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156 lines
3.3 KiB
C
156 lines
3.3 KiB
C
/* $OpenLDAP$ */
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/*
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* Copyright 1998-2003 The OpenLDAP Foundation, All Rights Reserved.
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* COPYING RESTRICTIONS APPLY, see COPYRIGHT file
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*/
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#include "portable.h"
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#include <ac/string.h>
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#include <ac/time.h>
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#include <ac/unistd.h>
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#ifdef HAVE_PROCESS_H
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#include <process.h>
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#endif
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#include <fcntl.h>
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#include <lutil.h>
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#include <lutil_md5.h>
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/*
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* lutil_entropy() provides nbytes of entropy in buf.
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* Quality offerred is suitable for one-time uses, such as "once" keys.
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* Values may not be suitable for multi-time uses.
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*
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* Note: Callers are encouraged to provide additional bytes of
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* of entropy in the buf argument. This information is used in
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* fallback mode to improve the quality of bytes returned.
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*
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* This routinue should be extended to support additional sources
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* of entropy.
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*/
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int lutil_entropy( unsigned char *buf, ber_len_t nbytes )
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{
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if( nbytes == 0 ) return 0;
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#ifdef URANDOM_DEVICE
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#define URANDOM_NREADS 4
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/* Linux and *BSD offer a urandom device */
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{
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int rc, fd, n=0;
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fd = open( URANDOM_DEVICE, O_RDONLY );
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if( fd < 0 ) return -1;
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do {
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rc = read( fd, buf, nbytes );
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if( rc <= 0 ) break;
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buf+=rc;
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nbytes-=rc;
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if( ++n >= URANDOM_NREADS ) break;
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} while( nbytes > 0 );
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close(fd);
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return nbytes > 0 ? -1 : 0;
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}
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#elif PROV_RSA_FULL
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{
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/* Not used since _WIN32_WINNT not set... */
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HCRYPTPROV hProv = 0;
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/* Get handle to user default provider */
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if(!CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_FULL, 0)) {
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return -1;
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}
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/* Generate random initialization vector */
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if(!CryptGenRandom(hProv, (DWORD) nbytes, (BYTE *) buf)) {
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return -1;
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}
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/* Release provider handle */
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if(hProv != 0) CryptReleaseContext(hProv, 0);
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return 0;
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}
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#else
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{
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/* based upon Phil Karn's "practical randomness" idea
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* but implementation 100% OpenLDAP. So don't blame Phil.
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*
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* Worse case is that this is a MD5 hash of a counter, if
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* MD5 is a strong cryptographic hash, this should be fairly
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* resistant to attack
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*/
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/*
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* the caller may need to provide external synchronization OR
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* provide entropy (in buf) to ensure quality results as
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* access to this counter may not be atomic.
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*/
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static int counter = 0;
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ber_len_t n;
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struct rdata_s {
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int counter;
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unsigned char *buf;
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struct rdata_s *stack;
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pid_t pid;
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#ifdef HAVE_GETTIMEOFDAY
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struct timeval tv;
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#else
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time_t time;
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#endif
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unsigned long junk; /* purposely not initialized */
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} rdata;
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/* make sure rdata differs for each process */
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rdata.pid = getpid();
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/* make sure rdata differs for each program */
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rdata.buf = buf;
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rdata.stack = &rdata;
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for( n = 0; n < nbytes; n += 16 ) {
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struct lutil_MD5Context ctx;
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unsigned char digest[16];
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/* poor resolution */
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#ifdef HAVE_GETTIMEOFDAY
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(void) gettimeofday( &rdata.tv, NULL );
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#else
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(void) time( &rdata.time );
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#endif
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/* make sure rdata differs */
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rdata.counter = ++counter;
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rdata.pid++;
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rdata.junk++;
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lutil_MD5Init( &ctx );
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lutil_MD5Update( &ctx, (unsigned char *) &rdata, sizeof( rdata ) );
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/* allow caller to provided additional entropy */
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lutil_MD5Update( &ctx, buf, nbytes );
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lutil_MD5Final( digest, &ctx );
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AC_MEMCPY( &buf[n], digest,
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nbytes - n >= 16 ? 16 : nbytes - n );
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}
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return 0;
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}
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#endif
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return -1;
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}
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