Add a fallback based upon Phil Karn's "practical randomness" idea.

diff --git a/libraries/liblutil/entropy.c b/libraries/liblutil/entropy.c
index dc33f7cfc4344ae30fd7e24623e40c3ff124e18c..5ff122b378f5dbe1960c0ae6c0e0e706877150af 100644 (file)
--- a/libraries/liblutil/entropy.c
+++ b/libraries/liblutil/entropy.c
@@ -9,6 +9,7 @@
 #include <fcntl.h>
 
 #include <lutil.h>
+#include <lutil_md5.h>
 
 /*
  * lutil_entropy() provides nbytes of entropy in buf.
@@ -19,6 +20,7 @@ int lutil_entropy( char *buf, int nbytes )
        if( nbytes < 0 ) return -1;
        if( nbytes == 0 ) return 0;
 
+#undef URANDOM_DEVICE
 #ifdef URANDOM_DEVICE
        /* Linux and *BSD offer a urandom device */
        {
@@ -34,6 +36,57 @@ int lutil_entropy( char *buf, int nbytes )
                /* should return nbytes */
                if( rc < nbytes ) return -1;
 
+               return 0;
+       }
+#else
+       {
+               /* based upon Phil Karn's "practical randomness" idea
+                * but implementation 100% OpenLDAP.  So don't blame Phil. */
+               /* worse case is this is a MD5 hash of a counter, if
+                *      MD5 is a strong cryptographic hash, this should
+                *      be fairly resisant to attack
+                */
+               static int initialized = 0;
+               int n;
+
+               struct {
+                       pid_t   pid;
+
+#ifdef HAVE_GETTIMEOFDAY
+                       struct timeval *tv;
+#else
+                       time_t  time;
+#endif
+                       unsigned long   junk;
+               } rdata;
+
+               if( !initialized ) {
+                       initialized++;
+
+                       rdata.pid = getpid();
+               }
+               
+               for( n = 0; n < nbytes; n += 16 ) {
+                       struct lutil_MD5Context ctx;
+                       char digest[16];
+
+#ifdef HAVE_GETTIMEOFDAY
+                       (void) gettimeofday( &rdata.tv, sizeof( rdata.tv ) );
+#else
+                       (void) time( &rdata.time );
+#endif
+
+                       rdata.pid++;
+                       rdata.junk++;
+
+                       lutil_MD5Init( &ctx );
+                       lutil_MD5Update( &ctx, (char *) &rdata, sizeof( rdata ) );
+                       lutil_MD5Final( digest, &ctx );
+
+                       memcpy( &buf[n], digest,
+                               nbytes - n > 16 ? 16 : nbytes - n );
+               }
+
                return 0;
        }
 #endif