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b121d029b5
gnupg/cipher/random.c
Werner Koch b121d029b5 about to release 1.4.3rc1
2006-02-14 16:28:34 +00:00

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/* random.c - random number generator
* Copyright (C) 1998, 1999, 2000, 2001, 2002,
* 2003, 2006 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
* GnuPG is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* GnuPG is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA.
*/
/****************
* This random number generator is modelled after the one described
* in Peter Gutmann's Paper: "Software Generation of Practically
* Strong Random Numbers".
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <time.h>
#ifndef _WIN32
#include <sys/time.h>
#endif
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#ifdef HAVE_GETHRTIME
#include <sys/times.h>
#endif
#ifdef HAVE_GETTIMEOFDAY
#include <sys/times.h>
#endif
#ifdef HAVE_TIMES
#include <sys/times.h>
#endif
#ifdef HAVE_GETRUSAGE
#include <sys/resource.h>
#endif
#ifdef _WIN32
#include <process.h>
#endif
#include "util.h"
#include "rmd.h"
#include "ttyio.h"
#include "i18n.h"
#include "random.h"
#include "rand-internal.h"
#include "algorithms.h"
#ifndef RAND_MAX /* for SunOS */
#define RAND_MAX 32767
#endif
/* Check whether we can lock the seed file read write. */
#if defined(HAVE_FCNTL) && defined(HAVE_FTRUNCATE) && !defined(HAVE_W32_SYSTEM)
#define LOCK_SEED_FILE 1
#else
#define LOCK_SEED_FILE 0
#endif
#if SIZEOF_UNSIGNED_LONG == 8
#define ADD_VALUE 0xa5a5a5a5a5a5a5a5
#elif SIZEOF_UNSIGNED_LONG == 4
#define ADD_VALUE 0xa5a5a5a5
#else
#error weird size for an unsigned long
#endif
#define BLOCKLEN 64 /* hash this amount of bytes */
#define DIGESTLEN 20 /* into a digest of this length (rmd160) */
/* poolblocks is the number of digests which make up the pool
* and poolsize must be a multiple of the digest length
* to make the AND operations faster, the size should also be
* a multiple of ulong
*/
#define POOLBLOCKS 30
#define POOLSIZE (POOLBLOCKS*DIGESTLEN)
#if (POOLSIZE % SIZEOF_UNSIGNED_LONG)
#error Please make sure that poolsize is a multiple of ulong
#endif
#define POOLWORDS (POOLSIZE / SIZEOF_UNSIGNED_LONG)
static int is_initialized;
#define MASK_LEVEL(a) do {if( a > 2 ) a = 2; else if( a < 0 ) a = 0; } while(0)
static char *rndpool; /* allocated size is POOLSIZE+BLOCKLEN */
static char *keypool; /* allocated size is POOLSIZE+BLOCKLEN */
static size_t pool_readpos;
static size_t pool_writepos;
static int pool_filled;
static int pool_balance;
static int just_mixed;
static int did_initial_extra_seeding;
static char *seed_file_name;
static int allow_seed_file_update;
static int no_seed_file_locking;
static int secure_alloc;
static int quick_test;
static int faked_rng;
static void read_pool( byte *buffer, size_t length, int level );
static void add_randomness( const void *buffer, size_t length, int source );
static void random_poll(void);
static void read_random_source( int requester, size_t length, int level);
static int gather_faked( void (*add)(const void*, size_t, int), int requester,
size_t length, int level );
static struct {
ulong mixrnd;
ulong mixkey;
ulong slowpolls;
ulong fastpolls;
ulong getbytes1;
ulong ngetbytes1;
ulong getbytes2;
ulong ngetbytes2;
ulong addbytes;
ulong naddbytes;
} rndstats;
static int (*
getfnc_gather_random (void))(void (*)(const void*, size_t, int), int,
size_t, int)
{
#ifdef USE_ALL_RANDOM_MODULES
static int (*fnc)(void (*)(const void*, size_t, int), int, size_t, int);
if (fnc)
return fnc;
# ifdef USE_RNDLINUX
if ( !access (NAME_OF_DEV_RANDOM, R_OK)
&& !access (NAME_OF_DEV_URANDOM, R_OK))
{
fnc = rndlinux_gather_random;
return fnc;
}
# endif
# ifdef USE_RNDEGD
if ( rndegd_connect_socket (1) != -1 )
{
fnc = rndegd_gather_random;
return fnc;
}
# endif
# ifdef USE_RNDUNIX
fnc = rndunix_gather_random;
return fnc;
# endif
log_fatal (_("no entropy gathering module detected\n"));
#else
# ifdef USE_RNDLINUX
return rndlinux_gather_random;
# endif
# ifdef USE_RNDUNIX
return rndunix_gather_random;
# endif
# ifdef USE_RNDEGD
return rndegd_gather_random;
# endif
# ifdef USE_RNDW32
return rndw32_gather_random;
# endif
# ifdef USE_RNDRISCOS
return rndriscos_gather_random;
# endif
#endif
return NULL;
}
static int (*
getfnc_fast_random_poll (void))( void (*)(const void*, size_t, int), int)
{
#ifdef USE_RNDW32
return rndw32_gather_random_fast;
#endif
return NULL;
}
static void
initialize(void)
{
/* The data buffer is allocated somewhat larger, so that
* we can use this extra space (which is allocated in secure memory)
* as a temporary hash buffer */
rndpool = secure_alloc ? xmalloc_secure_clear(POOLSIZE+BLOCKLEN)
: xmalloc_clear(POOLSIZE+BLOCKLEN);
keypool = secure_alloc ? xmalloc_secure_clear(POOLSIZE+BLOCKLEN)
: xmalloc_clear(POOLSIZE+BLOCKLEN);
is_initialized = 1;
}
static void
burn_stack (int bytes)
{
char buf[128];
wipememory(buf,sizeof buf);
bytes -= sizeof buf;
if (bytes > 0)
burn_stack (bytes);
}
void
random_dump_stats()
{
fprintf(stderr,
"random usage: poolsize=%d mixed=%lu polls=%lu/%lu added=%lu/%lu\n"
" outmix=%lu getlvl1=%lu/%lu getlvl2=%lu/%lu\n",
POOLSIZE, rndstats.mixrnd, rndstats.slowpolls, rndstats.fastpolls,
rndstats.naddbytes, rndstats.addbytes,
rndstats.mixkey, rndstats.ngetbytes1, rndstats.getbytes1,
rndstats.ngetbytes2, rndstats.getbytes2 );
}
void
secure_randoxmalloc()
{
secure_alloc = 1;
}
int
quick_random_gen( int onoff )
{
int last;
read_random_source(0,0,0); /* init */
last = quick_test;
if( onoff != -1 )
quick_test = onoff;
return faked_rng? 1 : last;
}
/****************
* Fill the buffer with LENGTH bytes of cryptographically strong
* random bytes. level 0 is not very strong, 1 is strong enough
* for most usage, 2 is good for key generation stuff but may be very slow.
*/
void
randomize_buffer( byte *buffer, size_t length, int level )
{
char *p = get_random_bits( length*8, level, 1 );
memcpy( buffer, p, length );
xfree(p);
}
int
random_is_faked()
{
if( !is_initialized )
initialize();
return faked_rng || quick_test;
}
/* Disable locking of seed files. */
void
random_disable_locking ()
{
no_seed_file_locking = 1;
}
/****************
* Return a pointer to a randomized buffer of level 0 and LENGTH bits
* caller must free the buffer.
* Note: The returned value is rounded up to bytes.
*/
byte *
get_random_bits( size_t nbits, int level, int secure )
{
byte *buf, *p;
size_t nbytes = (nbits+7)/8;
if( quick_test && level > 1 )
level = 1;
MASK_LEVEL(level);
if( level == 1 ) {
rndstats.getbytes1 += nbytes;
rndstats.ngetbytes1++;
}
else if( level >= 2 ) {
rndstats.getbytes2 += nbytes;
rndstats.ngetbytes2++;
}
buf = secure && secure_alloc ? xmalloc_secure( nbytes ) : xmalloc( nbytes );
for( p = buf; nbytes > 0; ) {
size_t n = nbytes > POOLSIZE? POOLSIZE : nbytes;
read_pool( p, n, level );
nbytes -= n;
p += n;
}
return buf;
}
/****************
* Mix the pool
*/
static void
mix_pool(byte *pool)
{
char *hashbuf = pool + POOLSIZE;
char *p, *pend;
int i, n;
RMD160_CONTEXT md;
rmd160_init( &md );
#if DIGESTLEN != 20
#error must have a digest length of 20 for ripe-md-160
#endif
/* loop over the pool */
pend = pool + POOLSIZE;
memcpy(hashbuf, pend - DIGESTLEN, DIGESTLEN );
memcpy(hashbuf+DIGESTLEN, pool, BLOCKLEN-DIGESTLEN);
rmd160_mixblock( &md, hashbuf);
memcpy(pool, hashbuf, 20 );
p = pool;
for( n=1; n < POOLBLOCKS; n++ ) {
memcpy(hashbuf, p, DIGESTLEN );
p += DIGESTLEN;
if( p+DIGESTLEN+BLOCKLEN < pend )
memcpy(hashbuf+DIGESTLEN, p+DIGESTLEN, BLOCKLEN-DIGESTLEN);
else {
char *pp = p+DIGESTLEN;
for(i=DIGESTLEN; i < BLOCKLEN; i++ ) {
if( pp >= pend )
pp = pool;
hashbuf[i] = *pp++;
}
}
rmd160_mixblock( &md, hashbuf);
memcpy(p, hashbuf, 20 );
}
burn_stack (384); /* for the rmd160_mixblock() */
}
void
set_random_seed_file( const char *name )
{
if( seed_file_name )
BUG();
seed_file_name = xstrdup( name );
}
/* Lock an open file identified by file descriptor FD and wait a
reasonable time to succeed. With FOR_WRITE set to true a Rite lock
will be taken. FNAME is used only for diagnostics. Returns 0 on
success or -1 on error. */
static int
lock_seed_file (int fd, const char *fname, int for_write)
{
#if LOCK_SEED_FILE
struct flock lck;
struct timeval tv;
int backoff=0;
if (no_seed_file_locking)
return 0;
/* We take a lock on the entire file. */
memset (&lck, 0, sizeof lck);
lck.l_type = for_write? F_WRLCK : F_RDLCK;
lck.l_whence = SEEK_SET;
while (fcntl (fd, F_SETLK, &lck) == -1)
{
if (errno != EAGAIN && errno != EACCES)
{
log_info (_("can't lock `%s': %s\n"), fname, strerror (errno));
return -1;
}
if (backoff > 2) /* Show the first message after ~2.25 seconds. */
log_info( _("waiting for lock on `%s'...\n"), fname);
tv.tv_sec = backoff;
tv.tv_usec = 250000;
select (0, NULL, NULL, NULL, &tv);
if (backoff < 10)
backoff++ ;
}
#endif /*LOCK_SEED_FILE*/
return 0;
}
/****************
* Read in a seed form the random_seed file
* and return true if this was successful
*/
static int
read_seed_file(void)
{
int fd;
struct stat sb;
unsigned char buffer[POOLSIZE];
int n;
if( !seed_file_name )
return 0;
#if defined(HAVE_DOSISH_SYSTEM) || defined(__CYGWIN__)
fd = open( seed_file_name, O_RDONLY | O_BINARY );
#else
fd = open( seed_file_name, O_RDONLY );
#endif
if( fd == -1 && errno == ENOENT) {
allow_seed_file_update = 1;
return 0;
}
if( fd == -1 ) {
log_info(_("can't open `%s': %s\n"), seed_file_name, strerror(errno) );
return 0;
}
if (lock_seed_file (fd, seed_file_name, 0))
{
close (fd);
return 0;
}
if( fstat( fd, &sb ) ) {
log_info(_("can't stat `%s': %s\n"), seed_file_name, strerror(errno) );
close(fd);
return 0;
}
if( !S_ISREG(sb.st_mode) ) {
log_info(_("`%s' is not a regular file - ignored\n"), seed_file_name );
close(fd);
return 0;
}
if( !sb.st_size ) {
log_info(_("note: random_seed file is empty\n") );
close(fd);
allow_seed_file_update = 1;
return 0;
}
if( sb.st_size != POOLSIZE ) {
log_info(_("WARNING: invalid size of random_seed file - not used\n") );
close(fd);
return 0;
}
do {
n = read( fd, buffer, POOLSIZE );
} while( n == -1 && errno == EINTR );
if( n != POOLSIZE ) {
log_fatal(_("can't read `%s': %s\n"), seed_file_name,strerror(errno) );
close(fd);
return 0;
}
close(fd);
add_randomness( buffer, POOLSIZE, 0 );
/* add some minor entropy to the pool now (this will also force a mixing) */
{ pid_t x = getpid();
add_randomness( &x, sizeof(x), 0 );
}
{ time_t x = time(NULL);
add_randomness( &x, sizeof(x), 0 );
}
{ clock_t x = clock();
add_randomness( &x, sizeof(x), 0 );
}
/* And read a few bytes from our entropy source. By using
* a level of 0 this will not block and might not return anything
* with some entropy drivers, however the rndlinux driver will use
* /dev/urandom and return some stuff - Do not read to much as we
* want to be friendly to the scare system entropy resource. */
read_random_source( 0, 16, 0 );
allow_seed_file_update = 1;
return 1;
}
void
update_random_seed_file()
{
ulong *sp, *dp;
int fd, i;
if( !seed_file_name || !is_initialized || !pool_filled )
return;
if( !allow_seed_file_update ) {
log_info(_("note: random_seed file not updated\n"));
return;
}
/* copy the entropy pool to a scratch pool and mix both of them */
for(i=0,dp=(ulong*)keypool, sp=(ulong*)rndpool;
i < POOLWORDS; i++, dp++, sp++ ) {
*dp = *sp + ADD_VALUE;
}
mix_pool(rndpool); rndstats.mixrnd++;
mix_pool(keypool); rndstats.mixkey++;
#if defined(HAVE_DOSISH_SYSTEM) || defined(__CYGWIN__)
fd = open( seed_file_name, O_WRONLY|O_CREAT|O_TRUNC|O_BINARY,
S_IRUSR|S_IWUSR );
#else
# if LOCK_SEED_FILE
fd = open( seed_file_name, O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR );
# else
fd = open( seed_file_name, O_WRONLY|O_CREAT|O_TRUNC, S_IRUSR|S_IWUSR );
# endif
#endif
if( fd == -1 ) {
log_info(_("can't create `%s': %s\n"), seed_file_name, strerror(errno) );
return;
}
if (lock_seed_file (fd, seed_file_name, 1))
{
close (fd);
return;
}
#if LOCK_SEED_FILE
if (ftruncate (fd, 0))
{
log_info(_("can't write `%s': %s\n"), seed_file_name, strerror(errno));
close (fd);
return;
}
#endif /*LOCK_SEED_FILE*/
do {
i = write( fd, keypool, POOLSIZE );
} while( i == -1 && errno == EINTR );
if( i != POOLSIZE ) {
log_info(_("can't write `%s': %s\n"), seed_file_name, strerror(errno) );
}
if( close(fd) )
log_info(_("can't close `%s': %s\n"), seed_file_name, strerror(errno) );
}
static void
read_pool( byte *buffer, size_t length, int level )
{
int i;
ulong *sp, *dp;
if( length > POOLSIZE ) {
log_bug("too many random bits requested\n");
}
if( !pool_filled ) {
if( read_seed_file() )
pool_filled = 1;
}
/* For level 2 quality (key generation) we alwas make
* sure that the pool has been seeded enough initially */
if( level == 2 && !did_initial_extra_seeding ) {
size_t needed;
pool_balance = 0;
needed = length - pool_balance;
if( needed < POOLSIZE/2 )
needed = POOLSIZE/2;
else if( needed > POOLSIZE )
BUG();
read_random_source( 3, needed, 2 );
pool_balance += needed;
did_initial_extra_seeding=1;
}
/* for level 2 make sure that there is enough random in the pool */
if( level == 2 && pool_balance < length ) {
size_t needed;
if( pool_balance < 0 )
pool_balance = 0;
needed = length - pool_balance;
if( needed > POOLSIZE )
BUG();
read_random_source( 3, needed, 2 );
pool_balance += needed;
}
/* make sure the pool is filled */
while( !pool_filled )
random_poll();
/* do always a fast random poll */
fast_random_poll();
if( !level ) { /* no need for cryptographic strong random */
/* create a new pool */
for(i=0,dp=(ulong*)keypool, sp=(ulong*)rndpool;
i < POOLWORDS; i++, dp++, sp++ )
*dp = *sp + ADD_VALUE;
/* must mix both pools */
mix_pool(rndpool); rndstats.mixrnd++;
mix_pool(keypool); rndstats.mixkey++;
memcpy( buffer, keypool, length );
}
else {
/* mix the pool (if add_randomness() didn't it) */
if( !just_mixed ) {
mix_pool(rndpool);
rndstats.mixrnd++;
}
/* create a new pool */
for(i=0,dp=(ulong*)keypool, sp=(ulong*)rndpool;
i < POOLWORDS; i++, dp++, sp++ )
*dp = *sp + ADD_VALUE;
/* and mix both pools */
mix_pool(rndpool); rndstats.mixrnd++;
mix_pool(keypool); rndstats.mixkey++;
/* read the required data
* we use a readpoiter to read from a different postion each
* time */
while( length-- ) {
*buffer++ = keypool[pool_readpos++];
if( pool_readpos >= POOLSIZE )
pool_readpos = 0;
pool_balance--;
}
if( pool_balance < 0 )
pool_balance = 0;
/* and clear the keypool */
wipememory(keypool, POOLSIZE);
}
}
/****************
* Add LENGTH bytes of randomness from buffer to the pool.
* source may be used to specify the randomness source.
* Source is:
* 0 - used ony for initialization
* 1 - fast random poll function
* 2 - normal poll function
* 3 - used when level 2 random quality has been requested
* to do an extra pool seed.
*/
static void
add_randomness( const void *buffer, size_t length, int source )
{
const byte *p = buffer;
if( !is_initialized )
initialize();
rndstats.addbytes += length;
rndstats.naddbytes++;
while( length-- ) {
rndpool[pool_writepos++] ^= *p++;
if( pool_writepos >= POOLSIZE ) {
if( source > 1 )
pool_filled = 1;
pool_writepos = 0;
mix_pool(rndpool); rndstats.mixrnd++;
just_mixed = !length;
}
}
}
static void
random_poll()
{
rndstats.slowpolls++;
read_random_source( 2, POOLSIZE/5, 1 );
}
void
fast_random_poll()
{
static int (*fnc)( void (*)(const void*, size_t, int), int) = NULL;
static int initialized = 0;
rndstats.fastpolls++;
if( !initialized ) {
if( !is_initialized )
initialize();
initialized = 1;
fnc = getfnc_fast_random_poll();
}
if( fnc ) {
(*fnc)( add_randomness, 1 );
return;
}
/* fall back to the generic function */
#if defined(HAVE_GETHRTIME) && !defined(HAVE_BROKEN_GETHRTIME)
{ hrtime_t tv;
/* On some Solaris and HPUX system gethrtime raises an SIGILL, but we
* checked this with configure */
tv = gethrtime();
add_randomness( &tv, sizeof(tv), 1 );
}
#elif defined (HAVE_GETTIMEOFDAY)
{ struct timeval tv;
if( gettimeofday( &tv, NULL ) )
BUG();
add_randomness( &tv.tv_sec, sizeof(tv.tv_sec), 1 );
add_randomness( &tv.tv_usec, sizeof(tv.tv_usec), 1 );
}
#elif defined (HAVE_CLOCK_GETTIME)
{ struct timespec tv;
if( clock_gettime( CLOCK_REALTIME, &tv ) == -1 )
BUG();
add_randomness( &tv.tv_sec, sizeof(tv.tv_sec), 1 );
add_randomness( &tv.tv_nsec, sizeof(tv.tv_nsec), 1 );
}
#elif defined (HAVE_TIMES)
{ struct tms buf;
if( times( &buf ) == -1 )
BUG();
add_randomness( &buf, sizeof buf, 1 );
}
#endif
#ifdef HAVE_GETRUSAGE
#ifndef RUSAGE_SELF
#ifdef __GCC__
#warning There is no RUSAGE_SELF on this system
#endif
#else
{ struct rusage buf;
/* QNX/Neutrino does return ENOSYS - so we just ignore it and
* add whatever is in buf. In a chroot environment it might not
* work at all (i.e. because /proc/ is not accessible), so we better
* ignore all error codes and hope for the best
*/
getrusage( RUSAGE_SELF, &buf );
add_randomness( &buf, sizeof buf, 1 );
wipememory( &buf, sizeof buf );
}
#endif
#endif
/* time and clock are available on all systems - so
* we better do it just in case one of the above functions
* didn't work */
{ time_t x = time(NULL);
add_randomness( &x, sizeof(x), 1 );
}
{ clock_t x = clock();
add_randomness( &x, sizeof(x), 1 );
}
}
static void
read_random_source( int requester, size_t length, int level )
{
static int (*fnc)(void (*)(const void*, size_t, int), int,
size_t, int) = NULL;
if( !fnc ) {
if( !is_initialized )
initialize();
fnc = getfnc_gather_random();
if( !fnc ) {
faked_rng = 1;
fnc = gather_faked;
}
if( !requester && !length && !level )
return; /* init only */
}
if( (*fnc)( add_randomness, requester, length, level ) < 0 )
log_fatal("No way to gather entropy for the RNG\n");
}
static int
gather_faked( void (*add)(const void*, size_t, int), int requester,
size_t length, int level )
{
static int initialized=0;
size_t n;
char *buffer, *p;
if( !initialized ) {
log_info(_("WARNING: using insecure random number generator!!\n"));
tty_printf(_("The random number generator is only a kludge to let\n"
"it run - it is in no way a strong RNG!\n\n"
"DON'T USE ANY DATA GENERATED BY THIS PROGRAM!!\n\n"));
initialized=1;
#ifdef HAVE_RAND
srand(make_timestamp()*getpid());
#else
srandom(make_timestamp()*getpid());
#endif
}
p = buffer = xmalloc( length );
n = length;
#ifdef HAVE_RAND
while( n-- )
*p++ = ((unsigned)(1 + (int) (256.0*rand()/(RAND_MAX+1.0)))-1);
#else
while( n-- )
*p++ = ((unsigned)(1 + (int) (256.0*random()/(RAND_MAX+1.0)))-1);
#endif
add_randomness( buffer, length, requester );
xfree(buffer);
return 0; /* okay */
}
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