3 \title{Python OpenSSL Manual}
7 \author{Jean-Paul Calderone}
8 \authoraddress{\email{exarkun@twistedmatrix.com}}
10 \usepackage[english]{babel}
11 \usepackage[T1]{fontenc}
19 This module is a rather thin wrapper around (a subset of) the OpenSSL library.
20 With thin wrapper I mean that a lot of the object methods do nothing more than
21 calling a corresponding function in the OpenSSL library.
27 \section{Introduction \label{intro}}
29 The reason pyOpenSSL was created is that the SSL support in the socket module
30 in Python 2.1 (the contemporary version of Python when the pyOpenSSL project
31 was begun) was severely limited. Other OpenSSL wrappers for Python at the time
32 were also limited, though in different ways. Unfortunately, Python's standard
33 library SSL support has remained weak, although other packages (such as
34 M2Crypto\footnote{See \url{http://chandlerproject.org/Projects/MeTooCrypto}})
35 have made great advances and now equal or exceed pyOpenSSL's functionality.
37 The reason pyOpenSSL continues to be maintained is that there is a significant
38 user community around it, as well as a large amount of software which depends
39 on it. It is a great benefit to many people for pyOpenSSL to continue to exist
42 \section{Building and Installing \label{building}}
44 These instructions can also be found in the file \verb|INSTALL|.
46 I have tested this on Debian Linux systems (woody and sid), Solaris 2.6 and
47 2.7. Others have successfully compiled it on Windows and NT.
49 \subsection{Building the Module on a Unix System \label{building-unix}}
51 pyOpenSSL uses distutils, so there really shouldn't be any problems. To build
57 If your OpenSSL header files aren't in \verb|/usr/include|, you may need to
58 supply the \verb|-I| flag to let the setup script know where to look. The same
59 goes 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:
63 python setup.py build_ext -I/usr/local/ssl/include -L/usr/local/ssl/lib
67 Now 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,
71 python setup.py install
74 If you, for some arcane reason, don't want the module to appear in the
75 \verb|site-packages| directory, use the \verb|--prefix| option.
77 You can, of course, do
79 python setup.py --help
82 to find out more about how to use the script.
84 \subsection{Building the Module on a Windows System \label{building-windows}}
86 Big thanks to Itamar Shtull-Trauring and Oleg Orlov for their help with
87 Windows build instructions. Same as for Unix systems, we have to separate
88 the \verb|build_ext| and the \verb|build|.
93 setup.py build_ext -I ...\openssl\inc32 -L ...\openssl\out32dll
97 Where \verb|...\openssl| is of course the location of your OpenSSL installation.
99 Installation is the same as for Unix systems:
104 And similarily, you can do
109 to get more information.
112 \section{\module{OpenSSL} --- Python interface to OpenSSL \label{openssl}}
114 \declaremodule{extension}{OpenSSL}
115 \modulesynopsis{Python interface to OpenSSL}
117 This package provides a high-level interface to the functions in the
118 OpenSSL library. The following modules are defined:
120 \begin{datadesc}{crypto}
121 Generic cryptographic module. Note that if anything is incomplete, this module is!
124 \begin{datadesc}{rand}
125 An interface to the OpenSSL pseudo random number generator.
128 \begin{datadesc}{SSL}
129 An interface to the SSL-specific parts of OpenSSL.
133 % % % crypto moduleOpenSSL
135 \subsection{\module{crypto} --- Generic cryptographic module \label{openssl-crypto}}
137 \declaremodule{extension}{crypto}
138 \modulesynopsis{Generic cryptographic module}
140 \begin{datadesc}{X509Type}
144 \begin{classdesc}{X509}{}
145 A class representing X.509 certificates.
148 \begin{datadesc}{X509NameType}
149 See \class{X509Name}.
152 \begin{classdesc}{X509Name}{x509name}
153 A class representing X.509 Distinguished Names.
155 This constructor creates a copy of \var{x509name} which should be an
156 instance of \class{X509Name}.
159 \begin{datadesc}{X509ReqType}
163 \begin{classdesc}{X509Req}{}
164 A class representing X.509 certificate requests.
167 \begin{datadesc}{X509StoreType}
168 A Python type object representing the X509Store object type.
171 \begin{datadesc}{PKeyType}
175 \begin{classdesc}{PKey}{}
176 A class representing DSA or RSA keys.
179 \begin{datadesc}{PKCS7Type}
180 A Python type object representing the PKCS7 object type.
183 \begin{datadesc}{PKCS12Type}
184 A Python type object representing the PKCS12 object type.
187 \begin{datadesc}{X509ExtensionType}
188 See \class{X509Extension}.
191 \begin{classdesc}{X509Extension}{typename, critical, value\optional{, subject}\optional{, issuer}}
192 A class representing an X.509 v3 certificate extensions.
193 See \url{http://openssl.org/docs/apps/x509v3_config.html\#STANDARD_EXTENSIONS}
194 for \var{typename} strings and their options.
195 Optional parameters \var{subject} and \var{issuer} must be X509 objects.
198 \begin{datadesc}{NetscapeSPKIType}
199 See \class{NetscapeSPKI}.
202 \begin{classdesc}{NetscapeSPKI}{\optional{enc}}
203 A class representing Netscape SPKI objects.
205 If the \var{enc} argument is present, it should be a base64-encoded string
206 representing a NetscapeSPKI object, as returned by the \method{b64_encode}
210 \begin{classdesc}{CRL}{}
211 A class representing Certifcate Revocation List objects.
214 \begin{classdesc}{Revoked}{}
215 A class representing Revocation objects of CRL.
218 \begin{datadesc}{FILETYPE_PEM}
219 \dataline{FILETYPE_ASN1}
223 \begin{datadesc}{TYPE_RSA}
228 \begin{excdesc}{Error}
229 Generic exception used in the \module{crypto} module.
232 \begin{funcdesc}{dump_certificate}{type, cert}
233 Dump the certificate \var{cert} into a buffer string encoded with the type
237 \begin{funcdesc}{dump_certificate_request}{type, req}
238 Dump the certificate request \var{req} into a buffer string encoded with the
242 \begin{funcdesc}{dump_privatekey}{type, pkey\optional{, cipher, passphrase}}
243 Dump the private key \var{pkey} into a buffer string encoded with the type
244 \var{type}, optionally (if \var{type} is \constant{FILETYPE_PEM}) encrypting it
245 using \var{cipher} and \var{passphrase}.
247 \var{passphrase} must be either a string or a callback for providing the
251 \begin{funcdesc}{load_certificate}{type, buffer}
252 Load a certificate (X509) from the string \var{buffer} encoded with the
256 \begin{funcdesc}{load_certificate_request}{type, buffer}
257 Load a certificate request (X509Req) from the string \var{buffer} encoded with
261 \begin{funcdesc}{load_privatekey}{type, buffer\optional{, passphrase}}
262 Load a private key (PKey) from the string \var{buffer} encoded with
263 the type \var{type} (must be one of \constant{FILETYPE_PEM} and
264 \constant{FILETYPE_ASN1}).
266 \var{passphrase} must be either a string or a callback for providing the
270 \begin{funcdesc}{load_crl}{type, buffer}
271 Load Certificate Revocation List (CRL) data from a string \var{buffer}.
272 \var{buffer} encoded with the type \var{type}. The type \var{type}
273 must either \constant{FILETYPE_PEM} or \constant{FILETYPE_ASN1}).
276 \begin{funcdesc}{load_pkcs7_data}{type, buffer}
277 Load pkcs7 data from the string \var{buffer} encoded with the type \var{type}.
280 \begin{funcdesc}{load_pkcs12}{buffer\optional{, passphrase}}
281 Load pkcs12 data from the string \var{buffer}. If the pkcs12 structure is
282 encrypted, a \var{passphrase} must be included. The MAC is always
283 checked and thus required.
285 See also the man page for the C function \function{PKCS12_parse}.
288 \begin{funcdesc}{sign}{key, data, digest}
289 Sign a data string using the given key and message digest.
291 \var{key} is a \code{PKey} instance. \var{data} is a \code{str} instance.
292 \var{digest} is a \code{str} naming a supported message digest type, for example
297 \begin{funcdesc}{verify}{certificate, signature, data, digest}
298 Verify the signature for a data string.
300 \var{certificate} is a \code{X509} instance corresponding to the private key
301 which generated the signature. \var{signature} is a \var{str} instance giving
302 the signature itself. \var{data} is a \var{str} instance giving the data to
303 which the signature applies. \var{digest} is a \var{str} instance naming the
304 message digest type of the signature, for example \code{``sha1''}.
308 \subsubsection{X509Extension objects \label{openssl-x509ext}}
310 X509Extension objects have the following methods:
312 \begin{methoddesc}[X509Extension]{get_short_name}{}
313 Retrieve the short descriptive name for this extension.
315 The result is a byte string like \code{``basicConstraints''}.
319 \begin{methoddesc}[X509Extension]{get_data}{}
320 Retrieve the data for this extension.
322 The result is the ASN.1 encoded form of the extension data as a byte string.
326 \subsubsection{X509 objects \label{openssl-x509}}
328 X509 objects have the following methods:
330 \begin{methoddesc}[X509]{get_issuer}{}
331 Return an X509Name object representing the issuer of the certificate.
334 \begin{methoddesc}[X509]{get_pubkey}{}
335 Return a PKey object representing the public key of the certificate.
338 \begin{methoddesc}[X509]{get_serial_number}{}
339 Return the certificate serial number.
342 \begin{methoddesc}[X509]{get_subject}{}
343 Return an X509Name object representing the subject of the certificate.
346 \begin{methoddesc}[X509]{get_version}{}
347 Return the certificate version.
350 \begin{methoddesc}[X509]{get_notBefore}{}
351 Return a string giving the time before which the certificate is not valid. The
352 string is formatted as an ASN1 GENERALIZEDTIME:
358 If no value exists for this field, \code{None} is returned.
361 \begin{methoddesc}[X509]{get_notAfter}{}
362 Return a string giving the time after which the certificate is not valid. The
363 string is formatted as an ASN1 GENERALIZEDTIME:
369 If no value exists for this field, \code{None} is returned.
372 \begin{methoddesc}[X509]{set_notBefore}{when}
373 Change the time before which the certificate is not valid. \var{when} is a
374 string formatted as an ASN1 GENERALIZEDTIME:
382 \begin{methoddesc}[X509]{set_notAfter}{when}
383 Change the time after which the certificate is not valid. \var{when} is a
384 string formatted as an ASN1 GENERALIZEDTIME:
392 \begin{methoddesc}[X509]{gmtime_adj_notBefore}{time}
393 Adjust the timestamp (in GMT) when the certificate starts being valid.
396 \begin{methoddesc}[X509]{gmtime_adj_notAfter}{time}
397 Adjust the timestamp (in GMT) when the certificate stops being valid.
400 \begin{methoddesc}[X509]{has_expired}{}
401 Checks the certificate's time stamp against current time. Returns true if the
402 certificate has expired and false otherwise.
405 \begin{methoddesc}[X509]{set_issuer}{issuer}
406 Set the issuer of the certificate to \var{issuer}.
409 \begin{methoddesc}[X509]{set_pubkey}{pkey}
410 Set the public key of the certificate to \var{pkey}.
413 \begin{methoddesc}[X509]{set_serial_number}{serialno}
414 Set the serial number of the certificate to \var{serialno}.
417 \begin{methoddesc}[X509]{set_subject}{subject}
418 Set the subject of the certificate to \var{subject}.
421 \begin{methoddesc}[X509]{set_version}{version}
422 Set the certificate version to \var{version}.
425 \begin{methoddesc}[X509]{sign}{pkey, digest}
426 Sign the certificate, using the key \var{pkey} and the message digest algorithm
427 identified by the string \var{digest}.
430 \begin{methoddesc}[X509]{subject_name_hash}{}
431 Return the hash of the certificate subject.
434 \begin{methoddesc}[X509]{digest}{digest_name}
435 Return a digest of the certificate, using the \var{digest_name} method.
436 \var{digest_name} must be a string describing a digest algorithm supported
437 by OpenSSL (by EVP_get_digestbyname, specifically). For example,
438 \constant{"md5"} or \constant{"sha1"}.
441 \begin{methoddesc}[X509]{add_extensions}{extensions}
442 Add the extensions in the sequence \var{extensions} to the certificate.
445 \begin{methoddesc}[X509]{get_extension_count}{}
446 Return the number of extensions on this certificate.
450 \begin{methoddesc}[X509]{get_extension}{index}
451 Retrieve the extension on this certificate at the given index.
453 Extensions on a certificate are kept in order. The index parameter selects
454 which extension will be returned. The returned object will be an X509Extension
459 \subsubsection{X509Name objects \label{openssl-x509name}}
461 X509Name objects have the following methods:
463 \begin{methoddesc}[X509Name]{hash}{}
464 Return an integer giving the first four bytes of the MD5 digest of the DER
465 representation of the name.
468 \begin{methoddesc}[X509Name]{der}{}
469 Return a string giving the DER representation of the name.
472 \begin{methoddesc}[X509Name]{get_components}{}
473 Return a list of two-tuples of strings giving the components of the name.
476 X509Name objects have the following members:
478 \begin{memberdesc}[X509Name]{countryName}
479 The country of the entity. \code{C} may be used as an alias for
483 \begin{memberdesc}[X509Name]{stateOrProvinceName}
484 The state or province of the entity. \code{ST} may be used as an alias for
485 \code{stateOrProvinceName}·
488 \begin{memberdesc}[X509Name]{localityName}
489 The locality of the entity. \code{L} may be used as an alias for
493 \begin{memberdesc}[X509Name]{organizationName}
494 The organization name of the entity. \code{O} may be used as an alias for
495 \code{organizationName}.
498 \begin{memberdesc}[X509Name]{organizationalUnitName}
499 The organizational unit of the entity. \code{OU} may be used as an alias for
500 \code{organizationalUnitName}.
503 \begin{memberdesc}[X509Name]{commonName}
504 The common name of the entity. \code{CN} may be used as an alias for
508 \begin{memberdesc}[X509Name]{emailAddress}
509 The e-mail address of the entity.
512 \subsubsection{X509Req objects \label{openssl-x509req}}
514 X509Req objects have the following methods:
516 \begin{methoddesc}[X509Req]{get_pubkey}{}
517 Return a PKey object representing the public key of the certificate request.
520 \begin{methoddesc}[X509Req]{get_subject}{}
521 Return an X509Name object representing the subject of the certificate.
524 \begin{methoddesc}[X509Req]{set_pubkey}{pkey}
525 Set the public key of the certificate request to \var{pkey}.
528 \begin{methoddesc}[X509Req]{sign}{pkey, digest}
529 Sign the certificate request, using the key \var{pkey} and the message digest
530 algorithm identified by the string \var{digest}.
533 \begin{methoddesc}[X509Req]{verify}{pkey}
534 Verify a certificate request using the public key \var{pkey}.
537 \begin{methoddesc}[X509Req]{set_version}{version}
538 Set the version (RFC 2459, 4.1.2.1) of the certificate request to
542 \begin{methoddesc}[X509Req]{get_version}{}
543 Get the version (RFC 2459, 4.1.2.1) of the certificate request.
546 \subsubsection{X509Store objects \label{openssl-x509store}}
548 The X509Store object has currently just one method:
550 \begin{methoddesc}[X509Store]{add_cert}{cert}
551 Add the certificate \var{cert} to the certificate store.
554 \subsubsection{PKey objects \label{openssl-pkey}}
556 The PKey object has the following methods:
558 \begin{methoddesc}[PKey]{bits}{}
559 Return the number of bits of the key.
562 \begin{methoddesc}[PKey]{generate_key}{type, bits}
563 Generate a public/private key pair of the type \var{type} (one of
564 \constant{TYPE_RSA} and \constant{TYPE_DSA}) with the size \var{bits}.
567 \begin{methoddesc}[PKey]{type}{}
568 Return the type of the key.
571 \subsubsection{PKCS7 objects \label{openssl-pkcs7}}
573 PKCS7 objects have the following methods:
575 \begin{methoddesc}[PKCS7]{type_is_signed}{}
579 \begin{methoddesc}[PKCS7]{type_is_enveloped}{}
583 \begin{methoddesc}[PKCS7]{type_is_signedAndEnveloped}{}
587 \begin{methoddesc}[PKCS7]{type_is_data}{}
591 \begin{methoddesc}[PKCS7]{get_type_name}{}
592 Get the type name of the PKCS7.
595 \subsubsection{PKCS12 objects \label{openssl-pkcs12}}
597 PKCS12 objects have the following methods:
599 \begin{methoddesc}[PKCS12]{export}{\optional{passphrase=None}\optional{, iter=2048}\optional{, maciter=1}}
600 Returns a PKCS12 object as a string.
602 The optional \var{passphrase} must be a string not a callback.
604 See also the man page for the C function \function{PKCS12_create}.
607 \begin{methoddesc}[PKCS12]{get_ca_certificates}{}
608 Return CA certificates within the PKCS12 object as a tuple. Returns
609 \constant{None} if no CA certificates are present.
612 \begin{methoddesc}[PKCS12]{get_certificate}{}
613 Return certificate portion of the PKCS12 structure.
616 \begin{methoddesc}[PKCS12]{get_friendlyname}{}
617 Return friendlyName portion of the PKCS12 structure.
620 \begin{methoddesc}[PKCS12]{get_privatekey}{}
621 Return private key portion of the PKCS12 structure
624 \begin{methoddesc}[PKCS12]{set_ca_certificates}{cacerts}
625 Replace or set the CA certificates within the PKCS12 object with the sequence \var{cacerts}.
627 Set \var{cacerts} to \constant{None} to remove all CA certificates.
630 \begin{methoddesc}[PKCS12]{set_certificate}{cert}
631 Replace or set the certificate portion of the PKCS12 structure.
634 \begin{methoddesc}[PKCS12]{set_friendlyname}{name}
635 Replace or set the friendlyName portion of the PKCS12 structure.
638 \begin{methoddesc}[PKCS12]{set_privatekey}{pkey}
639 Replace or set private key portion of the PKCS12 structure
642 \subsubsection{X509Extension objects \label{openssl-509ext}}
644 X509Extension objects have several methods:
646 \begin{methoddesc}[X509Extension]{get_critical}{}
647 Return the critical field of the extension object.
650 \begin{methoddesc}[X509Extension]{get_short_name}{}
651 Return the short type name of the extension object.
654 \subsubsection{NetscapeSPKI objects \label{openssl-netscape-spki}}
656 NetscapeSPKI objects have the following methods:
658 \begin{methoddesc}[NetscapeSPKI]{b64_encode}{}
659 Return a base64-encoded string representation of the object.
662 \begin{methoddesc}[NetscapeSPKI]{get_pubkey}{}
663 Return the public key of object.
666 \begin{methoddesc}[NetscapeSPKI]{set_pubkey}{key}
667 Set the public key of the object to \var{key}.
670 \begin{methoddesc}[NetscapeSPKI]{sign}{key, digest_name}
671 Sign the NetscapeSPKI object using the given \var{key} and
672 \var{digest_name}. \var{digest_name} must be a string describing a digest
673 algorithm supported by OpenSSL (by EVP_get_digestbyname, specifically). For
674 example, \constant{"md5"} or \constant{"sha1"}.
677 \begin{methoddesc}[NetscapeSPKI]{verify}{key}
678 Verify the NetscapeSPKI object using the given \var{key}.
681 \subsubsection{CRL objects \label{crl}}
683 CRL objects have the following methods:
685 \begin{methoddesc}[CRL]{add_revoked}{revoked}
686 Add a Revoked object to the CRL, by value not reference.
689 \begin{methoddesc}[CRL]{export}{cert, key\optional{, type=FILETYPE_PEM}\optional{, days=100}}
690 Use \var{cert} and \var{key} to sign the CRL and return the CRL as a string.
691 \var{days} is the number of days before the next CRL is due.
694 \begin{methoddesc}[CRL]{get_revoked}{}
695 Return a tuple of Revoked objects, by value not reference.
698 \subsubsection{Revoked objects \label{revoked}}
700 Revoked objects have the following methods:
702 \begin{methoddesc}[Revoked]{all_reasons}{}
703 Return a list of all supported reasons.
706 \begin{methoddesc}[Revoked]{get_reason}{}
707 Return the revocation reason as a str. Can be
708 None, which differs from "Unspecified".
711 \begin{methoddesc}[Revoked]{get_rev_date}{}
712 Return the revocation date as a str.
713 The string is formatted as an ASN1 GENERALIZEDTIME.
716 \begin{methoddesc}[Revoked]{get_serial}{}
717 Return a str containing a hex number of the serial of the revoked certificate.
720 \begin{methoddesc}[Revoked]{set_reason}{reason}
721 Set the revocation reason. \var{reason} must
722 be None or a string, but the values are limited.
723 Spaces and case are ignored. See \method{all_reasons}.
726 \begin{methoddesc}[Revoked]{set_rev_date}{date}
727 Set the revocation date.
728 The string is formatted as an ASN1 GENERALIZEDTIME.
731 \begin{methoddesc}[Revoked]{set_serial}{serial}
732 \var{serial} is a string containing a hex number of the serial of the revoked certificate.
738 \subsection{\module{rand} --- An interface to the OpenSSL pseudo random number generator \label{openssl-rand}}
740 \declaremodule{extension}{rand}
741 \modulesynopsis{An interface to the OpenSSL pseudo random number generator}
743 This module handles the OpenSSL pseudo random number generator (PRNG) and
744 declares the following:
746 \begin{funcdesc}{add}{string, entropy}
747 Mix bytes from \var{string} into the PRNG state. The \var{entropy} argument is
748 (the lower bound of) an estimate of how much randomness is contained in
749 \var{string}, measured in bytes. For more information, see e.g. \rfc{1750}.
752 \begin{funcdesc}{bytes}{num_bytes}
753 Get some random bytes from the PRNG as a string.
755 This is a wrapper for the C function \function{RAND_bytes}.
758 \begin{funcdesc}{cleanup}{}
759 Erase the memory used by the PRNG.
761 This is a wrapper for the C function \function{RAND_cleanup}.
764 \begin{funcdesc}{egd}{path\optional{, bytes}}
765 Query the Entropy Gathering Daemon\footnote{See
766 \url{http://www.lothar.com/tech/crypto/}} on socket \var{path} for \var{bytes}
767 bytes of random data and and uses \function{add} to seed the PRNG. The default
768 value of \var{bytes} is 255.
771 \begin{funcdesc}{load_file}{path\optional{, bytes}}
772 Read \var{bytes} bytes (or all of it, if \var{bytes} is negative) of data from
773 the file \var{path} to seed the PRNG. The default value of \var{bytes} is -1.
776 \begin{funcdesc}{screen}{}
777 Add the current contents of the screen to the PRNG state.
778 Availability: Windows.
781 \begin{funcdesc}{seed}{string}
782 This is equivalent to calling \function{add} with \var{entropy} as the length
786 \begin{funcdesc}{status}{}
787 Returns true if the PRNG has been seeded with enough data, and false otherwise.
790 \begin{funcdesc}{write_file}{path}
791 Write a number of random bytes (currently 1024) to the file \var{path}. This
792 file can then be used with \function{load_file} to seed the PRNG again.
795 \begin{excdesc}{Error}
796 If the current RAND method supports any errors, this is raised when needed.
797 The default method does not raise this when the entropy pool is depleted.
799 Whenever this exception is raised directly, it has a list of error messages
800 from the OpenSSL error queue, where each item is a tuple \code{(\var{lib},
801 \var{function}, \var{reason})}. Here \var{lib}, \var{function} and \var{reason}
802 are all strings, describing where and what the problem is. See \manpage{err}{3}
803 for more information.
809 \subsection{\module{SSL} --- An interface to the SSL-specific parts of OpenSSL \label{openssl-ssl}}
811 \declaremodule{extension}{SSL}
812 \modulesynopsis{An interface to the SSL-specific parts of OpenSSL}
814 This module handles things specific to SSL. There are two objects defined:
817 \begin{datadesc}{SSLv2_METHOD}
818 \dataline{SSLv3_METHOD}
819 \dataline{SSLv23_METHOD}
820 \dataline{TLSv1_METHOD}
821 These constants represent the different SSL methods to use when creating a
825 \begin{datadesc}{VERIFY_NONE}
826 \dataline{VERIFY_PEER}
827 \dataline{VERIFY_FAIL_IF_NO_PEER_CERT}
828 These constants represent the verification mode used by the Context
829 object's \method{set_verify} method.
832 \begin{datadesc}{FILETYPE_PEM}
833 \dataline{FILETYPE_ASN1}
834 File type constants used with the \method{use_certificate_file} and
835 \method{use_privatekey_file} methods of Context objects.
838 \begin{datadesc}{OP_SINGLE_DH_USE}
839 \dataline{OP_EPHEMERAL_RSA}
840 \dataline{OP_NO_SSLv2}
841 \dataline{OP_NO_SSLv3}
842 \dataline{OP_NO_TLSv1}
843 Constants used with \method{set_options} of Context objects.
844 \constant{OP_SINGLE_DH_USE} means to always create a new key when using ephemeral
845 Diffie-Hellman. \constant{OP_EPHEMERAL_RSA} means to always use ephemeral RSA keys
846 when doing RSA operations. \constant{OP_NO_SSLv2}, \constant{OP_NO_SSLv3} and
847 \constant{OP_NO_TLSv1} means to disable those specific protocols. This is
848 interesting if you're using e.g. \constant{SSLv23_METHOD} to get an SSLv2-compatible
849 handshake, but don't want to use SSLv2.
852 \begin{datadesc}{ContextType}
856 \begin{classdesc}{Context}{method}
857 A class representing SSL contexts. Contexts define the parameters of one or
858 more SSL connections.
860 \var{method} should be \constant{SSLv2_METHOD}, \constant{SSLv3_METHOD},
861 \constant{SSLv23_METHOD} or \constant{TLSv1_METHOD}.
864 \begin{datadesc}{ConnectionType}
865 See \class{Connection}.
868 \begin{classdesc}{Connection}{context, socket}
869 A class representing SSL connections.
871 \var{context} should be an instance of \class{Context} and \var{socket}
872 should be a socket \footnote{Actually, all that is required is an object
873 that \emph{behaves} like a socket, you could even use files, even though
874 it'd be tricky to get the handshakes right!} object. \var{socket} may be
875 \var{None}; in this case, the Connection is created with a memory BIO: see
876 the \method{bio_read}, \method{bio_write}, and \method{bio_shutdown}
880 \begin{excdesc}{Error}
881 This exception is used as a base class for the other SSL-related
882 exceptions, but may also be raised directly.
884 Whenever this exception is raised directly, it has a list of error messages
885 from the OpenSSL error queue, where each item is a tuple \code{(\var{lib},
886 \var{function}, \var{reason})}. Here \var{lib}, \var{function} and \var{reason}
887 are all strings, describing where and what the problem is. See \manpage{err}{3}
888 for more information.
891 \begin{excdesc}{ZeroReturnError}
892 This exception matches the error return code \code{SSL_ERROR_ZERO_RETURN}, and
893 is raised when the SSL Connection has been closed. In SSL 3.0 and TLS 1.0, this
894 only occurs if a closure alert has occurred in the protocol, i.e. the
895 connection has been closed cleanly. Note that this does not necessarily
896 mean that the transport layer (e.g. a socket) has been closed.
898 It may seem a little strange that this is an exception, but it does match an
899 \code{SSL_ERROR} code, and is very convenient.
902 \begin{excdesc}{WantReadError}
903 The operation did not complete; the same I/O method should be called again
904 later, with the same arguments. Any I/O method can lead to this since new
905 handshakes can occur at any time.
907 The wanted read is for \emph{dirty} data sent over the network, not the
908 \emph{clean} data inside the tunnel. For a socket based SSL connection,
909 \emph{read} means data coming at us over the network. Until that read
910 succeeds, the attempted \method{OpenSSL.SSL.Connection.recv},
911 \method{OpenSSL.SSL.Connection.send}, or
912 \method{OpenSSL.SSL.Connection.do_handshake} is prevented or incomplete. You
913 probably want to \method{select()} on the socket before trying again.
916 \begin{excdesc}{WantWriteError}
917 See \exception{WantReadError}. The socket send buffer may be too full to
921 \begin{excdesc}{WantX509LookupError}
922 The operation did not complete because an application callback has asked to be
923 called again. The I/O method should be called again later, with the same
924 arguments. Note: This won't occur in this version, as there are no such
925 callbacks in this version.
928 \begin{excdesc}{SysCallError}
929 The \exception{SysCallError} occurs when there's an I/O error and OpenSSL's
930 error queue does not contain any information. This can mean two things: An
931 error in the transport protocol, or an end of file that violates the protocol.
932 The parameter to the exception is always a pair \code{(\var{errnum},
937 \subsubsection{Context objects \label{openssl-context}}
939 Context objects have the following methods:
941 \begin{methoddesc}[Context]{check_privatekey}{}
942 Check if the private key (loaded with \method{use_privatekey\optional{_file}})
943 matches the certificate (loaded with \method{use_certificate\optional{_file}}).
944 Returns \code{None} if they match, raises \exception{Error} otherwise.
947 \begin{methoddesc}[Context]{get_app_data}{}
948 Retrieve application data as set by \method{set_app_data}.
951 \begin{methoddesc}[Context]{get_cert_store}{}
952 Retrieve the certificate store (a X509Store object) that the context uses.
953 This can be used to add "trusted" certificates without using the.
954 \method{load_verify_locations()} method.
957 \begin{methoddesc}[Context]{get_timeout}{}
958 Retrieve session timeout, as set by \method{set_timeout}. The default is 300
962 \begin{methoddesc}[Context]{get_verify_depth}{}
963 Retrieve the Context object's verify depth, as set by
964 \method{set_verify_depth}.
967 \begin{methoddesc}[Context]{get_verify_mode}{}
968 Retrieve the Context object's verify mode, as set by \method{set_verify}.
971 \begin{methoddesc}[Context]{load_client_ca}{pemfile}
972 Read a file with PEM-formatted certificates that will be sent to the client
973 when requesting a client certificate.
976 \begin{methoddesc}[Context]{set_client_ca_list}{certificate_authorities}
977 Replace the current list of preferred certificate signers that would be
978 sent to the client when requesting a client certificate with the
979 \var{certificate_authorities} sequence of \class{OpenSSL.crypto.X509Name}s.
984 \begin{methoddesc}[Context]{add_client_ca}{certificate_authority}
985 Extract a \class{OpenSSL.crypto.X509Name} from the \var{certificate_authority}
986 \class{OpenSSL.crypto.X509} certificate and add it to the list of preferred
987 certificate signers sent to the client when requesting a client certificate.
992 \begin{methoddesc}[Context]{load_verify_locations}{pemfile, capath}
993 Specify where CA certificates for verification purposes are located. These
994 are trusted certificates. Note that the certificates have to be in PEM
995 format. If capath is passed, it must be a directory prepared using the
996 \code{c_rehash} tool included with OpenSSL. Either, but not both, of
997 \var{pemfile} or \var{capath} may be \code{None}.
1000 \begin{methoddesc}[Context]{set_default_verify_paths}{}
1001 Specify that the platform provided CA certificates are to be used for
1002 verification purposes. This method may not work properly on OS X.
1005 \begin{methoddesc}[Context]{load_tmp_dh}{dhfile}
1006 Load parameters for Ephemeral Diffie-Hellman from \var{dhfile}.
1009 \begin{methoddesc}[Context]{set_app_data}{data}
1010 Associate \var{data} with this Context object. \var{data} can be retrieved
1011 later using the \method{get_app_data} method.
1014 \begin{methoddesc}[Context]{set_cipher_list}{ciphers}
1015 Set the list of ciphers to be used in this context. See the OpenSSL manual for
1016 more information (e.g. ciphers(1))
1019 \begin{methoddesc}[Context]{set_info_callback}{callback}
1020 Set the information callback to \var{callback}. This function will be called
1021 from time to time during SSL handshakes.
1022 \var{callback} should take three arguments: a Connection object and two
1023 integers. The first integer specifies where in the SSL handshake the function
1024 was called, and the other the return code from a (possibly failed) internal
1028 \begin{methoddesc}[Context]{set_options}{options}
1029 Add SSL options. Options you have set before are not cleared!
1030 This method should be used with the \constant{OP_*} constants.
1033 \begin{methoddesc}[Context]{set_passwd_cb}{callback\optional{, userdata}}
1034 Set the passphrase callback to \var{callback}. This function will be called
1035 when a private key with a passphrase is loaded. \var{callback} must accept
1036 three positional arguments. First, an integer giving the maximum length of
1037 the passphrase it may return. If the returned passphrase is longer than
1038 this, it will be truncated. Second, a boolean value which will be true if
1039 the user should be prompted for the passphrase twice and the callback should
1040 verify that the two values supplied are equal. Third, the value given as the
1041 \var{userdata} parameter to \method{set_passwd_cb}. If an error occurs,
1042 \var{callback} should return a false value (e.g. an empty string).
1045 \begin{methoddesc}[Context]{set_session_id}{name}
1046 Set the context \var{name} within which a session can be reused for this
1047 Context object. This is needed when doing session resumption, because there is
1048 no way for a stored session to know which Context object it is associated with.
1049 \var{name} may be any binary data.
1052 \begin{methoddesc}[Context]{set_timeout}{timeout}
1053 Set the timeout for newly created sessions for this Context object to
1054 \var{timeout}. \var{timeout} must be given in (whole) seconds. The default
1055 value is 300 seconds. See the OpenSSL manual for more information (e.g.
1056 SSL_CTX_set_timeout(3)).
1059 \begin{methoddesc}[Context]{set_verify}{mode, callback}
1060 Set the verification flags for this Context object to \var{mode} and specify
1061 that \var{callback} should be used for verification callbacks. \var{mode}
1062 should be one of \constant{VERIFY_NONE} and \constant{VERIFY_PEER}. If
1063 \constant{VERIFY_PEER} is used, \var{mode} can be OR:ed with
1064 \constant{VERIFY_FAIL_IF_NO_PEER_CERT} and \constant{VERIFY_CLIENT_ONCE} to
1065 further control the behaviour.
1066 \var{callback} should take five arguments: A Connection object, an X509 object,
1067 and three integer variables, which are in turn potential error number, error
1068 depth and return code. \var{callback} should return true if verification passes
1069 and false otherwise.
1072 \begin{methoddesc}[Context]{set_verify_depth}{depth}
1073 Set the maximum depth for the certificate chain verification that shall be
1074 allowed for this Context object.
1077 \begin{methoddesc}[Context]{use_certificate}{cert}
1078 Use the certificate \var{cert} which has to be a X509 object.
1081 \begin{methoddesc}[Context]{add_extra_chain_cert}{cert}
1082 Adds the certificate \var{cert}, which has to be a X509 object, to the
1083 certificate chain presented together with the certificate.
1086 \begin{methoddesc}[Context]{use_certificate_chain_file}{file}
1087 Load a certificate chain from \var{file} which must be PEM encoded.
1090 \begin{methoddesc}[Context]{use_privatekey}{pkey}
1091 Use the private key \var{pkey} which has to be a PKey object.
1094 \begin{methoddesc}[Context]{use_certificate_file}{file\optional{, format}}
1095 Load the first certificate found in \var{file}. The certificate must be in the
1096 format specified by \var{format}, which is either \constant{FILETYPE_PEM} or
1097 \constant{FILETYPE_ASN1}. The default is \constant{FILETYPE_PEM}.
1100 \begin{methoddesc}[Context]{use_privatekey_file}{file\optional{, format}}
1101 Load the first private key found in \var{file}. The private key must be in the
1102 format specified by \var{format}, which is either \constant{FILETYPE_PEM} or
1103 \constant{FILETYPE_ASN1}. The default is \constant{FILETYPE_PEM}.
1107 \subsubsection{Connection objects \label{openssl-connection}}
1109 Connection objects have the following methods:
1111 \begin{methoddesc}[Connection]{accept}{}
1112 Call the \method{accept} method of the underlying socket and set up SSL on the
1113 returned socket, using the Context object supplied to this Connection object at
1114 creation. Returns a pair \code{(\var{conn}, \var{address})}. where \var{conn}
1115 is the new Connection object created, and \var{address} is as returned by the
1116 socket's \method{accept}.
1119 \begin{methoddesc}[Connection]{bind}{address}
1120 Call the \method{bind} method of the underlying socket.
1123 \begin{methoddesc}[Connection]{close}{}
1124 Call the \method{close} method of the underlying socket. Note: If you want
1125 correct SSL closure, you need to call the \method{shutdown} method first.
1128 \begin{methoddesc}[Connection]{connect}{address}
1129 Call the \method{connect} method of the underlying socket and set up SSL on the
1130 socket, using the Context object supplied to this Connection object at
1134 \begin{methoddesc}[Connection]{connect_ex}{address}
1135 Call the \method{connect_ex} method of the underlying socket and set up SSL on
1136 the socket, using the Context object supplied to this Connection object at
1137 creation. Note that if the \method{connect_ex} method of the socket doesn't
1138 return 0, SSL won't be initialized.
1141 \begin{methoddesc}[Connection]{do_handshake}{}
1142 Perform an SSL handshake (usually called after \method{renegotiate} or one of
1143 \method{set_accept_state} or \method{set_accept_state}). This can raise the
1144 same exceptions as \method{send} and \method{recv}.
1147 \begin{methoddesc}[Connection]{fileno}{}
1148 Retrieve the file descriptor number for the underlying socket.
1151 \begin{methoddesc}[Connection]{listen}{backlog}
1152 Call the \method{listen} method of the underlying socket.
1155 \begin{methoddesc}[Connection]{get_app_data}{}
1156 Retrieve application data as set by \method{set_app_data}.
1159 \begin{methoddesc}[Connection]{get_cipher_list}{}
1160 Retrieve the list of ciphers used by the Connection object. WARNING: This API
1161 has changed. It used to take an optional parameter and just return a string,
1162 but not it returns the entire list in one go.
1165 \begin{methoddesc}[Connection]{get_client_ca_list}{}
1166 Retrieve the list of preferred client certificate issuers sent by the server
1167 as \class{OpenSSL.crypto.X509Name} objects.
1169 If this is a client \class{Connection}, the list will be empty until the
1170 connection with the server is established.
1172 If this is a server \class{Connection}, return the list of certificate
1173 authorities that will be sent or has been sent to the client, as controlled
1174 by this \class{Connection}'s \class{Context}.
1179 \begin{methoddesc}[Connection]{get_context}{}
1180 Retrieve the Context object associated with this Connection.
1183 \begin{methoddesc}[Connection]{get_peer_certificate}{}
1184 Retrieve the other side's certificate (if any)
1187 \begin{methoddesc}[Connection]{getpeername}{}
1188 Call the \method{getpeername} method of the underlying socket.
1191 \begin{methoddesc}[Connection]{getsockname}{}
1192 Call the \method{getsockname} method of the underlying socket.
1195 \begin{methoddesc}[Connection]{getsockopt}{level, optname\optional{, buflen}}
1196 Call the \method{getsockopt} method of the underlying socket.
1199 \begin{methoddesc}[Connection]{pending}{}
1200 Retrieve the number of bytes that can be safely read from the SSL buffer
1201 (\emph{not} the underlying transport buffer).
1204 \begin{methoddesc}[Connection]{recv}{bufsize}
1205 Receive data from the Connection. The return value is a string representing the
1206 data received. The maximum amount of data to be received at once, is specified
1210 \begin{methoddesc}[Connection]{bio_write}{bytes}
1211 If the Connection was created with a memory BIO, this method can be used to add
1212 bytes to the read end of that memory BIO. The Connection can then read the
1213 bytes (for example, in response to a call to \method{recv}).
1216 \begin{methoddesc}[Connection]{renegotiate}{}
1217 Renegotiate the SSL session. Call this if you wish to change cipher suites or
1221 \begin{methoddesc}[Connection]{send}{string}
1222 Send the \var{string} data to the Connection.
1225 \begin{methoddesc}[Connection]{bio_read}{bufsize}
1226 If the Connection was created with a memory BIO, this method can be used to
1227 read bytes from the write end of that memory BIO. Many Connection methods will
1228 add bytes which must be read in this manner or the buffer will eventually fill
1229 up and the Connection will be able to take no further actions.
1232 \begin{methoddesc}[Connection]{sendall}{string}
1233 Send all of the \var{string} data to the Connection. This calls \method{send}
1234 repeatedly until all data is sent. If an error occurs, it's impossible to tell
1235 how much data has been sent.
1238 \begin{methoddesc}[Connection]{set_accept_state}{}
1239 Set the connection to work in server mode. The handshake will be handled
1240 automatically by read/write.
1243 \begin{methoddesc}[Connection]{set_app_data}{data}
1244 Associate \var{data} with this Connection object. \var{data} can be retrieved
1245 later using the \method{get_app_data} method.
1248 \begin{methoddesc}[Connection]{set_connect_state}{}
1249 Set the connection to work in client mode. The handshake will be handled
1250 automatically by read/write.
1253 \begin{methoddesc}[Connection]{setblocking}{flag}
1254 Call the \method{setblocking} method of the underlying socket.
1257 \begin{methoddesc}[Connection]{setsockopt}{level, optname, value}
1258 Call the \method{setsockopt} method of the underlying socket.
1261 \begin{methoddesc}[Connection]{shutdown}{}
1262 Send the shutdown message to the Connection. Returns true if the shutdown
1263 message exchange is completed and false otherwise (in which case you call
1264 \method{recv()} or \method{send()} when the connection becomes
1268 \begin{methoddesc}[Connection]{get_shutdown}{}
1269 Get the shutdown state of the Connection. Returns a bitvector of either or
1270 both of \var{SENT_SHUTDOWN} and \var{RECEIVED_SHUTDOWN}.
1273 \begin{methoddesc}[Connection]{set_shutdown}{state}
1274 Set the shutdown state of the Connection. \var{state} is a bitvector of
1275 either or both of \var{SENT_SHUTDOWN} and \var{RECEIVED_SHUTDOWN}.
1278 \begin{methoddesc}[Connection]{sock_shutdown}{how}
1279 Call the \method{shutdown} method of the underlying socket.
1282 \begin{methoddesc}[Connection]{bio_shutdown}{}
1283 If the Connection was created with a memory BIO, this method can be used to
1284 indicate that ``end of file'' has been reached on the read end of that memory
1288 \begin{methoddesc}[Connection]{state_string}{}
1289 Retrieve a verbose string detailing the state of the Connection.
1292 \begin{methoddesc}[Connection]{client_random}{}
1293 Retrieve the random value used with the client hello message.
1296 \begin{methoddesc}[Connection]{server_random}{}
1297 Retrieve the random value used with the server hello message.
1300 \begin{methoddesc}[Connection]{master_key}{}
1301 Retrieve the value of the master key for this session.
1304 \begin{methoddesc}[Connection]{want_read}{}
1305 Checks if more data has to be read from the transport layer to complete an
1309 \begin{methoddesc}[Connection]{want_write}{}
1310 Checks if there is data to write to the transport layer to complete an
1316 \section{Internals \label{internals}}
1318 We ran into three main problems developing this: Exceptions, callbacks and
1319 accessing socket methods. This is what this chapter is about.
1321 \subsection{Exceptions \label{exceptions}}
1323 We realized early that most of the exceptions would be raised by the I/O
1324 functions of OpenSSL, so it felt natural to mimic OpenSSL's error code system,
1325 translating them into Python exceptions. This naturally gives us the exceptions
1326 \exception{SSL.ZeroReturnError}, \exception{SSL.WantReadError},
1327 \exception{SSL.WantWriteError}, \exception{SSL.WantX509LookupError} and
1328 \exception{SSL.SysCallError}.
1330 For more information about this, see section \ref{openssl-ssl}.
1333 \subsection{Callbacks \label{callbacks}}
1335 There are a number of problems with callbacks. First of all, OpenSSL is written
1336 as a C library, it's not meant to have Python callbacks, so a way around that
1337 is needed. Another problem is thread support. A lot of the OpenSSL I/O
1338 functions can block if the socket is in blocking mode, and then you want other
1339 Python threads to be able to do other things. The real trouble is if you've
1340 released the global CPython interpreter lock to do a potentially blocking
1341 operation, and the operation calls a callback. Then we must take the GIL back,
1342 since calling Python APIs without holding it is not allowed.
1344 There are two solutions to the first problem, both of which are necessary. The
1345 first solution to use is if the C callback allows ''userdata'' to be passed to
1346 it (an arbitrary pointer normally). This is great! We can set our Python
1347 function object as the real userdata and emulate userdata for the Python
1348 function in another way. The other solution can be used if an object with an
1349 ''app_data'' system always is passed to the callback. For example, the SSL
1350 object in OpenSSL has app_data functions and in e.g. the verification
1351 callbacks, you can retrieve the related SSL object. What we do is to set our
1352 wrapper \class{Connection} object as app_data for the SSL object, and we can
1353 easily find the Python callback.
1355 The other problem is solved using thread local variables. Whenever the GIL is
1356 released before calling into an OpenSSL API, the PyThreadState pointer returned
1357 by \cfunction{PyEval_SaveState} is stored in a global thread local variable
1358 (using Python's own TLS API, \cfunction{PyThread_set_key_value}). When it is
1359 necessary to re-acquire the GIL, either after the OpenSSL API returns or in a C
1360 callback invoked by that OpenSSL API, the value of the thread local variable is
1361 retrieved (\cfunction{PyThread_get_key_value}) and used to re-acquire the GIL.
1362 This allows Python threads to execute while OpenSSL APIs are running and allows
1363 use of any particular pyOpenSSL object from any Python thread, since there is
1364 no per-thread state associated with any of these objects and since OpenSSL is
1365 threadsafe (as long as properly initialized, as pyOpenSSL initializes it).
1368 \subsection{Acessing Socket Methods \label{socket-methods}}
1370 We quickly saw the benefit of wrapping socket methods in the
1371 \class{SSL.Connection} class, for an easy transition into using SSL. The
1372 problem here is that the \module{socket} module lacks a C API, and all the
1373 methods are declared static. One approach would be to have \module{OpenSSL} as
1374 a submodule to the \module{socket} module, placing all the code in
1375 \file{socketmodule.c}, but this is obviously not a good solution, since you
1376 might not want to import tonnes of extra stuff you're not going to use when
1377 importing the \module{socket} module. The other approach is to somehow get a
1378 pointer to the method to be called, either the C function, or a callable Python
1379 object. This is not really a good solution either, since there's a lot of
1382 The way it works is that you have to supply a ``\class{socket}-like'' transport
1383 object to the \class{SSL.Connection}. The only requirement of this object is
1384 that it has a \method{fileno()} method that returns a file descriptor that's
1385 valid at the C level (i.e. you can use the system calls read and write). If you
1386 want to use the \method{connect()} or \method{accept()} methods of the
1387 \class{SSL.Connection} object, the transport object has to supply such
1388 methods too. Apart from them, any method lookups in the \class{SSL.Connection}
1389 object that fail are passed on to the underlying transport object.
1391 Future changes might be to allow Python-level transport objects, that instead
1392 of having \method{fileno()} methods, have \method{read()} and \method{write()}
1393 methods, so more advanced features of Python can be used. This would probably
1394 entail some sort of OpenSSL ``BIOs'', but converting Python strings back and
1395 forth is expensive, so this shouldn't be used unless necessary. Other nice
1396 things would be to be able to pass in different transport objects for reading
1397 and writing, but then the \method{fileno()} method of \class{SSL.Connection}
1398 becomes virtually useless. Also, should the method resolution be used on the
1399 read-transport or the write-transport?