# HG changeset patch

# User Benjamin Peterson <benjamin@python.org>

# Date 1409243400 14400

# Node ID 3e7f8855078855a9409bc2c1372de89cb021d6c8

# Parent  3f73c44b1fd1d442d6841493328e9756fb5e7ef5

PEP 466: backport persistent urandom fd (closes #21305)

Patch from Alex Gaynor.

diff --git a/Python/pythonrun.c b/Python/pythonrun.c

--- a/Python/pythonrun.c

+++ b/Python/pythonrun.c

@@ -536,6 +536,7 @@ Py_Finalize(void)

     PyInt_Fini();

     PyFloat_Fini();

     PyDict_Fini();

+    _PyRandom_Fini();

 #ifdef Py_USING_UNICODE

     /* Cleanup Unicode implementation */

diff -up Python-2.7.5/Include/pythonrun.h.urandom Python-2.7.5/Include/pythonrun.h

--- Python-2.7.5/Include/pythonrun.h.urandom	2015-03-06 08:16:47.638584015 +0100

+++ Python-2.7.5/Include/pythonrun.h	2015-03-06 08:21:48.009485462 +0100

@@ -145,6 +145,7 @@ PyAPI_FUNC(void) PyInt_Fini(void);

 PyAPI_FUNC(void) PyFloat_Fini(void);

 PyAPI_FUNC(void) PyOS_FiniInterrupts(void);

 PyAPI_FUNC(void) PyByteArray_Fini(void);

+PyAPI_FUNC(void) _PyRandom_Fini(void);

 /* Stuff with no proper home (yet) */

 PyAPI_FUNC(char *) PyOS_Readline(FILE *, FILE *, char *);

diff -up Python-2.7.5/Python/random.c.urandom Python-2.7.5/Python/random.c

--- Python-2.7.5/Python/random.c.urandom	2015-03-06 08:22:10.244699950 +0100

+++ Python-2.7.5/Python/random.c	2015-03-06 08:24:57.907317272 +0100

@@ -118,10 +118,16 @@ vms_urandom(unsigned char *buffer, Py_ss

 #if !defined(MS_WINDOWS) && !defined(__VMS)

+static struct {

+    int fd;

+    dev_t st_dev;

+    ino_t st_ino;

+} urandom_cache = { -1 };

+

 /* Read size bytes from /dev/urandom into buffer.

    Call Py_FatalError() on error. */

 static void

-dev_urandom_noraise(char *buffer, Py_ssize_t size)

+dev_urandom_noraise(unsigned char *buffer, Py_ssize_t size)

 {

     int fd;

     Py_ssize_t n;

@@ -156,18 +162,56 @@ dev_urandom_python(char *buffer, Py_ssiz

 {

     int fd;

     Py_ssize_t n;

+    struct stat st;

     if (size <= 0)

         return 0;

-    Py_BEGIN_ALLOW_THREADS

-    fd = open("/dev/urandom", O_RDONLY);

-    Py_END_ALLOW_THREADS

-    if (fd < 0)

-    {

-        PyErr_SetString(PyExc_NotImplementedError,

-                        "/dev/urandom (or equivalent) not found");

-        return -1;

+    if (urandom_cache.fd >= 0) {

+        /* Does the fd point to the same thing as before? (issue #21207) */

+        if (fstat(urandom_cache.fd, &st)

+            || st.st_dev != urandom_cache.st_dev

+            || st.st_ino != urandom_cache.st_ino) {

+            /* Something changed: forget the cached fd (but don't close it,

+               since it probably points to something important for some

+               third-party code). */

+            urandom_cache.fd = -1;

+        }

+    }

+    if (urandom_cache.fd >= 0)

+        fd = urandom_cache.fd;

+    else {

+        Py_BEGIN_ALLOW_THREADS

+        fd = open("/dev/urandom", O_RDONLY);

+        Py_END_ALLOW_THREADS

+        if (fd < 0)

+        {

+            if (errno == ENOENT || errno == ENXIO ||

+                errno == ENODEV || errno == EACCES)

+                PyErr_SetString(PyExc_NotImplementedError,

+                                "/dev/urandom (or equivalent) not found");

+            else

+                PyErr_SetFromErrno(PyExc_OSError);

+            return -1;

+        }

+        if (urandom_cache.fd >= 0) {

+            /* urandom_fd was initialized by another thread while we were

+               not holding the GIL, keep it. */

+            close(fd);

+            fd = urandom_cache.fd;

+        }

+        else {

+            if (fstat(fd, &st)) {

+                PyErr_SetFromErrno(PyExc_OSError);

+                close(fd);

+                return -1;

+            }

+            else {

+                urandom_cache.fd = fd;

+                urandom_cache.st_dev = st.st_dev;

+                urandom_cache.st_ino = st.st_ino;

+            }

+        }

     }

     Py_BEGIN_ALLOW_THREADS

@@ -191,12 +235,21 @@ dev_urandom_python(char *buffer, Py_ssiz

             PyErr_Format(PyExc_RuntimeError,

                          "Failed to read %zi bytes from /dev/urandom",

                          size);

-        close(fd);

         return -1;

     }

-    close(fd);

     return 0;

 }

+

+static void

+dev_urandom_close(void)

+{

+    if (urandom_cache.fd >= 0) {

+        close(urandom_cache.fd);

+        urandom_cache.fd = -1;

+    }

+}

+

+

 #endif /* !defined(MS_WINDOWS) && !defined(__VMS) */

 /* Fill buffer with pseudo-random bytes generated by a linear congruent

@@ -300,8 +353,21 @@ _PyRandom_Init(void)

 # ifdef __VMS

         vms_urandom((unsigned char *)secret, secret_size, 0);

 # else

-        dev_urandom_noraise((char*)secret, secret_size);

+        dev_urandom_noraise((unsigned char*)secret, secret_size);

 # endif

 #endif

     }

 }

+

+void

+_PyRandom_Fini(void)

+{

+#ifdef MS_WINDOWS

+    if (hCryptProv) {

+        CryptReleaseContext(hCryptProv, 0);

+        hCryptProv = 0;

+    }

+#else

+    dev_urandom_close();

+#endif

+}