src/journal/journal-authenticate.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2012 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <fcntl.h>
  23 #include <sys/mman.h>
  24
  25 #include "journal-def.h"
  26 #include "journal-file.h"
  27 #include "journal-authenticate.h"
  28 #include "fsprg.h"
  29
  30 static uint64_t journal_file_tag_seqnum(JournalFile *f) {
  31         uint64_t r;
  32
  33         assert(f);
  34
  35         r = le64toh(f->header->n_tags) + 1;
  36         f->header->n_tags = htole64(r);
  37
  38         return r;
  39 }
  40
  41 int journal_file_append_tag(JournalFile *f) {
  42         Object *o;
  43         uint64_t p;
  44         int r;
  45
  46         assert(f);
  47
  48         if (!f->authenticate)
  49                 return 0;
  50
  51         if (!f->hmac_running)
  52                 return 0;
  53
  54         log_debug("Writing tag for epoch %llu\n", (unsigned long long) FSPRG_GetEpoch(f->fsprg_state));
  55
  56         assert(f->hmac);
  57
  58         r = journal_file_append_object(f, OBJECT_TAG, sizeof(struct TagObject), &o, &p);
  59         if (r < 0)
  60                 return r;
  61
  62         o->tag.seqnum = htole64(journal_file_tag_seqnum(f));
  63         o->tag.epoch = htole64(FSPRG_GetEpoch(f->fsprg_state));
  64
  65         /* Add the tag object itself, so that we can protect its
  66          * header. This will exclude the actual hash value in it */
  67         r = journal_file_hmac_put_object(f, OBJECT_TAG, p);
  68         if (r < 0)
  69                 return r;
  70
  71         /* Get the HMAC tag and store it in the object */
  72         memcpy(o->tag.tag, gcry_md_read(f->hmac, 0), TAG_LENGTH);
  73         f->hmac_running = false;
  74
  75         return 0;
  76 }
  77
  78 int journal_file_hmac_start(JournalFile *f) {
  79         uint8_t key[256 / 8]; /* Let's pass 256 bit from FSPRG to HMAC */
  80         assert(f);
  81
  82         if (!f->authenticate)
  83                 return 0;
  84
  85         if (f->hmac_running)
  86                 return 0;
  87
  88         /* Prepare HMAC for next cycle */
  89         gcry_md_reset(f->hmac);
  90         FSPRG_GetKey(f->fsprg_state, key, sizeof(key), 0);
  91         gcry_md_setkey(f->hmac, key, sizeof(key));
  92
  93         f->hmac_running = true;
  94
  95         return 0;
  96 }
  97
  98 static int journal_file_get_epoch(JournalFile *f, uint64_t realtime, uint64_t *epoch) {
  99         uint64_t t;
 100
 101         assert(f);
 102         assert(epoch);
 103         assert(f->authenticate);
 104
 105         if (f->fsprg_start_usec == 0 ||
 106             f->fsprg_interval_usec == 0)
 107                 return -ENOTSUP;
 108
 109         if (realtime < f->fsprg_start_usec)
 110                 return -ESTALE;
 111
 112         t = realtime - f->fsprg_start_usec;
 113         t = t / f->fsprg_interval_usec;
 114
 115         *epoch = t;
 116         return 0;
 117 }
 118
 119 static int journal_file_need_evolve(JournalFile *f, uint64_t realtime) {
 120         uint64_t goal, epoch;
 121         int r;
 122         assert(f);
 123
 124         if (!f->authenticate)
 125                 return 0;
 126
 127         r = journal_file_get_epoch(f, realtime, &goal);
 128         if (r < 0)
 129                 return r;
 130
 131         epoch = FSPRG_GetEpoch(f->fsprg_state);
 132         if (epoch > goal)
 133                 return -ESTALE;
 134
 135         return epoch != goal;
 136 }
 137
 138 static int journal_file_evolve(JournalFile *f, uint64_t realtime) {
 139         uint64_t goal, epoch;
 140         int r;
 141
 142         assert(f);
 143
 144         if (!f->authenticate)
 145                 return 0;
 146
 147         r = journal_file_get_epoch(f, realtime, &goal);
 148         if (r < 0)
 149                 return r;
 150
 151         epoch = FSPRG_GetEpoch(f->fsprg_state);
 152         if (epoch < goal)
 153                 log_debug("Evolving FSPRG key from epoch %llu to %llu.", (unsigned long long) epoch, (unsigned long long) goal);
 154
 155         for (;;) {
 156                 if (epoch > goal)
 157                         return -ESTALE;
 158                 if (epoch == goal)
 159                         return 0;
 160
 161                 FSPRG_Evolve(f->fsprg_state);
 162                 epoch = FSPRG_GetEpoch(f->fsprg_state);
 163         }
 164 }
 165
 166 int journal_file_fsprg_seek(JournalFile *f, uint64_t goal) {
 167         void *msk;
 168         uint64_t epoch;
 169
 170         assert(f);
 171
 172         if (!f->authenticate)
 173                 return 0;
 174
 175         assert(f->fsprg_seed);
 176
 177         if (f->fsprg_state) {
 178                 /* Cheaper... */
 179
 180                 epoch = FSPRG_GetEpoch(f->fsprg_state);
 181                 if (goal == epoch)
 182                         return 0;
 183
 184                 if (goal == epoch+1) {
 185                         FSPRG_Evolve(f->fsprg_state);
 186                         return 0;
 187                 }
 188         } else {
 189                 f->fsprg_state_size = FSPRG_stateinbytes(FSPRG_RECOMMENDED_SECPAR);
 190                 f->fsprg_state = malloc(f->fsprg_state_size);
 191
 192                 if (!f->fsprg_state)
 193                         return -ENOMEM;
 194         }
 195
 196         log_debug("Seeking FSPRG key to %llu.", (unsigned long long) goal);
 197
 198         msk = alloca(FSPRG_mskinbytes(FSPRG_RECOMMENDED_SECPAR));
 199         FSPRG_GenMK(msk, NULL, f->fsprg_seed, f->fsprg_seed_size, FSPRG_RECOMMENDED_SECPAR);
 200         FSPRG_Seek(f->fsprg_state, goal, msk, f->fsprg_seed, f->fsprg_seed_size);
 201         return 0;
 202 }
 203
 204 int journal_file_maybe_append_tag(JournalFile *f, uint64_t realtime) {
 205         int r;
 206
 207         assert(f);
 208
 209         if (!f->authenticate)
 210                 return 0;
 211
 212         r = journal_file_need_evolve(f, realtime);
 213         if (r <= 0)
 214                 return 0;
 215
 216         r = journal_file_append_tag(f);
 217         if (r < 0)
 218                 return r;
 219
 220         r = journal_file_evolve(f, realtime);
 221         if (r < 0)
 222                 return r;
 223
 224         r = journal_file_hmac_start(f);
 225         if (r < 0)
 226                 return r;
 227
 228         return 0;
 229 }
 230
 231 int journal_file_hmac_put_object(JournalFile *f, int type, uint64_t p) {
 232         int r;
 233         Object *o;
 234
 235         assert(f);
 236
 237         if (!f->authenticate)
 238                 return 0;
 239
 240         r = journal_file_hmac_start(f);
 241         if (r < 0)
 242                 return r;
 243
 244         r = journal_file_move_to_object(f, type, p, &o);
 245         if (r < 0)
 246                 return r;
 247
 248         gcry_md_write(f->hmac, o, offsetof(ObjectHeader, payload));
 249
 250         switch (o->object.type) {
 251
 252         case OBJECT_DATA:
 253                 /* All but hash and payload are mutable */
 254                 gcry_md_write(f->hmac, &o->data.hash, sizeof(o->data.hash));
 255                 gcry_md_write(f->hmac, o->data.payload, le64toh(o->object.size) - offsetof(DataObject, payload));
 256                 break;
 257
 258         case OBJECT_ENTRY:
 259                 /* All */
 260                 gcry_md_write(f->hmac, &o->entry.seqnum, le64toh(o->object.size) - offsetof(EntryObject, seqnum));
 261                 break;
 262
 263         case OBJECT_FIELD_HASH_TABLE:
 264         case OBJECT_DATA_HASH_TABLE:
 265         case OBJECT_ENTRY_ARRAY:
 266                 /* Nothing: everything is mutable */
 267                 break;
 268
 269         case OBJECT_TAG:
 270                 /* All but the tag itself */
 271                 gcry_md_write(f->hmac, &o->tag.seqnum, sizeof(o->tag.seqnum));
 272                 gcry_md_write(f->hmac, &o->tag.epoch, sizeof(o->tag.epoch));
 273                 break;
 274         default:
 275                 return -EINVAL;
 276         }
 277
 278         return 0;
 279 }
 280
 281 int journal_file_hmac_put_header(JournalFile *f) {
 282         int r;
 283
 284         assert(f);
 285
 286         if (!f->authenticate)
 287                 return 0;
 288
 289         r = journal_file_hmac_start(f);
 290         if (r < 0)
 291                 return r;
 292
 293         /* All but state+reserved, boot_id, arena_size,
 294          * tail_object_offset, n_objects, n_entries,
 295          * tail_entry_seqnum, head_entry_seqnum, entry_array_offset,
 296          * head_entry_realtime, tail_entry_realtime,
 297          * tail_entry_monotonic, n_data, n_fields, n_tags,
 298          * n_entry_arrays. */
 299
 300         gcry_md_write(f->hmac, f->header->signature, offsetof(Header, state) - offsetof(Header, signature));
 301         gcry_md_write(f->hmac, &f->header->file_id, offsetof(Header, boot_id) - offsetof(Header, file_id));
 302         gcry_md_write(f->hmac, &f->header->seqnum_id, offsetof(Header, arena_size) - offsetof(Header, seqnum_id));
 303         gcry_md_write(f->hmac, &f->header->data_hash_table_offset, offsetof(Header, tail_object_offset) - offsetof(Header, data_hash_table_offset));
 304
 305         return 0;
 306 }
 307
 308 int journal_file_load_fsprg(JournalFile *f) {
 309         int r, fd = -1;
 310         char *p = NULL;
 311         struct stat st;
 312         FSPRGHeader *m = NULL;
 313         sd_id128_t machine;
 314
 315         assert(f);
 316
 317         if (!f->authenticate)
 318                 return 0;
 319
 320         r = sd_id128_get_machine(&machine);
 321         if (r < 0)
 322                 return r;
 323
 324         if (asprintf(&p, "/var/log/journal/" SD_ID128_FORMAT_STR "/fsprg",
 325                      SD_ID128_FORMAT_VAL(machine)) < 0)
 326                 return -ENOMEM;
 327
 328         fd = open(p, O_RDWR|O_CLOEXEC|O_NOCTTY, 0600);
 329         if (fd < 0) {
 330                 log_error("Failed to open %s: %m", p);
 331                 r = -errno;
 332                 goto finish;
 333         }
 334
 335         if (fstat(fd, &st) < 0) {
 336                 r = -errno;
 337                 goto finish;
 338         }
 339
 340         if (st.st_size < (off_t) sizeof(FSPRGHeader)) {
 341                 r = -ENODATA;
 342                 goto finish;
 343         }
 344
 345         m = mmap(NULL, PAGE_ALIGN(sizeof(FSPRGHeader)), PROT_READ, MAP_SHARED, fd, 0);
 346         if (m == MAP_FAILED) {
 347                 m = NULL;
 348                 r = -errno;
 349                 goto finish;
 350         }
 351
 352         if (memcmp(m->signature, FSPRG_HEADER_SIGNATURE, 8) != 0) {
 353                 r = -EBADMSG;
 354                 goto finish;
 355         }
 356
 357         if (m->incompatible_flags != 0) {
 358                 r = -EPROTONOSUPPORT;
 359                 goto finish;
 360         }
 361
 362         if (le64toh(m->header_size) < sizeof(FSPRGHeader)) {
 363                 r = -EBADMSG;
 364                 goto finish;
 365         }
 366
 367         if (le64toh(m->state_size) != FSPRG_stateinbytes(m->secpar)) {
 368                 r = -EBADMSG;
 369                 goto finish;
 370         }
 371
 372         f->fsprg_file_size = le64toh(m->header_size) + le64toh(m->state_size);
 373         if ((uint64_t) st.st_size < f->fsprg_file_size) {
 374                 r = -ENODATA;
 375                 goto finish;
 376         }
 377
 378         if (!sd_id128_equal(machine, m->machine_id)) {
 379                 r = -EHOSTDOWN;
 380                 goto finish;
 381         }
 382
 383         if (le64toh(m->fsprg_start_usec) <= 0 ||
 384             le64toh(m->fsprg_interval_usec) <= 0) {
 385                 r = -EBADMSG;
 386                 goto finish;
 387         }
 388
 389         f->fsprg_file = mmap(NULL, PAGE_ALIGN(f->fsprg_file_size), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
 390         if (f->fsprg_file == MAP_FAILED) {
 391                 f->fsprg_file = NULL;
 392                 r = -errno;
 393                 goto finish;
 394         }
 395
 396         f->fsprg_start_usec = le64toh(f->fsprg_file->fsprg_start_usec);
 397         f->fsprg_interval_usec = le64toh(f->fsprg_file->fsprg_interval_usec);
 398
 399         f->fsprg_state = (uint8_t*) f->fsprg_file + le64toh(f->fsprg_file->header_size);
 400         f->fsprg_state_size = le64toh(f->fsprg_file->state_size);
 401
 402         r = 0;
 403
 404 finish:
 405         if (m)
 406                 munmap(m, PAGE_ALIGN(sizeof(FSPRGHeader)));
 407
 408         if (fd >= 0)
 409                 close_nointr_nofail(fd);
 410
 411         free(p);
 412         return r;
 413 }
 414
 415 int journal_file_setup_hmac(JournalFile *f) {
 416         gcry_error_t e;
 417
 418         if (!f->authenticate)
 419                 return 0;
 420
 421         e = gcry_md_open(&f->hmac, GCRY_MD_SHA256, GCRY_MD_FLAG_HMAC);
 422         if (e != 0)
 423                 return -ENOTSUP;
 424
 425         return 0;
 426 }
 427
 428 int journal_file_append_first_tag(JournalFile *f) {
 429         int r;
 430         uint64_t p;
 431
 432         if (!f->authenticate)
 433                 return 0;
 434
 435         log_debug("Calculating first tag...");
 436
 437         r = journal_file_hmac_put_header(f);
 438         if (r < 0)
 439                 return r;
 440
 441         p = le64toh(f->header->field_hash_table_offset);
 442         if (p < offsetof(Object, hash_table.items))
 443                 return -EINVAL;
 444         p -= offsetof(Object, hash_table.items);
 445
 446         r = journal_file_hmac_put_object(f, OBJECT_FIELD_HASH_TABLE, p);
 447         if (r < 0)
 448                 return r;
 449
 450         p = le64toh(f->header->data_hash_table_offset);
 451         if (p < offsetof(Object, hash_table.items))
 452                 return -EINVAL;
 453         p -= offsetof(Object, hash_table.items);
 454
 455         r = journal_file_hmac_put_object(f, OBJECT_DATA_HASH_TABLE, p);
 456         if (r < 0)
 457                 return r;
 458
 459         r = journal_file_append_tag(f);
 460         if (r < 0)
 461                 return r;
 462
 463         return 0;
 464 }
 465
 466 bool journal_file_fsprg_enabled(JournalFile *f) {
 467         assert(f);
 468
 469         return !!(le32toh(f->header->compatible_flags) & HEADER_COMPATIBLE_AUTHENTICATED);
 470 }