dump_privatekey}{type, pkey\optional{, cipher, passphrase}}
232Dump the private key \var{pkey} into a buffer string encoded with the type
233\var{type}, optionally (if \var{type} is \constant{FILETYPE_PEM}) encrypting it
234using \var{cipher} and \var{passphrase}.
235
236\var{passphrase} must be either a string or a callback for providing the
237pass phrase.
238\end{funcdesc}
239
240\begin{funcdesc}{load_certificate}{type, buffer}
241Load a certificate (X509) from the string \var{buffer} encoded with the
242type \var{type}.
243\end{funcdesc}
244
245\begin{funcdesc}{load_certificate_request}{type, buffer}
246Load a certificate request (X509Req) from the string \var{buffer} encoded with
247the type \var{type}.
248\end{funcdesc}
249
250\begin{funcdesc}{load_privatekey}{type, buffer\optional{, passphrase}}
251Load a private key (PKey) from the string \var{buffer} encoded with
252the type \var{type} (must be one of \constant{FILETYPE_PEM} and
253\constant{FILETYPE_ASN1}).
254
255\var{passphrase} must be either a string or a callback for providing the
256pass phrase.
257\end{funcdesc}
258
259\begin{funcdesc}{load_pkcs7_data}{type, buffer}
260Load pkcs7 data from the string \var{buffer} encoded with the type \var{type}.
261\end{funcdesc}
262
263\begin{funcdesc}{load_pkcs12}{buffer\optional{, passphrase}}
264Load pkcs12 data from the string \var{buffer}. If the pkcs12 structure is
265encrypted, a \var{passphrase} must be included.
266\end{funcdesc}
267
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500268\subsubsection{X509 objects \label{openssl-x509}}
269
270X509 objects have the following methods:
271
272\begin{methoddesc}[X509]{get_issuer}{}
Jean-Paul Calderone2aa2b332008-03-06 21:43:14 -0500273Return an X509Name object representing the issuer of the certificate.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500274\end{methoddesc}
275
276\begin{methoddesc}[X509]{get_pubkey}{}
277Return a PKey object representing the public key of the certificate.
278\end{methoddesc}
279
280\begin{methoddesc}[X509]{get_serial_number}{}
281Return the certificate serial number.
282\end{methoddesc}
283
284\begin{methoddesc}[X509]{get_subject}{}
Jean-Paul Calderone2aa2b332008-03-06 21:43:14 -0500285Return an X509Name object representing the subject of the certificate.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500286\end{methoddesc}
287
288\begin{methoddesc}[X509]{get_version}{}
289Return the certificate version.
290\end{methoddesc}
291
Jean-Paul Calderone525ef802008-03-09 20:39:42 -0400292\begin{methoddesc}[X509]{get_notBefore}{}
293Return a string giving the time before which the certificate is not valid. The
294string is formatted as an ASN1 GENERALIZEDTIME:
295\begin{verbatim}
296 YYYYMMDDhhmmssZ
297 YYYYMMDDhhmmss+hhmm
298 YYYYMMDDhhmmss-hhmm
299\end{verbatim}
Jean-Paul Calderonee0615b52008-03-09 21:44:46 -0400300If no value exists for this field, \code{None} is returned.
Jean-Paul Calderone525ef802008-03-09 20:39:42 -0400301\end{methoddesc}
302
303\begin{methoddesc}[X509]{get_notAfter}{}
304Return a string giving the time after which the certificate is not valid. The
305string is formatted as an ASN1 GENERALIZEDTIME:
306\begin{verbatim}
307 YYYYMMDDhhmmssZ
308 YYYYMMDDhhmmss+hhmm
309 YYYYMMDDhhmmss-hhmm
310\end{verbatim}
Jean-Paul Calderonee0615b52008-03-09 21:44:46 -0400311If no value exists for this field, \code{None} is returned.
Jean-Paul Calderone525ef802008-03-09 20:39:42 -0400312\end{methoddesc}
313
314\begin{methoddesc}[X509]{set_notBefore}{when}
315Change the time before which the certificate is not valid. \var{when} is a
316string formatted as an ASN1 GENERALIZEDTIME:
317\begin{verbatim}
318 YYYYMMDDhhmmssZ
319 YYYYMMDDhhmmss+hhmm
320 YYYYMMDDhhmmss-hhmm
321\end{verbatim}
322\end{methoddesc}
323
324\begin{methoddesc}[X509]{set_notAfter}{when}
325Change the time after which the certificate is not valid. \var{when} is a
326string formatted as an ASN1 GENERALIZEDTIME:
327\begin{verbatim}
328 YYYYMMDDhhmmssZ
329 YYYYMMDDhhmmss+hhmm
330 YYYYMMDDhhmmss-hhmm
331\end{verbatim}
332\end{methoddesc}
333
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500334\begin{methoddesc}[X509]{gmtime_adj_notBefore}{time}
335Adjust the timestamp (in GMT) when the certificate starts being valid.
336\end{methoddesc}
337
338\begin{methoddesc}[X509]{gmtime_adj_notAfter}{time}
339Adjust the timestamp (in GMT) when the certificate stops being valid.
340\end{methoddesc}
341
342\begin{methoddesc}[X509]{has_expired}{}
343Checks the certificate's time stamp against current time. Returns true if the
344certificate has expired and false otherwise.
345\end{methoddesc}
346
347\begin{methoddesc}[X509]{set_issuer}{issuer}
348Set the issuer of the certificate to \var{issuer}.
349\end{methoddesc}
350
351\begin{methoddesc}[X509]{set_pubkey}{pkey}
352Set the public key of the certificate to \var{pkey}.
353\end{methoddesc}
354
355\begin{methoddesc}[X509]{set_serial_number}{serialno}
356Set the serial number of the certificate to \var{serialno}.
357\end{methoddesc}
358
359\begin{methoddesc}[X509]{set_subject}{subject}
360Set the subject of the certificate to \var{subject}.
361\end{methoddesc}
362
363\begin{methoddesc}[X509]{set_version}{version}
364Set the certificate version to \var{version}.
365\end{methoddesc}
366
367\begin{methoddesc}[X509]{sign}{pkey, digest}
368Sign the certificate, using the key \var{pkey} and the message digest algorithm
369identified by the string \var{digest}.
370\end{methoddesc}
371
372\begin{methoddesc}[X509]{subject_name_hash}{}
373Return the hash of the certificate subject.
374\end{methoddesc}
375
376\begin{methoddesc}[X509]{digest}{digest_name}
377Return a digest of the certificate, using the \var{digest_name} method.
Jean-Paul Calderoneb6f0d602008-12-28 21:20:01 -0500378\var{digest_name} must be a string describing a digest algorithm supported
379by OpenSSL (by EVP_get_digestbyname, specifically). For example,
380\constant{"md5"} or \constant{"sha1"}.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500381\end{methoddesc}
382
383\begin{methoddesc}[X509]{add_extensions}{extensions}
384Add the extensions in the sequence \var{extensions} to the certificate.
385\end{methoddesc}
386
387\subsubsection{X509Name objects \label{openssl-x509name}}
388
Jean-Paul Calderone2dd8ff52008-03-24 17:43:58 -0400389X509Name objects have the following methods:
390
391\begin{methoddesc}[X509Name]{hash}{}
392Return an integer giving the first four bytes of the MD5 digest of the DER
393representation of the name.
394\end{methoddesc}
395
Jean-Paul Calderonea6edbf82008-03-25 15:19:11 -0400396\begin{methoddesc}[X509Name]{der}{}
397Return a string giving the DER representation of the name.
398\end{methoddesc}
399
Jean-Paul Calderonec54cc182008-03-26 21:11:07 -0400400\begin{methoddesc}[X509Name]{get_components}{}
401Return a list of two-tuples of strings giving the components of the name.
402\end{methoddesc}
403
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500404X509Name objects have the following members:
405
406\begin{memberdesc}[X509Name]{countryName}
407The country of the entity. \code{C} may be used as an alias for
408\code{countryName}.
409\end{memberdesc}
410
411\begin{memberdesc}[X509Name]{stateOrProvinceName}
412The state or province of the entity. \code{ST} may be used as an alias for
413\code{stateOrProvinceName}·
414\end{memberdesc}
415
416\begin{memberdesc}[X509Name]{localityName}
417The locality of the entity. \code{L} may be used as an alias for
418\code{localityName}.
419\end{memberdesc}
420
421\begin{memberdesc}[X509Name]{organizationName}
422The organization name of the entity. \code{O} may be used as an alias for
423\code{organizationName}.
424\end{memberdesc}
425
426\begin{memberdesc}[X509Name]{organizationalUnitName}
427The organizational unit of the entity. \code{OU} may be used as an alias for
428\code{organizationalUnitName}.
429\end{memberdesc}
430
431\begin{memberdesc}[X509Name]{commonName}
432The common name of the entity. \code{CN} may be used as an alias for
433\code{commonName}.
434\end{memberdesc}
435
436\begin{memberdesc}[X509Name]{emailAddress}
437The e-mail address of the entity.
438\end{memberdesc}
439
440\subsubsection{X509Req objects \label{openssl-x509req}}
441
442X509Req objects have the following methods:
443
444\begin{methoddesc}[X509Req]{get_pubkey}{}
445Return a PKey object representing the public key of the certificate request.
446\end{methoddesc}
447
448\begin{methoddesc}[X509Req]{get_subject}{}
Jean-Paul Calderone2aa2b332008-03-06 21:43:14 -0500449Return an X509Name object representing the subject of the certificate.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500450\end{methoddesc}
451
452\begin{methoddesc}[X509Req]{set_pubkey}{pkey}
453Set the public key of the certificate request to \var{pkey}.
454\end{methoddesc}
455
456\begin{methoddesc}[X509Req]{sign}{pkey, digest}
457Sign the certificate request, using the key \var{pkey} and the message digest
458algorithm identified by the string \var{digest}.
459\end{methoddesc}
460
461\begin{methoddesc}[X509Req]{verify}{pkey}
462Verify a certificate request using the public key \var{pkey}.
463\end{methoddesc}
464
Jean-Paul Calderone8dd19b82008-12-28 20:41:16 -0500465\begin{methoddesc}[X509Req]{set_version}{version}
466Set the version (RFC 2459, 4.1.2.1) of the certificate request to
467\var{version}.
468\end{methoddesc}
469
470\begin{methoddesc}[X509Req]{get_version}{}
471Get the version (RFC 2459, 4.1.2.1) of the certificate request.
472\end{methoddesc}
473
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500474\subsubsection{X509Store objects \label{openssl-x509store}}
475
476The X509Store object has currently just one method:
477
478\begin{methoddesc}[X509Store]{add_cert}{cert}
479Add the certificate \var{cert} to the certificate store.
480\end{methoddesc}
481
482\subsubsection{PKey objects \label{openssl-pkey}}
483
484The PKey object has the following methods:
485
486\begin{methoddesc}[PKey]{bits}{}
487Return the number of bits of the key.
488\end{methoddesc}
489
490\begin{methoddesc}[PKey]{generate_key}{type, bits}
491Generate a public/private key pair of the type \var{type} (one of
492\constant{TYPE_RSA} and \constant{TYPE_DSA}) with the size \var{bits}.
493\end{methoddesc}
494
495\begin{methoddesc}[PKey]{type}{}
496Return the type of the key.
497\end{methoddesc}
498
499\subsubsection{PKCS7 objects \label{openssl-pkcs7}}
500
501PKCS7 objects have the following methods:
502
503\begin{methoddesc}[PKCS7]{type_is_signed}{}
504FIXME
505\end{methoddesc}
506
507\begin{methoddesc}[PKCS7]{type_is_enveloped}{}
508FIXME
509\end{methoddesc}
510
511\begin{methoddesc}[PKCS7]{type_is_signedAndEnveloped}{}
512FIXME
513\end{methoddesc}
514
515\begin{methoddesc}[PKCS7]{type_is_data}{}
516FIXME
517\end{methoddesc}
518
519\begin{methoddesc}[PKCS7]{get_type_name}{}
520Get the type name of the PKCS7.
521\end{methoddesc}
522
523\subsubsection{PKCS12 objects \label{openssl-pkcs12}}
524
525PKCS12 objects have the following methods:
526
527\begin{methoddesc}[PKCS12]{get_certificate}{}
528Return certificate portion of the PKCS12 structure.
529\end{methoddesc}
530
531\begin{methoddesc}[PKCS12]{get_privatekey}{}
532Return private key portion of the PKCS12 structure
533\end{methoddesc}
534
535\begin{methoddesc}[PKCS12]{get_ca_certificates}{}
536Return CA certificates within the PKCS12 object as a tuple. Returns
537None if no CA certificates are present.
538\end{methoddesc}
539
540\subsubsection{X509Extension objects \label{openssl-509ext}}
541
Jean-Paul Calderonef8c5fab2008-12-31 15:53:48 -0500542X509Extension objects have several methods:
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500543
544\begin{methoddesc}[X509Extension]{get_critical}{}
545Return the critical field of the extension object.
546\end{methoddesc}
547
Jean-Paul Calderonef8c5fab2008-12-31 15:53:48 -0500548\begin{methoddesc}[X509Extension]{get_short_name}{}
549Return the short type name of the extension object.
550\end{methoddesc}
551
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500552\subsubsection{NetscapeSPKI objects \label{openssl-netscape-spki}}
553
554NetscapeSPKI objects have the following methods:
555
556\begin{methoddesc}[NetscapeSPKI]{b64_encode}{}
557Return a base64-encoded string representation of the object.
558\end{methoddesc}
559
560\begin{methoddesc}[NetscapeSPKI]{get_pubkey}{}
561Return the public key of object.
562\end{methoddesc}
563
564\begin{methoddesc}[NetscapeSPKI]{set_pubkey}{key}
565Set the public key of the object to \var{key}.
566\end{methoddesc}
567
568\begin{methoddesc}[NetscapeSPKI]{sign}{key, digest_name}
Jean-Paul Calderoneb6f0d602008-12-28 21:20:01 -0500569Sign the NetscapeSPKI object using the given \var{key} and
570\var{digest_name}. \var{digest_name} must be a string describing a digest
571algorithm supported by OpenSSL (by EVP_get_digestbyname, specifically). For
572example, \constant{"md5"} or \constant{"sha1"}.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500573\end{methoddesc}
574
575\begin{methoddesc}[NetscapeSPKI]{verify}{key}
576Verify the NetscapeSPKI object using the given \var{key}.
577\end{methoddesc}
578
579
580% % % rand module
581
582\subsection{\module{rand} --- An interface to the OpenSSL pseudo random number generator \label{openssl-rand}}
583
584\declaremodule{extension}{rand}
585\modulesynopsis{An interface to the OpenSSL pseudo random number generator}
586
587This module handles the OpenSSL pseudo random number generator (PRNG) and
588declares the following:
589
590\begin{funcdesc}{add}{string, entropy}
591Mix bytes from \var{string} into the PRNG state. The \var{entropy} argument is
592(the lower bound of) an estimate of how much randomness is contained in
593\var{string}, measured in bytes. For more information, see e.g. \rfc{1750}.
594\end{funcdesc}
595
596\begin{funcdesc}{egd}{path\optional{, bytes}}
597Query the Entropy Gathering Daemon\footnote{See
598\url{http://www.lothar.com/tech/crypto/}} on socket \var{path} for \var{bytes}
599bytes of random data and and uses \function{add} to seed the PRNG. The default
600value of \var{bytes} is 255.
601\end{funcdesc}
602
603\begin{funcdesc}{load_file}{path\optional{, bytes}}
604Read \var{bytes} bytes (or all of it, if \var{bytes} is negative) of data from
605the file \var{path} to seed the PRNG. The default value of \var{bytes} is -1.
606\end{funcdesc}
607
608\begin{funcdesc}{screen}{}
609Add the current contents of the screen to the PRNG state.
610Availability: Windows.
611\end{funcdesc}
612
613\begin{funcdesc}{seed}{string}
614This is equivalent to calling \function{add} with \var{entropy} as the length
615of the string.
616\end{funcdesc}
617
618\begin{funcdesc}{status}{}
619Returns true if the PRNG has been seeded with enough data, and false otherwise.
620\end{funcdesc}
621
622\begin{funcdesc}{write_file}{path}
623Write a number of random bytes (currently 1024) to the file \var{path}. This
624file can then be used with \function{load_file} to seed the PRNG again.
625\end{funcdesc}
626
627
628
629% % % SSL module
630
631\subsection{\module{SSL} --- An interface to the SSL-specific parts of OpenSSL \label{openssl-ssl}}
632
633\declaremodule{extension}{SSL}
634\modulesynopsis{An interface to the SSL-specific parts of OpenSSL}
635
636This module handles things specific to SSL. There are two objects defined:
637Context, Connection.
638
639\begin{datadesc}{SSLv2_METHOD}
640\dataline{SSLv3_METHOD}
641\dataline{SSLv23_METHOD}
642\dataline{TLSv1_METHOD}
643These constants represent the different SSL methods to use when creating a
644context object.
645\end{datadesc}
646
647\begin{datadesc}{VERIFY_NONE}
648\dataline{VERIFY_PEER}
649\dataline{VERIFY_FAIL_IF_NO_PEER_CERT}
650These constants represent the verification mode used by the Context
651object's \method{set_verify} method.
652\end{datadesc}
653
654\begin{datadesc}{FILETYPE_PEM}
655\dataline{FILETYPE_ASN1}
656File type constants used with the \method{use_certificate_file} and
657\method{use_privatekey_file} methods of Context objects.
658\end{datadesc}
659
660\begin{datadesc}{OP_SINGLE_DH_USE}
661\dataline{OP_EPHEMERAL_RSA}
662\dataline{OP_NO_SSLv2}
663\dataline{OP_NO_SSLv3}
664\dataline{OP_NO_TLSv1}
665Constants used with \method{set_options} of Context objects.
666\constant{OP_SINGLE_DH_USE} means to always create a new key when using ephemeral
667Diffie-Hellman. \constant{OP_EPHEMERAL_RSA} means to always use ephemeral RSA keys
668when doing RSA operations. \constant{OP_NO_SSLv2}, \constant{OP_NO_SSLv3} and
669\constant{OP_NO_TLSv1} means to disable those specific protocols. This is
670interesting if you're using e.g. \constant{SSLv23_METHOD} to get an SSLv2-compatible
671handshake, but don't want to use SSLv2.
672\end{datadesc}
673
674\begin{datadesc}{ContextType}
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400675See \class{Context}.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500676\end{datadesc}
677
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400678\begin{classdesc}{Context}{method}
679A class representing SSL contexts. Contexts define the parameters of one or
680more SSL connections.
681
682\var{method} should be \constant{SSLv2_METHOD}, \constant{SSLv3_METHOD},
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500683\constant{SSLv23_METHOD} or \constant{TLSv1_METHOD}.
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400684\end{classdesc}
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500685
686\begin{datadesc}{ConnectionType}
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400687See \class{Connection}.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500688\end{datadesc}
689
Jean-Paul Calderonefc4abd02009-07-04 16:15:36 -0400690\begin{classdesc}{Connection}{context, socket}
691A class representing SSL connections.
692
693\var{context} should be an instance of \class{Context} and \var{socket}
694should be a socket \footnote{Actually, all that is required is an object
695that \emph{behaves} like a socket, you could even use files, even though
696it'd be tricky to get the handshakes right!} object. \var{socket} may be
697\var{None}; in this case, the Connection is created with a memory BIO: see
698the \method{bio_read}, \method{bio_write}, and \method{bio_shutdown}
699methods.
700\end{classdesc}
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500701
702\begin{excdesc}{Error}
703This exception is used as a base class for the other SSL-related
704exceptions, but may also be raised directly.
705
706Whenever this exception is raised directly, it has a list of error messages
707from the OpenSSL error queue, where each item is a tuple \code{(\var{lib},
708\var{function}, \var{reason})}. Here \var{lib}, \var{function} and \var{reason}
709are all strings, describing where and what the problem is. See \manpage{err}{3}
710for more information.
711\end{excdesc}
712
713\begin{excdesc}{ZeroReturnError}
714This exception matches the error return code \code{SSL_ERROR_ZERO_RETURN}, and
715is raised when the SSL Connection has been closed. In SSL 3.0 and TLS 1.0, this
716only occurs if a closure alert has occurred in the protocol, i.e. the
717connection has been closed cleanly. Note that this does not necessarily
718mean that the transport layer (e.g. a socket) has been closed.
719
720It may seem a little strange that this is an exception, but it does match an
721\code{SSL_ERROR} code, and is very convenient.
722\end{excdesc}
723
724\begin{excdesc}{WantReadError}
725The operation did not complete; the same I/O method should be called again
726later, with the same arguments. Any I/O method can lead to this since new
727handshakes can occur at any time.
Rick Dean71fa0962009-07-09 23:56:39 -0500728
729The wanted read is for "dirty" data sent over the network, not the
730"clean" data inside the tunnel. For a socket based SSL connection,
731"read" means data coming at us over the network. Until
732that read succeeds, the attempted
733\method{OpenSSL.SSL.Connection.recv},
734\method{OpenSSL.SSL.Connection.send}, or
735\method{OpenSSL.SSL.Connection.do_handshake} is prevented or incomplete.
736You probably want to \method{select()} on the socket before trying again.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500737\end{excdesc}
738
739\begin{excdesc}{WantWriteError}
Rick Dean71fa0962009-07-09 23:56:39 -0500740See \exception{WantReadError}. The socket may be too full to
741write more data.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500742\end{excdesc}
743
744\begin{excdesc}{WantX509LookupError}
745The operation did not complete because an application callback has asked to be
746called again. The I/O method should be called again later, with the same
747arguments. Note: This won't occur in this version, as there are no such
748callbacks in this version.
749\end{excdesc}
750
751\begin{excdesc}{SysCallError}
752The \exception{SysCallError} occurs when there's an I/O error and OpenSSL's
753error queue does not contain any information. This can mean two things: An
754error in the transport protocol, or an end of file that violates the protocol.
755The parameter to the exception is always a pair \code{(\var{errnum},
756\var{errstr})}.
757\end{excdesc}
758
759
760\subsubsection{Context objects \label{openssl-context}}
761
762Context objects have the following methods:
763
764\begin{methoddesc}[Context]{check_privatekey}{}
765Check if the private key (loaded with \method{use_privatekey\optional{_file}})
766matches the certificate (loaded with \method{use_certificate\optional{_file}}).
Jean-Paul Calderonef05fbbe2008-03-06 21:52:35 -0500767Returns \code{None} if they match, raises \exception{Error} otherwise.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500768\end{methoddesc}
769
770\begin{methoddesc}[Context]{get_app_data}{}
771Retrieve application data as set by \method{set_app_data}.
772\end{methoddesc}
773
774\begin{methoddesc}[Context]{get_cert_store}{}
775Retrieve the certificate store (a X509Store object) that the context uses.
776This can be used to add "trusted" certificates without using the.
777\method{load_verify_locations()} method.
778\end{methoddesc}
779
780\begin{methoddesc}[Context]{get_timeout}{}
781Retrieve session timeout, as set by \method{set_timeout}. The default is 300
782seconds.
783\end{methoddesc}
784
785\begin{methoddesc}[Context]{get_verify_depth}{}
786Retrieve the Context object's verify depth, as set by
787\method{set_verify_depth}.
788\end{methoddesc}
789
790\begin{methoddesc}[Context]{get_verify_mode}{}
Jean-Paul Calderoneae4238d2008-12-28 21:13:50 -0500791Retrieve the Context object's verify mode, as set by \method{set_verify}.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500792\end{methoddesc}
793
794\begin{methoddesc}[Context]{load_client_ca}{pemfile}
795Read a file with PEM-formatted certificates that will be sent to the client
796when requesting a client certificate.
797\end{methoddesc}
798
Jean-Paul Calderone5601c242008-09-07 21:06:52 -0400799\begin{methoddesc}[Context]{load_verify_locations}{pemfile, capath}
800Specify where CA certificates for verification purposes are located. These
801are trusted certificates. Note that the certificates have to be in PEM
802format. If capath is passed, it must be a directory prepared using the
803\code{c_rehash} tool included with OpenSSL. Either, but not both, of
804\var{pemfile} or \var{capath} may be \code{None}.
805\end{methoddesc}
806
807\begin{methoddesc}[Context]{set_default_verify_paths}{}
808Specify that the platform provided CA certificates are to be used for
Jean-Paul Calderone1d287e52009-03-07 09:09:07 -0500809verification purposes. This method may not work properly on OS X.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500810\end{methoddesc}
811
812\begin{methoddesc}[Context]{load_tmp_dh}{dhfile}
813Load parameters for Ephemeral Diffie-Hellman from \var{dhfile}.
814\end{methoddesc}
815
816\begin{methoddesc}[Context]{set_app_data}{data}
817Associate \var{data} with this Context object. \var{data} can be retrieved
818later using the \method{get_app_data} method.
819\end{methoddesc}
820
821\begin{methoddesc}[Context]{set_cipher_list}{ciphers}
822Set the list of ciphers to be used in this context. See the OpenSSL manual for
823more information (e.g. ciphers(1))
824\end{methoddesc}
825
826\begin{methoddesc}[Context]{set_info_callback}{callback}
827Set the information callback to \var{callback}. This function will be called
828from time to time during SSL handshakes.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500829\var{callback} should take three arguments: a Connection object and two
830integers. The first integer specifies where in the SSL handshake the function
831was called, and the other the return code from a (possibly failed) internal
832function call.
833\end{methoddesc}
834
835\begin{methoddesc}[Context]{set_options}{options}
836Add SSL options. Options you have set before are not cleared!
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500837This method should be used with the \constant{OP_*} constants.
838\end{methoddesc}
839
840\begin{methoddesc}[Context]{set_passwd_cb}{callback\optional{, userdata}}
841Set the passphrase callback to \var{callback}. This function will be called
Jean-Paul Calderone1eeb29e2008-10-19 11:50:53 -0400842when a private key with a passphrase is loaded. \var{callback} must accept
843three positional arguments. First, an integer giving the maximum length of
844the passphrase it may return. If the returned passphrase is longer than
845this, it will be truncated. Second, a boolean value which will be true if
846the user should be prompted for the passphrase twice and the callback should
847verify that the two values supplied are equal. Third, the value given as the
848\var{userdata} parameter to \method{set_passwd_cb}. If an error occurs,
849\var{callback} should return a false value (e.g. an empty string).
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500850\end{methoddesc}
851
852\begin{methoddesc}[Context]{set_session_id}{name}
853Set the context \var{name} within which a session can be reused for this
854Context object. This is needed when doing session resumption, because there is
855no way for a stored session to know which Context object it is associated with.
856\var{name} may be any binary data.
857\end{methoddesc}
858
859\begin{methoddesc}[Context]{set_timeout}{timeout}
860Set the timeout for newly created sessions for this Context object to
861\var{timeout}. \var{timeout} must be given in (whole) seconds. The default
862value is 300 seconds. See the OpenSSL manual for more information (e.g.
863SSL_CTX_set_timeout(3)).
864\end{methoddesc}
865
866\begin{methoddesc}[Context]{set_verify}{mode, callback}
867Set the verification flags for this Context object to \var{mode} and specify
868that \var{callback} should be used for verification callbacks. \var{mode}
869should be one of \constant{VERIFY_NONE} and \constant{VERIFY_PEER}. If
870\constant{VERIFY_PEER} is used, \var{mode} can be OR:ed with
871\constant{VERIFY_FAIL_IF_NO_PEER_CERT} and \constant{VERIFY_CLIENT_ONCE} to
872further control the behaviour.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500873\var{callback} should take five arguments: A Connection object, an X509 object,
874and three integer variables, which are in turn potential error number, error
875depth and return code. \var{callback} should return true if verification passes
876and false otherwise.
877\end{methoddesc}
878
879\begin{methoddesc}[Context]{set_verify_depth}{depth}
880Set the maximum depth for the certificate chain verification that shall be
881allowed for this Context object.
882\end{methoddesc}
883
884\begin{methoddesc}[Context]{use_certificate}{cert}
885Use the certificate \var{cert} which has to be a X509 object.
886\end{methoddesc}
887
Jean-Paul Calderone87b40602008-02-19 21:13:25 -0500888\begin{methoddesc}[Context]{add_extra_chain_cert}{cert}
889Adds the certificate \var{cert}, which has to be a X509 object, to the
890certificate chain presented together with the certificate.
891\end{methoddesc}
892
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500893\begin{methoddesc}[Context]{use_certificate_chain_file}{file}
894Load a certificate chain from \var{file} which must be PEM encoded.
895\end{methoddesc}
896
897\begin{methoddesc}[Context]{use_privatekey}{pkey}
898Use the private key \var{pkey} which has to be a PKey object.
899\end{methoddesc}
900
901\begin{methoddesc}[Context]{use_certificate_file}{file\optional{, format}}
902Load the first certificate found in \var{file}. The certificate must be in the
903format specified by \var{format}, which is either \constant{FILETYPE_PEM} or
904\constant{FILETYPE_ASN1}. The default is \constant{FILETYPE_PEM}.
905\end{methoddesc}
906
907\begin{methoddesc}[Context]{use_privatekey_file}{file\optional{, format}}
908Load the first private key found in \var{file}. The private key must be in the
909format specified by \var{format}, which is either \constant{FILETYPE_PEM} or
910\constant{FILETYPE_ASN1}. The default is \constant{FILETYPE_PEM}.
911\end{methoddesc}
912
913
914\subsubsection{Connection objects \label{openssl-connection}}
915
916Connection objects have the following methods:
917
918\begin{methoddesc}[Connection]{accept}{}
919Call the \method{accept} method of the underlying socket and set up SSL on the
920returned socket, using the Context object supplied to this Connection object at
921creation. Returns a pair \code{(\var{conn}, \var{address})}. where \var{conn}
922is the new Connection object created, and \var{address} is as returned by the
923socket's \method{accept}.
924\end{methoddesc}
925
926\begin{methoddesc}[Connection]{bind}{address}
927Call the \method{bind} method of the underlying socket.
928\end{methoddesc}
929
930\begin{methoddesc}[Connection]{close}{}
931Call the \method{close} method of the underlying socket. Note: If you want
932correct SSL closure, you need to call the \method{shutdown} method first.
933\end{methoddesc}
934
935\begin{methoddesc}[Connection]{connect}{address}
936Call the \method{connect} method of the underlying socket and set up SSL on the
937socket, using the Context object supplied to this Connection object at
938creation.
939\end{methoddesc}
940
941\begin{methoddesc}[Connection]{connect_ex}{address}
942Call the \method{connect_ex} method of the underlying socket and set up SSL on
943the socket, using the Context object supplied to this Connection object at
944creation. Note that if the \method{connect_ex} method of the socket doesn't
945return 0, SSL won't be initialized.
946\end{methoddesc}
947
948\begin{methoddesc}[Connection]{do_handshake}{}
949Perform an SSL handshake (usually called after \method{renegotiate} or one of
950\method{set_accept_state} or \method{set_accept_state}). This can raise the
951same exceptions as \method{send} and \method{recv}.
952\end{methoddesc}
953
954\begin{methoddesc}[Connection]{fileno}{}
955Retrieve the file descriptor number for the underlying socket.
956\end{methoddesc}
957
958\begin{methoddesc}[Connection]{listen}{backlog}
959Call the \method{listen} method of the underlying socket.
960\end{methoddesc}
961
962\begin{methoddesc}[Connection]{get_app_data}{}
963Retrieve application data as set by \method{set_app_data}.
964\end{methoddesc}
965
966\begin{methoddesc}[Connection]{get_cipher_list}{}
967Retrieve the list of ciphers used by the Connection object. WARNING: This API
968has changed. It used to take an optional parameter and just return a string,
969but not it returns the entire list in one go.
970\end{methoddesc}
971
972\begin{methoddesc}[Connection]{get_context}{}
973Retrieve the Context object associated with this Connection.
974\end{methoddesc}
975
976\begin{methoddesc}[Connection]{get_peer_certificate}{}
977Retrieve the other side's certificate (if any)
978\end{methoddesc}
979
980\begin{methoddesc}[Connection]{getpeername}{}
981Call the \method{getpeername} method of the underlying socket.
982\end{methoddesc}
983
984\begin{methoddesc}[Connection]{getsockname}{}
985Call the \method{getsockname} method of the underlying socket.
986\end{methoddesc}
987
988\begin{methoddesc}[Connection]{getsockopt}{level, optname\optional{, buflen}}
989Call the \method{getsockopt} method of the underlying socket.
990\end{methoddesc}
991
992\begin{methoddesc}[Connection]{pending}{}
Jean-Paul Calderoneb6f57be2008-03-06 21:22:16 -0500993Retrieve the number of bytes that can be safely read from the SSL buffer
994(\emph{not} the underlying transport buffer).
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500995\end{methoddesc}
996
997\begin{methoddesc}[Connection]{recv}{bufsize}
998Receive data from the Connection. The return value is a string representing the
999data received. The maximum amount of data to be received at once, is specified
1000by \var{bufsize}.
1001\end{methoddesc}
1002
Jean-Paul Calderoneb6b17122009-05-01 16:36:11 -04001003\begin{methoddesc}[Connection]{bio_write}{bytes}
1004If the Connection was created with a memory BIO, this method can be used to add
1005bytes to the read end of that memory BIO. The Connection can then read the
1006bytes (for example, in response to a call to \method{recv}).
1007\end{methoddesc}
1008
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001009\begin{methoddesc}[Connection]{renegotiate}{}
1010Renegotiate the SSL session. Call this if you wish to change cipher suites or
1011anything like that.
1012\end{methoddesc}
1013
1014\begin{methoddesc}[Connection]{send}{string}
1015Send the \var{string} data to the Connection.
1016\end{methoddesc}
1017
Jean-Paul Calderoneb6b17122009-05-01 16:36:11 -04001018\begin{methoddesc}[Connection]{bio_read}{bufsize}
1019If the Connection was created with a memory BIO, this method can be used to
1020read bytes from the write end of that memory BIO. Many Connection methods will
1021add bytes which must be read in this manner or the buffer will eventually fill
1022up and the Connection will be able to take no further actions.
1023\end{methoddesc}
1024
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001025\begin{methoddesc}[Connection]{sendall}{string}
1026Send all of the \var{string} data to the Connection. This calls \method{send}
1027repeatedly until all data is sent. If an error occurs, it's impossible to tell
1028how much data has been sent.
1029\end{methoddesc}
1030
1031\begin{methoddesc}[Connection]{set_accept_state}{}
1032Set the connection to work in server mode. The handshake will be handled
1033automatically by read/write.
1034\end{methoddesc}
1035
1036\begin{methoddesc}[Connection]{set_app_data}{data}
1037Associate \var{data} with this Connection object. \var{data} can be retrieved
1038later using the \method{get_app_data} method.
1039\end{methoddesc}
1040
1041\begin{methoddesc}[Connection]{set_connect_state}{}
1042Set the connection to work in client mode. The handshake will be handled
1043automatically by read/write.
1044\end{methoddesc}
1045
1046\begin{methoddesc}[Connection]{setblocking}{flag}
1047Call the \method{setblocking} method of the underlying socket.
1048\end{methoddesc}
1049
1050\begin{methoddesc}[Connection]{setsockopt}{level, optname, value}
1051Call the \method{setsockopt} method of the underlying socket.
1052\end{methoddesc}
1053
1054\begin{methoddesc}[Connection]{shutdown}{}
1055Send the shutdown message to the Connection. Returns true if the shutdown
1056message exchange is completed and false otherwise (in which case you call
1057\method{recv()} or \method{send()} when the connection becomes
1058readable/writeable.
1059\end{methoddesc}
1060
Jean-Paul Calderone72b8f0f2008-02-21 23:57:40 -05001061\begin{methoddesc}[Connection]{get_shutdown}{}
1062Get the shutdown state of the Connection. Returns a bitvector of either or
1063both of \var{SENT_SHUTDOWN} and \var{RECEIVED_SHUTDOWN}.
1064\end{methoddesc}
1065
1066\begin{methoddesc}[Connection]{set_shutdown}{state}
1067Set the shutdown state of the Connection. \var{state} is a bitvector of
1068either or both of \var{SENT_SHUTDOWN} and \var{RECEIVED_SHUTDOWN}.
1069\end{methoddesc}
1070
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001071\begin{methoddesc}[Connection]{sock_shutdown}{how}
1072Call the \method{shutdown} method of the underlying socket.
1073\end{methoddesc}
1074
Jean-Paul Calderoneb6b17122009-05-01 16:36:11 -04001075\begin{methoddesc}[Connection]{bio_shutdown}{}
1076If the Connection was created with a memory BIO, this method can be used to
1077indicate that ``end of file'' has been reached on the read end of that memory
1078BIO.
1079\end{methoddesc}
1080
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001081\begin{methoddesc}[Connection]{state_string}{}
1082Retrieve a verbose string detailing the state of the Connection.
1083\end{methoddesc}
1084
Jean-Paul Calderonefd236f32009-05-03 19:45:07 -04001085\begin{methoddesc}[Connection]{client_random}{}
1086Retrieve the random value used with the client hello message.
1087\end{methoddesc}
1088
1089\begin{methoddesc}[Connection]{server_random}{}
1090Retrieve the random value used with the server hello message.
1091\end{methoddesc}
1092
1093\begin{methoddesc}[Connection]{master_key}{}
1094Retrieve the value of the master key for this session.
1095\end{methoddesc}
1096
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001097\begin{methoddesc}[Connection]{want_read}{}
1098Checks if more data has to be read from the transport layer to complete an
1099operation.
1100\end{methoddesc}
1101
1102\begin{methoddesc}[Connection]{want_write}{}
1103Checks if there is data to write to the transport layer to complete an
1104operation.
1105\end{methoddesc}
1106
1107
1108
1109\section{Internals \label{internals}}
1110
1111We ran into three main problems developing this: Exceptions, callbacks and
1112accessing socket methods. This is what this chapter is about.
1113
1114\subsection{Exceptions \label{exceptions}}
1115
1116We realized early that most of the exceptions would be raised by the I/O
1117functions of OpenSSL, so it felt natural to mimic OpenSSL's error code system,
1118translating them into Python exceptions. This naturally gives us the exceptions
1119\exception{SSL.ZeroReturnError}, \exception{SSL.WantReadError},
1120\exception{SSL.WantWriteError}, \exception{SSL.WantX509LookupError} and
1121\exception{SSL.SysCallError}.
1122
1123For more information about this, see section \ref{openssl-ssl}.
1124
1125
1126\subsection{Callbacks \label{callbacks}}
1127
1128There are a number of problems with callbacks. First of all, OpenSSL is written
1129as a C library, it's not meant to have Python callbacks, so a way around that
1130is needed. Another problem is thread support. A lot of the OpenSSL I/O
1131functions can block if the socket is in blocking mode, and then you want other
1132Python threads to be able to do other things. The real trouble is if you've
Jean-Paul Calderoneb7d6db22008-09-21 18:57:56 -04001133released the global CPython interpreter lock to do a potentially blocking
1134operation, and the operation calls a callback. Then we must take the GIL back,
1135since calling Python APIs without holding it is not allowed.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001136
1137There are two solutions to the first problem, both of which are necessary. The
1138first solution to use is if the C callback allows ''userdata'' to be passed to
1139it (an arbitrary pointer normally). This is great! We can set our Python
1140function object as the real userdata and emulate userdata for the Python
1141function in another way. The other solution can be used if an object with an
1142''app_data'' system always is passed to the callback. For example, the SSL
1143object in OpenSSL has app_data functions and in e.g. the verification
1144callbacks, you can retrieve the related SSL object. What we do is to set our
1145wrapper \class{Connection} object as app_data for the SSL object, and we can
1146easily find the Python callback.
1147
Jean-Paul Calderoneb7d6db22008-09-21 18:57:56 -04001148The other problem is solved using thread local variables. Whenever the GIL is
1149released before calling into an OpenSSL API, the PyThreadState pointer returned
1150by \cfunction{PyEval_SaveState} is stored in a global thread local variable
1151(using Python's own TLS API, \cfunction{PyThread_set_key_value}). When it is
1152necessary to re-acquire the GIL, either after the OpenSSL API returns or in a C
1153callback invoked by that OpenSSL API, the value of the thread local variable is
1154retrieved (\cfunction{PyThread_get_key_value}) and used to re-acquire the GIL.
1155This allows Python threads to execute while OpenSSL APIs are running and allows
1156use of any particular pyOpenSSL object from any Python thread, since there is
1157no per-thread state associated with any of these objects and since OpenSSL is
1158threadsafe (as long as properly initialized, as pyOpenSSL initializes it).
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001159
1160
1161\subsection{Acessing Socket Methods \label{socket-methods}}
1162
1163We quickly saw the benefit of wrapping socket methods in the
1164\class{SSL.Connection} class, for an easy transition into using SSL. The
1165problem here is that the \module{socket} module lacks a C API, and all the
1166methods are declared static. One approach would be to have \module{OpenSSL} as
1167a submodule to the \module{socket} module, placing all the code in
1168\file{socketmodule.c}, but this is obviously not a good solution, since you
1169might not want to import tonnes of extra stuff you're not going to use when
1170importing the \module{socket} module. The other approach is to somehow get a
1171pointer to the method to be called, either the C function, or a callable Python
1172object. This is not really a good solution either, since there's a lot of
1173lookups involved.
1174
1175The way it works is that you have to supply a ``\class{socket}-like'' transport
1176object to the \class{SSL.Connection}. The only requirement of this object is
1177that it has a \method{fileno()} method that returns a file descriptor that's
1178valid at the C level (i.e. you can use the system calls read and write). If you
1179want to use the \method{connect()} or \method{accept()} methods of the
1180\class{SSL.Connection} object, the transport object has to supply such
1181methods too. Apart from them, any method lookups in the \class{SSL.Connection}
1182object that fail are passed on to the underlying transport object.
1183
1184Future changes might be to allow Python-level transport objects, that instead
1185of having \method{fileno()} methods, have \method{read()} and \method{write()}
1186methods, so more advanced features of Python can be used. This would probably
1187entail some sort of OpenSSL ``BIOs'', but converting Python strings back and
1188forth is expensive, so this shouldn't be used unless necessary. Other nice
1189things would be to be able to pass in different transport objects for reading
1190and writing, but then the \method{fileno()} method of \class{SSL.Connection}
1191becomes virtually useless. Also, should the method resolution be used on the
1192read-transport or the write-transport?
1193
1194
1195\end{document}