pythonpython-3.xsslfips

How to implement FIPS_mode() and FIPS_mode_set() in Python 3.6's ssl module?


I am trying to implement the FIPS_mode and FIPS_mode_set functions in Python's ssl module since those are not present by default. A patch for Python 3.4 has already been submitted and rejected due to various using reasons.

Using that patch as an inspiration, i made some modifications and added the following code in ssl.py:

try:
    from _ssl import FIPS_mode, FIPS_mode_set
except ImportError:
    pass

And the following code in _ssl.c:

#define EXPORT_FIPSMODE_FUNCS

#ifdef EXPORT_FIPSMODE_FUNCS


static PyObject *
_ssl_FIPS_mode_impl(PyObject *module) {
    return PyLong_FromLong(FIPS_mode());
}

static PyObject *
_ssl_FIPS_mode_set_impl(PyObject *module, int n) {
    if (FIPS_mode_set(n) == 0) {
        _setSSLError(ERR_error_string(ERR_get_error(), NULL) , 0, __FILE__, __LINE__);
        return NULL;
    }
    Py_RETURN_NONE;
}

#endif  //EXPORT_FIPSMODE_FUNCS

/* List of functions exported by this module. */
static PyMethodDef PySSL_methods[] = {
    _SSL__TEST_DECODE_CERT_METHODDEF
    _SSL_RAND_ADD_METHODDEF
    _SSL_RAND_BYTES_METHODDEF
    _SSL_RAND_PSEUDO_BYTES_METHODDEF
    _SSL_RAND_EGD_METHODDEF
    _SSL_RAND_STATUS_METHODDEF
    _SSL_GET_DEFAULT_VERIFY_PATHS_METHODDEF
    _SSL_ENUM_CERTIFICATES_METHODDEF
    _SSL_ENUM_CRLS_METHODDEF
    _SSL_TXT2OBJ_METHODDEF
    _SSL_NID2OBJ_METHODDEF
    _SSL_FIPS_MODE_SET_METHODDEF
    _SSL_FIPS_MODE_METHODDEF
    {NULL,                  NULL}            /* Sentinel */
};

This however is throwing the following errors:

./Modules/_ssl.c:5060:5: error: '_SSL_FIPS_MODE_SET_METHODDEF' undeclared here (not in a function)
     _SSL_FIPS_MODE_SET_METHODDEF

./Modules/_ssl.c:5061:5: error: expected '}' before '_SSL_FIPS_MODE_METHODDEF'
     _SSL_FIPS_MODE_METHODDEF

./Modules/_ssl.c:4641:1: warning: '_ssl_FIPS_mode_impl' defined but not used [-Wunused-function]  _ssl_FIPS_mode_impl(PyObject
*module) { 

./Modules/_ssl.c:4646:1: warning: '_ssl_FIPS_mode_set_impl' defined but not used [-Wunused-function] 
_ssl_FIPS_mode_set_impl(PyObject *module, int n) {  ^

I am pretty sure i am missing something extremely trivial here but i cant seem to figure out what exactly. Any help would be appreciated! Thanks!

Update:

A big shoutout to @CristiFati who pointed out that i was missing the macros which needed to be defined, I was able to solve this. In case someone else needs to implement FIPS Mode in Python 3.6, add the following code:

_ssl.c:

static PyObject *
_ssl_FIPS_mode_impl(PyObject *module) {
    return PyLong_FromLong(FIPS_mode());
}

static PyObject *
_ssl_FIPS_mode_set_impl(PyObject *module, int n) {
    if (FIPS_mode_set(n) == 0) {
        _setSSLError(ERR_error_string(ERR_get_error(), NULL) , 0, __FILE__, __LINE__);
        return NULL;
    }
    Py_RETURN_NONE;
}

static PyMethodDef PySSL_methods[] = {
    _SSL__TEST_DECODE_CERT_METHODDEF
    _SSL_RAND_ADD_METHODDEF
    _SSL_RAND_BYTES_METHODDEF
    _SSL_RAND_PSEUDO_BYTES_METHODDEF
    _SSL_RAND_EGD_METHODDEF
    _SSL_RAND_STATUS_METHODDEF
    _SSL_GET_DEFAULT_VERIFY_PATHS_METHODDEF
    _SSL_ENUM_CERTIFICATES_METHODDEF
    _SSL_ENUM_CRLS_METHODDEF
    _SSL_TXT2OBJ_METHODDEF
    _SSL_NID2OBJ_METHODDEF
    _SSL_FIPS_MODE_METHODDEF
    _SSL_FIPS_MODE_SET_METHODDEF
    {NULL,                  NULL}            /* Sentinel */
}; 

_ssl.c.h:

PyDoc_STRVAR(_ssl_FIPS_mode__doc__,
"FIPS Mode");

#define _SSL_FIPS_MODE_METHODDEF    \
    {"FIPS_mode", (PyCFunction)_ssl_FIPS_mode, METH_NOARGS, _ssl_FIPS_mode__doc__},    

static PyObject *
_ssl_FIPS_mode_impl(PyObject *module);

static PyObject *
_ssl_FIPS_mode(PyObject *module, PyObject *Py_UNUSED(ignored))
{
    return _ssl_FIPS_mode_impl(module);
}

PyDoc_STRVAR(_ssl_FIPS_mode_set_doc__,
"FIPS Mode Set");

#define _SSL_FIPS_MODE_SET_METHODDEF    \
    {"FIPS_mode_set", (PyCFunction)_ssl_FIPS_mode_set, METH_O, _ssl_FIPS_mode_set_doc__},   

static PyObject *
_ssl_FIPS_mode_set_impl(PyObject *module, int n);

static PyObject *
_ssl_FIPS_mode_set(PyObject *module, PyObject *arg)
{
    PyObject *return_value = NULL;
    int n;

    if (!PyArg_Parse(arg, "i:FIPS_mode_set", &n)) {
        goto exit;
    }
    return_value = _ssl_FIPS_mode_set_impl(module, n);

exit:
    return return_value;
}

ssl.py:

try:
    from _ssl import FIPS_mode, FIPS_mode_set
    print('successful import')
except ImportError as e:
    print('error in importing')
    print(e)   

Solution

  • Looking at the source code, I noticed that since Python 3.5, the ${PYTHON_SRC_DIR}/Modules/_ssl.c structure has changed (got "a little bit" more structured and also contains generated code), compared to the 3.4 version that I submitted the patch to ([Python.Bugs]: FIPS_mode() and FIPS_mode_set() functions in Python (ssl)).
    Basically, every entry in the PySSL_methods array is no longer defined on the spot, but indirectly, via a preprocessor macro.
    You acted according to the new standard, but forgot to define the macros.

    In order to fix the problem:

    1. Define the 2 macros for the PyMethodDef entries (inside #ifdef EXPORT_FIPSMODE_FUNCS):

      // ...
      
      }
      
      #define _SSL_FIPS_MODE_METHODDEF    \
          {"FIPS_mode", (PyCFunction)_ssl_FIPS_mode_impl, METH_NOARGS, NULL},
      
      #define _SSL_FIPS_MODE_SET_METHODDEF    \
          {"FIPS_mode_set", (PyCFunction)_ssl_FIPS_mode_set_impl, METH_O, NULL},
      
      #endif  // EXPORT_FIPSMODE_FUNCS
      
      // ...
      
    2. "Protect" the new macros by an #ifdef clause (similarly to where they were defined) when defining PySSL_methods (so that if the EXPORT_FIPSMODE_FUNCS macro isn't defined, you won't get a compile error):

      // ...
      
      _SSL_NID2OBJ_METHODDEF
      #ifdef EXPORT_FIPSMODE_FUNCS
      _SSL_FIPS_MODE_METHODDEF
      _SSL_FIPS_MODE_SET_METHODDEF
      #endif  // EXPORT_FIPSMODE_FUNCS
      {NULL,                  NULL}            /* Sentinel */
      
      // ...
      

    Notes:



    Update #0

    Python-3.6.4-ssl_fips.diff:

    --- Python-3.6.4/Modules/_ssl.c.orig    2018-07-27 19:10:06.131999999 +0300
    +++ Python-3.6.4/Modules/_ssl.c 2018-07-27 20:32:15.531999999 +0300
    @@ -4789,6 +4789,46 @@
         return result;
     }
     
    +#if defined(EXPORT_FIPSMODE_FUNCS)
    +
    +unsigned char _fips_table_sig[0x0C] = {0x21, 0x7A, 0x65, 0x6C, 0x75, 0x72, 0x20, 0x49, 0x54, 0x41, 0x46, 0x00};
    +
    +/*[clinic input]
    +_ssl.FIPS_mode
    +
    +Return 1 (!=0) if FIPS mode is enabled, 0 otherwise.
    +[clinic start generated code]*/
    +
    +static PyObject *
    +_ssl_FIPS_mode_impl(PyObject *module)
    +/*[clinic end generated code: output=89f5a88ec715a291 input=52e4e5fdd1f555c7]*/
    +{
    +    return PyLong_FromLong(FIPS_mode());
    +}
    +
    +/*[clinic input]
    +_ssl.FIPS_mode_set
    +    mode: int
    +    /
    +
    +Try to set the FIPS mode to 'mode' (int).
    +
    +Return nothing. Raise SSLError when enabling FIPS mode fails.
    +[clinic start generated code]*/
    +
    +static PyObject *
    +_ssl_FIPS_mode_set_impl(PyObject *module, int mode)
    +/*[clinic end generated code: output=70e3e9f3bb4fce65 input=899c21a986720235]*/
    +{
    +if (FIPS_mode_set(mode) == 0) {
    +        _setSSLError(ERR_error_string(ERR_get_error(), NULL), 0, __FILE__, __LINE__);
    +        return NULL;
    +    }
    +    Py_RETURN_NONE;
    +}
    +
    +#endif  // EXPORT_FIPSMODE_FUNCS
    +
     #ifdef _MSC_VER
     
     static PyObject*
    @@ -5055,6 +5095,8 @@
         _SSL_ENUM_CRLS_METHODDEF
         _SSL_TXT2OBJ_METHODDEF
         _SSL_NID2OBJ_METHODDEF
    +    _SSL_FIPS_MODE_METHODDEF
    +    _SSL_FIPS_MODE_SET_METHODDEF
         {NULL,                  NULL}            /* Sentinel */
     };
     
    --- Python-3.6.4/Modules/clinic/_ssl.c.h.orig   2018-07-27 19:10:48.067999999 +0300
    +++ Python-3.6.4/Modules/clinic/_ssl.c.h    2018-07-27 20:31:04.507999999 +0300
    @@ -1062,6 +1062,61 @@
         return return_value;
     }
     
    +#if defined(EXPORT_FIPSMODE_FUNCS)
    +
    +PyDoc_STRVAR(_ssl_FIPS_mode__doc__,
    +"FIPS_mode($module, /)\n"
    +"--\n"
    +"\n"
    +"Return 1 (!=0) if FIPS mode is enabled, 0 otherwise.");
    +
    +#define _SSL_FIPS_MODE_METHODDEF    \
    +    {"FIPS_mode", (PyCFunction)_ssl_FIPS_mode, METH_NOARGS, _ssl_FIPS_mode__doc__},
    +
    +static PyObject *
    +_ssl_FIPS_mode_impl(PyObject *module);
    +
    +static PyObject *
    +_ssl_FIPS_mode(PyObject *module, PyObject *Py_UNUSED(ignored))
    +{
    +    return _ssl_FIPS_mode_impl(module);
    +}
    +
    +#endif /* defined(EXPORT_FIPSMODE_FUNCS) */
    +
    +#if defined(EXPORT_FIPSMODE_FUNCS)
    +
    +PyDoc_STRVAR(_ssl_FIPS_mode_set__doc__,
    +"FIPS_mode_set($module, mode, /)\n"
    +"--\n"
    +"\n"
    +"Try to set the FIPS mode to \'mode\' (int).\n"
    +"\n"
    +"Return nothing. Raise SSLError when enabling FIPS mode fails.");
    +
    +#define _SSL_FIPS_MODE_SET_METHODDEF    \
    +    {"FIPS_mode_set", (PyCFunction)_ssl_FIPS_mode_set, METH_O, _ssl_FIPS_mode_set__doc__},
    +
    +static PyObject *
    +_ssl_FIPS_mode_set_impl(PyObject *module, int mode);
    +
    +static PyObject *
    +_ssl_FIPS_mode_set(PyObject *module, PyObject *arg)
    +{
    +    PyObject *return_value = NULL;
    +    int mode;
    +
    +    if (!PyArg_Parse(arg, "i:FIPS_mode_set", &mode)) {
    +        goto exit;
    +    }
    +    return_value = _ssl_FIPS_mode_set_impl(module, mode);
    +
    +exit:
    +    return return_value;
    +}
    +
    +#endif /* defined(EXPORT_FIPSMODE_FUNCS) */
    +
     #if defined(_MSC_VER)
     
     PyDoc_STRVAR(_ssl_enum_certificates__doc__,
    @@ -1161,6 +1216,14 @@
         #define _SSL_RAND_EGD_METHODDEF
     #endif /* !defined(_SSL_RAND_EGD_METHODDEF) */
     
    +#ifndef _SSL_FIPS_MODE_METHODDEF
    +    #define _SSL_FIPS_MODE_METHODDEF
    +#endif /* !defined(_SSL_FIPS_MODE_METHODDEF) */
    +
    +#ifndef _SSL_FIPS_MODE_SET_METHODDEF
    +    #define _SSL_FIPS_MODE_SET_METHODDEF
    +#endif /* !defined(_SSL_FIPS_MODE_SET_METHODDEF) */
    +
     #ifndef _SSL_ENUM_CERTIFICATES_METHODDEF
         #define _SSL_ENUM_CERTIFICATES_METHODDEF
     #endif /* !defined(_SSL_ENUM_CERTIFICATES_METHODDEF) */
    @@ -1168,4 +1231,4 @@
     #ifndef _SSL_ENUM_CRLS_METHODDEF
         #define _SSL_ENUM_CRLS_METHODDEF
     #endif /* !defined(_SSL_ENUM_CRLS_METHODDEF) */
    -/*[clinic end generated code: output=a8b184655068c238 input=a9049054013a1b77]*/
    +/*[clinic end generated code: output=94d0ec4213d44124 input=a9049054013a1b77]*/
    --- Python-3.6.4/Lib/ssl.py.orig    2018-07-27 19:10:29.827999999 +0300
    +++ Python-3.6.4/Lib/ssl.py 2018-03-28 23:30:35.065667344 +0300
    @@ -114,6 +114,11 @@
         # LibreSSL does not provide RAND_egd
         pass
     
    +try:
    +    from _ssl import FIPS_mode, FIPS_mode_set
    +except ImportError:
    +    # Compiled without FIPS functions support
    +    pass 
     
     from _ssl import HAS_SNI, HAS_ECDH, HAS_NPN, HAS_ALPN, HAS_TLSv1_3
     from _ssl import _OPENSSL_API_VERSION
    --- Python-3.6.4/setup.py.orig  2018-07-27 19:09:33.763999999 +0300
    +++ Python-3.6.4/setup.py   2018-03-28 23:30:35.061667315 +0300
    @@ -862,6 +862,7 @@
                 ssl_libs is not None):
                 exts.append( Extension('_ssl', ['_ssl.c'],
                                        include_dirs = ssl_incs,
    +                                   define_macros = [("EXPORT_FIPSMODE_FUNCS", None)],
                                        library_dirs = ssl_libs,
                                        libraries = ['ssl', 'crypto'],
                                        depends = ['socketmodule.h']), )
    

    Notes:

    I also tested the changes (at one point I used the OpenSSL version that I've built for [SO]: How to enable FIPS mode for libcrypto and libssl packaged with Python? (@CristiFati's answer))

    Output:

    [cfati@cfati-ubtu16x64-0:~/Work/Dev/StackOverflow/q049493537]> LD_LIBRARY_PATH=./py364-nofips/lib ./py364-nofips/bin/python3 -c "import ssl;print(ssl.FIPS_mode())"
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
    AttributeError: module 'ssl' has no attribute 'FIPS_mode'
    [cfati@cfati-ubtu16x64-0:~/Work/Dev/StackOverflow/q049493537]> LD_LIBRARY_PATH=py364-fips/lib py364-fips/bin/python3 -c "import ssl;print(ssl.FIPS_mode(), ssl.FIPS_mode_set(0), ssl.FIPS_mode());print(ssl.FIPS_mode_set(1), ssl.FIPS_mode())"
    0 None 0
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
    ssl.SSLError: error:0F06D065:common libcrypto routines:FIPS_mode_set:fips mode not supported (_ssl.c:4822)
    [cfati@cfati-ubtu16x64-0:~/Work/Dev/StackOverflow/q049493537]> LD_LIBRARY_PATH=py364-fips/lib:../q049320993/ssl/build/lib py364-fips/bin/python3 -c "import ssl;print(ssl.FIPS_mode(), ssl.FIPS_mode_set(0), ssl.FIPS_mode());print(ssl.FIPS_mode_set(1), ssl.FIPS_mode())"
    0 None 0
    None 1
    

    Might also look over [SO]: OpenSSL FIPS_mode_set not working in Python cryptography library (@CristiFati's answer).