The documentation in the file header is duplicate documentation to the documentation Documentation/security/tpm/tpm-security.rst and kdoc comments attached to the exported functions in 'tpm2-sessions.c'. Remove it as maintaining it would be just a waster of time and resources. Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> --- v3: - Refine the commit message. v2: - Refine the commit message. --- drivers/char/tpm/tpm2-sessions.c | 65 -------------------------------- 1 file changed, 65 deletions(-) diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c index 44f60730cff4..6cc1ea81c57c 100644 --- a/drivers/char/tpm/tpm2-sessions.c +++ b/drivers/char/tpm/tpm2-sessions.c @@ -1,71 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 - /* * Copyright (C) 2018 James.Bottomley@xxxxxxxxxxxxxxxxxxxxx - * - * Cryptographic helper routines for handling TPM2 sessions for - * authorization HMAC and request response encryption. - * - * The idea is to ensure that every TPM command is HMAC protected by a - * session, meaning in-flight tampering would be detected and in - * addition all sensitive inputs and responses should be encrypted. - * - * The basic way this works is to use a TPM feature called salted - * sessions where a random secret used in session construction is - * encrypted to the public part of a known TPM key. The problem is we - * have no known keys, so initially a primary Elliptic Curve key is - * derived from the NULL seed (we use EC because most TPMs generate - * these keys much faster than RSA ones). The curve used is NIST_P256 - * because that's now mandated to be present in 'TCG TPM v2.0 - * Provisioning Guidance' - * - * Threat problems: the initial TPM2_CreatePrimary is not (and cannot - * be) session protected, so a clever Man in the Middle could return a - * public key they control to this command and from there intercept - * and decode all subsequent session based transactions. The kernel - * cannot mitigate this threat but, after boot, userspace can get - * proof this has not happened by asking the TPM to certify the NULL - * key. This certification would chain back to the TPM Endorsement - * Certificate and prove the NULL seed primary had not been tampered - * with and thus all sessions must have been cryptographically secure. - * To assist with this, the initial NULL seed public key name is made - * available in a sysfs file. - * - * Use of these functions: - * - * The design is all the crypto, hash and hmac gunk is confined in this - * file and never needs to be seen even by the kernel internal user. To - * the user there's an init function tpm2_sessions_init() that needs to - * be called once per TPM which generates the NULL seed primary key. - * - * These are the usage functions: - * - * tpm2_start_auth_session() which allocates the opaque auth structure - * and gets a session from the TPM. This must be called before - * any of the following functions. The session is protected by a - * session_key which is derived from a random salt value - * encrypted to the NULL seed. - * tpm2_end_auth_session() kills the session and frees the resources. - * Under normal operation this function is done by - * tpm_buf_check_hmac_response(), so this is only to be used on - * error legs where the latter is not executed. - * tpm_buf_append_name() to add a handle to the buffer. This must be - * used in place of the usual tpm_buf_append_u32() for adding - * handles because handles have to be processed specially when - * calculating the HMAC. In particular, for NV, volatile and - * permanent objects you now need to provide the name. - * tpm_buf_append_hmac_session() which appends the hmac session to the - * buf in the same way tpm_buf_append_auth does(). - * tpm_buf_fill_hmac_session() This calculates the correct hash and - * places it in the buffer. It must be called after the complete - * command buffer is finalized so it can fill in the correct HMAC - * based on the parameters. - * tpm_buf_check_hmac_response() which checks the session response in - * the buffer and calculates what it should be. If there's a - * mismatch it will log a warning and return an error. If - * tpm_buf_append_hmac_session() did not specify - * TPM_SA_CONTINUE_SESSION then the session will be closed (if it - * hasn't been consumed) and the auth structure freed. */ #include "tpm.h" -- 2.46.0
