1 files changed, 68 insertions, 25 deletions

diff --git a/ssh-rand-helper.c b/ssh-rand-helper.c
index 86af3893d..d7d8d0f3b 100644
--- a/ssh-rand-helper.c
+++ b/ssh-rand-helper.c
@@ -39,7 +39,7 @@
 #include "pathnames.h"
 #include "log.h"
 
-RCSID("$Id: ssh-rand-helper.c,v 1.18 2004/07/17 04:07:42 dtucker Exp $");
+RCSID("$Id: ssh-rand-helper.c,v 1.23 2005/02/16 02:32:30 dtucker Exp $");
 
 /* Number of bytes we write out */
 #define OUTPUT_SEED_SIZE        48
@@ -209,6 +209,22 @@ done:
         return rval;
 }
 
+static int
+seed_from_prngd(unsigned char *buf, size_t bytes)
+{
+#ifdef PRNGD_PORT
+        debug("trying egd/prngd port %d", PRNGD_PORT);
+        if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
+                return 0;
+#endif
+#ifdef PRNGD_SOCKET
+        debug("trying egd/prngd socket %s", PRNGD_SOCKET);
+        if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
+                return 0;
+#endif
+        return -1;
+}
+
 double
 stir_gettimeofday(double entropy_estimate)
 {
@@ -534,10 +550,11 @@ prng_check_seedfile(char *filename)
 void
 prng_write_seedfile(void)
 {
-        int fd;
+        int fd, save_errno;
         unsigned char seed[SEED_FILE_SIZE];
-        char filename[MAXPATHLEN];
+        char filename[MAXPATHLEN], tmpseed[MAXPATHLEN];
         struct passwd *pw;
+        mode_t old_umask;
 
         pw = getpwuid(getuid());
         if (pw == NULL)
@@ -552,7 +569,10 @@ prng_write_seedfile(void)
         snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
             SSH_PRNG_SEED_FILE);
 
-        debug("writing PRNG seed to file %.100s", filename);
+        strlcpy(tmpseed, filename, sizeof(tmpseed));
+        if (strlcat(tmpseed, ".XXXXXXXXXX", sizeof(tmpseed)) >=
+            sizeof(tmpseed))
+                fatal("PRNG seed filename too long");
 
         if (RAND_bytes(seed, sizeof(seed)) <= 0)
                 fatal("PRNG seed extraction failed");
@@ -560,15 +580,31 @@ 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) {
-                debug("WARNING: couldn't access PRNG seedfile %.100s "
-                    "(%.100s)", filename, strerror(errno));
+        old_umask = umask(0177);
+
+        if ((fd = mkstemp(tmpseed)) == -1) {
+                debug("WARNING: couldn't make temporary PRNG seedfile %.100s "
+                    "(%.100s)", tmpseed, strerror(errno));
         } else {
-                if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed))
+                debug("writing PRNG seed to file %.100s", tmpseed);
+                if (atomicio(vwrite, fd, &seed, sizeof(seed)) < sizeof(seed)) {
+                        save_errno = errno;
+                        close(fd);
+                        unlink(tmpseed);
                         fatal("problem writing PRNG seedfile %.100s "
-                            "(%.100s)", filename, strerror(errno));
+                            "(%.100s)", filename, strerror(save_errno));
+                }
                 close(fd);
+                debug("moving temporary PRNG seed to file %.100s", filename);
+                if (rename(tmpseed, filename) == -1) {
+                        save_errno = errno;
+                        unlink(tmpseed);
+                        fatal("problem renaming PRNG seedfile from %.100s "
+                            "to %.100s (%.100s)", tmpseed, filename, 
+                            strerror(save_errno));
+                }
         }
+        umask(old_umask);
 }
 
 void
@@ -747,7 +783,7 @@ usage(void)
         fprintf(stderr, "Usage: %s [options]\n", __progname);
         fprintf(stderr, "  -v          Verbose; display verbose debugging messages.\n");
         fprintf(stderr, "              Multiple -v increases verbosity.\n");
-        fprintf(stderr, "  -x          Force output in hexidecimal (for debugging)\n");
+        fprintf(stderr, "  -x          Force output in hexadecimal (for debugging)\n");
         fprintf(stderr, "  -X          Force output in binary\n");
         fprintf(stderr, "  -b bytes    Number of bytes to output (default %d)\n",
             OUTPUT_SEED_SIZE);
@@ -815,21 +851,16 @@ main(int argc, char **argv)
         debug("Seeded RNG with %i bytes from system calls",
             (int)stir_from_system());
 
-#ifdef PRNGD_PORT
-        if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == -1)
-                fatal("Entropy collection failed");
-        RAND_add(buf, bytes, bytes);
-#elif defined(PRNGD_SOCKET)
-        if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == -1)
-                fatal("Entropy collection failed");
-        RAND_add(buf, bytes, bytes);
-#else
-        /* Read in collection commands */
-        if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
-                fatal("PRNG initialisation failed -- exiting.");
-        debug("Seeded RNG with %i bytes from programs",
-            (int)stir_from_programs());
-#endif
+        /* try prngd, fall back to commands if prngd fails or not configured */
+        if (seed_from_prngd(buf, bytes) == 0) {
+                RAND_add(buf, bytes, bytes);
+        } else {
+                /* Read in collection commands */
+                if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1)
+                        fatal("PRNG initialisation failed -- exiting.");
+                debug("Seeded RNG with %i bytes from programs",
+                    (int)stir_from_programs());
+        }
 
 #ifdef USE_SEED_FILES
         prng_write_seedfile();
@@ -857,3 +888,15 @@ main(int argc, char **argv)
 
         return ret == bytes ? 0 : 1;
 }
+
+/*
+ * We may attempt to re-seed during mkstemp if we are using the one in the
+ * compat library (via mkstemp -> _gettemp -> arc4random -> seed_rng) so we
+ * need our own seed_rng().  We must also check that we have enough entropy.
+ */
+void
+seed_rng(void)
+{
+        if (!RAND_status())
+                fatal("Not enough entropy in RNG");
+}