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s4 librpc rpc pyrpc: Ensure tevent_context deleted last

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Ensure that the tevent_context is deleted after the connection, to
prevent a use after free.

Note: Py_DECREF calls dcerpc_interface_dealloc so the
TALLOC_FREE(ret->mem_ctx) calls in the error paths of
py_dcerpc_interface_init_helper needed removal.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=13932

Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
This commit is contained in:
Gary Lockyer 2019-05-08 11:30:20 +12:00 committed by Andrew Bartlett
parent 165025a56e
commit d65b7641c8
3 changed files with 39 additions and 28 deletions
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18
source4/librpc/rpc/pyrpc.c
View File

@ -300,9 +300,27 @@ static PyMethodDef dcerpc_interface_methods[] = {
static void dcerpc_interface_dealloc(PyObject* self)
{
dcerpc_InterfaceObject *interface = (dcerpc_InterfaceObject *)self;
/*
* This can't fail, and if it did talloc_unlink(NULL, NULL) is
* harmless below
*/
struct tevent_context *ev_save = talloc_reparent(
NULL, interface->mem_ctx, interface->ev);
interface->binding_handle = NULL;
interface->pipe = NULL;
/*
* Free everything *except* the event context, which must go
* away last
*/
TALLOC_FREE(interface->mem_ctx);
/*
* Now wish a fond goodbye to the event context itself
*/
talloc_unlink(NULL, ev_save);
self->ob_type->tp_free(self);
}

1
source4/librpc/rpc/pyrpc.h
View File

@ -49,6 +49,7 @@ typedef struct {
TALLOC_CTX *mem_ctx;
struct dcerpc_pipe *pipe;
struct dcerpc_binding_handle *binding_handle;
struct tevent_context *ev;
} dcerpc_InterfaceObject;

48
source4/librpc/rpc/pyrpc_util.c
View File

@ -123,6 +123,7 @@ PyObject *py_dcerpc_interface_init_helper(PyTypeObject *type, PyObject *args, Py
ret->pipe = NULL;
ret->binding_handle = NULL;
ret->ev = NULL;
ret->mem_ctx = talloc_new(NULL);
if (ret->mem_ctx == NULL) {
PyErr_NoMemory();
@ -130,30 +131,26 @@ PyObject *py_dcerpc_interface_init_helper(PyTypeObject *type, PyObject *args, Py
}
if (strncmp(binding_string, "irpc:", 5) == 0) {
struct tevent_context *event_ctx;
struct loadparm_context *lp_ctx;
event_ctx = s4_event_context_init(ret->mem_ctx);
if (event_ctx == NULL) {
ret->ev = s4_event_context_init(ret->mem_ctx);
if (ret->ev == NULL) {
PyErr_SetString(PyExc_TypeError, "Expected loadparm context");
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
return NULL;
}
lp_ctx = lpcfg_from_py_object(event_ctx, py_lp_ctx);
lp_ctx = lpcfg_from_py_object(ret->ev, py_lp_ctx);
if (lp_ctx == NULL) {
PyErr_SetString(PyExc_TypeError, "Expected loadparm context");
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
return NULL;
}
status = pyrpc_irpc_connect(ret->mem_ctx, binding_string+5, table,
event_ctx, lp_ctx, &ret->binding_handle);
ret->ev, lp_ctx, &ret->binding_handle);
if (!NT_STATUS_IS_OK(status)) {
PyErr_SetNTSTATUS(status);
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
return NULL;
}
@ -164,7 +161,6 @@ PyObject *py_dcerpc_interface_init_helper(PyTypeObject *type, PyObject *args, Py
py_base = PyImport_ImportModule("samba.dcerpc.base");
if (py_base == NULL) {
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
return NULL;
}
@ -172,7 +168,6 @@ PyObject *py_dcerpc_interface_init_helper(PyTypeObject *type, PyObject *args, Py
ClientConnection_Type = (PyTypeObject *)PyObject_GetAttrString(py_base, "ClientConnection");
if (ClientConnection_Type == NULL) {
PyErr_SetNone(PyExc_TypeError);
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
Py_DECREF(py_base);
return NULL;
@ -180,7 +175,6 @@ PyObject *py_dcerpc_interface_init_helper(PyTypeObject *type, PyObject *args, Py
if (!PyObject_TypeCheck(py_basis, ClientConnection_Type)) {
PyErr_SetString(PyExc_TypeError, "basis_connection must be a DCE/RPC connection");
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
Py_DECREF(py_base);
Py_DECREF(ClientConnection_Type);
@ -191,7 +185,17 @@ PyObject *py_dcerpc_interface_init_helper(PyTypeObject *type, PyObject *args, Py
((dcerpc_InterfaceObject *)py_basis)->pipe);
if (base_pipe == NULL) {
PyErr_NoMemory();
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
Py_DECREF(py_base);
Py_DECREF(ClientConnection_Type);
return NULL;
}
ret->ev = talloc_reference(
ret->mem_ctx,
((dcerpc_InterfaceObject *)py_basis)->ev);
if (ret->ev == NULL) {
PyErr_NoMemory();
Py_DECREF(ret);
Py_DECREF(py_base);
Py_DECREF(ClientConnection_Type);
@ -201,7 +205,6 @@ PyObject *py_dcerpc_interface_init_helper(PyTypeObject *type, PyObject *args, Py
status = dcerpc_secondary_context(base_pipe, &ret->pipe, table);
if (!NT_STATUS_IS_OK(status)) {
PyErr_SetNTSTATUS(status);
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
Py_DECREF(py_base);
Py_DECREF(ClientConnection_Type);
@ -212,22 +215,19 @@ PyObject *py_dcerpc_interface_init_helper(PyTypeObject *type, PyObject *args, Py
Py_XDECREF(ClientConnection_Type);
Py_XDECREF(py_base);
} else {
struct tevent_context *event_ctx;
struct loadparm_context *lp_ctx;
struct cli_credentials *credentials;
event_ctx = s4_event_context_init(ret->mem_ctx);
if (event_ctx == NULL) {
ret->ev = s4_event_context_init(ret->mem_ctx);
if (ret->ev == NULL) {
PyErr_SetString(PyExc_TypeError, "Expected loadparm context");
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
return NULL;
}
lp_ctx = lpcfg_from_py_object(event_ctx, py_lp_ctx);
lp_ctx = lpcfg_from_py_object(ret->ev, py_lp_ctx);
if (lp_ctx == NULL) {
PyErr_SetString(PyExc_TypeError, "Expected loadparm context");
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
return NULL;
}
@ -235,24 +235,16 @@ PyObject *py_dcerpc_interface_init_helper(PyTypeObject *type, PyObject *args, Py
credentials = cli_credentials_from_py_object(py_credentials);
if (credentials == NULL) {
PyErr_SetString(PyExc_TypeError, "Expected credentials");
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
return NULL;
}
status = dcerpc_pipe_connect(ret->mem_ctx, &ret->pipe, binding_string,
table, credentials, event_ctx, lp_ctx);
table, credentials, ret->ev, lp_ctx);
if (!NT_STATUS_IS_OK(status)) {
PyErr_SetNTSTATUS(status);
TALLOC_FREE(ret->mem_ctx);
Py_DECREF(ret);
return NULL;
}
/*
* the event context is cached under the connection,
* so let it be a child of it.
*/
talloc_steal(ret->pipe->conn, event_ctx);
}
if (ret->pipe) {