src/veritysetup/veritysetup-generator.c

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