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