Clean up and modernize librandom.

 Correct random number generation has historically been
suprisingly painful to achieve. There was no standard,
every system behaved in a subtly different way, and there
were a few userland initiatives to get decent randomness,
all incompatible of course.
 The situation is a bit better now, we're heading towards
some standardization. The arc4random() series of functions
is a good API, and available on a lot of systems -
unfortunately not Linux, but on Linux the new getrandom()
makes using /dev/random obsolete.

 So I removed the old crap in librandom, dropped EGD support,
dropped dynamic backend selection, made a single API series
(random_* instead of goodrandom_* and badrandom_*), added
an arc4random backend and a getrandom backend, and defaulted
to /dev/urandom backed up by SURF in the worst case. This
should be much smaller and logical. However, it's a major
API break, so the skarnet.org stack will be changed to
adapt.

3 files changed, 33 insertions, 54 deletions

diff --git a/src/sysdeps/tryarc4random.c b/src/sysdeps/tryarc4random.c
new file mode 100644
index 0000000..b2f596a
--- /dev/null
+++ b/src/sysdeps/tryarc4random.c
@@ -0,0 +1,11 @@
+/* ISC license. */
+
+#undef _POSIX_C_SOURCE
+#undef _XOPEN_SOURCE
+
+#include <stdlib.h>
+
+int main (void)
+{
+  return arc4random_uniform(1) ;
+}
diff --git a/src/sysdeps/trydevrandom.c b/src/sysdeps/trydevrandom.c
deleted file mode 100644
index 395d008..0000000
--- a/src/sysdeps/trydevrandom.c
+++ /dev/null
@@ -1,54 +0,0 @@
-/* ISC license. */
-
-#include <unistd.h>
-#include <sys/types.h>
-#include <fcntl.h>
-#include <errno.h>
-
-static int fd_read (int fd, char *buf, unsigned int len)
-{
-  register int r ;
-  do r = read(fd, buf, len) ;
-  while ((r == -1) && (errno == EINTR)) ;
-  return r ;
-}
-
-static unsigned int allread (int fd, register char *buf, register unsigned int len)
-{
-  register unsigned int written = 0 ;
-  while (len)
-  {
-    register int w = fd_read(fd, buf, len) ;
-    if (!w) errno = EPIPE ;
-    if (w <= 0) break ;
-    written += w ;
-    buf += w ;
-    len -= w ;
-  }
-  return written ;
-}
-
-static int byte_diff (char *s, unsigned int n, char *t)
-{
-  for (;;)
-  {
-    if (!n) return 0 ;
-    if (*s != *t) break ;
-    ++s ; ++t ; --n ;
-  }
-  return ((int)(unsigned int)(unsigned char) *s)
-       - ((int)(unsigned int)(unsigned char) *t);
-}
-
-int main ()
-{
-  char a[64] ;
-  char b[64] ;
-  int fd = open("/dev/random", O_RDONLY) ;
-  if ((fd == -1) || (allread(fd, a, 64) < 64) ) return 111 ;
-  close(fd) ;
-  fd = open("/dev/random", O_RDONLY) ;
-  if ((fd == -1) || (allread(fd, b, 64) < 64) ) return 111 ;
-  close(fd) ;
-  return !byte_diff(a, 64, b) ;
-}
diff --git a/src/sysdeps/trygetrandom.c b/src/sysdeps/trygetrandom.c
new file mode 100644
index 0000000..67a623d
--- /dev/null
+++ b/src/sysdeps/trygetrandom.c
@@ -0,0 +1,22 @@
+/* ISC license. */
+
+#undef _POSIX_C_SOURCE
+#undef _XOPEN_SOURCE
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <sys/types.h>
+#include <sys/syscall.h>
+
+static int getrandom (void *buf, size_t buflen, unsigned int flags)
+{
+  return syscall(SYS_getrandom, buf, buflen, flags) ;
+}
+
+int main (void)
+{
+  char buf[4] ;
+  return getrandom(buf, 4, 0) ;
+}