The Socket Stream SSL interface allows you to use Secure Socket Layer (SSL) with Lisp objects of type socket-stream.
The interface is based on the OpenSSL code, and most of it is simply an FLI interface to OpenSSL functions. The main LispWorks specific code is the way OpenSSL is integrated with socket-stream.
The Socket Stream SSL interface is in the "comm" module, so to load it you evaluate
(require "comm")
Note:
In this section we assume that the current package uses the comm package. That is, comm package symbols may not be qualified explicitly.
There are three ways to make a socket-stream with SSL processing:
(make-instance 'socket-stream :ssl-ctx ...) (open-tcp-stream ... :ssl-ctx ...)
(open-tcp-stream some-url 443 :ssl-ctx t)
When the value of the :ssl-ctx argument is a symbol, LispWorks automatically creates an SSL_CTX object and an SSL object and uses them. If you need to configure these objects, you can access them by the following methods:
:ssl-ctx or when calling attach-ssl (as described above) also pass :ctx-configure-callback and :ssl-configure-callback.The configuration interface contains mostly FLI function definitions that map directly to OpenSSL calls. See below for a list of those provided.
There are also some functions to make common cases simpler. These are read-dhparams, pem-read, set-ssl-ctx-options, set-ssl-ctx-password-callback, and set-ssl-ctx-dh.
The Lisp constants SSL_FILETYPE_ASN1 and SSL_FILETYPE_PEM representing file types are provided.
This section describes the mapping between OpenSSL function names and the corresponding Lisp names.
For functions that map directly to OpenSSL calls, the convention is to create the LISP name from the C name by replacing underscores by hyphens.
The following functions map directly to the OpenSSL functions. Check the OpenSSL documentation for details.
Where an OpenSSL function takes an SSL* or SSL_CTX*, the Lisp function's argument must be a foreign pointer of type ssl-pointer, ssl-ctx-pointer or ssl-cipher-pointer. Where an OpenSSL function takes a char* or int, the Lisp function's argument must be a string or integer. Where an OpenSSL function takes other kinds of pointers, the Lisp function's argument must be a foreign pointer. The return values are integers or foreign pointers unless stated otherwise.
If an error occurs in one of these functions, an error code is returned. They do not signal any Common Lisp conditions and so you should check the return value carefully.
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First value is number of bits the cipher actually uses. |
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If you need OpenSSL functionality that is not provided here, you can define your own foreign functions via the LispWorks Foreign Language Interface.
If you do this, an important point to note is that on Microsoft Windows, the :calling-convention must be :cdecl (it defaults to :stdcall). If using OpenSSL suddenly causes mysterious crashes, the calling-convention in your foreign function definitions is the first thing to check.
The keyword arguments :ssl-ctx, :ssl-side, :ctx-configure-callback and :ssl-configure-callback can be be passed to create and configure socket streams with SSL processing. The various methods for creating and configuring SSL streams accept these keyword arguments as shown in SSL configuration keywords.
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(make-instance 'socket-stream ...) and open-tcp-stream, when ssl-ctx is non-nil, call attach-ssl and pass it all the arguments.
:ssl-ctx specifies that SSL should be used, and also specifies the SSL_CTX object to use. See the OpenSSL manual entry for SSL_CTX_new for details of making a SSL_CTX. The value of ssl-ctx can be:
Together with ssl-side, this symbol specifies which protocol to use. ssl-ctx can be one of:
1) t or :default, meaning use the default. Currently this is the same as :v23.
2) One of :v2, :v3, :v23 or :tls-v1. These are mapped to the SSLv2_*, SSLv3_*, SSLv23_*, TLSv1_* methods.
LispWorks makes a new SSL_CTX object and uses it and frees it when the stream is closed. make-instance, attach-ssl and open-tcp-stream also make an SSL object, use it and free it when the stream is closed.
A foreign pointer of type
ssl-ctx-pointer
This corresponds to the C type SSL_CTX*. This is used and is not freed when the stream is closed. make-instance, attach-ssl and open-tcp-stream also make an SSL object, use it and free it when the stream is closed. The foreign pointer maybe a result of a call to make-ssl-ctx, but it can also be a result of your code, provided that it points to a valid SSL_CTX and has the type
ssl-ctx-pointer
.
A foreign pointer of type
ssl-pointer
This corresponds to the C type SSL*. This specifies the SSL to use in make-instance, attach-ssl and open-tcp-stream. This maybe a result of a call to ssl-new. but can also be a result of your code, provided that it points to a valid SSL object and has the type
ssl-pointer
. The SSL is used and is not freed when the stream is closed.
When you pass a
ssl-ctx-pointer
or a
ssl-pointer
foreign pointer, these must have already been set up correctly.
:ssl-side specifies which side the stream is. The value ssl-side can be one of :client, :server or :both. open-tcp-stream does not take this keyword and always uses :client. For the other calls this argument defaults to :server. The value of ssl-side is used in two cases:
When a new SSL_CTX object is created, it is used to select the method:
When a new SSL object is created, when ssl-side is either :client or :server, LispWorks calls ssl-set-connect-state or ssl-set-accept-state respectively.
If the value of ssl-ctx is a
ssl-pointer
, ssl-side is ignored.
:ctx-configure-callback specifies a callback, a function which takes a foreign pointer of type
ssl-ctx-pointer
. This is called immediately after a new SSL_CTX is created. If the value of ssl-ctx is not a symbol, ctx-configure-callback is ignored.
:ssl-configure-callback specifies a callback, a function which takes a foreign pointer of type
ssl-pointer
. This is called immediately after a new SSL is created. If the value of ssl-ctx is not a ssl-pointer, ssl-configure-callback is ignored.
You can attach SSL to an existing socket-stream by calling attach-ssl on the stream. attach-ssl ensures the OpenSSL library is loaded and seeds the Pseudo Random Number Generator (PRNG). The socket-stream SSL keyword arguments are processed by attach-ssl as described in Socket Stream SSL keyword arguments.
Detach SSL from a socket-stream and shut down the SSL with detach-ssl.
For full descriptions see attach-ssl and detach-ssl.
The C objects SSL and SSL_CTX are represented in LispWorks by foreign pointers with type ssl-pointer and ssl-ctx-pointer, which correspond to the C types SSL* and SSL_CTX*. These foreign types should be used for any foreign function that takes or returns these C types, and must be used when passing a foreign pointer as the value of the :ssl-ctx argument.
Making SSL objects is a way of getting access to them to perform configuration, but, especially in the case of the SSL_CTX, it is a useful way to avoid repeated calls to the configuration routines which may be time consuming. For example, if we have defined a function configure-a-ctx, and we want to read once every 60 seconds from some URL, we can write:
(loop (with-open-stream
(str (comm:open-tcp-stream some-url 443 :ssl-ctx t
:ctx-configure-callback 'configure-a-ctx))
(read-something str))
(sleep 60))
This will cause configure-a-ctx to be called each time. If it is expensive, we can call it only once by changing the code to:
(let ((ctx (comm:make-ssl-ctx :ssl-side :client)))
(configure-a-ctx ctx)
(loop (with-open-stream
(str (comm:open-tcp-stream some-url 443 :ssl-ctx ctx))
(read-something str))
(sleep 60))
(ssl-ctx-free ctx))
The SSL objects could be made either by make-ssl-ctx or ssl-new or by user code that calls the C functions SSL_CTX_new and SSL_new. destroy-ssl-ctx frees the SSL_CTX object. To free an SSL object you would call destroy-ssl. See the manual entries for full descriptions of these functions.
All the functions that make a SSL_CTX first call ensure-ssl, so normally you do not need to initialize the library. If your code makes a SSL_CTX itself (that is, not by calling any of the LispWorks interface functions), it needs to initialize the library first. Normally that should be done by an explicit call to ensure-ssl, which loads the SSL library and calls SSL_library_init and SSL_load_error_strings, and also does some LispWorks specific initializations. If your code must do the initialization, ensure-ssl should still be called with the argument :already-done t, which tells it that the library is already loaded and initialized.
At the time of writing, OpenSSL is available as shown in OpenSSL availability:
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Installed by default on most 32-bit and 64-bit distributions |
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32-bit and 64-bit libraries are available at |
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Installed by default on Solaris 10. For other versions, see the freeware from Sun at |
After installing (with pkgadd) you need to put the shared libraries libcrypto.so and libssl.o on the loader path. By default these are installed in /usr/local/ssl/lib.
Since OpenSSL is not a standard on all machines yet, the location of the library or libraries varies. By default, ensure-ssl loads libraries as shown in Loading the OpenSSL libraries.
On machines where the path is unknown or is incorrect, you must set the path. Do this by calling
set-ssl-library-path
, or by passing the path as the library-path argument to ensure-ssl.
If there are errors inside SSL, LispWorks will signal an error of type
ssl-condition
, which is a subclass of
socket-error
.
The condition can be one of the types
ssl-x509-lookup
,
ssl-closed
,
ssl-error
and
ssl-failure
. See the manual pages for details of these condition classes.
LispWorks User Guide and Reference Manual - 13 Feb 2015
