verity: add support for setting up verity-protected root disks in the initrd

This adds a generator and a small service that will look for "roothash="
on the kernel command line and use it for setting up a very partition
for the root device.

This provides similar functionality to nspawn's existing --roothash=
switch.

1 files changed, 253 insertions, 0 deletions

diff --git a/src/veritysetup/veritysetup-generator.c b/src/veritysetup/veritysetup-generator.c
new file mode 100644
index 0000000000..519ac050f9
--- /dev/null
+++ b/src/veritysetup/veritysetup-generator.c
@@ -0,0 +1,253 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2016 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 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
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fstab-util.h"
+#include "hexdecoct.h"
+#include "id128-util.h"
+#include "mkdir.h"
+#include "parse-util.h"
+#include "proc-cmdline.h"
+#include "string-util.h"
+#include "unit-name.h"
+
+static char *arg_dest = NULL;
+static bool arg_enabled = true;
+static char *arg_root_hash = NULL;
+static char *arg_data_what = NULL;
+static char *arg_hash_what = NULL;
+
+static int create_device(void) {
+        _cleanup_free_ char *u = NULL, *v = NULL, *d = NULL, *e = NULL;
+        _cleanup_fclose_ FILE *f = NULL;
+        const char *p, *to;
+        int r;
+
+        /* If all three pieces of information are missing, then verity is turned off */
+        if (!arg_root_hash && !arg_data_what && !arg_hash_what)
+                return 0;
+
+        /* if one of them is missing however, the data is simply incomplete and this is an error */
+        if (!arg_root_hash)
+                log_error("Verity information incomplete, root hash unspecified.");
+        if (!arg_data_what)
+                log_error("Verity information incomplete, root data device unspecified.");
+        if (!arg_hash_what)
+                log_error("Verity information incomplete, root hash device unspecified.");
+
+        if (!arg_root_hash || !arg_data_what || !arg_hash_what)
+                return -EINVAL;
+
+        log_debug("Using root verity data device %s,\n"
+                  "                  hash device %s,\n"
+                  "                and root hash %s.", arg_data_what, arg_hash_what, arg_root_hash);
+
+        p = strjoina(arg_dest, "/systemd-veritysetup@root.service");
+
+        u = fstab_node_to_udev_node(arg_data_what);
+        if (!u)
+                return log_oom();
+        v = fstab_node_to_udev_node(arg_hash_what);
+        if (!v)
+                return log_oom();
+
+        r = unit_name_from_path(u, ".device", &d);
+        if (r < 0)
+                return log_error_errno(r, "Failed to to generate unit name: %m");
+        r = unit_name_from_path(v, ".device", &e);
+        if (r < 0)
+                return log_error_errno(r, "Failed to to generate unit name: %m");
+
+        f = fopen(p, "wxe");
+        if (!f)
+                return log_error_errno(errno, "Failed to create unit file %s: %m", p);
+
+        fprintf(f,
+                "# Automatically generated by systemd-veritysetup-generator\n\n"
+                "[Unit]\n"
+                "Description=Integrity Protection Setup for %%I\n"
+                "Documentation=man:systemd-veritysetup-generator(8) man:systemd-veritysetup@.service(8)\n"
+                "SourcePath=/proc/cmdline\n"
+                "DefaultDependencies=no\n"
+                "Conflicts=umount.target\n"
+                "BindsTo=%s %s\n"
+                "IgnoreOnIsolate=true\n"
+                "After=cryptsetup-pre.target %s %s\n"
+                "Before=cryptsetup.target umount.target\n"
+                "\n[Service]\n"
+                "Type=oneshot\n"
+                "RemainAfterExit=yes\n"
+                "ExecStart=" ROOTLIBEXECDIR "/systemd-veritysetup attach root '%s' '%s' '%s'\n"
+                "ExecStop=" ROOTLIBEXECDIR "/systemd-veritysetup detach root\n",
+                d, e,
+                d, e,
+                u, v, arg_root_hash);
+
+        r = fflush_and_check(f);
+        if (r < 0)
+                return log_error_errno(r, "Failed to write file %s: %m", p);
+
+        to = strjoina(arg_dest, "/cryptsetup.target.requires/systemd-veritysetup@root.service");
+
+        (void) mkdir_parents(to, 0755);
+        if (symlink("../systemd-veritysetup@root.service", to) < 0)
+                return log_error_errno(errno, "Failed to create symlink %s: %m", to);
+
+        return 0;
+}
+
+static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
+        int r;
+
+        if (streq(key, "systemd.verity")) {
+
+                r = value ? parse_boolean(value) : 1;
+                if (r < 0)
+                        log_warning("Failed to parse verity= kernel command line switch %s. Ignoring.", value);
+                else
+                        arg_enabled = r;
+
+        } else if (streq(key, "roothash")) {
+
+                if (proc_cmdline_value_missing(key, value))
+                        return 0;
+
+                r = free_and_strdup(&arg_root_hash, value);
+                if (r < 0)
+                        return log_oom();
+
+        } else if (streq(key, "systemd.verity_root_data")) {
+
+                if (proc_cmdline_value_missing(key, value))
+                        return 0;
+
+                r = free_and_strdup(&arg_data_what, value);
+                if (r < 0)
+                        return log_oom();
+
+        } else if (streq(key, "systemd.verity_root_hash")) {
+
+                if (proc_cmdline_value_missing(key, value))
+                        return 0;
+
+                r = free_and_strdup(&arg_hash_what, value);
+                if (r < 0)
+                        return log_oom();
+        }
+
+        return 0;
+}
+
+static int determine_devices(void) {
+        _cleanup_free_ void *m = NULL;
+        sd_id128_t root_uuid, verity_uuid;
+        char ids[37];
+        size_t l;
+        int r;
+
+        /* Try to automatically derive the root data and hash device paths from the root hash */
+
+        if (!arg_root_hash)
+                return 0;
+
+        if (arg_data_what && arg_hash_what)
+                return 0;
+
+        r = unhexmem(arg_root_hash, strlen(arg_root_hash), &m, &l);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse root hash: %s", arg_root_hash);
+        if (l < sizeof(sd_id128_t)) {
+                log_debug("Root hash is shorter than 128 bits (32 characters), ignoring for discovering verity partition.");
+                return 0;
+        }
+
+        if (!arg_data_what) {
+                memcpy(&root_uuid, m, sizeof(root_uuid));
+
+                arg_data_what = strjoin("/dev/disk/by-partuuid/", id128_to_uuid_string(root_uuid, ids));
+                if (!arg_data_what)
+                        return log_oom();
+        }
+
+        if (!arg_hash_what) {
+                memcpy(&verity_uuid, (uint8_t*) m + l - sizeof(verity_uuid), sizeof(verity_uuid));
+
+                arg_hash_what = strjoin("/dev/disk/by-partuuid/", id128_to_uuid_string(verity_uuid, ids));
+                if (!arg_hash_what)
+                        return log_oom();
+        }
+
+        return 1;
+}
+
+int main(int argc, char *argv[]) {
+        int r;
+
+        if (argc > 1 && argc != 4) {
+                log_error("This program takes three or no arguments.");
+                return EXIT_FAILURE;
+        }
+
+        if (argc > 1)
+                arg_dest = argv[1];
+
+        log_set_target(LOG_TARGET_SAFE);
+        log_parse_environment();
+        log_open();
+
+        umask(0022);
+
+        r = proc_cmdline_parse(parse_proc_cmdline_item, NULL, PROC_CMDLINE_STRIP_RD_PREFIX);
+        if (r < 0) {
+                log_warning_errno(r, "Failed to parse kernel command line: %m");
+                goto finish;
+        }
+
+        /* For now we only support the root device on verity. Later on we might want to add support for /etc/veritytab
+         * or similar to define additional mappings */
+
+        if (!arg_enabled) {
+                r = 0;
+                goto finish;
+        }
+
+        r = determine_devices();
+        if (r < 0)
+                goto finish;
+
+        r = create_device();
+        if (r < 0)
+                goto finish;
+
+        r = 0;
+
+finish:
+        free(arg_root_hash);
+        free(arg_data_what);
+        free(arg_hash_what);
+
+        return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
+}