From 244b2c5ca8b14627e4a17755e5922221e121c771 Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Wed, 09 Oct 2024 06:15:07 +0000
Subject: [PATCH] change system file
---
kernel/crypto/ghash-generic.c | 40 ++++++++++++++++++++++++++++++----------
1 files changed, 30 insertions(+), 10 deletions(-)
diff --git a/kernel/crypto/ghash-generic.c b/kernel/crypto/ghash-generic.c
index 591b52d..c70d163 100644
--- a/kernel/crypto/ghash-generic.c
+++ b/kernel/crypto/ghash-generic.c
@@ -1,15 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0-only
/*
- * GHASH: digest algorithm for GCM (Galois/Counter Mode).
+ * GHASH: hash function for GCM (Galois/Counter Mode).
*
* Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi>
* Copyright (c) 2009 Intel Corp.
* Author: Huang Ying <ying.huang@intel.com>
+ */
+
+/*
+ * GHASH is a keyed hash function used in GCM authentication tag generation.
*
- * The algorithm implementation is copied from gcm.c.
+ * The original GCM paper [1] presents GHASH as a function GHASH(H, A, C) which
+ * takes a 16-byte hash key H, additional authenticated data A, and a ciphertext
+ * C. It formats A and C into a single byte string X, interprets X as a
+ * polynomial over GF(2^128), and evaluates this polynomial at the point H.
*
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 as published
- * by the Free Software Foundation.
+ * However, the NIST standard for GCM [2] presents GHASH as GHASH(H, X) where X
+ * is the already-formatted byte string containing both A and C.
+ *
+ * "ghash" in the Linux crypto API uses the 'X' (pre-formatted) convention,
+ * since the API supports only a single data stream per hash. Thus, the
+ * formatting of 'A' and 'C' is done in the "gcm" template, not in "ghash".
+ *
+ * The reason "ghash" is separate from "gcm" is to allow "gcm" to use an
+ * accelerated "ghash" when a standalone accelerated "gcm(aes)" is unavailable.
+ * It is generally inappropriate to use "ghash" for other purposes, since it is
+ * an "ε-almost-XOR-universal hash function", not a cryptographic hash function.
+ * It can only be used securely in crypto modes specially designed to use it.
+ *
+ * [1] The Galois/Counter Mode of Operation (GCM)
+ * (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.694.695&rep=rep1&type=pdf)
+ * [2] Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC
+ * (https://csrc.nist.gov/publications/detail/sp/800-38d/final)
*/
#include <crypto/algapi.h>
@@ -36,10 +58,8 @@
struct ghash_ctx *ctx = crypto_shash_ctx(tfm);
be128 k;
- if (keylen != GHASH_BLOCK_SIZE) {
- crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
+ if (keylen != GHASH_BLOCK_SIZE)
return -EINVAL;
- }
if (ctx->gf128)
gf128mul_free_4k(ctx->gf128);
@@ -155,10 +175,10 @@
crypto_unregister_shash(&ghash_alg);
}
-module_init(ghash_mod_init);
+subsys_initcall(ghash_mod_init);
module_exit(ghash_mod_exit);
MODULE_LICENSE("GPL");
-MODULE_DESCRIPTION("GHASH Message Digest Algorithm");
+MODULE_DESCRIPTION("GHASH hash function");
MODULE_ALIAS_CRYPTO("ghash");
MODULE_ALIAS_CRYPTO("ghash-generic");
--
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