NetBSD-5.0.2/dist/dhcp/dst/prandom.c
#ifndef LINT
static const char rcsid[] = "$Header: /cvsroot/src/dist/dhcp/dst/prandom.c,v 1.4 2005/08/11 17:13:21 drochner Exp $";
#endif
/*
* Portions Copyright (c) 1995-1998 by Trusted Information Systems, Inc.
*
* Permission to use, copy modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND TRUSTED INFORMATION SYSTEMS
* DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
* TRUSTED INFORMATION SYSTEMS BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
* FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
* NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
* WITH THE USE OR PERFORMANCE OF THE SOFTWARE.
*/
#include <stdio.h>
#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>
#include <dirent.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <sys/socket.h>
#define NEED_PRAND_CONF
#include "minires/minires.h"
#include "dst_internal.h"
#include "arpa/nameser.h"
#ifndef DST_NUM_HASHES
#define DST_NUM_HASHES 4
#endif
#ifndef DST_NUMBER_OF_COUNTERS
#define DST_NUMBER_OF_COUNTERS 5 /* 32 * 5 == 160 == SHA(1) > MD5 */
#endif
/*
* the constant below is a prime number to make fixed data structues like
* stat and time wrap over blocks. This adds certain uncertanty to what is
* in each digested block.
* The prime number 2879 has the special property that when
* divided by 2,4 and 6 the result is also a prime numbers
*/
#ifndef DST_RANDOM_BLOCK_SIZE
#define DST_RANDOM_BLOCK_SIZE 2879
#endif
/*
* This constant dictatates how many bits we shift to the right before using a
*/
#ifndef DST_SHIFT
#define DST_SHIFT 9
#endif
/*
* An initalizer that is as bad as any other with half the bits set
*/
#ifndef DST_RANDOM_PATTERN
#define DST_RANDOM_PATTERN 0x8765CA93
#endif
/*
* things must have changed in the last 3600 seconds to be used
*/
#define MAX_OLD 3600
/*
* these two data structure are used to process input data into digests,
*
* The first structure is containts a pointer to a DST HMAC key
* the variables accompanying are used for
* step : select every step byte from input data for the hash
* block: number of data elements going into each hash
* digested: number of data elements digested so far
* curr: offset into the next input data for the first byte.
*/
typedef struct hash {
DST_KEY *key;
void *ctx;
int digested, block, step, curr;
} prand_hash;
/*
* This data structure controlls number of hashes and keeps track of
* overall progress in generating correct number of bytes of output.
* output : array to store the output data in
* needed : how many bytes of output are needed
* filled : number of bytes in output so far.
* bytes : total number of bytes processed by this structure
* file_digest : the HMAC key used to digest files.
*/
typedef struct work {
unsigned needed, filled, bytes;
u_char *output;
prand_hash *hash[DST_NUM_HASHES];
DST_KEY *file_digest;
} dst_work;
/*
* forward function declarations
*/
static int get_dev_random(u_char *output, unsigned size);
static int do_time(dst_work *work);
static int do_ls(dst_work *work);
static int unix_cmd(dst_work *work);
static int digest_file(dst_work *work);
static void force_hash(dst_work *work, prand_hash *hash);
static int do_hash(dst_work *work, prand_hash *hash, const u_char *input,
unsigned size);
static int my_digest(dst_work *tmp, const u_char *input, unsigned size);
static prand_hash *get_hmac_key(int step, int block);
static unsigned own_random(dst_work *work);
/*
* variables used in the quick random number generator
*/
static u_int32_t ran_val = DST_RANDOM_PATTERN;
static u_int32_t ran_cnt = (DST_RANDOM_PATTERN >> 10);
/*
* setting the quick_random generator to particular values or if both
* input parameters are 0 then set it to initial vlaues
*/
void
dst_s_quick_random_set(u_int32_t val, u_int32_t cnt)
{
ran_val = (val == 0) ? DST_RANDOM_PATTERN : val;
ran_cnt = (cnt == 0) ? (DST_RANDOM_PATTERN >> 10) : cnt;
}
/*
* this is a quick and random number generator that seems to generate quite
* good distribution of data
*/
u_int32_t
dst_s_quick_random(int inc)
{
ran_val = ((ran_val >> 13) ^ (ran_val << 19)) ^
((ran_val >> 7) ^ (ran_val << 25));
if (inc > 0) /* only increasing values accepted */
ran_cnt += inc;
ran_val += ran_cnt++;
return (ran_val);
}
/*
* get_dev_random: Function to read /dev/random reliably
* this function returns how many bytes where read from the device.
* port_after.h should set the control variable HAVE_DEV_RANDOM
*/
static int
get_dev_random(u_char *output, unsigned size)
{
#ifdef HAVE_DEV_RANDOM
struct stat st;
int n = 0, fd = -1, s;
s = stat("/dev/random", &st);
if (s == 0 && S_ISCHR(st.st_mode)) {
if ((fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) != -1) {
if ((n = read(fd, output, size)) < 0)
n = 0;
close(fd);
}
return (n);
}
#endif
return (0);
}
/*
* Portable way of getting the time values if gettimeofday is missing
* then compile with -DMISSING_GETTIMEOFDAY time() is POSIX compliant but
* gettimeofday() is not.
* Time of day is predictable, we are looking for the randomness that comes
* the last few bits in the microseconds in the timer are hard to predict when
* this is invoked at the end of other operations
*/
struct timeval *mtime;
static int
do_time(dst_work *work)
{
int cnt = 0;
static u_char tmp[sizeof(struct timeval) + sizeof(struct timezone)];
struct timezone *zone;
zone = (struct timezone *) tmp;
mtime = (struct timeval *)(tmp + sizeof(struct timezone));
gettimeofday(mtime, zone);
cnt = sizeof(tmp);
my_digest(work, tmp, sizeof(tmp));
return (cnt);
}
/*
* this function simulates the ls command, but it uses stat which gives more
* information and is harder to guess
* Each call to this function will visit the next directory on the list of
* directories, in a circular manner.
* return value is the number of bytes added to the temp buffer
*
* do_ls() does not visit subdirectories
* if attacker has access to machine it can guess most of the values seen
* thus it is important to only visit directories that are freqently updated
* Attacker that has access to the network can see network traffic
* when NFS mounted directories are accessed and know exactly the data used
* but may not know exactly in what order data is used.
* Returns the number of bytes that where returned in stat structures
*/
static int
do_ls(dst_work *work)
{
struct dir_info {
uid_t uid;
gid_t gid;
off_t size;
time_t atime, mtime, ctime;
};
static struct dir_info dir_info;
struct stat buf;
struct dirent *entry;
static int i = 0;
static unsigned long d_round = 0;
struct timeval tv;
int n = 0, tb_i = 0, out = 0;
unsigned dir_len;
char file_name[1024];
u_char tmp_buff[1024];
DIR *dir = NULL;
if (dirs[i] == NULL) /* if at the end of the list start over */
i = 0;
if (stat(dirs[i++], &buf)) /* directory does not exist */
return (0);
gettimeofday(&tv,NULL);
if (d_round == 0)
d_round = tv.tv_sec - MAX_OLD;
else if (i==1) /* if starting a new round cut what we accept */
d_round += (tv.tv_sec - d_round)/2;
if (buf.st_atime < d_round)
return (0);
EREPORT(("do_ls i %d filled %4d in_temp %4d\n",
i-1, work->filled, work->in_temp));
memcpy(tmp_buff, &buf, sizeof(buf));
tb_i += sizeof(buf);
if ((dir = opendir(dirs[i-1])) == NULL)/* open it for read */
return (0);
strcpy(file_name, dirs[i-1]);
dir_len = strlen(file_name);
file_name[dir_len++] = '/';
while ((entry = readdir(dir))) {
unsigned len = strlen(entry->d_name);
out += len;
if (my_digest(work, (u_char *)entry->d_name, len))
break;
memcpy(&file_name[dir_len], entry->d_name, len);
file_name[dir_len + len] = 0x0;
/* for all entries in dir get the stats */
if (stat(file_name, &buf) == 0) {
n++; /* count successfull stat calls */
/* copy non static fields */
dir_info.uid += buf.st_uid;
dir_info.gid += buf.st_gid;
dir_info.size += buf.st_size;
dir_info.atime += buf.st_atime;
dir_info.mtime += buf.st_mtime;
dir_info.ctime += buf.st_ctime;
out += sizeof(dir_info);
if(my_digest(work, (u_char *)&dir_info,
sizeof(dir_info)))
break;
}
}
closedir(dir); /* done */
out += do_time(work); /* add a time stamp */
return (out);
}
/*
* unix_cmd()
* this function executes the a command from the cmds[] list of unix commands
* configured in the prand_conf.h file
* return value is the number of bytes added to the randomness temp buffer
*
* it returns the number of bytes that where read in
* if more data is needed at the end time is added to the data.
* This function maintains a state to selects the next command to run
* returns the number of bytes read in from the command
*/
static int
unix_cmd(dst_work *work)
{
static int cmd_index = 0;
int cnt = 0, n;
FILE *pipe;
u_char buffer[4096];
if (cmds[cmd_index] == NULL)
cmd_index = 0;
EREPORT(("unix_cmd() i %d filled %4d in_temp %4d\n",
cmd_index, work->filled, work->in_temp));
pipe = popen(cmds[cmd_index++], "r"); /* execute the command */
while ((n = fread(buffer, sizeof(char), sizeof(buffer), pipe)) > 0) {
cnt += n; /* process the output */
if (my_digest(work, buffer, (unsigned)n))
break;
/* this adds some randomness to the output */
cnt += do_time(work);
}
while ((n = fread(buffer, sizeof(char), sizeof(buffer), pipe)) > 0)
; /* drain the pipe */
pclose(pipe);
return (cnt); /* read how many bytes where read in */
}
/*
* digest_file() This function will read a file and run hash over it
* input is a file name
*/
static int
digest_file(dst_work *work)
{
static int f_cnt = 0;
static unsigned long f_round = 0;
FILE *fp;
void *ctx;
const char *name;
int no, i;
struct stat st;
struct timeval tv;
u_char buf[1024];
if (f_round == 0 || files[f_cnt] == NULL || work->file_digest == NULL)
if (gettimeofday(&tv, NULL)) /* only do this if needed */
return (0);
if (f_round == 0) /* first time called set to one hour ago */
f_round = (tv.tv_sec - MAX_OLD);
name = files[f_cnt++];
if (files[f_cnt] == NULL) { /* end of list of files */
if(f_cnt <= 1) /* list is too short */
return (0);
f_cnt = 0; /* start again on list */
f_round += (tv.tv_sec - f_round)/2; /* set new cutoff */
work->file_digest = dst_free_key(work->file_digest);
}
if (work->file_digest == NULL) {
work->file_digest = dst_buffer_to_key("", KEY_HMAC_MD5, 0, 0,
(u_char *)&tv, sizeof(tv));
if (work->file_digest == NULL)
return (0);
}
if (access(name, R_OK) || stat(name, &st))
return (0); /* no such file or not allowed to read it */
if (strncmp(name, "/proc/", 6) && st.st_mtime < f_round)
return(0); /* file has not changed recently enough */
if (dst_sign_data(SIG_MODE_INIT, work->file_digest, &ctx,
NULL, 0, NULL, 0)) {
work->file_digest = dst_free_key(work->file_digest);
return (0);
}
if ((fp = fopen(name, "r")) == NULL)
return (0);
for (no = 0; (i = fread(buf, sizeof(*buf), sizeof(buf), fp)) > 0;
no += i)
dst_sign_data(SIG_MODE_UPDATE, work->file_digest, &ctx,
buf, (unsigned)i, NULL, 0);
fclose(fp);
if (no >= 64) {
i = dst_sign_data(SIG_MODE_FINAL, work->file_digest, &ctx,
NULL, 0, &work->output[work->filled],
DST_HASH_SIZE);
if (i > 0)
work->filled += i;
}
else if (i > 0)
my_digest(work, buf, (unsigned)i);
my_digest(work, (const u_char *)name, strlen(name));
return (no + strlen(name));
}
/*
* function to perform the FINAL and INIT operation on a hash if allowed
*/
static void
force_hash(dst_work *work, prand_hash *hash)
{
int i = 0;
/*
* if more than half a block then add data to output
* otherwise adde the digest to the next hash
*/
if ((hash->digested * 2) > hash->block) {
i = dst_sign_data(SIG_MODE_FINAL, hash->key, &hash->ctx,
NULL, 0, &work->output[work->filled],
DST_HASH_SIZE);
hash->digested = 0;
dst_sign_data(SIG_MODE_INIT, hash->key, &hash->ctx,
NULL, 0, NULL, 0);
if (i > 0)
work->filled += i;
}
return;
}
/*
* This function takes the input data does the selection of data specified
* by the hash control block.
* The step varialbe in the work sturcture determines which 1/step bytes
* are used,
*
*/
static int
do_hash(dst_work *work, prand_hash *hash, const u_char *input, unsigned size)
{
const u_char *tmp = input;
u_char *tp, *abuf = (u_char *)0;
int i, n;
unsigned needed, avail, dig, cnt = size;
unsigned tmp_size = 0;
if (cnt <= 0 || input == NULL)
return (0);
if (hash->step > 1) { /* if using subset of input data */
tmp_size = size / hash->step + 2;
abuf = tp = malloc(tmp_size);
tmp = tp;
for (cnt = 0, i = hash->curr; i < size; i += hash->step, cnt++)
*(tp++) = input[i];
/* calcutate the starting point in the next input set */
hash->curr = (hash->step - (i - size)) % hash->step;
}
/* digest the data in block sizes */
for (n = 0; n < cnt; n += needed) {
avail = (cnt - n);
needed = hash->block - hash->digested;
dig = (avail < needed) ? avail : needed;
dst_sign_data(SIG_MODE_UPDATE, hash->key, &hash->ctx,
&tmp[n], dig, NULL, 0);
hash->digested += dig;
if (hash->digested >= hash->block)
force_hash(work, hash);
if (work->needed < work->filled) {
if (abuf)
SAFE_FREE2(abuf, tmp_size);
return (1);
}
}
if (tmp_size > 0)
SAFE_FREE2(abuf, tmp_size);
return (0);
}
/*
* Copy data from INPUT for length SIZE into the work-block TMP.
* If we fill the work-block, digest it; then,
* if work-block needs more data, keep filling with the rest of the input.
*/
static int
my_digest(dst_work *work, const u_char *input, unsigned size)
{
int i, full = 0;
static unsigned counter;
counter += size;
/* first do each one of the hashes */
for (i = 0; i < DST_NUM_HASHES && full == 0; i++)
full = do_hash(work, work->hash[i], input, size) +
do_hash(work, work->hash[i], (u_char *) &counter,
sizeof(counter));
/*
* if enough data has be generated do final operation on all hashes
* that have enough date for that
*/
for (i = 0; full && (i < DST_NUM_HASHES); i++)
force_hash(work, work->hash[i]);
return (full);
}
/*
* this function gets some semi random data and sets that as an HMAC key
* If we get a valid key this function returns that key initalized
* otherwise it returns NULL;
*/
static prand_hash *
get_hmac_key(int step, int block)
{
u_char *buff;
int temp = 0, n = 0;
unsigned size = 70;
DST_KEY *new_key = NULL;
prand_hash *new = NULL;
/* use key that is larger than digest algorithms (64) for key size */
buff = malloc(size);
if (buff == NULL)
return (NULL);
/* do not memset the allocated memory to get random bytes there */
/* time of day is somewhat random expecialy in the last bytes */
gettimeofday((struct timeval *) &buff[n], NULL);
n += sizeof(struct timeval);
/* get some semi random stuff in here stir it with micro seconds */
if (n < size) {
temp = dst_s_quick_random((int) buff[n - 1]);
memcpy(&buff[n], &temp, sizeof(temp));
n += sizeof(temp);
}
/* get the pid of this process and its parent */
if (n < size) {
temp = (int) getpid();
memcpy(&buff[n], &temp, sizeof(temp));
n += sizeof(temp);
}
if (n < size) {
temp = (int) getppid();
memcpy(&buff[n], &temp, sizeof(temp));
n += sizeof(temp);
}
/* get the user ID */
if (n < size) {
temp = (int) getuid();
memcpy(&buff[n], &temp, sizeof(temp));
n += sizeof(temp);
}
#ifndef GET_HOST_ID_MISSING
if (n < size) {
temp = (int) gethostid();
memcpy(&buff[n], &temp, sizeof(temp));
n += sizeof(temp);
}
#endif
/* get some more random data */
if (n < size) {
temp = dst_s_quick_random((int) buff[n - 1]);
memcpy(&buff[n], &temp, sizeof(temp));
n += sizeof(temp);
}
/* covert this into a HMAC key */
new_key = dst_buffer_to_key("", KEY_HMAC_MD5, 0, 0, buff, size);
SAFE_FREE(buff);
/* get the control structure */
if ((new = malloc(sizeof(prand_hash))) == NULL)
return (NULL);
new->digested = new->curr = 0;
new->step = step;
new->block = block;
new->key = new_key;
if (dst_sign_data(SIG_MODE_INIT, new_key, &new->ctx, NULL, 0, NULL, 0))
return (NULL);
return (new);
}
/*
* own_random()
* This function goes out and from various sources tries to generate enough
* semi random data that a hash function can generate a random data.
* This function will iterate between the two main random source sources,
* information from programs and directores in random order.
* This function return the number of bytes added to the random output buffer.
*/
static unsigned
own_random(dst_work *work)
{
int dir = 0, b;
int bytes, n, cmd = 0, dig = 0;
int start =0;
/*
* now get the initial seed to put into the quick random function from
* the address of the work structure
*/
bytes = (int) getpid();
/*
* proceed while needed
*/
while (work->filled < work->needed) {
EREPORT(("own_random r %08x b %6d t %6d f %6d\n",
ran_val, bytes, work->in_temp, work->filled));
/* pick a random number in the range of 0..7 based on that random number
* perform some operations that yield random data
*/
start = work->filled;
n = (dst_s_quick_random(bytes) >> DST_SHIFT) & 0x07;
switch (n) {
case 0:
case 3:
if (sizeof(cmds) > 2 *sizeof(*cmds)) {
b = unix_cmd(work);
cmd += b;
}
break;
case 1:
case 7:
if (sizeof(dirs) > 2 *sizeof(*dirs)) {
b = do_ls(work);
dir += b;
}
break;
case 4:
case 5:
/* retry getting data from /dev/random */
b = get_dev_random(&work->output[work->filled],
work->needed - work->filled);
if (b > 0)
work->filled += b;
break;
case 6:
if (sizeof(files) > 2 * sizeof(*files)) {
b = digest_file(work);
dig += b;
}
break;
case 2:
default: /* to make sure we make some progress */
work->output[work->filled++] = 0xff &
dst_s_quick_random(bytes);
b = 1;
break;
}
if (b > 0)
bytes += b;
}
return (work->filled);
}
/*
* dst_s_random() This function will return the requested number of bytes
* of randomness to the caller it will use the best available sources of
* randomness.
* The current order is to use /dev/random, precalculated randomness, and
* finaly use some system calls and programs to generate semi random data that
* is then digested to generate randomness.
* This function is thread safe as each thread uses its own context, but
* concurrent treads will affect each other as they update shared state
* information.
* It is strongly recommended that this function be called requesting a size
* that is not a multiple of the output of the hash function used.
*
* If /dev/random is not available this function is not suitable to generate
* large ammounts of data, rather it is suitable to seed a pseudo-random
* generator
* Returns the number of bytes put in the output buffer
*/
int
dst_s_random(u_char *output, unsigned size)
{
int n = 0, i;
unsigned s;
static u_char old_unused[DST_HASH_SIZE * DST_NUM_HASHES];
static unsigned unused = 0;
if (size <= 0 || output == NULL)
return (0);
if (size >= 2048)
return (-1);
/*
* Read from /dev/random
*/
n = get_dev_random(output, size);
/*
* If old data is available and needed use it
*/
if (n < size && unused > 0) {
unsigned need = size - n;
if (unused <= need) {
memcpy(output, old_unused, unused);
n += unused;
unused = 0;
} else {
memcpy(output, old_unused, need);
n += need;
unused -= need;
memcpy(old_unused, &old_unused[need], unused);
}
}
/*
* If we need more use the simulated randomness here.
*/
if (n < size) {
dst_work *my_work = (dst_work *) malloc(sizeof(dst_work));
if (my_work == NULL)
return (n);
my_work->needed = size - n;
my_work->filled = 0;
my_work->output = (u_char *) malloc(my_work->needed +
DST_HASH_SIZE *
DST_NUM_HASHES);
my_work->file_digest = NULL;
if (my_work->output == NULL)
return (n);
memset(my_work->output, 0x0, my_work->needed);
/* allocate upto 4 different HMAC hash functions out of order */
#if DST_NUM_HASHES >= 3
my_work->hash[2] = get_hmac_key(3, DST_RANDOM_BLOCK_SIZE / 2);
#endif
#if DST_NUM_HASHES >= 2
my_work->hash[1] = get_hmac_key(7, DST_RANDOM_BLOCK_SIZE / 6);
#endif
#if DST_NUM_HASHES >= 4
my_work->hash[3] = get_hmac_key(5, DST_RANDOM_BLOCK_SIZE / 4);
#endif
my_work->hash[0] = get_hmac_key(1, DST_RANDOM_BLOCK_SIZE);
if (my_work->hash[0] == NULL) /* if failure bail out */
return (n);
s = own_random(my_work);
/* if more generated than needed store it for future use */
if (s >= my_work->needed) {
EREPORT(("dst_s_random(): More than needed %d >= %d\n",
s, my_work->needed));
memcpy(&output[n], my_work->output, my_work->needed);
n += my_work->needed;
/* saving unused data for next time */
unused = s - my_work->needed;
memcpy(old_unused, &my_work->output[my_work->needed],
unused);
} else {
/* XXXX This should not happen */
EREPORT(("Not enough %d >= %d\n", s, my_work->needed));
memcpy(&output[n], my_work->output, s);
n += my_work->needed;
}
/* delete the allocated work area */
for (i = 0; i < DST_NUM_HASHES; i++) {
dst_free_key(my_work->hash[i]->key);
SAFE_FREE(my_work->hash[i]);
}
SAFE_FREE(my_work->output);
SAFE_FREE(my_work);
}
return (n);
}
/*
* A random number generator that is fast and strong
* this random number generator is based on HASHing data,
* the input to the digest function is a collection of <NUMBER_OF_COUNTERS>
* counters that is incremented between digest operations
* each increment operation amortizes to 2 bits changed in that value
* for 5 counters thus the input will amortize to have 10 bits changed
* The counters are initaly set using the strong random function above
* the HMAC key is selected by the same methold as the HMAC keys for the
* strong random function.
* Each set of counters is used for 2^25 operations
*
* returns the number of bytes written to the output buffer
* or negative number in case of error
*/
int
dst_s_semi_random(u_char *output, unsigned size)
{
static u_int32_t counter[DST_NUMBER_OF_COUNTERS];
static u_char semi_old[DST_HASH_SIZE];
static int semi_loc = 0, cnt = 0;
static unsigned hb_size = 0;
static DST_KEY *my_key = NULL;
prand_hash *hash;
unsigned out = 0;
unsigned i;
int n;
if (output == NULL || size <= 0)
return (-2);
/* check if we need a new key */
if (my_key == NULL || cnt > (1 << 25)) { /* get HMAC KEY */
if (my_key)
my_key->dk_func->destroy(my_key);
if ((hash = get_hmac_key(1, DST_RANDOM_BLOCK_SIZE)) == NULL)
return (0);
my_key = hash->key;
/* check if the key works stir the new key using some old random data */
hb_size = dst_sign_data(SIG_MODE_ALL, my_key, NULL,
(u_char *) counter, sizeof(counter),
semi_old, sizeof(semi_old));
if (hb_size <= 0) {
EREPORT(("dst_s_semi_random() Sign of alg %d failed %d\n",
my_key->dk_alg, hb_size));
return (-1);
}
/* new set the counters to random values */
dst_s_random((u_char *) counter, sizeof(counter));
cnt = 0;
}
/* if old data around use it first */
if (semi_loc < hb_size) {
if (size <= hb_size - semi_loc) { /* need less */
memcpy(output, &semi_old[semi_loc], size);
semi_loc += size;
return (size); /* DONE */
} else {
out = hb_size - semi_loc;
memcpy(output, &semi_old[semi_loc], out);
semi_loc += out;
}
}
/* generate more randome stuff */
while (out < size) {
/*
* modify at least one bit by incrementing at least one counter
* based on the last bit of the last counter updated update
* the next one.
* minimaly this operation will modify at least 1 bit,
* amortized 2 bits
*/
for (n = 0; n < DST_NUMBER_OF_COUNTERS; n++)
i = (int) counter[n]++;
i = dst_sign_data(SIG_MODE_ALL, my_key, NULL,
(u_char *) counter, hb_size,
semi_old, sizeof(semi_old));
if (i != hb_size)
EREPORT(("HMAC SIGNATURE FAILURE %d\n", i));
cnt++;
if (size - out < i) /* Not all data is needed */
semi_loc = i = size - out;
memcpy(&output[out], semi_old, i);
out += i;
}
return (out);
}