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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 3 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, see <http://www.gnu.org/licenses/>.
*/
#include "includes.h"
static struct arcfour_state smb_arc4_state;
static uint32 counter;
static bool done_reseed = False;
static void (*reseed_callback)(int *newseed);
/****************************************************************
Copy any user given reseed data.
*****************************************************************/
void set_rand_reseed_callback(void (*fn)(int *))
{
reseed_callback = fn;
set_need_random_reseed();
}
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;
}
}
/****************************************************************
Get a 16 byte hash from the contents of a file.
Note that the hash is not initialised.
*****************************************************************/
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;
fd = sys_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];
DATA_BLOB seed_blob = { seed_inbuf, 40 };
uint32 v1, v2; struct timeval tval; pid_t mypid;
struct passwd *pw;
int reseed_data = 0;
if (use_fd) {
if (fd != -1)
return fd;
fd = sys_open( "/dev/urandom", O_RDONLY,0);
if(fd >= 0)
return fd;
}
/* Add in some secret file contents */
do_filehash("/etc/shadow", &seed_inbuf[0]);
do_filehash(lp_smb_passwd_file(), &seed_inbuf[16]);
/*
* Add in the root encrypted password.
* On any system where security is taken
* seriously this will be secret.
*/
pw = getpwnam_alloc(NULL, "root");
if (pw && pw->pw_passwd) {
size_t i;
unsigned char md4_tmp[16];
mdfour(md4_tmp, (unsigned char *)pw->pw_passwd, strlen(pw->pw_passwd));
for (i=0;i<16;i++)
seed_inbuf[8+i] ^= md4_tmp[i];
TALLOC_FREE(pw);
}
/*
* Add the counter, time of day, and pid.
*/
GetTimeOfDay(&tval);
mypid = sys_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)];
}
arcfour_init(&smb_arc4_state, &seed_blob);
return -1;
}
/*******************************************************************
Interface to the (hopefully) good crypto random number generator.
********************************************************************/
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;
arcfour_crypt_sbox(&smb_arc4_state, 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;
}
}
/*******************************************************************
Use the random number generator to generate a random string.
********************************************************************/
static char c_list[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#.,";
char *generate_random_str(TALLOC_CTX *mem_ctx, size_t len)
{
unsigned char *retstr = talloc_zero_array(mem_ctx, unsigned char, len);
size_t i;
generate_random_buffer( retstr, len);
for (i = 0; i < len; i++)
retstr[i] = c_list[ retstr[i] % (sizeof(c_list)-1) ];
retstr[i] = '\0';
return (char *)retstr;
}
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