mirror of https://github.com/MidnightCommander/mc
230 lines
6.5 KiB
C
230 lines
6.5 KiB
C
/*
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Unix SMB/Netbios implementation.
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Version 1.9.
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Functions to create reasonable random numbers for crypto use.
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Copyright (C) Jeremy Allison 1998
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include "includes.h"
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extern int DEBUGLEVEL;
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static uint32 counter = 0;
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/****************************************************************
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get a 16 byte hash from the contents of a file
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Note that the hash is not initialised.
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*****************************************************************/
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static void do_filehash(char *fname, unsigned char *hash)
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{
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unsigned char buf[1011]; /* deliberate weird size */
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unsigned char tmp_md4[16];
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int fd, n;
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fd = sys_open(fname,O_RDONLY,0);
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if (fd == -1) return;
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while ((n = read(fd, (char *)buf, sizeof(buf))) > 0) {
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mdfour(tmp_md4, buf, n);
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for (n=0;n<16;n++)
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hash[n] ^= tmp_md4[n];
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}
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close(fd);
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}
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/****************************************************************
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Try and get a seed by looking at the atimes of files in a given
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directory. XOR them into the buf array.
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*****************************************************************/
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static void do_dirrand(char *name, unsigned char *buf, int buf_len)
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{
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DIR *dp = opendir(name);
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pstring fullname;
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int len_left;
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int fullname_len;
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char *pos;
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pstrcpy(fullname, name);
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fullname_len = strlen(fullname);
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if(fullname_len + 2 > sizeof(pstring))
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return;
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if(fullname[fullname_len] != '/') {
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fullname[fullname_len] = '/';
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fullname[fullname_len+1] = '\0';
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fullname_len = strlen(fullname);
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}
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len_left = sizeof(pstring) - fullname_len - 1;
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pos = &fullname[fullname_len];
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if(dp != NULL) {
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char *p;
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while ((p = readdirname(dp))) {
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SMB_STRUCT_STAT st;
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if(strlen(p) <= len_left)
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pstrcpy(pos, p);
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if(sys_stat(fullname,&st) == 0) {
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SIVAL(buf, ((counter * 4)%(buf_len-4)),
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IVAL(buf,((counter * 4)%(buf_len-4))) ^ st.st_atime);
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counter++;
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DEBUG(10,("do_dirrand: value from file %s.\n", fullname));
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}
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}
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closedir(dp);
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}
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}
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/**************************************************************
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Try and get a good random number seed. Try a number of
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different factors. Firstly, try /dev/urandom and try and
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read from this. If this fails iterate through /tmp and
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/dev and XOR all the file timestamps. Next add in
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a hash of the contents of /etc/shadow and the smb passwd
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file and a combination of pid and time of day (yes I know this
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sucks :-). Finally md4 the result.
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We use /dev/urandom as a read of /dev/random can block if
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the entropy pool dries up. This leads clients to timeout
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or be very slow on connect.
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The result goes in a 16 byte buffer passed from the caller
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**************************************************************/
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static uint32 do_reseed(unsigned char *md4_outbuf)
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{
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unsigned char md4_inbuf[40];
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BOOL got_random = False;
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uint32 v1, v2, ret;
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int fd;
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struct timeval tval;
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pid_t mypid;
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struct passwd *pw;
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memset(md4_inbuf, '\0', sizeof(md4_inbuf));
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fd = sys_open( "/dev/urandom", O_RDONLY,0);
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if(fd >= 0) {
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/*
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* We can use /dev/urandom !
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*/
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if(read(fd, md4_inbuf, 40) == 40) {
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got_random = True;
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DEBUG(10,("do_reseed: got 40 bytes from /dev/urandom.\n"));
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}
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close(fd);
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}
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if(!got_random) {
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/*
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* /dev/urandom failed - try /dev for timestamps.
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*/
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do_dirrand("/dev", md4_inbuf, sizeof(md4_inbuf));
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}
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/* possibly add in some secret file contents */
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do_filehash("/etc/shadow", &md4_inbuf[0]);
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do_filehash(lp_smb_passwd_file(), &md4_inbuf[16]);
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/* add in the root encrypted password. On any system where security is taken
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seriously this will be secret */
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pw = getpwnam("root");
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if (pw && pw->pw_passwd) {
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int i;
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unsigned char md4_tmp[16];
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mdfour(md4_tmp, (unsigned char *)pw->pw_passwd, strlen(pw->pw_passwd));
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for (i=0;i<16;i++)
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md4_inbuf[8+i] ^= md4_tmp[i];
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}
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/*
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* Finally add the counter, time of day, and pid.
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*/
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GetTimeOfDay(&tval);
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mypid = getpid();
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v1 = (counter++) + mypid + tval.tv_sec;
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v2 = (counter++) * mypid + tval.tv_usec;
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SIVAL(md4_inbuf, 32, v1 ^ IVAL(md4_inbuf, 32));
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SIVAL(md4_inbuf, 36, v2 ^ IVAL(md4_inbuf, 36));
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mdfour(md4_outbuf, md4_inbuf, sizeof(md4_inbuf));
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/*
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* Return a 32 bit int created from XORing the
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* 16 bit return buffer.
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*/
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ret = IVAL(md4_outbuf, 0);
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ret ^= IVAL(md4_outbuf, 4);
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ret ^= IVAL(md4_outbuf, 8);
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return (ret ^ IVAL(md4_outbuf, 12));
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}
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/*******************************************************************
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Interface to the (hopefully) good crypto random number generator.
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********************************************************************/
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void generate_random_buffer( unsigned char *out, int len, BOOL re_seed)
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{
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static BOOL done_reseed = False;
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static unsigned char md4_buf[16];
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unsigned char tmp_buf[16];
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unsigned char *p;
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if(!done_reseed || re_seed) {
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sys_srandom(do_reseed(md4_buf));
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done_reseed = True;
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}
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/*
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* Generate random numbers in chunks of 64 bytes,
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* then md4 them & copy to the output buffer.
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* Added XOR with output from random, seeded
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* by the original md4_buf. This is to stop the
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* output from this function being the previous
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* md4_buf md4'ed. The output from this function
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* is often output onto the wire, and so it should
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* not be possible to guess the next output from
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* this function based on the previous output.
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* XORing in the output from random(), seeded by
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* the original md4 hash should stop this. JRA.
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*/
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p = out;
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while(len > 0) {
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int i;
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int copy_len = len > 16 ? 16 : len;
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mdfour(tmp_buf, md4_buf, sizeof(md4_buf));
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memcpy(md4_buf, tmp_buf, sizeof(md4_buf));
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/* XOR in output from random(). */
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for(i = 0; i < 4; i++)
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SIVAL(tmp_buf, i*4, (IVAL(tmp_buf, i*4) ^ (uint32)sys_random()));
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memcpy(p, tmp_buf, copy_len);
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p += copy_len;
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len -= copy_len;
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}
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}
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