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Message-ID: <CAOi1vP9QRWKoQuYHynTXuupJ=VHhLLtN3s2FE6a+gG6gvrA6SQ@mail.gmail.com>
Date: Thu, 4 Sep 2025 12:24:08 +0200
From: Ilya Dryomov <idryomov@...il.com>
To: Eric Biggers <ebiggers@...nel.org>
Cc: ceph-devel@...r.kernel.org, Xiubo Li <xiubli@...hat.com>,
linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] libceph: Use HMAC-SHA256 library instead of crypto_shash
On Thu, Jul 31, 2025 at 9:03 PM Eric Biggers <ebiggers@...nel.org> wrote:
>
> Use the HMAC-SHA256 library functions instead of crypto_shash. This is
> simpler and faster.
>
> Signed-off-by: Eric Biggers <ebiggers@...nel.org>
> ---
> include/linux/ceph/messenger.h | 4 +-
> net/ceph/Kconfig | 3 +-
> net/ceph/messenger_v2.c | 77 ++++++++++------------------------
> 3 files changed, 26 insertions(+), 58 deletions(-)
>
> diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
> index 1717cc57cdacd..4b49592a738fc 100644
> --- a/include/linux/ceph/messenger.h
> +++ b/include/linux/ceph/messenger.h
> @@ -1,9 +1,10 @@
> /* SPDX-License-Identifier: GPL-2.0 */
> #ifndef __FS_CEPH_MESSENGER_H
> #define __FS_CEPH_MESSENGER_H
>
> +#include <crypto/sha2.h>
> #include <linux/bvec.h>
> #include <linux/crypto.h>
> #include <linux/kref.h>
> #include <linux/mutex.h>
> #include <linux/net.h>
> @@ -410,11 +411,12 @@ struct ceph_connection_v2_info {
>
> struct ceph_frame_desc in_desc;
> struct ceph_msg_data_cursor in_cursor;
> struct ceph_msg_data_cursor out_cursor;
>
> - struct crypto_shash *hmac_tfm; /* post-auth signature */
> + struct hmac_sha256_key hmac_key; /* post-auth signature */
> + bool hmac_key_set;
> struct crypto_aead *gcm_tfm; /* on-wire encryption */
> struct aead_request *gcm_req;
> struct crypto_wait gcm_wait;
> struct ceph_gcm_nonce in_gcm_nonce;
> struct ceph_gcm_nonce out_gcm_nonce;
> diff --git a/net/ceph/Kconfig b/net/ceph/Kconfig
> index 0aa21fcbf6ece..ea60e3ef08343 100644
> --- a/net/ceph/Kconfig
> +++ b/net/ceph/Kconfig
> @@ -4,12 +4,11 @@ config CEPH_LIB
> depends on INET
> select CRC32
> select CRYPTO_AES
> select CRYPTO_CBC
> select CRYPTO_GCM
> - select CRYPTO_HMAC
> - select CRYPTO_SHA256
> + select CRYPTO_LIB_SHA256
> select CRYPTO
> select KEYS
> default n
> help
> Choose Y or M here to include cephlib, which provides the
> diff --git a/net/ceph/messenger_v2.c b/net/ceph/messenger_v2.c
> index 5483b4eed94e1..c54c8b5a65261 100644
> --- a/net/ceph/messenger_v2.c
> +++ b/net/ceph/messenger_v2.c
> @@ -707,11 +707,11 @@ static int setup_crypto(struct ceph_connection *con,
> unsigned int noio_flag;
> int ret;
>
> dout("%s con %p con_mode %d session_key_len %d con_secret_len %d\n",
> __func__, con, con->v2.con_mode, session_key_len, con_secret_len);
> - WARN_ON(con->v2.hmac_tfm || con->v2.gcm_tfm || con->v2.gcm_req);
> + WARN_ON(con->v2.hmac_key_set || con->v2.gcm_tfm || con->v2.gcm_req);
>
> if (con->v2.con_mode != CEPH_CON_MODE_CRC &&
> con->v2.con_mode != CEPH_CON_MODE_SECURE) {
> pr_err("bad con_mode %d\n", con->v2.con_mode);
> return -EINVAL;
> @@ -721,26 +721,12 @@ static int setup_crypto(struct ceph_connection *con,
> WARN_ON(con->v2.con_mode != CEPH_CON_MODE_CRC);
> WARN_ON(con_secret_len);
> return 0; /* auth_none */
> }
>
> - noio_flag = memalloc_noio_save();
> - con->v2.hmac_tfm = crypto_alloc_shash("hmac(sha256)", 0, 0);
> - memalloc_noio_restore(noio_flag);
> - if (IS_ERR(con->v2.hmac_tfm)) {
> - ret = PTR_ERR(con->v2.hmac_tfm);
> - con->v2.hmac_tfm = NULL;
> - pr_err("failed to allocate hmac tfm context: %d\n", ret);
> - return ret;
> - }
> -
> - ret = crypto_shash_setkey(con->v2.hmac_tfm, session_key,
> - session_key_len);
> - if (ret) {
> - pr_err("failed to set hmac key: %d\n", ret);
> - return ret;
> - }
> + hmac_sha256_preparekey(&con->v2.hmac_key, session_key, session_key_len);
> + con->v2.hmac_key_set = true;
>
> if (con->v2.con_mode == CEPH_CON_MODE_CRC) {
> WARN_ON(con_secret_len);
> return 0; /* auth_x, plain mode */
> }
> @@ -791,42 +777,30 @@ static int setup_crypto(struct ceph_connection *con,
> con_secret + CEPH_GCM_KEY_LEN + CEPH_GCM_IV_LEN,
> CEPH_GCM_IV_LEN);
> return 0; /* auth_x, secure mode */
> }
>
> -static int ceph_hmac_sha256(struct ceph_connection *con,
> - const struct kvec *kvecs, int kvec_cnt, u8 *hmac)
> +static void ceph_hmac_sha256(struct ceph_connection *con,
> + const struct kvec *kvecs, int kvec_cnt,
> + u8 hmac[SHA256_DIGEST_SIZE])
> {
> - SHASH_DESC_ON_STACK(desc, con->v2.hmac_tfm); /* tfm arg is ignored */
> - int ret;
> + struct hmac_sha256_ctx ctx;
> int i;
>
> - dout("%s con %p hmac_tfm %p kvec_cnt %d\n", __func__, con,
> - con->v2.hmac_tfm, kvec_cnt);
> + dout("%s con %p hmac_key_set %d kvec_cnt %d\n", __func__, con,
> + con->v2.hmac_key_set, kvec_cnt);
>
> - if (!con->v2.hmac_tfm) {
> + if (!con->v2.hmac_key_set) {
> memset(hmac, 0, SHA256_DIGEST_SIZE);
> - return 0; /* auth_none */
> + return; /* auth_none */
> }
>
> - desc->tfm = con->v2.hmac_tfm;
> - ret = crypto_shash_init(desc);
> - if (ret)
> - goto out;
> -
> - for (i = 0; i < kvec_cnt; i++) {
> - ret = crypto_shash_update(desc, kvecs[i].iov_base,
> - kvecs[i].iov_len);
> - if (ret)
> - goto out;
> - }
> -
> - ret = crypto_shash_final(desc, hmac);
> -
> -out:
> - shash_desc_zero(desc);
> - return ret; /* auth_x, both plain and secure modes */
> + /* auth_x, both plain and secure modes */
> + hmac_sha256_init(&ctx, &con->v2.hmac_key);
> + for (i = 0; i < kvec_cnt; i++)
> + hmac_sha256_update(&ctx, kvecs[i].iov_base, kvecs[i].iov_len);
> + hmac_sha256_final(&ctx, hmac);
> }
>
> static void gcm_inc_nonce(struct ceph_gcm_nonce *nonce)
> {
> u64 counter;
> @@ -1453,21 +1427,18 @@ static int prepare_auth_request_more(struct ceph_connection *con,
> }
>
> static int prepare_auth_signature(struct ceph_connection *con)
> {
> void *buf;
> - int ret;
>
> buf = alloc_conn_buf(con, head_onwire_len(SHA256_DIGEST_SIZE,
> con_secure(con)));
> if (!buf)
> return -ENOMEM;
>
> - ret = ceph_hmac_sha256(con, con->v2.in_sign_kvecs,
> - con->v2.in_sign_kvec_cnt, CTRL_BODY(buf));
> - if (ret)
> - return ret;
> + ceph_hmac_sha256(con, con->v2.in_sign_kvecs, con->v2.in_sign_kvec_cnt,
> + CTRL_BODY(buf));
>
> return prepare_control(con, FRAME_TAG_AUTH_SIGNATURE, buf,
> SHA256_DIGEST_SIZE);
> }
>
> @@ -2458,14 +2429,12 @@ static int process_auth_signature(struct ceph_connection *con,
> if (con->state != CEPH_CON_S_V2_AUTH_SIGNATURE) {
> con->error_msg = "protocol error, unexpected auth_signature";
> return -EINVAL;
> }
>
> - ret = ceph_hmac_sha256(con, con->v2.out_sign_kvecs,
> - con->v2.out_sign_kvec_cnt, hmac);
> - if (ret)
> - return ret;
> + ceph_hmac_sha256(con, con->v2.out_sign_kvecs, con->v2.out_sign_kvec_cnt,
> + hmac);
>
> ceph_decode_need(&p, end, SHA256_DIGEST_SIZE, bad);
> if (crypto_memneq(p, hmac, SHA256_DIGEST_SIZE)) {
> con->error_msg = "integrity error, bad auth signature";
> return -EBADMSG;
> @@ -3812,14 +3781,12 @@ void ceph_con_v2_reset_protocol(struct ceph_connection *con)
>
> con->v2.con_mode = CEPH_CON_MODE_UNKNOWN;
> memzero_explicit(&con->v2.in_gcm_nonce, CEPH_GCM_IV_LEN);
> memzero_explicit(&con->v2.out_gcm_nonce, CEPH_GCM_IV_LEN);
>
> - if (con->v2.hmac_tfm) {
> - crypto_free_shash(con->v2.hmac_tfm);
> - con->v2.hmac_tfm = NULL;
> - }
> + memzero_explicit(&con->v2.hmac_key, sizeof(con->v2.hmac_key));
> + con->v2.hmac_key_set = false;
Hi Eric,
Since we have hmac_key_set anyway, could the call to memzero_explicit()
be conditioned on it?
Thanks,
Ilya
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