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-rw-r--r--src/cryptenroll/cryptenroll-tpm2.c268
1 files changed, 268 insertions, 0 deletions
diff --git a/src/cryptenroll/cryptenroll-tpm2.c b/src/cryptenroll/cryptenroll-tpm2.c
new file mode 100644
index 0000000..1e11d73
--- /dev/null
+++ b/src/cryptenroll/cryptenroll-tpm2.c
@@ -0,0 +1,268 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "alloc-util.h"
+#include "ask-password-api.h"
+#include "cryptenroll-tpm2.h"
+#include "env-util.h"
+#include "fileio.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 < sym_crypt_token_max(CRYPT_LUKS2); 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) {
+ /* Handle parsing errors of the keyslots field gracefully, since it's not 'owned' by
+ * us, but by the LUKS2 spec */
+ log_warning_errno(keyslot, "Failed to determine keyslot of JSON token %i, skipping: %m", token);
+ continue;
+ }
+
+ 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_MAX, &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 */
+}
+
+static int get_pin(char **ret_pin_str, TPM2Flags *ret_flags) {
+ _cleanup_(erase_and_freep) char *pin_str = NULL;
+ TPM2Flags flags = 0;
+ int r;
+
+ assert(ret_pin_str);
+ assert(ret_flags);
+
+ r = getenv_steal_erase("NEWPIN", &pin_str);
+ if (r < 0)
+ return log_error_errno(r, "Failed to acquire PIN from environment: %m");
+ if (r > 0)
+ flags |= TPM2_FLAGS_USE_PIN;
+ else {
+ for (size_t i = 5;; i--) {
+ _cleanup_strv_free_erase_ char **pin = NULL, **pin2 = NULL;
+
+ if (i <= 0)
+ return log_error_errno(
+ SYNTHETIC_ERRNO(ENOKEY), "Too many attempts, giving up.");
+
+ pin = strv_free_erase(pin);
+ r = ask_password_auto(
+ "Please enter TPM2 PIN:",
+ "drive-harddisk",
+ NULL,
+ "tpm2-pin",
+ "cryptenroll.tpm2-pin",
+ USEC_INFINITY,
+ 0,
+ &pin);
+ if (r < 0)
+ return log_error_errno(r, "Failed to ask for user pin: %m");
+ assert(strv_length(pin) == 1);
+
+ r = ask_password_auto(
+ "Please enter TPM2 PIN (repeat):",
+ "drive-harddisk",
+ NULL,
+ "tpm2-pin",
+ "cryptenroll.tpm2-pin",
+ USEC_INFINITY,
+ 0,
+ &pin2);
+ if (r < 0)
+ return log_error_errno(r, "Failed to ask for user pin: %m");
+ assert(strv_length(pin) == 1);
+
+ if (strv_equal(pin, pin2)) {
+ pin_str = strdup(*pin);
+ if (!pin_str)
+ return log_oom();
+ flags |= TPM2_FLAGS_USE_PIN;
+ break;
+ }
+
+ log_error("PINs didn't match, please try again!");
+ }
+ }
+
+ *ret_flags = flags;
+ *ret_pin_str = TAKE_PTR(pin_str);
+
+ return 0;
+}
+
+int enroll_tpm2(struct crypt_device *cd,
+ const void *volume_key,
+ size_t volume_key_size,
+ const char *device,
+ uint32_t hash_pcr_mask,
+ const char *pubkey_path,
+ uint32_t pubkey_pcr_mask,
+ const char *signature_path,
+ bool use_pin) {
+
+ _cleanup_(erase_and_freep) void *secret = NULL;
+ _cleanup_(json_variant_unrefp) JsonVariant *v = NULL, *signature_json = NULL;
+ _cleanup_(erase_and_freep) char *base64_encoded = NULL;
+ size_t secret_size, blob_size, hash_size, pubkey_size = 0;
+ _cleanup_free_ void *blob = NULL, *hash = NULL, *pubkey = NULL;
+ uint16_t pcr_bank, primary_alg;
+ const char *node;
+ _cleanup_(erase_and_freep) char *pin_str = NULL;
+ int r, keyslot;
+ TPM2Flags flags = 0;
+
+ assert(cd);
+ assert(volume_key);
+ assert(volume_key_size > 0);
+ assert(TPM2_PCR_MASK_VALID(hash_pcr_mask));
+ assert(TPM2_PCR_MASK_VALID(pubkey_pcr_mask));
+
+ assert_se(node = crypt_get_device_name(cd));
+
+ if (use_pin) {
+ r = get_pin(&pin_str, &flags);
+ if (r < 0)
+ return r;
+ }
+
+ r = tpm2_load_pcr_public_key(pubkey_path, &pubkey, &pubkey_size);
+ if (r < 0) {
+ if (pubkey_path || signature_path || r != -ENOENT)
+ return log_error_errno(r, "Failed read TPM PCR public key: %m");
+
+ log_debug_errno(r, "Failed to read TPM2 PCR public key, proceeding without: %m");
+ pubkey_pcr_mask = 0;
+ } else if (signature_path) {
+ /* Also try to load the signature JSON object, to verify that our enrollment will work.
+ * This is optional however, skip it if it's not explicitly provided. */
+
+ r = tpm2_load_pcr_signature(signature_path, &signature_json);
+ if (r < 0)
+ return log_debug_errno(r, "Failed to read TPM PCR signature: %m");
+ }
+
+ r = tpm2_seal(device,
+ hash_pcr_mask,
+ pubkey, pubkey_size,
+ pubkey_pcr_mask,
+ pin_str,
+ &secret, &secret_size,
+ &blob, &blob_size,
+ &hash, &hash_size,
+ &pcr_bank,
+ &primary_alg);
+ 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.*/
+ if (!pubkey || signature_json) {
+ _cleanup_(erase_and_freep) void *secret2 = NULL;
+ size_t secret2_size;
+
+ log_debug("Unsealing for verification...");
+ r = tpm2_unseal(device,
+ hash_pcr_mask,
+ pcr_bank,
+ pubkey, pubkey_size,
+ pubkey_pcr_mask,
+ signature_json,
+ pin_str,
+ primary_alg,
+ 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,
+ hash_pcr_mask,
+ pcr_bank,
+ pubkey, pubkey_size,
+ pubkey_pcr_mask,
+ primary_alg,
+ blob, blob_size,
+ hash, hash_size,
+ flags,
+ &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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-12 23:17:21 +0000