3 * Copyright 1998-2002 The OpenLDAP Foundation, All Rights Reserved.
4 * COPYING RESTRICTIONS APPLY, see COPYRIGHT file
11 #include <ac/unistd.h>
20 #include <lutil_md5.h>
23 * lutil_entropy() provides nbytes of entropy in buf.
24 * Quality offerred is suitable for one-time uses, such as "once" keys.
25 * Values may not be suitable for multi-time uses.
27 * Note: Callers are encouraged to provide additional bytes of
28 * of entropy in the buf argument. This information is used in
29 * fallback mode to improve the quality of bytes returned.
31 * This routinue should be extended to support additional sources
34 int lutil_entropy( unsigned char *buf, ber_len_t nbytes )
36 if( nbytes == 0 ) return 0;
39 /* Linux and *BSD offer a urandom device */
43 fd = open( URANDOM_DEVICE, O_RDONLY );
45 if( fd < 0 ) return -1;
47 rc = read( fd, buf, nbytes );
50 /* should return nbytes */
51 if( rc != nbytes ) return -1;
57 /* Not used since _WIN32_WINNT not set... */
60 /* Get handle to user default provider */
61 if(!CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_FULL, 0)) {
65 /* Generate random initialization vector */
66 if(!CryptGenRandom(hProv, (DWORD) nbytes, (BYTE *) buf)) {
70 /* Release provider handle */
71 if(hProv != 0) CryptReleaseContext(hProv, 0);
77 /* based upon Phil Karn's "practical randomness" idea
78 * but implementation 100% OpenLDAP. So don't blame Phil.
80 * Worse case is that this is a MD5 hash of a counter, if
81 * MD5 is a strong cryptographic hash, this should be fairly
86 * the caller may need to provide external synchronization OR
87 * provide entropy (in buf) to ensure quality results as
88 * access to this counter may not be atomic.
90 static int counter = 0;
97 struct rdata_s *stack;
101 #ifdef HAVE_GETTIMEOFDAY
107 unsigned long junk; /* purposely not initialized */
110 /* make sure rdata differs for each process */
111 rdata.pid = getpid();
113 /* make sure rdata differs for each program */
115 rdata.stack = &rdata;
117 for( n = 0; n < nbytes; n += 16 ) {
118 struct lutil_MD5Context ctx;
121 /* poor resolution */
122 #ifdef HAVE_GETTIMEOFDAY
123 (void) gettimeofday( &rdata.tv, NULL );
125 (void) time( &rdata.time );
128 /* make sure rdata differs */
129 rdata.counter = ++counter;
133 lutil_MD5Init( &ctx );
134 lutil_MD5Update( &ctx, (unsigned char *) &rdata, sizeof( rdata ) );
136 /* allow caller to provided additional entropy */
137 lutil_MD5Update( &ctx, buf, nbytes );
139 lutil_MD5Final( digest, &ctx );
141 AC_MEMCPY( &buf[n], digest,
142 nbytes - n >= 16 ? 16 : nbytes - n );