tpm2-util: return better errors if we try to unlock a tpm key on the wrong tpm

Let's improve error handling in case one tries to unlock a TPM2 locked
volume on a different machine via TPM than it was originally enrolled
on. Let's recognize this case and print a clearer error message.

src/cryptsetup/cryptsetup-tokens/luks2-tpm2.c

@@ -109,6 +109,8 @@ int acquire_luks2_key(
                         n_policy_hash,
                         srk,
                         ret_decrypted_key);
+        if (r == -EREMOTE)
+                return log_error_errno(r, "TPM key integrity check failed. Key enrolled in superblock most likely does not belong to this TPM.");
         if (r < 0)
                 return log_error_errno(r, "Failed to unseal secret using TPM2: %m");
 

src/shared/creds-util.c

@@ -1355,6 +1355,8 @@ int decrypt_credential_and_warn(
                                 /* n_policy_hash= */ 1,
                                 /* srk= */ NULL,
                                 &tpm2_key);
+                if (r == -EREMOTE)
+                        return log_error_errno(r, "TPM key integrity check failed. Key enrolled in superblock most likely does not belong to this TPM.");
                 if (r < 0)
                         return log_error_errno(r, "Failed to unseal secret using TPM2: %m");
 #else

src/shared/cryptsetup-tpm2.c

@@ -167,6 +167,8 @@ int acquire_tpm2_key(
                                 n_policy_hash,
                                 srk,
                                 ret_decrypted_key);
+                if (r == -EREMOTE)
+                        return log_error_errno(r, "TPM key integrity check failed. Key enrolled in superblock most likely does not belong to this TPM.");
                 if (r < 0)
                         return log_error_errno(r, "Failed to unseal secret using TPM2: %m");
 
@@ -215,6 +217,8 @@ int acquire_tpm2_key(
                                 n_policy_hash,
                                 srk,
                                 ret_decrypted_key);
+                if (r == -EREMOTE)
+                        return log_error_errno(r, "TPM key integrity check failed. Key enrolled in superblock most likely does not belong to this TPM.");
                 if (r < 0) {
                         log_error_errno(r, "Failed to unseal secret using TPM2: %m");
 

src/shared/tpm2-util.c

@@ -2283,6 +2283,9 @@ int tpm2_load(
         if (rc == TPM2_RC_LOCKOUT)
                 return log_debug_errno(SYNTHETIC_ERRNO(ENOLCK),
                                        "TPM2 device is in dictionary attack lockout mode.");
+        if ((rc & ~(TPM2_RC_N_MASK|TPM2_RC_P)) == TPM2_RC_INTEGRITY) /* Return a recognizable error if this key does not belong to the local TPM */
+                return log_debug_errno(SYNTHETIC_ERRNO(EREMOTE),
+                                       "Key invalid or does not belong to current TPM.");
         if (rc != TSS2_RC_SUCCESS)
                 return log_debug_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
                                        "Failed to load key into TPM: %s", sym_Tss2_RC_Decode(rc));