Patch 10124 by Bill Janssen, docs for the new ssl code.
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+
+:mod:`ssl` --- SSL wrapper for socket objects, and utility functions
+====================================================================
+
+.. module:: ssl
+ :synopsis: SSL wrapper for socket objects, and utility functions
+
+.. versionadded:: 2.6
+
+
+This module provides access to Transport Layer Security (often known
+as "Secure Sockets Layer") encryption and peer authentication
+facilities for network sockets, both client-side and server-side.
+This module uses the OpenSSL library. It is available on all modern
+Unix systems, Windows, Mac OS X, and probably additional
+platforms, as long as OpenSSL is installed on that platform.
+
+.. note::
+
+ Some behavior may be platform dependent, since calls are made to the operating
+ system socket APIs.
+
+This section documents the objects and functions in the `ssl` module;
+for more general information about TLS, SSL, and certificates, the
+reader is referred to the paper, *Introducing SSL and Certificates using OpenSSL*, by Frederick J. Hirsch, at
+http://old.pseudonym.org/ssl/wwwj-index.html.
+
+This module defines a class, :class:`ssl.sslsocket`, which is
+derived from the :class:`socket.socket` type, and supports additional
+:meth:`read` and :meth:`write` methods, along with a method, :meth:`getpeercert`,
+to retrieve the certificate of the other side of the connection.
+
+This module defines the following functions, exceptions, and constants:
+
+.. function:: cert_time_to_seconds(timestring)
+
+ Returns a floating-point value containing a normal seconds-after-the-epoch time
+ value, given the time-string representing the "notBefore" or "notAfter" date
+ from a certificate.
+
+ Here's an example::
+
+ >>> import ssl
+ >>> ssl.cert_time_to_seconds("May 9 00:00:00 2007 GMT")
+ 1178694000.0
+ >>> import time
+ >>> time.ctime(ssl.cert_time_to_seconds("May 9 00:00:00 2007 GMT"))
+ 'Wed May 9 00:00:00 2007'
+ >>>
+
+.. exception:: sslerror
+
+ Raised to signal an error from the underlying SSL implementation. This
+ signifies some problem in the higher-level
+ encryption and authentication layer that's superimposed on the underlying
+ network connection.
+
+.. data:: CERT_NONE
+
+ Value to pass to the `cert_reqs` parameter to :func:`sslobject`
+ when no certificates will be required or validated from the other
+ side of the socket connection.
+
+.. data:: CERT_OPTIONAL
+
+ Value to pass to the `cert_reqs` parameter to :func:`sslobject`
+ when no certificates will be required from the other side of the
+ socket connection, but if they are provided, will be validated.
+ Note that use of this setting requires a valid certificate
+ validation file also be passed as a value of the `ca_certs`
+ parameter.
+
+.. data:: CERT_REQUIRED
+
+ Value to pass to the `cert_reqs` parameter to :func:`sslobject`
+ when certificates will be required from the other side of the
+ socket connection. Note that use of this setting requires a valid certificate
+ validation file also be passed as a value of the `ca_certs`
+ parameter.
+
+.. data:: PROTOCOL_SSLv2
+
+ Selects SSL version 2 as the channel encryption protocol.
+
+.. data:: PROTOCOL_SSLv23
+
+ Selects SSL version 2 or 3 as the channel encryption protocol. This is a setting to use for maximum compatibility
+ with the other end of an SSL connection, but it may cause the specific ciphers chosen for the encryption to be
+ of fairly low quality.
+
+.. data:: PROTOCOL_SSLv3
+
+ Selects SSL version 3 as the channel encryption protocol.
+
+.. data:: PROTOCOL_TLSv1
+
+ Selects SSL version 2 as the channel encryption protocol. This is
+ the most modern version, and probably the best choice for maximum
+ protection, if both sides can speak it.
+
+
+Certificates
+------------
+
+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 he claims 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".
+
+The underlying system which is used in the Python SSL support is
+called "OpenSSL". It contains facilities for constructing and
+validating certificates. In the Python use of certificates, the other
+side of a network connection can be required to produce a certificate,
+and that certificate can be validated against a file filled with
+self-signed *root* certificates (so-called because the issuer is the
+same as the subject), and and "CA" (certification authority)
+certificates assured by those root certificates (and by other CA
+certificates). Either side of a connection, client or server, can
+request certificates and validation, and the connection can be optionally
+set up to fail if a valid certificate is not presented by the other side.
+
+
+sslsocket Objects
+-----------------
+
+.. class:: sslsocket(sock [, keyfile=None, certfile=None, server_side=False, cert_reqs=CERT_NONE, ssl_version=PROTOCOL_SSLv23, ca_certs=None])
+
+ Takes an instance *sock* of :class:`socket.socket`, and returns an instance of a subtype
+ of :class:`socket.socket` which wraps the underlying socket in an SSL context.
+ For client-side sockets, the context construction is lazy; if the underlying socket isn't
+ connected yet, the context construction will be performed after :meth:`connect` is called
+ on the socket.
+
+ The `keyfile` and `certfile` parameters specify optional files which contain a certificate
+ to be used to identify the local side of the connection. Often the private key is stored
+ in the same file as the certificate; in this case, only the `certfile` parameter need be
+ passed. If the private key is stored in a separate file, both parameters must be used.
+
+ The parameter `server_side` is a boolean which identifies whether server-side or client-side
+ behavior is desired from this socket.
+
+ The parameter `cert_reqs` specifies whether a certificate is
+ required from the other side of the connection, and whether it will
+ be validated if provided. It must be one of the three values
+ :const:`CERT_NONE` (certificates ignored), :const:`CERT_OPTIONAL` (not required,
+ but validated if provided), or :const:`CERT_REQUIRED` (required and
+ validated). If the value of this parameter is not :const:`CERT_NONE`, then
+ the `ca_certs` parameter must point to a file of CA certificates.
+
+ The parameter `ssl_version` specifies which version of the SSL protocol to use. Typically,
+ the server specifies this, and a client connecting to it must use the same protocol. An
+ SSL server using :const:`PROTOCOL_SSLv23` can understand a client connecting via SSL2, SSL3, or TLS1,
+ but a client using :const:`PROTOCOL_SSLv23` can only connect to an SSL2 server.
+
+ The `ca_certs` file contains a set of concatenated "certification authority" certificates,
+ which are used to validate certificates passed from the other end of the connection.
+ This file
+ contains the certificates in PEM format (IETF RFC 1422) where each certificate is
+ encoded in base64 encoding and surrounded with a header and footer::
+
+ -----BEGIN CERTIFICATE-----
+ ... (CA certificate in base64 encoding) ...
+ -----END CERTIFICATE-----
+
+ The various certificates in the file are just concatenated together::
+
+ -----BEGIN CERTIFICATE-----
+ ... (CA certificate in base64 encoding) ...
+ -----END CERTIFICATE-----
+ -----BEGIN CERTIFICATE-----
+ ... (a second CA certificate in base64 encoding) ...
+ -----END CERTIFICATE-----
+ -----BEGIN CERTIFICATE-----
+ ... (a root certificate in base64 encoding) ...
+ -----END CERTIFICATE-----
+
+ Some "standard" root certificates are available at
+ http://www.thawte.com/roots/ (for Thawte roots) and
+ http://www.verisign.com/support/roots.html (for Verisign roots).
+
+.. method:: sslsocket.read([nbytes])
+
+ Reads up to `nbytes` bytes from the SSL-encrypted channel and returns them.
+
+.. method:: sslsocket.write(data)
+
+ Writes the `data` to the other side of the connection, using the SSL channel to encrypt. Returns the number
+ of bytes written.
+
+.. method:: sslsocket.getpeercert()
+
+ If there is no certificate for the peer on the other end of the connection, returns `None`.
+ If a certificate was received from the peer, but not validated, returns an empty `dict` instance.
+ If a certificate was received and validated, returns a `dict` instance with the fields
+ `subject` (the principal for which the certificate was issued), `issuer` (the signer of
+ the certificate), `notBefore` (the time before which the certificate should not be trusted),
+ and `notAfter` (the time after which the certificate should not be trusted) filled in.
+
+ The "subject" and "issuer" fields are themselves dictionaries containing the fields given
+ in the certificate's data structure for each principal::
+
+ {'issuer': {'commonName': u'somemachine.python.org',
+ 'countryName': u'US',
+ 'localityName': u'Wilmington',
+ 'organizationName': u'Python Software Foundation',
+ 'organizationalUnitName': u'SSL',
+ 'stateOrProvinceName': u'Delaware'},
+ 'subject': {'commonName': u'somemachine.python.org',
+ 'countryName': u'US',
+ 'localityName': u'Wilmington',
+ 'organizationName': u'Python Software Foundation',
+ 'organizationalUnitName': u'SSL',
+ 'stateOrProvinceName': u'Delaware'},
+ 'notAfter': 'Sep 4 21:54:26 2007 GMT',
+ 'notBefore': 'Aug 25 21:54:26 2007 GMT',
+ 'version': 2}
+
+ This certificate is said to be *self-signed*, because the subject
+ and issuer are the same entity. The *version* field refers the the X509 version
+ that's used for the certificate.
+
+Examples
+--------
+
+This example connects to an SSL server, prints the server's address and certificate,
+sends some bytes, and reads part of the response::
+
+ import socket, ssl, pprint
+
+ s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+ ssl_sock = ssl.sslsocket(s, ca_certs="/etc/ca_certs_file", cert_reqs=ssl.CERT_REQUIRED)
+
+ ssl_sock.connect(('www.verisign.com', 443))
+
+ print repr(ssl_sock.getpeername())
+ print pprint.pformat(ssl_sock.getpeercert())
+
+ # Set a simple HTTP request -- use httplib in actual code.
+ ssl_sock.write("""GET / HTTP/1.0\r
+ Host: www.verisign.com\r\n\r\n""")
+
+ # Read a chunk of data. Will not necessarily
+ # read all the data returned by the server.
+ data = ssl_sock.read()
+
+ # note that closing the sslsocket will also close the underlying socket
+ ssl_sock.close()
+
+As of August 25, 2007, the certificate printed by this program
+looked like this::
+
+ {'issuer': {'commonName': u'VeriSign Class 3 Extended Validation SSL SGC CA',
+ 'countryName': u'US',
+ 'organizationName': u'VeriSign, Inc.',
+ 'organizationalUnitName': u'Terms of use at https://www.verisign.com/rpa (c)06'},
+ 'subject': {'1.3.6.1.4.1.311.60.2.1.2': u'Delaware',
+ '1.3.6.1.4.1.311.60.2.1.3': u'US',
+ 'commonName': u'www.verisign.com',
+ 'countryName': u'US',
+ 'localityName': u'Mountain View',
+ 'organizationName': u'VeriSign, Inc.',
+ 'organizationalUnitName': u'Terms of use at www.verisign.com/rpa (c)06',
+ 'postalCode': u'94043',
+ 'serialNumber': u'2497886',
+ 'stateOrProvinceName': u'California',
+ 'streetAddress': u'487 East Middlefield Road'},
+ 'notAfter': 'May 8 23:59:59 2009 GMT',
+ 'notBefore': 'May 9 00:00:00 2007 GMT',
+ 'version': 2}
+
+For server operation, typically you'd need to have a server certificate, and private key, each in a file.
+You'd open a socket, bind it to a port, call :meth:`listen` on it, then start waiting for clients
+to connect::
+
+ import socket, ssl
+
+ bindsocket = socket.socket()
+ bindsocket.bind(('myaddr.mydomain.com', 10023))
+ bindsocket.listen(5)
+
+When one did, you'd call :meth:`accept` on the socket to get the new socket from the other
+end, and use :func:`sslsocket` to create a server-side SSL context for it::
+
+ while True:
+ newsocket, fromaddr = bindsocket.accept()
+ connstream = ssl.sslsocket(newsocket, server_side=True, certfile="mycertfile",
+ keyfile="mykeyfile", ssl_protocol=ssl.PROTOCOL_TLSv1)
+ deal_with_client(connstream)
+
+Then you'd read data from the `connstream` and do something with it till you are finished with the client (or the client is finished with you)::
+
+ def deal_with_client(connstream):
+
+ data = connstream.read()
+ # null 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.read()
+ # finished with client
+ connstream.close()
+
+And go back to listening for new client connections.
+
+