summaryrefslogtreecommitdiffstats
path: root/libraries/liblutil/entropy.c
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--libraries/liblutil/entropy.c170
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..289aca4
--- /dev/null
+++ b/libraries/liblutil/entropy.c
@@ -0,0 +1,170 @@
+/* entropy.c -- routines for providing pseudo-random data */
+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 1999-2022 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 publicly
+ * 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 offered 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;
+}