view mercurial/thirdparty/sha1dc/cext.c @ 46779:49fd21f32695

revlog: guarantee that p1 != null if a non-null parent exists

This change does not affect the hashing (which already did this
transformation), but can change the log output in the rare case where
this behavior was observed in repositories. The change can simplify
iteration code where regular changesets and merges are distinct
branches.

Differential Revision: https://phab.mercurial-scm.org/D10150

#define PY_SSIZE_T_CLEAN
#include <Python.h>

#include "lib/sha1.h"

#if PY_MAJOR_VERSION >= 3
#define IS_PY3K
#endif

/* helper to switch things like string literal depending on Python version */
#ifdef IS_PY3K
#define PY23(py2, py3) py3
#else
#define PY23(py2, py3) py2
#endif

static char sha1dc_doc[] = "Efficient detection of SHA1 collision constructs.";

/* clang-format off */
typedef struct {
	PyObject_HEAD
	SHA1_CTX ctx;
} pysha1ctx;
/* clang-format on */

static int pysha1ctx_init(pysha1ctx *self, PyObject *args)
{
	Py_buffer data;
	data.obj = NULL;

	SHA1DCInit(&(self->ctx));
	/* We don't want "safe" sha1s, wherein sha1dc can give you a
	   different hash for something that's trying to give you a
	   collision. We just want to detect collisions.
	 */
	SHA1DCSetSafeHash(&(self->ctx), 0);
	if (!PyArg_ParseTuple(args, PY23("|s*", "|y*"), &data)) {
		return -1;
	}
	if (data.obj) {
		if (!PyBuffer_IsContiguous(&data, 'C') || data.ndim > 1) {
			PyErr_SetString(PyExc_BufferError,
			                "buffer must be contiguous and single dimension");
			PyBuffer_Release(&data);
			return -1;
		}

		SHA1DCUpdate(&(self->ctx), data.buf, data.len);
		PyBuffer_Release(&data);
	}
	return 0;
}

static void pysha1ctx_dealloc(pysha1ctx *self)
{
	PyObject_Del(self);
}

static PyObject *pysha1ctx_update(pysha1ctx *self, PyObject *args)
{
	Py_buffer data;
	if (!PyArg_ParseTuple(args, PY23("s*", "y*"), &data)) {
		return NULL;
	}
	if (!PyBuffer_IsContiguous(&data, 'C') || data.ndim > 1) {
		PyErr_SetString(PyExc_BufferError,
		                "buffer must be contiguous and single dimension");
		PyBuffer_Release(&data);
		return NULL;
	}
	SHA1DCUpdate(&(self->ctx), data.buf, data.len);
	PyBuffer_Release(&data);
	Py_RETURN_NONE;
}

/* it is intentional that this take a ctx by value, as that clones the
   context so we can keep using .update() without poisoning the state
   with padding.
*/
static int finalize(SHA1_CTX ctx, unsigned char *hash_out)
{
	if (SHA1DCFinal(hash_out, &ctx)) {
		PyErr_SetString(PyExc_OverflowError,
		                "sha1 collision attack detected");
		return 0;
	}
	return 1;
}

static PyObject *pysha1ctx_digest(pysha1ctx *self)
{
	unsigned char hash[20];
	if (!finalize(self->ctx, hash)) {
		return NULL;
	}
	return PyBytes_FromStringAndSize((char *)hash, 20);
}

static PyObject *pysha1ctx_hexdigest(pysha1ctx *self)
{
	static const char hexdigit[] = "0123456789abcdef";
	unsigned char hash[20];
	char hexhash[40];
	int i;
	if (!finalize(self->ctx, hash)) {
		return NULL;
	}
	for (i = 0; i < 20; ++i) {
		hexhash[i * 2] = hexdigit[hash[i] >> 4];
		hexhash[i * 2 + 1] = hexdigit[hash[i] & 15];
	}
	return PY23(PyString_FromStringAndSize, PyUnicode_FromStringAndSize)(hexhash, 40);
}

static PyTypeObject sha1ctxType;

static PyObject *pysha1ctx_copy(pysha1ctx *self)
{
	pysha1ctx *clone = (pysha1ctx *)PyObject_New(pysha1ctx, &sha1ctxType);
	if (!clone) {
		return NULL;
	}
	clone->ctx = self->ctx;
	return (PyObject *)clone;
}

static PyMethodDef pysha1ctx_methods[] = {
    {"update", (PyCFunction)pysha1ctx_update, METH_VARARGS,
     "Update this hash object's state with the provided bytes."},
    {"digest", (PyCFunction)pysha1ctx_digest, METH_NOARGS,
     "Return the digest value as a string of binary data."},
    {"hexdigest", (PyCFunction)pysha1ctx_hexdigest, METH_NOARGS,
     "Return the digest value as a string of hexadecimal digits."},
    {"copy", (PyCFunction)pysha1ctx_copy, METH_NOARGS,
     "Return a copy of the hash object."},
    {NULL},
};

/* clang-format off */
static PyTypeObject sha1ctxType = {
	PyVarObject_HEAD_INIT(NULL, 0)                    /* header */
	"sha1dc.sha1",                                    /* tp_name */
	sizeof(pysha1ctx),                                /* tp_basicsize */
	0,                                                /* tp_itemsize */
	(destructor)pysha1ctx_dealloc,                    /* tp_dealloc */
	0,                                                /* tp_print */
	0,                                                /* tp_getattr */
	0,                                                /* tp_setattr */
	0,                                                /* tp_compare */
	0,                                                /* tp_repr */
	0,                                                /* tp_as_number */
	0,                                                /* tp_as_sequence */
	0,                                                /* tp_as_mapping */
	0,                                                /* tp_hash */
	0,                                                /* tp_call */
	0,                                                /* tp_str */
	0,                                                /* tp_getattro */
	0,                                                /* tp_setattro */
	0,                                                /* tp_as_buffer */
	Py_TPFLAGS_DEFAULT,                               /* tp_flags */
	"sha1 implementation that looks for collisions",  /* tp_doc */
	0,                                                /* tp_traverse */
	0,                                                /* tp_clear */
	0,                                                /* tp_richcompare */
	0,                                                /* tp_weaklistoffset */
	0,                                                /* tp_iter */
	0,                                                /* tp_iternext */
	pysha1ctx_methods,                                /* tp_methods */
	0,                                                /* tp_members */
	0,                                                /* tp_getset */
	0,                                                /* tp_base */
	0,                                                /* tp_dict */
	0,                                                /* tp_descr_get */
	0,                                                /* tp_descr_set */
	0,                                                /* tp_dictoffset */
	(initproc)pysha1ctx_init,                         /* tp_init */
	0,                                                /* tp_alloc */
};
/* clang-format on */

static PyMethodDef methods[] = {
    {NULL, NULL},
};

static void module_init(PyObject *mod)
{
	sha1ctxType.tp_new = PyType_GenericNew;
	if (PyType_Ready(&sha1ctxType) < 0) {
		return;
	}
	Py_INCREF(&sha1ctxType);

	PyModule_AddObject(mod, "sha1", (PyObject *)&sha1ctxType);
}

#ifdef IS_PY3K
static struct PyModuleDef sha1dc_module = {PyModuleDef_HEAD_INIT, "sha1dc",
                                           sha1dc_doc, -1, methods};

PyMODINIT_FUNC PyInit_sha1dc(void)
{
	PyObject *mod = PyModule_Create(&sha1dc_module);
	module_init(mod);
	return mod;
}
#else
PyMODINIT_FUNC initsha1dc(void)
{
	PyObject *mod = Py_InitModule3("sha1dc", methods, sha1dc_doc);
	module_init(mod);
}
#endif