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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include "alloc-util.h"
#include "cryptenroll-tpm2.h"
#include "hexdecoct.h"
#include "json.h"
#include "memory-util.h"
#include "tpm2-util.h"
static int search_policy_hash(
struct crypt_device *cd,
const void *hash,
size_t hash_size) {
int r;
assert(cd);
assert(hash || hash_size == 0);
if (hash_size == 0)
return 0;
for (int token = 0; token < LUKS2_TOKENS_MAX; token ++) {
_cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
_cleanup_free_ void *thash = NULL;
size_t thash_size = 0;
int keyslot;
JsonVariant *w;
r = cryptsetup_get_token_as_json(cd, token, "systemd-tpm2", &v);
if (IN_SET(r, -ENOENT, -EINVAL, -EMEDIUMTYPE))
continue;
if (r < 0)
return log_error_errno(r, "Failed to read JSON token data off disk: %m");
keyslot = cryptsetup_get_keyslot_from_token(v);
if (keyslot < 0)
return log_error_errno(keyslot, "Failed to determine keyslot of JSON token: %m");
w = json_variant_by_key(v, "tpm2-policy-hash");
if (!w || !json_variant_is_string(w))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"TPM2 token data lacks 'tpm2-policy-hash' field.");
r = unhexmem(json_variant_string(w), (size_t) -1, &thash, &thash_size);
if (r < 0)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Invalid base64 data in 'tpm2-policy-hash' field.");
if (memcmp_nn(hash, hash_size, thash, thash_size) == 0)
return keyslot; /* Found entry with same hash. */
}
return -ENOENT; /* Not found */
}
int enroll_tpm2(struct crypt_device *cd,
const void *volume_key,
size_t volume_key_size,
const char *device,
uint32_t pcr_mask) {
_cleanup_(erase_and_freep) void *secret = NULL, *secret2 = NULL;
_cleanup_(json_variant_unrefp) JsonVariant *v = NULL, *a = NULL;
_cleanup_(erase_and_freep) char *base64_encoded = NULL;
size_t secret_size, secret2_size, blob_size, hash_size;
_cleanup_free_ void *blob = NULL, *hash = NULL;
const char *node;
int r, keyslot;
assert(cd);
assert(volume_key);
assert(volume_key_size > 0);
assert(pcr_mask < (1U << TPM2_PCRS_MAX)); /* Support 24 PCR banks */
assert_se(node = crypt_get_device_name(cd));
r = tpm2_seal(device, pcr_mask, &secret, &secret_size, &blob, &blob_size, &hash, &hash_size);
if (r < 0)
return r;
/* Let's see if we already have this specific PCR policy hash enrolled, if so, exit early. */
r = search_policy_hash(cd, hash, hash_size);
if (r == -ENOENT)
log_debug_errno(r, "PCR policy hash not yet enrolled, enrolling now.");
else if (r < 0)
return r;
else {
log_info("This PCR set is already enrolled, executing no operation.");
return r; /* return existing keyslot, so that wiping won't kill it */
}
/* Quick verification that everything is in order, we are not in a hurry after all. */
log_debug("Unsealing for verification...");
r = tpm2_unseal(device, pcr_mask, blob, blob_size, hash, hash_size, &secret2, &secret2_size);
if (r < 0)
return r;
if (memcmp_nn(secret, secret_size, secret2, secret2_size) != 0)
return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE), "TPM2 seal/unseal verification failed.");
/* let's base64 encode the key to use, for compat with homed (and it's easier to every type it in by keyboard, if that might end up being necessary. */
r = base64mem(secret, secret_size, &base64_encoded);
if (r < 0)
return log_error_errno(r, "Failed to base64 encode secret key: %m");
r = cryptsetup_set_minimal_pbkdf(cd);
if (r < 0)
return log_error_errno(r, "Failed to set minimal PBKDF: %m");
keyslot = crypt_keyslot_add_by_volume_key(
cd,
CRYPT_ANY_SLOT,
volume_key,
volume_key_size,
base64_encoded,
strlen(base64_encoded));
if (keyslot < 0)
return log_error_errno(keyslot, "Failed to add new TPM2 key to %s: %m", node);
r = tpm2_make_luks2_json(keyslot, pcr_mask, blob, blob_size, hash, hash_size, &v);
if (r < 0)
return log_error_errno(r, "Failed to prepare TPM2 JSON token object: %m");
r = cryptsetup_add_token_json(cd, v);
if (r < 0)
return log_error_errno(r, "Failed to add TPM2 JSON token to LUKS2 header: %m");
log_info("New TPM2 token enrolled as key slot %i.", keyslot);
return keyslot;
}
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