166 lines
3.9 KiB
C++
166 lines
3.9 KiB
C++
/* fhandler_dev_random.cc: code to access /dev/random and /dev/urandom
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Copyright 2000 Cygnus Solutions.
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Written by Corinna Vinschen (vinschen@cygnus.com)
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This file is part of Cygwin.
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This software is a copyrighted work licensed under the terms of the
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Cygwin license. Please consult the file "CYGWIN_LICENSE" for
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details. */
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#include "winsup.h"
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#include <errno.h>
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#include <limits.h>
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#include "cygerrno.h"
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#define RANDOM 8
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#define URANDOM 9
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#define PSEUDO_MULTIPLIER (6364136223846793005LL)
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#define PSEUDO_SHIFTVAL (21)
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fhandler_dev_random::fhandler_dev_random (const char *name, int nunit)
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: fhandler_base (FH_RANDOM, name),
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unit(nunit),
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crypt_prov((HCRYPTPROV)NULL)
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{
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set_cb (sizeof *this);
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}
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int
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fhandler_dev_random::open (const char *, int flags, mode_t)
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{
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set_flags (flags);
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return 1;
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}
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BOOL
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fhandler_dev_random::crypt_gen_random (void *ptr, size_t len)
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{
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if (!crypt_prov
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&& !CryptAcquireContext (&crypt_prov, NULL, MS_DEF_PROV, PROV_RSA_FULL,
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CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET)
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&& !CryptAcquireContext (&crypt_prov, NULL, MS_DEF_PROV, PROV_RSA_FULL,
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CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET
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| CRYPT_NEWKEYSET))
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{
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debug_printf ("%E = CryptAquireContext()");
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return FALSE;
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}
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if (!CryptGenRandom (crypt_prov, len, (BYTE *)ptr))
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{
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debug_printf ("%E = CryptGenRandom()");
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return FALSE;
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}
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return TRUE;
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}
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int
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fhandler_dev_random::pseudo_write (const void *ptr, size_t len)
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{
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/* Use buffer to mess up the pseudo random number generator. */
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for (size_t i = 0; i < len; ++i)
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pseudo = (pseudo + ((unsigned char *)ptr)[i]) * PSEUDO_MULTIPLIER + 1;
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return len;
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}
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int
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fhandler_dev_random::write (const void *ptr, size_t len)
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{
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if (!len)
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return 0;
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if (!ptr)
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{
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set_errno (EINVAL);
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return -1;
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}
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/* Limit len to a value <= 512 since we don't want to overact.
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Copy to local buffer because CryptGenRandom violates const. */
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unsigned char buf[512];
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size_t limited_len = len <= 512 ? len : 512;
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memcpy (buf, ptr, limited_len);
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/* Mess up system entropy source. Return error if device is /dev/random. */
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if (!crypt_gen_random (buf, limited_len) && unit == RANDOM)
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{
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__seterrno ();
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return -1;
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}
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/* Mess up the pseudo random number generator. */
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pseudo_write (buf, limited_len);
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return len;
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}
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int
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fhandler_dev_random::pseudo_read (void *ptr, size_t len)
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{
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/* Use pseudo random number generator as fallback entropy source.
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This multiplier was obtained from Knuth, D.E., "The Art of
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Computer Programming," Vol 2, Seminumerical Algorithms, Third
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Edition, Addison-Wesley, 1998, p. 106 (line 26) & p. 108 */
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for (size_t i = 0; i < len; ++i)
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{
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pseudo = pseudo * PSEUDO_MULTIPLIER + 1;
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((unsigned char *)ptr)[i] = (pseudo >> PSEUDO_SHIFTVAL) & UCHAR_MAX;
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}
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return len;
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}
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int
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fhandler_dev_random::read (void *ptr, size_t len)
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{
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if (!len)
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return 0;
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if (!ptr)
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{
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set_errno (EINVAL);
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return -1;
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}
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if (crypt_gen_random (ptr, len))
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return len;
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/* If device is /dev/urandom, use pseudo number generator as fallback.
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Don't do this for /dev/random since it's intended for uses that need
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very high quality randomness. */
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if (unit == URANDOM)
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return pseudo_read (ptr, len);
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__seterrno ();
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return -1;
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}
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off_t
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fhandler_dev_random::lseek (off_t, int)
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{
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return 0;
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}
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int
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fhandler_dev_random::close (void)
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{
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if (crypt_prov)
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while (!CryptReleaseContext (crypt_prov, 0)
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&& GetLastError () == ERROR_BUSY)
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Sleep(10);
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return 0;
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}
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int
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fhandler_dev_random::dup (fhandler_base *child)
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{
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fhandler_dev_random *fhr = (fhandler_dev_random *) child;
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fhr->unit = unit;
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fhr->crypt_prov = (HCRYPTPROV)NULL;
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return 0;
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}
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void
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fhandler_dev_random::dump ()
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{
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paranoid_printf("here, fhandler_dev_random");
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}
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