]> git.saurik.com Git - apple/xnu.git/blobdiff - bsd/dev/random/randomdev.c
xnu-1699.26.8.tar.gz
[apple/xnu.git] / bsd / dev / random / randomdev.c
index 96f997e24d0324d9da3231448ce3c48ec9d78580..c29e9f877fec0e9672e4ef05787cbc08ffff21b6 100644 (file)
@@ -1,16 +1,19 @@
 /*
- * Copyright (c) 1999, 2000-2002 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 1999-2009 Apple, Inc. All rights reserved.
  *
- * @APPLE_LICENSE_HEADER_START@
- * 
- * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
  * This file contains Original Code and/or Modifications of Original Code
  * as defined in and that are subject to the Apple Public Source License
  * Version 2.0 (the 'License'). You may not use this file except in
- * compliance with the License. Please obtain a copy of the License at
- * http://www.opensource.apple.com/apsl/ and read it before using this
- * file.
+ * compliance with the License. The rights granted to you under the License
+ * may not be used to create, or enable the creation or redistribution of,
+ * unlawful or unlicensed copies of an Apple operating system, or to
+ * circumvent, violate, or enable the circumvention or violation of, any
+ * terms of an Apple operating system software license agreement.
+ * 
+ * Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this file.
  * 
  * The Original Code and all software distributed under the License are
  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  * Please see the License for the specific language governing rights and
  * limitations under the License.
  * 
- * @APPLE_LICENSE_HEADER_END@
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  */
 
+/*
+       WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!
+       
+       THIS FILE IS NEEDED TO PASS FIPS ACCEPTANCE FOR THE RANDOM NUMBER GENERATOR.
+       IF YOU ALTER IT IN ANY WAY, WE WILL NEED TO GO THOUGH FIPS ACCEPTANCE AGAIN,
+       AN OPERATION THAT IS VERY EXPENSIVE AND TIME CONSUMING.  IN OTHER WORDS,
+       DON'T MESS WITH THIS FILE.
+
+       WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!
+*/
+
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/proc.h>
 #include <sys/ioctl.h>
 #include <sys/conf.h>
 #include <sys/fcntl.h>
+#include <string.h>
 #include <miscfs/devfs/devfs.h>
 #include <kern/lock.h>
+#include <kern/clock.h>
 #include <sys/time.h>
 #include <sys/malloc.h>
+#include <sys/uio_internal.h>
 
 #include <dev/random/randomdev.h>
 #include <dev/random/YarrowCoreLib/include/yarrow.h>
 
+#include <libkern/OSByteOrder.h>
+#include <libkern/OSAtomic.h>
+
+#include <mach/mach_time.h>
+#include <machine/machine_routines.h>
+
+#include "fips_sha1.h"
+
 #define RANDOM_MAJOR  -1 /* let the kernel pick the device number */
 
+d_ioctl_t       random_ioctl;
+
 /*
  * A struct describing which functions will get invoked for certain
  * actions.
@@ -50,9 +77,9 @@ static struct cdevsw random_cdevsw =
        random_close,           /* close */
        random_read,            /* read */
        random_write,           /* write */
-       eno_ioctl,                      /* ioctl */
-       nulldev,                        /* stop */
-       nulldev,                        /* reset */
+       random_ioctl,           /* ioctl */
+       (stop_fcn_t *)nulldev, /* stop */
+       (reset_fcn_t *)nulldev, /* reset */
        NULL,                           /* tty's */
        eno_select,                     /* select */
        eno_mmap,                       /* mmap */
@@ -62,22 +89,246 @@ static struct cdevsw random_cdevsw =
        0                                       /* type */
 };
 
+
+/*
+       WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!
+
+       ANY CODE PROTECTED UNDER "#ifdef __arm__" IS SERIOUSLY SUPPOSED TO BE THERE!
+       IF YOU REMOVE ARM CODE, RANDOM WILL NOT MEAN ANYTHING FOR iPHONES ALL OVER.
+       PLEASE DON'T TOUCH __arm__ CODE IN THIS FILE!
+
+       WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!
+*/
+
+
 /* Used to detect whether we've already been initialized */
-static int gRandomInstalled = 0;
+static UInt8 gRandomInstalled = 0;
 static PrngRef gPrngRef;
 static int gRandomError = 1;
-static mutex_t *gYarrowMutex = 0;
+static lck_grp_t *gYarrowGrp;
+static lck_attr_t *gYarrowAttr;
+static lck_grp_attr_t *gYarrowGrpAttr;
+static lck_mtx_t *gYarrowMutex = 0;
+static UInt8 gYarrowInitializationLock = 0;
 
 #define RESEED_TICKS 50 /* how long a reseed operation can take */
 
+
+typedef u_int8_t BlockWord;
+enum {kBSize = 20};
+typedef BlockWord Block[kBSize];
+enum {kBlockSize = sizeof(Block)};
+
+/* define prototypes to keep the compiler happy... */
+
+void add_blocks(Block a, Block b, BlockWord carry);
+void fips_initialize(void);
+void random_block(Block b, int addOptional);
+u_int32_t CalculateCRC(u_int8_t* buffer, size_t length);
+
+/*
+ * Get 120 bits from yarrow
+ */
+
+/*
+ * add block b to block a
+ */
+void
+add_blocks(Block a, Block b, BlockWord carry)
+{
+       int i = kBlockSize - 1;
+       while (i >= 0)
+       {
+               u_int32_t c = (u_int32_t)carry +
+                                         (u_int32_t)a[i] +
+                                         (u_int32_t)b[i];
+               a[i] = c & 0xff;
+               carry = c >> 8;
+               i -= 1;
+       }
+}
+
+
+
+static char zeros[(512 - kBSize * 8) / 8];
+static Block g_xkey;
+static Block g_random_data;
+static int g_bytes_used;
+static unsigned char g_SelfTestInitialized = 0;
+static u_int32_t gLastBlockChecksum;
+
+static const u_int32_t g_crc_table[] =
+{
+       0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
+       0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
+       0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE, 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
+       0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
+       0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
+       0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
+       0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
+       0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924, 0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
+       0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
+       0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
+       0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
+       0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
+       0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2, 0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
+       0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
+       0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
+       0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
+       0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
+       0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8, 0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
+       0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
+       0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
+       0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
+       0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
+       0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236, 0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
+       0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
+       0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
+       0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
+       0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
+       0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C, 0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
+       0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
+       0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
+       0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
+       0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D,
+};
+
+/*
+ * Setup for fips compliance
+ */
+
+/*
+ * calculate a crc-32 checksum
+ */
+u_int32_t CalculateCRC(u_int8_t* buffer, size_t length)
+{
+       u_int32_t crc = 0;
+       
+       size_t i;
+       for (i = 0; i < length; ++i)
+       {
+               u_int32_t temp = (crc ^ ((u_int32_t) buffer[i])) & 0xFF;
+               crc = (crc >> 8) ^ g_crc_table[temp];
+       }
+       
+       return crc;
+}
+
+/*
+ * get a random block of data per fips 186-2
+ */
+void
+random_block(Block b, int addOptional)
+{
+       SHA1_CTX sha1_ctx;
+       
+       int repeatCount = 0;
+       do
+       {
+               // do one iteration
+               
+               if (addOptional)
+               {
+                       // create an xSeed to add.
+                       Block xSeed;
+                       prngOutput (gPrngRef, (BYTE*) &xSeed, sizeof (xSeed));
+                       
+                       // add the seed to the previous value of g_xkey
+                       add_blocks (g_xkey, xSeed, 0);
+               }
+               
+               // initialize the value of H
+               FIPS_SHA1Init(&sha1_ctx);
+               
+               // to stay compatible with the FIPS specification, we need to flip the bytes in
+               // g_xkey to little endian byte order.  In our case, this makes exactly no difference
+               // (random is random), but we need to do it anyway to keep FIPS happy
+               
+               // compute "G"
+               FIPS_SHA1Update(&sha1_ctx, g_xkey, kBlockSize);
+               
+               // add zeros to fill the internal SHA-1 buffer
+               FIPS_SHA1Update (&sha1_ctx, (const u_int8_t *)zeros, sizeof (zeros));
+               
+               // we have to do a byte order correction here because the sha1 math is being done internally
+               // as u_int32_t, not a stream of bytes.  Since we maintain our data as a byte stream, we need
+               // to convert
+               
+               u_int32_t* finger = (u_int32_t*) b;
+               
+               unsigned j;
+               for (j = 0; j < kBlockSize / sizeof (u_int32_t); ++j)
+               {
+                       *finger++ = OSSwapHostToBigInt32(sha1_ctx.h.b32[j]);
+               }               
+               
+               // calculate the CRC-32 of the block
+               u_int32_t new_crc = CalculateCRC(sha1_ctx.h.b8, sizeof (Block));
+               
+               // make sure we don't repeat
+               int cmp = new_crc == gLastBlockChecksum;
+               gLastBlockChecksum = new_crc;
+               if (!g_SelfTestInitialized)
+               {
+                       g_SelfTestInitialized = 1;
+                       return;
+               }
+               else if (!cmp)
+               {
+                       return;
+               }
+               
+               repeatCount += 1;
+               
+               // fix up the next value of g_xkey
+               add_blocks (g_xkey, b, 1);
+       } while (repeatCount < 2);
+       
+       /*
+        * If we got here, three sucessive checksums of the random number
+        * generator have been the same.  Since the odds of this happening are
+        * 1 in 18,446,744,073,709,551,616, (1 in 18 quintillion) one of the following has
+        * most likely happened:
+        *
+        * 1: There is a significant bug in this code.
+        * 2: There has been a massive system failure.
+        * 3: The universe has ceased to exist.
+        *
+        * There is no good way to recover from any of these cases. We
+        * therefore panic.
+        */
+        
+        panic("FIPS random self-test failed.");
+}
+
 /*
  *Initialize ONLY the Yarrow generator.
  */
-void PreliminarySetup ()
+void
+PreliminarySetup(void)
 {
     prng_error_status perr;
-    struct timeval tt;
-    char buffer [16];
+
+       /* Multiple threads can enter this as a result of an earlier
+        * check of gYarrowMutex.  We make sure that only one of them
+        * can enter at a time.  If one of them enters and discovers
+        * that gYarrowMutex is no longer NULL, we know that another
+        * thread has initialized the Yarrow state and we can exit.
+        */
+       
+       /* The first thread that enters this function will find
+        * gYarrowInitializationLock set to 0.  It will atomically
+        * set the value to 1 and, seeing that it was zero, drop
+        * out of the loop.  Other threads will see that the value is
+        * 1 and continue to loop until we are initialized.
+     */
+
+       while (OSTestAndSet(0, &gYarrowInitializationLock)); /* serialize access to this function */
+       
+       if (gYarrowMutex) {
+               /*  we've already been initialized, clear and get out */
+               goto function_exit;
+       }
 
     /* create a Yarrow object */
     perr = prngInitialize(&gPrngRef);
@@ -89,7 +340,12 @@ void PreliminarySetup ()
        /* clear the error flag, reads and write should then work */
     gRandomError = 0;
 
+    struct timeval tt;
+    char buffer [16];
+
     /* get a little non-deterministic data as an initial seed. */
+       /* On OSX, securityd will add much more entropy as soon as it */
+       /* comes up.  On iOS, entropy is added with each system interrupt. */
     microtime(&tt);
 
     /*
@@ -103,7 +359,7 @@ void PreliminarySetup ()
     if (perr != 0) {
         /* an error, complain */
         printf ("Couldn't seed Yarrow.\n");
-        return;
+        goto function_exit;
     }
     
     /* turn the data around */
@@ -113,7 +369,39 @@ void PreliminarySetup ()
     perr = prngForceReseed(gPrngRef, RESEED_TICKS);
     
     /* make a mutex to control access */
-    gYarrowMutex = mutex_alloc(0);
+    gYarrowGrpAttr = lck_grp_attr_alloc_init();
+    gYarrowGrp     = lck_grp_alloc_init("random", gYarrowGrpAttr);
+    gYarrowAttr    = lck_attr_alloc_init();
+    gYarrowMutex   = lck_mtx_alloc_init(gYarrowGrp, gYarrowAttr);
+       
+       fips_initialize ();
+
+function_exit:
+       /* allow other threads to figure out whether or not we have been initialized. */
+       gYarrowInitializationLock = 0;
+}
+
+const Block kKnownAnswer = {0x92, 0xb4, 0x04, 0xe5, 0x56, 0x58, 0x8c, 0xed, 0x6c, 0x1a, 0xcd, 0x4e, 0xbf, 0x05, 0x3f, 0x68, 0x09, 0xf7, 0x3a, 0x93};
+
+void
+fips_initialize(void)
+{
+       /* So that we can do the self test, set the seed to zero */
+       memset(&g_xkey, 0, sizeof(g_xkey));
+       
+       /* other initializations */
+       memset (zeros, 0, sizeof (zeros));
+       g_bytes_used = 0;
+       random_block(g_random_data, FALSE);
+       
+       // check here to see if we got the initial data we were expecting
+       if (memcmp(kKnownAnswer, g_random_data, kBlockSize) != 0)
+       {
+               panic("FIPS random self test failed");
+       }
+       
+       // now do the random block again to make sure that userland doesn't get predicatable data
+       random_block(g_random_data, TRUE);
 }
 
 /*
@@ -121,18 +409,15 @@ void PreliminarySetup ()
  * and to register ourselves with devfs
  */
 void
-random_init()
+random_init(void)
 {
        int ret;
 
-       if (gRandomInstalled)
+       if (OSTestAndSet(0, &gRandomInstalled)) {
+               /* do this atomically so that it works correctly with
+                multiple threads */
                return;
-
-       /* install us in the file system */
-       gRandomInstalled = 1;
-
-       /* setup yarrow and the mutex */
-       PreliminarySetup();
+       }
 
        ret = cdevsw_add(RANDOM_MAJOR, &random_cdevsw);
        if (ret < 0) {
@@ -142,14 +427,32 @@ random_init()
        }
 
        devfs_make_node(makedev (ret, 0), DEVFS_CHAR,
-               UID_ROOT, GID_WHEEL, 0644, "random", 0);
+               UID_ROOT, GID_WHEEL, 0666, "random", 0);
 
        /*
         * also make urandom 
         * (which is exactly the same thing in our context)
         */
        devfs_make_node(makedev (ret, 1), DEVFS_CHAR,
-               UID_ROOT, GID_WHEEL, 0644, "urandom", 0);
+               UID_ROOT, GID_WHEEL, 0666, "urandom", 0);
+
+       /* setup yarrow and the mutex if needed*/
+       PreliminarySetup();
+}
+
+int
+random_ioctl(  __unused dev_t dev, u_long cmd, __unused caddr_t data, 
+                               __unused int flag, __unused struct proc *p  )
+{
+       switch (cmd) {
+       case FIONBIO:
+       case FIOASYNC:
+               break;
+       default:
+               return ENODEV;
+       }
+
+       return (0);
 }
 
 /*
@@ -158,7 +461,7 @@ random_init()
  */
  
 int
-random_open(dev_t dev, int flags, int devtype, struct proc *p)
+random_open(__unused dev_t dev, int flags, __unused int devtype, __unused struct proc *p)
 {
        if (gRandomError != 0) {
                /* forget it, yarrow didn't come up */
@@ -172,8 +475,10 @@ random_open(dev_t dev, int flags, int devtype, struct proc *p)
        if (flags & FWRITE) {
                if (securelevel >= 2)
                        return (EPERM);
-               if ((securelevel >= 1) && suser(p->p_ucred, &p->p_acflag))
+#ifndef __APPLE__
+               if ((securelevel >= 1) && proc_suser(p))
                        return (EPERM);
+#endif /* !__APPLE__ */
        }
 
        return (0);
@@ -185,7 +490,7 @@ random_open(dev_t dev, int flags, int devtype, struct proc *p)
  */
  
 int
-random_close(dev_t dev, int flags, int mode, struct proc *p)
+random_close(__unused dev_t dev, __unused int flags, __unused int mode, __unused struct proc *p)
 {
        return (0);
 }
@@ -196,7 +501,7 @@ random_close(dev_t dev, int flags, int mode, struct proc *p)
  * prng.
  */
 int
-random_write (dev_t dev, struct uio *uio, int ioflag)
+random_write (__unused dev_t dev, struct uio *uio, __unused int ioflag)
 {
     int retCode = 0;
     char rdBuffer[256];
@@ -206,21 +511,21 @@ random_write (dev_t dev, struct uio *uio, int ioflag)
     }
     
     /* get control of the Yarrow instance, Yarrow is NOT thread safe */
-    mutex_lock(gYarrowMutex);
+    lck_mtx_lock(gYarrowMutex);
     
     /* Security server is sending us entropy */
 
-    while (uio->uio_resid > 0 && retCode == 0) {
+    while (uio_resid(uio) > 0 && retCode == 0) {
         /* get the user's data */
-        int bytesToInput = min(uio->uio_resid, sizeof (rdBuffer));
+        int bytesToInput = min(uio_resid(uio), sizeof (rdBuffer));
         retCode = uiomove(rdBuffer, bytesToInput, uio);
         if (retCode != 0)
             goto /*ugh*/ error_exit;
         
         /* put it in Yarrow */
         if (prngInput(gPrngRef, (BYTE*) rdBuffer,
-                       sizeof (rdBuffer), SYSTEM_SOURCE,
-               sizeof (rdBuffer) * 8) != 0) {
+                       bytesToInput, SYSTEM_SOURCE,
+               bytesToInput * 8) != 0) {
             retCode = EIO;
             goto error_exit;
         }
@@ -235,7 +540,7 @@ random_write (dev_t dev, struct uio *uio, int ioflag)
     /* retCode should be 0 at this point */
     
 error_exit: /* do this to make sure the mutex unlocks. */
-    mutex_unlock(gYarrowMutex);
+    lck_mtx_unlock(gYarrowMutex);
     return (retCode);
 }
 
@@ -243,40 +548,45 @@ error_exit: /* do this to make sure the mutex unlocks. */
  * return data to the caller.  Results unpredictable.
  */ 
 int
-random_read(dev_t dev, struct uio *uio, int ioflag)
+random_read(__unused dev_t dev, struct uio *uio, __unused int ioflag)
 {
     int retCode = 0;
-    char wrBuffer[512];
-
+       
     if (gRandomError != 0)
         return (ENOTSUP);
 
    /* lock down the mutex */
-    mutex_lock(gYarrowMutex);
+    lck_mtx_lock(gYarrowMutex);
+
 
-    while (uio->uio_resid > 0 && retCode == 0) {
+       int bytes_remaining = uio_resid(uio);
+    while (bytes_remaining > 0 && retCode == 0) {
         /* get the user's data */
-        int bytesToRead = min(uio->uio_resid, sizeof (wrBuffer));
-        
-        /* get the data from Yarrow */
-        if (prngOutput(gPrngRef, (BYTE *) wrBuffer, sizeof (wrBuffer)) != 0) {
-            printf ("Couldn't read data from Yarrow.\n");
-            
-            /* something's really weird */
-            retCode = EIO;
-            goto error_exit;
-        }
-        
-        retCode = uiomove(wrBuffer, bytesToRead, uio);
-        
+               int bytes_to_read = 0;
+               
+               int bytes_available = kBlockSize - g_bytes_used;
+        if (bytes_available == 0)
+               {
+                       random_block(g_random_data, TRUE);
+                       g_bytes_used = 0;
+                       bytes_available = kBlockSize;
+               }
+               
+               bytes_to_read = min (bytes_remaining, bytes_available);
+               
+        retCode = uiomove(((caddr_t)g_random_data)+ g_bytes_used, bytes_to_read, uio);
+        g_bytes_used += bytes_to_read;
+
         if (retCode != 0)
             goto error_exit;
+               
+               bytes_remaining = uio_resid(uio);
     }
     
     retCode = 0;
     
 error_exit:
-    mutex_unlock(gYarrowMutex);
+    lck_mtx_unlock(gYarrowMutex);
     return retCode;
 }
 
@@ -288,18 +598,35 @@ read_random(void* buffer, u_int numbytes)
         PreliminarySetup ();
     }
     
-    mutex_lock(gYarrowMutex);
-    prngOutput(gPrngRef, (BYTE *) buffer, numbytes);
-    mutex_unlock(gYarrowMutex);
+    lck_mtx_lock(gYarrowMutex);
+       int bytes_read = 0;
+
+       int bytes_remaining = numbytes;
+    while (bytes_remaining > 0) {
+        int bytes_to_read = min(bytes_remaining, kBlockSize - g_bytes_used);
+        if (bytes_to_read == 0)
+               {
+                       random_block(g_random_data, TRUE);
+                       g_bytes_used = 0;
+                       bytes_to_read = min(bytes_remaining, kBlockSize);
+               }
+               
+               memmove ((u_int8_t*) buffer + bytes_read, ((u_int8_t*)g_random_data)+ g_bytes_used, bytes_to_read);
+               g_bytes_used += bytes_to_read;
+               bytes_read += bytes_to_read;
+               bytes_remaining -= bytes_to_read;
+    }
+
+    lck_mtx_unlock(gYarrowMutex);
 }
 
 /*
- * Return an unsigned long pseudo-random number.
+ * Return an u_int32_t pseudo-random number.
  */
-u_long
-RandomULong()
+u_int32_t
+RandomULong(void)
 {
-       u_long buf;
+       u_int32_t buf;
        read_random(&buf, sizeof (buf));
        return (buf);
 }