src/veritysetup/veritysetup-generator.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   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 "path-util.h"
  20 #include "proc-cmdline.h"
  21 #include "specifier.h"
  22 #include "string-util.h"
  23 #include "unit-name.h"
  24
  25 #define SYSTEMD_VERITYSETUP_SERVICE "systemd-veritysetup@root.service"
  26
  27 static const char *arg_dest = NULL;
  28 static bool arg_enabled = true;
  29 static char *arg_root_hash = NULL;
  30 static char *arg_data_what = NULL;
  31 static char *arg_hash_what = NULL;
  32
  33 STATIC_DESTRUCTOR_REGISTER(arg_root_hash, freep);
  34 STATIC_DESTRUCTOR_REGISTER(arg_data_what, freep);
  35 STATIC_DESTRUCTOR_REGISTER(arg_hash_what, freep);
  36
  37 static int create_device(void) {
  38         _cleanup_free_ char *u = NULL, *v = NULL, *d = NULL, *e = NULL, *u_escaped = NULL, *v_escaped = NULL, *root_hash_escaped = NULL;
  39         _cleanup_fclose_ FILE *f = NULL;
  40         const char *to;
  41         int r;
  42
  43         /* If all three pieces of information are missing, then verity is turned off */
  44         if (!arg_root_hash && !arg_data_what && !arg_hash_what)
  45                 return 0;
  46
  47         /* if one of them is missing however, the data is simply incomplete and this is an error */
  48         if (!arg_root_hash)
  49                 log_error("Verity information incomplete, root hash unspecified.");
  50         if (!arg_data_what)
  51                 log_error("Verity information incomplete, root data device unspecified.");
  52         if (!arg_hash_what)
  53                 log_error("Verity information incomplete, root hash device unspecified.");
  54
  55         if (!arg_root_hash || !arg_data_what || !arg_hash_what)
  56                 return -EINVAL;
  57
  58         log_debug("Using root verity data device %s,\n"
  59                   "                  hash device %s,\n"
  60                   "                and root hash %s.", arg_data_what, arg_hash_what, arg_root_hash);
  61
  62         u = fstab_node_to_udev_node(arg_data_what);
  63         if (!u)
  64                 return log_oom();
  65         v = fstab_node_to_udev_node(arg_hash_what);
  66         if (!v)
  67                 return log_oom();
  68
  69         u_escaped = specifier_escape(u);
  70         if (!u_escaped)
  71                 return log_oom();
  72         v_escaped = specifier_escape(v);
  73         if (!v_escaped)
  74                 return log_oom();
  75
  76         r = unit_name_from_path(u, ".device", &d);
  77         if (r < 0)
  78                 return log_error_errno(r, "Failed to generate unit name: %m");
  79         r = unit_name_from_path(v, ".device", &e);
  80         if (r < 0)
  81                 return log_error_errno(r, "Failed to generate unit name: %m");
  82
  83         root_hash_escaped = specifier_escape(arg_root_hash);
  84         if (!root_hash_escaped)
  85                 return log_oom();
  86
  87         r = generator_open_unit_file(arg_dest, NULL, SYSTEMD_VERITYSETUP_SERVICE, &f);
  88         if (r < 0)
  89                 return r;
  90
  91         fprintf(f,
  92                 "[Unit]\n"
  93                 "Description=Integrity Protection Setup for %%I\n"
  94                 "Documentation=man:systemd-veritysetup-generator(8) man:systemd-veritysetup@.service(8)\n"
  95                 "SourcePath=/proc/cmdline\n"
  96                 "DefaultDependencies=no\n"
  97                 "Conflicts=umount.target\n"
  98                 "BindsTo=%s %s\n"
  99                 "IgnoreOnIsolate=true\n"
 100                 "After=cryptsetup-pre.target systemd-udevd-kernel.socket %s %s\n"
 101                 "Before=cryptsetup.target umount.target\n"
 102                 "\n[Service]\n"
 103                 "Type=oneshot\n"
 104                 "RemainAfterExit=yes\n"
 105                 "ExecStart=" ROOTLIBEXECDIR "/systemd-veritysetup attach root '%s' '%s' '%s'\n"
 106                 "ExecStop=" ROOTLIBEXECDIR "/systemd-veritysetup detach root\n",
 107                 d, e,
 108                 d, e,
 109                 u_escaped, v_escaped, root_hash_escaped);
 110
 111         r = fflush_and_check(f);
 112         if (r < 0)
 113                 return log_error_errno(r, "Failed to write file unit "SYSTEMD_VERITYSETUP_SERVICE": %m");
 114
 115         to = strjoina(arg_dest, "/cryptsetup.target.requires/" SYSTEMD_VERITYSETUP_SERVICE);
 116
 117         (void) mkdir_parents(to, 0755);
 118         if (symlink("../" SYSTEMD_VERITYSETUP_SERVICE, to) < 0)
 119                 return log_error_errno(errno, "Failed to create symlink %s: %m", to);
 120
 121         return 0;
 122 }
 123
 124 static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
 125         int r;
 126
 127         if (proc_cmdline_key_streq(key, "systemd.verity")) {
 128
 129                 r = value ? parse_boolean(value) : 1;
 130                 if (r < 0)
 131                         log_warning("Failed to parse verity= kernel command line switch %s. Ignoring.", value);
 132                 else
 133                         arg_enabled = r;
 134
 135         } else if (proc_cmdline_key_streq(key, "roothash")) {
 136
 137                 if (proc_cmdline_value_missing(key, value))
 138                         return 0;
 139
 140                 r = free_and_strdup(&arg_root_hash, value);
 141                 if (r < 0)
 142                         return log_oom();
 143
 144         } else if (proc_cmdline_key_streq(key, "systemd.verity_root_data")) {
 145
 146                 if (proc_cmdline_value_missing(key, value))
 147                         return 0;
 148
 149                 r = free_and_strdup(&arg_data_what, value);
 150                 if (r < 0)
 151                         return log_oom();
 152
 153         } else if (proc_cmdline_key_streq(key, "systemd.verity_root_hash")) {
 154
 155                 if (proc_cmdline_value_missing(key, value))
 156                         return 0;
 157
 158                 r = free_and_strdup(&arg_hash_what, value);
 159                 if (r < 0)
 160                         return log_oom();
 161         }
 162
 163         return 0;
 164 }
 165
 166 static int determine_devices(void) {
 167         _cleanup_free_ void *m = NULL;
 168         sd_id128_t root_uuid, verity_uuid;
 169         char ids[ID128_UUID_STRING_MAX];
 170         size_t l;
 171         int r;
 172
 173         /* Try to automatically derive the root data and hash device paths from the root hash */
 174
 175         if (!arg_root_hash)
 176                 return 0;
 177
 178         if (arg_data_what && arg_hash_what)
 179                 return 0;
 180
 181         r = unhexmem(arg_root_hash, strlen(arg_root_hash), &m, &l);
 182         if (r < 0)
 183                 return log_error_errno(r, "Failed to parse root hash: %s", arg_root_hash);
 184         if (l < sizeof(sd_id128_t)) {
 185                 log_debug("Root hash is shorter than 128 bits (32 characters), ignoring for discovering verity partition.");
 186                 return 0;
 187         }
 188
 189         if (!arg_data_what) {
 190                 memcpy(&root_uuid, m, sizeof(root_uuid));
 191
 192                 arg_data_what = path_join("/dev/disk/by-partuuid", id128_to_uuid_string(root_uuid, ids));
 193                 if (!arg_data_what)
 194                         return log_oom();
 195         }
 196
 197         if (!arg_hash_what) {
 198                 memcpy(&verity_uuid, (uint8_t*) m + l - sizeof(verity_uuid), sizeof(verity_uuid));
 199
 200                 arg_hash_what = path_join("/dev/disk/by-partuuid", id128_to_uuid_string(verity_uuid, ids));
 201                 if (!arg_hash_what)
 202                         return log_oom();
 203         }
 204
 205         return 1;
 206 }
 207
 208 static int run(const char *dest, const char *dest_early, const char *dest_late) {
 209         int r;
 210
 211         assert_se(arg_dest = dest);
 212
 213         r = proc_cmdline_parse(parse_proc_cmdline_item, NULL, PROC_CMDLINE_STRIP_RD_PREFIX);
 214         if (r < 0)
 215                 return log_warning_errno(r, "Failed to parse kernel command line: %m");
 216
 217         /* For now we only support the root device on verity. Later on we might want to add support for /etc/veritytab
 218          * or similar to define additional mappings */
 219
 220         if (!arg_enabled)
 221                 return 0;
 222
 223         r = determine_devices();
 224         if (r < 0)
 225                 return r;
 226
 227         return create_device();
 228 }
 229
 230 DEFINE_MAIN_GENERATOR_FUNCTION(run);