src/shared/creds-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <sys/file.h>
   4
   5 #if HAVE_OPENSSL
   6 #include <openssl/err.h>
   7 #endif
   8
   9 #include "sd-id128.h"
  10
  11 #include "blockdev-util.h"
  12 #include "chattr-util.h"
  13 #include "creds-util.h"
  14 #include "env-util.h"
  15 #include "fd-util.h"
  16 #include "fileio.h"
  17 #include "fs-util.h"
  18 #include "io-util.h"
  19 #include "memory-util.h"
  20 #include "mkdir.h"
  21 #include "openssl-util.h"
  22 #include "path-util.h"
  23 #include "random-util.h"
  24 #include "sparse-endian.h"
  25 #include "stat-util.h"
  26 #include "tpm2-util.h"
  27 #include "virt.h"
  28
  29 bool credential_name_valid(const char *s) {
  30         /* We want that credential names are both valid in filenames (since that's our primary way to pass
  31          * them around) and as fdnames (which is how we might want to pass them around eventually) */
  32         return filename_is_valid(s) && fdname_is_valid(s);
  33 }
  34
  35 int get_credentials_dir(const char **ret) {
  36         const char *e;
  37
  38         assert(ret);
  39
  40         e = secure_getenv("CREDENTIALS_DIRECTORY");
  41         if (!e)
  42                 return -ENXIO;
  43
  44         if (!path_is_absolute(e) || !path_is_normalized(e))
  45                 return -EINVAL;
  46
  47         *ret = e;
  48         return 0;
  49 }
  50
  51 int read_credential(const char *name, void **ret, size_t *ret_size) {
  52         _cleanup_free_ char *fn = NULL;
  53         const char *d;
  54         int r;
  55
  56         assert(ret);
  57
  58         if (!credential_name_valid(name))
  59                 return -EINVAL;
  60
  61         r = get_credentials_dir(&d);
  62         if (r < 0)
  63                 return r;
  64
  65         fn = path_join(d, name);
  66         if (!fn)
  67                 return -ENOMEM;
  68
  69         return read_full_file_full(
  70                         AT_FDCWD, fn,
  71                         UINT64_MAX, SIZE_MAX,
  72                         READ_FULL_FILE_SECURE,
  73                         NULL,
  74                         (char**) ret, ret_size);
  75 }
  76
  77 #if HAVE_OPENSSL
  78
  79 #define CREDENTIAL_HOST_SECRET_SIZE 4096
  80
  81 static const sd_id128_t credential_app_id =
  82         SD_ID128_MAKE(d3,ac,ec,ba,0d,ad,4c,df,b8,c9,38,15,28,93,6c,58);
  83
  84 struct credential_host_secret_format {
  85         /* The hashed machine ID of the machine this belongs to. Why? We want to ensure that each machine
  86          * gets its own secret, even if people forget to flush out this secret file. Hence we bind it to the
  87          * machine ID, for which there's hopefully a better chance it will be flushed out. We use a hashed
  88          * machine ID instead of the literal one, because it's trivial to, and it might be a good idea not
  89          * being able to directly associate a secret key file with a host. */
  90         sd_id128_t machine_id;
  91
  92         /* The actual secret key */
  93         uint8_t data[CREDENTIAL_HOST_SECRET_SIZE];
  94 } _packed_;
  95
  96 static int make_credential_host_secret(
  97                 int dfd,
  98                 const sd_id128_t machine_id,
  99                 const char *fn,
 100                 void **ret_data,
 101                 size_t *ret_size) {
 102
 103         struct credential_host_secret_format buf;
 104         _cleanup_free_ char *t = NULL;
 105         _cleanup_close_ int fd = -1;
 106         int r;
 107
 108         assert(dfd >= 0);
 109         assert(fn);
 110
 111         fd = openat(dfd, ".", O_CLOEXEC|O_WRONLY|O_TMPFILE, 0400);
 112         if (fd < 0) {
 113                 log_debug_errno(errno, "Failed to create temporary credential file with O_TMPFILE, proceeding without: %m");
 114
 115                 if (asprintf(&t, "credential.secret.%016" PRIx64, random_u64()) < 0)
 116                         return -ENOMEM;
 117
 118                 fd = openat(dfd, t, O_CLOEXEC|O_WRONLY|O_CREAT|O_EXCL|O_NOFOLLOW, 0400);
 119                 if (fd < 0)
 120                         return -errno;
 121         }
 122
 123         r = chattr_secret(fd, 0);
 124         if (r < 0)
 125                 log_debug_errno(r, "Failed to set file attributes for secrets file, ignoring: %m");
 126
 127         buf = (struct credential_host_secret_format) {
 128                 .machine_id = machine_id,
 129         };
 130
 131         r = genuine_random_bytes(buf.data, sizeof(buf.data), RANDOM_BLOCK);
 132         if (r < 0)
 133                 goto finish;
 134
 135         r = loop_write(fd, &buf, sizeof(buf), false);
 136         if (r < 0)
 137                 goto finish;
 138
 139         if (fsync(fd) < 0) {
 140                 r = -errno;
 141                 goto finish;
 142         }
 143
 144         if (t) {
 145                 r = rename_noreplace(dfd, t, dfd, fn);
 146                 if (r < 0)
 147                         goto finish;
 148
 149                 t = mfree(t);
 150         } else if (linkat(fd, "", dfd, fn, AT_EMPTY_PATH) < 0) {
 151                 r = -errno;
 152                 goto finish;
 153         }
 154
 155         if (fsync(dfd) < 0) {
 156                 r = -errno;
 157                 goto finish;
 158         }
 159
 160         if (ret_data) {
 161                 void *copy;
 162
 163                 copy = memdup(buf.data, sizeof(buf.data));
 164                 if (!copy) {
 165                         r = -ENOMEM;
 166                         goto finish;
 167                 }
 168
 169                 *ret_data = copy;
 170         }
 171
 172         if (ret_size)
 173                 *ret_size = sizeof(buf.data);
 174
 175         r = 0;
 176
 177 finish:
 178         if (t && unlinkat(dfd, t, 0) < 0)
 179                 log_debug_errno(errno, "Failed to remove temporary credential key: %m");
 180
 181         explicit_bzero_safe(&buf, sizeof(buf));
 182         return r;
 183 }
 184
 185 int get_credential_host_secret(CredentialSecretFlags flags, void **ret, size_t *ret_size) {
 186         _cleanup_free_ char *efn = NULL, *ep = NULL;
 187         _cleanup_close_ int dfd = -1;
 188         sd_id128_t machine_id;
 189         const char *e, *fn, *p;
 190         int r;
 191
 192         r = sd_id128_get_machine_app_specific(credential_app_id, &machine_id);
 193         if (r < 0)
 194                 return r;
 195
 196         e = secure_getenv("SYSTEMD_CREDENTIAL_SECRET");
 197         if (e) {
 198                 if (!path_is_normalized(e))
 199                         return -EINVAL;
 200                 if (!path_is_absolute(e))
 201                         return -EINVAL;
 202
 203                 r = path_extract_directory(e, &ep);
 204                 if (r < 0)
 205                         return r;
 206
 207                 r = path_extract_filename(e, &efn);
 208                 if (r < 0)
 209                         return r;
 210
 211                 p = ep;
 212                 fn = efn;
 213         } else {
 214                 p = "/var/lib/systemd";
 215                 fn = "credential.secret";
 216         }
 217
 218         (void) mkdir_p(p, 0755);
 219         dfd = open(p, O_CLOEXEC|O_DIRECTORY|O_RDONLY);
 220         if (dfd < 0)
 221                 return -errno;
 222
 223         if (FLAGS_SET(flags, CREDENTIAL_SECRET_FAIL_ON_TEMPORARY_FS)) {
 224                 r = fd_is_temporary_fs(dfd);
 225                 if (r < 0)
 226                         return r;
 227                 if (r > 0)
 228                         return -ENOMEDIUM;
 229         }
 230
 231         for (unsigned attempt = 0;; attempt++) {
 232                 _cleanup_(erase_and_freep) struct credential_host_secret_format *f = NULL;
 233                 _cleanup_close_ int fd = -1;
 234                 size_t l = 0;
 235                 ssize_t n = 0;
 236                 struct stat st;
 237
 238                 if (attempt >= 3) /* Somebody is playing games with us */
 239                         return -EIO;
 240
 241                 fd = openat(dfd, fn, O_CLOEXEC|O_RDONLY|O_NOCTTY|O_NOFOLLOW);
 242                 if (fd < 0) {
 243                         if (errno != ENOENT || !FLAGS_SET(flags, CREDENTIAL_SECRET_GENERATE))
 244                                 return -errno;
 245
 246                         r = make_credential_host_secret(dfd, machine_id, fn, ret, ret_size);
 247                         if (r == -EEXIST) {
 248                                 log_debug_errno(r, "Credential secret was created while we were creating it. Trying to read new secret.");
 249                                 continue;
 250                         }
 251                         if (r < 0)
 252                                 return r;
 253
 254                         return 0;
 255                 }
 256
 257                 if (fstat(fd, &st) < 0)
 258                         return -errno;
 259
 260                 r = stat_verify_regular(&st);
 261                 if (r < 0)
 262                         return r;
 263                 if (st.st_nlink == 0) /* Deleted by now, try again */
 264                         continue;
 265                 if (st.st_nlink > 1)
 266                         return -EPERM; /* Our deletion check won't work if hardlinked somewhere else */
 267                 if ((st.st_mode & 07777) != 0400) /* Don't use file if not 0400 access mode */
 268                         return -EPERM;
 269                 if (st.st_size > 16*1024*1024)
 270                         return -E2BIG;
 271                 l = st.st_size;
 272                 if (l < offsetof(struct credential_host_secret_format, data) + 1)
 273                         return -EINVAL;
 274
 275                 f = malloc(l+1);
 276                 if (!f)
 277                         return -ENOMEM;
 278
 279                 n = read(fd, f, l+1);
 280                 if (n < 0)
 281                         return -errno;
 282                 if ((size_t) n != l) /* What? The size changed? */
 283                         return -EIO;
 284
 285                 if (sd_id128_equal(machine_id, f->machine_id)) {
 286                         size_t sz;
 287
 288                         if (FLAGS_SET(flags, CREDENTIAL_SECRET_WARN_NOT_ENCRYPTED)) {
 289                                 r = fd_is_encrypted(fd);
 290                                 if (r < 0)
 291                                         log_debug_errno(r, "Failed to determine if credential secret file '%s/%s' is encrypted.", p, fn);
 292                                 else if (r == 0)
 293                                         log_warning("Credential secret file '%s/%s' is not located on encrypted media, using anyway.", p, fn);
 294                         }
 295
 296                         sz = l - offsetof(struct credential_host_secret_format, data);
 297                         assert(sz > 0);
 298
 299                         if (ret) {
 300                                 void *copy;
 301
 302                                 assert(sz <= sizeof(f->data)); /* Ensure we don't read past f->data bounds */
 303
 304                                 copy = memdup(f->data, sz);
 305                                 if (!copy)
 306                                         return -ENOMEM;
 307
 308                                 *ret = copy;
 309                         }
 310
 311                         if (ret_size)
 312                                 *ret_size = sz;
 313
 314                         return 0;
 315                 }
 316
 317                 /* Hmm, this secret is from somewhere else. Let's delete the file. Let's first acquire a lock
 318                  * to ensure we are the only ones accessing the file while we delete it. */
 319
 320                 if (flock(fd, LOCK_EX) < 0)
 321                         return -errno;
 322
 323                 /* Before we delete it check that the file is still linked into the file system */
 324                 if (fstat(fd, &st) < 0)
 325                         return -errno;
 326                 if (st.st_nlink == 0) /* Already deleted by now? */
 327                         continue;
 328                 if (st.st_nlink != 1) /* Safety check, someone is playing games with us */
 329                         return -EPERM;
 330
 331                 if (unlinkat(dfd, fn, 0) < 0)
 332                         return -errno;
 333
 334                 /* And now try again */
 335         }
 336 }
 337
 338 /* Construction is like this:
 339  *
 340  * A symmetric encryption key is derived from:
 341  *
 342  *      1. Either the "host" key (a key stored in /var/lib/credential.secret)
 343  *
 344  *      2. A key generated by letting the TPM2 calculate an HMAC hash of some nonce we pass to it, keyed
 345  *         by a key derived from its internal seed key.
 346  *
 347  *      3. The concatenation of the above.
 348  *
 349  * The above is hashed with SHA256 which is then used as encryption key for AES256-GCM. The encrypted
 350  * credential is a short (unencrypted) header describing which of the three keys to use, the IV to use for
 351  * AES256-GCM and some more meta information (sizes of certain objects) that is strictly speaking redundant,
 352  * but kinda nice to have since we can have a more generic parser. If the TPM2 key is used this is followed
 353  * by another (unencrypted) header, with information about the TPM2 policy used (specifically: the PCR mask
 354  * to bind against, and a hash of the resulting policy — the latter being redundant, but speeding up things a
 355  * bit, since we can more quickly refuse PCR state), followed by a sealed/exported TPM2 HMAC key. This is
 356  * then followed by the encrypted data, which begins with a metadata header (which contains validity
 357  * timestamps as well as the credential name), followed by the actual credential payload. The file ends in
 358  * the AES256-GCM tag. To make things simple, the AES256-GCM AAD covers the main and the TPM2 header in
 359  * full. This means the whole file is either protected by AAD, or is ciphertext, or is the tag. No
 360  * unprotected data is included.
 361  */
 362
 363 struct _packed_ encrypted_credential_header {
 364         sd_id128_t id;
 365         le32_t key_size;
 366         le32_t block_size;
 367         le32_t iv_size;
 368         le32_t tag_size;
 369         uint8_t iv[];
 370         /* Followed by NUL bytes until next 8 byte boundary */
 371 };
 372
 373 struct _packed_ tpm2_credential_header {
 374         le64_t pcr_mask; /* Note that the spec for PC Clients only mandates 24 PCRs, and that's what systems
 375                           * generally have. But keep the door open for more. */
 376         le16_t pcr_bank; /* For now, either TPM2_ALG_SHA256 or TPM2_ALG_SHA1 */
 377         le16_t _zero;    /* Filler to maintain 32bit alignment */
 378         le32_t blob_size;
 379         le32_t policy_hash_size;
 380         uint8_t policy_hash_and_blob[];
 381         /* Followed by NUL bytes until next 8 byte boundary */
 382 };
 383
 384 struct _packed_ metadata_credential_header {
 385         le64_t timestamp;
 386         le64_t not_after;
 387         le32_t name_size;
 388         char name[];
 389         /* Followed by NUL bytes until next 8 byte boundary */
 390 };
 391
 392 /* Some generic limit for parts of the encrypted credential for which we don't know the right size ahead of
 393  * time, but where we are really sure it won't be larger than this. Should be larger than any possible IV,
 394  * padding, tag size and so on. This is purely used for early filtering out of invalid sizes. */
 395 #define CREDENTIAL_FIELD_SIZE_MAX (16U*1024U)
 396
 397 static int sha256_hash_host_and_tpm2_key(
 398                 const void *host_key,
 399                 size_t host_key_size,
 400                 const void *tpm2_key,
 401                 size_t tpm2_key_size,
 402                 uint8_t ret[static SHA256_DIGEST_LENGTH]) {
 403
 404         SHA256_CTX sha256_context;
 405
 406         assert(host_key_size == 0 || host_key);
 407         assert(tpm2_key_size == 0 || tpm2_key);
 408         assert(ret);
 409
 410         /* Combines the host key and the TPM2 HMAC hash into a SHA256 hash value we'll use as symmetric encryption key. */
 411
 412         if (SHA256_Init(&sha256_context) != 1)
 413                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to initial SHA256 context.");
 414
 415         if (host_key && SHA256_Update(&sha256_context, host_key, host_key_size) != 1)
 416                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to hash host key.");
 417
 418         if (tpm2_key && SHA256_Update(&sha256_context, tpm2_key, tpm2_key_size) != 1)
 419                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to hash TPM2 key.");
 420
 421         if (SHA256_Final(ret, &sha256_context) != 1)
 422                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to finalize SHA256 hash.");
 423
 424         return 0;
 425 }
 426
 427 int encrypt_credential_and_warn(
 428                 sd_id128_t with_key,
 429                 const char *name,
 430                 usec_t timestamp,
 431                 usec_t not_after,
 432                 const char *tpm2_device,
 433                 uint32_t tpm2_pcr_mask,
 434                 const void *input,
 435                 size_t input_size,
 436                 void **ret,
 437                 size_t *ret_size) {
 438
 439         _cleanup_(EVP_CIPHER_CTX_freep) EVP_CIPHER_CTX *context = NULL;
 440         _cleanup_(erase_and_freep) void *host_key = NULL, *tpm2_key = NULL;
 441         size_t host_key_size = 0, tpm2_key_size = 0, tpm2_blob_size = 0, tpm2_policy_hash_size = 0, output_size, p, ml;
 442         _cleanup_free_ void *tpm2_blob = NULL, *tpm2_policy_hash = NULL, *iv = NULL, *output = NULL;
 443         _cleanup_free_ struct metadata_credential_header *m = NULL;
 444         struct encrypted_credential_header *h;
 445         int ksz, bsz, ivsz, tsz, added, r;
 446         uint8_t md[SHA256_DIGEST_LENGTH];
 447         uint16_t tpm2_pcr_bank = 0;
 448         const EVP_CIPHER *cc;
 449 #if HAVE_TPM2
 450         bool try_tpm2 = false;
 451 #endif
 452         sd_id128_t id;
 453
 454         assert(input || input_size == 0);
 455         assert(ret);
 456         assert(ret_size);
 457
 458         if (name && !credential_name_valid(name))
 459                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid credential name: %s", name);
 460
 461         if (not_after != USEC_INFINITY && timestamp != USEC_INFINITY && not_after < timestamp)
 462                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Credential is invalidated before it is valid (" USEC_FMT " < " USEC_FMT ").", not_after, timestamp);
 463
 464         if (DEBUG_LOGGING) {
 465                 char buf[FORMAT_TIMESTAMP_MAX];
 466
 467                 if (name)
 468                         log_debug("Including credential name '%s' in encrypted credential.", name);
 469                 if (timestamp != USEC_INFINITY)
 470                         log_debug("Including timestamp '%s' in encrypted credential.", format_timestamp(buf, sizeof(buf), timestamp));
 471                 if (not_after != USEC_INFINITY)
 472                         log_debug("Including not-after timestamp '%s' in encrypted credential.", format_timestamp(buf, sizeof(buf), not_after));
 473         }
 474
 475         if (sd_id128_is_null(with_key) ||
 476             sd_id128_in_set(with_key, CRED_AES256_GCM_BY_HOST, CRED_AES256_GCM_BY_HOST_AND_TPM2_HMAC)) {
 477
 478                 r = get_credential_host_secret(
 479                                 CREDENTIAL_SECRET_GENERATE|
 480                                 CREDENTIAL_SECRET_WARN_NOT_ENCRYPTED|
 481                                 (sd_id128_is_null(with_key) ? CREDENTIAL_SECRET_FAIL_ON_TEMPORARY_FS : 0),
 482                                 &host_key,
 483                                 &host_key_size);
 484                 if (r == -ENOMEDIUM && sd_id128_is_null(with_key))
 485                         log_debug_errno(r, "Credential host secret location on temporary file system, not using.");
 486                 else if (r < 0)
 487                         return log_error_errno(r, "Failed to determine local credential host secret: %m");
 488         }
 489
 490 #if HAVE_TPM2
 491         if (sd_id128_is_null(with_key)) {
 492                 /* If automatic mode is selected and we are running in a container, let's not try TPM2. OTOH
 493                  * if user picks TPM2 explicitly, let's always honour the request and try. */
 494
 495                 r = detect_container();
 496                 if (r < 0)
 497                         log_debug_errno(r, "Failed to determine whether we are running in a container, ignoring: %m");
 498                 else if (r > 0)
 499                         log_debug("Running in container, not attempting to use TPM2.");
 500
 501                 try_tpm2 = r <= 0;
 502         }
 503
 504         if (try_tpm2 ||
 505             sd_id128_in_set(with_key, CRED_AES256_GCM_BY_TPM2_HMAC, CRED_AES256_GCM_BY_HOST_AND_TPM2_HMAC)) {
 506
 507                 r = tpm2_seal(tpm2_device,
 508                               tpm2_pcr_mask,
 509                               &tpm2_key,
 510                               &tpm2_key_size,
 511                               &tpm2_blob,
 512                               &tpm2_blob_size,
 513                               &tpm2_policy_hash,
 514                               &tpm2_policy_hash_size,
 515                               &tpm2_pcr_bank);
 516                 if (r < 0) {
 517                         if (!sd_id128_is_null(with_key))
 518                                 return r;
 519
 520                         log_debug_errno(r, "TPM2 sealing didn't work, not using: %m");
 521                 }
 522
 523                 assert(tpm2_blob_size <= CREDENTIAL_FIELD_SIZE_MAX);
 524                 assert(tpm2_policy_hash_size <= CREDENTIAL_FIELD_SIZE_MAX);
 525         }
 526 #endif
 527
 528         if (sd_id128_is_null(with_key)) {
 529                 /* Let's settle the key type in auto mode now. */
 530
 531                 if (host_key && tpm2_key)
 532                         id = CRED_AES256_GCM_BY_HOST_AND_TPM2_HMAC;
 533                 else if (tpm2_key)
 534                         id = CRED_AES256_GCM_BY_TPM2_HMAC;
 535                 else if (host_key)
 536                         id = CRED_AES256_GCM_BY_HOST;
 537                 else
 538                         return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
 539                                                "TPM2 not available and host key located on temporary file system, no encryption key available.");
 540         } else
 541                 id = with_key;
 542
 543         /* Let's now take the host key and the TPM2 key and hash it together, to use as encryption key for the data */
 544         r = sha256_hash_host_and_tpm2_key(host_key, host_key_size, tpm2_key, tpm2_key_size, md);
 545         if (r < 0)
 546                 return r;
 547
 548         assert_se(cc = EVP_aes_256_gcm());
 549
 550         ksz = EVP_CIPHER_key_length(cc);
 551         assert(ksz == sizeof(md));
 552
 553         bsz = EVP_CIPHER_block_size(cc);
 554         assert(bsz > 0);
 555         assert((size_t) bsz <= CREDENTIAL_FIELD_SIZE_MAX);
 556
 557         ivsz = EVP_CIPHER_iv_length(cc);
 558         if (ivsz > 0) {
 559                 assert((size_t) ivsz <= CREDENTIAL_FIELD_SIZE_MAX);
 560
 561                 iv = malloc(ivsz);
 562                 if (!iv)
 563                         return log_oom();
 564
 565                 r = genuine_random_bytes(iv, ivsz, RANDOM_BLOCK);
 566                 if (r < 0)
 567                         return log_error_errno(r, "Failed to acquired randomized IV: %m");
 568         }
 569
 570         tsz = 16; /* FIXME: On OpenSSL 3 there is EVP_CIPHER_CTX_get_tag_length(), until then let's hardcode this */
 571
 572         context = EVP_CIPHER_CTX_new();
 573         if (!context)
 574                 return log_error_errno(SYNTHETIC_ERRNO(ENOMEM), "Failed to allocate encryption object: %s",
 575                                        ERR_error_string(ERR_get_error(), NULL));
 576
 577         if (EVP_EncryptInit_ex(context, cc, NULL, md, iv) != 1)
 578                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to initialize encryption context: %s",
 579                                        ERR_error_string(ERR_get_error(), NULL));
 580
 581         /* Just an upper estimate */
 582         output_size =
 583                 ALIGN8(offsetof(struct encrypted_credential_header, iv) + ivsz) +
 584                 ALIGN8(tpm2_key ? offsetof(struct tpm2_credential_header, policy_hash_and_blob) + tpm2_blob_size + tpm2_policy_hash_size : 0) +
 585                 ALIGN8(offsetof(struct metadata_credential_header, name) + strlen_ptr(name)) +
 586                 input_size + 2U * (size_t) bsz +
 587                 tsz;
 588
 589         output = malloc0(output_size);
 590         if (!output)
 591                 return log_oom();
 592
 593         h = (struct encrypted_credential_header*) output;
 594         h->id = id;
 595         h->block_size = htole32(bsz);
 596         h->key_size = htole32(ksz);
 597         h->tag_size = htole32(tsz);
 598         h->iv_size = htole32(ivsz);
 599         memcpy(h->iv, iv, ivsz);
 600
 601         p = ALIGN8(offsetof(struct encrypted_credential_header, iv) + ivsz);
 602
 603         if (tpm2_key) {
 604                 struct tpm2_credential_header *t;
 605
 606                 t = (struct tpm2_credential_header*) ((uint8_t*) output + p);
 607                 t->pcr_mask = htole64(tpm2_pcr_mask);
 608                 t->pcr_bank = htole16(tpm2_pcr_bank);
 609                 t->blob_size = htole32(tpm2_blob_size);
 610                 t->policy_hash_size = htole32(tpm2_policy_hash_size);
 611                 memcpy(t->policy_hash_and_blob, tpm2_blob, tpm2_blob_size);
 612                 memcpy(t->policy_hash_and_blob + tpm2_blob_size, tpm2_policy_hash, tpm2_policy_hash_size);
 613
 614                 p += ALIGN8(offsetof(struct tpm2_credential_header, policy_hash_and_blob) + tpm2_blob_size + tpm2_policy_hash_size);
 615         }
 616
 617         /* Pass the encrypted + TPM2 header as AAD */
 618         if (EVP_EncryptUpdate(context, NULL, &added, output, p) != 1)
 619                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to write AAD data: %s",
 620                                        ERR_error_string(ERR_get_error(), NULL));
 621
 622         /* Now construct the metadata header */
 623         ml = strlen_ptr(name);
 624         m = malloc0(ALIGN8(offsetof(struct metadata_credential_header, name) + ml));
 625         if (!m)
 626                 return log_oom();
 627
 628         m->timestamp = htole64(timestamp);
 629         m->not_after = htole64(not_after);
 630         m->name_size = htole32(ml);
 631         memcpy_safe(m->name, name, ml);
 632
 633         /* And encrypt the metadata header */
 634         if (EVP_EncryptUpdate(context, (uint8_t*) output + p, &added, (const unsigned char*) m, ALIGN8(offsetof(struct metadata_credential_header, name) + ml)) != 1)
 635                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to encrypt metadata header: %s",
 636                                        ERR_error_string(ERR_get_error(), NULL));
 637
 638         assert(added >= 0);
 639         assert((size_t) added <= output_size - p);
 640         p += added;
 641
 642         /* Then encrypt the plaintext */
 643         if (EVP_EncryptUpdate(context, (uint8_t*) output + p, &added, input, input_size) != 1)
 644                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to encrypt data: %s",
 645                                        ERR_error_string(ERR_get_error(), NULL));
 646
 647         assert(added >= 0);
 648         assert((size_t) added <= output_size - p);
 649         p += added;
 650
 651         /* Finalize */
 652         if (EVP_EncryptFinal_ex(context, (uint8_t*) output + p, &added) != 1)
 653                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to finalize data encryption: %s",
 654                                        ERR_error_string(ERR_get_error(), NULL));
 655
 656         assert(added >= 0);
 657         assert((size_t) added <= output_size - p);
 658         p += added;
 659
 660         assert(p <= output_size - tsz);
 661
 662         /* Append tag */
 663         if (EVP_CIPHER_CTX_ctrl(context, EVP_CTRL_GCM_GET_TAG, tsz, (uint8_t*) output + p) != 1)
 664                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to get tag: %s",
 665                                        ERR_error_string(ERR_get_error(), NULL));
 666
 667         p += tsz;
 668         assert(p <= output_size);
 669
 670         if (DEBUG_LOGGING && input_size > 0) {
 671                 size_t base64_size;
 672
 673                 base64_size = DIV_ROUND_UP(p * 4, 3); /* Include base64 size increase in debug output */
 674                 assert(base64_size >= input_size);
 675                 log_debug("Input of %zu bytes grew to output of %zu bytes (+%2zu%%).", input_size, base64_size, base64_size * 100 / input_size - 100);
 676         }
 677
 678         *ret = TAKE_PTR(output);
 679         *ret_size = p;
 680
 681         return 0;
 682 }
 683
 684 int decrypt_credential_and_warn(
 685                 const char *validate_name,
 686                 usec_t validate_timestamp,
 687                 const char *tpm2_device,
 688                 const void *input,
 689                 size_t input_size,
 690                 void **ret,
 691                 size_t *ret_size) {
 692
 693         _cleanup_(erase_and_freep) void *host_key = NULL, *tpm2_key = NULL, *plaintext = NULL;
 694         _cleanup_(EVP_CIPHER_CTX_freep) EVP_CIPHER_CTX *context = NULL;
 695         size_t host_key_size = 0, tpm2_key_size = 0, plaintext_size, p, hs;
 696         struct encrypted_credential_header *h;
 697         struct metadata_credential_header *m;
 698         uint8_t md[SHA256_DIGEST_LENGTH];
 699         bool with_tpm2, with_host_key;
 700         const EVP_CIPHER *cc;
 701         int r, added;
 702
 703         assert(input || input_size == 0);
 704         assert(ret);
 705         assert(ret_size);
 706
 707         h = (struct encrypted_credential_header*) input;
 708
 709         /* The ID must fit in, for the current and all future formats */
 710         if (input_size < sizeof(h->id))
 711                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Encrypted file too short.");
 712
 713         with_host_key = sd_id128_in_set(h->id, CRED_AES256_GCM_BY_HOST, CRED_AES256_GCM_BY_HOST_AND_TPM2_HMAC);
 714         with_tpm2 = sd_id128_in_set(h->id, CRED_AES256_GCM_BY_TPM2_HMAC, CRED_AES256_GCM_BY_HOST_AND_TPM2_HMAC);
 715
 716         if (!with_host_key && !with_tpm2)
 717                 return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Unknown encryption format, or corrupted data: %m");
 718
 719         /* Now we know the minimum header size */
 720         if (input_size < offsetof(struct encrypted_credential_header, iv))
 721                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Encrypted file too short.");
 722
 723         /* Verify some basic header values */
 724         if (le32toh(h->key_size) != sizeof(md))
 725                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected key size in header.");
 726         if (le32toh(h->block_size) <= 0 || le32toh(h->block_size) > CREDENTIAL_FIELD_SIZE_MAX)
 727                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected block size in header.");
 728         if (le32toh(h->iv_size) > CREDENTIAL_FIELD_SIZE_MAX)
 729                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "IV size too large.");
 730         if (le32toh(h->tag_size) != 16) /* FIXME: On OpenSSL 3, let's verify via EVP_CIPHER_CTX_get_tag_length() */
 731                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected tag size in header.");
 732
 733         /* Ensure we have space for the full header now (we don't know the size of the name hence this is a
 734          * lower limit only) */
 735         if (input_size <
 736             ALIGN8(offsetof(struct encrypted_credential_header, iv) + le32toh(h->iv_size)) +
 737             ALIGN8((with_tpm2 ? offsetof(struct tpm2_credential_header, policy_hash_and_blob) : 0)) +
 738             ALIGN8(offsetof(struct metadata_credential_header, name)) +
 739             le32toh(h->tag_size))
 740                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Encrypted file too short.");
 741
 742         p = ALIGN8(offsetof(struct encrypted_credential_header, iv) + le32toh(h->iv_size));
 743
 744         if (with_tpm2) {
 745 #if HAVE_TPM2
 746                 struct tpm2_credential_header* t = (struct tpm2_credential_header*) ((uint8_t*) input + p);
 747
 748                 if (le64toh(t->pcr_mask) >= (UINT64_C(1) << TPM2_PCRS_MAX))
 749                         return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "TPM2 PCR mask out of range.");
 750                 if (!tpm2_pcr_bank_supported(le16toh(t->pcr_bank)))
 751                         return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "TPM2 PCR bank invalid or not supported");
 752                 if (le16toh(t->_zero) != 0)
 753                         return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "TPM2 padding space not zero.");
 754                 if (le32toh(t->blob_size) > CREDENTIAL_FIELD_SIZE_MAX)
 755                         return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected TPM2 blob size.");
 756                 if (le32toh(t->policy_hash_size) > CREDENTIAL_FIELD_SIZE_MAX)
 757                         return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected TPM2 policy hash size.");
 758
 759                 /* Ensure we have space for the full TPM2 header now (still don't know the name, and its size
 760                  * though, hence still just a lower limit test only) */
 761                 if (input_size <
 762                     ALIGN8(offsetof(struct encrypted_credential_header, iv) + le32toh(h->iv_size)) +
 763                     ALIGN8(offsetof(struct tpm2_credential_header, policy_hash_and_blob) + le32toh(t->blob_size) + le32toh(t->policy_hash_size)) +
 764                     ALIGN8(offsetof(struct metadata_credential_header, name)) +
 765                     le32toh(h->tag_size))
 766                         return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Encrypted file too short.");
 767
 768                 r = tpm2_unseal(tpm2_device,
 769                                 le64toh(t->pcr_mask),
 770                                 le16toh(t->pcr_bank),
 771                                 t->policy_hash_and_blob,
 772                                 le32toh(t->blob_size),
 773                                 t->policy_hash_and_blob + le32toh(t->blob_size),
 774                                 le32toh(t->policy_hash_size),
 775                                 &tpm2_key,
 776                                 &tpm2_key_size);
 777                 if (r < 0)
 778                         return r;
 779
 780                 p += ALIGN8(offsetof(struct tpm2_credential_header, policy_hash_and_blob) +
 781                             le32toh(t->blob_size) +
 782                             le32toh(t->policy_hash_size));
 783 #else
 784                 return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Credential requires TPM2 support, but TPM2 support not available.");
 785 #endif
 786         }
 787
 788         if (with_host_key) {
 789                 r = get_credential_host_secret(
 790                                 0,
 791                                 &host_key,
 792                                 &host_key_size);
 793                 if (r < 0)
 794                         return log_error_errno(r, "Failed to determine local credential key: %m");
 795         }
 796
 797         sha256_hash_host_and_tpm2_key(host_key, host_key_size, tpm2_key, tpm2_key_size, md);
 798
 799         assert_se(cc = EVP_aes_256_gcm());
 800
 801         /* Make sure cipher expectations match the header */
 802         if (EVP_CIPHER_key_length(cc) != (int) le32toh(h->key_size))
 803                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected key size in header.");
 804         if (EVP_CIPHER_block_size(cc) != (int) le32toh(h->block_size))
 805                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected block size in header.");
 806
 807         context = EVP_CIPHER_CTX_new();
 808         if (!context)
 809                 return log_error_errno(SYNTHETIC_ERRNO(ENOMEM), "Failed to allocate decryption object: %s",
 810                                        ERR_error_string(ERR_get_error(), NULL));
 811
 812         if (EVP_DecryptInit_ex(context, cc, NULL, NULL, NULL) != 1)
 813                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to initialize decryption context: %s",
 814                                        ERR_error_string(ERR_get_error(), NULL));
 815
 816         if (EVP_CIPHER_CTX_ctrl(context, EVP_CTRL_GCM_SET_IVLEN, le32toh(h->iv_size), NULL) != 1)
 817                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to set IV size on decryption context: %s",
 818                                        ERR_error_string(ERR_get_error(), NULL));
 819
 820         if (EVP_DecryptInit_ex(context, NULL, NULL, md, h->iv) != 1)
 821                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to set IV and key: %s",
 822                                        ERR_error_string(ERR_get_error(), NULL));
 823
 824         if (EVP_DecryptUpdate(context, NULL, &added, input, p) != 1)
 825                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to write AAD data: %s",
 826                                        ERR_error_string(ERR_get_error(), NULL));
 827
 828         plaintext = malloc(input_size - p - le32toh(h->tag_size));
 829         if (!plaintext)
 830                 return -ENOMEM;
 831
 832         if (EVP_DecryptUpdate(
 833                             context,
 834                             plaintext,
 835                             &added,
 836                             (uint8_t*) input + p,
 837                             input_size - p - le32toh(h->tag_size)) != 1)
 838                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to decrypt data: %s",
 839                                        ERR_error_string(ERR_get_error(), NULL));
 840
 841         assert(added >= 0);
 842         assert((size_t) added <= input_size - p - le32toh(h->tag_size));
 843         plaintext_size = added;
 844
 845         if (EVP_CIPHER_CTX_ctrl(context, EVP_CTRL_GCM_SET_TAG, le32toh(h->tag_size), (uint8_t*) input + input_size - le32toh(h->tag_size)) != 1)
 846                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to set tag: %s",
 847                                        ERR_error_string(ERR_get_error(), NULL));
 848
 849         if (EVP_DecryptFinal_ex(context, (uint8_t*) plaintext + plaintext_size, &added) != 1)
 850                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Decryption failed (incorrect key?): %s",
 851                                        ERR_error_string(ERR_get_error(), NULL));
 852
 853         plaintext_size += added;
 854
 855         if (plaintext_size < ALIGN8(offsetof(struct metadata_credential_header, name)))
 856                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Metadata header incomplete.");
 857
 858         m = plaintext;
 859
 860         if (le64toh(m->timestamp) != USEC_INFINITY &&
 861             le64toh(m->not_after) != USEC_INFINITY &&
 862             le64toh(m->timestamp) >= le64toh(m->not_after))
 863                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Timestamps of credential are not in order, refusing.");
 864
 865         if (le32toh(m->name_size) > CREDENTIAL_NAME_MAX)
 866                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Embedded credential name too long, refusing.");
 867
 868         hs = ALIGN8(offsetof(struct metadata_credential_header, name) + le32toh(m->name_size));
 869         if (plaintext_size < hs)
 870                 return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Metadata header incomplete.");
 871
 872         if (le32toh(m->name_size) > 0) {
 873                 _cleanup_free_ char *embedded_name = NULL;
 874
 875                 if (memchr(m->name, 0, le32toh(m->name_size)))
 876                         return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Embedded credential name contains NUL byte, refusing.");
 877
 878                 embedded_name = memdup_suffix0(m->name, le32toh(m->name_size));
 879                 if (!embedded_name)
 880                         return log_oom();
 881
 882                 if (!credential_name_valid(embedded_name))
 883                         return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Embedded credential name is not valid, refusing.");
 884
 885                 if (validate_name && !streq(embedded_name, validate_name)) {
 886
 887                         r = getenv_bool_secure("SYSTEMD_CREDENTIAL_VALIDATE_NAME");
 888                         if (r < 0 && r != -ENXIO)
 889                                 log_debug_errno(r, "Failed to parse $SYSTEMD_CREDENTIAL_VALIDATE_NAME: %m");
 890                         if (r != 0)
 891                                 return log_error_errno(SYNTHETIC_ERRNO(EREMOTE), "Embedded credential name '%s' does not match filename '%s', refusing.", embedded_name, validate_name);
 892
 893                         log_debug("Embedded credential name '%s' does not match expected name '%s', but configured to use credential anyway.", embedded_name, validate_name);
 894                 }
 895         }
 896
 897         if (validate_timestamp != USEC_INFINITY) {
 898                 if (le64toh(m->timestamp) != USEC_INFINITY && le64toh(m->timestamp) > validate_timestamp)
 899                         log_debug("Credential timestamp is from the future, assuming clock skew.");
 900
 901                 if (le64toh(m->not_after) != USEC_INFINITY && le64toh(m->not_after) < validate_timestamp) {
 902
 903                         r = getenv_bool_secure("SYSTEMD_CREDENTIAL_VALIDATE_NOT_AFTER");
 904                         if (r < 0 && r != -ENXIO)
 905                                 log_debug_errno(r, "Failed to parse $SYSTEMD_CREDENTIAL_VALIDATE_NOT_AFTER: %m");
 906                         if (r != 0)
 907                                 return log_error_errno(SYNTHETIC_ERRNO(ESTALE), "Credential's time passed, refusing to use.");
 908
 909                         log_debug("Credential not-after timestamp has passed, but configured to use credential anyway.");
 910                 }
 911         }
 912
 913         if (ret) {
 914                 char *without_metadata;
 915
 916                 without_metadata = memdup((uint8_t*) plaintext + hs, plaintext_size - hs);
 917                 if (!without_metadata)
 918                         return log_oom();
 919
 920                 *ret = without_metadata;
 921         }
 922
 923         if (ret_size)
 924                 *ret_size = plaintext_size - hs;
 925
 926         return 0;
 927 }
 928
 929 #else
 930
 931 int get_credential_host_secret(CredentialSecretFlags flags, void **ret, size_t *ret_size) {
 932         return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Support for encrypted credentials not available.");
 933 }
 934
 935 int encrypt_credential_and_warn(sd_id128_t with_key, const char *name, usec_t timestamp, usec_t not_after, const char *tpm2_device, uint32_t tpm2_pcr_mask, const void *input, size_t input_size, void **ret, size_t *ret_size) {
 936         return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Support for encrypted credentials not available.");
 937 }
 938
 939 int decrypt_credential_and_warn(const char *validate_name, usec_t validate_timestamp, const char *tpm2_device, const void *input, size_t input_size, void **ret, size_t *ret_size) {
 940         return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Support for encrypted credentials not available.");
 941 }
 942
 943 #endif