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Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001\documentclass{howto}
2
3\title{Python OpenSSL Manual}
4
Jean-Paul Calderonef7f0fb42008-10-19 11:55:13 -04005\release{0.8}
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05006
7\author{Martin Sjögren}
8\authoraddress{\email{martin@strakt.com}}
9
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}
141A Python type object representing the X509 object type.
142\end{datadesc}
143
144\begin{funcdesc}{X509}{}
145Factory function that creates an X509 object.
146\end{funcdesc}
147
148\begin{datadesc}{X509NameType}
149A Python type object representing the X509Name object type.
150\end{datadesc}
151
152\begin{funcdesc}{X509Name}{x509name}
153Factory function that creates a copy of \var{x509name}.
154\end{funcdesc}
155
156\begin{datadesc}{X509ReqType}
157A Python type object representing the X509Req object type.
158\end{datadesc}
159
160\begin{funcdesc}{X509Req}{}
161Factory function that creates an X509Req object.
162\end{funcdesc}
163
164\begin{datadesc}{X509StoreType}
165A Python type object representing the X509Store object type.
166\end{datadesc}
167
168\begin{datadesc}{PKeyType}
169A Python type object representing the PKey object type.
170\end{datadesc}
171
172\begin{funcdesc}{PKey}{}
173Factory function that creates a PKey object.
174\end{funcdesc}
175
176\begin{datadesc}{PKCS7Type}
177A Python type object representing the PKCS7 object type.
178\end{datadesc}
179
180\begin{datadesc}{PKCS12Type}
181A Python type object representing the PKCS12 object type.
182\end{datadesc}
183
184\begin{datadesc}{X509ExtensionType}
185A Python type object representing the X509Extension object type.
186\end{datadesc}
187
188\begin{funcdesc}{X509Extension}{typename, critical, value}
189Factory function that creates a X509Extension object.
190\end{funcdesc}
191
192\begin{datadesc}{NetscapeSPKIType}
193A Python type object representing the NetscapeSPKI object type.
194\end{datadesc}
195
196\begin{funcdesc}{NetscapeSPKI}{\optional{enc}}
197Factory function that creates a NetscapeSPKI object. If the \var{enc} argument
198is present, it should be a base64-encoded string representing a NetscapeSPKI
199object, as returned by the \method{b64_encode} method.
200\end{funcdesc}
201
202\begin{datadesc}{FILETYPE_PEM}
203\dataline{FILETYPE_ASN1}
204File type constants.
205\end{datadesc}
206
207\begin{datadesc}{TYPE_RSA}
208\dataline{TYPE_DSA}
209Key type constants.
210\end{datadesc}
211
212\begin{excdesc}{Error}
213Generic exception used in the \module{crypto} module.
214\end{excdesc}
215
216\begin{funcdesc}{dump_certificate}{type, cert}
217Dump the certificate \var{cert} into a buffer string encoded with the type
218\var{type}.
219\end{funcdesc}
220
221\begin{funcdesc}{dump_certificate_request}{type, req}
222Dump the certificate request \var{req} into a buffer string encoded with the
223type \var{type}.
224\end{funcdesc}
225
226\begin{funcdesc}{dump_privatekey}{type, pkey\optional{, cipher, passphrase}}
227Dump the private key \var{pkey} into a buffer string encoded with the type
228\var{type}, optionally (if \var{type} is \constant{FILETYPE_PEM}) encrypting it
229using \var{cipher} and \var{passphrase}.
230
231\var{passphrase} must be either a string or a callback for providing the
232pass phrase.
233\end{funcdesc}
234
235\begin{funcdesc}{load_certificate}{type, buffer}
236Load a certificate (X509) from the string \var{buffer} encoded with the
237type \var{type}.
238\end{funcdesc}
239
240\begin{funcdesc}{load_certificate_request}{type, buffer}
241Load a certificate request (X509Req) from the string \var{buffer} encoded with
242the type \var{type}.
243\end{funcdesc}
244
245\begin{funcdesc}{load_privatekey}{type, buffer\optional{, passphrase}}
246Load a private key (PKey) from the string \var{buffer} encoded with
247the type \var{type} (must be one of \constant{FILETYPE_PEM} and
248\constant{FILETYPE_ASN1}).
249
250\var{passphrase} must be either a string or a callback for providing the
251pass phrase.
252\end{funcdesc}
253
254\begin{funcdesc}{load_pkcs7_data}{type, buffer}
255Load pkcs7 data from the string \var{buffer} encoded with the type \var{type}.
256\end{funcdesc}
257
258\begin{funcdesc}{load_pkcs12}{buffer\optional{, passphrase}}
259Load pkcs12 data from the string \var{buffer}. If the pkcs12 structure is
260encrypted, a \var{passphrase} must be included.
261\end{funcdesc}
262
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500263\subsubsection{X509 objects \label{openssl-x509}}
264
265X509 objects have the following methods:
266
267\begin{methoddesc}[X509]{get_issuer}{}
Jean-Paul Calderone2aa2b332008-03-06 21:43:14 -0500268Return an X509Name object representing the issuer of the certificate.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500269\end{methoddesc}
270
271\begin{methoddesc}[X509]{get_pubkey}{}
272Return a PKey object representing the public key of the certificate.
273\end{methoddesc}
274
275\begin{methoddesc}[X509]{get_serial_number}{}
276Return the certificate serial number.
277\end{methoddesc}
278
279\begin{methoddesc}[X509]{get_subject}{}
Jean-Paul Calderone2aa2b332008-03-06 21:43:14 -0500280Return an X509Name object representing the subject of the certificate.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500281\end{methoddesc}
282
283\begin{methoddesc}[X509]{get_version}{}
284Return the certificate version.
285\end{methoddesc}
286
Jean-Paul Calderone525ef802008-03-09 20:39:42 -0400287\begin{methoddesc}[X509]{get_notBefore}{}
288Return a string giving the time before which the certificate is not valid. The
289string is formatted as an ASN1 GENERALIZEDTIME:
290\begin{verbatim}
291 YYYYMMDDhhmmssZ
292 YYYYMMDDhhmmss+hhmm
293 YYYYMMDDhhmmss-hhmm
294\end{verbatim}
Jean-Paul Calderonee0615b52008-03-09 21:44:46 -0400295If no value exists for this field, \code{None} is returned.
Jean-Paul Calderone525ef802008-03-09 20:39:42 -0400296\end{methoddesc}
297
298\begin{methoddesc}[X509]{get_notAfter}{}
299Return a string giving the time after which the certificate is not valid. The
300string is formatted as an ASN1 GENERALIZEDTIME:
301\begin{verbatim}
302 YYYYMMDDhhmmssZ
303 YYYYMMDDhhmmss+hhmm
304 YYYYMMDDhhmmss-hhmm
305\end{verbatim}
Jean-Paul Calderonee0615b52008-03-09 21:44:46 -0400306If no value exists for this field, \code{None} is returned.
Jean-Paul Calderone525ef802008-03-09 20:39:42 -0400307\end{methoddesc}
308
309\begin{methoddesc}[X509]{set_notBefore}{when}
310Change the time before which the certificate is not valid. \var{when} is a
311string formatted as an ASN1 GENERALIZEDTIME:
312\begin{verbatim}
313 YYYYMMDDhhmmssZ
314 YYYYMMDDhhmmss+hhmm
315 YYYYMMDDhhmmss-hhmm
316\end{verbatim}
317\end{methoddesc}
318
319\begin{methoddesc}[X509]{set_notAfter}{when}
320Change the time after which the certificate is not valid. \var{when} is a
321string formatted as an ASN1 GENERALIZEDTIME:
322\begin{verbatim}
323 YYYYMMDDhhmmssZ
324 YYYYMMDDhhmmss+hhmm
325 YYYYMMDDhhmmss-hhmm
326\end{verbatim}
327\end{methoddesc}
328
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500329\begin{methoddesc}[X509]{gmtime_adj_notBefore}{time}
330Adjust the timestamp (in GMT) when the certificate starts being valid.
331\end{methoddesc}
332
333\begin{methoddesc}[X509]{gmtime_adj_notAfter}{time}
334Adjust the timestamp (in GMT) when the certificate stops being valid.
335\end{methoddesc}
336
337\begin{methoddesc}[X509]{has_expired}{}
338Checks the certificate's time stamp against current time. Returns true if the
339certificate has expired and false otherwise.
340\end{methoddesc}
341
342\begin{methoddesc}[X509]{set_issuer}{issuer}
343Set the issuer of the certificate to \var{issuer}.
344\end{methoddesc}
345
346\begin{methoddesc}[X509]{set_pubkey}{pkey}
347Set the public key of the certificate to \var{pkey}.
348\end{methoddesc}
349
350\begin{methoddesc}[X509]{set_serial_number}{serialno}
351Set the serial number of the certificate to \var{serialno}.
352\end{methoddesc}
353
354\begin{methoddesc}[X509]{set_subject}{subject}
355Set the subject of the certificate to \var{subject}.
356\end{methoddesc}
357
358\begin{methoddesc}[X509]{set_version}{version}
359Set the certificate version to \var{version}.
360\end{methoddesc}
361
362\begin{methoddesc}[X509]{sign}{pkey, digest}
363Sign the certificate, using the key \var{pkey} and the message digest algorithm
364identified by the string \var{digest}.
365\end{methoddesc}
366
367\begin{methoddesc}[X509]{subject_name_hash}{}
368Return the hash of the certificate subject.
369\end{methoddesc}
370
371\begin{methoddesc}[X509]{digest}{digest_name}
372Return a digest of the certificate, using the \var{digest_name} method.
373\end{methoddesc}
374
375\begin{methoddesc}[X509]{add_extensions}{extensions}
376Add the extensions in the sequence \var{extensions} to the certificate.
377\end{methoddesc}
378
379\subsubsection{X509Name objects \label{openssl-x509name}}
380
Jean-Paul Calderone2dd8ff52008-03-24 17:43:58 -0400381X509Name objects have the following methods:
382
383\begin{methoddesc}[X509Name]{hash}{}
384Return an integer giving the first four bytes of the MD5 digest of the DER
385representation of the name.
386\end{methoddesc}
387
Jean-Paul Calderonea6edbf82008-03-25 15:19:11 -0400388\begin{methoddesc}[X509Name]{der}{}
389Return a string giving the DER representation of the name.
390\end{methoddesc}
391
Jean-Paul Calderonec54cc182008-03-26 21:11:07 -0400392\begin{methoddesc}[X509Name]{get_components}{}
393Return a list of two-tuples of strings giving the components of the name.
394\end{methoddesc}
395
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500396X509Name objects have the following members:
397
398\begin{memberdesc}[X509Name]{countryName}
399The country of the entity. \code{C} may be used as an alias for
400\code{countryName}.
401\end{memberdesc}
402
403\begin{memberdesc}[X509Name]{stateOrProvinceName}
404The state or province of the entity. \code{ST} may be used as an alias for
405\code{stateOrProvinceName}·
406\end{memberdesc}
407
408\begin{memberdesc}[X509Name]{localityName}
409The locality of the entity. \code{L} may be used as an alias for
410\code{localityName}.
411\end{memberdesc}
412
413\begin{memberdesc}[X509Name]{organizationName}
414The organization name of the entity. \code{O} may be used as an alias for
415\code{organizationName}.
416\end{memberdesc}
417
418\begin{memberdesc}[X509Name]{organizationalUnitName}
419The organizational unit of the entity. \code{OU} may be used as an alias for
420\code{organizationalUnitName}.
421\end{memberdesc}
422
423\begin{memberdesc}[X509Name]{commonName}
424The common name of the entity. \code{CN} may be used as an alias for
425\code{commonName}.
426\end{memberdesc}
427
428\begin{memberdesc}[X509Name]{emailAddress}
429The e-mail address of the entity.
430\end{memberdesc}
431
432\subsubsection{X509Req objects \label{openssl-x509req}}
433
434X509Req objects have the following methods:
435
436\begin{methoddesc}[X509Req]{get_pubkey}{}
437Return a PKey object representing the public key of the certificate request.
438\end{methoddesc}
439
440\begin{methoddesc}[X509Req]{get_subject}{}
Jean-Paul Calderone2aa2b332008-03-06 21:43:14 -0500441Return an X509Name object representing the subject of the certificate.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500442\end{methoddesc}
443
444\begin{methoddesc}[X509Req]{set_pubkey}{pkey}
445Set the public key of the certificate request to \var{pkey}.
446\end{methoddesc}
447
448\begin{methoddesc}[X509Req]{sign}{pkey, digest}
449Sign the certificate request, using the key \var{pkey} and the message digest
450algorithm identified by the string \var{digest}.
451\end{methoddesc}
452
453\begin{methoddesc}[X509Req]{verify}{pkey}
454Verify a certificate request using the public key \var{pkey}.
455\end{methoddesc}
456
Jean-Paul Calderone8dd19b82008-12-28 20:41:16 -0500457\begin{methoddesc}[X509Req]{set_version}{version}
458Set the version (RFC 2459, 4.1.2.1) of the certificate request to
459\var{version}.
460\end{methoddesc}
461
462\begin{methoddesc}[X509Req]{get_version}{}
463Get the version (RFC 2459, 4.1.2.1) of the certificate request.
464\end{methoddesc}
465
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500466\subsubsection{X509Store objects \label{openssl-x509store}}
467
468The X509Store object has currently just one method:
469
470\begin{methoddesc}[X509Store]{add_cert}{cert}
471Add the certificate \var{cert} to the certificate store.
472\end{methoddesc}
473
474\subsubsection{PKey objects \label{openssl-pkey}}
475
476The PKey object has the following methods:
477
478\begin{methoddesc}[PKey]{bits}{}
479Return the number of bits of the key.
480\end{methoddesc}
481
482\begin{methoddesc}[PKey]{generate_key}{type, bits}
483Generate a public/private key pair of the type \var{type} (one of
484\constant{TYPE_RSA} and \constant{TYPE_DSA}) with the size \var{bits}.
485\end{methoddesc}
486
487\begin{methoddesc}[PKey]{type}{}
488Return the type of the key.
489\end{methoddesc}
490
491\subsubsection{PKCS7 objects \label{openssl-pkcs7}}
492
493PKCS7 objects have the following methods:
494
495\begin{methoddesc}[PKCS7]{type_is_signed}{}
496FIXME
497\end{methoddesc}
498
499\begin{methoddesc}[PKCS7]{type_is_enveloped}{}
500FIXME
501\end{methoddesc}
502
503\begin{methoddesc}[PKCS7]{type_is_signedAndEnveloped}{}
504FIXME
505\end{methoddesc}
506
507\begin{methoddesc}[PKCS7]{type_is_data}{}
508FIXME
509\end{methoddesc}
510
511\begin{methoddesc}[PKCS7]{get_type_name}{}
512Get the type name of the PKCS7.
513\end{methoddesc}
514
515\subsubsection{PKCS12 objects \label{openssl-pkcs12}}
516
517PKCS12 objects have the following methods:
518
519\begin{methoddesc}[PKCS12]{get_certificate}{}
520Return certificate portion of the PKCS12 structure.
521\end{methoddesc}
522
523\begin{methoddesc}[PKCS12]{get_privatekey}{}
524Return private key portion of the PKCS12 structure
525\end{methoddesc}
526
527\begin{methoddesc}[PKCS12]{get_ca_certificates}{}
528Return CA certificates within the PKCS12 object as a tuple. Returns
529None if no CA certificates are present.
530\end{methoddesc}
531
532\subsubsection{X509Extension objects \label{openssl-509ext}}
533
534X509Extension objects currently only have one method:
535
536\begin{methoddesc}[X509Extension]{get_critical}{}
537Return the critical field of the extension object.
538\end{methoddesc}
539
540\subsubsection{NetscapeSPKI objects \label{openssl-netscape-spki}}
541
542NetscapeSPKI objects have the following methods:
543
544\begin{methoddesc}[NetscapeSPKI]{b64_encode}{}
545Return a base64-encoded string representation of the object.
546\end{methoddesc}
547
548\begin{methoddesc}[NetscapeSPKI]{get_pubkey}{}
549Return the public key of object.
550\end{methoddesc}
551
552\begin{methoddesc}[NetscapeSPKI]{set_pubkey}{key}
553Set the public key of the object to \var{key}.
554\end{methoddesc}
555
556\begin{methoddesc}[NetscapeSPKI]{sign}{key, digest_name}
557Sign the NetscapeSPKI object using the given \var{key} and \var{digest_name}.
558\end{methoddesc}
559
560\begin{methoddesc}[NetscapeSPKI]{verify}{key}
561Verify the NetscapeSPKI object using the given \var{key}.
562\end{methoddesc}
563
564
565% % % rand module
566
567\subsection{\module{rand} --- An interface to the OpenSSL pseudo random number generator \label{openssl-rand}}
568
569\declaremodule{extension}{rand}
570\modulesynopsis{An interface to the OpenSSL pseudo random number generator}
571
572This module handles the OpenSSL pseudo random number generator (PRNG) and
573declares the following:
574
575\begin{funcdesc}{add}{string, entropy}
576Mix bytes from \var{string} into the PRNG state. The \var{entropy} argument is
577(the lower bound of) an estimate of how much randomness is contained in
578\var{string}, measured in bytes. For more information, see e.g. \rfc{1750}.
579\end{funcdesc}
580
581\begin{funcdesc}{egd}{path\optional{, bytes}}
582Query the Entropy Gathering Daemon\footnote{See
583\url{http://www.lothar.com/tech/crypto/}} on socket \var{path} for \var{bytes}
584bytes of random data and and uses \function{add} to seed the PRNG. The default
585value of \var{bytes} is 255.
586\end{funcdesc}
587
588\begin{funcdesc}{load_file}{path\optional{, bytes}}
589Read \var{bytes} bytes (or all of it, if \var{bytes} is negative) of data from
590the file \var{path} to seed the PRNG. The default value of \var{bytes} is -1.
591\end{funcdesc}
592
593\begin{funcdesc}{screen}{}
594Add the current contents of the screen to the PRNG state.
595Availability: Windows.
596\end{funcdesc}
597
598\begin{funcdesc}{seed}{string}
599This is equivalent to calling \function{add} with \var{entropy} as the length
600of the string.
601\end{funcdesc}
602
603\begin{funcdesc}{status}{}
604Returns true if the PRNG has been seeded with enough data, and false otherwise.
605\end{funcdesc}
606
607\begin{funcdesc}{write_file}{path}
608Write a number of random bytes (currently 1024) to the file \var{path}. This
609file can then be used with \function{load_file} to seed the PRNG again.
610\end{funcdesc}
611
612
613
614% % % SSL module
615
616\subsection{\module{SSL} --- An interface to the SSL-specific parts of OpenSSL \label{openssl-ssl}}
617
618\declaremodule{extension}{SSL}
619\modulesynopsis{An interface to the SSL-specific parts of OpenSSL}
620
621This module handles things specific to SSL. There are two objects defined:
622Context, Connection.
623
624\begin{datadesc}{SSLv2_METHOD}
625\dataline{SSLv3_METHOD}
626\dataline{SSLv23_METHOD}
627\dataline{TLSv1_METHOD}
628These constants represent the different SSL methods to use when creating a
629context object.
630\end{datadesc}
631
632\begin{datadesc}{VERIFY_NONE}
633\dataline{VERIFY_PEER}
634\dataline{VERIFY_FAIL_IF_NO_PEER_CERT}
635These constants represent the verification mode used by the Context
636object's \method{set_verify} method.
637\end{datadesc}
638
639\begin{datadesc}{FILETYPE_PEM}
640\dataline{FILETYPE_ASN1}
641File type constants used with the \method{use_certificate_file} and
642\method{use_privatekey_file} methods of Context objects.
643\end{datadesc}
644
645\begin{datadesc}{OP_SINGLE_DH_USE}
646\dataline{OP_EPHEMERAL_RSA}
647\dataline{OP_NO_SSLv2}
648\dataline{OP_NO_SSLv3}
649\dataline{OP_NO_TLSv1}
650Constants used with \method{set_options} of Context objects.
651\constant{OP_SINGLE_DH_USE} means to always create a new key when using ephemeral
652Diffie-Hellman. \constant{OP_EPHEMERAL_RSA} means to always use ephemeral RSA keys
653when doing RSA operations. \constant{OP_NO_SSLv2}, \constant{OP_NO_SSLv3} and
654\constant{OP_NO_TLSv1} means to disable those specific protocols. This is
655interesting if you're using e.g. \constant{SSLv23_METHOD} to get an SSLv2-compatible
656handshake, but don't want to use SSLv2.
657\end{datadesc}
658
659\begin{datadesc}{ContextType}
660A Python type object representing the Context object type.
661\end{datadesc}
662
663\begin{funcdesc}{Context}{method}
664Factory function that creates a new Context object given an SSL method. The
665method should be \constant{SSLv2_METHOD}, \constant{SSLv3_METHOD},
666\constant{SSLv23_METHOD} or \constant{TLSv1_METHOD}.
667\end{funcdesc}
668
669\begin{datadesc}{ConnectionType}
670A Python type object representing the Connection object type.
671\end{datadesc}
672
673\begin{funcdesc}{Connection}{context, socket}
674Factory fucnction that creates a new Connection object given an SSL context and
675a socket \footnote{Actually, all that is required is an object that
676\emph{behaves} like a socket, you could even use files, even though it'd be
677tricky to get the handshakes right!} object.
678\end{funcdesc}
679
680\begin{excdesc}{Error}
681This exception is used as a base class for the other SSL-related
682exceptions, but may also be raised directly.
683
684Whenever this exception is raised directly, it has a list of error messages
685from the OpenSSL error queue, where each item is a tuple \code{(\var{lib},
686\var{function}, \var{reason})}. Here \var{lib}, \var{function} and \var{reason}
687are all strings, describing where and what the problem is. See \manpage{err}{3}
688for more information.
689\end{excdesc}
690
691\begin{excdesc}{ZeroReturnError}
692This exception matches the error return code \code{SSL_ERROR_ZERO_RETURN}, and
693is raised when the SSL Connection has been closed. In SSL 3.0 and TLS 1.0, this
694only occurs if a closure alert has occurred in the protocol, i.e. the
695connection has been closed cleanly. Note that this does not necessarily
696mean that the transport layer (e.g. a socket) has been closed.
697
698It may seem a little strange that this is an exception, but it does match an
699\code{SSL_ERROR} code, and is very convenient.
700\end{excdesc}
701
702\begin{excdesc}{WantReadError}
703The operation did not complete; the same I/O method should be called again
704later, with the same arguments. Any I/O method can lead to this since new
705handshakes can occur at any time.
706\end{excdesc}
707
708\begin{excdesc}{WantWriteError}
709See \exception{WantReadError}.
710\end{excdesc}
711
712\begin{excdesc}{WantX509LookupError}
713The operation did not complete because an application callback has asked to be
714called again. The I/O method should be called again later, with the same
715arguments. Note: This won't occur in this version, as there are no such
716callbacks in this version.
717\end{excdesc}
718
719\begin{excdesc}{SysCallError}
720The \exception{SysCallError} occurs when there's an I/O error and OpenSSL's
721error queue does not contain any information. This can mean two things: An
722error in the transport protocol, or an end of file that violates the protocol.
723The parameter to the exception is always a pair \code{(\var{errnum},
724\var{errstr})}.
725\end{excdesc}
726
727
728\subsubsection{Context objects \label{openssl-context}}
729
730Context objects have the following methods:
731
732\begin{methoddesc}[Context]{check_privatekey}{}
733Check if the private key (loaded with \method{use_privatekey\optional{_file}})
734matches the certificate (loaded with \method{use_certificate\optional{_file}}).
Jean-Paul Calderonef05fbbe2008-03-06 21:52:35 -0500735Returns \code{None} if they match, raises \exception{Error} otherwise.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500736\end{methoddesc}
737
738\begin{methoddesc}[Context]{get_app_data}{}
739Retrieve application data as set by \method{set_app_data}.
740\end{methoddesc}
741
742\begin{methoddesc}[Context]{get_cert_store}{}
743Retrieve the certificate store (a X509Store object) that the context uses.
744This can be used to add "trusted" certificates without using the.
745\method{load_verify_locations()} method.
746\end{methoddesc}
747
748\begin{methoddesc}[Context]{get_timeout}{}
749Retrieve session timeout, as set by \method{set_timeout}. The default is 300
750seconds.
751\end{methoddesc}
752
753\begin{methoddesc}[Context]{get_verify_depth}{}
754Retrieve the Context object's verify depth, as set by
755\method{set_verify_depth}.
756\end{methoddesc}
757
758\begin{methoddesc}[Context]{get_verify_mode}{}
759Retrieve the Context object's verify mode, as set by \method{set_verify_mode}.
760\end{methoddesc}
761
762\begin{methoddesc}[Context]{load_client_ca}{pemfile}
763Read a file with PEM-formatted certificates that will be sent to the client
764when requesting a client certificate.
765\end{methoddesc}
766
767\begin{methoddesc}[Context]{load_verify_locations}{pemfile}
768Specify where CA certificates for verification purposes are located. These are
769trusted certificates. Note that the certificates have to be in PEM format.
770\end{methoddesc}
771
772\begin{methoddesc}[Context]{load_tmp_dh}{dhfile}
773Load parameters for Ephemeral Diffie-Hellman from \var{dhfile}.
774\end{methoddesc}
775
776\begin{methoddesc}[Context]{set_app_data}{data}
777Associate \var{data} with this Context object. \var{data} can be retrieved
778later using the \method{get_app_data} method.
779\end{methoddesc}
780
781\begin{methoddesc}[Context]{set_cipher_list}{ciphers}
782Set the list of ciphers to be used in this context. See the OpenSSL manual for
783more information (e.g. ciphers(1))
784\end{methoddesc}
785
786\begin{methoddesc}[Context]{set_info_callback}{callback}
787Set the information callback to \var{callback}. This function will be called
788from time to time during SSL handshakes.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500789\var{callback} should take three arguments: a Connection object and two
790integers. The first integer specifies where in the SSL handshake the function
791was called, and the other the return code from a (possibly failed) internal
792function call.
793\end{methoddesc}
794
795\begin{methoddesc}[Context]{set_options}{options}
796Add SSL options. Options you have set before are not cleared!
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500797This method should be used with the \constant{OP_*} constants.
798\end{methoddesc}
799
800\begin{methoddesc}[Context]{set_passwd_cb}{callback\optional{, userdata}}
801Set the passphrase callback to \var{callback}. This function will be called
Jean-Paul Calderone1eeb29e2008-10-19 11:50:53 -0400802when a private key with a passphrase is loaded. \var{callback} must accept
803three positional arguments. First, an integer giving the maximum length of
804the passphrase it may return. If the returned passphrase is longer than
805this, it will be truncated. Second, a boolean value which will be true if
806the user should be prompted for the passphrase twice and the callback should
807verify that the two values supplied are equal. Third, the value given as the
808\var{userdata} parameter to \method{set_passwd_cb}. If an error occurs,
809\var{callback} should return a false value (e.g. an empty string).
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500810\end{methoddesc}
811
812\begin{methoddesc}[Context]{set_session_id}{name}
813Set the context \var{name} within which a session can be reused for this
814Context object. This is needed when doing session resumption, because there is
815no way for a stored session to know which Context object it is associated with.
816\var{name} may be any binary data.
817\end{methoddesc}
818
819\begin{methoddesc}[Context]{set_timeout}{timeout}
820Set the timeout for newly created sessions for this Context object to
821\var{timeout}. \var{timeout} must be given in (whole) seconds. The default
822value is 300 seconds. See the OpenSSL manual for more information (e.g.
823SSL_CTX_set_timeout(3)).
824\end{methoddesc}
825
826\begin{methoddesc}[Context]{set_verify}{mode, callback}
827Set the verification flags for this Context object to \var{mode} and specify
828that \var{callback} should be used for verification callbacks. \var{mode}
829should be one of \constant{VERIFY_NONE} and \constant{VERIFY_PEER}. If
830\constant{VERIFY_PEER} is used, \var{mode} can be OR:ed with
831\constant{VERIFY_FAIL_IF_NO_PEER_CERT} and \constant{VERIFY_CLIENT_ONCE} to
832further control the behaviour.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500833\var{callback} should take five arguments: A Connection object, an X509 object,
834and three integer variables, which are in turn potential error number, error
835depth and return code. \var{callback} should return true if verification passes
836and false otherwise.
837\end{methoddesc}
838
839\begin{methoddesc}[Context]{set_verify_depth}{depth}
840Set the maximum depth for the certificate chain verification that shall be
841allowed for this Context object.
842\end{methoddesc}
843
844\begin{methoddesc}[Context]{use_certificate}{cert}
845Use the certificate \var{cert} which has to be a X509 object.
846\end{methoddesc}
847
Jean-Paul Calderone87b40602008-02-19 21:13:25 -0500848\begin{methoddesc}[Context]{add_extra_chain_cert}{cert}
849Adds the certificate \var{cert}, which has to be a X509 object, to the
850certificate chain presented together with the certificate.
851\end{methoddesc}
852
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500853\begin{methoddesc}[Context]{use_certificate_chain_file}{file}
854Load a certificate chain from \var{file} which must be PEM encoded.
855\end{methoddesc}
856
857\begin{methoddesc}[Context]{use_privatekey}{pkey}
858Use the private key \var{pkey} which has to be a PKey object.
859\end{methoddesc}
860
861\begin{methoddesc}[Context]{use_certificate_file}{file\optional{, format}}
862Load the first certificate found in \var{file}. The certificate must be in the
863format specified by \var{format}, which is either \constant{FILETYPE_PEM} or
864\constant{FILETYPE_ASN1}. The default is \constant{FILETYPE_PEM}.
865\end{methoddesc}
866
867\begin{methoddesc}[Context]{use_privatekey_file}{file\optional{, format}}
868Load the first private key found in \var{file}. The private key must be in the
869format specified by \var{format}, which is either \constant{FILETYPE_PEM} or
870\constant{FILETYPE_ASN1}. The default is \constant{FILETYPE_PEM}.
871\end{methoddesc}
872
873
874\subsubsection{Connection objects \label{openssl-connection}}
875
876Connection objects have the following methods:
877
878\begin{methoddesc}[Connection]{accept}{}
879Call the \method{accept} method of the underlying socket and set up SSL on the
880returned socket, using the Context object supplied to this Connection object at
881creation. Returns a pair \code{(\var{conn}, \var{address})}. where \var{conn}
882is the new Connection object created, and \var{address} is as returned by the
883socket's \method{accept}.
884\end{methoddesc}
885
886\begin{methoddesc}[Connection]{bind}{address}
887Call the \method{bind} method of the underlying socket.
888\end{methoddesc}
889
890\begin{methoddesc}[Connection]{close}{}
891Call the \method{close} method of the underlying socket. Note: If you want
892correct SSL closure, you need to call the \method{shutdown} method first.
893\end{methoddesc}
894
895\begin{methoddesc}[Connection]{connect}{address}
896Call the \method{connect} method of the underlying socket and set up SSL on the
897socket, using the Context object supplied to this Connection object at
898creation.
899\end{methoddesc}
900
901\begin{methoddesc}[Connection]{connect_ex}{address}
902Call the \method{connect_ex} method of the underlying socket and set up SSL on
903the socket, using the Context object supplied to this Connection object at
904creation. Note that if the \method{connect_ex} method of the socket doesn't
905return 0, SSL won't be initialized.
906\end{methoddesc}
907
908\begin{methoddesc}[Connection]{do_handshake}{}
909Perform an SSL handshake (usually called after \method{renegotiate} or one of
910\method{set_accept_state} or \method{set_accept_state}). This can raise the
911same exceptions as \method{send} and \method{recv}.
912\end{methoddesc}
913
914\begin{methoddesc}[Connection]{fileno}{}
915Retrieve the file descriptor number for the underlying socket.
916\end{methoddesc}
917
918\begin{methoddesc}[Connection]{listen}{backlog}
919Call the \method{listen} method of the underlying socket.
920\end{methoddesc}
921
922\begin{methoddesc}[Connection]{get_app_data}{}
923Retrieve application data as set by \method{set_app_data}.
924\end{methoddesc}
925
926\begin{methoddesc}[Connection]{get_cipher_list}{}
927Retrieve the list of ciphers used by the Connection object. WARNING: This API
928has changed. It used to take an optional parameter and just return a string,
929but not it returns the entire list in one go.
930\end{methoddesc}
931
932\begin{methoddesc}[Connection]{get_context}{}
933Retrieve the Context object associated with this Connection.
934\end{methoddesc}
935
936\begin{methoddesc}[Connection]{get_peer_certificate}{}
937Retrieve the other side's certificate (if any)
938\end{methoddesc}
939
940\begin{methoddesc}[Connection]{getpeername}{}
941Call the \method{getpeername} method of the underlying socket.
942\end{methoddesc}
943
944\begin{methoddesc}[Connection]{getsockname}{}
945Call the \method{getsockname} method of the underlying socket.
946\end{methoddesc}
947
948\begin{methoddesc}[Connection]{getsockopt}{level, optname\optional{, buflen}}
949Call the \method{getsockopt} method of the underlying socket.
950\end{methoddesc}
951
952\begin{methoddesc}[Connection]{pending}{}
Jean-Paul Calderoneb6f57be2008-03-06 21:22:16 -0500953Retrieve the number of bytes that can be safely read from the SSL buffer
954(\emph{not} the underlying transport buffer).
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500955\end{methoddesc}
956
957\begin{methoddesc}[Connection]{recv}{bufsize}
958Receive data from the Connection. The return value is a string representing the
959data received. The maximum amount of data to be received at once, is specified
960by \var{bufsize}.
961\end{methoddesc}
962
963\begin{methoddesc}[Connection]{renegotiate}{}
964Renegotiate the SSL session. Call this if you wish to change cipher suites or
965anything like that.
966\end{methoddesc}
967
968\begin{methoddesc}[Connection]{send}{string}
969Send the \var{string} data to the Connection.
970\end{methoddesc}
971
972\begin{methoddesc}[Connection]{sendall}{string}
973Send all of the \var{string} data to the Connection. This calls \method{send}
974repeatedly until all data is sent. If an error occurs, it's impossible to tell
975how much data has been sent.
976\end{methoddesc}
977
978\begin{methoddesc}[Connection]{set_accept_state}{}
979Set the connection to work in server mode. The handshake will be handled
980automatically by read/write.
981\end{methoddesc}
982
983\begin{methoddesc}[Connection]{set_app_data}{data}
984Associate \var{data} with this Connection object. \var{data} can be retrieved
985later using the \method{get_app_data} method.
986\end{methoddesc}
987
988\begin{methoddesc}[Connection]{set_connect_state}{}
989Set the connection to work in client mode. The handshake will be handled
990automatically by read/write.
991\end{methoddesc}
992
993\begin{methoddesc}[Connection]{setblocking}{flag}
994Call the \method{setblocking} method of the underlying socket.
995\end{methoddesc}
996
997\begin{methoddesc}[Connection]{setsockopt}{level, optname, value}
998Call the \method{setsockopt} method of the underlying socket.
999\end{methoddesc}
1000
1001\begin{methoddesc}[Connection]{shutdown}{}
1002Send the shutdown message to the Connection. Returns true if the shutdown
1003message exchange is completed and false otherwise (in which case you call
1004\method{recv()} or \method{send()} when the connection becomes
1005readable/writeable.
1006\end{methoddesc}
1007
Jean-Paul Calderone72b8f0f2008-02-21 23:57:40 -05001008\begin{methoddesc}[Connection]{get_shutdown}{}
1009Get the shutdown state of the Connection. Returns a bitvector of either or
1010both of \var{SENT_SHUTDOWN} and \var{RECEIVED_SHUTDOWN}.
1011\end{methoddesc}
1012
1013\begin{methoddesc}[Connection]{set_shutdown}{state}
1014Set the shutdown state of the Connection. \var{state} is a bitvector of
1015either or both of \var{SENT_SHUTDOWN} and \var{RECEIVED_SHUTDOWN}.
1016\end{methoddesc}
1017
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001018\begin{methoddesc}[Connection]{sock_shutdown}{how}
1019Call the \method{shutdown} method of the underlying socket.
1020\end{methoddesc}
1021
1022\begin{methoddesc}[Connection]{state_string}{}
1023Retrieve a verbose string detailing the state of the Connection.
1024\end{methoddesc}
1025
1026\begin{methoddesc}[Connection]{want_read}{}
1027Checks if more data has to be read from the transport layer to complete an
1028operation.
1029\end{methoddesc}
1030
1031\begin{methoddesc}[Connection]{want_write}{}
1032Checks if there is data to write to the transport layer to complete an
1033operation.
1034\end{methoddesc}
1035
1036
1037
1038\section{Internals \label{internals}}
1039
1040We ran into three main problems developing this: Exceptions, callbacks and
1041accessing socket methods. This is what this chapter is about.
1042
1043\subsection{Exceptions \label{exceptions}}
1044
1045We realized early that most of the exceptions would be raised by the I/O
1046functions of OpenSSL, so it felt natural to mimic OpenSSL's error code system,
1047translating them into Python exceptions. This naturally gives us the exceptions
1048\exception{SSL.ZeroReturnError}, \exception{SSL.WantReadError},
1049\exception{SSL.WantWriteError}, \exception{SSL.WantX509LookupError} and
1050\exception{SSL.SysCallError}.
1051
1052For more information about this, see section \ref{openssl-ssl}.
1053
1054
1055\subsection{Callbacks \label{callbacks}}
1056
1057There are a number of problems with callbacks. First of all, OpenSSL is written
1058as a C library, it's not meant to have Python callbacks, so a way around that
1059is needed. Another problem is thread support. A lot of the OpenSSL I/O
1060functions can block if the socket is in blocking mode, and then you want other
1061Python threads to be able to do other things. The real trouble is if you've
Jean-Paul Calderoneb7d6db22008-09-21 18:57:56 -04001062released the global CPython interpreter lock to do a potentially blocking
1063operation, and the operation calls a callback. Then we must take the GIL back,
1064since calling Python APIs without holding it is not allowed.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001065
1066There are two solutions to the first problem, both of which are necessary. The
1067first solution to use is if the C callback allows ''userdata'' to be passed to
1068it (an arbitrary pointer normally). This is great! We can set our Python
1069function object as the real userdata and emulate userdata for the Python
1070function in another way. The other solution can be used if an object with an
1071''app_data'' system always is passed to the callback. For example, the SSL
1072object in OpenSSL has app_data functions and in e.g. the verification
1073callbacks, you can retrieve the related SSL object. What we do is to set our
1074wrapper \class{Connection} object as app_data for the SSL object, and we can
1075easily find the Python callback.
1076
Jean-Paul Calderoneb7d6db22008-09-21 18:57:56 -04001077The other problem is solved using thread local variables. Whenever the GIL is
1078released before calling into an OpenSSL API, the PyThreadState pointer returned
1079by \cfunction{PyEval_SaveState} is stored in a global thread local variable
1080(using Python's own TLS API, \cfunction{PyThread_set_key_value}). When it is
1081necessary to re-acquire the GIL, either after the OpenSSL API returns or in a C
1082callback invoked by that OpenSSL API, the value of the thread local variable is
1083retrieved (\cfunction{PyThread_get_key_value}) and used to re-acquire the GIL.
1084This allows Python threads to execute while OpenSSL APIs are running and allows
1085use of any particular pyOpenSSL object from any Python thread, since there is
1086no per-thread state associated with any of these objects and since OpenSSL is
1087threadsafe (as long as properly initialized, as pyOpenSSL initializes it).
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001088
1089
1090\subsection{Acessing Socket Methods \label{socket-methods}}
1091
1092We quickly saw the benefit of wrapping socket methods in the
1093\class{SSL.Connection} class, for an easy transition into using SSL. The
1094problem here is that the \module{socket} module lacks a C API, and all the
1095methods are declared static. One approach would be to have \module{OpenSSL} as
1096a submodule to the \module{socket} module, placing all the code in
1097\file{socketmodule.c}, but this is obviously not a good solution, since you
1098might not want to import tonnes of extra stuff you're not going to use when
1099importing the \module{socket} module. The other approach is to somehow get a
1100pointer to the method to be called, either the C function, or a callable Python
1101object. This is not really a good solution either, since there's a lot of
1102lookups involved.
1103
1104The way it works is that you have to supply a ``\class{socket}-like'' transport
1105object to the \class{SSL.Connection}. The only requirement of this object is
1106that it has a \method{fileno()} method that returns a file descriptor that's
1107valid at the C level (i.e. you can use the system calls read and write). If you
1108want to use the \method{connect()} or \method{accept()} methods of the
1109\class{SSL.Connection} object, the transport object has to supply such
1110methods too. Apart from them, any method lookups in the \class{SSL.Connection}
1111object that fail are passed on to the underlying transport object.
1112
1113Future changes might be to allow Python-level transport objects, that instead
1114of having \method{fileno()} methods, have \method{read()} and \method{write()}
1115methods, so more advanced features of Python can be used. This would probably
1116entail some sort of OpenSSL ``BIOs'', but converting Python strings back and
1117forth is expensive, so this shouldn't be used unless necessary. Other nice
1118things would be to be able to pass in different transport objects for reading
1119and writing, but then the \method{fileno()} method of \class{SSL.Connection}
1120becomes virtually useless. Also, should the method resolution be used on the
1121read-transport or the write-transport?
1122
1123
1124\end{document}