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/*
Unix SMB/Netbios implementation.
Version 1.9.
Functions to create reasonable random numbers for crypto use.
Copyright (C) Jeremy Allison 1998
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"
extern int DEBUGLEVEL;
static uint32 counter = 0;
/****************************************************************
get a 16 byte hash from the contents of a file
Note that the hash is not initialised.
*****************************************************************/
static void do_filehash(char *fname, unsigned char *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++)
hash[n] ^= tmp_md4[n];
}
close(fd);
}
/****************************************************************
Try and get a seed by looking at the atimes of files in a given
directory. XOR them into the buf array.
*****************************************************************/
static void do_dirrand(char *name, unsigned char *buf, int buf_len)
{
DIR *dp = opendir(name);
pstring fullname;
int len_left;
int fullname_len;
char *pos;
pstrcpy(fullname, name);
fullname_len = strlen(fullname);
if(fullname_len + 2 > sizeof(pstring))
return;
if(fullname[fullname_len] != '/') {
fullname[fullname_len] = '/';
fullname[fullname_len+1] = '\0';
fullname_len = strlen(fullname);
}
len_left = sizeof(pstring) - fullname_len - 1;
pos = &fullname[fullname_len];
if(dp != NULL) {
char *p;
while ((p = readdirname(dp))) {
SMB_STRUCT_STAT st;
if(strlen(p) <= len_left)
pstrcpy(pos, p);
if(sys_stat(fullname,&st) == 0) {
SIVAL(buf, ((counter * 4)%(buf_len-4)),
IVAL(buf,((counter * 4)%(buf_len-4))) ^ st.st_atime);
counter++;
DEBUG(10,("do_dirrand: value from file %s.\n", fullname));
}
}
closedir(dp);
}
}
/**************************************************************
Try and get a good random number seed. Try a number of
different factors. Firstly, try /dev/urandom and try and
read from this. If this fails iterate through /tmp and
/dev and XOR all the file timestamps. Next add in
a hash of the contents of /etc/shadow and the smb passwd
file and a combination of pid and time of day (yes I know this
sucks :-). Finally md4 the result.
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.
The result goes in a 16 byte buffer passed from the caller
**************************************************************/
static uint32 do_reseed(unsigned char *md4_outbuf)
{
unsigned char md4_inbuf[40];
BOOL got_random = False;
uint32 v1, v2, ret;
int fd;
struct timeval tval;
pid_t mypid;
struct passwd *pw;
memset(md4_inbuf, '\0', sizeof(md4_inbuf));
fd = sys_open( "/dev/urandom", O_RDONLY,0);
if(fd >= 0) {
/*
* We can use /dev/urandom !
*/
if(read(fd, md4_inbuf, 40) == 40) {
got_random = True;
DEBUG(10,("do_reseed: got 40 bytes from /dev/urandom.\n"));
}
close(fd);
}
if(!got_random) {
/*
* /dev/urandom failed - try /tmp and /dev for timestamps.
*/
do_dirrand("/tmp", md4_inbuf, sizeof(md4_inbuf));
do_dirrand("/dev", md4_inbuf, sizeof(md4_inbuf));
}
/* possibly add in some secret file contents */
do_filehash("/etc/shadow", &md4_inbuf[0]);
do_filehash(lp_smb_passwd_file(), &md4_inbuf[16]);
/* add in the root encrypted password. On any system where security is taken
seriously this will be secret */
pw = getpwnam("root");
if (pw && pw->pw_passwd) {
int i;
unsigned char md4_tmp[16];
mdfour(md4_tmp, (unsigned char *)pw->pw_passwd, strlen(pw->pw_passwd));
for (i=0;i<16;i++)
md4_inbuf[8+i] ^= md4_tmp[i];
}
/*
* Finally 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(md4_inbuf, 32, v1 ^ IVAL(md4_inbuf, 32));
SIVAL(md4_inbuf, 36, v2 ^ IVAL(md4_inbuf, 36));
mdfour(md4_outbuf, md4_inbuf, sizeof(md4_inbuf));
/*
* Return a 32 bit int created from XORing the
* 16 bit return buffer.
*/
ret = IVAL(md4_outbuf, 0);
ret ^= IVAL(md4_outbuf, 4);
ret ^= IVAL(md4_outbuf, 8);
return (ret ^ IVAL(md4_outbuf, 12));
}
/*******************************************************************
Interface to the (hopefully) good crypto random number generator.
********************************************************************/
void generate_random_buffer( unsigned char *out, int len, BOOL re_seed)
{
static BOOL done_reseed = False;
static unsigned char md4_buf[16];
unsigned char tmp_buf[16];
unsigned char *p;
if(!done_reseed || re_seed) {
sys_srandom(do_reseed(md4_buf));
done_reseed = True;
}
/*
* Generate random numbers in chunks of 64 bytes,
* then md4 them & copy to the output buffer.
* Added XOR with output from random, seeded
* by the original md4_buf. This is to stop the
* output from this function being the previous
* md4_buf md4'ed. The output from this function
* is often output onto the wire, and so it should
* not be possible to guess the next output from
* this function based on the previous output.
* XORing in the output from random(), seeded by
* the original md4 hash should stop this. JRA.
*/
p = out;
while(len > 0) {
int i;
int copy_len = len > 16 ? 16 : len;
mdfour(tmp_buf, md4_buf, sizeof(md4_buf));
memcpy(md4_buf, tmp_buf, sizeof(md4_buf));
/* XOR in output from random(). */
for(i = 0; i < 4; i++)
SIVAL(tmp_buf, i*4, (IVAL(tmp_buf, i*4) ^ (uint32)sys_random()));
memcpy(p, tmp_buf, copy_len);
p += copy_len;
len -= copy_len;
}
}
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