Import of OpenSSH 4.0p1

[gssapi-openssh.git] / openssh / ssh-rand-helper.c

diff --git a/openssh/ssh-rand-helper.c b/openssh/ssh-rand-helper.c
index 2d8707ee9825e41f4a8bfb6894a17193f7399d98..28c93b6f56cd9889b3a09064458d4b17ad42cff6 100644 (file)
--- a/openssh/ssh-rand-helper.c
+++ b/openssh/ssh-rand-helper.c
@@ -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");
+}