src/veritysetup/veritysetup-generator.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   Copyright 2016 Lennart Poettering
   4 ***/
   5
   6 #include <errno.h>
   7 #include <stdbool.h>
   8 #include <stdlib.h>
   9 #include <sys/stat.h>
  10 #include <unistd.h>
  11
  12 #include "alloc-util.h"
  13 #include "fd-util.h"
  14 #include "fileio.h"
  15 #include "fstab-util.h"
  16 #include "generator.h"
  17 #include "hexdecoct.h"
  18 #include "id128-util.h"
  19 #include "mkdir.h"
  20 #include "parse-util.h"
  21 #include "proc-cmdline.h"
  22 #include "specifier.h"
  23 #include "string-util.h"
  24 #include "unit-name.h"
  25
  26 #define SYSTEMD_VERITYSETUP_SERVICE "systemd-veritysetup@root.service"
  27
  28 static char *arg_dest = NULL;
  29 static bool arg_enabled = true;
  30 static char *arg_root_hash = NULL;
  31 static char *arg_data_what = NULL;
  32 static char *arg_hash_what = NULL;
  33
  34 static int create_device(void) {
  35         _cleanup_free_ char *u = NULL, *v = NULL, *d = NULL, *e = NULL, *u_escaped = NULL, *v_escaped = NULL, *root_hash_escaped = NULL;
  36         _cleanup_fclose_ FILE *f = NULL;
  37         const char *to;
  38         int r;
  39
  40         /* If all three pieces of information are missing, then verity is turned off */
  41         if (!arg_root_hash && !arg_data_what && !arg_hash_what)
  42                 return 0;
  43
  44         /* if one of them is missing however, the data is simply incomplete and this is an error */
  45         if (!arg_root_hash)
  46                 log_error("Verity information incomplete, root hash unspecified.");
  47         if (!arg_data_what)
  48                 log_error("Verity information incomplete, root data device unspecified.");
  49         if (!arg_hash_what)
  50                 log_error("Verity information incomplete, root hash device unspecified.");
  51
  52         if (!arg_root_hash || !arg_data_what || !arg_hash_what)
  53                 return -EINVAL;
  54
  55         log_debug("Using root verity data device %s,\n"
  56                   "                  hash device %s,\n"
  57                   "                and root hash %s.", arg_data_what, arg_hash_what, arg_root_hash);
  58
  59         u = fstab_node_to_udev_node(arg_data_what);
  60         if (!u)
  61                 return log_oom();
  62         v = fstab_node_to_udev_node(arg_hash_what);
  63         if (!v)
  64                 return log_oom();
  65
  66         u_escaped = specifier_escape(u);
  67         if (!u_escaped)
  68                 return log_oom();
  69         v_escaped = specifier_escape(v);
  70         if (!v_escaped)
  71                 return log_oom();
  72
  73         r = unit_name_from_path(u, ".device", &d);
  74         if (r < 0)
  75                 return log_error_errno(r, "Failed to generate unit name: %m");
  76         r = unit_name_from_path(v, ".device", &e);
  77         if (r < 0)
  78                 return log_error_errno(r, "Failed to generate unit name: %m");
  79
  80         root_hash_escaped = specifier_escape(arg_root_hash);
  81         if (!root_hash_escaped)
  82                 return log_oom();
  83
  84         r = generator_open_unit_file(arg_dest, NULL, SYSTEMD_VERITYSETUP_SERVICE, &f);
  85         if (r < 0)
  86                 return r;
  87
  88         fprintf(f,
  89                 "[Unit]\n"
  90                 "Description=Integrity Protection Setup for %%I\n"
  91                 "Documentation=man:systemd-veritysetup-generator(8) man:systemd-veritysetup@.service(8)\n"
  92                 "SourcePath=/proc/cmdline\n"
  93                 "DefaultDependencies=no\n"
  94                 "Conflicts=umount.target\n"
  95                 "BindsTo=%s %s\n"
  96                 "IgnoreOnIsolate=true\n"
  97                 "After=cryptsetup-pre.target %s %s\n"
  98                 "Before=cryptsetup.target umount.target\n"
  99                 "\n[Service]\n"
 100                 "Type=oneshot\n"
 101                 "RemainAfterExit=yes\n"
 102                 "ExecStart=" ROOTLIBEXECDIR "/systemd-veritysetup attach root '%s' '%s' '%s'\n"
 103                 "ExecStop=" ROOTLIBEXECDIR "/systemd-veritysetup detach root\n",
 104                 d, e,
 105                 d, e,
 106                 u_escaped, v_escaped, root_hash_escaped);
 107
 108         r = fflush_and_check(f);
 109         if (r < 0)
 110                 return log_error_errno(r, "Failed to write file unit "SYSTEMD_VERITYSETUP_SERVICE": %m");
 111
 112         to = strjoina(arg_dest, "/cryptsetup.target.requires/" SYSTEMD_VERITYSETUP_SERVICE);
 113
 114         (void) mkdir_parents(to, 0755);
 115         if (symlink("../" SYSTEMD_VERITYSETUP_SERVICE, to) < 0)
 116                 return log_error_errno(errno, "Failed to create symlink %s: %m", to);
 117
 118         return 0;
 119 }
 120
 121 static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
 122         int r;
 123
 124         if (streq(key, "systemd.verity")) {
 125
 126                 r = value ? parse_boolean(value) : 1;
 127                 if (r < 0)
 128                         log_warning("Failed to parse verity= kernel command line switch %s. Ignoring.", value);
 129                 else
 130                         arg_enabled = r;
 131
 132         } else if (streq(key, "roothash")) {
 133
 134                 if (proc_cmdline_value_missing(key, value))
 135                         return 0;
 136
 137                 r = free_and_strdup(&arg_root_hash, value);
 138                 if (r < 0)
 139                         return log_oom();
 140
 141         } else if (streq(key, "systemd.verity_root_data")) {
 142
 143                 if (proc_cmdline_value_missing(key, value))
 144                         return 0;
 145
 146                 r = free_and_strdup(&arg_data_what, value);
 147                 if (r < 0)
 148                         return log_oom();
 149
 150         } else if (streq(key, "systemd.verity_root_hash")) {
 151
 152                 if (proc_cmdline_value_missing(key, value))
 153                         return 0;
 154
 155                 r = free_and_strdup(&arg_hash_what, value);
 156                 if (r < 0)
 157                         return log_oom();
 158         }
 159
 160         return 0;
 161 }
 162
 163 static int determine_devices(void) {
 164         _cleanup_free_ void *m = NULL;
 165         sd_id128_t root_uuid, verity_uuid;
 166         char ids[37];
 167         size_t l;
 168         int r;
 169
 170         /* Try to automatically derive the root data and hash device paths from the root hash */
 171
 172         if (!arg_root_hash)
 173                 return 0;
 174
 175         if (arg_data_what && arg_hash_what)
 176                 return 0;
 177
 178         r = unhexmem(arg_root_hash, strlen(arg_root_hash), &m, &l);
 179         if (r < 0)
 180                 return log_error_errno(r, "Failed to parse root hash: %s", arg_root_hash);
 181         if (l < sizeof(sd_id128_t)) {
 182                 log_debug("Root hash is shorter than 128 bits (32 characters), ignoring for discovering verity partition.");
 183                 return 0;
 184         }
 185
 186         if (!arg_data_what) {
 187                 memcpy(&root_uuid, m, sizeof(root_uuid));
 188
 189                 arg_data_what = strjoin("/dev/disk/by-partuuid/", id128_to_uuid_string(root_uuid, ids));
 190                 if (!arg_data_what)
 191                         return log_oom();
 192         }
 193
 194         if (!arg_hash_what) {
 195                 memcpy(&verity_uuid, (uint8_t*) m + l - sizeof(verity_uuid), sizeof(verity_uuid));
 196
 197                 arg_hash_what = strjoin("/dev/disk/by-partuuid/", id128_to_uuid_string(verity_uuid, ids));
 198                 if (!arg_hash_what)
 199                         return log_oom();
 200         }
 201
 202         return 1;
 203 }
 204
 205 int main(int argc, char *argv[]) {
 206         int r;
 207
 208         if (argc > 1 && argc != 4) {
 209                 log_error("This program takes three or no arguments.");
 210                 return EXIT_FAILURE;
 211         }
 212
 213         if (argc > 1)
 214                 arg_dest = argv[1];
 215
 216         log_set_prohibit_ipc(true);
 217         log_set_target(LOG_TARGET_AUTO);
 218         log_parse_environment();
 219         log_open();
 220
 221         umask(0022);
 222
 223         r = proc_cmdline_parse(parse_proc_cmdline_item, NULL, PROC_CMDLINE_STRIP_RD_PREFIX);
 224         if (r < 0) {
 225                 log_warning_errno(r, "Failed to parse kernel command line: %m");
 226                 goto finish;
 227         }
 228
 229         /* For now we only support the root device on verity. Later on we might want to add support for /etc/veritytab
 230          * or similar to define additional mappings */
 231
 232         if (!arg_enabled) {
 233                 r = 0;
 234                 goto finish;
 235         }
 236
 237         r = determine_devices();
 238         if (r < 0)
 239                 goto finish;
 240
 241         r = create_device();
 242         if (r < 0)
 243                 goto finish;
 244
 245         r = 0;
 246
 247 finish:
 248         free(arg_root_hash);
 249         free(arg_data_what);
 250         free(arg_hash_what);
 251
 252         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 253 }