/* entropy.c -- routines for providing pseudo-random data */ /* $OpenLDAP: pkg/ldap/libraries/liblutil/entropy.c,v 1.27.2.3 2007/01/02 21:43:52 kurt Exp $ */ /* This work is part of OpenLDAP Software . * * Copyright 1999-2007 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 * . */ /* 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 #include #include #ifdef HAVE_PROCESS_H #include #endif #include #include #include /* * 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 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; }