Issue #5753: A new C API function, :cfunc:`PySys_SetArgvEx`, allows

embedders of the interpreter to set sys.argv without also modifying
sys.path.  This helps fix `CVE-2008-5983
<http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983>`_.

Doc/c-api/init.rst

@@ -22,6 +22,7 @@ Initialization, Finalization, and Threads
       module: sys
       triple: module; search; path
       single: PySys_SetArgv()
+      single: PySys_SetArgvEx()
       single: Py_Finalize()
 
    Initialize the Python interpreter.  In an application embedding  Python, this
@@ -31,7 +32,7 @@ Initialization, Finalization, and Threads
    the table of loaded modules (``sys.modules``), and creates the fundamental
    modules :mod:`__builtin__`, :mod:`__main__` and :mod:`sys`.  It also initializes
    the module search path (``sys.path``). It does not set ``sys.argv``; use
-   :cfunc:`PySys_SetArgv` for that.  This is a no-op when called for a second time
+   :cfunc:`PySys_SetArgvEx` for that.  This is a no-op when called for a second time
    (without calling :cfunc:`Py_Finalize` first).  There is no return value; it is a
    fatal error if the initialization fails.
 
@@ -338,7 +339,7 @@ Initialization, Finalization, and Threads
    ``sys.version``.
 
 
-.. cfunction:: void PySys_SetArgv(int argc, char **argv)
+.. cfunction:: void PySys_SetArgvEx(int argc, char **argv, int updatepath)
 
    .. index::
       single: main()
@@ -353,14 +354,41 @@ Initialization, Finalization, and Threads
    string.  If this function fails to initialize :data:`sys.argv`, a fatal
    condition is signalled using :cfunc:`Py_FatalError`.
 
-   This function also prepends the executed script's path to :data:`sys.path`.
-   If no script is executed (in the case of calling ``python -c`` or just the
-   interactive interpreter), the empty string is used instead.
+   If *updatepath* is zero, this is all the function does.  If *updatepath*
+   is non-zero, the function also modifies :data:`sys.path` according to the
+   following algorithm:
+
+   - If the name of an existing script is passed in ``argv[0]``, the absolute
+     path of the directory where the script is located is prepended to
+     :data:`sys.path`.
+   - Otherwise (that is, if *argc* is 0 or ``argv[0]`` doesn't point
+     to an existing file name), an empty string is prepended to
+     :data:`sys.path`, which is the same as prepending the current working
+     directory (``"."``).
+
+   .. note::
+      It is recommended that applications embedding the Python interpreter
+      for purposes other than executing a single script pass 0 as *updatepath*,
+      and update :data:`sys.path` themselves if desired.
+      See `CVE-2008-5983 <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983>`_.
+
+      On versions before 2.6.6, you can achieve the same effect by manually
+      popping the first :data:`sys.path` element after having called
+      :cfunc:`PySys_SetArgv`, for example using::
+
+         PyRun_SimpleString("import sys; sys.path.pop(0)\n");
+
+   .. versionadded:: 2.6.6
 
    .. XXX impl. doesn't seem consistent in allowing 0/NULL for the params;
       check w/ Guido.
 
 
+.. cfunction:: void PySys_SetArgv(int argc, char **argv)
+
+   This function works like :cfunc:`PySys_SetArgv` with *updatepath* set to 1.
+
+
 .. cfunction:: void Py_SetPythonHome(char *home)
 
    Set the default "home" directory, that is, the location of the standard

Include/sysmodule.h

@@ -11,6 +11,7 @@ PyAPI_FUNC(PyObject *) PySys_GetObject(char *);
 PyAPI_FUNC(int) PySys_SetObject(char *, PyObject *);
 PyAPI_FUNC(FILE *) PySys_GetFile(char *, FILE *);
 PyAPI_FUNC(void) PySys_SetArgv(int, char **);
+PyAPI_FUNC(void) PySys_SetArgvEx(int, char **, int);
 PyAPI_FUNC(void) PySys_SetPath(char *);
 
 PyAPI_FUNC(void) PySys_WriteStdout(const char *format, ...)

Misc/NEWS

@@ -18,6 +18,14 @@ Core and Builtins
 - Issue #7079: Fix a possible crash when closing a file object while using
   it from another thread.  Patch by Daniel Stutzbach.
 
+C-API
+-----
+
+- Issue #5753: A new C API function, :cfunc:`PySys_SetArgvEx`, allows
+  embedders of the interpreter to set sys.argv without also modifying
+  sys.path.  This helps fix `CVE-2008-5983
+  <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983>`_.
+
 Library
 -------
 

Python/sysmodule.c

@@ -1649,7 +1649,7 @@ makeargvobject(int argc, char **argv)
 }
 
 void
-PySys_SetArgv(int argc, char **argv)
+PySys_SetArgvEx(int argc, char **argv, int updatepath)
 {
 #if defined(HAVE_REALPATH)
     char fullpath[MAXPATHLEN];
@@ -1662,7 +1662,7 @@ PySys_SetArgv(int argc, char **argv)
         Py_FatalError("no mem for sys.argv");
     if (PySys_SetObject("argv", av) != 0)
         Py_FatalError("can't assign sys.argv");
-    if (path != NULL) {
+    if (updatepath && path != NULL) {
         char *argv0 = argv[0];
         char *p = NULL;
         Py_ssize_t n = 0;
@@ -1752,6 +1752,12 @@ PySys_SetArgv(int argc, char **argv)
     Py_DECREF(av);
 }
 
+void
+PySys_SetArgv(int argc, char **argv)
+{
+    PySys_SetArgvEx(argc, argv, 1);
+}
+
 
 /* APIs to write to sys.stdout or sys.stderr using a printf-like interface.
    Adapted from code submitted by Just van Rossum.