/*
 * rand.c
 *
 * Copyright (C) AB Strakt
 * See LICENSE file for details.
 *
 * PRNG management routines, thin wrappers.
 * See the file RATIONALE for a short explanation of why this module was written.
 *
 */
#include <Python.h>

/* 
 * In order to get the RAND_screen definition from the rand.h
 * WIN32 or WINDOWS needs to be defined, otherwise we get a
 * warning.
 */
#ifdef MS_WINDOWS
#  ifndef WIN32
#      define WIN32
#  endif
#endif
#include <openssl/rand.h>
#include "../util.h"

PyObject *rand_Error;

static char rand_doc[] = "\n\
PRNG management routines, thin wrappers.\n\
See the file RATIONALE for a short explanation of why this module was written.\n\
";

static char rand_add_doc[] = "\n\
Add data with a given entropy to the PRNG\n\
\n\
@param buffer: Buffer with random data\n\
@param entropy: The entropy (in bytes) measurement of the buffer\n\
@return: None\n\
";

static PyObject *
rand_add(PyObject *spam, PyObject *args)
{
    char *buf;
    int size;
    double entropy;

    if (!PyArg_ParseTuple(args, BYTESTRING_FMT "#d:add", &buf, &size, &entropy))
        return NULL;

    RAND_add(buf, size, entropy);

    Py_INCREF(Py_None);
    return Py_None;
}

static char rand_seed_doc[] = "\n\
Alias for rand_add, with entropy equal to length\n\
\n\
@param buffer: Buffer with random data\n\
@return: None\n\
";

static PyObject *
rand_seed(PyObject *spam, PyObject *args)
{
    char *buf;
    int size;

    if (!PyArg_ParseTuple(args, BYTESTRING_FMT "#:seed", &buf, &size))
        return NULL;

    RAND_seed(buf, size);

    Py_INCREF(Py_None);
    return Py_None;
}

static char rand_status_doc[] = "\n\
Retrieve the status of the PRNG\n\
\n\
@return: True if the PRNG is seeded enough, false otherwise\n\
";

static PyObject *
rand_status(PyObject *spam, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":status"))
        return NULL;

    return PyLong_FromLong((long)RAND_status());
}

#ifdef MS_WINDOWS
static char rand_screen_doc[] = "\n\
Add the current contents of the screen to the PRNG state. Availability:\n\
Windows.\n\
\n\
@return: None\n\
";

static PyObject *
rand_screen(PyObject *spam, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":screen"))
        return NULL;

    RAND_screen();
    Py_INCREF(Py_None);
    return Py_None;
}
#endif

static char rand_egd_doc[] = "\n\
Query an entropy gathering daemon (EGD) for random data and add it to the\n\
PRNG. I haven't found any problems when the socket is missing, the function\n\
just returns 0.\n\
\n\
@param path: The path to the EGD socket\n\
@param bytes: (optional) The number of bytes to read, default is 255\n\
@returns: The number of bytes read (NB: a value of 0 isn't necessarily an\n\
          error, check rand.status())\n\
";

static PyObject *
rand_egd(PyObject *spam, PyObject *args)
{
    char *path;
    int bytes = 255;

    if (!PyArg_ParseTuple(args, "s|i:egd", &path, &bytes))
        return NULL;

    return PyLong_FromLong((long)RAND_egd_bytes(path, bytes));
}

static char rand_cleanup_doc[] = "\n\
Erase the memory used by the PRNG.\n\
\n\
@return: None\n\
";

static PyObject *
rand_cleanup(PyObject *spam, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":cleanup"))
        return NULL;

    RAND_cleanup();

    Py_INCREF(Py_None);
    return Py_None;
}

static char rand_load_file_doc[] = "\n\
Seed the PRNG with data from a file\n\
\n\
@param filename: The file to read data from\n\
@param maxbytes: (optional) The number of bytes to read, default is\n\
                 to read the entire file\n\
@return: The number of bytes read\n\
";

static PyObject *
rand_load_file(PyObject *spam, PyObject *args)
{
    char *filename;
    int maxbytes = -1;

    if (!PyArg_ParseTuple(args, "s|i:load_file", &filename, &maxbytes))
        return NULL;

    return PyLong_FromLong((long)RAND_load_file(filename, maxbytes));
}

static char rand_write_file_doc[] = "\n\
Save PRNG state to a file\n\
\n\
@param filename: The file to write data to\n\
@return: The number of bytes written\n\
";

static PyObject *
rand_write_file(PyObject *spam, PyObject *args)
{
    char *filename;

    if (!PyArg_ParseTuple(args, "s:write_file", &filename))
        return NULL;

    return PyLong_FromLong((long)RAND_write_file(filename));
}

static char rand_bytes_doc[] = "\n\
Get some randomm bytes as a string.\n\
\n\
@param num_bytes: The number of bytes to fetch\n\
@return: A string of random bytes\n\
";

#if PY_VERSION_HEX < 0x02050000
#define Py_ssize_t int
#define PY_SSIZE_FMT "i"
#else
#define PY_SSIZE_FMT "n"
#endif

static PyObject *
rand_bytes(PyObject *spam, PyObject *args, PyObject *keywds) {
    Py_ssize_t num_bytes;
    static char *kwlist[] = {"num_bytes", NULL};
    char *buf;
    unsigned int rc;
    PyObject *obj = NULL;

    if (!PyArg_ParseTupleAndKeywords(
            args, keywds, PY_SSIZE_FMT ":bytes", kwlist, &num_bytes)) {
        return NULL;
    }

    if(num_bytes < 0) {
        PyErr_SetString(PyExc_ValueError, "num_bytes must not be negative");
        return NULL;
    }
    buf = malloc(num_bytes);
    if (buf == NULL)   /* out of memory  */
        return NULL;
    rc = RAND_bytes((unsigned char *) buf, num_bytes);
    if(rc != 1) {  /* if unsuccessful */
        exception_from_error_queue(rand_Error);
        goto done;
    }
    obj = PyBytes_FromStringAndSize(buf, (unsigned) num_bytes);
 done:
    free(buf);
    return obj;
}


/* Methods in the OpenSSL.rand module */
static PyMethodDef rand_methods[] = {
    { "add",       (PyCFunction)rand_add,          METH_VARARGS, rand_add_doc },
    { "seed",      (PyCFunction)rand_seed,         METH_VARARGS, rand_seed_doc },
    { "status",    (PyCFunction)rand_status,       METH_VARARGS, rand_status_doc },
#ifdef MS_WINDOWS
    { "screen",    (PyCFunction)rand_screen,       METH_VARARGS, rand_screen_doc },
#endif
    { "egd",       (PyCFunction)rand_egd,          METH_VARARGS, rand_egd_doc },
    { "cleanup",   (PyCFunction)rand_cleanup,      METH_VARARGS, rand_cleanup_doc },
    { "load_file", (PyCFunction)rand_load_file,    METH_VARARGS, rand_load_file_doc },
    { "write_file",(PyCFunction)rand_write_file,   METH_VARARGS, rand_write_file_doc },
    { "bytes",     (PyCFunction)rand_bytes,        METH_VARARGS|METH_KEYWORDS, rand_bytes_doc },
    { NULL, NULL }
};


#ifdef PY3
static struct PyModuleDef randmodule = {
    PyModuleDef_HEAD_INIT,
    "rand",
    rand_doc,
    -1,
    rand_methods
};
#endif

/*
 * Initialize the rand sub module
 *
 * Arguments: None
 * Returns:   None
 */
PyOpenSSL_MODINIT(rand) {
    PyObject *module;

#ifdef PY3
    module = PyModule_Create(&randmodule);
#else
    module = Py_InitModule3("rand", rand_methods, rand_doc);
#endif
    if (module == NULL) {
        PyOpenSSL_MODRETURN(NULL);
    }

    rand_Error = PyErr_NewException("OpenSSL.rand.Error", NULL, NULL);

    if (rand_Error == NULL) {
        goto error;
    }

    /* PyModule_AddObject steals a reference.
     */
    Py_INCREF(rand_Error);
    if (PyModule_AddObject(module, "Error", rand_Error) != 0) {
        goto error;
    }

    ERR_load_RAND_strings();

    PyOpenSSL_MODRETURN(module);

error:
    PyOpenSSL_MODRETURN(NULL);
    ;
}