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
¶ -
OpenSSL.SSL.
OP_SINGLE_ECDH_USE
¶ Constants used with
set_options()
of Context objects.When these options are used, a new key will always be created when using ephemeral (Elliptic curve) 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
(cafile)¶ Load the trusted certificates that will be sent to the client. Does not actually imply any of the certificates are trusted; that must be configured separately.
Parameters: cafile (bytes) – The path to a certificates file in PEM format. Returns: None
-
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 has some caveats related to the binary wheels that cryptography (pyOpenSSL’s primary dependency) ships:
- macOS will only load certificates using this method if the user has the
openssl@1.1
Homebrew formula installed in the default location. - Windows will not work.
- manylinux1 cryptography wheels will work on most common Linux distributions in pyOpenSSL 17.1.0 and above. pyOpenSSL detects the manylinux1 wheel and attempts to load roots via a fallback path.
- macOS will only load certificates using this method if the user has the
-
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
(cipher_list)¶ Set the list of ciphers to be used in this context.
See the OpenSSL manual for more information (e.g. ciphers(1)).
Parameters: cipher_list (bytes) – An OpenSSL cipher string. Returns: None
-
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()
. The callback must return a byte string. 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
(buf)¶ Set the session id to buf 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.
Parameters: buf (bytes) – The session id. Returns: None
-
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.
Returns: A list of native cipher strings.
-
Connection.
get_protocol_version
()¶ Retrieve the version of the SSL or TLS protocol used by the Connection. For example, it will return
0x769
for connections made over TLS version 1.
-
Connection.
get_protocol_version_name
()¶ Retrieve the version of the SSL or TLS protocol used by the Connection as a unicode string. For example, it will return
TLSv1
for connections made over TLS version 1, orUnknown
for connections that were not successfully established.
-
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[, flags])¶ 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. The only supported flag is
MSG_PEEK
, all other flags are ignored.
-
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. The only supported flag is
MSG_PEEK
, all other flags are 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 session.
Returns: True if the renegotiation can be started, False otherwise Return type: bool
-
Connection.
renegotiate_pending
()¶ Check if there’s a renegotiation in progress, it will return False once a renegotiation is finished.
Returns: Whether there’s a renegotiation in progress Return type: bool
-
Connection.
total_renegotiations
()¶ Find out the total number of renegotiations.
Returns: The number of renegotiations. Return type: int
-
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.
get_state_string
()¶ Retrieve a verbose string detailing the state of the Connection.
Returns: A string representing the state Return type: bytes
-
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! |