18.2. ssl — 套接字对象的 TLS/SSL 包裹器 ¶

18.2.1. 函数、常量及异常 ¶

exception ssl. SSLError ¶

Raised to signal an error from the underlying SSL implementation (currently provided by the OpenSSL library). This signifies some problem in the higher-level encryption and authentication layer that’s superimposed on the underlying network connection. This error is a subtype of OSError . The error code and message of SSLError instances are provided by the OpenSSL library.

3.3 版改变： SSLError used to be a subtype of socket.error .

library ¶

A string mnemonic designating the OpenSSL submodule in which the error occurred, such as SSL , PEM or X509 . The range of possible values depends on the OpenSSL version.

3.3 版新增。

reason ¶

A string mnemonic designating the reason this error occurred, for example CERTIFICATE_VERIFY_FAILED . The range of possible values depends on the OpenSSL version.

3.3 版新增。

exception ssl. SSLZeroReturnError ¶

子类化的 SSLError raised when trying to read or write and the SSL connection has been closed cleanly. Note that this doesn’t mean that the underlying transport (read TCP) has been closed.

3.3 版新增。

exception ssl. SSLWantReadError ¶

子类化的 SSLError raised by a non-blocking SSL socket when trying to read or write data, but more data needs to be received on the underlying TCP transport before the request can be fulfilled.

3.3 版新增。

exception ssl. SSLWantWriteError ¶

子类化的 SSLError raised by a non-blocking SSL socket when trying to read or write data, but more data needs to be sent on the underlying TCP transport before the request can be fulfilled.

3.3 版新增。

exception ssl. SSLSyscallError ¶

子类化的 SSLError raised when a system error was encountered while trying to fulfill an operation on a SSL socket. Unfortunately, there is no easy way to inspect the original errno number.

3.3 版新增。

exception ssl. SSLEOFError ¶

子类化的 SSLError raised when the SSL connection has been terminated abruptly. Generally, you shouldn’t try to reuse the underlying transport when this error is encountered.

3.3 版新增。

exception ssl. CertificateError ¶

Raised to signal an error with a certificate (such as mismatching hostname). Certificate errors detected by OpenSSL, though, raise an SSLError .

18.2.2. SSL 套接字 ¶

class ssl. SSLSocket ( socket.socket ) ¶

SSL sockets provide the following methods of Socket Objects :

• accept()
• bind()
• close()
• connect()
• detach()
• fileno()
• getpeername() , getsockname()
• getsockopt() , setsockopt()
• gettimeout() , settimeout() , setblocking()
• listen()
• makefile()
• recv() , recv_into() (but passing a non-zero flags argument is not allowed)
• send() , sendall() (with the same limitation)
• sendfile() (but os.sendfile will be used for plain-text sockets only, else send() will be used)
• shutdown()

However, since the SSL (and TLS) protocol has its own framing atop of TCP, the SSL sockets abstraction can, in certain respects, diverge from the specification of normal, OS-level sockets. See especially the notes on non-blocking sockets .

Usually, SSLSocket are not created directly, but using the SSLContext.wrap_socket() 方法。

3.5 版改变： sendfile() 方法被添加。

3.5 版改变： shutdown() does not reset the socket timeout each time bytes are received or sent. The socket timeout is now to maximum total duration of the shutdown.

从 3.6 版起弃用： It is deprecated to create a SSLSocket instance directly, use SSLContext.wrap_socket() to wrap a socket.

SSL sockets also have the following additional methods and attributes:

SSLSocket. read ( len=1024 , buffer=None ) ¶

Read up to len bytes of data from the SSL socket and return the result as a bytes instance. If buffer is specified, then read into the buffer instead, and return the number of bytes read.

引发 SSLWantReadError or SSLWantWriteError if the socket is non-blocking and the read would block.

As at any time a re-negotiation is possible, a call to read() can also cause write operations.

3.5 版改变： The socket timeout is no more reset each time bytes are received or sent. The socket timeout is now to maximum total duration to read up to len 字节。

从 3.6 版起弃用： 使用 recv() 而不是 read() .

SSLSocket. write ( buf ) ¶

Write buf to the SSL socket and return the number of bytes written. The buf argument must be an object supporting the buffer interface.

引发 SSLWantReadError or SSLWantWriteError if the socket is non-blocking and the write would block.

As at any time a re-negotiation is possible, a call to write() can also cause read operations.

3.5 版改变： The socket timeout is no more reset each time bytes are received or sent. The socket timeout is now to maximum total duration to write buf .

从 3.6 版起弃用： 使用 send() 而不是 write() .

SSLSocket. do_handshake ( ) ¶

Perform the SSL setup handshake.

3.4 版改变： The handshake method also performs match_hostname() when the check_hostname attribute of the socket’s context 为 true。

3.5 版改变： The socket timeout is no more reset each time bytes are received or sent. The socket timeout is now to maximum total duration of the handshake.

SSLSocket. getpeercert ( binary_form=False ) ¶

If there is no certificate for the peer on the other end of the connection, return None . If the SSL handshake hasn’t been done yet, raise ValueError .

若 binary_form 参数为 False , and a certificate was received from the peer, this method returns a dict instance. If the certificate was not validated, the dict is empty. If the certificate was validated, it returns a dict with several keys, amongst them subject (the principal for which the certificate was issued) and issuer (the principal issuing the certificate). If a certificate contains an instance of the Subject Alternative Name 扩展 (见 RFC 3280 ), there will also be a subjectAltName key in the dictionary.

subject and issuer fields are tuples containing the sequence of relative distinguished names (RDNs) given in the certificate’s data structure for the respective fields, and each RDN is a sequence of name-value pairs. Here is a real-world example:

{'issuer': ((('countryName', 'IL'),),
            (('organizationName', 'StartCom Ltd.'),),
            (('organizationalUnitName',
              'Secure Digital Certificate Signing'),),
            (('commonName',
              'StartCom Class 2 Primary Intermediate Server CA'),)),
 'notAfter': 'Nov 22 08:15:19 2013 GMT',
 'notBefore': 'Nov 21 03:09:52 2011 GMT',
 'serialNumber': '95F0',
 'subject': ((('description', '571208-SLe257oHY9fVQ07Z'),),
             (('countryName', 'US'),),
             (('stateOrProvinceName', 'California'),),
             (('localityName', 'San Francisco'),),
             (('organizationName', 'Electronic Frontier Foundation, Inc.'),),
             (('commonName', '*.eff.org'),),
             (('emailAddress', 'hostmaster@eff.org'),)),
 'subjectAltName': (('DNS', '*.eff.org'), ('DNS', 'eff.org')),
 'version': 3}
										

注意

To validate a certificate for a particular service, you can use the match_hostname() 函数。

若 binary_form 参数为 True , and a certificate was provided, this method returns the DER-encoded form of the entire certificate as a sequence of bytes, or None if the peer did not provide a certificate. Whether the peer provides a certificate depends on the SSL socket’s role:

• for a client SSL socket, the server will always provide a certificate, regardless of whether validation was required;
• for a server SSL socket, the client will only provide a certificate when requested by the server; therefore getpeercert() will return None if you used CERT_NONE (rather than CERT_OPTIONAL or CERT_REQUIRED ).

3.2 版改变： The returned dictionary includes additional items such as issuer and notBefore .

3.4 版改变： ValueError is raised when the handshake isn’t done. The returned dictionary includes additional X509v3 extension items such as crlDistributionPoints , caIssuers and OCSP URIs.

SSLSocket. cipher ( ) ¶

Returns a three-value tuple containing the name of the cipher being used, the version of the SSL protocol that defines its use, and the number of secret bits being used. If no connection has been established, returns None .

SSLSocket. shared_ciphers ( ) ¶

Return the list of ciphers shared by the client during the handshake. Each entry of the returned list is a three-value tuple containing the name of the cipher, the version of the SSL protocol that defines its use, and the number of secret bits the cipher uses. shared_ciphers() 返回 None if no connection has been established or the socket is a client socket.

3.5 版新增。

SSLSocket. 压缩 ( ) ¶

Return the compression algorithm being used as a string, or None if the connection isn’t compressed.

If the higher-level protocol supports its own compression mechanism, you can use OP_NO_COMPRESSION to disable SSL-level compression.

3.3 版新增。

SSLSocket. get_channel_binding ( cb_type="tls-unique" ) ¶

Get channel binding data for current connection, as a bytes object. Returns None if not connected or the handshake has not been completed.

cb_type parameter allow selection of the desired channel binding type. Valid channel binding types are listed in the CHANNEL_BINDING_TYPES list. Currently only the ‘tls-unique’ channel binding, defined by RFC 5929 , is supported. ValueError will be raised if an unsupported channel binding type is requested.

3.3 版新增。

SSLSocket. selected_alpn_protocol ( ) ¶

Return the protocol that was selected during the TLS handshake. If SSLContext.set_alpn_protocols() was not called, if the other party does not support ALPN, if this socket does not support any of the client’s proposed protocols, or if the handshake has not happened yet, None 被返回。

3.5 版新增。

SSLSocket. selected_npn_protocol ( ) ¶

Return the higher-level protocol that was selected during the TLS/SSL handshake. If SSLContext.set_npn_protocols() was not called, or if the other party does not support NPN, or if the handshake has not yet happened, this will return None .

3.3 版新增。

SSLSocket. unwrap ( ) ¶

Performs the SSL shutdown handshake, which removes the TLS layer from the underlying socket, and returns the underlying socket object. This can be used to go from encrypted operation over a connection to unencrypted. The returned socket should always be used for further communication with the other side of the connection, rather than the original socket.

SSLSocket. verify_client_post_handshake ( ) ¶

Requests post-handshake authentication (PHA) from a TLS 1.3 client. PHA can only be initiated for a TLS 1.3 connection from a server-side socket, after the initial TLS handshake and with PHA enabled on both sides, see SSLContext.post_handshake_auth .

The method does not perform a cert exchange immediately. The server-side sends a CertificateRequest during the next write event and expects the client to respond with a certificate on the next read event.

If any precondition isn’t met (e.g. not TLS 1.3, PHA not enabled), an SSLError 被引发。

New in version 3.6.7.

注意

Only available with OpenSSL 1.1.1 and TLS 1.3 enabled. Without TLS 1.3 support, the method raises NotImplementedError .

SSLSocket. version ( ) ¶

Return the actual SSL protocol version negotiated by the connection as a string, or None is no secure connection is established. As of this writing, possible return values include "SSLv2" , "SSLv3" , "TLSv1" , "TLSv1.1" and "TLSv1.2" . Recent OpenSSL versions may define more return values.

3.5 版新增。

SSLSocket. pending ( ) ¶

Returns the number of already decrypted bytes available for read, pending on the connection.

SSLSocket. context ¶

SSLContext object this SSL socket is tied to. If the SSL socket was created using the top-level wrap_socket() function (rather than SSLContext.wrap_socket() ), this is a custom context object created for this SSL socket.

3.2 版新增。

SSLSocket. server_side ¶

A boolean which is True for server-side sockets and False for client-side sockets.

3.2 版新增。

SSLSocket. server_hostname ¶

Hostname of the server: str type, or None for server-side socket or if the hostname was not specified in the constructor.

3.2 版新增。

SSLSocket. session ¶

SSLSession for this SSL connection. The session is available for client and server side sockets after the TLS handshake has been performed. For client sockets the session can be set before do_handshake() has been called to reuse a session.

3.6 版新增。

SSLSocket. session_reused ¶

3.6 版新增。

18.2.3. SSL 上下文 ¶

An SSL context holds various data longer-lived than single SSL connections, such as SSL configuration options, certificate(s) and private key(s). It also manages a cache of SSL sessions for server-side sockets, in order to speed up repeated connections from the same clients.

class ssl. SSLContext ( protocol=PROTOCOL_TLS ) ¶

Create a new SSL context. You may pass protocol which must be one of the PROTOCOL_* constants defined in this module. PROTOCOL_TLS is currently recommended for maximum interoperability and default value.

另请参阅

create_default_context() lets the ssl module choose security settings for a given purpose.

3.6 版改变： The context is created with secure default values. The options OP_NO_COMPRESSION , OP_CIPHER_SERVER_PREFERENCE , OP_SINGLE_DH_USE , OP_SINGLE_ECDH_USE , OP_NO_SSLv2 (except for PROTOCOL_SSLv2 ), and OP_NO_SSLv3 (except for PROTOCOL_SSLv3 ) are set by default. The initial cipher suite list contains only HIGH ciphers, no NULL ciphers and no MD5 ciphers (except for PROTOCOL_SSLv2 ).

SSLContext objects have the following methods and attributes:

SSLContext. cert_store_stats ( ) ¶

Get statistics about quantities of loaded X.509 certificates, count of X.509 certificates flagged as CA certificates and certificate revocation lists as dictionary.

Example for a context with one CA cert and one other cert:

>>> context.cert_store_stats()
{'crl': 0, 'x509_ca': 1, 'x509': 2}
										

3.4 版新增。

SSLContext. load_cert_chain ( certfile , keyfile=None , password=None ) ¶

Load a private key and the corresponding certificate. The certfile string must be the path to a single file in PEM format containing the certificate as well as any number of CA certificates needed to establish the certificate’s authenticity. The keyfile string, if present, must point to a file containing the private key in. Otherwise the private key will be taken from certfile as well. See the discussion of Certificates for more information on how the certificate is stored in the certfile .

password argument may be a function to call to get the password for decrypting the private key. It will only be called if the private key is encrypted and a password is necessary. It will be called with no arguments, and it should return a string, bytes, or bytearray. If the return value is a string it will be encoded as UTF-8 before using it to decrypt the key. Alternatively a string, bytes, or bytearray value may be supplied directly as the password argument. It will be ignored if the private key is not encrypted and no password is needed.

若 password argument is not specified and a password is required, OpenSSL’s built-in password prompting mechanism will be used to interactively prompt the user for a password.

An SSLError is raised if the private key doesn’t match with the certificate.

3.3 版改变： New optional argument password .

SSLContext. load_default_certs ( purpose=Purpose.SERVER_AUTH ) ¶

Load a set of default “certification authority” (CA) certificates from default locations. On Windows it loads CA certs from the CA and ROOT system stores. On other systems it calls SSLContext.set_default_verify_paths() . In the future the method may load CA certificates from other locations, too.

purpose flag specifies what kind of CA certificates are loaded. The default settings Purpose.SERVER_AUTH loads certificates, that are flagged and trusted for TLS web server authentication (client side sockets). Purpose.CLIENT_AUTH loads CA certificates for client certificate verification on the server side.

3.4 版新增。

SSLContext. load_verify_locations ( cafile=None , capath=None , cadata=None ) ¶

Load a set of “certification authority” (CA) certificates used to validate other peers’ certificates when verify_mode is other than CERT_NONE . At least one of cafile or capath 必须指定。

This method can also load certification revocation lists (CRLs) in PEM or DER format. In order to make use of CRLs, SSLContext.verify_flags must be configured properly.

cafile string, if present, is the path to a file of concatenated CA certificates in PEM format. See the discussion of Certificates for more information about how to arrange the certificates in this file.

capath string, if present, is the path to a directory containing several CA certificates in PEM format, following an OpenSSL specific layout .

cadata object, if present, is either an ASCII string of one or more PEM-encoded certificates or a 像字节对象 of DER-encoded certificates. Like with capath extra lines around PEM-encoded certificates are ignored but at least one certificate must be present.

3.4 版改变： New optional argument cadata

SSLContext. get_ca_certs ( binary_form=False ) ¶

Get a list of loaded “certification authority” (CA) certificates. If the binary_form 参数为 False each list entry is a dict like the output of SSLSocket.getpeercert() . Otherwise the method returns a list of DER-encoded certificates. The returned list does not contain certificates from capath unless a certificate was requested and loaded by a SSL connection.

注意

Certificates in a capath directory aren’t loaded unless they have been used at least once.

3.4 版新增。

SSLContext. get_ciphers ( ) ¶

Get a list of enabled ciphers. The list is in order of cipher priority. See SSLContext.set_ciphers() .

范例：

>>> ctx = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
>>> ctx.set_ciphers('ECDHE+AESGCM:!ECDSA')
>>> ctx.get_ciphers()  # OpenSSL 1.0.x
[{'alg_bits': 256,
  'description': 'ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  '
                 'Enc=AESGCM(256) Mac=AEAD',
  'id': 50380848,
  'name': 'ECDHE-RSA-AES256-GCM-SHA384',
  'protocol': 'TLSv1/SSLv3',
  'strength_bits': 256},
 {'alg_bits': 128,
  'description': 'ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  '
                 'Enc=AESGCM(128) Mac=AEAD',
  'id': 50380847,
  'name': 'ECDHE-RSA-AES128-GCM-SHA256',
  'protocol': 'TLSv1/SSLv3',
  'strength_bits': 128}]
										

On OpenSSL 1.1 and newer the cipher dict contains additional fields::

>>> ctx.get_ciphers()  # OpenSSL 1.1+
[{'aead': True,
  'alg_bits': 256,
  'auth': 'auth-rsa',
  'description': 'ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  '
                 'Enc=AESGCM(256) Mac=AEAD',
  'digest': None,
  'id': 50380848,
  'kea': 'kx-ecdhe',
  'name': 'ECDHE-RSA-AES256-GCM-SHA384',
  'protocol': 'TLSv1.2',
  'strength_bits': 256,
  'symmetric': 'aes-256-gcm'},
 {'aead': True,
  'alg_bits': 128,
  'auth': 'auth-rsa',
  'description': 'ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  '
                 'Enc=AESGCM(128) Mac=AEAD',
  'digest': None,
  'id': 50380847,
  'kea': 'kx-ecdhe',
  'name': 'ECDHE-RSA-AES128-GCM-SHA256',
  'protocol': 'TLSv1.2',
  'strength_bits': 128,
  'symmetric': 'aes-128-gcm'}]
												

Availability: OpenSSL 1.0.2+

3.6 版新增。

SSLContext. set_default_verify_paths ( ) ¶

Load a set of default “certification authority” (CA) certificates from a filesystem path defined when building the OpenSSL library. Unfortunately, there’s no easy way to know whether this method succeeds: no error is returned if no certificates are to be found. When the OpenSSL library is provided as part of the operating system, though, it is likely to be configured properly.

SSLContext. set_ciphers ( ciphers ) ¶

Set the available ciphers for sockets created with this context. It should be a string in the OpenSSL cipher list format . If no cipher can be selected (because compile-time options or other configuration forbids use of all the specified ciphers), an SSLError 会被引发。

注意

when connected, the SSLSocket.cipher() method of SSL sockets will give the currently selected cipher.

OpenSSL 1.1.1 has TLS 1.3 cipher suites enabled by default. The suites cannot be disabled with set_ciphers() .

SSLContext. set_alpn_protocols ( protocols ) ¶

Specify which protocols the socket should advertise during the SSL/TLS handshake. It should be a list of ASCII strings, like ['http/1.1', 'spdy/2'] , ordered by preference. The selection of a protocol will happen during the handshake, and will play out according to RFC 7301 . After a successful handshake, the SSLSocket.selected_alpn_protocol() method will return the agreed-upon protocol.

This method will raise NotImplementedError if HAS_ALPN is False.

OpenSSL 1.1.0 to 1.1.0e will abort the handshake and raise SSLError when both sides support ALPN but cannot agree on a protocol. 1.1.0f+ behaves like 1.0.2, SSLSocket.selected_alpn_protocol() returns None.

3.5 版新增。

SSLContext. set_npn_protocols ( protocols ) ¶

Specify which protocols the socket should advertise during the SSL/TLS handshake. It should be a list of strings, like ['http/1.1', 'spdy/2'] , ordered by preference. The selection of a protocol will happen during the handshake, and will play out according to the NPN draft specification . After a successful handshake, the SSLSocket.selected_npn_protocol() method will return the agreed-upon protocol.

This method will raise NotImplementedError if HAS_NPN is False.

3.3 版新增。

SSLContext. set_servername_callback ( server_name_callback ) ¶

Register a callback function that will be called after the TLS Client Hello handshake message has been received by the SSL/TLS server when the TLS client specifies a server name indication. The server name indication mechanism is specified in RFC 6066 section 3 - Server Name Indication.

Only one callback can be set per SSLContext 。若 server_name_callback is None then the callback is disabled. Calling this function a subsequent time will disable the previously registered callback.

The callback function, server_name_callback , will be called with three arguments; the first being the ssl.SSLSocket , the second is a string that represents the server name that the client is intending to communicate (or None if the TLS Client Hello does not contain a server name) and the third argument is the original SSLContext . The server name argument is the IDNA decoded server name.

A typical use of this callback is to change the ssl.SSLSocket ’s SSLSocket.context attribute to a new object of type SSLContext representing a certificate chain that matches the server name.

Due to the early negotiation phase of the TLS connection, only limited methods and attributes are usable like SSLSocket.selected_alpn_protocol() and SSLSocket.context . SSLSocket.getpeercert() , SSLSocket.getpeercert() , SSLSocket.cipher() and SSLSocket.compress() methods require that the TLS connection has progressed beyond the TLS Client Hello and therefore will not contain return meaningful values nor can they be called safely.

server_name_callback function must return None to allow the TLS negotiation to continue. If a TLS failure is required, a constant ALERT_DESCRIPTION_* can be returned. Other return values will result in a TLS fatal error with ALERT_DESCRIPTION_INTERNAL_ERROR .

If there is an IDNA decoding error on the server name, the TLS connection will terminate with an ALERT_DESCRIPTION_INTERNAL_ERROR fatal TLS alert message to the client.

If an exception is raised from the server_name_callback function the TLS connection will terminate with a fatal TLS alert message ALERT_DESCRIPTION_HANDSHAKE_FAILURE .

This method will raise NotImplementedError if the OpenSSL library had OPENSSL_NO_TLSEXT defined when it was built.

3.4 版新增。

SSLContext. load_dh_params ( dhfile ) ¶

Load the key generation parameters for Diffie-Hellman (DH) key exchange. Using DH key exchange improves forward secrecy at the expense of computational resources (both on the server and on the client). dhfile parameter should be the path to a file containing DH parameters in PEM format.

This setting doesn’t apply to client sockets. You can also use the OP_SINGLE_DH_USE option to further improve security.

3.3 版新增。

SSLContext. set_ecdh_curve ( curve_name ) ¶

Set the curve name for Elliptic Curve-based Diffie-Hellman (ECDH) key exchange. ECDH is significantly faster than regular DH while arguably as secure. The curve_name parameter should be a string describing a well-known elliptic curve, for example prime256v1 for a widely supported curve.

This setting doesn’t apply to client sockets. You can also use the OP_SINGLE_ECDH_USE option to further improve security.

This method is not available if HAS_ECDH is False .

3.3 版新增。

另请参阅

SSL/TLS & Perfect Forward Secrecy

Vincent Bernat.

SSLContext. wrap_socket ( sock , server_side=False , do_handshake_on_connect=True , suppress_ragged_eofs=True , server_hostname=None , session=None ) ¶

Wrap an existing Python socket sock and return an SSLSocket 对象。 sock 必须是 SOCK_STREAM socket; other socket types are unsupported.

The returned SSL socket is tied to the context, its settings and certificates. The parameters server_side , do_handshake_on_connect and suppress_ragged_eofs have the same meaning as in the top-level wrap_socket() 函数。

On client connections, the optional parameter server_hostname specifies the hostname of the service which we are connecting to. This allows a single server to host multiple SSL-based services with distinct certificates, quite similarly to HTTP virtual hosts. Specifying server_hostname will raise a ValueError if server_side 为 true。

session ，见 session .

3.5 版改变： Always allow a server_hostname to be passed, even if OpenSSL does not have SNI.

3.6 版改变： session argument was added.

SSLContext. wrap_bio ( incoming , outgoing , server_side=False , server_hostname=None , session=None ) ¶

创建新的 SSLObject instance by wrapping the BIO objects incoming and outgoing . The SSL routines will read input data from the incoming BIO and write data to the outgoing BIO.

server_side , server_hostname and session parameters have the same meaning as in SSLContext.wrap_socket() .

3.6 版改变： session argument was added.

SSLContext. session_stats ( ) ¶

Get statistics about the SSL sessions created or managed by this context. A dictionary is returned which maps the names of each piece of information to their numeric values. For example, here is the total number of hits and misses in the session cache since the context was created:

>>> stats = context.session_stats()
>>> stats['hits'], stats['misses']
(0, 0)
										

SSLContext. check_hostname ¶

Whether to match the peer cert’s hostname with match_hostname() in SSLSocket.do_handshake() . The context’s verify_mode must be set to CERT_OPTIONAL or CERT_REQUIRED , and you must pass server_hostname to wrap_socket() in order to match the hostname.

范例：

import socket, ssl
context = ssl.SSLContext()
context.verify_mode = ssl.CERT_REQUIRED
context.check_hostname = True
context.load_default_certs()
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
ssl_sock = context.wrap_socket(s, server_hostname='www.verisign.com')
ssl_sock.connect(('www.verisign.com', 443))
										

3.4 版新增。

注意

This features requires OpenSSL 0.9.8f or newer.

SSLContext. 选项 ¶

An integer representing the set of SSL options enabled on this context. The default value is OP_ALL , but you can specify other options such as OP_NO_SSLv2 by ORing them together.

注意

With versions of OpenSSL older than 0.9.8m, it is only possible to set options, not to clear them. Attempting to clear an option (by resetting the corresponding bits) will raise a ValueError .

3.6 版改变： SSLContext.options 返回 Options flags:

>>> ssl.create_default_context().options
<Options.OP_ALL|OP_NO_SSLv3|OP_NO_SSLv2|OP_NO_COMPRESSION: 2197947391>
											

SSLContext. post_handshake_auth ¶

Enable TLS 1.3 post-handshake client authentication. Post-handshake auth is disabled by default and a server can only request a TLS client certificate during the initial handshake. When enabled, a server may request a TLS client certificate at any time after the handshake.

When enabled on client-side sockets, the client signals the server that it supports post-handshake authentication.

When enabled on server-side sockets, SSLContext.verify_mode must be set to CERT_OPTIONAL or CERT_REQUIRED , too. The actual client cert exchange is delayed until SSLSocket.verify_client_post_handshake() is called and some I/O is performed.

New in version 3.6.7.

注意

Only available with OpenSSL 1.1.1 and TLS 1.3 enabled. Without TLS 1.3 support, the property value is None and can’t be modified

SSLContext. protocol ¶

The protocol version chosen when constructing the context. This attribute is read-only.

SSLContext. verify_flags ¶

The flags for certificate verification operations. You can set flags like VERIFY_CRL_CHECK_LEAF by ORing them together. By default OpenSSL does neither require nor verify certificate revocation lists (CRLs). Available only with openssl version 0.9.8+.

3.4 版新增。

3.6 版改变： SSLContext.verify_flags 返回 VerifyFlags flags:

>>> ssl.create_default_context().verify_flags
<VerifyFlags.VERIFY_X509_TRUSTED_FIRST: 32768>
											

SSLContext. verify_mode ¶

Whether to try to verify other peers’ certificates and how to behave if verification fails. This attribute must be one of CERT_NONE , CERT_OPTIONAL or CERT_REQUIRED .

3.6 版改变： SSLContext.verify_mode 返回 VerifyMode enum:

>>> ssl.create_default_context().verify_mode
<VerifyMode.CERT_REQUIRED: 2>
											

18.2.4. 证书 ¶

Certificates in general are part of a public-key / private-key system. In this system, each principal , (which may be a machine, or a person, or an organization) is assigned a unique two-part encryption key. One part of the key is public, and is called the public key ; the other part is kept secret, and is called the private key . The two parts are related, in that if you encrypt a message with one of the parts, you can decrypt it with the other part, and only with the other part.

A certificate contains information about two principals. It contains the name of a subject , and the subject’s public key. It also contains a statement by a second principal, the issuer , that the subject is who they claim to be, and that this is indeed the subject’s public key. The issuer’s statement is signed with the issuer’s private key, which only the issuer knows. However, anyone can verify the issuer’s statement by finding the issuer’s public key, decrypting the statement with it, and comparing it to the other information in the certificate. The certificate also contains information about the time period over which it is valid. This is expressed as two fields, called “notBefore” and “notAfter”.

In the Python use of certificates, a client or server can use a certificate to prove who they are. The other side of a network connection can also be required to produce a certificate, and that certificate can be validated to the satisfaction of the client or server that requires such validation. The connection attempt can be set to raise an exception if the validation fails. Validation is done automatically, by the underlying OpenSSL framework; the application need not concern itself with its mechanics. But the application does usually need to provide sets of certificates to allow this process to take place.

Python uses files to contain certificates. They should be formatted as “PEM” (see RFC 1422 ), which is a base-64 encoded form wrapped with a header line and a footer line:

-----BEGIN CERTIFICATE-----
... (certificate in base64 PEM encoding) ...
-----END CERTIFICATE-----
								

-----BEGIN CERTIFICATE-----
... (certificate for your server)...
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
... (the certificate for the CA)...
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
... (the root certificate for the CA's issuer)...
-----END CERTIFICATE-----
									

-----BEGIN RSA PRIVATE KEY-----
... (private key in base64 encoding) ...
-----END RSA PRIVATE KEY-----
-----BEGIN CERTIFICATE-----
... (certificate in base64 PEM encoding) ...
-----END CERTIFICATE-----
									

% openssl req -new -x509 -days 365 -nodes -out cert.pem -keyout cert.pem
Generating a 1024 bit RSA private key
.......++++++
.............................++++++
writing new private key to 'cert.pem'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:MyState
Locality Name (eg, city) []:Some City
Organization Name (eg, company) [Internet Widgits Pty Ltd]:My Organization, Inc.
Organizational Unit Name (eg, section) []:My Group
Common Name (eg, YOUR name) []:myserver.mygroup.myorganization.com
Email Address []:ops@myserver.mygroup.myorganization.com
%
									

18.2.5. 范例 ¶

try:
    import ssl
except ImportError:
    pass
else:
    ...  # do something that requires SSL support
									

>>> context = ssl.create_default_context()
									

>>> context = ssl.SSLContext()
>>> context.verify_mode = ssl.CERT_REQUIRED
>>> context.check_hostname = True
>>> context.load_verify_locations("/etc/ssl/certs/ca-bundle.crt")
									

>>> conn = context.wrap_socket(socket.socket(socket.AF_INET),
...                            server_hostname="www.python.org")
>>> conn.connect(("www.python.org", 443))
									

>>> cert = conn.getpeercert()
									

>>> pprint.pprint(cert)
{'OCSP': ('http://ocsp.digicert.com',),
 'caIssuers': ('http://cacerts.digicert.com/DigiCertSHA2ExtendedValidationServerCA.crt',),
 'crlDistributionPoints': ('http://crl3.digicert.com/sha2-ev-server-g1.crl',
                           'http://crl4.digicert.com/sha2-ev-server-g1.crl'),
 'issuer': ((('countryName', 'US'),),
            (('organizationName', 'DigiCert Inc'),),
            (('organizationalUnitName', 'www.digicert.com'),),
            (('commonName', 'DigiCert SHA2 Extended Validation Server CA'),)),
 'notAfter': 'Sep  9 12:00:00 2016 GMT',
 'notBefore': 'Sep  5 00:00:00 2014 GMT',
 'serialNumber': '01BB6F00122B177F36CAB49CEA8B6B26',
 'subject': ((('businessCategory', 'Private Organization'),),
             (('1.3.6.1.4.1.311.60.2.1.3', 'US'),),
             (('1.3.6.1.4.1.311.60.2.1.2', 'Delaware'),),
             (('serialNumber', '3359300'),),
             (('streetAddress', '16 Allen Rd'),),
             (('postalCode', '03894-4801'),),
             (('countryName', 'US'),),
             (('stateOrProvinceName', 'NH'),),
             (('localityName', 'Wolfeboro,'),),
             (('organizationName', 'Python Software Foundation'),),
             (('commonName', 'www.python.org'),)),
 'subjectAltName': (('DNS', 'www.python.org'),
                    ('DNS', 'python.org'),
                    ('DNS', 'pypi.org'),
                    ('DNS', 'docs.python.org'),
                    ('DNS', 'testpypi.org'),
                    ('DNS', 'bugs.python.org'),
                    ('DNS', 'wiki.python.org'),
                    ('DNS', 'hg.python.org'),
                    ('DNS', 'mail.python.org'),
                    ('DNS', 'packaging.python.org'),
                    ('DNS', 'pythonhosted.org'),
                    ('DNS', 'www.pythonhosted.org'),
                    ('DNS', 'test.pythonhosted.org'),
                    ('DNS', 'us.pycon.org'),
                    ('DNS', 'id.python.org')),
 'version': 3}
									

>>> conn.sendall(b"HEAD / HTTP/1.0\r\nHost: linuxfr.org\r\n\r\n")
>>> pprint.pprint(conn.recv(1024).split(b"\r\n"))
[b'HTTP/1.1 200 OK',
 b'Date: Sat, 18 Oct 2014 18:27:20 GMT',
 b'Server: nginx',
 b'Content-Type: text/html; charset=utf-8',
 b'X-Frame-Options: SAMEORIGIN',
 b'Content-Length: 45679',
 b'Accept-Ranges: bytes',
 b'Via: 1.1 varnish',
 b'Age: 2188',
 b'X-Served-By: cache-lcy1134-LCY',
 b'X-Cache: HIT',
 b'X-Cache-Hits: 11',
 b'Vary: Cookie',
 b'Strict-Transport-Security: max-age=63072000; includeSubDomains',
 b'Connection: close',
 b'',
 b'']
									

import socket, ssl
context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
context.load_cert_chain(certfile="mycertfile", keyfile="mykeyfile")
bindsocket = socket.socket()
bindsocket.bind(('myaddr.mydomain.com', 10023))
bindsocket.listen(5)
									

while True:
    newsocket, fromaddr = bindsocket.accept()
    connstream = context.wrap_socket(newsocket, server_side=True)
    try:
        deal_with_client(connstream)
    finally:
        connstream.shutdown(socket.SHUT_RDWR)
        connstream.close()
									

def deal_with_client(connstream):
    data = connstream.recv(1024)
    # empty data means the client is finished with us
    while data:
        if not do_something(connstream, data):
            # we'll assume do_something returns False
            # when we're finished with client
            break
        data = connstream.recv(1024)
    # finished with client
									

18.2.6. Notes on non-blocking sockets ¶

SSL sockets behave slightly different than regular sockets in non-blocking mode. When working with non-blocking sockets, there are thus several things you need to be aware of:

• Most SSLSocket methods will raise either SSLWantWriteError or SSLWantReadError 而不是 BlockingIOError if an I/O operation would block. SSLWantReadError will be raised if a read operation on the underlying socket is necessary, and SSLWantWriteError for a write operation on the underlying socket. Note that attempts to write to an SSL socket may require reading from the underlying socket first, and attempts to read from the SSL socket may require a prior write to the underlying socket.

  3.5 版改变： In earlier Python versions, the SSLSocket.send() method returned zero instead of raising SSLWantWriteError or SSLWantReadError .

• 调用 select() tells you that the OS-level socket can be read from (or written to), but it does not imply that there is sufficient data at the upper SSL layer. For example, only part of an SSL frame might have arrived. Therefore, you must be ready to handle SSLSocket.recv() and SSLSocket.send() failures, and retry after another call to select() .

• Conversely, since the SSL layer has its own framing, a SSL socket may still have data available for reading without select() being aware of it. Therefore, you should first call SSLSocket.recv() to drain any potentially available data, and then only block on a select() call if still necessary.

  (of course, similar provisions apply when using other primitives such as poll() , or those in the selectors 模块)

• The SSL handshake itself will be non-blocking: the SSLSocket.do_handshake() method has to be retried until it returns successfully. Here is a synopsis using select() to wait for the socket’s readiness:

  while True:
      try:
          sock.do_handshake()
          break
      except ssl.SSLWantReadError:
          select.select([sock], [], [])
      except ssl.SSLWantWriteError:
          select.select([], [sock], [])
  										

18.2.7. Memory BIO Support ¶

Ever since the SSL module was introduced in Python 2.6, the SSLSocket class has provided two related but distinct areas of functionality:

• SSL protocol handling
• Network IO

The network IO API is identical to that provided by socket.socket , from which SSLSocket also inherits. This allows an SSL socket to be used as a drop-in replacement for a regular socket, making it very easy to add SSL support to an existing application.

Combining SSL protocol handling and network IO usually works well, but there are some cases where it doesn’t. An example is async IO frameworks that want to use a different IO multiplexing model than the “select/poll on a file descriptor” (readiness based) model that is assumed by socket.socket and by the internal OpenSSL socket IO routines. This is mostly relevant for platforms like Windows where this model is not efficient. For this purpose, a reduced scope variant of SSLSocket called SSLObject is provided.

class ssl. SSLObject ¶

A reduced-scope variant of SSLSocket representing an SSL protocol instance that does not contain any network IO methods. This class is typically used by framework authors that want to implement asynchronous IO for SSL through memory buffers.

This class implements an interface on top of a low-level SSL object as implemented by OpenSSL. This object captures the state of an SSL connection but does not provide any network IO itself. IO needs to be performed through separate “BIO” objects which are OpenSSL’s IO abstraction layer.

An SSLObject instance can be created using the wrap_bio() method. This method will create the SSLObject instance and bind it to a pair of BIOs. The incoming BIO is used to pass data from Python to the SSL protocol instance, while the outgoing BIO is used to pass data the other way around.

The following methods are available:

• context
• server_side
• server_hostname
• session
• session_reused
• read()
• write()
• getpeercert()
• selected_npn_protocol()
• cipher()
• shared_ciphers()
• compression()
• pending()
• do_handshake()
• unwrap()
• get_channel_binding()

When compared to SSLSocket , this object lacks the following features:

• Any form of network IO; recv() and send() read and write only to the underlying MemoryBIO buffers.
• There is no do_handshake_on_connect machinery. You must always manually call do_handshake() to start the handshake.
• There is no handling of suppress_ragged_eofs . All end-of-file conditions that are in violation of the protocol are reported via the SSLEOFError 异常。
• The method unwrap() call does not return anything, unlike for an SSL socket where it returns the underlying socket.
• server_name_callback callback passed to SSLContext.set_servername_callback() will get an SSLObject instance instead of a SSLSocket instance as its first parameter.

Some notes related to the use of SSLObject :

• All IO on an SSLObject is non-blocking . This means that for example read() will raise an SSLWantReadError if it needs more data than the incoming BIO has available.
• There is no module-level wrap_bio() call like there is for wrap_socket() . An SSLObject is always created via an SSLContext .

An SSLObject communicates with the outside world using memory buffers. The class MemoryBIO provides a memory buffer that can be used for this purpose. It wraps an OpenSSL memory BIO (Basic IO) object:

class ssl. MemoryBIO ¶

A memory buffer that can be used to pass data between Python and an SSL protocol instance.

pending ¶

Return the number of bytes currently in the memory buffer.

eof ¶

A boolean indicating whether the memory BIO is current at the end-of-file position.

read ( n=-1 ) ¶

Read up to n bytes from the memory buffer. If n is not specified or negative, all bytes are returned.

write ( buf ) ¶

Write the bytes from buf to the memory BIO. The buf argument must be an object supporting the buffer protocol.

The return value is the number of bytes written, which is always equal to the length of buf .

write_eof ( ) ¶

Write an EOF marker to the memory BIO. After this method has been called, it is illegal to call write() . The attribute eof will become true after all data currently in the buffer has been read.

18.2.8. SSL 会话 ¶

class ssl. SSLSession ¶

Session object used by session .

id ¶

time ¶

timeout ¶

ticket_lifetime_hint ¶

has_ticket ¶

18.2.9. Security considerations ¶

>>> import ssl, smtplib
>>> smtp = smtplib.SMTP("mail.python.org", port=587)
>>> context = ssl.create_default_context()
>>> smtp.starttls(context=context)
(220, b'2.0.0 Ready to start TLS')
									

>>> client_context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
>>> client_context.options |= ssl.OP_NO_TLSv1
>>> client_context.options |= ssl.OP_NO_TLSv1_1
										

18.2.10. LibreSSL 支持 ¶

LibreSSL is a fork of OpenSSL 1.0.1. The ssl module has limited support for LibreSSL. Some features are not available when the ssl module is compiled with LibreSSL.

• LibreSSL >= 2.6.1 no longer supports NPN. The methods SSLContext.set_npn_protocols() and SSLSocket.selected_npn_protocol() are not available.
• SSLContext.set_default_verify_paths() ignores the env vars SSL_CERT_FILE and SSL_CERT_PATH although get_default_verify_paths() still reports them.