]> andersk Git - openssh.git/blobdiff - entropy.c
- (djm) Convert mandoc manpages to man automatically. Patch from Mark D.
[openssh.git] / entropy.c
index 0b86fdf0e0cb376d404708f4d5e1998f3d3f1b2e..44440d974cb6830a462ad34dba4ce1cf13a6d3b6 100644 (file)
--- 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
 
 #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
 
@@ -62,90 +64,180 @@ RCSID("$Id$");
 # define RUSAGE_CHILDREN 0
 #endif
 
-#if defined(EGD_SOCKET) || defined(RANDOM_POOL)
+#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)
+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)
+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);
        }
-       
-       c = atomicio(read, random_pool, buf, len);
-       if (c <= 0)
-               fatal("Couldn't read from random pool \"%s\": %s", RANDOM_POOL, strerror(errno));
+
+       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 /* 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
@@ -155,9 +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
 {
@@ -185,18 +277,18 @@ 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), 0.5);
        total_entropy_estimate += 0.1;
-       
+
        i = getppid();
        RAND_add(&i, sizeof(i), 0.5);
        total_entropy_estimate += 0.1;
@@ -213,7 +305,7 @@ stir_from_system(void)
        return(total_entropy_estimate);
 }
 
-double 
+double
 stir_from_programs(void)
 {
        int i;
@@ -233,21 +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;
 
@@ -257,10 +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--;
@@ -269,7 +357,7 @@ stir_from_programs(void)
                        c++;
                }
        }
-       
+
        return(total_entropy_estimate);
 }
 
@@ -277,12 +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);
 }
 
@@ -291,10 +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);
@@ -306,7 +394,7 @@ stir_rusage(int who, double entropy_estimate)
 {
 #ifdef HAVE_GETRUSAGE
        struct rusage ru;
-       
+
        if (getrusage(who, &ru) == -1)
                return(0);
 
@@ -319,8 +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;
 
@@ -344,13 +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));
 
@@ -370,10 +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;
@@ -407,49 +496,45 @@ 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));
+                       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);
        }
@@ -460,7 +545,7 @@ 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);
@@ -470,13 +555,13 @@ 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);
@@ -495,10 +580,10 @@ 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);
        }
@@ -508,9 +593,11 @@ 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);
 }
@@ -525,20 +612,22 @@ 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);
@@ -547,16 +636,17 @@ 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
@@ -565,31 +655,26 @@ 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)) {
@@ -649,7 +734,7 @@ 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, "\"");
@@ -659,7 +744,7 @@ 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",
@@ -671,7 +756,7 @@ 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) {
@@ -683,14 +768,14 @@ 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;
@@ -701,7 +786,7 @@ 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);
@@ -730,14 +815,14 @@ 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)
 {
@@ -751,36 +836,80 @@ 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) */
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