/* 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; } }