]> git.saurik.com Git - apple/xnu.git/blobdiff - bsd/dev/random/randomdev.c
xnu-6153.141.1.tar.gz
[apple/xnu.git] / bsd / dev / random / randomdev.c
index 6f99d775d205f5e1eb1fad86c65703acc0adae51..7e5e10e3ea39578e4b774156b670b77c7c135118 100644 (file)
@@ -1,8 +1,8 @@
 /*
- * Copyright (c)1999-2004 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 1999-2009 Apple, 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
  * 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
  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  * Please see the License for the specific language governing rights and
  * limitations under the License.
- * 
+ *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  */
 
+
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/proc.h>
 #include <sys/fcntl.h>
 #include <string.h>
 #include <miscfs/devfs/devfs.h>
-#include <kern/lock.h>
+#include <kern/locks.h>
+#include <kern/clock.h>
 #include <sys/time.h>
 #include <sys/malloc.h>
+#include <sys/sysproto.h>
 #include <sys/uio_internal.h>
 
 #include <dev/random/randomdev.h>
-#include <dev/random/YarrowCoreLib/include/yarrow.h>
-#include <crypto/sha1.h>
+
+#include <libkern/OSByteOrder.h>
+#include <libkern/OSAtomic.h>
+
+#include <mach/mach_time.h>
 
 #define RANDOM_MAJOR  -1 /* let the kernel pick the device number */
+#define RANDOM_MINOR   0
+#define URANDOM_MINOR  1
 
 d_ioctl_t       random_ioctl;
 
@@ -54,260 +62,22 @@ d_ioctl_t       random_ioctl;
  */
 static struct cdevsw random_cdevsw =
 {
-       random_open,            /* open */
-       random_close,           /* close */
-       random_read,            /* read */
-       random_write,           /* write */
-       random_ioctl,           /* ioctl */
+       random_open,            /* open */
+       random_close,           /* close */
+       random_read,            /* read */
+       random_write,           /* write */
+       random_ioctl,           /* ioctl */
        (stop_fcn_t *)nulldev, /* stop */
        (reset_fcn_t *)nulldev, /* reset */
-       NULL,                           /* tty's */
-       eno_select,                     /* select */
-       eno_mmap,                       /* mmap */
-       eno_strat,                      /* strategy */
-       eno_getc,                       /* getc */
-       eno_putc,                       /* putc */
-       0                                       /* type */
-};
-
-/* Used to detect whether we've already been initialized */
-static int gRandomInstalled = 0;
-static PrngRef gPrngRef;
-static int gRandomError = 1;
-static mutex_t *gYarrowMutex = 0;
-
-#define RESEED_TICKS 50 /* how long a reseed operation can take */
-
-
-enum {kBSizeInBits = 160}; // MUST be a multiple of 32!!!
-enum {kBSizeInBytes = kBSizeInBits / 8};
-typedef u_int32_t BlockWord;
-enum {kWordSizeInBits = 32};
-enum {kBSize = 5};
-typedef BlockWord Block[kBSize];
-
-/* 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);
-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 = kBSize;
-       while (--i >= 0)
-       {
-               u_int64_t c = (u_int64_t)carry +
-                                         (u_int64_t)a[i] +
-                                         (u_int64_t)b[i];
-               a[i] = c & ((1LL << kWordSizeInBits) - 1);
-               carry = c >> kWordSizeInBits;
-       }
-}
-
-
-
-struct sha1_ctxt g_sha1_ctx;
-char zeros[(512 - kBSizeInBits) / 8];
-Block g_xkey;
-Block g_random_data;
-int g_bytes_used;
-unsigned char g_SelfTestInitialized = 0;
-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,
+       NULL,                           /* tty's */
+       eno_select,                     /* select */
+       eno_mmap,                       /* mmap */
+       eno_strat,                      /* strategy */
+       eno_getc,                       /* getc */
+       eno_putc,                       /* putc */
+       0                                       /* type */
 };
 
-/*
- * 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 repeatCount = 0;
-       do
-       {
-               // do one iteration
-               Block xSeed;
-               prngOutput (gPrngRef, (BYTE*) &xSeed, sizeof (xSeed));
-               
-               // add the seed to the previous value of g_xkey
-               add_blocks (g_xkey, xSeed, 0);
-
-               // compute "G"
-               SHA1Update (&g_sha1_ctx, (const u_int8_t *) &g_xkey, sizeof (g_xkey));
-               
-               // add zeros to fill the internal SHA-1 buffer
-               SHA1Update (&g_sha1_ctx, (const u_int8_t *)zeros, sizeof (zeros));
-               
-               // write the resulting block
-               memmove(b, g_sha1_ctx.h.b8, sizeof (Block));
-               
-               // calculate the CRC-32 of the block
-               u_int32_t new_crc = CalculateCRC(g_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)
-{
-    prng_error_status perr;
-    struct timeval tt;
-    char buffer [16];
-
-    /* create a Yarrow object */
-    perr = prngInitialize(&gPrngRef);
-    if (perr != 0) {
-        printf ("Couldn't initialize Yarrow, /dev/random will not work.\n");
-        return;
-    }
-
-       /* clear the error flag, reads and write should then work */
-    gRandomError = 0;
-
-    /* get a little non-deterministic data as an initial seed. */
-    microtime(&tt);
-
-    /*
-        * So how much of the system clock is entropic?
-        * It's hard to say, but assume that at least the
-        * least significant byte of a 64 bit structure
-        * is entropic.  It's probably more, how can you figure
-        * the exact time the user turned the computer on, for example.
-    */
-    perr = prngInput(gPrngRef, (BYTE*) &tt, sizeof (tt), SYSTEM_SOURCE, 8);
-    if (perr != 0) {
-        /* an error, complain */
-        printf ("Couldn't seed Yarrow.\n");
-        return;
-    }
-    
-    /* turn the data around */
-    perr = prngOutput(gPrngRef, (BYTE*)buffer, sizeof (buffer));
-    
-    /* and scramble it some more */
-    perr = prngForceReseed(gPrngRef, RESEED_TICKS);
-    
-    /* make a mutex to control access */
-    gYarrowMutex = mutex_alloc(0);
-       
-       fips_initialize ();
-}
-
-void
-fips_initialize(void)
-{
-       /* Read the initial value of g_xkey from yarrow */
-       prngOutput (gPrngRef, (BYTE*) &g_xkey, sizeof (g_xkey));
-       
-       /* initialize our SHA1 generator */
-       SHA1Init (&g_sha1_ctx);
-       
-       /* other initializations */
-       memset (zeros, 0, sizeof (zeros));
-       g_bytes_used = 0;
-       random_block(g_random_data);
-}
 
 /*
  * Called to initialize our device,
@@ -318,36 +88,25 @@ random_init(void)
 {
        int ret;
 
-       if (gRandomInstalled)
-               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) {
-               printf("random_init: failed to allocate a major number!\n");
-               gRandomInstalled = 0;
-               return;
+               panic("random_init: failed to allocate a major number!");
        }
 
-       devfs_make_node(makedev (ret, 0), DEVFS_CHAR,
-               UID_ROOT, GID_WHEEL, 0666, "random", 0);
+       devfs_make_node(makedev(ret, RANDOM_MINOR), DEVFS_CHAR,
+           UID_ROOT, GID_WHEEL, 0666, "random", 0);
 
        /*
-        * also make urandom 
+        * also make urandom
         * (which is exactly the same thing in our context)
         */
-       devfs_make_node(makedev (ret, 1), DEVFS_CHAR,
-               UID_ROOT, GID_WHEEL, 0666, "urandom", 0);
+       devfs_make_node(makedev(ret, URANDOM_MINOR), DEVFS_CHAR,
+           UID_ROOT, GID_WHEEL, 0666, "urandom", 0);
 }
 
 int
-random_ioctl(  __unused dev_t dev, u_long cmd, __unused caddr_t data, 
-                               __unused int flag, __unused struct proc *p  )
+random_ioctl(   __unused dev_t dev, u_long cmd, __unused caddr_t data,
+    __unused int flag, __unused struct proc *p  )
 {
        switch (cmd) {
        case FIONBIO:
@@ -357,47 +116,44 @@ random_ioctl(     __unused dev_t dev, u_long cmd, __unused caddr_t data,
                return ENODEV;
        }
 
-       return (0);
+       return 0;
 }
 
 /*
  * Open the device.  Make sure init happened, and make sure the caller is
  * authorized.
  */
+
 int
 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 */
-               return (ENOTSUP);
-       }
-
        /*
         * if we are being opened for write,
         * make sure that we have privledges do so
         */
        if (flags & FWRITE) {
-               if (securelevel >= 2)
-                       return (EPERM);
+               if (securelevel >= 2) {
+                       return EPERM;
+               }
 #ifndef __APPLE__
-               if ((securelevel >= 1) && proc_suser(p))
-                       return (EPERM);
-#endif /* !__APPLE__ */
+               if ((securelevel >= 1) && proc_suser(p)) {
+                       return EPERM;
+               }
+#endif  /* !__APPLE__ */
        }
 
-       return (0);
+       return 0;
 }
 
 
 /*
  * close the device.
  */
+
 int
 random_close(__unused dev_t dev, __unused int flags, __unused int mode, __unused struct proc *p)
 {
-       return (0);
+       return 0;
 }
 
 
@@ -406,133 +162,87 @@ random_close(__unused dev_t dev, __unused int flags, __unused int mode, __unused
  * prng.
  */
 int
-random_write (__unused dev_t dev, struct uio *uio, __unused int ioflag)
+random_write(dev_t dev, struct uio *uio, __unused int ioflag)
 {
-    int retCode = 0;
-    char rdBuffer[256];
-
-    if (gRandomError != 0) {
-        return (ENOTSUP);
-    }
-    
-    /* get control of the Yarrow instance, Yarrow is NOT thread safe */
-    mutex_lock(gYarrowMutex);
-    
-    /* Security server is sending us entropy */
-
-    while (uio_resid(uio) > 0 && retCode == 0) {
-        /* get the user's data */
-        // LP64todo - fix this!  uio_resid may be 64-bit value
-        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,
-                       bytesToInput, SYSTEM_SOURCE,
-               bytesToInput * 8) != 0) {
-            retCode = EIO;
-            goto error_exit;
-        }
-    }
-    
-    /* force a reseed */
-    if (prngForceReseed(gPrngRef, RESEED_TICKS) != 0) {
-        retCode = EIO;
-        goto error_exit;
-    }
-    
-    /* retCode should be 0 at this point */
-    
-error_exit: /* do this to make sure the mutex unlocks. */
-    mutex_unlock(gYarrowMutex);
-    return (retCode);
+       int retCode = 0;
+       char rdBuffer[256];
+
+       if (minor(dev) != RANDOM_MINOR) {
+               return EPERM;
+       }
+
+       /* Security server is sending us entropy */
+
+       while (uio_resid(uio) > 0 && retCode == 0) {
+               /* get the user's data */
+               int bytesToInput = MIN(uio_resid(uio),
+                   (user_ssize_t) sizeof(rdBuffer));
+               retCode = uiomove(rdBuffer, bytesToInput, uio);
+               if (retCode != 0) {
+                       break;
+               }
+               retCode = write_random(rdBuffer, bytesToInput);
+               if (retCode != 0) {
+                       break;
+               }
+       }
+
+       return retCode;
 }
 
 /*
  * return data to the caller.  Results unpredictable.
- */ 
-int random_read(__unused dev_t dev, struct uio *uio, __unused int ioflag)
+ */
+int
+random_read(__unused dev_t dev, struct uio *uio, __unused int ioflag)
 {
-    int retCode = 0;
-       
-    if (gRandomError != 0)
-        return (ENOTSUP);
-
-   /* lock down the mutex */
-    mutex_lock(gYarrowMutex);
-
-       int bytes_remaining = uio_resid(uio);
-    while (bytes_remaining > 0 && retCode == 0) {
-        /* get the user's data */
-               int bytes_to_read = 0;
-               
-               int bytes_available = kBSizeInBytes - g_bytes_used;
-        if (bytes_available == 0)
-               {
-                       random_block(g_random_data);
-                       g_bytes_used = 0;
-                       bytes_available = kBSizeInBytes;
+       int retCode = 0;
+       char buffer[512];
+
+       user_ssize_t bytes_remaining = uio_resid(uio);
+       while (bytes_remaining > 0 && retCode == 0) {
+               int bytesToRead = MIN(bytes_remaining,
+                   (user_ssize_t) sizeof(buffer));
+               read_random(buffer, bytesToRead);
+
+               retCode = uiomove(buffer, bytesToRead, uio);
+               if (retCode != 0) {
+                       break;
                }
-               
-               bytes_to_read = min (bytes_remaining, bytes_available);
-               
-        retCode = uiomove(((u_int8_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);
-    return retCode;
-}
+       }
 
-/* export good random numbers to the rest of the kernel */
-void
-read_random(void* buffer, u_int numbytes)
-{
-    if (gYarrowMutex == 0) { /* are we initialized? */
-        PreliminarySetup ();
-    }
-    
-    mutex_lock(gYarrowMutex);
-       
-       int bytes_read = 0;
-
-       int bytes_remaining = numbytes;
-    while (bytes_remaining > 0) {
-        int bytes_to_read = min(bytes_remaining, kBSizeInBytes - g_bytes_used);
-        if (bytes_to_read == 0)
-               {
-                       random_block(g_random_data);
-                       g_bytes_used = 0;
-                       bytes_to_read = min(bytes_remaining, kBSizeInBytes);
-               }
-               
-               memmove (buffer, ((u_int8_t*)g_random_data)+ bytes_read, bytes_to_read);
-               g_bytes_used += bytes_to_read;
-               bytes_read += bytes_to_read;
-               bytes_remaining -= bytes_to_read;
-    }
-
-    mutex_unlock(gYarrowMutex);
+       return retCode;
 }
 
 /*
- * Return an unsigned long pseudo-random number.
+ * Return an u_int32_t pseudo-random number.
  */
-u_long
+u_int32_t
 RandomULong(void)
 {
-       u_long buf;
-       read_random(&buf, sizeof (buf));
-       return (buf);
+       u_int32_t buf;
+       read_random(&buf, sizeof(buf));
+       return buf;
 }
 
+
+int
+getentropy(__unused struct proc * p, struct getentropy_args *gap, __unused int * ret)
+{
+       user_addr_t user_addr;
+       uint32_t user_size;
+       char buffer[256];
+
+       user_addr = (vm_map_offset_t)gap->buffer;
+       user_size = gap->size;
+       /* Can't request more than 256 random bytes
+        * at once. Complying with openbsd getentropy()
+        */
+       if (user_size > sizeof(buffer)) {
+               return EINVAL;
+       }
+       read_random(buffer, user_size);
+       return copyout(buffer, user_addr, user_size);
+}