ssh-rand-helper.c

OpenSSL Source code for SFTP, SSH, and many others

/*
 * Copyright (c) 2001-2002 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.
 *
 * 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 <openssl/rand.h>
#include <openssl/sha.h>
#include <openssl/crypto.h>

/* SunOS 4.4.4 needs this */
#ifdef HAVE_FLOATINGPOINT_H
# include <floatingpoint.h>
#endif /* HAVE_FLOATINGPOINT_H */

#include "misc.h"
#include "xmalloc.h"
#include "atomicio.h"
#include "pathnames.h"
#include "log.h"

RCSID("$Id: ssh-rand-helper.c,v 1.7 2002/06/09 19:41:49 mouring Exp $");

/* Number of bytes we write out */
#define OUTPUT_SEED_SIZE	48

/* Length of on-disk seedfiles */
#define SEED_FILE_SIZE		1024

/* Maximum number of command-line arguments to read from file */
#define NUM_ARGS		10

/* Minimum number of usable commands to be considered sufficient */
#define MIN_ENTROPY_SOURCES	16

/* Path to on-disk seed file (relative to user's home directory */
#ifndef SSH_PRNG_SEED_FILE
# define SSH_PRNG_SEED_FILE      _PATH_SSH_USER_DIR"/prng_seed"
#endif

/* Path to PRNG commands list */
#ifndef SSH_PRNG_COMMAND_FILE
# define SSH_PRNG_COMMAND_FILE   SSHDIR "/ssh_prng_cmds"
#endif


#ifdef HAVE___PROGNAME
extern char *__progname;
#else
char *__progname;
#endif

#ifndef offsetof
# define offsetof(type, member) ((size_t) &((type *)0)->member)
#endif

#define WHITESPACE " \t\n"

#ifndef RUSAGE_SELF
# define RUSAGE_SELF 0
#endif
#ifndef RUSAGE_CHILDREN
# define RUSAGE_CHILDREN 0
#endif

#if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT)
# define USE_SEED_FILES
#endif

typedef struct {
	/* Proportion of data that is entropy */
	double rate;
	/* Counter goes positive if this command times out */
	unsigned int badness;
	/* Increases by factor of two each timeout */
	unsigned int sticky_badness;
	/* Path to executable */
	char *path;
	/* argv to pass to executable */
	char *args[NUM_ARGS]; /* XXX: arbitrary limit */
	/* full command string (debug) */
	char *cmdstring;
} entropy_cmd_t;

/* slow command timeouts (all in milliseconds) */
/* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;

/* this is initialised from a file, by prng_read_commands() */
static entropy_cmd_t *entropy_cmds = NULL;

/* Prototypes */
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_command_output(entropy_cmd_t *src, char *hash);
int get_random_bytes_prngd(unsigned char *buf, int len, 
    unsigned short tcp_port, char *socket_path);

/*
 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
 * listening either on 'tcp_port', or via Unix domain socket at *
 * 'socket_path'.
 * Either a non-zero tcp_port or a non-null socket_path must be 
 * supplied.
 * Returns 0 on success, -1 on error
 */
int
get_random_bytes_prngd(unsigned char *buf, int len, 
    unsigned short tcp_port, char *socket_path)
{
	int fd, addr_len, rval, errors;
	char msg[2];
	struct sockaddr_storage addr;
	struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
	struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
	mysig_t old_sigpipe;

	/* Sanity checks */
	if (socket_path == NULL && tcp_port == 0)
		fatal("You must specify a port or a socket");
	if (socket_path != NULL &&
	    strlen(socket_path) >= sizeof(addr_un->sun_path))
		fatal("Random pool path is too long");
	if (len > 255)
		fatal("Too many bytes to read from PRNGD");

	memset(&addr, '\0', sizeof(addr));

	if (tcp_port != 0) {
		addr_in->sin_family = AF_INET;
		addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
		addr_in->sin_port = htons(tcp_port);
		addr_len = sizeof(*addr_in);
	} else {
		addr_un->sun_family = AF_UNIX;
		strlcpy(addr_un->sun_path, socket_path,
		    sizeof(addr_un->sun_path));
		addr_len = offsetof(struct sockaddr_un, sun_path) +
		    strlen(socket_path) + 1;
	}

	old_sigpipe = mysignal(SIGPIPE, SIG_IGN);

	errors = 0;
	rval = -1;
reopen:
	fd = socket(addr.ss_family, SOCK_STREAM, 0);
	if (fd == -1) {
		error("Couldn't create socket: %s", strerror(errno));
		goto done;
	}

	if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
		if (tcp_port != 0) {
			error("Couldn't connect to PRNGD port %d: %s",
			    tcp_port, strerror(errno));
		} else {
			error("Couldn't connect to PRNGD socket \"%s\": %s",
			    addr_un->sun_path, strerror(errno));
		}
		goto done;
	}

	/* Send blocking read request to PRNGD */
	msg[0] = 0x02;
	msg[1] = len;

	if (atomicio(write, fd, msg, sizeof(msg)) != sizeof(msg)) {
		if (errno == EPIPE && errors < 10) {
			close(fd);
			errors++;
			goto reopen;
		}
		error("Couldn't write to PRNGD socket: %s",
		    strerror(errno));
		goto done;
	}

	if (atomicio(read, fd, buf, len) != len) {
		if (errno == EPIPE && errors < 10) {
			close(fd);
			errors++;
			goto reopen;
		}
		error("Couldn't read from PRNGD socket: %s",
		    strerror(errno));
		goto done;
	}

	rval = 0;
done:
	mysignal(SIGPIPE, old_sigpipe);
	if (fd != -1)
		close(fd);
	return rval;
}

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)
		return 0;

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

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

static int
timeval_diff(struct timeval *t1, struct timeval *t2)
{
	int secdiff, usecdiff;

	secdiff = t2->tv_sec - t1->tv_sec;
	usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
	return (int)(usecdiff / 1000);
}

double
hash_command_output(entropy_cmd_t *src, char *hash)
{
	char buf[8192];
	fd_set rdset;
	int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2];
	int status, total_bytes_read;
	static int devnull = -1;
	pid_t pid;
	SHA_CTX sha;
	struct timeval tv_start, tv_current;

	debug3("Reading output from \'%s\'", src->cmdstring);

	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));

	(void)gettimeofday(&tv_start, NULL); /* record start time */

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

			execv(src->path, (char**)(src->args));

			debug("(child) Couldn't exec '%s': %s", 
			    src->cmdstring, strerror(errno));
			_exit(-1);
		default: /* Parent */
			break;
	}

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

	close(p[1]);

	/* Hash output from child */
	SHA1_Init(&sha);

	cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0;
	while (!error_abort && !cmd_eof) {
		int ret;
		struct timeval tv;
		int msec_remaining;

		(void) gettimeofday(&tv_current, 0);
		msec_elapsed = timeval_diff(&tv_start, &tv_current);
		if (msec_elapsed >= entropy_timeout_current) {
			error_abort=1;
			continue;
		}
		msec_remaining = entropy_timeout_current - msec_elapsed;

		FD_ZERO(&rdset);
		FD_SET(p[0], &rdset);
		tv.tv_sec = msec_remaining / 1000;
		tv.tv_usec = (msec_remaining % 1000) * 1000;

		ret = select(p[0] + 1, &rdset, NULL, NULL, &tv);

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

		switch (ret) {
		case 0:
			/* timer expired */
			error_abort = 1;
			break;
		case 1:
			/* command input */
			do {
				bytes_read = read(p[0], buf, sizeof(buf));
			} while (bytes_read == -1 && errno == EINTR);
			RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
			if (bytes_read == -1) {
				error_abort = 1;
				break;
			} else if (bytes_read) {
				SHA1_Update(&sha, buf, bytes_read);
				total_bytes_read += bytes_read;
			} else {
				cmd_eof = 1;
			}
			break;
		case -1:
		default:
			/* error */
			debug("Command '%s': select() failed: %s", 
			    src->cmdstring, strerror(errno));
			error_abort = 1;
			break;
		}
	}

	SHA1_Final(hash, &sha);

	close(p[0]);

	debug3("Time elapsed: %d msec", msec_elapsed);

	if (waitpid(pid, &status, 0) == -1) {
	       error("Couldn't wait for child '%s' completion: %s",
		   src->cmdstring, strerror(errno));
		return 0.0;
	}

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

	if (error_abort) {
		/*
		 * Closing p[0] on timeout causes the entropy command to
		 * SIGPIPE. Take whatever output we got, and mark this 
		 * command as slow 
		 */
		debug2("Command '%s' timed out", src->cmdstring);
		src->sticky_badness *= 2;
		src->badness = src->sticky_badness;
		return total_bytes_read;
	}

	if (WIFEXITED(status)) {
		if (WEXITSTATUS(status) == 0) {
			return total_bytes_read;
		} else {
			debug2("Command '%s' exit status was %d",
			    src->cmdstring, WEXITSTATUS(status));
			src->badness = src->sticky_badness = 128;
			return 0.0;
		}
	} else if (WIFSIGNALED(status)) {
		debug2("Command '%s' returned on uncaught signal %d !",
		    src->cmdstring, status);
		src->badness = src->sticky_badness = 128;
		return 0.0;
	} else
		return 0.0;
}

double
stir_from_system(void)
{
	double total_entropy_estimate;