Mercurial > vim
changeset 18703:aef98a646d3e v8.1.2343
patch 8.1.2343: using time() for srand() is not very random
Commit: https://github.com/vim/vim/commit/07e4a197953d12902fb97beb48830a5323a52280
Author: Bram Moolenaar <Bram@vim.org>
Date: Tue Nov 26 12:23:30 2019 +0100
patch 8.1.2343: using time() for srand() is not very random
Problem: Using time() for srand() is not very random.
Solution: use /dev/urandom if available
| author | Bram Moolenaar <Bram@vim.org> |
|---|---|
| date | Tue, 26 Nov 2019 12:30:04 +0100 |
| parents | fd7bbf832d8f |
| children | 65e3c91819fe |
| files | src/evalfunc.c src/testdir/test_random.vim src/version.c |
| diffstat | 3 files changed, 50 insertions(+), 5 deletions(-) [+] |
line wrap: on
line diff
--- a/src/evalfunc.c +++ b/src/evalfunc.c @@ -7095,10 +7095,45 @@ f_sqrt(typval_T *argvars, typval_T *rett 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) - list_append_number(rettv->vval.v_list, (varnumber_T)vim_time()); + { + 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; @@ -7107,7 +7142,7 @@ f_srand(typval_T *argvars, typval_T *ret if (error) return; - list_append_number(rettv->vval.v_list, x); + 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);
--- a/src/testdir/test_random.vim +++ b/src/testdir/test_random.vim @@ -11,9 +11,15 @@ func Test_Rand() call test_settime(12341234) let s = srand() - call assert_equal(s, srand()) - call test_settime(12341235) - call assert_notequal(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() @@ -25,4 +31,6 @@ func Test_Rand() 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