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thunderbolt: Use HMAC-SHA256 library instead of crypto_shash

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Use the hmac_sha256_usingrawkey() library function instead of the
"hmac(sha256)" crypto_shash.  This is simpler and faster.

As a cleanup, change the input data parameters from "challenge,
sizeof(hmac)" to "challenge, sizeof(challenge)", so that the size is
being taken of the correct buffer.  This is not a functional change,
since it happens that sizeof(hmac) == sizeof(challenge).

Replace the selection of CRYPTO and CRYPTO_HASH with CRYPTO_LIB_SHA256
and CRYPTO_LIB_UTILS.  The latter is needed for crypto_memneq() which
was previously being pulled in via CRYPTO.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
This commit is contained in:
Eric Biggers 2025-07-31 12:25:45 -07:00 • committed by Mika Westerberg
parent dced755df3
commit 0eff12ce88
2 changed files with 8 additions and 40 deletions
Download patch file Download diff file Expand all files Collapse all files

4
drivers/thunderbolt/Kconfig
View file

@ -4,8 +4,8 @@ menuconfig USB4
depends on PCI
select APPLE_PROPERTIES if EFI_STUB && X86
select CRC32
select CRYPTO
select CRYPTO_HASH
select CRYPTO_LIB_SHA256
select CRYPTO_LIB_UTILS
select NVMEM
help
USB4 and Thunderbolt driver. USB4 is the public specification

44
drivers/thunderbolt/domain.c
View file

@ -12,7 +12,7 @@
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <crypto/hash.h>
#include <crypto/sha2.h>
#include <crypto/utils.h>
#include "tb.h"
@ -709,8 +709,6 @@ int tb_domain_challenge_switch_key(struct tb *tb, struct tb_switch *sw)
u8 response[TB_SWITCH_KEY_SIZE];
u8 hmac[TB_SWITCH_KEY_SIZE];
struct tb_switch *parent_sw;
struct crypto_shash *tfm;
struct shash_desc *shash;
int ret;
if (!tb->cm_ops->approve_switch || !tb->cm_ops->challenge_switch_key)
@ -726,45 +724,15 @@ int tb_domain_challenge_switch_key(struct tb *tb, struct tb_switch *sw)
if (ret)
return ret;
tfm = crypto_alloc_shash("hmac(sha256)", 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
ret = crypto_shash_setkey(tfm, sw->key, TB_SWITCH_KEY_SIZE);
if (ret)
goto err_free_tfm;
shash = kzalloc(sizeof(*shash) + crypto_shash_descsize(tfm),
GFP_KERNEL);
if (!shash) {
ret = -ENOMEM;
goto err_free_tfm;
}
shash->tfm = tfm;
memset(hmac, 0, sizeof(hmac));
ret = crypto_shash_digest(shash, challenge, sizeof(hmac), hmac);
if (ret)
goto err_free_shash;
static_assert(sizeof(hmac) == SHA256_DIGEST_SIZE);
hmac_sha256_usingrawkey(sw->key, TB_SWITCH_KEY_SIZE,
challenge, sizeof(challenge), hmac);
/* The returned HMAC must match the one we calculated */
if (crypto_memneq(response, hmac, sizeof(hmac))) {
ret = -EKEYREJECTED;
goto err_free_shash;
}
crypto_free_shash(tfm);
kfree(shash);
if (crypto_memneq(response, hmac, sizeof(hmac)))
return -EKEYREJECTED;
return tb->cm_ops->approve_switch(tb, sw);
err_free_shash:
kfree(shash);
err_free_tfm:
crypto_free_shash(tfm);
return ret;
}
/**