123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184 |
- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * GHASH: hash function for GCM (Galois/Counter Mode).
- *
- * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <[email protected]>
- * Copyright (c) 2009 Intel Corp.
- * Author: Huang Ying <[email protected]>
- */
- /*
- * GHASH is a keyed hash function used in GCM authentication tag generation.
- *
- * 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.
- *
- * 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>
- #include <crypto/gf128mul.h>
- #include <crypto/ghash.h>
- #include <crypto/internal/hash.h>
- #include <linux/crypto.h>
- #include <linux/init.h>
- #include <linux/kernel.h>
- #include <linux/module.h>
- static int ghash_init(struct shash_desc *desc)
- {
- struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
- memset(dctx, 0, sizeof(*dctx));
- return 0;
- }
- static int ghash_setkey(struct crypto_shash *tfm,
- const u8 *key, unsigned int keylen)
- {
- struct ghash_ctx *ctx = crypto_shash_ctx(tfm);
- be128 k;
- if (keylen != GHASH_BLOCK_SIZE)
- return -EINVAL;
- if (ctx->gf128)
- gf128mul_free_4k(ctx->gf128);
- BUILD_BUG_ON(sizeof(k) != GHASH_BLOCK_SIZE);
- memcpy(&k, key, GHASH_BLOCK_SIZE); /* avoid violating alignment rules */
- ctx->gf128 = gf128mul_init_4k_lle(&k);
- memzero_explicit(&k, GHASH_BLOCK_SIZE);
- if (!ctx->gf128)
- return -ENOMEM;
- return 0;
- }
- static int ghash_update(struct shash_desc *desc,
- const u8 *src, unsigned int srclen)
- {
- struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
- struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
- u8 *dst = dctx->buffer;
- if (dctx->bytes) {
- int n = min(srclen, dctx->bytes);
- u8 *pos = dst + (GHASH_BLOCK_SIZE - dctx->bytes);
- dctx->bytes -= n;
- srclen -= n;
- while (n--)
- *pos++ ^= *src++;
- if (!dctx->bytes)
- gf128mul_4k_lle((be128 *)dst, ctx->gf128);
- }
- while (srclen >= GHASH_BLOCK_SIZE) {
- crypto_xor(dst, src, GHASH_BLOCK_SIZE);
- gf128mul_4k_lle((be128 *)dst, ctx->gf128);
- src += GHASH_BLOCK_SIZE;
- srclen -= GHASH_BLOCK_SIZE;
- }
- if (srclen) {
- dctx->bytes = GHASH_BLOCK_SIZE - srclen;
- while (srclen--)
- *dst++ ^= *src++;
- }
- return 0;
- }
- static void ghash_flush(struct ghash_ctx *ctx, struct ghash_desc_ctx *dctx)
- {
- u8 *dst = dctx->buffer;
- if (dctx->bytes) {
- u8 *tmp = dst + (GHASH_BLOCK_SIZE - dctx->bytes);
- while (dctx->bytes--)
- *tmp++ ^= 0;
- gf128mul_4k_lle((be128 *)dst, ctx->gf128);
- }
- dctx->bytes = 0;
- }
- static int ghash_final(struct shash_desc *desc, u8 *dst)
- {
- struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
- struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
- u8 *buf = dctx->buffer;
- ghash_flush(ctx, dctx);
- memcpy(dst, buf, GHASH_BLOCK_SIZE);
- return 0;
- }
- static void ghash_exit_tfm(struct crypto_tfm *tfm)
- {
- struct ghash_ctx *ctx = crypto_tfm_ctx(tfm);
- if (ctx->gf128)
- gf128mul_free_4k(ctx->gf128);
- }
- static struct shash_alg ghash_alg = {
- .digestsize = GHASH_DIGEST_SIZE,
- .init = ghash_init,
- .update = ghash_update,
- .final = ghash_final,
- .setkey = ghash_setkey,
- .descsize = sizeof(struct ghash_desc_ctx),
- .base = {
- .cra_name = "ghash",
- .cra_driver_name = "ghash-generic",
- .cra_priority = 100,
- .cra_blocksize = GHASH_BLOCK_SIZE,
- .cra_ctxsize = sizeof(struct ghash_ctx),
- .cra_module = THIS_MODULE,
- .cra_exit = ghash_exit_tfm,
- },
- };
- static int __init ghash_mod_init(void)
- {
- return crypto_register_shash(&ghash_alg);
- }
- static void __exit ghash_mod_exit(void)
- {
- crypto_unregister_shash(&ghash_alg);
- }
- subsys_initcall(ghash_mod_init);
- module_exit(ghash_mod_exit);
- MODULE_LICENSE("GPL");
- MODULE_DESCRIPTION("GHASH hash function");
- MODULE_ALIAS_CRYPTO("ghash");
- MODULE_ALIAS_CRYPTO("ghash-generic");
|