X-Git-Url: http://andersk.mit.edu/gitweb/gssapi-openssh.git/blobdiff_plain/0fff78ff85eabb96f2600c7996ab2a6ffd21e706..HEAD:/openssh/entropy.c

diff --git a/openssh/entropy.c b/openssh/entropy.c
index 2d8cec0..9588f79 100644
--- a/openssh/entropy.c
+++ b/openssh/entropy.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001 Damien Miller.  All rights reserved.
+ * 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
@@ -25,8 +25,14 @@
 #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 "ssh.h"
 #include "misc.h"
 #include "xmalloc.h"
@@ -34,121 +40,878 @@
 #include "pathnames.h"
 #include "log.h"
 
-/*
- * Portable OpenSSH PRNG seeding:
- * If OpenSSL has not "internally seeded" itself (e.g. pulled data from 
- * /dev/random), then we execute a "ssh-rand-helper" program which 
- * collects entropy and writes it to stdout. The child program must 
- * write at least RANDOM_SEED_SIZE bytes. The child is run with stderr
- * attached, so error/debugging output should be visible.
- *
- * XXX: we should tell the child how many bytes we need.
- */
-
 RCSID("$Id$");
 
-#ifndef OPENSSL_PRNG_ONLY
-#define RANDOM_SEED_SIZE 48
-static uid_t original_uid, original_euid;
+#ifndef offsetof
+# define offsetof(type, member) ((size_t) &((type *)0)->member)
+#endif
+
+/* Number of times to pass through command list gathering entropy */
+#define NUM_ENTROPY_RUNS	1
+
+/* Scale entropy estimates back by this amount on subsequent runs */
+#define SCALE_PER_RUN		10.0
+
+/* Minimum number of commands to be considered valid */
+#define MIN_ENTROPY_SOURCES 16
+
+#define WHITESPACE " \t\n"
+
+#ifndef RUSAGE_SELF
+# define RUSAGE_SELF 0
+#endif
+#ifndef RUSAGE_CHILDREN
+# define RUSAGE_CHILDREN 0
+#endif
+
+#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
+# define SAVED_IDS_WORK_WITH_SETEUID
+#endif
+
+static void
+check_openssl_version(void) 
+{
+	if (SSLeay() != OPENSSL_VERSION_NUMBER)
+		fatal("OpenSSL version mismatch. Built against %lx, you "
+		    "have %lx", OPENSSL_VERSION_NUMBER, SSLeay());
+}
+
+#if defined(PRNGD_SOCKET) || defined(PRNGD_PORT)
+# define USE_PRNGD
+#endif
+
+#if defined(USE_PRNGD) || defined(RANDOM_POOL)
+
+#ifdef USE_PRNGD
+/* Collect entropy from PRNGD/EGD */
+int
+get_random_bytes(unsigned char *buf, int len)
+{
+	int fd;
+	char msg[2];
+#ifdef PRNGD_PORT
+	struct sockaddr_in addr;
+#else
+	struct sockaddr_un addr;
+#endif
+	int addr_len, rval, errors;
+	mysig_t old_sigpipe;
+
+	memset(&addr, '\0', sizeof(addr));
+
+#ifdef PRNGD_PORT
+	addr.sin_family = AF_INET;
+	addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+	addr.sin_port = htons(PRNGD_PORT);
+	addr_len = sizeof(struct sockaddr_in);
+#else /* use IP socket PRNGD_SOCKET instead */
+	/* Sanity checks */
+	if (sizeof(PRNGD_SOCKET) > sizeof(addr.sun_path))
+		fatal("Random pool path is too long");
+	if (len > 255)
+		fatal("Too many bytes to read from PRNGD");
+
+	addr.sun_family = AF_UNIX;
+	strlcpy(addr.sun_path, PRNGD_SOCKET, sizeof(addr.sun_path));
+	addr_len = offsetof(struct sockaddr_un, sun_path) +
+	    sizeof(PRNGD_SOCKET);
+#endif
+
+	old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
+
+	errors = rval = 0;
+reopen:
+#ifdef PRNGD_PORT
+	fd = socket(addr.sin_family, SOCK_STREAM, 0);
+	if (fd == -1) {
+		error("Couldn't create AF_INET socket: %s", strerror(errno));
+		goto done;
+	}
+#else
+	fd = socket(addr.sun_family, SOCK_STREAM, 0);
+	if (fd == -1) {
+		error("Couldn't create AF_UNIX socket: %s", strerror(errno));
+		goto done;
+	}
+#endif
+
+	if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
+#ifdef PRNGD_PORT
+		error("Couldn't connect to PRNGD port %d: %s",
+		    PRNGD_PORT, strerror(errno));
+#else
+		error("Couldn't connect to PRNGD socket \"%s\": %s",
+		    addr.sun_path, strerror(errno));
 #endif
+		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 = 1;
+done:
+	mysignal(SIGPIPE, old_sigpipe);
+	if (fd != -1)
+		close(fd);
+	return(rval);
+}
+#else /* !USE_PRNGD */
+#ifdef RANDOM_POOL
+/* Collect entropy from /dev/urandom or pipe */
+static int
+get_random_bytes(unsigned char *buf, int len)
+{
+	int random_pool;
+
+	random_pool = open(RANDOM_POOL, O_RDONLY);
+	if (random_pool == -1) {
+		error("Couldn't open random pool \"%s\": %s",
+			RANDOM_POOL, strerror(errno));
+		return(0);
+	}
+
+	if (atomicio(read, random_pool, buf, len) != len) {
+		error("Couldn't read from random pool \"%s\": %s",
+			RANDOM_POOL, strerror(errno));
+		close(random_pool);
+		return(0);
+	}
+
+	close(random_pool);
+
+	return(1);
+}
+#endif /* RANDOM_POOL */
+#endif /* USE_PRNGD */
+
+/*
+ * Seed OpenSSL's random number pool from Kernel random number generator
+ * or PRNGD/EGD
+ */
 void
 seed_rng(void)
 {
-#ifndef OPENSSL_PRNG_ONLY
-	int devnull;
+	unsigned char buf[32];
+
+	debug("Seeding random number generator");
+
+	if (!get_random_bytes(buf, sizeof(buf))) {
+		if (!RAND_status())
+			fatal("Entropy collection failed and entropy exhausted");
+	} else {
+		RAND_add(buf, sizeof(buf), sizeof(buf));
+	}
+
+	memset(buf, '\0', sizeof(buf));
+}
+
+void
+init_rng(void) 
+{
+	check_openssl_version();
+}
+
+#else /* defined(USE_PRNGD) || defined(RANDOM_POOL) */
+
+/*
+ * FIXME: proper entropy estimations. All current values are guesses
+ * FIXME: (ATL) do estimates at compile time?
+ * FIXME: More entropy sources
+ */
+
+/* slow command timeouts (all in milliseconds) */
+/* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
+static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
+
+static int prng_seed_saved = 0;
+static int prng_initialised = 0;
+uid_t original_uid;
+
+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[5];
+	/* full command string (debug) */
+	char *cmdstring;
+} entropy_source_t;
+
+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(entropy_source_t *src, char *hash);
+
+/* this is initialised from a file, by prng_read_commands() */
+entropy_source_t *entropy_sources = NULL;
+
+double
+stir_from_system(void)
+{
+	double total_entropy_estimate;
+	long int i;
+
+	total_entropy_estimate = 0;
+
+	i = getpid();
+	RAND_add(&i, sizeof(i), 0.5);
+	total_entropy_estimate += 0.1;
+
+	i = getppid();
+	RAND_add(&i, sizeof(i), 0.5);
+	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(0.5);
+	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];
+
+	total_entropy_estimate = 0;
+	for(i = 0; i < NUM_ENTROPY_RUNS; i++) {
+		c = 0;
+		while (entropy_sources[c].path != NULL) {
+
+			if (!entropy_sources[c].badness) {
+				/* Hash output from command */
+				entropy_estimate = hash_output_from_command(&entropy_sources[c], 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 /= SCALE_PER_RUN * (i + 1.0);
+
+				/* Stir it in */
+				RAND_add(hash, sizeof(hash), entropy_estimate);
+
+				debug3("Got %0.2f bytes of entropy from '%s'", entropy_estimate,
+					entropy_sources[c].cmdstring);
+
+				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);
+			} else {
+				debug2("Command '%s' disabled (badness %d)",
+					entropy_sources[c].cmdstring, entropy_sources[c].badness);
+
+				if (entropy_sources[c].badness > 0)
+					entropy_sources[c].badness--;
+			}
+
+			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)
+		return(0);
+
+	RAND_add(&ru, sizeof(ru), entropy_estimate);
+
+	return(entropy_estimate);
+#else /* _HAVE_GETRUSAGE */
+	return(0);
+#endif /* _HAVE_GETRUSAGE */
+}
+
+
+static int
+_get_timeval_msec_difference(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_output_from_command(entropy_source_t *src, char *hash)
+{
+	static int devnull = -1;
 	int p[2];
+	fd_set rdset;
+	int cmd_eof = 0, error_abort = 0;
+	struct timeval tv_start, tv_current;
+	int msec_elapsed = 0;
 	pid_t pid;
-	int ret;
-	unsigned char buf[RANDOM_SEED_SIZE];
-	mysig_t old_sigchld;
+	int status;
+	char buf[16384];
+	int bytes_read;
+	int total_bytes_read;
+	SHA_CTX sha;
 
-	if (RAND_status() == 1) {
-		debug3("RNG is ready, skipping seeding");
-		return;
-	}
+	debug3("Reading output from \'%s\'", src->cmdstring);
 
-	debug3("Seeding PRNG from %s", SSH_RAND_HELPER);
+	if (devnull == -1) {
+		devnull = open("/dev/null", O_RDWR);
+		if (devnull == -1)
+			fatal("Couldn't open /dev/null: %s", strerror(errno));
+	}
 
-	if ((devnull = open("/dev/null", O_RDWR)) == -1)
-		fatal("Couldn't open /dev/null: %s", strerror(errno));
 	if (pipe(p) == -1)
-		fatal("pipe: %s", strerror(errno));
-
-	old_sigchld = signal(SIGCHLD, SIG_DFL);
-	if ((pid = fork()) == -1)
-		fatal("Couldn't fork: %s", strerror(errno));
-	if (pid == 0) {
-		dup2(devnull, STDIN_FILENO);
-		dup2(p[1], STDOUT_FILENO);
-		/* Keep stderr open for errors */
-		close(p[0]);
-		close(p[1]);
-		close(devnull);
-
-		if (original_uid != original_euid && 
-		    ( seteuid(getuid()) == -1 || 
-		      setuid(original_uid) == -1) ) {
-			fprintf(stderr, "(rand child) setuid(%li): %s\n", 
-			    (long int)original_uid, strerror(errno));
-			_exit(1);
-		}
-		
-		execl(SSH_RAND_HELPER, "ssh-rand-helper", NULL);
-		fprintf(stderr, "(rand child) Couldn't exec '%s': %s\n", 
-		    SSH_RAND_HELPER, strerror(errno));
-		_exit(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);
+
+			setuid(original_uid);
+			execv(src->path, (char**)(src->args));
+			debug("(child) Couldn't exec '%s': %s", src->cmdstring,
+			      strerror(errno));
+			_exit(-1);
+		default: /* Parent */
+			break;
 	}
 
-	close(devnull);
+	RAND_add(&pid, sizeof(&pid), 0.0);
+
 	close(p[1]);
 
-	memset(buf, '\0', sizeof(buf));
-	ret = atomicio(read, p[0], buf, sizeof(buf));
-	if (ret == -1)
-		fatal("Couldn't read from ssh-rand-helper: %s",
-		    strerror(errno));
-	if (ret != sizeof(buf))
-		fatal("ssh-rand-helper child produced insufficient data");
+	/* Hash output from child */
+	SHA1_Init(&sha);
+	total_bytes_read = 0;
+
+	while (!error_abort && !cmd_eof) {
+		int ret;
+		struct timeval tv;
+		int msec_remaining;
+
+		(void) gettimeofday(&tv_current, 0);
+		msec_elapsed = _get_timeval_msec_difference(&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]);
 
-	if (waitpid(pid, &ret, 0) == -1)
-	       fatal("Couldn't wait for ssh-rand-helper completion: %s", 
-		   strerror(errno));
-	signal(SIGCHLD, old_sigchld);
+	debug3("Time elapsed: %d msec", msec_elapsed);
 
-	/* We don't mind if the child exits upon a SIGPIPE */
-	if (!WIFEXITED(ret) && 
-	    (!WIFSIGNALED(ret) || WTERMSIG(ret) != SIGPIPE))
-		fatal("ssh-rand-helper terminated abnormally");
-	if (WEXITSTATUS(ret) != 0)
-		fatal("ssh-rand-helper exit with exit status %d", ret);
+	if (waitpid(pid, &status, 0) == -1) {
+	       error("Couldn't wait for child '%s' completion: %s", src->cmdstring,
+		     strerror(errno));
+		return(0.0);
+	}
 
-	RAND_add(buf, sizeof(buf), sizeof(buf));
-	memset(buf, '\0', sizeof(buf));
+	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);
+}
+
+/*
+ * prng seedfile functions
+ */
+int
+prng_check_seedfile(char *filename) {
+
+	struct stat st;
+
+	/* FIXME raceable: eg replace seed between this stat and subsequent open */
+	/* Not such a problem because we don't trust the seed file anyway */
+	if (lstat(filename, &st) == -1) {
+		/* Give up on hard errors */
+		if (errno != ENOENT)
+			debug("WARNING: Couldn't stat random seed file \"%s\": %s",
+			   filename, strerror(errno));
+
+		return(0);
+	}
+
+	/* regular file? */
+	if (!S_ISREG(st.st_mode))
+		fatal("PRNG seedfile %.100s is not a regular file", filename);
+
+	/* mode 0600, owned by root or the current user? */
+	if (((st.st_mode & 0177) != 0) || !(st.st_uid == original_uid)) {
+		debug("WARNING: PRNG seedfile %.100s must be mode 0600, owned by uid %d",
+			 filename, getuid());
+		return(0);
+	}
 
-#endif /* OPENSSL_PRNG_ONLY */
-	if (RAND_status() != 1)
-		fatal("PRNG is not seeded");
+	return(1);
 }
 
 void
-init_rng(void) 
+prng_write_seedfile(void) {
+	int fd;
+	char seed[1024];
+	char filename[1024];
+	struct passwd *pw;
+
+	/* Don't bother if we have already saved a seed */
+	if (prng_seed_saved)
+		return;
+
+	setuid(original_uid);
+
+	prng_seed_saved = 1;
+
+	pw = getpwuid(original_uid);
+	if (pw == NULL)
+		fatal("Couldn't get password entry for current user (%i): %s",
+			original_uid, strerror(errno));
+
+	/* Try to ensure that the parent directory is there */
+	snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
+		_PATH_SSH_USER_DIR);
+	mkdir(filename, 0700);
+
+	snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
+		SSH_PRNG_SEED_FILE);
+
+	debug("writing PRNG seed to file %.100s", filename);
+
+	RAND_bytes(seed, sizeof(seed));
+
+	/* Don't care if the seed doesn't exist */
+	prng_check_seedfile(filename);
+
+	if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1) {
+		debug("WARNING: couldn't access PRNG seedfile %.100s (%.100s)",
+		   filename, strerror(errno));
+	} else {
+		if (atomicio(write, fd, &seed, sizeof(seed)) != sizeof(seed))
+			fatal("problem writing PRNG seedfile %.100s (%.100s)", filename,
+				 strerror(errno));
+
+		close(fd);
+	}
+}
+
+void
+prng_read_seedfile(void) {
+	int fd;
+	char seed[1024];
+	char filename[1024];
+	struct passwd *pw;
+
+	pw = getpwuid(original_uid);
+	if (pw == NULL)
+		fatal("Couldn't get password entry for current user (%i): %s",
+			original_uid, strerror(errno));
+
+	snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
+		SSH_PRNG_SEED_FILE);
+
+	debug("loading PRNG seed from file %.100s", filename);
+
+	if (!prng_check_seedfile(filename)) {
+		verbose("Random seed file not found or not valid, ignoring.");
+		return;
+	}
+
+	/* open the file and read in the seed */
+	fd = open(filename, O_RDONLY);
+	if (fd == -1)
+		fatal("could not open PRNG seedfile %.100s (%.100s)", filename,
+			strerror(errno));
+
+	if (atomicio(read, fd, &seed, sizeof(seed)) != sizeof(seed)) {
+		verbose("invalid or short read from PRNG seedfile %.100s - ignoring",
+			filename);
+		memset(seed, '\0', sizeof(seed));
+	}
+	close(fd);
+
+	/* stir in the seed, with estimated entropy zero */
+	RAND_add(&seed, sizeof(seed), 0.0);
+}
+
+
+/*
+ * entropy command initialisation functions
+ */
+int
+prng_read_commands(char *cmdfilename)
+{
+	FILE *f;
+	char *cp;
+	char line[1024];
+	char cmd[1024];
+	char path[256];
+	int linenum;
+	int num_cmds = 64;
+	int cur_cmd = 0;
+	double est;
+	entropy_source_t *entcmd;
+
+	f = fopen(cmdfilename, "r");
+	if (!f) {
+		fatal("couldn't read entropy commands file %.100s: %.100s",
+		    cmdfilename, strerror(errno));
+	}
+
+	entcmd = (entropy_source_t *)xmalloc(num_cmds * sizeof(entropy_source_t));
+	memset(entcmd, '\0', num_cmds * sizeof(entropy_source_t));
+
+	/* Read in file */
+	linenum = 0;
+	while (fgets(line, sizeof(line), f)) {
+		int arg;
+		char *argv;
+
+		linenum++;
+
+		/* skip leading whitespace, test for blank line or comment */
+		cp = line + strspn(line, WHITESPACE);
+		if ((*cp == 0) || (*cp == '#'))
+			continue; /* done with this line */
+
+		/* First non-whitespace char should be double quote delimiting */
+		/* commandline */
+		if (*cp != '"') {
+			error("bad entropy command, %.100s line %d", cmdfilename,
+			     linenum);
+			continue;
+		}
+
+		/* first token, command args (incl. argv[0]) in double quotes */
+		cp = strtok(cp, "\"");
+		if (cp == NULL) {
+			error("missing or bad command string, %.100s line %d -- ignored",
+			      cmdfilename, linenum);
+			continue;
+		}
+		strlcpy(cmd, cp, sizeof(cmd));
+
+		/* second token, full command path */
+		if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
+			error("missing command path, %.100s line %d -- ignored",
+			      cmdfilename, linenum);
+			continue;
+		}
+
+		/* did configure mark this as dead? */
+		if (strncmp("undef", cp, 5) == 0)
+			continue;
+
+		strlcpy(path, cp, sizeof(path));
+
+		/* third token, entropy rate estimate for this command */
+		if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
+			error("missing entropy estimate, %.100s line %d -- ignored",
+			      cmdfilename, linenum);
+			continue;
+		}
+		est = strtod(cp, &argv);
+
+		/* end of line */
+		if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
+			error("garbage at end of line %d in %.100s -- ignored", linenum,
+				cmdfilename);
+			continue;
+		}
+
+		/* save the command for debug messages */
+		entcmd[cur_cmd].cmdstring = xstrdup(cmd);
+
+		/* split the command args */
+		cp = strtok(cmd, WHITESPACE);
+		arg = 0;
+		argv = NULL;
+		do {
+			char *s = (char*)xmalloc(strlen(cp) + 1);
+			strncpy(s, cp, strlen(cp) + 1);
+			entcmd[cur_cmd].args[arg] = s;
+			arg++;
+		} while ((arg < 5) && (cp = strtok(NULL, WHITESPACE)));
+
+		if (strtok(NULL, WHITESPACE))
+			error("ignored extra command elements (max 5), %.100s line %d",
+			      cmdfilename, linenum);
+
+		/* Copy the command path and rate estimate */
+		entcmd[cur_cmd].path = xstrdup(path);
+		entcmd[cur_cmd].rate = est;
+
+		/* Initialise other values */
+		entcmd[cur_cmd].sticky_badness = 1;
+
+		cur_cmd++;
+
+		/* If we've filled the array, reallocate it twice the size */
+		/* Do this now because even if this we're on the last command,
+		   we need another slot to mark the last entry */
+		if (cur_cmd == num_cmds) {
+			num_cmds *= 2;
+			entcmd = xrealloc(entcmd, num_cmds * sizeof(entropy_source_t));
+		}
+	}
+
+	/* zero the last entry */
+	memset(&entcmd[cur_cmd], '\0', sizeof(entropy_source_t));
+
+	/* trim to size */
+	entropy_sources = xrealloc(entcmd, (cur_cmd+1) * sizeof(entropy_source_t));
+
+	debug("Loaded %d entropy commands from %.100s", cur_cmd, cmdfilename);
+
+	return (cur_cmd >= MIN_ENTROPY_SOURCES);
+}
+
+/*
+ * Write a keyfile at exit
+ */
+void
+prng_seed_cleanup(void *junk)
 {
+	prng_write_seedfile();
+}
+
+/*
+ * Conditionally Seed OpenSSL's random number pool from
+ * syscalls and program output
+ */
+void
+seed_rng(void)
+{
+	mysig_t old_sigchld_handler;
+
+	if (!prng_initialised)
+		fatal("RNG not initialised");
+
+	/* Make sure some other sigchld handler doesn't reap our entropy */
+	/* commands */
+	old_sigchld_handler = mysignal(SIGCHLD, SIG_DFL);
+
+	debug("Seeded RNG with %i bytes from programs", 
+	    (int)stir_from_programs());
+	debug("Seeded RNG with %i bytes from system calls", 
+	    (int)stir_from_system());
+
+	if (!RAND_status())
+		fatal("Not enough entropy in RNG");
+
+	mysignal(SIGCHLD, old_sigchld_handler);
+
+	if (!RAND_status())
+		fatal("Couldn't initialise builtin random number generator -- exiting.");
+}
+
+void
+init_rng(void)
+{
+	int original_euid;
+
+	check_openssl_version();
+
+	original_uid = getuid();
+	original_euid = geteuid();
+
+	/* Read in collection commands */
+	if (!prng_read_commands(SSH_PRNG_COMMAND_FILE))
+		fatal("PRNG initialisation failed -- exiting.");
+
+	/* Set ourselves up to save a seed upon exit */
+	prng_seed_saved = 0;
+
+	/* Give up privs while reading seed file */
+#ifdef SAVED_IDS_WORK_WITH_SETEUID
+	if ((original_uid != original_euid) && (seteuid(original_uid) == -1))
+		fatal("Couldn't give up privileges");
+#else /* SAVED_IDS_WORK_WITH_SETEUID */
 	/*
-	 * OpenSSL version numbers: MNNFFPPS: major minor fix patch status
-	 * We match major, minor, fix and status (not patch)
+	 * Propagate the privileged uid to all of our uids.
+	 * Set the effective uid to the given (unprivileged) uid. 
 	 */
-	if ((SSLeay() ^ OPENSSL_VERSION_NUMBER) & ~0xff0L)
-		fatal("OpenSSL version mismatch. Built against %lx, you "
-		    "have %lx", OPENSSL_VERSION_NUMBER, SSLeay());
+	if (original_uid != original_euid && (setuid(original_euid) == -1 || 
+	    seteuid(original_uid) == -1))
+		fatal("Couldn't give up privileges");
+#endif /* SAVED_IDS_WORK_WITH_SETEUID */
 
-#ifndef OPENSSL_PRNG_ONLY
-	if ((original_uid = getuid()) == -1)
-		fatal("getuid: %s", strerror(errno));
-	if ((original_euid = geteuid()) == -1)
-		fatal("geteuid: %s", strerror(errno));
-#endif
+	prng_read_seedfile();
+
+#ifdef SAVED_IDS_WORK_WITH_SETEUID
+	if ((original_uid != original_euid) && (seteuid(original_euid) == -1))
+		fatal("Couldn't restore privileges");
+#else /* SAVED_IDS_WORK_WITH_SETEUID */
+	/*
+	 * We are unable to restore the real uid to its unprivileged value.
+	 * Propagate the real uid (usually more privileged) to effective uid
+	 * as well.
+	 */
+	if (original_uid != original_euid && (seteuid(original_euid) == -1 || 
+	    setuid(original_uid) == -1))
+		fatal("Couldn't restore privileges");
+#endif /* SAVED_IDS_WORK_WITH_SETEUID */
+
+	fatal_add_cleanup(prng_seed_cleanup, NULL);
+	atexit(prng_write_seedfile);
+
+	prng_initialised = 1;
 }
 
+#endif /* defined(USE_PRNGD) || defined(RANDOM_POOL) */