Welcome to pyOpenSSL’s documentation!¶
Abstract
This module is a rather thin wrapper around (a subset of) the OpenSSL library. With thin wrapper I mean that a lot of the object methods do nothing more than calling a corresponding function in the OpenSSL library.
Contents:
Introduction¶
The reason pyOpenSSL was created is that the SSL support in the socket module in Python 2.1 (the contemporary version of Python when the pyOpenSSL project was begun) was severely limited. Other OpenSSL wrappers for Python at the time were also limited, though in different ways. Unfortunately, Python’s standard library SSL support has remained weak, although other packages (such as M2Crypto) have made great advances and now equal or exceed pyOpenSSL’s functionality.
The reason pyOpenSSL continues to be maintained is that there is a significant user community around it, as well as a large amount of software which depends on it. It is a great benefit to many people for pyOpenSSL to continue to exist and advance.
OpenSSL
— Python interface to OpenSSL¶
This package provides a high-level interface to the functions in the OpenSSL library. The following modules are defined:
crypto
— Generic cryptographic module¶
-
class
OpenSSL.crypto.
X509
¶ A class representing X.509 certificates.
-
class
OpenSSL.crypto.
X509Name
(x509name)¶ A class representing X.509 Distinguished Names.
This constructor creates a copy of x509name which should be an instance of
X509Name
.
-
class
OpenSSL.crypto.
X509Req
¶ A class representing X.509 certificate requests.
-
OpenSSL.crypto.
X509StoreType
¶ See
X509Store
-
OpenSSL.crypto.
X509StoreContext
¶ A class representing the X.509 store context.
-
class
OpenSSL.crypto.
PKey
¶ A class representing DSA or RSA keys.
-
OpenSSL.crypto.
PKCS7Type
¶ A Python type object representing the PKCS7 object type.
-
OpenSSL.crypto.
PKCS12Type
¶ A Python type object representing the PKCS12 object type.
-
OpenSSL.crypto.
X509ExtensionType
¶ See
X509Extension
.
-
class
OpenSSL.crypto.
X509Extension
(typename, critical, value[, subject][, issuer])¶ A class representing an X.509 v3 certificate extensions. See http://openssl.org/docs/apps/x509v3_config.html#STANDARD_EXTENSIONS for typename strings and their options. Optional parameters subject and issuer must be X509 objects.
-
OpenSSL.crypto.
NetscapeSPKIType
¶ See
NetscapeSPKI
.
-
class
OpenSSL.crypto.
NetscapeSPKI
([enc])¶ A class representing Netscape SPKI objects.
If the enc argument is present, it should be a base64-encoded string representing a NetscapeSPKI object, as returned by the
b64_encode()
method.
-
class
OpenSSL.crypto.
CRL
¶ A class representing Certifcate Revocation List objects.
-
class
OpenSSL.crypto.
Revoked
¶ A class representing Revocation objects of CRL.
-
OpenSSL.crypto.
get_elliptic_curves
()¶ Return a set of objects representing the elliptic curves supported in the OpenSSL build in use.
The curve objects have a
unicode
name
attribute by which they identify themselves.The curve objects are useful as values for the argument accepted by
Context.set_tmp_ecdh()
to specify which elliptical curve should be used for ECDHE key exchange.
-
OpenSSL.crypto.
get_elliptic_curve
()¶ Return a single curve object selected by name.
See
get_elliptic_curves()
for information about curve objects.If the named curve is not supported then
ValueError
is raised.
-
OpenSSL.crypto.
dump_certificate
(type, cert)¶ Dump the certificate cert into a buffer string encoded with the type type.
-
OpenSSL.crypto.
dump_certificate_request
(type, req)¶ Dump the certificate request req into a buffer string encoded with the type type.
-
OpenSSL.crypto.
dump_privatekey
(type, pkey[, cipher, passphrase])¶ Dump the private key pkey into a buffer string encoded with the type type, optionally (if type is
FILETYPE_PEM
) encrypting it using cipher and passphrase.passphrase must be either a string or a callback for providing the pass phrase.
-
OpenSSL.crypto.
load_certificate
(type, buffer)¶ Load a certificate (X509) from the string buffer encoded with the type type.
-
OpenSSL.crypto.
load_certificate_request
(type, buffer)¶ Load a certificate request (X509Req) from the string buffer encoded with the type type.
-
OpenSSL.crypto.
load_privatekey
(type, buffer[, passphrase])¶ Load a private key (PKey) from the string buffer encoded with the type type (must be one of
FILETYPE_PEM
andFILETYPE_ASN1
).passphrase must be either a string or a callback for providing the pass phrase.
-
OpenSSL.crypto.
load_crl
(type, buffer)¶ Load Certificate Revocation List (CRL) data from a string buffer. buffer encoded with the type type. The type type must either
FILETYPE_PEM
orFILETYPE_ASN1
).
-
OpenSSL.crypto.
load_pkcs7_data
(type, buffer)¶ Load pkcs7 data from the string buffer encoded with the type type.
-
OpenSSL.crypto.
load_pkcs12
(buffer[, passphrase])¶ Load pkcs12 data from the string buffer. If the pkcs12 structure is encrypted, a passphrase must be included. The MAC is always checked and thus required.
See also the man page for the C function
PKCS12_parse()
.
-
OpenSSL.crypto.
sign
(key, data, digest)¶ Sign a data string using the given key and message digest.
key is a
PKey
instance. data is astr
instance. digest is astr
naming a supported message digest type, for examplesha1
.New in version 0.11.
-
OpenSSL.crypto.
verify
(certificate, signature, data, digest)¶ Verify the signature for a data string.
certificate is a
X509
instance corresponding to the private key which generated the signature. signature is a str instance giving the signature itself. data is a str instance giving the data to which the signature applies. digest is a str instance naming the message digest type of the signature, for examplesha1
.New in version 0.11.
X509 objects¶
X509 objects have the following methods:
-
X509.
get_issuer
()¶ Return an X509Name object representing the issuer of the certificate.
-
X509.
get_serial_number
()¶ Return the certificate serial number.
-
X509.
get_signature_algorithm
()¶ Return the signature algorithm used in the certificate. If the algorithm is undefined, raise
ValueError
.New in version 0.13.
-
X509.
get_version
()¶ Return the certificate version.
-
X509.
get_notBefore
()¶ Return a string giving the time before which the certificate is not valid. The string is formatted as an ASN1 GENERALIZEDTIME:
YYYYMMDDhhmmssZ YYYYMMDDhhmmss+hhmm YYYYMMDDhhmmss-hhmm
If no value exists for this field,
None
is returned.
-
X509.
get_notAfter
()¶ Return a string giving the time after which the certificate is not valid. The string is formatted as an ASN1 GENERALIZEDTIME:
YYYYMMDDhhmmssZ YYYYMMDDhhmmss+hhmm YYYYMMDDhhmmss-hhmm
If no value exists for this field,
None
is returned.
-
X509.
set_notBefore
(when)¶ Change the time before which the certificate is not valid. when is a string formatted as an ASN1 GENERALIZEDTIME:
YYYYMMDDhhmmssZ YYYYMMDDhhmmss+hhmm YYYYMMDDhhmmss-hhmm
-
X509.
set_notAfter
(when)¶ Change the time after which the certificate is not valid. when is a string formatted as an ASN1 GENERALIZEDTIME:
YYYYMMDDhhmmssZ YYYYMMDDhhmmss+hhmm YYYYMMDDhhmmss-hhmm
-
X509.
gmtime_adj_notBefore
(time)¶ Adjust the timestamp (in GMT) when the certificate starts being valid.
-
X509.
gmtime_adj_notAfter
(time)¶ Adjust the timestamp (in GMT) when the certificate stops being valid.
-
X509.
has_expired
()¶ Checks the certificate’s time stamp against current time. Returns true if the certificate has expired and false otherwise.
-
X509.
set_issuer
(issuer)¶ Set the issuer of the certificate to issuer.
-
X509.
set_pubkey
(pkey)¶ Set the public key of the certificate to pkey.
-
X509.
set_serial_number
(serialno)¶ Set the serial number of the certificate to serialno.
-
X509.
set_subject
(subject)¶ Set the subject of the certificate to subject.
-
X509.
set_version
(version)¶ Set the certificate version to version.
-
X509.
sign
(pkey, digest)¶ Sign the certificate, using the key pkey and the message digest algorithm identified by the string digest.
-
X509.
subject_name_hash
()¶ Return the hash of the certificate subject.
-
X509.
digest
(digest_name)¶ Return a digest of the certificate, using the digest_name method. digest_name must be a string describing a digest algorithm supported by OpenSSL (by EVP_get_digestbyname, specifically). For example,
"md5"
or"sha1"
.
-
X509.
add_extensions
(extensions)¶ Add the extensions in the sequence extensions to the certificate.
-
X509.
get_extension_count
()¶ Return the number of extensions on this certificate.
New in version 0.12.
-
X509.
get_extension
(index)¶ Retrieve the extension on this certificate at the given index.
Extensions on a certificate are kept in order. The index parameter selects which extension will be returned. The returned object will be an
X509Extension
instance.New in version 0.12.
X509Name objects¶
X509Name objects have the following methods:
-
X509Name.
hash
()¶ Return an integer giving the first four bytes of the MD5 digest of the DER representation of the name.
-
X509Name.
der
()¶ Return a string giving the DER representation of the name.
-
X509Name.
get_components
()¶ Return a list of two-tuples of strings giving the components of the name.
X509Name objects have the following members:
-
X509Name.
countryName
¶ The country of the entity.
C
may be used as an alias forcountryName
.
-
X509Name.
stateOrProvinceName
¶ The state or province of the entity.
ST
may be used as an alias forstateOrProvinceName
.
-
X509Name.
localityName
¶ The locality of the entity.
L
may be used as an alias forlocalityName
.
-
X509Name.
organizationName
¶ The organization name of the entity.
O
may be used as an alias fororganizationName
.
-
X509Name.
organizationalUnitName
¶ The organizational unit of the entity.
OU
may be used as an alias fororganizationalUnitName
.
-
X509Name.
commonName
¶ The common name of the entity.
CN
may be used as an alias forcommonName
.
-
X509Name.
emailAddress
¶ The e-mail address of the entity.
X509Req objects¶
X509Req objects have the following methods:
-
X509Req.
set_pubkey
(pkey)¶ Set the public key of the certificate request to pkey.
-
X509Req.
sign
(pkey, digest)¶ Sign the certificate request, using the key pkey and the message digest algorithm identified by the string digest.
-
X509Req.
verify
(pkey)¶ Verify a certificate request using the public key pkey.
-
X509Req.
set_version
(version)¶ Set the version (RFC 2459, 4.1.2.1) of the certificate request to version.
-
X509Req.
get_version
()¶ Get the version (RFC 2459, 4.1.2.1) of the certificate request.
-
X509Req.
get_extensions
()¶ Get extensions to the request.
New in version 0.15.
X509Store objects¶
The X509Store object has currently just one method:
-
X509Store.
add_cert
(cert)¶ Add the certificate cert to the certificate store.
X509StoreContextError objects¶
The X509StoreContextError is an exception raised from X509StoreContext.verify_certificate in circumstances where a certificate cannot be verified in a provided context.
The certificate for which the verification error was detected is given by the
certificate
attribute of the exception instance as a X509
instance.
Details about the verification error are given in the exception’s args
attribute.
X509StoreContext objects¶
The X509StoreContext object is used for verifying a certificate against a set of trusted certificates.
-
X509StoreContext.
verify_certificate
()¶ Verify a certificate in the context of this initialized X509StoreContext. On error, raises X509StoreContextError, otherwise does nothing.
New in version 0.15.
PKey objects¶
The PKey object has the following methods:
-
PKey.
bits
()¶ Return the number of bits of the key.
-
PKey.
generate_key
(type, bits)¶ Generate a public/private key pair of the type type (one of
TYPE_RSA
andTYPE_DSA
) with the size bits.
-
PKey.
type
()¶ Return the type of the key.
-
PKey.
check
()¶ Check the consistency of this key, returning True if it is consistent and raising an exception otherwise. This is only valid for RSA keys. See the OpenSSL RSA_check_key man page for further limitations.
PKCS7 objects¶
PKCS7 objects have the following methods:
-
PKCS7.
type_is_signed
()¶ FIXME
-
PKCS7.
type_is_enveloped
()¶ FIXME
-
PKCS7.
type_is_signedAndEnveloped
()¶ FIXME
-
PKCS7.
type_is_data
()¶ FIXME
-
PKCS7.
get_type_name
()¶ Get the type name of the PKCS7.
PKCS12 objects¶
PKCS12 objects have the following methods:
-
PKCS12.
export
([passphrase=None][, iter=2048][, maciter=1])¶ Returns a PKCS12 object as a string.
The optional passphrase must be a string not a callback.
See also the man page for the C function
PKCS12_create()
.
-
PKCS12.
get_ca_certificates
()¶ Return CA certificates within the PKCS12 object as a tuple. Returns
None
if no CA certificates are present.
-
PKCS12.
get_certificate
()¶ Return certificate portion of the PKCS12 structure.
-
PKCS12.
get_friendlyname
()¶ Return friendlyName portion of the PKCS12 structure.
-
PKCS12.
get_privatekey
()¶ Return private key portion of the PKCS12 structure
-
PKCS12.
set_ca_certificates
(cacerts)¶ Replace or set the CA certificates within the PKCS12 object with the sequence cacerts.
Set cacerts to
None
to remove all CA certificates.
-
PKCS12.
set_certificate
(cert)¶ Replace or set the certificate portion of the PKCS12 structure.
-
PKCS12.
set_friendlyname
(name)¶ Replace or set the friendlyName portion of the PKCS12 structure.
-
PKCS12.
set_privatekey
(pkey)¶ Replace or set private key portion of the PKCS12 structure
X509Extension objects¶
X509Extension objects have several methods:
-
X509Extension.
get_critical
()¶ Return the critical field of the extension object.
-
X509Extension.
get_short_name
()¶ Retrieve the short descriptive name for this extension.
The result is a byte string like
basicConstraints
.New in version 0.12.
-
X509Extension.
get_data
()¶ Retrieve the data for this extension.
The result is the ASN.1 encoded form of the extension data as a byte string.
New in version 0.12.
NetscapeSPKI objects¶
NetscapeSPKI objects have the following methods:
-
NetscapeSPKI.
b64_encode
()¶ Return a base64-encoded string representation of the object.
-
NetscapeSPKI.
get_pubkey
()¶ Return the public key of object.
-
NetscapeSPKI.
set_pubkey
(key)¶ Set the public key of the object to key.
-
NetscapeSPKI.
sign
(key, digest_name)¶ Sign the NetscapeSPKI object using the given key and digest_name. digest_name must be a string describing a digest algorithm supported by OpenSSL (by EVP_get_digestbyname, specifically). For example,
"md5"
or"sha1"
.
-
NetscapeSPKI.
verify
(key)¶ Verify the NetscapeSPKI object using the given key.
CRL objects¶
CRL objects have the following methods:
-
CRL.
add_revoked
(revoked)¶ Add a Revoked object to the CRL, by value not reference.
-
CRL.
export
(cert, key[, type=FILETYPE_PEM][, days=100][, digest=b'md5'])¶ Use cert and key to sign the CRL and return the CRL as a string. days is the number of days before the next CRL is due. digest is the algorithm that will be used to sign CRL.
-
CRL.
get_revoked
()¶ Return a tuple of Revoked objects, by value not reference.
Revoked objects¶
Revoked objects have the following methods:
-
Revoked.
all_reasons
()¶ Return a list of all supported reasons.
-
Revoked.
get_reason
()¶ Return the revocation reason as a str. Can be None, which differs from “Unspecified”.
-
Revoked.
get_rev_date
()¶ Return the revocation date as a str. The string is formatted as an ASN1 GENERALIZEDTIME.
-
Revoked.
get_serial
()¶ Return a str containing a hex number of the serial of the revoked certificate.
-
Revoked.
set_reason
(reason)¶ Set the revocation reason. reason must be None or a string, but the values are limited. Spaces and case are ignored. See
all_reasons()
.
-
Revoked.
set_rev_date
(date)¶ Set the revocation date. The string is formatted as an ASN1 GENERALIZEDTIME.
-
Revoked.
set_serial
(serial)¶ serial is a string containing a hex number of the serial of the revoked certificate.
rand
— An interface to the OpenSSL pseudo random number generator¶
This module handles the OpenSSL pseudo random number generator (PRNG) and declares the following:
-
OpenSSL.rand.
add
(string, entropy)¶ Mix bytes from string into the PRNG state. The entropy argument is (the lower bound of) an estimate of how much randomness is contained in string, measured in bytes. For more information, see e.g. RFC 1750.
-
OpenSSL.rand.
bytes
(num_bytes)¶ Get some random bytes from the PRNG as a string.
This is a wrapper for the C function
RAND_bytes()
.
-
OpenSSL.rand.
cleanup
()¶ Erase the memory used by the PRNG.
This is a wrapper for the C function
RAND_cleanup()
.
-
OpenSSL.rand.
egd
(path[, bytes])¶ Query the Entropy Gathering Daemon on socket path for bytes bytes of random data and uses
add()
to seed the PRNG. The default value of bytes is 255.
-
OpenSSL.rand.
load_file
(path[, bytes])¶ Read bytes bytes (or all of it, if bytes is negative) of data from the file path to seed the PRNG. The default value of bytes is -1.
-
OpenSSL.rand.
screen
()¶ Add the current contents of the screen to the PRNG state.
Availability: Windows.
-
OpenSSL.rand.
seed
(string)¶ This is equivalent to calling
add()
with entropy as the length of the string.
-
OpenSSL.rand.
status
()¶ Returns true if the PRNG has been seeded with enough data, and false otherwise.
-
OpenSSL.rand.
write_file
(path)¶ Write a number of random bytes (currently 1024) to the file path. This file can then be used with
load_file()
to seed the PRNG again.
-
exception
OpenSSL.rand.
Error
¶ If the current RAND method supports any errors, this is raised when needed. The default method does not raise this when the entropy pool is depleted.
Whenever this exception is raised directly, it has a list of error messages from the OpenSSL error queue, where each item is a tuple (lib, function, reason). Here lib, function and reason are all strings, describing where and what the problem is. See err(3) for more information.
SSL
— An interface to the SSL-specific parts of OpenSSL¶
This module handles things specific to SSL. There are two objects defined: Context, Connection.
-
OpenSSL.SSL.
SSLv2_METHOD
¶ -
OpenSSL.SSL.
SSLv3_METHOD
¶ -
OpenSSL.SSL.
SSLv23_METHOD
¶ -
OpenSSL.SSL.
TLSv1_METHOD
¶ -
OpenSSL.SSL.
TLSv1_1_METHOD
¶ -
OpenSSL.SSL.
TLSv1_2_METHOD
¶ These constants represent the different SSL methods to use when creating a context object. If the underlying OpenSSL build is missing support for any of these protocols, constructing a
Context
using the corresponding*_METHOD
will raise an exception.
-
OpenSSL.SSL.
VERIFY_NONE
¶ -
OpenSSL.SSL.
VERIFY_PEER
¶ -
OpenSSL.SSL.
VERIFY_FAIL_IF_NO_PEER_CERT
¶ These constants represent the verification mode used by the Context object’s
set_verify()
method.
-
OpenSSL.SSL.
FILETYPE_PEM
¶ -
OpenSSL.SSL.
FILETYPE_ASN1
¶ File type constants used with the
use_certificate_file()
anduse_privatekey_file()
methods of Context objects.
-
OpenSSL.SSL.
OP_SINGLE_DH_USE
¶ Constant used with
set_options()
of Context objects.When this option is used, a new key will always be created when using ephemeral Diffie-Hellman.
-
OpenSSL.SSL.
OP_EPHEMERAL_RSA
¶ Constant used with
set_options()
of Context objects.When this option is used, ephemeral RSA keys will always be used when doing RSA operations.
-
OpenSSL.SSL.
OP_NO_TICKET
¶ Constant used with
set_options()
of Context objects.When this option is used, the session ticket extension will not be used.
-
OpenSSL.SSL.
OP_NO_COMPRESSION
¶ Constant used with
set_options()
of Context objects.When this option is used, compression will not be used.
-
OpenSSL.SSL.
OP_NO_SSLv2
¶ -
OpenSSL.SSL.
OP_NO_SSLv3
¶ -
OpenSSL.SSL.
OP_NO_TLSv1
¶ -
OpenSSL.SSL.
OP_NO_TLSv1_1
¶ -
OpenSSL.SSL.
OP_NO_TLSv1_2
¶ Constants used with
set_options()
of Context objects.Each of these options disables one version of the SSL/TLS protocol. This is interesting if you’re using e.g.
SSLv23_METHOD
to get an SSLv2-compatible handshake, but don’t want to use SSLv2. If the underlying OpenSSL build is missing support for any of these protocols, theOP_NO_*
constant may be undefined.
-
OpenSSL.SSL.
SSLEAY_VERSION
¶ -
OpenSSL.SSL.
SSLEAY_CFLAGS
¶ -
OpenSSL.SSL.
SSLEAY_BUILT_ON
¶ -
OpenSSL.SSL.
SSLEAY_PLATFORM
¶ -
OpenSSL.SSL.
SSLEAY_DIR
¶ Constants used with
SSLeay_version()
to specify what OpenSSL version information to retrieve. See the man page for theSSLeay_version()
C API for details.
-
OpenSSL.SSL.
SESS_CACHE_OFF
¶ -
OpenSSL.SSL.
SESS_CACHE_CLIENT
¶ -
OpenSSL.SSL.
SESS_CACHE_SERVER
¶ -
OpenSSL.SSL.
SESS_CACHE_BOTH
¶ -
OpenSSL.SSL.
SESS_CACHE_NO_AUTO_CLEAR
¶ -
OpenSSL.SSL.
SESS_CACHE_NO_INTERNAL_LOOKUP
¶ -
OpenSSL.SSL.
SESS_CACHE_NO_INTERNAL_STORE
¶ -
OpenSSL.SSL.
SESS_CACHE_NO_INTERNAL
¶ Constants used with
Context.set_session_cache_mode()
to specify the behavior of the session cache and potential session reuse. See the man page for theSSL_CTX_set_session_cache_mode()
C API for details.New in version 0.14.
-
OpenSSL.SSL.
OPENSSL_VERSION_NUMBER
¶ An integer giving the version number of the OpenSSL library used to build this version of pyOpenSSL. See the man page for the
SSLeay_version()
C API for details.
-
OpenSSL.SSL.
SSLeay_version
(type)¶ Retrieve a string describing some aspect of the underlying OpenSSL version. The type passed in should be one of the
SSLEAY_*
constants defined in this module.
-
class
OpenSSL.SSL.
Context
(method)¶ A class representing SSL contexts. Contexts define the parameters of one or more SSL connections.
method should be
SSLv2_METHOD
,SSLv3_METHOD
,SSLv23_METHOD
,TLSv1_METHOD
,TLSv1_1_METHOD
, orTLSv1_2_METHOD
.
-
class
OpenSSL.SSL.
Session
¶ A class representing an SSL session. A session defines certain connection parameters which may be re-used to speed up the setup of subsequent connections.
New in version 0.14.
-
OpenSSL.SSL.
ConnectionType
¶ See
Connection
.
-
class
OpenSSL.SSL.
Connection
(context, socket)¶ A class representing SSL connections.
context should be an instance of
Context
and socket should be a socket [1] object. socket may be None; in this case, the Connection is created with a memory BIO: see thebio_read()
,bio_write()
, andbio_shutdown()
methods.
-
exception
OpenSSL.SSL.
Error
¶ This exception is used as a base class for the other SSL-related exceptions, but may also be raised directly.
Whenever this exception is raised directly, it has a list of error messages from the OpenSSL error queue, where each item is a tuple (lib, function, reason). Here lib, function and reason are all strings, describing where and what the problem is. See err(3) for more information.
-
exception
OpenSSL.SSL.
ZeroReturnError
¶ This exception matches the error return code
SSL_ERROR_ZERO_RETURN
, and is raised when the SSL Connection has been closed. In SSL 3.0 and TLS 1.0, this only occurs if a closure alert has occurred in the protocol, i.e. the connection has been closed cleanly. Note that this does not necessarily mean that the transport layer (e.g. a socket) has been closed.It may seem a little strange that this is an exception, but it does match an
SSL_ERROR
code, and is very convenient.
-
exception
OpenSSL.SSL.
WantReadError
¶ The operation did not complete; the same I/O method should be called again later, with the same arguments. Any I/O method can lead to this since new handshakes can occur at any time.
The wanted read is for dirty data sent over the network, not the clean data inside the tunnel. For a socket based SSL connection, read means data coming at us over the network. Until that read succeeds, the attempted
OpenSSL.SSL.Connection.recv()
,OpenSSL.SSL.Connection.send()
, orOpenSSL.SSL.Connection.do_handshake()
is prevented or incomplete. You probably want toselect()
on the socket before trying again.
-
exception
OpenSSL.SSL.
WantWriteError
¶ See
WantReadError
. The socket send buffer may be too full to write more data.
-
exception
OpenSSL.SSL.
WantX509LookupError
¶ The operation did not complete because an application callback has asked to be called again. The I/O method should be called again later, with the same arguments.
Note
This won’t occur in this version, as there are no such callbacks in this version.
-
exception
OpenSSL.SSL.
SysCallError
¶ The
SysCallError
occurs when there’s an I/O error and OpenSSL’s error queue does not contain any information. This can mean two things: An error in the transport protocol, or an end of file that violates the protocol. The parameter to the exception is always a pair (errnum, errstr).
Context objects¶
Context objects have the following methods:
-
Context.
check_privatekey
()¶ Check if the private key (loaded with
use_privatekey()
) matches the certificate (loaded withuse_certificate()
). ReturnsNone
if they match, raisesError
otherwise.
-
Context.
get_app_data
()¶ Retrieve application data as set by
set_app_data()
.
-
Context.
get_cert_store
()¶ Retrieve the certificate store (a X509Store object) that the context uses. This can be used to add “trusted” certificates without using the
load_verify_locations()
method.
-
Context.
get_timeout
()¶ Retrieve session timeout, as set by
set_timeout()
. The default is 300 seconds.
-
Context.
get_verify_depth
()¶ Retrieve the Context object’s verify depth, as set by
set_verify_depth()
.
-
Context.
get_verify_mode
()¶ Retrieve the Context object’s verify mode, as set by
set_verify()
.
-
Context.
load_client_ca
(pemfile)¶ Read a file with PEM-formatted certificates that will be sent to the client when requesting a client certificate.
-
Context.
set_client_ca_list
(certificate_authorities)¶ Replace the current list of preferred certificate signers that would be sent to the client when requesting a client certificate with the certificate_authorities sequence of
OpenSSL.crypto.X509Name
‘s.New in version 0.10.
-
Context.
add_client_ca
(certificate_authority)¶ Extract a
OpenSSL.crypto.X509Name
from the certificate_authorityOpenSSL.crypto.X509
certificate and add it to the list of preferred certificate signers sent to the client when requesting a client certificate.New in version 0.10.
-
Context.
load_verify_locations
(pemfile, capath)¶ Specify where CA certificates for verification purposes are located. These are trusted certificates. Note that the certificates have to be in PEM format. If capath is passed, it must be a directory prepared using the
c_rehash
tool included with OpenSSL. Either, but not both, of pemfile or capath may beNone
.
-
Context.
set_default_verify_paths
()¶ Specify that the platform provided CA certificates are to be used for verification purposes. This method may not work properly on OS X.
-
Context.
load_tmp_dh
(dhfile)¶ Load parameters for Ephemeral Diffie-Hellman from dhfile.
-
Context.
set_tmp_ecdh
(curve)¶ Select a curve to use for ECDHE key exchange.
The valid values of curve are the objects returned by
OpenSSL.crypto.get_elliptic_curves()
orOpenSSL.crypto.get_elliptic_curve()
.
-
Context.
set_app_data
(data)¶ Associate data with this Context object. data can be retrieved later using the
get_app_data()
method.
-
Context.
set_cipher_list
(ciphers)¶ Set the list of ciphers to be used in this context. See the OpenSSL manual for more information (e.g. ciphers(1))
-
Context.
set_info_callback
(callback)¶ Set the information callback to callback. This function will be called from time to time during SSL handshakes.
callback should take three arguments: a Connection object and two integers. The first integer specifies where in the SSL handshake the function was called, and the other the return code from a (possibly failed) internal function call.
-
Context.
set_options
(options)¶ Add SSL options. Options you have set before are not cleared! This method should be used with the
OP_*
constants.
-
Context.
set_mode
(mode)¶ Add SSL mode. Modes you have set before are not cleared! This method should be used with the
MODE_*
constants.
-
Context.
set_passwd_cb
(callback[, userdata])¶ Set the passphrase callback to callback. This function will be called when a private key with a passphrase is loaded. callback must accept three positional arguments. First, an integer giving the maximum length of the passphrase it may return. If the returned passphrase is longer than this, it will be truncated. Second, a boolean value which will be true if the user should be prompted for the passphrase twice and the callback should verify that the two values supplied are equal. Third, the value given as the userdata parameter to
set_passwd_cb()
. If an error occurs, callback should return a false value (e.g. an empty string).
-
Context.
set_session_cache_mode
(mode)¶ Set the behavior of the session cache used by all connections using this Context. The previously set mode is returned. See
SESS_CACHE_*
for details about particular modes.New in version 0.14.
-
Context.
get_session_cache_mode
()¶ Get the current session cache mode.
New in version 0.14.
-
Context.
set_session_id
(name)¶ Set the context name within which a session can be reused for this Context object. This is needed when doing session resumption, because there is no way for a stored session to know which Context object it is associated with. name may be any binary data.
-
Context.
set_timeout
(timeout)¶ Set the timeout for newly created sessions for this Context object to timeout. timeout must be given in (whole) seconds. The default value is 300 seconds. See the OpenSSL manual for more information (e.g. SSL_CTX_set_timeout(3)).
-
Context.
set_verify
(mode, callback)¶ Set the verification flags for this Context object to mode and specify that callback should be used for verification callbacks. mode should be one of
VERIFY_NONE
andVERIFY_PEER
. IfVERIFY_PEER
is used, mode can be OR:ed withVERIFY_FAIL_IF_NO_PEER_CERT
andVERIFY_CLIENT_ONCE
to further control the behaviour.callback should take five arguments: A Connection object, an X509 object, and three integer variables, which are in turn potential error number, error depth and return code. callback should return true if verification passes and false otherwise.
-
Context.
set_verify_depth
(depth)¶ Set the maximum depth for the certificate chain verification that shall be allowed for this Context object.
-
Context.
use_certificate
(cert)¶ Use the certificate cert which has to be a X509 object.
-
Context.
add_extra_chain_cert
(cert)¶ Adds the certificate cert, which has to be a X509 object, to the certificate chain presented together with the certificate.
-
Context.
use_certificate_chain_file
(file)¶ Load a certificate chain from file which must be PEM encoded.
-
Context.
use_privatekey
(pkey)¶ Use the private key pkey which has to be a PKey object.
-
Context.
use_certificate_file
(file[, format])¶ Load the first certificate found in file. The certificate must be in the format specified by format, which is either
FILETYPE_PEM
orFILETYPE_ASN1
. The default isFILETYPE_PEM
.
-
Context.
use_privatekey_file
(file[, format])¶ Load the first private key found in file. The private key must be in the format specified by format, which is either
FILETYPE_PEM
orFILETYPE_ASN1
. The default isFILETYPE_PEM
.
-
Context.
set_tlsext_servername_callback
(callback)¶ Specify a one-argument callable to use as the TLS extension server name callback. When a connection using the server name extension is made using this context, the callback will be invoked with the
Connection
instance.New in version 0.13.
-
Context.
set_npn_advertise_callback
(callback)¶ Specify a callback function that will be called when offering Next Protocol Negotiation as a server.
callback should be the callback function. It will be invoked with one argument, the
Connection
instance. It should return a list of bytestrings representing the advertised protocols, like[b'http/1.1', b'spdy/2']
.New in version 0.15.
-
Context.set_npn_select_callback(callback):
Specify a callback function that will be called when a server offers Next Protocol Negotiation options.
callback should be the callback function. It will be invoked with two arguments: the
Connection
, and a list of offered protocols as bytestrings, e.g.[b'http/1.1', b'spdy/2']
. It should return one of those bytestrings, the chosen protocol.New in version 0.15.
-
Context.
set_alpn_protos
(protos)¶ Specify the protocols that the client is prepared to speak after the TLS connection has been negotiated using Application Layer Protocol Negotiation.
protos should be a list of protocols that the client is offering, each as a bytestring. For example,
[b'http/1.1', b'spdy/2']
.
-
Context.
set_alpn_select_callback
(callback)¶ Specify a callback function that will be called on the server when a client offers protocols using Application Layer Protocol Negotiation.
callback should be the callback function. It will be invoked with two arguments: the
Connection
and a list of offered protocols as bytestrings, e.g.[b'http/1.1', b'spdy/2']
. It should return one of these bytestrings, the chosen protocol.
Session objects¶
Session objects have no methods.
Connection objects¶
Connection objects have the following methods:
-
Connection.
accept
()¶ Call the
accept()
method of the underlying socket and set up SSL on the returned socket, using the Context object supplied to this Connection object at creation. Returns a pair (conn, address). where conn is the new Connection object created, and address is as returned by the socket’saccept()
.
-
Connection.
close
()¶ Call the
close()
method of the underlying socket. Note: If you want correct SSL closure, you need to call theshutdown()
method first.
-
Connection.
connect
(address)¶ Call the
connect()
method of the underlying socket and set up SSL on the socket, using the Context object supplied to this Connection object at creation.
-
Connection.
connect_ex
(address)¶ Call the
connect_ex()
method of the underlying socket and set up SSL on the socket, using the Context object supplied to this Connection object at creation. Note that if theconnect_ex()
method of the socket doesn’t return 0, SSL won’t be initialized.
-
Connection.
do_handshake
()¶ Perform an SSL handshake (usually called after
renegotiate()
or one ofset_accept_state()
orset_accept_state()
). This can raise the same exceptions assend()
andrecv()
.
-
Connection.
fileno
()¶ Retrieve the file descriptor number for the underlying socket.
-
Connection.
get_app_data
()¶ Retrieve application data as set by
set_app_data()
.
-
Connection.
get_cipher_list
()¶ Retrieve the list of ciphers used by the Connection object. WARNING: This API has changed. It used to take an optional parameter and just return a string, but not it returns the entire list in one go.
-
Connection.
get_client_ca_list
()¶ Retrieve the list of preferred client certificate issuers sent by the server as
OpenSSL.crypto.X509Name
objects.If this is a client
Connection
, the list will be empty until the connection with the server is established.If this is a server
Connection
, return the list of certificate authorities that will be sent or has been sent to the client, as controlled by thisConnection
‘sContext
.New in version 0.10.
-
Connection.
get_context
()¶ Retrieve the Context object associated with this Connection.
-
Connection.
set_context
(context)¶ Specify a replacement Context object for this Connection.
-
Connection.
get_peer_certificate
()¶ Retrieve the other side’s certificate (if any)
-
Connection.
get_peer_cert_chain
()¶ Retrieve the tuple of the other side’s certificate chain (if any)
-
Connection.
getpeername
()¶ Call the
getpeername()
method of the underlying socket.
-
Connection.
getsockname
()¶ Call the
getsockname()
method of the underlying socket.
-
Connection.
getsockopt
(level, optname[, buflen])¶ Call the
getsockopt()
method of the underlying socket.
-
Connection.
pending
()¶ Retrieve the number of bytes that can be safely read from the SSL buffer (not the underlying transport buffer).
-
Connection.
recv
(bufsize)¶ Receive data from the Connection. The return value is a string representing the data received. The maximum amount of data to be received at once, is specified by bufsize.
-
Connection.
recv_into
(buffer[, nbytes[, flags]])¶ Receive data from the Connection and copy it directly into the provided buffer. The return value is the number of bytes read from the connection. The maximum amount of data to be received at once is specified by nbytes. flags is accepted for compatibility with
socket.recv_into
but its value is ignored.
-
Connection.
bio_write
(bytes)¶ If the Connection was created with a memory BIO, this method can be used to add bytes to the read end of that memory BIO. The Connection can then read the bytes (for example, in response to a call to
recv()
).
-
Connection.
renegotiate
()¶ Renegotiate the SSL session. Call this if you wish to change cipher suites or anything like that.
-
Connection.
send
(string)¶ Send the string data to the Connection.
-
Connection.
bio_read
(bufsize)¶ If the Connection was created with a memory BIO, this method can be used to read bytes from the write end of that memory BIO. Many Connection methods will add bytes which must be read in this manner or the buffer will eventually fill up and the Connection will be able to take no further actions.
-
Connection.
sendall
(string)¶ Send all of the string data to the Connection. This calls
send()
repeatedly until all data is sent. If an error occurs, it’s impossible to tell how much data has been sent.
-
Connection.
set_accept_state
()¶ Set the connection to work in server mode. The handshake will be handled automatically by read/write.
-
Connection.
set_app_data
(data)¶ Associate data with this Connection object. data can be retrieved later using the
get_app_data()
method.
-
Connection.
set_connect_state
()¶ Set the connection to work in client mode. The handshake will be handled automatically by read/write.
-
Connection.
setblocking
(flag)¶ Call the
setblocking()
method of the underlying socket.
-
Connection.
setsockopt
(level, optname, value)¶ Call the
setsockopt()
method of the underlying socket.
-
Connection.
shutdown
()¶ Send the shutdown message to the Connection. Returns true if the shutdown message exchange is completed and false otherwise (in which case you call
recv()
orsend()
when the connection becomes readable/writeable.
-
Connection.
get_shutdown
()¶ Get the shutdown state of the Connection. Returns a bitvector of either or both of SENT_SHUTDOWN and RECEIVED_SHUTDOWN.
-
Connection.
set_shutdown
(state)¶ Set the shutdown state of the Connection. state is a bitvector of either or both of SENT_SHUTDOWN and RECEIVED_SHUTDOWN.
-
Connection.
sock_shutdown
(how)¶ Call the
shutdown()
method of the underlying socket.
-
Connection.
bio_shutdown
()¶ If the Connection was created with a memory BIO, this method can be used to indicate that end of file has been reached on the read end of that memory BIO.
-
Connection.
state_string
()¶ Retrieve a verbose string detailing the state of the Connection.
-
Connection.
client_random
()¶ Retrieve the random value used with the client hello message.
-
Connection.
server_random
()¶ Retrieve the random value used with the server hello message.
-
Connection.
master_key
()¶ Retrieve the value of the master key for this session.
-
Connection.
want_read
()¶ Checks if more data has to be read from the transport layer to complete an operation.
-
Connection.
want_write
()¶ Checks if there is data to write to the transport layer to complete an operation.
-
Connection.
set_tlsext_host_name
(name)¶ Specify the byte string to send as the server name in the client hello message.
New in version 0.13.
-
Connection.
get_servername
()¶ Get the value of the server name received in the client hello message.
New in version 0.13.
-
Connection.
get_session
()¶ Get a
Session
instance representing the SSL session in use by the connection, orNone
if there is no session.New in version 0.14.
-
Connection.
set_session
(session)¶ Set a new SSL session (using a
Session
instance) to be used by the connection.New in version 0.14.
-
Connection.
get_finished
()¶ Obtain latest TLS Finished message that we sent, or
None
if handshake is not completed.New in version 0.15.
-
Connection.
get_peer_finished
()¶ Obtain latest TLS Finished message that we expected from peer, or
None
if handshake is not completed.New in version 0.15.
-
Connection.
get_cipher_name
()¶ Obtain the name of the currently used cipher.
New in version 0.15.
-
Connection.
get_cipher_bits
()¶ Obtain the number of secret bits of the currently used cipher.
New in version 0.15.
-
Connection.
get_cipher_version
()¶ Obtain the protocol name of the currently used cipher.
New in version 0.15.
-
Connection.get_next_proto_negotiated():
Get the protocol that was negotiated by Next Protocol Negotiation. Returns a bytestring of the protocol name. If no protocol has been negotiated yet, returns an empty string.
New in version 0.15.
-
Connection.
set_alpn_protos
(protos)¶ Specify the protocols that the client is prepared to speak after the TLS connection has been negotiated using Application Layer Protocol Negotiation.
protos should be a list of protocols that the client is offering, each as a bytestring. For example,
[b'http/1.1', b'spdy/2']
.
-
Connection.
get_alpn_proto_negotiated
()¶ Get the protocol that was negotiated by Application Layer Protocol Negotiation. Returns a bytestring of the protocol name. If no protocol has been negotiated yet, returns an empty string.
Footnotes
[1] | Actually, all that is required is an object that behaves like a socket, you could even use files, even though it’d be tricky to get the handshakes right! |
Internals¶
We ran into three main problems developing this: Exceptions, callbacks and accessing socket methods. This is what this chapter is about.
Exceptions¶
We realized early that most of the exceptions would be raised by the I/O
functions of OpenSSL, so it felt natural to mimic OpenSSL’s error code system,
translating them into Python exceptions. This naturally gives us the exceptions
SSL.ZeroReturnError
, SSL.WantReadError
,
SSL.WantWriteError
, SSL.WantX509LookupError
and
SSL.SysCallError
.
For more information about this, see section SSL — An interface to the SSL-specific parts of OpenSSL.
Callbacks¶
Callbacks were more of a problem when pyOpenSSL was written in C. Having switched to being written in Python using cffi, callbacks are now straightforward. The problems that originally existed no longer do (if you are interested in the details you can find descriptions of those problems in the version control history for this document).
Accessing Socket Methods¶
We quickly saw the benefit of wrapping socket methods in the
SSL.Connection
class, for an easy transition into using SSL. The
problem here is that the socket
module lacks a C API, and all the
methods are declared static. One approach would be to have OpenSSL
as
a submodule to the socket
module, placing all the code in
socketmodule.c
, but this is obviously not a good solution, since you
might not want to import tonnes of extra stuff you’re not going to use when
importing the socket
module. The other approach is to somehow get a
pointer to the method to be called, either the C function, or a callable Python
object. This is not really a good solution either, since there’s a lot of
lookups involved.
The way it works is that you have to supply a socket
- like transport
object to the SSL.Connection
. The only requirement of this object is
that it has a fileno()
method that returns a file descriptor that’s
valid at the C level (i.e. you can use the system calls read and write). If you
want to use the connect()
or accept()
methods of the
SSL.Connection
object, the transport object has to supply such
methods too. Apart from them, any method lookups in the SSL.Connection
object that fail are passed on to the underlying transport object.
Future changes might be to allow Python-level transport objects, that instead
of having fileno()
methods, have read()
and write()
methods, so more advanced features of Python can be used. This would probably
entail some sort of OpenSSL BIOs, but converting Python strings back and
forth is expensive, so this shouldn’t be used unless necessary. Other nice
things would be to be able to pass in different transport objects for reading
and writing, but then the fileno()
method of SSL.Connection
becomes virtually useless. Also, should the method resolution be used on the
read-transport or the write-transport?