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samba-mirror/source4/lib/util/genrand.c

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/*
Unix SMB/CIFS implementation.
Functions to create reasonable random numbers for crypto use.
Copyright (C) Jeremy Allison 2001
This program 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.
This program 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "includes.h"
#include "system/filesys.h"
#include "lib/crypto/crypto.h"
#include "system/locale.h"
/**
* @file
* @brief Random number generation
*/
static unsigned char hash[258];
static uint32_t counter;
static BOOL done_reseed = False;
static void (*reseed_callback)(int *newseed);
/**
Copy any user given reseed data.
**/
_PUBLIC_ void set_rand_reseed_callback(void (*fn)(int *))
{
reseed_callback = fn;
set_need_random_reseed();
}
/**
* Tell the random number generator it needs to reseed.
*/
_PUBLIC_ void set_need_random_reseed(void)
{
done_reseed = False;
}
static void get_rand_reseed_data(int *reseed_data)
{
if (reseed_callback) {
reseed_callback(reseed_data);
} else {
*reseed_data = 0;
}
}
/****************************************************************
Setup the seed.
*****************************************************************/
static void seed_random_stream(unsigned char *seedval, size_t seedlen)
{
unsigned char j = 0;
size_t ind;
for (ind = 0; ind < 256; ind++)
hash[ind] = (unsigned char)ind;
for( ind = 0; ind < 256; ind++) {
unsigned char tc;
j += (hash[ind] + seedval[ind%seedlen]);
tc = hash[ind];
hash[ind] = hash[j];
hash[j] = tc;
}
hash[256] = 0;
hash[257] = 0;
}
/****************************************************************
Get datasize bytes worth of random data.
*****************************************************************/
static void get_random_stream(unsigned char *data, size_t datasize)
{
unsigned char index_i = hash[256];
unsigned char index_j = hash[257];
size_t ind;
for( ind = 0; ind < datasize; ind++) {
unsigned char tc;
unsigned char t;
index_i++;
index_j += hash[index_i];
tc = hash[index_i];
hash[index_i] = hash[index_j];
hash[index_j] = tc;
t = hash[index_i] + hash[index_j];
data[ind] = hash[t];
}
hash[256] = index_i;
hash[257] = index_j;
}
/****************************************************************
Get a 16 byte hash from the contents of a file.
Note that the hash is initialised, because the extra entropy is not
worth the valgrind pain.
*****************************************************************/
static void do_filehash(const char *fname, unsigned char *the_hash)
{
unsigned char buf[1011]; /* deliberate weird size */
unsigned char tmp_md4[16];
int fd, n;
ZERO_STRUCT(tmp_md4);
fd = open(fname,O_RDONLY,0);
if (fd == -1)
return;
while ((n = read(fd, (char *)buf, sizeof(buf))) > 0) {
mdfour(tmp_md4, buf, n);
for (n=0;n<16;n++)
the_hash[n] ^= tmp_md4[n];
}
close(fd);
}
/**************************************************************
Try and get a good random number seed. Try a number of
different factors. Firstly, try /dev/urandom - use if exists.
We use /dev/urandom as a read of /dev/random can block if
the entropy pool dries up. This leads clients to timeout
or be very slow on connect.
If we can't use /dev/urandom then seed the stream random generator
above...
**************************************************************/
static int do_reseed(BOOL use_fd, int fd)
{
unsigned char seed_inbuf[40];
uint32_t v1, v2; struct timeval tval; pid_t mypid;
int reseed_data = 0;
if (use_fd) {
if (fd != -1)
return fd;
fd = open( "/dev/urandom", O_RDONLY,0);
if(fd >= 0)
return fd;
}
/* Add in some secret file contents */
do_filehash("/etc/shadow", &seed_inbuf[0]);
/*
* Add the counter, time of day, and pid.
*/
GetTimeOfDay(&tval);
mypid = getpid();
v1 = (counter++) + mypid + tval.tv_sec;
v2 = (counter++) * mypid + tval.tv_usec;
SIVAL(seed_inbuf, 32, v1 ^ IVAL(seed_inbuf, 32));
SIVAL(seed_inbuf, 36, v2 ^ IVAL(seed_inbuf, 36));
/*
* Add any user-given reseed data.
*/
get_rand_reseed_data(&reseed_data);
if (reseed_data) {
size_t i;
for (i = 0; i < sizeof(seed_inbuf); i++)
seed_inbuf[i] ^= ((char *)(&reseed_data))[i % sizeof(reseed_data)];
}
seed_random_stream(seed_inbuf, sizeof(seed_inbuf));
return -1;
}
/**
Interface to the (hopefully) good crypto random number generator.
**/
_PUBLIC_ void generate_random_buffer(uint8_t *out, int len)
{
static int urand_fd = -1;
unsigned char md4_buf[64];
unsigned char tmp_buf[16];
unsigned char *p;
if(!done_reseed) {
urand_fd = do_reseed(True, urand_fd);
done_reseed = True;
}
if (urand_fd != -1 && len > 0) {
if (read(urand_fd, out, len) == len)
return; /* len bytes of random data read from urandom. */
/* Read of urand error, drop back to non urand method. */
close(urand_fd);
urand_fd = -1;
do_reseed(False, -1);
done_reseed = True;
}
/*
* Generate random numbers in chunks of 64 bytes,
* then md4 them & copy to the output buffer.
* This way the raw state of the stream is never externally
* seen.
*/
p = out;
while(len > 0) {
int copy_len = len > 16 ? 16 : len;
get_random_stream(md4_buf, sizeof(md4_buf));
mdfour(tmp_buf, md4_buf, sizeof(md4_buf));
memcpy(p, tmp_buf, copy_len);
p += copy_len;
len -= copy_len;
}
}
/**
generate a single random uint32_t
**/
_PUBLIC_ uint32_t generate_random(void)
{
uint8_t v[4];
generate_random_buffer(v, 4);
return IVAL(v, 0);
}
/**
very basic password quality checker
**/
_PUBLIC_ BOOL check_password_quality(const char *s)
{
int has_digit=0, has_capital=0, has_lower=0;
while (*s) {
if (isdigit((unsigned char)*s)) {
has_digit++;
} else if (isupper((unsigned char)*s)) {
has_capital++;
} else if (islower((unsigned char)*s)) {
has_lower++;
}
s++;
}
return has_digit && has_lower && has_capital;
}
/**
Use the random number generator to generate a random string.
**/
_PUBLIC_ char *generate_random_str_list(TALLOC_CTX *mem_ctx, size_t len, const char *list)
{
size_t i;
size_t list_len = strlen(list);
char *retstr = talloc_array(mem_ctx, char, len + 1);
if (!retstr) return NULL;
generate_random_buffer((uint8_t *)retstr, len);
for (i = 0; i < len; i++) {
retstr[i] = list[retstr[i] % list_len];
}
retstr[i] = '\0';
return retstr;
}
/**
* Generate a random text string consisting of the specified length.
* The returned string will be allocated.
*
* Characters used are: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#.,
*/
_PUBLIC_ char *generate_random_str(TALLOC_CTX *mem_ctx, size_t len)
{
char *retstr;
const char *c_list = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#.,";
again:
retstr = generate_random_str_list(mem_ctx, len, c_list);
if (!retstr) return NULL;
/* we need to make sure the random string passes basic quality tests
or it might be rejected by windows as a password */
if (len >= 7 && !check_password_quality(retstr)) {
talloc_free(retstr);
goto again;
}
return retstr;
}