entropy.c - security/openssh-library - Rivoreo Source Code Repositories

 /*
  * Copyright (c) 2000 Damien Miller.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. All advertising materials mentioning features or use of this software
  *    must display the following acknowledgement:
  *      This product includes software developed by Markus Friedl.
  * 4. The name of the author may not be used to endorse or promote products
  *    derived from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "includes.h"

 #include "ssh.h"
 #include "xmalloc.h"

 #include <openssl/rand.h>
 #include <openssl/sha.h>

 RCSID("$Id: entropy.c,v 1.5 2000/04/16 02:31:50 damien Exp $");

 #ifdef EGD_SOCKET
 #ifndef offsetof
 # define offsetof(type, member) ((size_t) &((type *)0)->member)
 #endif
 /* Collect entropy from EGD */
 void get_random_bytes(unsigned char *buf, int len)
 {
 	static int egd_socket = -1;
 	int c;
 	char egd_message[2] = { 0x02, 0x00 };
 	struct sockaddr_un addr;
 	int addr_len;

 	memset(&addr, '\0', sizeof(addr));
 	addr.sun_family = AF_UNIX;

 	/* FIXME: compile time check? */
 	if (sizeof(EGD_SOCKET) > sizeof(addr.sun_path))
 		fatal("Random pool path is too long");

 	strcpy(addr.sun_path, EGD_SOCKET);

 	addr_len = offsetof(struct sockaddr_un, sun_path) + sizeof(EGD_SOCKET);

 	if (egd_socket == -1) {
 		egd_socket = socket(AF_UNIX, SOCK_STREAM, 0);
 		if (egd_socket == -1)
 			fatal("Couldn't create AF_UNIX socket: %s", strerror(errno));
 		if (connect(egd_socket, (struct sockaddr*)&addr, addr_len) == -1)
 			fatal("Couldn't connect to EGD socket \"%s\": %s", addr.sun_path, strerror(errno));
 	}

 	if (len > 255)
 		fatal("Too many bytes to read from EGD");

 	/* Send blocking read request to EGD */
 	egd_message[1] = len;

 	c = atomicio(write, egd_socket, egd_message, sizeof(egd_message));
 	if (c == -1)
 		fatal("Couldn't write to EGD socket \"%s\": %s", EGD_SOCKET, strerror(errno));

 	c = atomicio(read, egd_socket, buf, len);
 	if (c <= 0)
 		fatal("Couldn't read from EGD socket \"%s\": %s", EGD_SOCKET, strerror(errno));

 	close(EGD_SOCKET);
 }
 #else /* !EGD_SOCKET */
 #ifdef RANDOM_POOL
 /* Collect entropy from /dev/urandom or pipe */
 void get_random_bytes(unsigned char *buf, int len)
 {
 	static int random_pool = -1;
 	int c;

 	if (random_pool == -1) {
 		random_pool = open(RANDOM_POOL, O_RDONLY);
 		if (random_pool == -1)
 			fatal("Couldn't open random pool \"%s\": %s", RANDOM_POOL, strerror(errno));
 	}

 	c = atomicio(read, random_pool, buf, len);
 	if (c <= 0)
 		fatal("Couldn't read from random pool \"%s\": %s", RANDOM_POOL, strerror(errno));
 }
 #endif /* RANDOM_POOL */
 #endif /* EGD_SOCKET */

 #if !defined(EGD_SOCKET) && !defined(RANDOM_POOL)
 /*
  * FIXME: proper entropy estimations. All current values are guesses
  * FIXME: Need timeout for slow moving programs
  * FIXME: More entropy sources
  */

 double stir_from_system(void);
 double stir_from_programs(void);
 double stir_gettimeofday(double entropy_estimate);
 double stir_clock(double entropy_estimate);
 double stir_rusage(int who, double entropy_estimate);
 double hash_output_from_command(const char *path, const char **args, char *hash);

 typedef struct
 {
 	/* Proportion of data that is entropy */
 	double rate;
 	/* Path to executable */
 	const char *path;
 	/* argv to pass to executable */
 	const char *args[5];
 } entropy_source_t;

 entropy_source_t entropy_sources[] = {
 #ifdef PROG_LS
 	{ 0.002, PROG_LS,       { "ls", "-alni", "/var/log", NULL } },
 	{ 0.002, PROG_LS,       { "ls", "-alni", "/var/adm", NULL } },
 	{ 0.002, PROG_LS,       { "ls", "-alni", "/var/mail", NULL } },
 	{ 0.002, PROG_LS,       { "ls", "-alni", "/var/spool/mail", NULL } },
 	{ 0.002, PROG_LS,       { "ls", "-alni", "/proc", NULL } },
 	{ 0.002, PROG_LS,       { "ls", "-alni", "/tmp", NULL } },
 #endif
 #ifdef PROG_NETSTAT
 	{ 0.005, PROG_NETSTAT,  { "netstat","-an", NULL, NULL } },
 	{ 0.010, PROG_NETSTAT,  { "netstat","-in", NULL, NULL } },
 	{ 0.002, PROG_NETSTAT,  { "netstat","-rn", NULL, NULL } },
 	{ 0.002, PROG_NETSTAT,  { "netstat","-s", NULL, NULL } },
 #endif
 #ifdef PROG_ARP
 	{ 0.002, PROG_ARP,      { "arp","-a","-n", NULL } },
 #endif
 #ifdef PROG_IFCONFIG
 	{ 0.002, PROG_IFCONFIG, { "ifconfig", "-a", NULL, NULL } },
 #endif
 #ifdef PROG_PS
 	{ 0.003, PROG_PS,       { "ps", "laxww", NULL, NULL } },
 	{ 0.003, PROG_PS,       { "ps", "-al", NULL, NULL } },
 	{ 0.003, PROG_PS,       { "ps", "-efl", NULL, NULL } },
 #endif
 #ifdef PROG_W
 	{ 0.005, PROG_W,        { "w", NULL, NULL, NULL } },
 #endif
 #ifdef PROG_WHO
 	{ 0.001, PROG_WHO,      { "who","-i", NULL, NULL } },
 #endif
 #ifdef PROG_LAST
 	{ 0.001, PROG_LAST,     { "last", NULL, NULL, NULL } },
 #endif
 #ifdef PROG_LASTLOG
 	{ 0.001, PROG_LASTLOG,  { "lastlog", NULL, NULL, NULL } },
 #endif
 #ifdef PROG_DF
 	{ 0.010, PROG_DF,       { "df", NULL, NULL, NULL } },
 	{ 0.010, PROG_DF,       { "df", "-i", NULL, NULL } },
 #endif
 #ifdef PROG_VMSTAT
 	{ 0.010, PROG_VMSTAT,   { "vmstat", NULL, NULL, NULL } },
 #endif
 #ifdef PROG_UPTIME
 	{ 0.001, PROG_UPTIME,   { "uptime", NULL, NULL, NULL } },
 #endif
 #ifdef PROG_IPCS
 	{ 0.001, PROG_IPCS,     { "-a", NULL, NULL, NULL } },
 #endif
 #ifdef PROG_TAIL
 	{ 0.001, PROG_TAIL,     { "tail", "-200", "/var/log/messages", NULL, NULL } },
 	{ 0.001, PROG_TAIL,     { "tail", "-200", "/var/log/syslog", NULL, NULL } },
 	{ 0.001, PROG_TAIL,     { "tail", "-200", "/var/adm/messages", NULL, NULL } },
 	{ 0.001, PROG_TAIL,     { "tail", "-200", "/var/adm/syslog", NULL, NULL } },
 	{ 0.001, PROG_TAIL,     { "tail", "-200", "/var/log/maillog", NULL, NULL } },
 	{ 0.001, PROG_TAIL,     { "tail", "-200", "/var/adm/maillog", NULL, NULL } },
 #endif
 	{ 0.000, NULL,          { NULL, NULL, NULL, NULL, NULL } },
 };

 double
 stir_from_system(void)
 {
 	double total_entropy_estimate;
 	long int i;

 	total_entropy_estimate = 0;

 	i = getpid();
 	RAND_add(&i, sizeof(i), 0.1);
 	total_entropy_estimate += 0.1;

 	i = getppid();
 	RAND_add(&i, sizeof(i), 0.1);
 	total_entropy_estimate += 0.1;

 	i = getuid();
 	RAND_add(&i, sizeof(i), 0.0);
 	i = getgid();
 	RAND_add(&i, sizeof(i), 0.0);

 	total_entropy_estimate += stir_gettimeofday(1.0);
 	total_entropy_estimate += stir_clock(0.2);
 	total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);

 	return(total_entropy_estimate);
 }

 double
 stir_from_programs(void)
 {
 	int i;
 	int c;
 	double entropy_estimate;
 	double total_entropy_estimate;
 	char hash[SHA_DIGEST_LENGTH];

 	/*
 	 * Run through list of programs twice to catch differences
 	 */
 	total_entropy_estimate = 0;
 	for(i = 0; i < 2; i++) {
 		c = 0;
 		while (entropy_sources[c].path != NULL) {
 			/* Hash output from command */
 			entropy_estimate = hash_output_from_command(entropy_sources[c].path,
 				entropy_sources[c].args, hash);

 			/* Scale back entropy estimate according to command's rate */
 			entropy_estimate *= entropy_sources[c].rate;

 			/* Upper bound of entropy estimate is SHA_DIGEST_LENGTH */
 			if (entropy_estimate > SHA_DIGEST_LENGTH)
 				entropy_estimate = SHA_DIGEST_LENGTH;

  			/* * Scale back estimates for subsequent passes through list */
 			entropy_estimate /= 10.0 * (i + 1.0);

 			/* Stir it in */
 			RAND_add(hash, sizeof(hash), entropy_estimate);

 /* FIXME: turn this off later */
 #if 1
 			debug("Got %0.2f bytes of entropy from %s", entropy_estimate,
 				entropy_sources[c].path);
 #endif

 			total_entropy_estimate += entropy_estimate;

 			/* Execution times should be a little unpredictable */
 			total_entropy_estimate += stir_gettimeofday(0.05);
 			total_entropy_estimate += stir_clock(0.05);
 			total_entropy_estimate += stir_rusage(RUSAGE_SELF, 0.1);
 			total_entropy_estimate += stir_rusage(RUSAGE_CHILDREN, 0.1);

 			c++;
 		}
 	}

 	return(total_entropy_estimate);
 }

 double
 stir_gettimeofday(double entropy_estimate)
 {
 	struct timeval tv;

 	if (gettimeofday(&tv, NULL) == -1)
 		fatal("Couldn't gettimeofday: %s", strerror(errno));

 	RAND_add(&tv, sizeof(tv), entropy_estimate);

 	return(entropy_estimate);
 }

 double
 stir_clock(double entropy_estimate)
 {
 #ifdef HAVE_CLOCK
 	clock_t c;

 	c = clock();
 	RAND_add(&c, sizeof(c), entropy_estimate);

 	return(entropy_estimate);
 #else /* _HAVE_CLOCK */
 	return(0);
 #endif /* _HAVE_CLOCK */
 }

 double
 stir_rusage(int who, double entropy_estimate)
 {
 #ifdef HAVE_GETRUSAGE
 	struct rusage ru;

    if (getrusage(who, &ru) == -1)
 		fatal("Couldn't getrusage: %s", strerror(errno));

 	RAND_add(&ru, sizeof(ru), 0.1);

 	return(entropy_estimate);
 #else /* _HAVE_GETRUSAGE */
 	return(0);
 #endif /* _HAVE_GETRUSAGE */
 }

 double
 hash_output_from_command(const char *path, const char **args, char *hash)
 {
 	static int devnull = -1;
 	int p[2];
 	pid_t pid;
 	int status;
 	char buf[2048];
 	int bytes_read;
 	int total_bytes_read;
 	SHA_CTX sha;

 	if (devnull == -1) {
 		devnull = open("/dev/null", O_RDWR);
 		if (devnull == -1)
 			fatal("Couldn't open /dev/null: %s", strerror(errno));
 	}

 	if (pipe(p) == -1)
 		fatal("Couldn't open pipe: %s", strerror(errno));

 	switch (pid = fork()) {
 		case -1: /* Error */
 			close(p[0]);
 			close(p[1]);
 			fatal("Couldn't fork: %s", strerror(errno));
 			/* NOTREACHED */
 		case 0: /* Child */
 			close(0);
 			close(1);
 			close(2);
 			dup2(devnull, 0);
 			dup2(p[1], 1);
 			dup2(p[1], 2);
 			close(p[0]);
 			close(p[1]);
 			close(devnull);

 			execv(path, (char**)args);
 			debug("(child) Couldn't exec '%s': %s", path, strerror(errno));
 			_exit(-1);
 		default: /* Parent */
 			break;
 	}

 	RAND_add(&pid, sizeof(&pid), 0.0);

 	close(p[1]);

 	/* Hash output from child */
 	SHA1_Init(&sha);
 	total_bytes_read = 0;
 	while ((bytes_read = read(p[0], buf, sizeof(buf)))	> 0) {
 		SHA1_Update(&sha, buf, bytes_read);
 		total_bytes_read += bytes_read;
 		RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
 	}
 	SHA1_Final(hash, &sha);

 	close(p[0]);

 	if (waitpid(pid, &status, 0) == -1) {
 		error("Couldn't wait for child '%s' completion: %s", path,
 			strerror(errno));
 		return(-1);
 	}

 	RAND_add(&status, sizeof(&status), 0.0);

 	if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
 		return(0.0);
 	else
 		return(total_bytes_read);
 }
 #endif /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */

 #if defined(EGD_SOCKET) || defined(RANDOM_POOL)
 /*
  * Seed OpenSSL's random number pool from Kernel random number generator
  * or EGD
  */
 void
 seed_rng(void)
 {
 	char buf[32];

 	debug("Seeding random number generator");
 	get_random_bytes(buf, sizeof(buf));
 	RAND_add(buf, sizeof(buf), sizeof(buf));
 	memset(buf, '\0', sizeof(buf));
 }
 #else /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
 /*
  * Conditionally Seed OpenSSL's random number pool syscalls and program output
  */
 void
 seed_rng(void)
 {
 	debug("Seeding random number generator.");
 	debug("OpenSSL random status is now %i\n", RAND_status());
 	debug("%i bytes from system calls", (int)stir_from_system());
 	debug("%i bytes from programs", (int)stir_from_programs());
 	debug("OpenSSL random status is now %i\n", RAND_status());
 }
 #endif /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
	/*
	* Copyright (c) 2000 Damien Miller. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. All advertising materials mentioning features or use of this software
	* must display the following acknowledgement:
	* This product includes software developed by Markus Friedl.
	* 4. The name of the author may not be used to endorse or promote products
	* derived from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "includes.h"

	#include "ssh.h"
	#include "xmalloc.h"

	#include <openssl/rand.h>
	#include <openssl/sha.h>

	RCSID("$Id: entropy.c,v 1.5 2000/04/16 02:31:50 damien Exp $");

	#ifdef EGD_SOCKET
	#ifndef offsetof
	# define offsetof(type, member) ((size_t) &((type *)0)->member)
	#endif
	/* Collect entropy from EGD */
	void get_random_bytes(unsigned char *buf, int len)
	{
	static int egd_socket = -1;
	int c;
	char egd_message[2] = { 0x02, 0x00 };
	struct sockaddr_un addr;
	int addr_len;

	memset(&addr, '\0', sizeof(addr));
	addr.sun_family = AF_UNIX;

	/* FIXME: compile time check? */
	if (sizeof(EGD_SOCKET) > sizeof(addr.sun_path))
	fatal("Random pool path is too long");

	strcpy(addr.sun_path, EGD_SOCKET);

	addr_len = offsetof(struct sockaddr_un, sun_path) + sizeof(EGD_SOCKET);

	if (egd_socket == -1) {
	egd_socket = socket(AF_UNIX, SOCK_STREAM, 0);
	if (egd_socket == -1)
	fatal("Couldn't create AF_UNIX socket: %s", strerror(errno));
	if (connect(egd_socket, (struct sockaddr*)&addr, addr_len) == -1)
	fatal("Couldn't connect to EGD socket \"%s\": %s", addr.sun_path, strerror(errno));
	}

	if (len > 255)
	fatal("Too many bytes to read from EGD");

	/* Send blocking read request to EGD */
	egd_message[1] = len;

	c = atomicio(write, egd_socket, egd_message, sizeof(egd_message));
	if (c == -1)
	fatal("Couldn't write to EGD socket \"%s\": %s", EGD_SOCKET, strerror(errno));

	c = atomicio(read, egd_socket, buf, len);
	if (c <= 0)
	fatal("Couldn't read from EGD socket \"%s\": %s", EGD_SOCKET, strerror(errno));

	close(EGD_SOCKET);
	}
	#else /* !EGD_SOCKET */
	#ifdef RANDOM_POOL
	/* Collect entropy from /dev/urandom or pipe */
	void get_random_bytes(unsigned char *buf, int len)
	{
	static int random_pool = -1;
	int c;

	if (random_pool == -1) {
	random_pool = open(RANDOM_POOL, O_RDONLY);
	if (random_pool == -1)
	fatal("Couldn't open random pool \"%s\": %s", RANDOM_POOL, strerror(errno));
	}

	c = atomicio(read, random_pool, buf, len);
	if (c <= 0)
	fatal("Couldn't read from random pool \"%s\": %s", RANDOM_POOL, strerror(errno));
	}
	#endif /* RANDOM_POOL */
	#endif /* EGD_SOCKET */

	#if !defined(EGD_SOCKET) && !defined(RANDOM_POOL)
	/*
	* FIXME: proper entropy estimations. All current values are guesses
	* FIXME: Need timeout for slow moving programs
	* FIXME: More entropy sources
	*/

	double stir_from_system(void);
	double stir_from_programs(void);
	double stir_gettimeofday(double entropy_estimate);
	double stir_clock(double entropy_estimate);
	double stir_rusage(int who, double entropy_estimate);
	double hash_output_from_command(const char path, const char args, char hash);

	typedef struct
	{
	/* Proportion of data that is entropy */
	double rate;
	/* Path to executable */
	const char *path;
	/* argv to pass to executable */
	const char *args[5];
	} entropy_source_t;

	entropy_source_t entropy_sources[] = {
	#ifdef PROG_LS
	{ 0.002, PROG_LS, { "ls", "-alni", "/var/log", NULL } },
	{ 0.002, PROG_LS, { "ls", "-alni", "/var/adm", NULL } },
	{ 0.002, PROG_LS, { "ls", "-alni", "/var/mail", NULL } },
	{ 0.002, PROG_LS, { "ls", "-alni", "/var/spool/mail", NULL } },
	{ 0.002, PROG_LS, { "ls", "-alni", "/proc", NULL } },
	{ 0.002, PROG_LS, { "ls", "-alni", "/tmp", NULL } },
	#endif
	#ifdef PROG_NETSTAT
	{ 0.005, PROG_NETSTAT, { "netstat","-an", NULL, NULL } },
	{ 0.010, PROG_NETSTAT, { "netstat","-in", NULL, NULL } },
	{ 0.002, PROG_NETSTAT, { "netstat","-rn", NULL, NULL } },
	{ 0.002, PROG_NETSTAT, { "netstat","-s", NULL, NULL } },
	#endif
	#ifdef PROG_ARP
	{ 0.002, PROG_ARP, { "arp","-a","-n", NULL } },
	#endif
	#ifdef PROG_IFCONFIG
	{ 0.002, PROG_IFCONFIG, { "ifconfig", "-a", NULL, NULL } },
	#endif
	#ifdef PROG_PS
	{ 0.003, PROG_PS, { "ps", "laxww", NULL, NULL } },
	{ 0.003, PROG_PS, { "ps", "-al", NULL, NULL } },
	{ 0.003, PROG_PS, { "ps", "-efl", NULL, NULL } },
	#endif
	#ifdef PROG_W
	{ 0.005, PROG_W, { "w", NULL, NULL, NULL } },
	#endif
	#ifdef PROG_WHO
	{ 0.001, PROG_WHO, { "who","-i", NULL, NULL } },
	#endif
	#ifdef PROG_LAST
	{ 0.001, PROG_LAST, { "last", NULL, NULL, NULL } },
	#endif
	#ifdef PROG_LASTLOG
	{ 0.001, PROG_LASTLOG, { "lastlog", NULL, NULL, NULL } },
	#endif
	#ifdef PROG_DF
	{ 0.010, PROG_DF, { "df", NULL, NULL, NULL } },
	{ 0.010, PROG_DF, { "df", "-i", NULL, NULL } },
	#endif
	#ifdef PROG_VMSTAT
	{ 0.010, PROG_VMSTAT, { "vmstat", NULL, NULL, NULL } },
	#endif
	#ifdef PROG_UPTIME
	{ 0.001, PROG_UPTIME, { "uptime", NULL, NULL, NULL } },
	#endif
	#ifdef PROG_IPCS
	{ 0.001, PROG_IPCS, { "-a", NULL, NULL, NULL } },
	#endif
	#ifdef PROG_TAIL
	{ 0.001, PROG_TAIL, { "tail", "-200", "/var/log/messages", NULL, NULL } },
	{ 0.001, PROG_TAIL, { "tail", "-200", "/var/log/syslog", NULL, NULL } },
	{ 0.001, PROG_TAIL, { "tail", "-200", "/var/adm/messages", NULL, NULL } },
	{ 0.001, PROG_TAIL, { "tail", "-200", "/var/adm/syslog", NULL, NULL } },
	{ 0.001, PROG_TAIL, { "tail", "-200", "/var/log/maillog", NULL, NULL } },
	{ 0.001, PROG_TAIL, { "tail", "-200", "/var/adm/maillog", NULL, NULL } },
	#endif
	{ 0.000, NULL, { NULL, NULL, NULL, NULL, NULL } },
	};

	double
	stir_from_system(void)
	{
	double total_entropy_estimate;
	long int i;

	total_entropy_estimate = 0;

	i = getpid();
	RAND_add(&i, sizeof(i), 0.1);
	total_entropy_estimate += 0.1;

	i = getppid();
	RAND_add(&i, sizeof(i), 0.1);
	total_entropy_estimate += 0.1;

	i = getuid();
	RAND_add(&i, sizeof(i), 0.0);
	i = getgid();
	RAND_add(&i, sizeof(i), 0.0);

	total_entropy_estimate += stir_gettimeofday(1.0);
	total_entropy_estimate += stir_clock(0.2);
	total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);

	return(total_entropy_estimate);
	}

	double
	stir_from_programs(void)
	{
	int i;
	int c;
	double entropy_estimate;
	double total_entropy_estimate;
	char hash[SHA_DIGEST_LENGTH];

	/*
	* Run through list of programs twice to catch differences
	*/
	total_entropy_estimate = 0;
	for(i = 0; i < 2; i++) {
	c = 0;
	while (entropy_sources[c].path != NULL) {
	/* Hash output from command */
	entropy_estimate = hash_output_from_command(entropy_sources[c].path,
	entropy_sources[c].args, hash);

	/* Scale back entropy estimate according to command's rate */
	entropy_estimate *= entropy_sources[c].rate;

	/* Upper bound of entropy estimate is SHA_DIGEST_LENGTH */
	if (entropy_estimate > SHA_DIGEST_LENGTH)
	entropy_estimate = SHA_DIGEST_LENGTH;

	/* * Scale back estimates for subsequent passes through list */
	entropy_estimate /= 10.0 * (i + 1.0);

	/* Stir it in */
	RAND_add(hash, sizeof(hash), entropy_estimate);

	/* FIXME: turn this off later */
	#if 1
	debug("Got %0.2f bytes of entropy from %s", entropy_estimate,
	entropy_sources[c].path);
	#endif

	total_entropy_estimate += entropy_estimate;

	/* Execution times should be a little unpredictable */
	total_entropy_estimate += stir_gettimeofday(0.05);
	total_entropy_estimate += stir_clock(0.05);
	total_entropy_estimate += stir_rusage(RUSAGE_SELF, 0.1);
	total_entropy_estimate += stir_rusage(RUSAGE_CHILDREN, 0.1);

	c++;
	}
	}

	return(total_entropy_estimate);
	}

	double
	stir_gettimeofday(double entropy_estimate)
	{
	struct timeval tv;

	if (gettimeofday(&tv, NULL) == -1)
	fatal("Couldn't gettimeofday: %s", strerror(errno));

	RAND_add(&tv, sizeof(tv), entropy_estimate);

	return(entropy_estimate);
	}

	double
	stir_clock(double entropy_estimate)
	{
	#ifdef HAVE_CLOCK
	clock_t c;

	c = clock();
	RAND_add(&c, sizeof(c), entropy_estimate);

	return(entropy_estimate);
	#else /* _HAVE_CLOCK */
	return(0);
	#endif /* _HAVE_CLOCK */
	}

	double
	stir_rusage(int who, double entropy_estimate)
	{
	#ifdef HAVE_GETRUSAGE
	struct rusage ru;

	if (getrusage(who, &ru) == -1)
	fatal("Couldn't getrusage: %s", strerror(errno));

	RAND_add(&ru, sizeof(ru), 0.1);

	return(entropy_estimate);
	#else /* _HAVE_GETRUSAGE */
	return(0);
	#endif /* _HAVE_GETRUSAGE */
	}

	double
	hash_output_from_command(const char path, const char args, char hash)
	{
	static int devnull = -1;
	int p[2];
	pid_t pid;
	int status;
	char buf[2048];
	int bytes_read;
	int total_bytes_read;
	SHA_CTX sha;

	if (devnull == -1) {
	devnull = open("/dev/null", O_RDWR);
	if (devnull == -1)
	fatal("Couldn't open /dev/null: %s", strerror(errno));
	}

	if (pipe(p) == -1)
	fatal("Couldn't open pipe: %s", strerror(errno));

	switch (pid = fork()) {
	case -1: /* Error */
	close(p[0]);
	close(p[1]);
	fatal("Couldn't fork: %s", strerror(errno));
	/* NOTREACHED */
	case 0: /* Child */
	close(0);
	close(1);
	close(2);
	dup2(devnull, 0);
	dup2(p[1], 1);
	dup2(p[1], 2);
	close(p[0]);
	close(p[1]);
	close(devnull);

	execv(path, (char**)args);
	debug("(child) Couldn't exec '%s': %s", path, strerror(errno));
	_exit(-1);
	default: /* Parent */
	break;
	}

	RAND_add(&pid, sizeof(&pid), 0.0);

	close(p[1]);

	/* Hash output from child */
	SHA1_Init(&sha);
	total_bytes_read = 0;
	while ((bytes_read = read(p[0], buf, sizeof(buf))) > 0) {
	SHA1_Update(&sha, buf, bytes_read);
	total_bytes_read += bytes_read;
	RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
	}
	SHA1_Final(hash, &sha);

	close(p[0]);

	if (waitpid(pid, &status, 0) == -1) {
	error("Couldn't wait for child '%s' completion: %s", path,
	strerror(errno));
	return(-1);
	}

	RAND_add(&status, sizeof(&status), 0.0);

	if (!WIFEXITED(status) \|\| (WEXITSTATUS(status) != 0))
	return(0.0);
	else
	return(total_bytes_read);
	}
	#endif /* defined(EGD_SOCKET) \|\| defined(RANDOM_POOL) */

	#if defined(EGD_SOCKET) \|\| defined(RANDOM_POOL)
	/*
	* Seed OpenSSL's random number pool from Kernel random number generator
	* or EGD
	*/
	void
	seed_rng(void)
	{
	char buf[32];

	debug("Seeding random number generator");
	get_random_bytes(buf, sizeof(buf));
	RAND_add(buf, sizeof(buf), sizeof(buf));
	memset(buf, '\0', sizeof(buf));
	}
	#else /* defined(EGD_SOCKET) \|\| defined(RANDOM_POOL) */
	/*
	* Conditionally Seed OpenSSL's random number pool syscalls and program output
	*/
	void
	seed_rng(void)
	{
	debug("Seeding random number generator.");
	debug("OpenSSL random status is now %i\n", RAND_status());
	debug("%i bytes from system calls", (int)stir_from_system());
	debug("%i bytes from programs", (int)stir_from_programs());
	debug("OpenSSL random status is now %i\n", RAND_status());
	}
	#endif /* defined(EGD_SOCKET) \|\| defined(RANDOM_POOL) */