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* fhandler.h (class fhandler_dev_random): Add members for managing

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pseudo randomness.
        * fhandler_random.cc: Rearrange. Use pseudo random number generator
        as entropy source if system entropy isn't available and if device is
        used as /dev/urandom. Allow initializing device by calling write().
This commit is contained in:
Corinna Vinschen
2000-07-24 11:33:02 +00:00
parent 5b7d5241fe
commit 9602ffc30b
3 changed files with 100 additions and 16 deletions
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8
winsup/cygwin/ChangeLog
View File

@@ -1,3 +1,11 @@
Mon Jul 24 13:26:00 2000 Corinna Vinschen <corinna@vinschen.de>
* fhandler.h (class fhandler_dev_random): Add members for managing
pseudo randomness.
* fhandler_random.cc: Rearrange. Use pseudo random number generator
as entropy source if system entropy isn't available and if device is
used as /dev/urandom. Allow initializing device by calling write().
Sun Jul 23 23:11:00 2000 Corinna Vinschen <corinna@vinschen.de>
* fhandler.h: Add comment.

5
winsup/cygwin/fhandler.h
View File

@@ -743,6 +743,11 @@ class fhandler_dev_random: public fhandler_base
protected:
int unit;
HCRYPTPROV crypt_prov;
long pseudo;
BOOL crypt_gen_random (void *ptr, size_t len);
int pseudo_write (const void *ptr, size_t len);
int pseudo_read (void *ptr, size_t len);
public:
fhandler_dev_random (const char *name, int unit);

101
winsup/cygwin/fhandler_random.cc
View File

@@ -1,4 +1,4 @@
/* fhandler_dev_random.cc: code to access /dev/random
/* fhandler_dev_random.cc: code to access /dev/random and /dev/urandom
Copyright 2000 Cygnus Solutions.
@@ -11,11 +11,15 @@ Cygwin license. Please consult the file "CYGWIN_LICENSE" for
details. */
#include <errno.h>
#include <limits.h>
#include "winsup.h"
#define RANDOM 8
#define URANDOM 9
#define PSEUDO_MULTIPLIER (6364136223846793005LL)
#define PSEUDO_SHIFTVAL (21)
fhandler_dev_random::fhandler_dev_random (const char *name, int nunit)
: fhandler_base (FH_RANDOM, name),
unit(nunit),
@@ -31,9 +35,76 @@ fhandler_dev_random::open (const char *, int flags, mode_t)
return 1;
}
int
fhandler_dev_random::write (const void *, size_t len)
BOOL
fhandler_dev_random::crypt_gen_random (void *ptr, size_t len)
{
if (!crypt_prov
&& !CryptAcquireContext (&crypt_prov, NULL, MS_DEF_PROV, PROV_RSA_FULL,
CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET)
&& !CryptAcquireContext (&crypt_prov, NULL, MS_DEF_PROV, PROV_RSA_FULL,
CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET
| CRYPT_NEWKEYSET))
{
debug_printf ("%E = CryptAquireContext()");
return FALSE;
}
if (!CryptGenRandom (crypt_prov, len, (BYTE *)ptr))
{
debug_printf ("%E = CryptGenRandom()");
return FALSE;
}
return TRUE;
}
int
fhandler_dev_random::pseudo_write (const void *ptr, size_t len)
{
/* Use buffer to mess up the pseudo random number generator. */
for (size_t i = 0; i < len; ++i)
pseudo = (pseudo + ((unsigned char *)ptr)[i]) * PSEUDO_MULTIPLIER + 1;
return len;
}
int
fhandler_dev_random::write (const void *ptr, size_t len)
{
if (!len)
return 0;
if (!ptr)
{
set_errno (EINVAL);
return -1;
}
/* Limit len to a value <= 512 since we don't want to overact.
Copy to local buffer because CryptGenRandom violates const. */
unsigned char buf[512];
size_t limited_len = len <= 512 ? len : 512;
memcpy (buf, ptr, limited_len);
/* Mess up system entropy source. Return error if device is /dev/random. */
if (!crypt_gen_random (buf, limited_len) && unit == RANDOM)
{
__seterrno ();
return -1;
}
/* Mess up the pseudo random number generator. */
pseudo_write (buf, limited_len);
return len;
}
int
fhandler_dev_random::pseudo_read (void *ptr, size_t len)
{
/* Use pseudo random number generator as fallback entropy source.
This multiplier was obtained from Knuth, D.E., "The Art of
Computer Programming," Vol 2, Seminumerical Algorithms, Third
Edition, Addison-Wesley, 1998, p. 106 (line 26) & p. 108 */
for (size_t i = 0; i < len; ++i)
{
pseudo = pseudo * PSEUDO_MULTIPLIER + 1;
((unsigned char *)ptr)[i] = (pseudo >> PSEUDO_SHIFTVAL) & UCHAR_MAX;
}
return len;
}
@@ -42,22 +113,22 @@ fhandler_dev_random::read (void *ptr, size_t len)
{
if (!len)
return 0;
if (!crypt_prov
&& !CryptAcquireContext (&crypt_prov, NULL, MS_DEF_PROV, PROV_RSA_FULL,
CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET)
&& !CryptAcquireContext (&crypt_prov, NULL, MS_DEF_PROV, PROV_RSA_FULL,
CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET
| CRYPT_NEWKEYSET ))
if (!ptr)
{
__seterrno ();
return -1;
}
if (!CryptGenRandom (crypt_prov, len, (BYTE *)ptr))
{
__seterrno ();
set_errno (EINVAL);
return -1;
}
if (crypt_gen_random (ptr, len))
return len;
/* If device is /dev/urandom, use pseudo number generator as fallback.
Don't do this for /dev/random since it's intended for uses that need
very high quality randomness. */
if (unit == URANDOM)
return pseudo_read (ptr, len);
__seterrno ();
return -1;
}
off_t