Use getentropy() for seeding PRNG in Perl_seed()

On libc (*nix) systems we call `getentropy()` to get the seed needed to
start the PRNG. If that call fails, we fall back to reading the
filesystem via `/dev/urandom`. If that fails we fall back to hashing
some state variables instead.

This should be faster, less risky, and generally better than trying to
read from `/dev/urandom`

Foo

Configure

@@ -519,6 +519,7 @@ d_gai_strerror=''
 d_Gconvert=''
 d_getaddrinfo=''
 d_getcwd=''
+d_getentropy=''
 d_getenv_preserves_other_thread=''
 d_getespwnam=''
 d_getfsstat=''
@@ -702,6 +703,7 @@ d_newlocale=''
 d_querylocale=''
 d_uselocale=''
 i_xlocale=''
+i_sysrandom=''
 xlocale_needed=''
 d_nextafter=''
 d_nexttoward=''
@@ -12759,6 +12761,10 @@ eval $inlibc
 set xlocale.h i_xlocale
 eval $inhdr
 
+: see if this is a sys/random.h system
+set sys/random.h i_sysrandom
+eval $inhdr
+
 : see if newlocale exists
 set newlocale d_newlocale
 eval $inlibc
@@ -14369,6 +14375,10 @@ eval $inlibc
 set getcwd d_getcwd
 eval $inlibc
 
+: see if getentropy exists
+set getentropy d_getentropy
+eval $inlibc
+
 : check for getenv behavior
 case "$d_getenv_preserves_other_thread" in
 '')
@@ -25125,6 +25135,7 @@ d_gdbm_ndbm_h_uses_prototypes='$d_gdbm_ndbm_h_uses_prototypes'
 d_gdbmndbm_h_uses_prototypes='$d_gdbmndbm_h_uses_prototypes'
 d_getaddrinfo='$d_getaddrinfo'
 d_getcwd='$d_getcwd'
+d_getentropy='$d_getentropy'
 d_getenv_preserves_other_thread='$d_getenv_preserves_other_thread'
 d_getespwnam='$d_getespwnam'
 d_getfsstat='$d_getfsstat'
@@ -25718,6 +25729,7 @@ i_vfork='$i_vfork'
 i_wchar='$i_wchar'
 i_wctype='$i_wctype'
 i_xlocale='$i_xlocale'
+i_sysrandom='$i_sysrandom'
 ignore_versioned_solibs='$ignore_versioned_solibs'
 inc_version_list='$inc_version_list'
 inc_version_list_init='$inc_version_list_init'

Cross/config.sh-arm-linux

@@ -252,6 +252,7 @@ d_gdbm_ndbm_h_uses_prototypes='undef'
 d_gdbmndbm_h_uses_prototypes='undef'
 d_getaddrinfo='undef'
 d_getcwd='define'
+d_getentropy='undef'
 d_getenv_preserves_other_thread='define'
 d_getespwnam='undef'
 d_getfsstat='undef'
@@ -808,6 +809,7 @@ i_sysmount='define'
 i_sysndir='undef'
 i_sysparam='define'
 i_syspoll='undef'
+i_sysrandom='undef'
 i_sysresrc='define'
 i_syssecrt='undef'
 i_sysselct='define'

Cross/config.sh-arm-linux-n770

@@ -251,6 +251,7 @@ d_gdbm_ndbm_h_uses_prototypes='undef'
 d_gdbmndbm_h_uses_prototypes='undef'
 d_getaddrinfo='undef'
 d_getcwd='define'
+d_getentropy='undef'
 d_getenv_preserves_other_thread='define'
 d_getespwnam='undef'
 d_getfsstat='undef'
@@ -806,6 +807,7 @@ i_sysmount='define'
 i_sysndir='undef'
 i_sysparam='define'
 i_syspoll='undef'
+i_sysrandom='undef'
 i_sysresrc='define'
 i_syssecrt='undef'
 i_sysselct='define'

Porting/config.sh

@@ -263,6 +263,7 @@ d_gdbm_ndbm_h_uses_prototypes='undef'
 d_gdbmndbm_h_uses_prototypes='undef'
 d_getaddrinfo='define'
 d_getcwd='define'
+d_getentropy='undef'
 d_getenv_preserves_other_thread='define'
 d_getespwnam='undef'
 d_getfsstat='undef'
@@ -830,6 +831,7 @@ i_sysmount='define'
 i_sysndir='undef'
 i_sysparam='define'
 i_syspoll='define'
+i_sysrandom='undef'
 i_sysresrc='define'
 i_syssecrt='undef'
 i_sysselct='define'

config_h.SH

@@ -561,6 +561,12 @@ sed <<!GROK!THIS! >$CONFIG_H -e 's!^#undef\(.*/\)\*!/\*#define\1 \*!' -e 's!^#un
  */
 #$d_system HAS_SYSTEM	/**/
 
+/* HAS_SYSRANDOM:
+ *	This symbol, if defined, indicates that the system has the
+ *	sys/random.h header file.
+ */
+#$i_sysrandom HAS_SYSRANDOM	/**/
+
 /* HAS_TCGETPGRP:
  *	This symbol, if defined, indicates that the tcgetpgrp routine is
  *	available to get foreground process group ID.
@@ -1604,6 +1610,12 @@ sed <<!GROK!THIS! >$CONFIG_H -e 's!^#undef\(.*/\)\*!/\*#define\1 \*!' -e 's!^#un
  */
 #$d_flexfnam	FLEXFILENAMES		/**/
 
+/* HAS_GETENTROPY:
+ *	This symbol, if defined, indicates that the getentropy routine is
+ *	available.
+ */
+#$d_getentropy HAS_GETENTROPY		/**/
+
 /* HAS_GETGRENT:
  *	This symbol, if defined, indicates that the getgrent routine is
  *	available for sequential access of the group database.

configure.com

@@ -6210,6 +6210,7 @@ $ WC "d_nice='define'"
 $ WC "d_nl_langinfo='" + d_nl_langinfo + "'"
 $ WC "d_nl_langinfo_l='undef'"
 $ WC "d_non_int_bitfields='define'"
+$ WC "d_getentropy='undef'"
 $ WC "d_getenv_preserves_other_thread='" + d_getenv_preserves_other_thread + "'"
 $ WC "d_nv_preserves_uv='" + d_nv_preserves_uv + "'"
 $ WC "nv_overflows_integers_at='" + nv_overflows_integers_at + "'"
@@ -6573,6 +6574,7 @@ $ WC "i_sysmount='undef'"
 $ WC "i_sysndir='undef'"
 $ WC "i_sysparam='undef'"
 $ WC "i_syspoll='" + i_syspoll + "'"
+$ WC "i_sysrandom='undef'"
 $ WC "i_sysresrc='undef'"
 $ WC "i_syssecrt='" + i_syssecrt + "'"
 $ WC "i_sysselct='undef'"

metaconfig.h

@@ -44,6 +44,7 @@
  * HAS_FD_SET
  * HAS_FFS
  * HAS_FFSL
+ * HAS_GETENTROPY
  * HAS_GETMNT
  * HAS_GMTIME64
  * HAS_GNULIBC
@@ -85,6 +86,7 @@
  * INSTALL_USR_BIN_PERL
  * I_STDBOOL
  * I_SYS_MOUNT
+ * I_SYSRANDOM
  * I_SYS_STATFS
  * I_SYS_STATVFS
  * I_SYS_VFS

plan9/config_sh.sample

@@ -252,6 +252,7 @@ d_gdbm_ndbm_h_uses_prototypes='undef'
 d_gdbmndbm_h_uses_prototypes='undef'
 d_getaddrinfo='undef'
 d_getcwd='define'
+d_getentropy='undef'
 d_getenv_preserves_other_thread='define'
 d_getespwnam='undef'
 d_getfsstat='undef'
@@ -802,6 +803,7 @@ i_sysmount='undef'
 i_sysndir='undef'
 i_sysparam='define'
 i_syspoll='undef'
+i_sysrandom='undef'
 i_sysresrc='define'
 i_syssecrt='undef'
 i_sysselct='define'

util.c

@@ -38,6 +38,11 @@
 #include <math.h>
 #include <stdlib.h>
 
+/* For get_entropy() on non-Linux systems (MacOS, Android) we need sys/random.h */
+#ifdef HAS_SYSRANDOM
+#include <sys/random.h>
+#endif
+
 #ifdef __Lynx__
 /* Missing protos on LynxOS */
 int putenv(char *);
@@ -4612,6 +4617,14 @@ Perl_seed(pTHX)
 #endif
     U64 u;
 
+#ifdef HAS_GETENTROPY
+    U8 ok = (getentropy(&u, sizeof(u)) == 0);
+    PerlIO_printf(Perl_debug_log, "Entropy: OK:%i Seed:%lu\n", ok, u);
+    if (ok) {
+        return u;
+    }
+#endif
+
     int fd = PerlLIO_open_cloexec(PERL_RANDOM_DEVICE, 0);
     if (fd != -1) {
         if (PerlLIO_read(fd, (void*)&u, sizeof u) != sizeof u) {

win32/config.gc

@@ -239,6 +239,7 @@ d_gdbm_ndbm_h_uses_prototypes='undef'
 d_gdbmndbm_h_uses_prototypes='undef'
 d_getaddrinfo='define'
 d_getcwd='define'
+d_getentropy='undef'
 d_getenv_preserves_other_thread='define'
 d_getespwnam='undef'
 d_getfsstat='undef'
@@ -799,6 +800,7 @@ i_sysmount='undef'
 i_sysndir='undef'
 i_sysparam='undef'
 i_syspoll='undef'
+i_sysrandom='undef'
 i_sysresrc='undef'
 i_syssecrt='undef'
 i_sysselct='undef'

win32/config.vc

@@ -239,6 +239,7 @@ d_gdbm_ndbm_h_uses_prototypes='undef'
 d_gdbmndbm_h_uses_prototypes='undef'
 d_getaddrinfo='undef'
 d_getcwd='define'
+d_getentropy='undef'
 d_getenv_preserves_other_thread='define'
 d_getespwnam='undef'
 d_getfsstat='undef'
@@ -798,6 +799,7 @@ i_sysmount='undef'
 i_sysndir='undef'
 i_sysparam='undef'
 i_syspoll='undef'
+i_sysrandom='undef'
 i_sysresrc='undef'
 i_syssecrt='undef'
 i_sysselct='undef'