X-Git-Url: http://andersk.mit.edu/gitweb/openssh.git/blobdiff_plain/48c99b2c840180331f14e9ad6d1a13dcdac411ff..27c47c0ad07c3e63270ef33b5f3f7226d4d58582:/entropy.c

diff --git a/entropy.c b/entropy.c
index cecf9e8d..9588f792 100644
--- a/entropy.c
+++ b/entropy.c
@@ -9,11 +9,6 @@
  * 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
@@ -29,11 +24,21 @@
 
 #include "includes.h"
 
-#include "ssh.h"
-#include "xmalloc.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"
+#include "atomicio.h"
+#include "pathnames.h"
+#include "log.h"
 
 RCSID("$Id$");
 
@@ -41,9 +46,6 @@ RCSID("$Id$");
 # define offsetof(type, member) ((size_t) &((type *)0)->member)
 #endif
 
-/* Print lots of detail */
-/* #define DEBUG_ENTROPY */
-
 /* Number of times to pass through command list gathering entropy */
 #define NUM_ENTROPY_RUNS	1
 
@@ -55,90 +57,187 @@ RCSID("$Id$");
 
 #define WHITESPACE " \t\n"
 
-#if defined(EGD_SOCKET) || defined(RANDOM_POOL)
+#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
 
-#ifdef EGD_SOCKET
-/* Collect entropy from EGD */
-void get_random_bytes(unsigned char *buf, int len)
+static void
+check_openssl_version(void) 
 {
-	static int egd_socket = -1;
-	int c;
-	char egd_message[2] = { 0x02, 0x00 };
+	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;
-	int addr_len;
+#endif
+	int addr_len, rval, errors;
+	mysig_t old_sigpipe;
 
 	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");
-	
-	strlcpy(addr.sun_path, EGD_SOCKET, sizeof(addr.sun_path));
-	
-	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));
-	}	
 
+#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 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));
+		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 /* !EGD_SOCKET */
+#else /* !USE_PRNGD */
 #ifdef RANDOM_POOL
 /* Collect entropy from /dev/urandom or pipe */
-void get_random_bytes(unsigned char *buf, int len)
+static int
+get_random_bytes(unsigned char *buf, int len)
 {
-	static int random_pool = -1;
-	int c;
+	int random_pool;
 
+	random_pool = open(RANDOM_POOL, O_RDONLY);
 	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));
+		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);
 	}
-	
-	c = atomicio(read, random_pool, buf, len);
-	if (c <= 0)
-		fatal("Couldn't read from random pool \"%s\": %s", RANDOM_POOL, strerror(errno));
+
+	close(random_pool);
+
+	return(1);
 }
 #endif /* RANDOM_POOL */
-#endif /* EGD_SOCKET */
+#endif /* USE_PRNGD */
 
 /*
  * Seed OpenSSL's random number pool from Kernel random number generator
- * or EGD
+ * or PRNGD/EGD
  */
 void
 seed_rng(void)
 {
-	char buf[32];
-	
+	unsigned char buf[32];
+
 	debug("Seeding random number generator");
-	get_random_bytes(buf, sizeof(buf));
-	RAND_add(buf, sizeof(buf), sizeof(buf));
+
+	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));
 }
 
-#else /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
+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
@@ -148,9 +247,9 @@ seed_rng(void)
 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
 
-static int prng_seed_loaded = 0;
 static int prng_seed_saved = 0;
-static int prng_commands_loaded = 0;
+static int prng_initialised = 0;
+uid_t original_uid;
 
 typedef struct
 {
@@ -178,20 +277,20 @@ 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 
+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);
+	RAND_add(&i, sizeof(i), 0.5);
 	total_entropy_estimate += 0.1;
-	
+
 	i = getppid();
-	RAND_add(&i, sizeof(i), 0.1);
+	RAND_add(&i, sizeof(i), 0.5);
 	total_entropy_estimate += 0.1;
 
 	i = getuid();
@@ -200,13 +299,13 @@ stir_from_system(void)
 	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_clock(0.5);
 	total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
 
 	return(total_entropy_estimate);
 }
 
-double 
+double
 stir_from_programs(void)
 {
 	int i;
@@ -226,21 +325,19 @@ stir_from_programs(void)
 
 				/* 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 */
+				/* 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);
 
-#ifdef DEBUG_ENTROPY
-				debug("Got %0.2f bytes of entropy from '%s'", entropy_estimate, 
+				debug3("Got %0.2f bytes of entropy from '%s'", entropy_estimate,
 					entropy_sources[c].cmdstring);
-#endif
 
 				total_entropy_estimate += entropy_estimate;
 
@@ -250,10 +347,8 @@ stir_from_programs(void)
 				total_entropy_estimate += stir_rusage(RUSAGE_SELF, 0.1);
 				total_entropy_estimate += stir_rusage(RUSAGE_CHILDREN, 0.1);
 			} else {
-#ifdef DEBUG_ENTROPY
-				debug("Command '%s' disabled (badness %d)",
+				debug2("Command '%s' disabled (badness %d)",
 					entropy_sources[c].cmdstring, entropy_sources[c].badness);
-#endif
 
 				if (entropy_sources[c].badness > 0)
 					entropy_sources[c].badness--;
@@ -262,7 +357,7 @@ stir_from_programs(void)
 			c++;
 		}
 	}
-	
+
 	return(total_entropy_estimate);
 }
 
@@ -270,12 +365,12 @@ 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);
 }
 
@@ -284,10 +379,10 @@ 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);
@@ -299,11 +394,11 @@ 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));
+		return(0);
 
-	RAND_add(&ru, sizeof(ru), 0.1);
+	RAND_add(&ru, sizeof(ru), entropy_estimate);
 
 	return(entropy_estimate);
 #else /* _HAVE_GETRUSAGE */
@@ -312,8 +407,7 @@ stir_rusage(int who, double entropy_estimate)
 }
 
 
-static
-int
+static int
 _get_timeval_msec_difference(struct timeval *t1, struct timeval *t2) {
 	int secdiff, usecdiff;
 
@@ -337,13 +431,15 @@ hash_output_from_command(entropy_source_t *src, char *hash)
 	int bytes_read;
 	int total_bytes_read;
 	SHA_CTX sha;
-	
+
+	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));
 
@@ -363,10 +459,10 @@ hash_output_from_command(entropy_source_t *src, char *hash)
 			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));
-			src->badness = src->sticky_badness = 128;
 			_exit(-1);
 		default: /* Parent */
 			break;
@@ -400,49 +496,47 @@ hash_output_from_command(entropy_source_t *src, char *hash)
 
 		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 */
-			bytes_read = read(p[0], buf, sizeof(buf));
+			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;
-			}
-			if (bytes_read) {
+			} else if (bytes_read) {
 				SHA1_Update(&sha, buf, bytes_read);
 				total_bytes_read += bytes_read;
-				RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
-			} else
+			} else {
 				cmd_eof = 1;
-
+			}
 			break;
-
 		case -1:
 		default:
+			/* error */
 			debug("Command '%s': select() failed: %s", src->cmdstring,
 			      strerror(errno));
 			error_abort = 1;
 			break;
-		} /* switch ret */
-
-		RAND_add(&tv, sizeof(&tv), 0.0);
-	} /* while !error_abort && !cmd_eof */
+		}
+	}
 
 	SHA1_Final(hash, &sha);
 
 	close(p[0]);
 
-#ifdef DEBUG_ENTROPY
-	debug("Time elapsed: %d msec", msec_elapsed);
-#endif
-	
+	debug3("Time elapsed: %d msec", msec_elapsed);
+
 	if (waitpid(pid, &status, 0) == -1) {
-	       debug("Couldn't wait for child '%s' completion: %s", src->cmdstring,
+	       error("Couldn't wait for child '%s' completion: %s", src->cmdstring,
 		     strerror(errno));
 		return(0.0);
 	}
@@ -453,7 +547,7 @@ hash_output_from_command(entropy_source_t *src, char *hash)
 		/* closing p[0] on timeout causes the entropy command to
 		 * SIGPIPE. Take whatever output we got, and mark this command
 		 * as slow */
-		debug("Command '%s' timed out", src->cmdstring);
+		debug2("Command '%s' timed out", src->cmdstring);
 		src->sticky_badness *= 2;
 		src->badness = src->sticky_badness;
 		return(total_bytes_read);
@@ -463,13 +557,13 @@ hash_output_from_command(entropy_source_t *src, char *hash)
 		if (WEXITSTATUS(status)==0) {
 			return(total_bytes_read);
 		} else {
-			debug("Command '%s' exit status was %d", src->cmdstring, 
+			debug2("Command '%s' exit status was %d", src->cmdstring,
 				WEXITSTATUS(status));
 			src->badness = src->sticky_badness = 128;
 			return (0.0);
 		}
 	} else if (WIFSIGNALED(status)) {
-		debug("Command '%s' returned on uncaught signal %d !", src->cmdstring, 
+		debug2("Command '%s' returned on uncaught signal %d !", src->cmdstring,
 			status);
 		src->badness = src->sticky_badness = 128;
 		return(0.0);
@@ -488,10 +582,10 @@ prng_check_seedfile(char *filename) {
 	/* 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) {
-		/* Fail on hard errors */
+		/* Give up on hard errors */
 		if (errno != ENOENT)
-			fatal("Couldn't stat random seed file \"%s\": %s", filename,
-				strerror(errno));
+			debug("WARNING: Couldn't stat random seed file \"%s\": %s",
+			   filename, strerror(errno));
 
 		return(0);
 	}
@@ -501,9 +595,11 @@ prng_check_seedfile(char *filename) {
 		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 == getuid()))
-		fatal("PRNG seedfile %.100s must be mode 0600, owned by uid %d",
+	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);
+	}
 
 	return(1);
 }
@@ -518,20 +614,22 @@ prng_write_seedfile(void) {
 	/* Don't bother if we have already saved a seed */
 	if (prng_seed_saved)
 		return;
-	
+
+	setuid(original_uid);
+
 	prng_seed_saved = 1;
-	
-	pw = getpwuid(getuid());
+
+	pw = getpwuid(original_uid);
 	if (pw == NULL)
-		fatal("Couldn't get password entry for current user (%i): %s", 
-			getuid(), strerror(errno));
-				
+		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, 
-		SSH_USER_DIR);
+	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, 
+	snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
 		SSH_PRNG_SEED_FILE);
 
 	debug("writing PRNG seed to file %.100s", filename);
@@ -540,16 +638,17 @@ prng_write_seedfile(void) {
 
 	/* 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)
-		fatal("couldn't access PRNG seedfile %.100s (%.100s)", filename, 
-			strerror(errno));
-	
-	if (atomicio(write, fd, &seed, sizeof(seed)) != sizeof(seed))
-		fatal("problem writing PRNG seedfile %.100s (%.100s)", filename, 
-			 strerror(errno));
 
-	close(fd);
+	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
@@ -558,31 +657,26 @@ prng_read_seedfile(void) {
 	char seed[1024];
 	char filename[1024];
 	struct passwd *pw;
-	
-	pw = getpwuid(getuid());
+
+	pw = getpwuid(original_uid);
 	if (pw == NULL)
-		fatal("Couldn't get password entry for current user (%i): %s", 
-			getuid(), strerror(errno));
-			
-	snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir, 
+		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, creating new");
-		prng_write_seedfile();
-		
-		/* Reseed immediatly */
-		(void)stir_from_system();
-		(void)stir_from_programs();
+		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, 
+		fatal("could not open PRNG seedfile %.100s (%.100s)", filename,
 			strerror(errno));
 
 	if (atomicio(read, fd, &seed, sizeof(seed)) != sizeof(seed)) {
@@ -642,7 +736,7 @@ prng_read_commands(char *cmdfilename)
 			error("bad entropy command, %.100s line %d", cmdfilename,
 			     linenum);
 			continue;
-		}		
+		}
 
 		/* first token, command args (incl. argv[0]) in double quotes */
 		cp = strtok(cp, "\"");
@@ -652,7 +746,7 @@ prng_read_commands(char *cmdfilename)
 			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",
@@ -664,7 +758,7 @@ prng_read_commands(char *cmdfilename)
 		if (strncmp("undef", cp, 5) == 0)
 			continue;
 
-		strlcpy(path, cp, sizeof(path));			
+		strlcpy(path, cp, sizeof(path));
 
 		/* third token, entropy rate estimate for this command */
 		if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
@@ -676,14 +770,14 @@ prng_read_commands(char *cmdfilename)
 
 		/* end of line */
 		if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
-			error("garbage at end of line %d in %.100s -- ignored", linenum, 
+			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;
@@ -694,7 +788,7 @@ prng_read_commands(char *cmdfilename)
 			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);
@@ -723,14 +817,14 @@ prng_read_commands(char *cmdfilename)
 	/* trim to size */
 	entropy_sources = xrealloc(entcmd, (cur_cmd+1) * sizeof(entropy_source_t));
 
-	debug("loaded %d entropy commands from %.100s", cur_cmd, cmdfilename);
+	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)
 {
@@ -744,36 +838,80 @@ prng_seed_cleanup(void *junk)
 void
 seed_rng(void)
 {
-	void *old_sigchld_handler;
-	
-	if (!prng_commands_loaded) {
-		if (!prng_read_commands(SSH_PRNG_COMMAND_FILE))
-			fatal("PRNG initialisation failed -- exiting.");
-		prng_commands_loaded = 1;
-	}
+	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 = signal(SIGCHLD, SIG_DFL);
+	old_sigchld_handler = mysignal(SIGCHLD, SIG_DFL);
 
-	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());
+	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());
 
-	signal(SIGCHLD, old_sigchld_handler);
+	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.");
+}
 
-	if (!prng_seed_loaded)
-	{
-		prng_seed_loaded = 1;
-		prng_seed_saved = 0;		
-		prng_read_seedfile();
-		fatal_add_cleanup(prng_seed_cleanup, NULL);
-		atexit(prng_write_seedfile);
-	}
+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 */
+	/*
+	 * Propagate the privileged uid to all of our uids.
+	 * Set the effective uid to the given (unprivileged) uid. 
+	 */
+	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 */
+
+	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(EGD_SOCKET) || defined(RANDOM_POOL) */
+
+#endif /* defined(USE_PRNGD) || defined(RANDOM_POOL) */