1 files changed, 170 insertions, 0 deletions
diff --git a/libraries/liblutil/entropy.c b/libraries/liblutil/entropy.c
new file mode 100644
index 0000000..eb1d740
--- /dev/null
+++ b/libraries/liblutil/entropy.c
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+/* entropy.c -- routines for providing pseudo-random data */
+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 1999-2021 The OpenLDAP Foundation.
+ * Portions Copyright 1999-2003 Kurt D. Zeilenga.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+/* This work was initially developed by Kurt D. Zeilenga for
+ * inclusion in OpenLDAP Software based, in part, on publically
+ * available works (as noted below).
+ */
+
+#include "portable.h"
+
+#include <ac/string.h>
+#include <ac/time.h>
+#include <ac/unistd.h>
+
+#ifdef HAVE_PROCESS_H
+#include <process.h>
+#endif
+
+#include <fcntl.h>
+
+#include <lutil.h>
+#include <lutil_md5.h>
+
+/*
+ * lutil_entropy() provides nbytes of entropy in buf.
+ * Quality offerred is suitable for one-time uses, such as "once" keys.
+ * Values may not be suitable for multi-time uses.
+ *
+ * Note:  Callers are encouraged to provide additional bytes of
+ * of entropy in the buf argument.  This information is used in
+ * fallback mode to improve the quality of bytes returned.
+ *
+ * This routinue should be extended to support additional sources
+ * of entropy.
+ */
+int lutil_entropy( unsigned char *buf, ber_len_t nbytes )
+{
+	if( nbytes == 0 ) return 0;
+
+#ifdef URANDOM_DEVICE
+#define URANDOM_NREADS 4
+	/* Linux and *BSD offer a urandom device */
+	{
+		int rc, fd, n=0;
+
+		fd = open( URANDOM_DEVICE, O_RDONLY );
+
+		if( fd < 0 ) return -1;
+
+		do {
+			rc = read( fd, buf, nbytes );
+			if( rc <= 0 ) break;
+
+			buf+=rc;
+			nbytes-=rc;
+
+			if( ++n >= URANDOM_NREADS ) break;
+		} while( nbytes > 0 );
+
+		close(fd);
+		return nbytes > 0 ? -1 : 0;
+	}
+#elif defined(PROV_RSA_FULL)
+	{
+		/* Not used since _WIN32_WINNT not set... */
+		HCRYPTPROV hProv = 0;
+
+		/* Get handle to user default provider */
+		if(!CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_FULL, 0)) {
+		   return -1;
+		}
+
+		/* Generate random initialization vector */
+		if(!CryptGenRandom(hProv, (DWORD) nbytes, (BYTE *) buf)) {
+		   return -1;
+		}
+
+		/* Release provider handle */
+		if(hProv != 0) CryptReleaseContext(hProv, 0);
+
+		return 0;
+	}
+#else
+	{
+		/* based upon Phil Karn's "practical randomness" idea
+		 * but implementation 100% OpenLDAP.  So don't blame Phil.
+		 *
+		 * Worse case is that this is a MD5 hash of a counter, if
+		 * MD5 is a strong cryptographic hash, this should be fairly
+		 * resistant to attack
+		 */
+
+		/*
+		 * the caller may need to provide external synchronization OR
+		 * provide entropy (in buf) to ensure quality results as
+		 * access to this counter may not be atomic.
+		 */
+		static int counter = 0;
+		ber_len_t n;
+
+		struct rdata_s {
+			int counter;
+
+			unsigned char *buf;
+			struct rdata_s *stack;
+
+			pid_t	pid;
+
+#ifdef HAVE_GETTIMEOFDAY
+			struct timeval tv;
+#else
+			time_t	time;
+#endif
+
+			unsigned long	junk;	/* purposely not initialized */
+		} rdata;
+
+		/* make sure rdata differs for each process */
+		rdata.pid = getpid();
+
+		/* make sure rdata differs for each program */
+		rdata.buf = buf;
+		rdata.stack = &rdata;
+
+		for( n = 0; n < nbytes; n += 16 ) {
+			struct lutil_MD5Context ctx;
+			unsigned char digest[16];
+
+			/* poor resolution */
+#ifdef HAVE_GETTIMEOFDAY
+			(void) gettimeofday( &rdata.tv, NULL );
+#else
+			(void) time( &rdata.time );
+#endif
+
+			/* make sure rdata differs */
+			rdata.counter = ++counter;
+			rdata.pid++;
+			rdata.junk++;
+
+			lutil_MD5Init( &ctx );
+			lutil_MD5Update( &ctx, (unsigned char *) &rdata, sizeof( rdata ) );
+
+			/* allow caller to provided additional entropy */
+			lutil_MD5Update( &ctx, buf, nbytes );
+
+			lutil_MD5Final( digest, &ctx );
+
+			AC_MEMCPY( &buf[n], digest,
+				nbytes - n >= 16 ? 16 : nbytes - n );
+		}
+
+		return 0;
+	}
+#endif
+	return -1;
+}