Implement arc4random_buf() function

Obtained from:  OpenBSD

2 files changed, 28 insertions, 4 deletions

diff --git a/lib/libc/gen/arc4random.3 b/lib/libc/gen/arc4random.3
index 27c6fd1..5af38ce 100644
--- a/lib/libc/gen/arc4random.3
+++ b/lib/libc/gen/arc4random.3
@@ -35,6 +35,7 @@
 .Os
 .Sh NAME
 .Nm arc4random ,
+.Nm arc4random_buf ,
 .Nm arc4random_stir ,
 .Nm arc4random_addrandom
 .Nd arc4 random number generator
@@ -45,6 +46,8 @@
 .Ft u_int32_t
 .Fn arc4random "void"
 .Ft void
+.Fn arc4random_buf "void *buf" "size_t nbytes"
+.Ft void
 .Fn arc4random_stir "void"
 .Ft void
 .Fn arc4random_addrandom "unsigned char *dat" "int datlen"
@@ -68,6 +71,13 @@ and therefore has twice the range of
 and
 .Xr random 3 .
 .Pp
+.Fn arc4random_buf
+function fills the region
+.Fa buf
+of length
+.Fa nbytes
+with ARC4-derived random data.
+.Pp
 The
 .Fn arc4random_stir
 function reads data from
@@ -78,10 +88,9 @@ and uses it to permute the S-Boxes via
 There is no need to call
 .Fn arc4random_stir
 before using
-.Fn arc4random ,
-since
 .Fn arc4random
-automatically initializes itself.
+functions family, since
+they automatically initialize themselves.
 .Sh EXAMPLES
 The following produces a drop-in replacement for the traditional
 .Fn rand
diff --git a/lib/libc/gen/arc4random.c b/lib/libc/gen/arc4random.c
index 6aa2323..7c11da2 100644
--- a/lib/libc/gen/arc4random.c
+++ b/lib/libc/gen/arc4random.c
@@ -164,7 +164,7 @@ arc4_check_init(void)
 	}
 }
 
-static void
+static inline void
 arc4_check_stir(void)
 {
 	if (!rs_stired || arc4_count <= 0) {
@@ -208,6 +208,21 @@ arc4random(void)
 	return (rnd);
 }
 
+void
+arc4random_buf(void *_buf, size_t n)
+{
+	u_char *buf = (u_char *)_buf;
+
+	THREAD_LOCK();
+	arc4_check_init();
+	while (n--) {
+		arc4_check_stir();
+		buf[n] = arc4_getbyte(&rs);
+		arc4_count--;
+	}
+	THREAD_UNLOCK();
+}
+
 #if 0
 /*-------- Test code for i386 --------*/
 #include <stdio.h>