Add a prominent warning about these functions' unsuitability for

cryptographic purposes, and recommend using arc4random(3) instead.

lib/libc/stdlib/rand.3

@@ -55,9 +55,15 @@
 .Fn rand_r "unsigned *ctx"
 .Sh DESCRIPTION
 .Bf -symbolic
+The functions described in this manual page are not cryptographically
+secure.
+Cryptographic applications should use
+.Xr arc4random 3
+instead.
+.Ef
+.Pp
 These interfaces are obsoleted by
 .Xr random 3 .
-.Ef
 .Pp
 The
 .Fn rand
@@ -88,9 +94,6 @@ The
 function initializes a seed using the
 .Xr random 4
 random number device which returns good random numbers.
-However, the
-.Fn rand
-function still remains unsuitable for cryptographic use.
 .Pp
 The
 .Fn rand_r
@@ -105,8 +108,6 @@ For better generator quality, use
 .Xr random 3
 or
 .Xr lrand48 3 .
-Applications requiring cryptographic quality randomness should use
-.Xr arc4random 3 .
 .Sh SEE ALSO
 .Xr arc4random 3 ,
 .Xr lrand48 3 ,

lib/libc/stdlib/random.3

@@ -53,6 +53,14 @@
 .Ft char *
 .Fn setstate "char *state"
 .Sh DESCRIPTION
+.Bf -symbolic
+The functions described in this manual page are not cryptographically
+secure.
+Cryptographic applications should use
+.Xr arc4random 3
+instead.
+.Ef
+.Pp
 The
 .Fn random
 function
@@ -98,10 +106,8 @@ as the seed.
 .Pp
 The
 .Fn srandomdev
-routine initializes a state array using the
-.Xr random 4
-random number device which returns good random numbers,
-suitable for cryptographic use.
+routine initializes a state array using data from
+.Xr random 4 .
 Note that this particular seeding
 procedure can generate states which are impossible to reproduce by
 calling
@@ -191,6 +197,3 @@ The historical implementation used to have a very weak seeding; the
 random sequence did not vary much with the seed.
 The current implementation employs a better pseudo-random number
 generator for the initial state calculation.
-.Pp
-Applications requiring cryptographic quality randomness should use
-.Xr arc4random 3 .