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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;
}
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