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Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001\documentclass{howto}
2
3\title{Python OpenSSL Manual}
4
Jean-Paul Calderoned2532d82008-03-25 15:20:39 -04005\release{0.7a2}
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
29The reason this module exists at all is that the SSL support in the socket
30module in the Python 2.1 distribution (which is what we used, of course I
31cannot speak for later versions) is severely limited.
32
33When asking about SSL on the comp.lang.python newsgroup (or on
34python-list@python.org) people usually pointed you to the M2Crypto package.
35The M2Crypto.SSL module does implement a lot of OpenSSL's functionality but
36unfortunately its error handling system does not seem to be finished,
37especially for non-blocking I/O. I think that much of the reason for this
38is that M2Crypto\footnote{See \url{http://www.post1.com/home/ngps/m2/}} is
39developed using SWIG\footnote{See \url{http://swig.sourceforge.net/}}. This
40makes it awkward to create functions that e.g. can return both an integer and
41NULL since (as far as I know) you basically write C functions and SWIG makes
42wrapper functions that parses the Python argument list and calls your C
43function, and finally transforms your return value to a Python object.
44
45
46\section{Building and Installing \label{building}}
47
48These instructions can also be found in the file \verb|INSTALL|.
49
50I have tested this on Debian Linux systems (woody and sid), Solaris 2.6 and
512.7. Others have successfully compiled it on Windows and NT.
52
53\subsection{Building the Module on a Unix System \label{building-unix}}
54
55pyOpenSSL uses distutils, so there really shouldn't be any problems. To build
56the library:
57\begin{verbatim}
58python setup.py build
59\end{verbatim}
60
61If your OpenSSL header files aren't in \verb|/usr/include|, you may need to
62supply the \verb|-I| flag to let the setup script know where to look. The same
63goes for the libraries of course, use the \verb|-L| flag. Note that
64\verb|build| won't accept these flags, so you have to run first
65\verb|build_ext| and then \verb|build|! Example:
66\begin{verbatim}
67python setup.py build_ext -I/usr/local/ssl/include -L/usr/local/ssl/lib
68python setup.py build
69\end{verbatim}
70
71Now you should have a directory called \verb|OpenSSL| that contains e.g.
72\verb|SSL.so| and \verb|__init__.py| somewhere in the build dicrectory,
73so just:
74\begin{verbatim}
75python setup.py install
76\end{verbatim}
77
78If you, for some arcane reason, don't want the module to appear in the
79\verb|site-packages| directory, use the \verb|--prefix| option.
80
81You can, of course, do
82\begin{verbatim}
83python setup.py --help
84\end{verbatim}
85
86to find out more about how to use the script.
87
88\subsection{Building the Module on a Windows System \label{building-windows}}
89
90Big thanks to Itamar Shtull-Trauring and Oleg Orlov for their help with
91Windows build instructions. Same as for Unix systems, we have to separate
92the \verb|build_ext| and the \verb|build|.
93
94Building the library:
95
96\begin{verbatim}
97setup.py build_ext -I ...\openssl\inc32 -L ...\openssl\out32dll
98setup.py build
99\end{verbatim}
100
101Where \verb|...\openssl| is of course the location of your OpenSSL installation.
102
103Installation is the same as for Unix systems:
104\begin{verbatim}
105setup.py install
106\end{verbatim}
107
108And similarily, you can do
109\begin{verbatim}
110setup.py --help
111\end{verbatim}
112
113to get more information.
114
115
116\section{\module{OpenSSL} --- Python interface to OpenSSL \label{openssl}}
117
118\declaremodule{extension}{OpenSSL}
119\modulesynopsis{Python interface to OpenSSL}
120
121This package provides a high-level interface to the functions in the
122OpenSSL library. The following modules are defined:
123
124\begin{datadesc}{crypto}
125Generic cryptographic module. Note that if anything is incomplete, this module is!
126\end{datadesc}
127
128\begin{datadesc}{rand}
129An interface to the OpenSSL pseudo random number generator.
130\end{datadesc}
131
132\begin{datadesc}{SSL}
133An interface to the SSL-specific parts of OpenSSL.
134\end{datadesc}
135
136
137% % % crypto moduleOpenSSL
138
139\subsection{\module{crypto} --- Generic cryptographic module \label{openssl-crypto}}
140
141\declaremodule{extension}{crypto}
142\modulesynopsis{Generic cryptographic module}
143
144\begin{datadesc}{X509Type}
145A Python type object representing the X509 object type.
146\end{datadesc}
147
148\begin{funcdesc}{X509}{}
149Factory function that creates an X509 object.
150\end{funcdesc}
151
152\begin{datadesc}{X509NameType}
153A Python type object representing the X509Name object type.
154\end{datadesc}
155
156\begin{funcdesc}{X509Name}{x509name}
157Factory function that creates a copy of \var{x509name}.
158\end{funcdesc}
159
160\begin{datadesc}{X509ReqType}
161A Python type object representing the X509Req object type.
162\end{datadesc}
163
164\begin{funcdesc}{X509Req}{}
165Factory function that creates an X509Req object.
166\end{funcdesc}
167
168\begin{datadesc}{X509StoreType}
169A Python type object representing the X509Store object type.
170\end{datadesc}
171
172\begin{datadesc}{PKeyType}
173A Python type object representing the PKey object type.
174\end{datadesc}
175
176\begin{funcdesc}{PKey}{}
177Factory function that creates a PKey object.
178\end{funcdesc}
179
180\begin{datadesc}{PKCS7Type}
181A Python type object representing the PKCS7 object type.
182\end{datadesc}
183
184\begin{datadesc}{PKCS12Type}
185A Python type object representing the PKCS12 object type.
186\end{datadesc}
187
188\begin{datadesc}{X509ExtensionType}
189A Python type object representing the X509Extension object type.
190\end{datadesc}
191
192\begin{funcdesc}{X509Extension}{typename, critical, value}
193Factory function that creates a X509Extension object.
194\end{funcdesc}
195
196\begin{datadesc}{NetscapeSPKIType}
197A Python type object representing the NetscapeSPKI object type.
198\end{datadesc}
199
200\begin{funcdesc}{NetscapeSPKI}{\optional{enc}}
201Factory function that creates a NetscapeSPKI object. If the \var{enc} argument
202is present, it should be a base64-encoded string representing a NetscapeSPKI
203object, as returned by the \method{b64_encode} method.
204\end{funcdesc}
205
206\begin{datadesc}{FILETYPE_PEM}
207\dataline{FILETYPE_ASN1}
208File type constants.
209\end{datadesc}
210
211\begin{datadesc}{TYPE_RSA}
212\dataline{TYPE_DSA}
213Key type constants.
214\end{datadesc}
215
216\begin{excdesc}{Error}
217Generic exception used in the \module{crypto} module.
218\end{excdesc}
219
220\begin{funcdesc}{dump_certificate}{type, cert}
221Dump the certificate \var{cert} into a buffer string encoded with the type
222\var{type}.
223\end{funcdesc}
224
225\begin{funcdesc}{dump_certificate_request}{type, req}
226Dump the certificate request \var{req} into a buffer string encoded with the
227type \var{type}.
228\end{funcdesc}
229
230\begin{funcdesc}{dump_privatekey}{type, pkey\optional{, cipher, passphrase}}
231Dump the private key \var{pkey} into a buffer string encoded with the type
232\var{type}, optionally (if \var{type} is \constant{FILETYPE_PEM}) encrypting it
233using \var{cipher} and \var{passphrase}.
234
235\var{passphrase} must be either a string or a callback for providing the
236pass phrase.
237\end{funcdesc}
238
239\begin{funcdesc}{load_certificate}{type, buffer}
240Load a certificate (X509) from the string \var{buffer} encoded with the
241type \var{type}.
242\end{funcdesc}
243
244\begin{funcdesc}{load_certificate_request}{type, buffer}
245Load a certificate request (X509Req) from the string \var{buffer} encoded with
246the type \var{type}.
247\end{funcdesc}
248
249\begin{funcdesc}{load_privatekey}{type, buffer\optional{, passphrase}}
250Load a private key (PKey) from the string \var{buffer} encoded with
251the type \var{type} (must be one of \constant{FILETYPE_PEM} and
252\constant{FILETYPE_ASN1}).
253
254\var{passphrase} must be either a string or a callback for providing the
255pass phrase.
256\end{funcdesc}
257
258\begin{funcdesc}{load_pkcs7_data}{type, buffer}
259Load pkcs7 data from the string \var{buffer} encoded with the type \var{type}.
260\end{funcdesc}
261
262\begin{funcdesc}{load_pkcs12}{buffer\optional{, passphrase}}
263Load pkcs12 data from the string \var{buffer}. If the pkcs12 structure is
264encrypted, a \var{passphrase} must be included.
265\end{funcdesc}
266
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500267\subsubsection{X509 objects \label{openssl-x509}}
268
269X509 objects have the following methods:
270
271\begin{methoddesc}[X509]{get_issuer}{}
Jean-Paul Calderone2aa2b332008-03-06 21:43:14 -0500272Return an X509Name object representing the issuer of the certificate.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500273\end{methoddesc}
274
275\begin{methoddesc}[X509]{get_pubkey}{}
276Return a PKey object representing the public key of the certificate.
277\end{methoddesc}
278
279\begin{methoddesc}[X509]{get_serial_number}{}
280Return the certificate serial number.
281\end{methoddesc}
282
283\begin{methoddesc}[X509]{get_subject}{}
Jean-Paul Calderone2aa2b332008-03-06 21:43:14 -0500284Return an X509Name object representing the subject of the certificate.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500285\end{methoddesc}
286
287\begin{methoddesc}[X509]{get_version}{}
288Return the certificate version.
289\end{methoddesc}
290
Jean-Paul Calderone525ef802008-03-09 20:39:42 -0400291\begin{methoddesc}[X509]{get_notBefore}{}
292Return a string giving the time before which the certificate is not valid. The
293string is formatted as an ASN1 GENERALIZEDTIME:
294\begin{verbatim}
295 YYYYMMDDhhmmssZ
296 YYYYMMDDhhmmss+hhmm
297 YYYYMMDDhhmmss-hhmm
298\end{verbatim}
Jean-Paul Calderonee0615b52008-03-09 21:44:46 -0400299If no value exists for this field, \code{None} is returned.
Jean-Paul Calderone525ef802008-03-09 20:39:42 -0400300\end{methoddesc}
301
302\begin{methoddesc}[X509]{get_notAfter}{}
303Return a string giving the time after which the certificate is not valid. The
304string is formatted as an ASN1 GENERALIZEDTIME:
305\begin{verbatim}
306 YYYYMMDDhhmmssZ
307 YYYYMMDDhhmmss+hhmm
308 YYYYMMDDhhmmss-hhmm
309\end{verbatim}
Jean-Paul Calderonee0615b52008-03-09 21:44:46 -0400310If no value exists for this field, \code{None} is returned.
Jean-Paul Calderone525ef802008-03-09 20:39:42 -0400311\end{methoddesc}
312
313\begin{methoddesc}[X509]{set_notBefore}{when}
314Change the time before which the certificate is not valid. \var{when} is a
315string formatted as an ASN1 GENERALIZEDTIME:
316\begin{verbatim}
317 YYYYMMDDhhmmssZ
318 YYYYMMDDhhmmss+hhmm
319 YYYYMMDDhhmmss-hhmm
320\end{verbatim}
321\end{methoddesc}
322
323\begin{methoddesc}[X509]{set_notAfter}{when}
324Change the time after which the certificate is not valid. \var{when} is a
325string formatted as an ASN1 GENERALIZEDTIME:
326\begin{verbatim}
327 YYYYMMDDhhmmssZ
328 YYYYMMDDhhmmss+hhmm
329 YYYYMMDDhhmmss-hhmm
330\end{verbatim}
331\end{methoddesc}
332
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500333\begin{methoddesc}[X509]{gmtime_adj_notBefore}{time}
334Adjust the timestamp (in GMT) when the certificate starts being valid.
335\end{methoddesc}
336
337\begin{methoddesc}[X509]{gmtime_adj_notAfter}{time}
338Adjust the timestamp (in GMT) when the certificate stops being valid.
339\end{methoddesc}
340
341\begin{methoddesc}[X509]{has_expired}{}
342Checks the certificate's time stamp against current time. Returns true if the
343certificate has expired and false otherwise.
344\end{methoddesc}
345
346\begin{methoddesc}[X509]{set_issuer}{issuer}
347Set the issuer of the certificate to \var{issuer}.
348\end{methoddesc}
349
350\begin{methoddesc}[X509]{set_pubkey}{pkey}
351Set the public key of the certificate to \var{pkey}.
352\end{methoddesc}
353
354\begin{methoddesc}[X509]{set_serial_number}{serialno}
355Set the serial number of the certificate to \var{serialno}.
356\end{methoddesc}
357
358\begin{methoddesc}[X509]{set_subject}{subject}
359Set the subject of the certificate to \var{subject}.
360\end{methoddesc}
361
362\begin{methoddesc}[X509]{set_version}{version}
363Set the certificate version to \var{version}.
364\end{methoddesc}
365
366\begin{methoddesc}[X509]{sign}{pkey, digest}
367Sign the certificate, using the key \var{pkey} and the message digest algorithm
368identified by the string \var{digest}.
369\end{methoddesc}
370
371\begin{methoddesc}[X509]{subject_name_hash}{}
372Return the hash of the certificate subject.
373\end{methoddesc}
374
375\begin{methoddesc}[X509]{digest}{digest_name}
376Return a digest of the certificate, using the \var{digest_name} method.
377\end{methoddesc}
378
379\begin{methoddesc}[X509]{add_extensions}{extensions}
380Add the extensions in the sequence \var{extensions} to the certificate.
381\end{methoddesc}
382
383\subsubsection{X509Name objects \label{openssl-x509name}}
384
Jean-Paul Calderone2dd8ff52008-03-24 17:43:58 -0400385X509Name objects have the following methods:
386
387\begin{methoddesc}[X509Name]{hash}{}
388Return an integer giving the first four bytes of the MD5 digest of the DER
389representation of the name.
390\end{methoddesc}
391
Jean-Paul Calderonea6edbf82008-03-25 15:19:11 -0400392\begin{methoddesc}[X509Name]{der}{}
393Return a string giving the DER representation 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
457\subsubsection{X509Store objects \label{openssl-x509store}}
458
459The X509Store object has currently just one method:
460
461\begin{methoddesc}[X509Store]{add_cert}{cert}
462Add the certificate \var{cert} to the certificate store.
463\end{methoddesc}
464
465\subsubsection{PKey objects \label{openssl-pkey}}
466
467The PKey object has the following methods:
468
469\begin{methoddesc}[PKey]{bits}{}
470Return the number of bits of the key.
471\end{methoddesc}
472
473\begin{methoddesc}[PKey]{generate_key}{type, bits}
474Generate a public/private key pair of the type \var{type} (one of
475\constant{TYPE_RSA} and \constant{TYPE_DSA}) with the size \var{bits}.
476\end{methoddesc}
477
478\begin{methoddesc}[PKey]{type}{}
479Return the type of the key.
480\end{methoddesc}
481
482\subsubsection{PKCS7 objects \label{openssl-pkcs7}}
483
484PKCS7 objects have the following methods:
485
486\begin{methoddesc}[PKCS7]{type_is_signed}{}
487FIXME
488\end{methoddesc}
489
490\begin{methoddesc}[PKCS7]{type_is_enveloped}{}
491FIXME
492\end{methoddesc}
493
494\begin{methoddesc}[PKCS7]{type_is_signedAndEnveloped}{}
495FIXME
496\end{methoddesc}
497
498\begin{methoddesc}[PKCS7]{type_is_data}{}
499FIXME
500\end{methoddesc}
501
502\begin{methoddesc}[PKCS7]{get_type_name}{}
503Get the type name of the PKCS7.
504\end{methoddesc}
505
506\subsubsection{PKCS12 objects \label{openssl-pkcs12}}
507
508PKCS12 objects have the following methods:
509
510\begin{methoddesc}[PKCS12]{get_certificate}{}
511Return certificate portion of the PKCS12 structure.
512\end{methoddesc}
513
514\begin{methoddesc}[PKCS12]{get_privatekey}{}
515Return private key portion of the PKCS12 structure
516\end{methoddesc}
517
518\begin{methoddesc}[PKCS12]{get_ca_certificates}{}
519Return CA certificates within the PKCS12 object as a tuple. Returns
520None if no CA certificates are present.
521\end{methoddesc}
522
523\subsubsection{X509Extension objects \label{openssl-509ext}}
524
525X509Extension objects currently only have one method:
526
527\begin{methoddesc}[X509Extension]{get_critical}{}
528Return the critical field of the extension object.
529\end{methoddesc}
530
531\subsubsection{NetscapeSPKI objects \label{openssl-netscape-spki}}
532
533NetscapeSPKI objects have the following methods:
534
535\begin{methoddesc}[NetscapeSPKI]{b64_encode}{}
536Return a base64-encoded string representation of the object.
537\end{methoddesc}
538
539\begin{methoddesc}[NetscapeSPKI]{get_pubkey}{}
540Return the public key of object.
541\end{methoddesc}
542
543\begin{methoddesc}[NetscapeSPKI]{set_pubkey}{key}
544Set the public key of the object to \var{key}.
545\end{methoddesc}
546
547\begin{methoddesc}[NetscapeSPKI]{sign}{key, digest_name}
548Sign the NetscapeSPKI object using the given \var{key} and \var{digest_name}.
549\end{methoddesc}
550
551\begin{methoddesc}[NetscapeSPKI]{verify}{key}
552Verify the NetscapeSPKI object using the given \var{key}.
553\end{methoddesc}
554
555
556% % % rand module
557
558\subsection{\module{rand} --- An interface to the OpenSSL pseudo random number generator \label{openssl-rand}}
559
560\declaremodule{extension}{rand}
561\modulesynopsis{An interface to the OpenSSL pseudo random number generator}
562
563This module handles the OpenSSL pseudo random number generator (PRNG) and
564declares the following:
565
566\begin{funcdesc}{add}{string, entropy}
567Mix bytes from \var{string} into the PRNG state. The \var{entropy} argument is
568(the lower bound of) an estimate of how much randomness is contained in
569\var{string}, measured in bytes. For more information, see e.g. \rfc{1750}.
570\end{funcdesc}
571
572\begin{funcdesc}{egd}{path\optional{, bytes}}
573Query the Entropy Gathering Daemon\footnote{See
574\url{http://www.lothar.com/tech/crypto/}} on socket \var{path} for \var{bytes}
575bytes of random data and and uses \function{add} to seed the PRNG. The default
576value of \var{bytes} is 255.
577\end{funcdesc}
578
579\begin{funcdesc}{load_file}{path\optional{, bytes}}
580Read \var{bytes} bytes (or all of it, if \var{bytes} is negative) of data from
581the file \var{path} to seed the PRNG. The default value of \var{bytes} is -1.
582\end{funcdesc}
583
584\begin{funcdesc}{screen}{}
585Add the current contents of the screen to the PRNG state.
586Availability: Windows.
587\end{funcdesc}
588
589\begin{funcdesc}{seed}{string}
590This is equivalent to calling \function{add} with \var{entropy} as the length
591of the string.
592\end{funcdesc}
593
594\begin{funcdesc}{status}{}
595Returns true if the PRNG has been seeded with enough data, and false otherwise.
596\end{funcdesc}
597
598\begin{funcdesc}{write_file}{path}
599Write a number of random bytes (currently 1024) to the file \var{path}. This
600file can then be used with \function{load_file} to seed the PRNG again.
601\end{funcdesc}
602
603
604
605% % % SSL module
606
607\subsection{\module{SSL} --- An interface to the SSL-specific parts of OpenSSL \label{openssl-ssl}}
608
609\declaremodule{extension}{SSL}
610\modulesynopsis{An interface to the SSL-specific parts of OpenSSL}
611
612This module handles things specific to SSL. There are two objects defined:
613Context, Connection.
614
615\begin{datadesc}{SSLv2_METHOD}
616\dataline{SSLv3_METHOD}
617\dataline{SSLv23_METHOD}
618\dataline{TLSv1_METHOD}
619These constants represent the different SSL methods to use when creating a
620context object.
621\end{datadesc}
622
623\begin{datadesc}{VERIFY_NONE}
624\dataline{VERIFY_PEER}
625\dataline{VERIFY_FAIL_IF_NO_PEER_CERT}
626These constants represent the verification mode used by the Context
627object's \method{set_verify} method.
628\end{datadesc}
629
630\begin{datadesc}{FILETYPE_PEM}
631\dataline{FILETYPE_ASN1}
632File type constants used with the \method{use_certificate_file} and
633\method{use_privatekey_file} methods of Context objects.
634\end{datadesc}
635
636\begin{datadesc}{OP_SINGLE_DH_USE}
637\dataline{OP_EPHEMERAL_RSA}
638\dataline{OP_NO_SSLv2}
639\dataline{OP_NO_SSLv3}
640\dataline{OP_NO_TLSv1}
641Constants used with \method{set_options} of Context objects.
642\constant{OP_SINGLE_DH_USE} means to always create a new key when using ephemeral
643Diffie-Hellman. \constant{OP_EPHEMERAL_RSA} means to always use ephemeral RSA keys
644when doing RSA operations. \constant{OP_NO_SSLv2}, \constant{OP_NO_SSLv3} and
645\constant{OP_NO_TLSv1} means to disable those specific protocols. This is
646interesting if you're using e.g. \constant{SSLv23_METHOD} to get an SSLv2-compatible
647handshake, but don't want to use SSLv2.
648\end{datadesc}
649
650\begin{datadesc}{ContextType}
651A Python type object representing the Context object type.
652\end{datadesc}
653
654\begin{funcdesc}{Context}{method}
655Factory function that creates a new Context object given an SSL method. The
656method should be \constant{SSLv2_METHOD}, \constant{SSLv3_METHOD},
657\constant{SSLv23_METHOD} or \constant{TLSv1_METHOD}.
658\end{funcdesc}
659
660\begin{datadesc}{ConnectionType}
661A Python type object representing the Connection object type.
662\end{datadesc}
663
664\begin{funcdesc}{Connection}{context, socket}
665Factory fucnction that creates a new Connection object given an SSL context and
666a socket \footnote{Actually, all that is required is an object that
667\emph{behaves} like a socket, you could even use files, even though it'd be
668tricky to get the handshakes right!} object.
669\end{funcdesc}
670
671\begin{excdesc}{Error}
672This exception is used as a base class for the other SSL-related
673exceptions, but may also be raised directly.
674
675Whenever this exception is raised directly, it has a list of error messages
676from the OpenSSL error queue, where each item is a tuple \code{(\var{lib},
677\var{function}, \var{reason})}. Here \var{lib}, \var{function} and \var{reason}
678are all strings, describing where and what the problem is. See \manpage{err}{3}
679for more information.
680\end{excdesc}
681
682\begin{excdesc}{ZeroReturnError}
683This exception matches the error return code \code{SSL_ERROR_ZERO_RETURN}, and
684is raised when the SSL Connection has been closed. In SSL 3.0 and TLS 1.0, this
685only occurs if a closure alert has occurred in the protocol, i.e. the
686connection has been closed cleanly. Note that this does not necessarily
687mean that the transport layer (e.g. a socket) has been closed.
688
689It may seem a little strange that this is an exception, but it does match an
690\code{SSL_ERROR} code, and is very convenient.
691\end{excdesc}
692
693\begin{excdesc}{WantReadError}
694The operation did not complete; the same I/O method should be called again
695later, with the same arguments. Any I/O method can lead to this since new
696handshakes can occur at any time.
697\end{excdesc}
698
699\begin{excdesc}{WantWriteError}
700See \exception{WantReadError}.
701\end{excdesc}
702
703\begin{excdesc}{WantX509LookupError}
704The operation did not complete because an application callback has asked to be
705called again. The I/O method should be called again later, with the same
706arguments. Note: This won't occur in this version, as there are no such
707callbacks in this version.
708\end{excdesc}
709
710\begin{excdesc}{SysCallError}
711The \exception{SysCallError} occurs when there's an I/O error and OpenSSL's
712error queue does not contain any information. This can mean two things: An
713error in the transport protocol, or an end of file that violates the protocol.
714The parameter to the exception is always a pair \code{(\var{errnum},
715\var{errstr})}.
716\end{excdesc}
717
718
719\subsubsection{Context objects \label{openssl-context}}
720
721Context objects have the following methods:
722
723\begin{methoddesc}[Context]{check_privatekey}{}
724Check if the private key (loaded with \method{use_privatekey\optional{_file}})
725matches the certificate (loaded with \method{use_certificate\optional{_file}}).
Jean-Paul Calderonef05fbbe2008-03-06 21:52:35 -0500726Returns \code{None} if they match, raises \exception{Error} otherwise.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500727\end{methoddesc}
728
729\begin{methoddesc}[Context]{get_app_data}{}
730Retrieve application data as set by \method{set_app_data}.
731\end{methoddesc}
732
733\begin{methoddesc}[Context]{get_cert_store}{}
734Retrieve the certificate store (a X509Store object) that the context uses.
735This can be used to add "trusted" certificates without using the.
736\method{load_verify_locations()} method.
737\end{methoddesc}
738
739\begin{methoddesc}[Context]{get_timeout}{}
740Retrieve session timeout, as set by \method{set_timeout}. The default is 300
741seconds.
742\end{methoddesc}
743
744\begin{methoddesc}[Context]{get_verify_depth}{}
745Retrieve the Context object's verify depth, as set by
746\method{set_verify_depth}.
747\end{methoddesc}
748
749\begin{methoddesc}[Context]{get_verify_mode}{}
750Retrieve the Context object's verify mode, as set by \method{set_verify_mode}.
751\end{methoddesc}
752
753\begin{methoddesc}[Context]{load_client_ca}{pemfile}
754Read a file with PEM-formatted certificates that will be sent to the client
755when requesting a client certificate.
756\end{methoddesc}
757
758\begin{methoddesc}[Context]{load_verify_locations}{pemfile}
759Specify where CA certificates for verification purposes are located. These are
760trusted certificates. Note that the certificates have to be in PEM format.
761\end{methoddesc}
762
763\begin{methoddesc}[Context]{load_tmp_dh}{dhfile}
764Load parameters for Ephemeral Diffie-Hellman from \var{dhfile}.
765\end{methoddesc}
766
767\begin{methoddesc}[Context]{set_app_data}{data}
768Associate \var{data} with this Context object. \var{data} can be retrieved
769later using the \method{get_app_data} method.
770\end{methoddesc}
771
772\begin{methoddesc}[Context]{set_cipher_list}{ciphers}
773Set the list of ciphers to be used in this context. See the OpenSSL manual for
774more information (e.g. ciphers(1))
775\end{methoddesc}
776
777\begin{methoddesc}[Context]{set_info_callback}{callback}
778Set the information callback to \var{callback}. This function will be called
779from time to time during SSL handshakes.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500780\var{callback} should take three arguments: a Connection object and two
781integers. The first integer specifies where in the SSL handshake the function
782was called, and the other the return code from a (possibly failed) internal
783function call.
784\end{methoddesc}
785
786\begin{methoddesc}[Context]{set_options}{options}
787Add SSL options. Options you have set before are not cleared!
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500788This method should be used with the \constant{OP_*} constants.
789\end{methoddesc}
790
791\begin{methoddesc}[Context]{set_passwd_cb}{callback\optional{, userdata}}
792Set the passphrase callback to \var{callback}. This function will be called
793when a private key with a passphrase is loaded.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500794\var{callback} should take a boolean argument \var{repeat} and an arbitrary
795argument \var{data} and return the passphrase entered by the user. If
796\var{repeat} is true then \var{callback} should ask for the passphrase twice
797and make sure that the two entries are equal. The \var{data} argument is the
798\var{userdata} variable passed to the \method{set_passwd_cb} method. If an
799error occurs, \var{callback} should return a false value (e.g. an empty
800string).
801\end{methoddesc}
802
803\begin{methoddesc}[Context]{set_session_id}{name}
804Set the context \var{name} within which a session can be reused for this
805Context object. This is needed when doing session resumption, because there is
806no way for a stored session to know which Context object it is associated with.
807\var{name} may be any binary data.
808\end{methoddesc}
809
810\begin{methoddesc}[Context]{set_timeout}{timeout}
811Set the timeout for newly created sessions for this Context object to
812\var{timeout}. \var{timeout} must be given in (whole) seconds. The default
813value is 300 seconds. See the OpenSSL manual for more information (e.g.
814SSL_CTX_set_timeout(3)).
815\end{methoddesc}
816
817\begin{methoddesc}[Context]{set_verify}{mode, callback}
818Set the verification flags for this Context object to \var{mode} and specify
819that \var{callback} should be used for verification callbacks. \var{mode}
820should be one of \constant{VERIFY_NONE} and \constant{VERIFY_PEER}. If
821\constant{VERIFY_PEER} is used, \var{mode} can be OR:ed with
822\constant{VERIFY_FAIL_IF_NO_PEER_CERT} and \constant{VERIFY_CLIENT_ONCE} to
823further control the behaviour.
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500824\var{callback} should take five arguments: A Connection object, an X509 object,
825and three integer variables, which are in turn potential error number, error
826depth and return code. \var{callback} should return true if verification passes
827and false otherwise.
828\end{methoddesc}
829
830\begin{methoddesc}[Context]{set_verify_depth}{depth}
831Set the maximum depth for the certificate chain verification that shall be
832allowed for this Context object.
833\end{methoddesc}
834
835\begin{methoddesc}[Context]{use_certificate}{cert}
836Use the certificate \var{cert} which has to be a X509 object.
837\end{methoddesc}
838
Jean-Paul Calderone87b40602008-02-19 21:13:25 -0500839\begin{methoddesc}[Context]{add_extra_chain_cert}{cert}
840Adds the certificate \var{cert}, which has to be a X509 object, to the
841certificate chain presented together with the certificate.
842\end{methoddesc}
843
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500844\begin{methoddesc}[Context]{use_certificate_chain_file}{file}
845Load a certificate chain from \var{file} which must be PEM encoded.
846\end{methoddesc}
847
848\begin{methoddesc}[Context]{use_privatekey}{pkey}
849Use the private key \var{pkey} which has to be a PKey object.
850\end{methoddesc}
851
852\begin{methoddesc}[Context]{use_certificate_file}{file\optional{, format}}
853Load the first certificate found in \var{file}. The certificate must be in the
854format specified by \var{format}, which is either \constant{FILETYPE_PEM} or
855\constant{FILETYPE_ASN1}. The default is \constant{FILETYPE_PEM}.
856\end{methoddesc}
857
858\begin{methoddesc}[Context]{use_privatekey_file}{file\optional{, format}}
859Load the first private key found in \var{file}. The private key must be in the
860format specified by \var{format}, which is either \constant{FILETYPE_PEM} or
861\constant{FILETYPE_ASN1}. The default is \constant{FILETYPE_PEM}.
862\end{methoddesc}
863
864
865\subsubsection{Connection objects \label{openssl-connection}}
866
867Connection objects have the following methods:
868
869\begin{methoddesc}[Connection]{accept}{}
870Call the \method{accept} method of the underlying socket and set up SSL on the
871returned socket, using the Context object supplied to this Connection object at
872creation. Returns a pair \code{(\var{conn}, \var{address})}. where \var{conn}
873is the new Connection object created, and \var{address} is as returned by the
874socket's \method{accept}.
875\end{methoddesc}
876
877\begin{methoddesc}[Connection]{bind}{address}
878Call the \method{bind} method of the underlying socket.
879\end{methoddesc}
880
881\begin{methoddesc}[Connection]{close}{}
882Call the \method{close} method of the underlying socket. Note: If you want
883correct SSL closure, you need to call the \method{shutdown} method first.
884\end{methoddesc}
885
886\begin{methoddesc}[Connection]{connect}{address}
887Call the \method{connect} method of the underlying socket and set up SSL on the
888socket, using the Context object supplied to this Connection object at
889creation.
890\end{methoddesc}
891
892\begin{methoddesc}[Connection]{connect_ex}{address}
893Call the \method{connect_ex} method of the underlying socket and set up SSL on
894the socket, using the Context object supplied to this Connection object at
895creation. Note that if the \method{connect_ex} method of the socket doesn't
896return 0, SSL won't be initialized.
897\end{methoddesc}
898
899\begin{methoddesc}[Connection]{do_handshake}{}
900Perform an SSL handshake (usually called after \method{renegotiate} or one of
901\method{set_accept_state} or \method{set_accept_state}). This can raise the
902same exceptions as \method{send} and \method{recv}.
903\end{methoddesc}
904
905\begin{methoddesc}[Connection]{fileno}{}
906Retrieve the file descriptor number for the underlying socket.
907\end{methoddesc}
908
909\begin{methoddesc}[Connection]{listen}{backlog}
910Call the \method{listen} method of the underlying socket.
911\end{methoddesc}
912
913\begin{methoddesc}[Connection]{get_app_data}{}
914Retrieve application data as set by \method{set_app_data}.
915\end{methoddesc}
916
917\begin{methoddesc}[Connection]{get_cipher_list}{}
918Retrieve the list of ciphers used by the Connection object. WARNING: This API
919has changed. It used to take an optional parameter and just return a string,
920but not it returns the entire list in one go.
921\end{methoddesc}
922
923\begin{methoddesc}[Connection]{get_context}{}
924Retrieve the Context object associated with this Connection.
925\end{methoddesc}
926
927\begin{methoddesc}[Connection]{get_peer_certificate}{}
928Retrieve the other side's certificate (if any)
929\end{methoddesc}
930
931\begin{methoddesc}[Connection]{getpeername}{}
932Call the \method{getpeername} method of the underlying socket.
933\end{methoddesc}
934
935\begin{methoddesc}[Connection]{getsockname}{}
936Call the \method{getsockname} method of the underlying socket.
937\end{methoddesc}
938
939\begin{methoddesc}[Connection]{getsockopt}{level, optname\optional{, buflen}}
940Call the \method{getsockopt} method of the underlying socket.
941\end{methoddesc}
942
943\begin{methoddesc}[Connection]{pending}{}
Jean-Paul Calderoneb6f57be2008-03-06 21:22:16 -0500944Retrieve the number of bytes that can be safely read from the SSL buffer
945(\emph{not} the underlying transport buffer).
Jean-Paul Calderone897bc252008-02-18 20:50:23 -0500946\end{methoddesc}
947
948\begin{methoddesc}[Connection]{recv}{bufsize}
949Receive data from the Connection. The return value is a string representing the
950data received. The maximum amount of data to be received at once, is specified
951by \var{bufsize}.
952\end{methoddesc}
953
954\begin{methoddesc}[Connection]{renegotiate}{}
955Renegotiate the SSL session. Call this if you wish to change cipher suites or
956anything like that.
957\end{methoddesc}
958
959\begin{methoddesc}[Connection]{send}{string}
960Send the \var{string} data to the Connection.
961\end{methoddesc}
962
963\begin{methoddesc}[Connection]{sendall}{string}
964Send all of the \var{string} data to the Connection. This calls \method{send}
965repeatedly until all data is sent. If an error occurs, it's impossible to tell
966how much data has been sent.
967\end{methoddesc}
968
969\begin{methoddesc}[Connection]{set_accept_state}{}
970Set the connection to work in server mode. The handshake will be handled
971automatically by read/write.
972\end{methoddesc}
973
974\begin{methoddesc}[Connection]{set_app_data}{data}
975Associate \var{data} with this Connection object. \var{data} can be retrieved
976later using the \method{get_app_data} method.
977\end{methoddesc}
978
979\begin{methoddesc}[Connection]{set_connect_state}{}
980Set the connection to work in client mode. The handshake will be handled
981automatically by read/write.
982\end{methoddesc}
983
984\begin{methoddesc}[Connection]{setblocking}{flag}
985Call the \method{setblocking} method of the underlying socket.
986\end{methoddesc}
987
988\begin{methoddesc}[Connection]{setsockopt}{level, optname, value}
989Call the \method{setsockopt} method of the underlying socket.
990\end{methoddesc}
991
992\begin{methoddesc}[Connection]{shutdown}{}
993Send the shutdown message to the Connection. Returns true if the shutdown
994message exchange is completed and false otherwise (in which case you call
995\method{recv()} or \method{send()} when the connection becomes
996readable/writeable.
997\end{methoddesc}
998
Jean-Paul Calderone72b8f0f2008-02-21 23:57:40 -0500999\begin{methoddesc}[Connection]{get_shutdown}{}
1000Get the shutdown state of the Connection. Returns a bitvector of either or
1001both of \var{SENT_SHUTDOWN} and \var{RECEIVED_SHUTDOWN}.
1002\end{methoddesc}
1003
1004\begin{methoddesc}[Connection]{set_shutdown}{state}
1005Set the shutdown state of the Connection. \var{state} is a bitvector of
1006either or both of \var{SENT_SHUTDOWN} and \var{RECEIVED_SHUTDOWN}.
1007\end{methoddesc}
1008
Jean-Paul Calderone897bc252008-02-18 20:50:23 -05001009\begin{methoddesc}[Connection]{sock_shutdown}{how}
1010Call the \method{shutdown} method of the underlying socket.
1011\end{methoddesc}
1012
1013\begin{methoddesc}[Connection]{state_string}{}
1014Retrieve a verbose string detailing the state of the Connection.
1015\end{methoddesc}
1016
1017\begin{methoddesc}[Connection]{want_read}{}
1018Checks if more data has to be read from the transport layer to complete an
1019operation.
1020\end{methoddesc}
1021
1022\begin{methoddesc}[Connection]{want_write}{}
1023Checks if there is data to write to the transport layer to complete an
1024operation.
1025\end{methoddesc}
1026
1027
1028
1029\section{Internals \label{internals}}
1030
1031We ran into three main problems developing this: Exceptions, callbacks and
1032accessing socket methods. This is what this chapter is about.
1033
1034\subsection{Exceptions \label{exceptions}}
1035
1036We realized early that most of the exceptions would be raised by the I/O
1037functions of OpenSSL, so it felt natural to mimic OpenSSL's error code system,
1038translating them into Python exceptions. This naturally gives us the exceptions
1039\exception{SSL.ZeroReturnError}, \exception{SSL.WantReadError},
1040\exception{SSL.WantWriteError}, \exception{SSL.WantX509LookupError} and
1041\exception{SSL.SysCallError}.
1042
1043For more information about this, see section \ref{openssl-ssl}.
1044
1045
1046\subsection{Callbacks \label{callbacks}}
1047
1048There are a number of problems with callbacks. First of all, OpenSSL is written
1049as a C library, it's not meant to have Python callbacks, so a way around that
1050is needed. Another problem is thread support. A lot of the OpenSSL I/O
1051functions can block if the socket is in blocking mode, and then you want other
1052Python threads to be able to do other things. The real trouble is if you've
1053released the thread lock to do a potentially blocking operation, and the
1054operation calls a callback. Then we must take the thread lock back\footnote{I'm
1055not sure why this is necessary, but otherwise I get a segmentation violation on
1056\cfunction{PyEval_CallObject}}.
1057
1058There are two solutions to the first problem, both of which are necessary. The
1059first solution to use is if the C callback allows ''userdata'' to be passed to
1060it (an arbitrary pointer normally). This is great! We can set our Python
1061function object as the real userdata and emulate userdata for the Python
1062function in another way. The other solution can be used if an object with an
1063''app_data'' system always is passed to the callback. For example, the SSL
1064object in OpenSSL has app_data functions and in e.g. the verification
1065callbacks, you can retrieve the related SSL object. What we do is to set our
1066wrapper \class{Connection} object as app_data for the SSL object, and we can
1067easily find the Python callback.
1068
1069The other problem is also partially solved by app_data. Since we're associating
1070our wrapper objects with the ''real'' objects, we can easily access data from
1071the \class{Connection} object. The solution then is to simply include a
1072\ctype{PyThreadState} variable in the \class{Connection} declaration, and write
1073macros similar to \cfunction{Py_BEGIN_ALLOW_THREADS} and
1074\cfunction{Py_END_ALLOW_THREADS} that allows specifying of the
1075\ctype{PyThreadState} variable to use. Now we can simply ''begin allow
1076threads'' before a potentially blocking operation, and ''end allow threads''
1077before calling a callback.
1078
1079
1080\subsection{Acessing Socket Methods \label{socket-methods}}
1081
1082We quickly saw the benefit of wrapping socket methods in the
1083\class{SSL.Connection} class, for an easy transition into using SSL. The
1084problem here is that the \module{socket} module lacks a C API, and all the
1085methods are declared static. One approach would be to have \module{OpenSSL} as
1086a submodule to the \module{socket} module, placing all the code in
1087\file{socketmodule.c}, but this is obviously not a good solution, since you
1088might not want to import tonnes of extra stuff you're not going to use when
1089importing the \module{socket} module. The other approach is to somehow get a
1090pointer to the method to be called, either the C function, or a callable Python
1091object. This is not really a good solution either, since there's a lot of
1092lookups involved.
1093
1094The way it works is that you have to supply a ``\class{socket}-like'' transport
1095object to the \class{SSL.Connection}. The only requirement of this object is
1096that it has a \method{fileno()} method that returns a file descriptor that's
1097valid at the C level (i.e. you can use the system calls read and write). If you
1098want to use the \method{connect()} or \method{accept()} methods of the
1099\class{SSL.Connection} object, the transport object has to supply such
1100methods too. Apart from them, any method lookups in the \class{SSL.Connection}
1101object that fail are passed on to the underlying transport object.
1102
1103Future changes might be to allow Python-level transport objects, that instead
1104of having \method{fileno()} methods, have \method{read()} and \method{write()}
1105methods, so more advanced features of Python can be used. This would probably
1106entail some sort of OpenSSL ``BIOs'', but converting Python strings back and
1107forth is expensive, so this shouldn't be used unless necessary. Other nice
1108things would be to be able to pass in different transport objects for reading
1109and writing, but then the \method{fileno()} method of \class{SSL.Connection}
1110becomes virtually useless. Also, should the method resolution be used on the
1111read-transport or the write-transport?
1112
1113
1114\end{document}