To: vim_dev@googlegroups.com
Subject: Patch 8.1.2343
Fcc: outbox
From: Bram Moolenaar <Bram@moolenaar.net>
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------------

Patch 8.1.2343
Problem:    Using time() for srand() is not very random.
Solution:   use /dev/urandom if available
Files:	    src/evalfunc.c, src/testdir/test_random.vim


*** ../vim-8.1.2342/src/evalfunc.c	2019-11-25 15:40:28.849612230 +0100
--- src/evalfunc.c	2019-11-26 12:14:53.058068739 +0100
***************
*** 7095,7104 ****
      static void
  f_srand(typval_T *argvars, typval_T *rettv)
  {
      if (rettv_list_alloc(rettv) == FAIL)
  	return;
      if (argvars[0].v_type == VAR_UNKNOWN)
! 	list_append_number(rettv->vval.v_list, (varnumber_T)vim_time());
      else
      {
  	int	    error = FALSE;
--- 7095,7139 ----
      static void
  f_srand(typval_T *argvars, typval_T *rettv)
  {
+     static int dev_urandom_state = -1;  // FAIL or OK once tried
+ 
      if (rettv_list_alloc(rettv) == FAIL)
  	return;
      if (argvars[0].v_type == VAR_UNKNOWN)
!     {
! 	if (dev_urandom_state != FAIL)
! 	{
! 	    int  fd = open("/dev/urandom", O_RDONLY);
! 	    struct {
! 		union {
! 		    UINT32_T number;
! 		    char     bytes[sizeof(UINT32_T)];
! 		} cont;
! 	    } buf;
! 
! 	    // Attempt reading /dev/urandom.
! 	    if (fd == -1)
! 		dev_urandom_state = FAIL;
! 	    else
! 	    {
! 		buf.cont.number = 0;
! 		if (read(fd, buf.cont.bytes, sizeof(UINT32_T))
! 							   != sizeof(UINT32_T))
! 		    dev_urandom_state = FAIL;
! 		else
! 		{
! 		    dev_urandom_state = OK;
! 		    list_append_number(rettv->vval.v_list,
! 						 (varnumber_T)buf.cont.number);
! 		}
! 		close(fd);
! 	    }
! 
! 	}
! 	if (dev_urandom_state != OK)
! 	    // Reading /dev/urandom doesn't work, fall back to time().
! 	    list_append_number(rettv->vval.v_list, (varnumber_T)vim_time());
!     }
      else
      {
  	int	    error = FALSE;
***************
*** 7107,7113 ****
  	if (error)
  	    return;
  
! 	list_append_number(rettv->vval.v_list, x);
      }
      list_append_number(rettv->vval.v_list, 362436069);
      list_append_number(rettv->vval.v_list, 521288629);
--- 7142,7148 ----
  	if (error)
  	    return;
  
! 	list_append_number(rettv->vval.v_list, (varnumber_T)x);
      }
      list_append_number(rettv->vval.v_list, 362436069);
      list_append_number(rettv->vval.v_list, 521288629);
*** ../vim-8.1.2342/src/testdir/test_random.vim	2019-11-25 15:40:28.853612211 +0100
--- src/testdir/test_random.vim	2019-11-26 12:21:15.508414423 +0100
***************
*** 11,19 ****
  
    call test_settime(12341234)
    let s = srand()
!   call assert_equal(s, srand())
!   call test_settime(12341235)
!   call assert_notequal(s, srand())
  
    call srand()
    let v = rand()
--- 11,25 ----
  
    call test_settime(12341234)
    let s = srand()
!   if filereadable('/dev/urandom')
!     " using /dev/urandom
!     call assert_notequal(s, srand())
!   else
!     " using time()
!     call assert_equal(s, srand())
!     call test_settime(12341235)
!     call assert_notequal(s, srand())
!   endif
  
    call srand()
    let v = rand()
***************
*** 25,28 ****
--- 31,36 ----
    call assert_fails('echo rand([1, [2], 3, 4])', 'E475:')
    call assert_fails('echo rand([1, 2, [3], 4])', 'E475:')
    call assert_fails('echo rand([1, 2, 3, [4]])', 'E475:')
+ 
+   call test_settime(0)
  endfunc
*** ../vim-8.1.2342/src/version.c	2019-11-25 15:40:28.853612211 +0100
--- src/version.c	2019-11-26 12:22:24.704102512 +0100
***************
*** 739,740 ****
--- 739,742 ----
  {   /* Add new patch number below this line */
+ /**/
+     2343,
  /**/

-- 
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 /// Bram Moolenaar -- Bram@Moolenaar.net -- http://www.Moolenaar.net   \\\
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