From c62ff2800ba9e4b6e851ae71b1696b28920854b9 Mon Sep 17 00:00:00 2001
From: Conrad Meyer <cem@FreeBSD.org>
Date: Sat, 14 Dec 2019 08:28:10 +0000
Subject: Deprecate sranddev(3) API

It serves no useful purpose and wasn't as popular as its equally meritless
cousin, srandomdev(3).

Setting aside the problems with rand(3) in general, the problem with this
interface is that the seed isn't shared with the caller (other than by
attacking the output of the generator, which is trivial, but not a hallmark of
pleasant API design).  The (arguable) utility of rand(3) or random(3) is as a
semi-fast simulation generator which produces consistent results from a given
seed.  These are mutually at odd.  Furthermore, sometimes people got the
mistaken impression that a high quality random seed meant a weak generator like
rand(3) or random(3) could be used for things like cryptographic key
generation.  This is absolutely not so.

The API was never part of a standard and was not widely used in tree.  Existing
in-tree uses have all been removed.

Possible replacement in out of tree codebases:

	char buf[3];
	time_t t;

	time(t);
	strftime(buf, sizeof(buf), "%S", gmtime(&t));
	srand(atoi(buf));

Relnotes:	yes
---
 lib/libc/stdlib/Makefile.inc |  2 +-
 lib/libc/stdlib/Symbol.map   |  1 -
 lib/libc/stdlib/rand.3       | 12 +++---------
 lib/libc/stdlib/rand.c       | 25 ++++++++++---------------
 4 files changed, 14 insertions(+), 26 deletions(-)

(limited to 'lib/libc/stdlib')

diff --git a/lib/libc/stdlib/Makefile.inc b/lib/libc/stdlib/Makefile.inc
index ee6d98e9cf6a9..1a44306973856 100644
--- a/lib/libc/stdlib/Makefile.inc
+++ b/lib/libc/stdlib/Makefile.inc
@@ -52,7 +52,7 @@ MLINKS+=insque.3 remque.3
 MLINKS+=lsearch.3 lfind.3
 MLINKS+=ptsname.3 grantpt.3 ptsname.3 unlockpt.3
 MLINKS+=qsort.3 heapsort.3 qsort.3 mergesort.3 qsort.3 qsort_r.3
-MLINKS+=rand.3 rand_r.3 rand.3 srand.3 rand.3 sranddev.3
+MLINKS+=rand.3 rand_r.3 rand.3 srand.3
 MLINKS+=random.3 initstate.3 random.3 setstate.3 random.3 srandom.3 \
 	random.3 srandomdev.3
 MLINKS+=radixsort.3 sradixsort.3
diff --git a/lib/libc/stdlib/Symbol.map b/lib/libc/stdlib/Symbol.map
index 8682901bca6df..d25b463241d7f 100644
--- a/lib/libc/stdlib/Symbol.map
+++ b/lib/libc/stdlib/Symbol.map
@@ -56,7 +56,6 @@ FBSD_1.0 {
 	rand_r;
 	rand;
 	srand;
-	sranddev;
 	srandom;
 	srandomdev;
 	initstate;
diff --git a/lib/libc/stdlib/rand.3 b/lib/libc/stdlib/rand.3
index ce3bae730a889..04de06ae48847 100644
--- a/lib/libc/stdlib/rand.3
+++ b/lib/libc/stdlib/rand.3
@@ -32,13 +32,12 @@
 .\"     @(#)rand.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd April 22, 2019
+.Dd December 14, 2019
 .Dt RAND 3
 .Os
 .Sh NAME
 .Nm rand ,
 .Nm srand ,
-.Nm sranddev ,
 .Nm rand_r
 .Nd bad random number generator
 .Sh LIBRARY
@@ -47,8 +46,6 @@
 .In stdlib.h
 .Ft void
 .Fn srand "unsigned seed"
-.Ft void
-.Fn sranddev void
 .Ft int
 .Fn rand void
 .Ft int
@@ -90,10 +87,6 @@ value is provided, the functions are automatically
 seeded with a value of 1.
 .Pp
 The
-.Fn sranddev
-function initializes a seed using pseudo-random numbers obtained from the kernel.
-.Pp
-The
 .Fn rand_r
 function
 provides the same functionality as
@@ -122,4 +115,5 @@ conform to
 .Pp
 The
 .Fn rand_r
-function is as proposed in the POSIX.4a Draft #6 document.
+function is marked as obsolescent in POSIX and may be removed in a future
+revision of the standard.
diff --git a/lib/libc/stdlib/rand.c b/lib/libc/stdlib/rand.c
index be2c3d4f058b6..3722e850549c4 100644
--- a/lib/libc/stdlib/rand.c
+++ b/lib/libc/stdlib/rand.c
@@ -40,7 +40,9 @@ __FBSDID("$FreeBSD$");
 #include "namespace.h"
 #include <sys/param.h>
 #include <sys/sysctl.h>
+#include <stdbool.h>
 #include <stdlib.h>
+#include <syslog.h>
 #include "un-namespace.h"
 
 #ifdef TEST
@@ -102,25 +104,18 @@ srand(unsigned seed)
 }
 
 
-/*
- * sranddev:
- *
- * Many programs choose the seed value in a totally predictable manner.
- * This often causes problems.  We seed the generator using pseudo-random
- * data from the kernel.
- */
+void __sranddev_fbsd12(void);
 void
-sranddev(void)
+__sranddev_fbsd12(void)
 {
-	int mib[2];
-	size_t len;
-
-	len = sizeof(next);
+	static bool warned = false;
 
-	mib[0] = CTL_KERN;
-	mib[1] = KERN_ARND;
-	sysctl(mib, 2, (void *)&next, &len, NULL, 0);
+	if (!warned) {
+		syslog(LOG_DEBUG, "Deprecated function sranddev() called");
+		warned = true;
+	}
 }
+__sym_compat(sranddev, __sranddev_fbsd12, FBSD_1.0);
 
 
 #ifdef TEST
-- 
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