From 58e10c74170bc2e99755b989f89dc14a1ec5f616 Mon Sep 17 00:00:00 2001
From: Kurt Zeilenga <kurt@openldap.org>
Date: Tue, 26 Oct 1999 23:41:09 +0000
Subject: [PATCH] Add a fallback based upon Phil Karn's "practical randomness"
 idea.

---
 libraries/liblutil/entropy.c | 53 ++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/libraries/liblutil/entropy.c b/libraries/liblutil/entropy.c
index dc33f7cfc4..5ff122b378 100644
--- a/libraries/liblutil/entropy.c
+++ b/libraries/liblutil/entropy.c
@@ -9,6 +9,7 @@
 #include <fcntl.h>
 
 #include <lutil.h>
+#include <lutil_md5.h>
 
 /*
  * lutil_entropy() provides nbytes of entropy in buf.
@@ -19,6 +20,7 @@ int lutil_entropy( char *buf, int nbytes )
 	if( nbytes < 0 ) return -1;
 	if( nbytes == 0 ) return 0;
 
+#undef URANDOM_DEVICE
 #ifdef URANDOM_DEVICE
 	/* Linux and *BSD offer a urandom device */
 	{
@@ -34,6 +36,57 @@ int lutil_entropy( char *buf, int nbytes )
 		/* should return nbytes */
 		if( rc < nbytes ) return -1;
 
+		return 0;
+	}
+#else
+	{
+		/* based upon Phil Karn's "practical randomness" idea
+		 * but implementation 100% OpenLDAP.  So don't blame Phil. */
+		/* worse case is this is a MD5 hash of a counter, if
+		 *	MD5 is a strong cryptographic hash, this should
+		 *	be fairly resisant to attack
+		 */
+		static int initialized = 0;
+		int n;
+
+		struct {
+			pid_t	pid;
+
+#ifdef HAVE_GETTIMEOFDAY
+			struct timeval *tv;
+#else
+			time_t	time;
+#endif
+			unsigned long	junk;
+		} rdata;
+
+		if( !initialized ) {
+			initialized++;
+
+			rdata.pid = getpid();
+		}
+		
+		for( n = 0; n < nbytes; n += 16 ) {
+			struct lutil_MD5Context ctx;
+			char digest[16];
+
+#ifdef HAVE_GETTIMEOFDAY
+			(void) gettimeofday( &rdata.tv, sizeof( rdata.tv ) );
+#else
+			(void) time( &rdata.time );
+#endif
+
+			rdata.pid++;
+			rdata.junk++;
+
+			lutil_MD5Init( &ctx );
+			lutil_MD5Update( &ctx, (char *) &rdata, sizeof( rdata ) );
+			lutil_MD5Final( digest, &ctx );
+
+			memcpy( &buf[n], digest,
+				nbytes - n > 16 ? 16 : nbytes - n );
+		}
+
 		return 0;
 	}
 #endif
-- 
2.39.5