Re: getrandom vs. crypto/gc-random

[Bruno Haible]

> 1) The list of random devices, determined through gc-random.m4.
> 
> > To fix that, I
> > am thinking that getrandom should remove its dependency on 
> > crypto/gc-random, and
> > should simply use "/dev/urandom" for the nonce device without worrying about
> > whether crypto/gc-random would define NAME_OF_NONCE_DEVICE to 
> > "/dev/urandom".
> > This should work on all current porting targets and should simplify 
> > maintenance
> > by lessening dependencies on the crypto/gc-random module, which pulls in 
> > several
> > other modules that some packages won't want to bother with.
> 
> I agree. In my testing yesterday, I found that /dev/random and /dev/urandom 
> are
> present in all modern versions of operating systems, except native Windows.
> I tested:
>   Linux Fedora 1       OK
>   Linux Ubuntu 16.04   OK
>   Linux Ubuntu 18.04   OK
>   Linux Ubuntu 20.04   OK
>   Linux Alpine 3.9     OK
>   Hurd 2019            OK
>   GNU/kFreeBSD         OK
>   Mac OS X 10.5        OK
>   Mac OS X 10.13       OK
>   FreeBSD 11           OK
>   FreeBSD 12           OK
>   NetBSD 7.0           OK
>   NetBSD 9.0           OK
>   OpenBSD 6.5          OK
>   AIX 7.1              OK
>   Solaris 10           OK
>   Solaris 11.0         OK
>   Solaris 11.3         OK
>   Solaris 11.4         OK
>   Solaris OpenIndiana  OK
>   Haiku                OK
>   Cygwin               OK
>   Minix 3.3            OK
> 
> Seeing this, the configure options --enable-random-device,
> --enable-pseudo-random-device, --enable-nonce-device are not needed any more
> - neither for gc-gnulib nor for getrandom. I won't remove them from 
> gc-random.m4
> (since that is Simon's responsibility), but I agree with you that for 
> getrandom
> we can use the two de-facto standard device names.

Done as follows.


2020-05-31  Bruno Haible  <bruno@clisp.org>

        getrandom: Simplify the determination of the random number devices.
        Suggested by Paul Eggert in
        <https://lists.gnu.org/archive/html/bug-gnulib/2020-05/msg00383.html>.
        * lib/getrandom.c (NAME_OF_RANDOM_DEVICE, NAME_OF_NONCE_DEVICE): New
        macros.
        * modules/getrandom (Depends-on): Remove crypto/gc-random.

diff --git a/lib/getrandom.c b/lib/getrandom.c
index f20ffe0..0cc3dc3 100644
--- a/lib/getrandom.c
+++ b/lib/getrandom.c
@@ -27,6 +27,25 @@
 
 #include "minmax.h"
 
+/* These devices exist on all platforms except native Windows.  */
+#if !(defined _WIN32 && ! defined __CYGWIN__)
+
+/* Name of a device through which the kernel returns high quality random
+   numbers, from an entropy pool.  When the pool is empty, the call blocks
+   until entropy sources have added enough bits of entropy.  */
+# ifndef NAME_OF_RANDOM_DEVICE
+#  define NAME_OF_RANDOM_DEVICE "/dev/random"
+# endif
+
+/* Name of a device through which the kernel returns random or pseudo-random
+   numbers.  It uses an entropy pool, but, in order to avoid blocking, adds
+   bits generated by a pseudo-random number generator, as needed.  */
+# ifndef NAME_OF_NONCE_DEVICE
+#  define NAME_OF_NONCE_DEVICE "/dev/urandom"
+# endif
+
+#endif
+
 /* Set BUFFER (of size LENGTH) to random bytes under the control of FLAGS.
    Return the number of bytes written, or -1 on error.  */
 ssize_t
diff --git a/modules/getrandom b/modules/getrandom
index e94686d..8aa4be2 100644
--- a/modules/getrandom
+++ b/modules/getrandom
@@ -7,7 +7,6 @@ m4/getrandom.m4
 
 Depends-on:
 sys_random
-crypto/gc-random    [test $HAVE_GETRANDOM = 0]
 fcntl-h             [test $HAVE_GETRANDOM = 0 || test $REPLACE_GETRANDOM = 1]
 minmax              [test $HAVE_GETRANDOM = 0 || test $REPLACE_GETRANDOM = 1]
 open                [test $HAVE_GETRANDOM = 0 || test $REPLACE_GETRANDOM = 1]