v1-0002-Support-getrandom-as-random-source-where-availabl.patch

From 8de85697dd0c8d334168749d2e104a97a455d395 Mon Sep 17 00:00:00 2001
From: Masahiko Sawada <sawada.mshk@gmail.com>
Date: Tue, 21 Oct 2025 17:35:15 -0700
Subject: [PATCH v1 2/2] Support getrandom() as random source where available.

getrandom system call is used when random_source is 'system' on Linux
and Unix-like operating systems. It's more faster than reading
/dev/urandom.

Reviewed-by:
Discussion: https://postgr.es/m/
Backpatch-through:
---
 configure                   | 24 +++++++++++++++++++++-
 configure.ac                |  8 +++++++-
 meson.build                 |  5 +++++
 src/include/pg_config.h.in  |  3 +++
 src/port/pg_strong_random.c | 40 +++++++++++++++++++++++++++++++++++--
 5 files changed, 76 insertions(+), 4 deletions(-)

diff --git a/configure b/configure
index 809691fd61c..bee4d57131b 100755
--- a/configure
+++ b/configure
@@ -16058,6 +16058,25 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
+ac_fn_c_check_header_mongrel "$LINENO" "sys/random.h" "ac_cv_header_sys_random_h" "$ac_includes_default"
+if test "x$ac_cv_header_sys_random_h" = xyes; then :
+  for ac_func in getrandom
+do :
+  ac_fn_c_check_func "$LINENO" "getrandom" "ac_cv_func_getrandom"
+if test "x$ac_cv_func_getrandom" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_GETRANDOM 1
+_ACEOF
+
+$as_echo "#define HAVE_GETRANDOM 1" >>confdefs.h
+
+fi
+done
+
+fi
+
+
+
 ac_fn_c_check_func "$LINENO" "explicit_bzero" "ac_cv_func_explicit_bzero"
 if test "x$ac_cv_func_explicit_bzero" = xyes; then :
   $as_echo "#define HAVE_EXPLICIT_BZERO 1" >>confdefs.h
@@ -18336,6 +18355,9 @@ else
   if test x"$PORTNAME" = x"win32" ; then
     { $as_echo "$as_me:${as_lineno-$LINENO}: result: Windows native" >&5
 $as_echo "Windows native" >&6; }
+  elif test x"$ac_cv_func_getrandom" = x"yes" ; then
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: getrandom" >&5
+$as_echo "getrandom" >&6; }
   elif test x"$cross_compiling" = x"yes"; then
     { $as_echo "$as_me:${as_lineno-$LINENO}: result: assuming /dev/urandom" >&5
 $as_echo "assuming /dev/urandom" >&6; }
@@ -18365,7 +18387,7 @@ fi
     if test x"$ac_cv_file__dev_urandom" = x"no" ; then
       as_fn_error $? "
 no source of strong random numbers was found
-PostgreSQL can use OpenSSL, native Windows API or /dev/urandom as a source of random numbers." "$LINENO" 5
+PostgreSQL can use OpenSSL, native Windows API, getrandom, or /dev/urandom as a source of random numbers." "$LINENO" 5
     fi
   fi
 
diff --git a/configure.ac b/configure.ac
index 2690b71527b..2a4ef82e145 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1842,6 +1842,10 @@ AC_CHECK_DECLS([memset_s], [], [], [#define __STDC_WANT_LIB_EXT1__ 1
 # This is probably only present on macOS, but may as well check always
 AC_CHECK_DECLS(F_FULLFSYNC, [], [], [#include <fcntl.h>])
 
+AC_CHECK_HEADER([sys/random.h],
+ [AC_CHECK_FUNCS([getrandom],
+  [AC_DEFINE(HAVE_GETRANDOM, 1, [Define to 1 if you have getrandom])])])
+
 AC_REPLACE_FUNCS(m4_normalize([
 	explicit_bzero
 	getopt
@@ -2328,6 +2332,8 @@ else
   # be used.
   if test x"$PORTNAME" = x"win32" ; then
     AC_MSG_RESULT([Windows native])
+  elif test x"$ac_cv_func_getrandom" = x"yes" ; then
+    AC_MSG_RESULT(getrandom)
   elif test x"$cross_compiling" = x"yes"; then
     AC_MSG_RESULT([assuming /dev/urandom])
   else
@@ -2337,7 +2343,7 @@ else
     if test x"$ac_cv_file__dev_urandom" = x"no" ; then
       AC_MSG_ERROR([
 no source of strong random numbers was found
-PostgreSQL can use OpenSSL, native Windows API or /dev/urandom as a source of random numbers.])
+PostgreSQL can use OpenSSL, native Windows API, getrandom, or /dev/urandom as a source of random numbers.])
     fi
   fi
   AC_DEFINE([USE_RANDOM_SOURCE_SYSTEM] , 1, [Define to 1 to use system native source for random number generation])
diff --git a/meson.build b/meson.build
index fce1e1436e7..01c3c308b65 100644
--- a/meson.build
+++ b/meson.build
@@ -2710,6 +2710,11 @@ return 0;
    don't.'''.format(func))
 endforeach
 
+if cc.has_header('sys/random.h') and cc.has_function('getrandom',
+   args: test_c_args, prefix: '''
+#include <sys/random.h>''')
+  cdata.set('HAVE_GETRANDOM', 1)
+endif
 
 if cc.has_type('struct option',
     args: test_c_args, include_directories: postgres_inc,
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 35543a3e3c6..bf76baf0617 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -190,6 +190,9 @@
 /* Define to 1 if you have the `getpeerucred' function. */
 #undef HAVE_GETPEERUCRED
 
+/* Define to 1 if you have the `getrandom' function. */
+#undef HAVE_GETRANDOM
+
 /* Define to 1 if you have the <gssapi_ext.h> header file. */
 #undef HAVE_GSSAPI_EXT_H
 
diff --git a/src/port/pg_strong_random.c b/src/port/pg_strong_random.c
index ea6780dcc9f..0d2b5bc8ad5 100644
--- a/src/port/pg_strong_random.c
+++ b/src/port/pg_strong_random.c
@@ -40,7 +40,8 @@
  *
  * 1. OpenSSL's RAND_bytes()
  * 2. Windows' CryptGenRandom() function
- * 3. /dev/urandom
+ * 3. getrandom() function
+ * 4. /dev/urandom
  *
  * Returns true on success, and false if none of the sources
  * were available. NB: It is important to check the return value!
@@ -134,7 +135,42 @@ pg_strong_random(void *buf, size_t len)
 	return false;
 }
 
-#else							/* not USE_OPENSSL or WIN32 */
+#elif HAVE_GETRANDOM
+
+#include <sys/random.h>
+
+void
+pg_strong_random_init(void)
+{
+	/* No initialization needed */
+}
+
+bool
+pg_strong_random(void *buf, size_t len)
+{
+	char	   *p = buf;
+	ssize_t		res;
+
+	while (len)
+	{
+		/* Get random data from the urandom source in blocking mode */
+		res = getrandom(p, len, 0);
+		if (res <= 0)
+		{
+			if (errno == EINTR)
+				continue;		/* interrupted by signal, just retry */
+
+			return false;
+		}
+
+		p += res;
+		len -= res;
+	}
+
+	return true;
+}
+
+#else							/* not USE_OPENSSL, WIN32, or HAVE_GETRANDOM */
 
 /*
  * Without OpenSSL or Win32 support, just read /dev/urandom ourselves.
-- 
2.47.3