random-seed: add missing random-seed.c file

[elogind.git] / src / random-seed.c

diff --git a/src/random-seed.c b/src/random-seed.c
new file mode 100644 (file)
index 0000000..91aa6c6
--- /dev/null
+++ b/src/random-seed.c
@@ -0,0 +1,112 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#include "log.h"
+#include "util.h"
+
+int main(int argc, char *argv[]) {
+        int seed_fd = -1, random_fd = -1;
+        int ret = 1;
+        uint8_t buf[512];
+        ssize_t r;
+
+        if (argc != 2) {
+                log_error("This program requires one argument.");
+                return 1;
+        }
+
+        log_parse_environment();
+
+        /* When we load the seed we read it and write it to the device
+         * and then immediately update the saved seed with new data,
+         * to make sure the next boot gets seeded differently. */
+
+        if (streq(argv[1], "load")) {
+
+                if ((seed_fd = open(RANDOM_SEED, O_RDWR|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600)) < 0) {
+                        if ((seed_fd = open(RANDOM_SEED, O_RDONLY|O_CLOEXEC|O_NOCTTY)) < 0) {
+                                log_error("Failed to open random seed: %m");
+                                goto finish;
+                        }
+                }
+
+                if ((random_fd = open("/dev/urandom", O_RDWR|O_CLOEXEC|O_NOCTTY, 0600)) < 0) {
+                        if ((random_fd = open("/dev/urandom", O_WRONLY|O_CLOEXEC|O_NOCTTY, 0600)) < 0) {
+                                log_error("Failed to open /dev/urandom: %m");
+                                goto finish;
+                        }
+                }
+
+                if ((r = loop_read(seed_fd, buf, sizeof(buf), false)) != sizeof(buf))
+                        log_error("Failed to read seed file: %s", r < 0 ? strerror(errno) : "EOF");
+                else {
+                        lseek(seed_fd, 0, SEEK_SET);
+
+                        if ((r = loop_write(random_fd, buf, sizeof(buf), false)) != sizeof(buf))
+                                log_error("Failed to write seed to /dev/random: %s", r < 0 ? strerror(errno) : "short write");
+                }
+
+        } else if (streq(argv[1], "save")) {
+
+                if ((seed_fd = open(RANDOM_SEED, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600)) < 0) {
+                        log_error("Failed to open random seed: %m");
+                        goto finish;
+                }
+
+                if ((random_fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY)) < 0) {
+                        log_error("Failed to open /dev/urandom: %m");
+                        goto finish;
+                }
+        } else {
+                log_error("Unknown verb %s.", argv[1]);
+                goto finish;
+        }
+
+        /* This is just a safety measure. Given that we are root and
+         * most likely created the file ourselves the mode and owner
+         * should be correct anyway. */
+        fchmod(seed_fd, 0600);
+        fchown(seed_fd, 0, 0);
+
+        if ((r = loop_read(random_fd, buf, sizeof(buf), false)) != sizeof(buf))
+                log_error("Failed to read new seed from /dev/urandom: %s", r < 0 ? strerror(errno) : "EOF");
+        else {
+                if ((r = loop_write(seed_fd, buf, sizeof(buf), false)) != sizeof(buf))
+                        log_error("Failed to write new random seed file: %s", r < 0 ? strerror(errno) : "short write");
+        }
+
+        ret = 0;
+
+finish:
+        if (random_fd >= 0)
+                close_nointr_nofail(random_fd);
+
+        if (seed_fd >= 0)
+                close_nointr_nofail(seed_fd);
+
+        return ret;
+}