+++ /dev/null
-/* -*-c-*-
- *
- * $Id$
- *
- * Acquisition of environmental noise (Unix-specific)
- *
- * (c) 1998 Straylight/Edgeware
- */
-
-/*----- Licensing notice --------------------------------------------------*
- *
- * This file is part of Catacomb.
- *
- * Catacomb is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Library General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or (at your option) any later version.
- *
- * Catacomb 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 Library General Public License for more details.
- *
- * You should have received a copy of the GNU Library General Public
- * License along with Catacomb; if not, write to the Free
- * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
- * MA 02111-1307, USA.
- */
-
-/*----- Header files ------------------------------------------------------*/
-
-#include "config.h"
-
-#include <setjmp.h>
-#include <stdio.h>
-#include <string.h>
-#include <signal.h>
-
-#include <sys/types.h>
-#include <sys/time.h>
-#include <sys/wait.h>
-
-#include <fcntl.h>
-#include <unistd.h>
-
-#ifdef HAVE_SETGROUPS
-# include <grp.h>
-#endif
-
-#include <mLib/bits.h>
-#include <mLib/tv.h>
-
-#include "noise.h"
-#include "paranoia.h"
-#include "rand.h"
-
-/*----- Magical numbers ---------------------------------------------------*/
-
-#define NOISE_KIDLIFE 100000 /* @noise_filter@ child lifetime */
-#define MILLION 1000000 /* One million */
-
-/*----- Noise source definition -------------------------------------------*/
-
-const rand_source noise_source = { noise_acquire, noise_timer };
-
-/*----- Static variables --------------------------------------------------*/
-
-/* --- Timer differences --- */
-
-static unsigned long noise_last; /* Last time recorded */
-static unsigned long noise_diff; /* Last first order difference */
-
-/* --- Setuid program handling --- */
-
-static uid_t noise_uid = NOISE_NOSETUID; /* Uid to set to spawn processes */
-static gid_t noise_gid = NOISE_NOSETGID; /* Gid to set to spawn processes */
-
-/*----- Main code ---------------------------------------------------------*/
-
-/* --- @bitcount@ --- *
- *
- * Arguments: @unsigned long x@ = a word containing bits
- *
- * Returns: The number of bits set in the word.
- */
-
-static int bitcount(unsigned long x)
-{
- char ctab[] = { 0, 1, 1, 2, 1, 2, 2, 3,
- 1, 2, 2, 3, 2, 3, 3, 4 };
- int count = 0;
- while (x) {
- count += ctab[x & 0xfu];
- x >>= 4;
- }
- return (count);
-}
-
-/* --- @timer@ --- *
- *
- * Arguments: @rand_pool *r@ = pointer to randomness pool
- * @struct timeval *tv@ = pointer to time block
- *
- * Returns: Nonzero if some randomness was contributed.
- *
- * Use: Low-level timer contributor.
- */
-
-static int timer(rand_pool *r, struct timeval *tv)
-{
- unsigned long x, d, dd;
- int de, dde;
- int ret;
-
- x = tv->tv_usec + MILLION * tv->tv_sec;
- d = x ^ noise_last;
- dd = d ^ noise_diff;
- noise_diff = d;
- de = bitcount(d);
- dde = bitcount(dd);
- rand_add(r, tv, sizeof(*tv), de <= dde ? de : dde);
- ret = (de || dde);
- BURN(tv); x = d = dd = de = dde = 0;
- return (ret);
-}
-
-/* --- @noise_timer@ --- *
- *
- * Arguments: @rand_pool *r@ = pointer to a randomness pool
- *
- * Returns: Nonzero if some randomness was contributed.
- *
- * Use: Contributes the current time to the randomness pool.
- * A guess at the number of useful bits contributed is made,
- * based on first and second order bit differences. This isn't
- * ever-so reliable, but it's better than nothing.
- */
-
-int noise_timer(rand_pool *r)
-{
- struct timeval tv;
- gettimeofday(&tv, 0);
- return (timer(r, &tv));
-}
-
-/* --- @noise_devrandom@ --- *
- *
- * Arguments: @rand_pool *r@ = pointer to a randomness pool
- *
- * Returns: Nonzero if some randomness was contributed.
- *
- * Use: Attempts to obtain some randomness from the system entropy
- * pool. All bits from the device are assumed to be good.
- */
-
-int noise_devrandom(rand_pool *r)
-{
- int fd;
- octet buf[RAND_POOLSZ];
- ssize_t len;
- int ret = 0;
-
- /* --- Be nice to other clients of the random device --- *
- *
- * Attempt to open the device nonblockingly. If that works, take up to
- * one bufferful and then close again. If there's no data to be read,
- * then that's tough and we go away again, on the grounds that the device
- * needs to get some more entropy from somewhere.
- */
-
- if ((fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK)) >= 0 ||
- (fd = open("/dev/arandom", O_RDONLY | O_NONBLOCK)) >= 0 ||
- (fd = open("/dev/random", O_RDONLY | O_NONBLOCK)) >= 0) {
- if ((len = read(fd, buf, sizeof(buf))) > 0) {
- rand_add(r, buf, len, len * 8);
- BURN(buf);
- ret = 1;
- }
- close(fd);
- }
- noise_timer(r);
- return (ret);
-}
-
-/* --- @noise_setid@ --- *
- *
- * Arguments: @uid_t uid@ = uid to set
- * @gid_t gid@ = gid to set
- *
- * Returns: ---
- *
- * Use: Sets the user and group ids to be used by @noise_filter@
- * when running child processes. This is useful to avoid
- * giving shell commands (even carefully written ones) undue
- * privileges. This interface is Unix-specific
- */
-
-void noise_setid(uid_t uid, gid_t gid)
-{
- noise_uid = uid;
- noise_gid = gid;
-}
-
-/* --- @noise_filter@ --- *
- *
- * Arguments: @rand_pool *r@ = pointer to a randomness pool
- * @int good@ = number of good bits per 1024 bits
- * @const char *c@ = shell command to run
- *
- * Returns: Nonzero if some randomness was contributed.
- *
- * Use: Attempts to execute a shell command, and dump it into the
- * randomness pool. A very rough estimate of the number of
- * good bits is made, based on the size of the command's output.
- * This function calls @waitpid@, so be careful. Before execing
- * the command, the process uid and gid are set to the values
- * given to @noise_setid@, and an attempt is made to reset the
- * list of supplementary groups. The environment passed to
- * the command has been severly lobotimized. If the command
- * fails to complete within a short time period, it is killed.
- * Paranoid use of close-on-exec flags for file descriptors is
- * recommended.
- *
- * This interface is Unix-specific.
- */
-
-int noise_filter(rand_pool *r, int good, const char *c)
-{
- char buf[4096];
- pid_t kid;
- int fd[2];
- struct timeval dead;
- int ret = 0;
- const char *env[] = {
- "PATH=/bin:/usr/bin:/sbin:/usr/sbin:/etc",
- 0
- };
-
- /* --- Remember when this business started --- */
-
- gettimeofday(&dead, 0);
- timer(r, &dead);
-
- /* --- Create a pipe --- */
-
- if (pipe(fd))
- return (ret);
-
- /* --- Fork a child off --- */
-
- fflush(0);
- kid = fork();
- if (kid < 0) {
- close(fd[0]);
- close(fd[1]);
- return (ret);
- }
-
- /* --- Handle the child end of the deal --- */
-
- if (kid == 0) {
- int f;
-
- /* --- Set the pipe as standard output, close standard input --- */
-
- close(0); close(1); close(2);
-
- if (fd[1] != 1) {
- if (dup2(fd[1], 1) < 0) _exit(127);
- close(fd[1]);
- }
-
- if ((f = open("/dev/null", O_RDONLY)) != 0 ||
- (f = open("/dev/null", O_WRONLY)) != 2)
- _exit(127);
-
- /* --- Play games with uids --- */
-
- if (noise_gid != NOISE_NOSETGID) {
- setgid(noise_gid);
- setegid(noise_gid);
-#ifdef HAVE_SETGROUPS
- setgroups(1, &noise_gid);
-#endif
- }
-
- if (noise_uid != NOISE_NOSETUID) {
- setuid(noise_uid);
- seteuid(noise_uid);
- }
-
- /* --- Start the process up --- */
-
- execle("/bin/sh", "-c", c, (char *)0, env);
- _exit(127);
- }
-
- /* --- Sort out my end of the deal --- */
-
- close(fd[1]);
-
- /* --- Decide on the deadline --- */
-
- TV_ADDL(&dead, &dead, 0, NOISE_KIDLIFE);
-
- /* --- Now read, and think --- */
-
- for (;;) {
- struct timeval now, diff;
- fd_set rd;
-
- gettimeofday(&now, 0);
- timer(r, &now);
- if (TV_CMP(&now, >, &dead))
- break;
- TV_SUB(&diff, &dead, &now);
-
- FD_ZERO(&rd);
- FD_SET(fd[0], &rd);
-
- if (select(fd[0] + 1, &rd, 0, 0, &diff) < 0)
- break;
- if (FD_ISSET(fd[0], &rd)) {
- ssize_t sz;
- int goodbits;
-
- if ((sz = read(fd[0], buf, sizeof(buf))) <= 0)
- break;
- goodbits = (sz * good) / 128;
- rand_add(r, buf, sz, goodbits);
- ret = 1;
- }
- }
-
- /* --- We've finished with it: kill the child process --- *
- *
- * This is morally questionable. On the other hand, I don't want to be
- * held up in the @waitpid@ call if I can possibly help it. Maybe a
- * double-fork is worth doing here.
- */
-
- close(fd[0]);
- BURN(buf);
- noise_timer(r);
- kill(kid, SIGKILL);
- waitpid(kid, 0, 0);
- return (ret);
-}
-
-/* --- @noise_freewheel@ --- *
- *
- * Arguments: @rand_pool *r@ = pointer to a randomness pool
- *
- * Returns: Nonzero if some randomness was contributed.
- *
- * Use: Runs a free counter for a short while as a desparate attempt
- * to get randomness from somewhere. This is actually quite
- * effective.
- */
-
-#ifdef USE_FREEWHEEL
-
-static jmp_buf fwjmp;
-
-static void fwalarm(int sig)
-{
- siglongjmp(fwjmp, 1);
-}
-
-int noise_freewheel(rand_pool *r)
-{
- void (*sigal)(int) = 0;
- struct itimerval oitv, itv = { { 0, 0 }, { 0, 5000 } };
- int rc = 0;
- volatile uint32 fwcount = 0;
-
- if (!sigsetjmp(fwjmp, 1)) {
- if ((sigal = signal(SIGALRM, fwalarm)) == SIG_ERR)
- return (0);
- if (setitimer(ITIMER_REAL, &itv, &oitv))
- goto done;
- for (;;)
- fwcount++;
- } else {
- octet buf[4];
- STORE32(buf, fwcount);
- rand_add(r, buf, sizeof(buf), 16);
- rc = 1;
- }
-
-done:
- signal(SIGALRM, sigal);
- if (oitv.it_value.tv_sec || oitv.it_value.tv_usec)
- TV_SUB(&oitv.it_value, &oitv.it_value, &itv.it_value);
- setitimer(ITIMER_REAL, &oitv, 0);
- return (rc);
-}
-
-#else
-
-int noise_freewheel(rand_pool *r)
-{
- return (0);
-}
-
-#endif
-
-/* --- @noise_enquire@ --- *
- *
- * Arguments: @rand_pool *r@ = pointer to a randomness pool
- *
- * Returns: Nonzero if some randomness was contributed.
- *
- * Use: Runs some shell commands to enquire about the prevailing
- * environment. This can gather quite a lot of low-quality
- * entropy.
- */
-
-int noise_enquire(rand_pool *r)
-{
- struct tab {
- const char *cmd;
- unsigned rate;
- } tab[] = {
- { "ps alxww || ps -elf", 16 },
- { "netstat -n", 6 },
- { "ifconfig -a", 8 },
- { "df", 20 },
- { "w", 6 },
- { "ls -align /tmp/.", 10 },
- { 0, 0 }
- };
- int i;
-
- for (i = 0; tab[i].cmd; i++)
- noise_filter(r, tab[i].rate, tab[i].cmd);
- return (1);
-}
-
-/* --- @noise_acquire@ --- *
- *
- * Arguments: @rand_pool *r@ = pointer to a randomness pool
- *
- * Returns: ---
- *
- * Use: Acquires some randomness from somewhere.
- */
-
-void noise_acquire(rand_pool *r)
-{
- unsigned i;
- for (i = 0; i < 8; i++)
- noise_freewheel(r);
- if (!noise_devrandom(r)) {
- noise_enquire(r);
- for (i = 0; i < 8; i++)
- noise_freewheel(r);
- }
-}
-
-/*----- That's all, folks -------------------------------------------------*/
projects / u / mdw / catacomb / blobdiff