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Message-ID: <aJIKH3-fRizRV8fi@kernel.org>
Date: Tue, 5 Aug 2025 16:41:58 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Eric Biggers <ebiggers@...nel.org>
Cc: keyrings@...r.kernel.org, David Howells <dhowells@...hat.com>,
Mimi Zohar <zohar@...ux.ibm.com>, linux-integrity@...r.kernel.org,
linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KEYS: encrypted: Use SHA-256 library instead of
crypto_shash
On Thu, Jul 31, 2025 at 11:47:47AM -0700, Eric Biggers wrote:
> Instead of the "sha256" crypto_shash, just use sha256(). Similarly,
> instead of the "hmac(sha256)" crypto_shash, just use
> hmac_sha256_usingrawkey(). This is simpler and faster.
>
> Signed-off-by: Eric Biggers <ebiggers@...nel.org>
Yeah, fully agree.
Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
David, will you pick this?
BR, Jarkko
> ---
> security/keys/Kconfig | 3 +-
> security/keys/encrypted-keys/encrypted.c | 63 ++++--------------------
> 2 files changed, 11 insertions(+), 55 deletions(-)
>
> diff --git a/security/keys/Kconfig b/security/keys/Kconfig
> index d4f5fc1e72638..64477e2c4a212 100644
> --- a/security/keys/Kconfig
> +++ b/security/keys/Kconfig
> @@ -85,14 +85,13 @@ endif
>
> config ENCRYPTED_KEYS
> tristate "ENCRYPTED KEYS"
> depends on KEYS
> select CRYPTO
> - select CRYPTO_HMAC
> select CRYPTO_AES
> select CRYPTO_CBC
> - select CRYPTO_SHA256
> + select CRYPTO_LIB_SHA256
> select CRYPTO_RNG
> help
> This option provides support for create/encrypting/decrypting keys
> in the kernel. Encrypted keys are instantiated using kernel
> generated random numbers or provided decrypted data, and are
> diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
> index 831cb84fd75a1..513c09e2b01cf 100644
> --- a/security/keys/encrypted-keys/encrypted.c
> +++ b/security/keys/encrypted-keys/encrypted.c
> @@ -25,22 +25,19 @@
> #include <linux/random.h>
> #include <linux/rcupdate.h>
> #include <linux/scatterlist.h>
> #include <linux/ctype.h>
> #include <crypto/aes.h>
> -#include <crypto/hash.h>
> #include <crypto/sha2.h>
> #include <crypto/skcipher.h>
> #include <crypto/utils.h>
>
> #include "encrypted.h"
> #include "ecryptfs_format.h"
>
> static const char KEY_TRUSTED_PREFIX[] = "trusted:";
> static const char KEY_USER_PREFIX[] = "user:";
> -static const char hash_alg[] = "sha256";
> -static const char hmac_alg[] = "hmac(sha256)";
> static const char blkcipher_alg[] = "cbc(aes)";
> static const char key_format_default[] = "default";
> static const char key_format_ecryptfs[] = "ecryptfs";
> static const char key_format_enc32[] = "enc32";
> static unsigned int ivsize;
> @@ -52,12 +49,10 @@ static int blksize;
> #define HASH_SIZE SHA256_DIGEST_SIZE
> #define MAX_DATA_SIZE 4096
> #define MIN_DATA_SIZE 20
> #define KEY_ENC32_PAYLOAD_LEN 32
>
> -static struct crypto_shash *hash_tfm;
> -
> enum {
> Opt_new, Opt_load, Opt_update, Opt_err
> };
>
> enum {
> @@ -327,39 +322,18 @@ static struct key *request_user_key(const char *master_desc, const u8 **master_k
> *master_keylen = upayload->datalen;
> error:
> return ukey;
> }
>
> -static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
> - const u8 *buf, unsigned int buflen)
> -{
> - struct crypto_shash *tfm;
> - int err;
> -
> - tfm = crypto_alloc_shash(hmac_alg, 0, 0);
> - if (IS_ERR(tfm)) {
> - pr_err("encrypted_key: can't alloc %s transform: %ld\n",
> - hmac_alg, PTR_ERR(tfm));
> - return PTR_ERR(tfm);
> - }
> -
> - err = crypto_shash_setkey(tfm, key, keylen);
> - if (!err)
> - err = crypto_shash_tfm_digest(tfm, buf, buflen, digest);
> - crypto_free_shash(tfm);
> - return err;
> -}
> -
> enum derived_key_type { ENC_KEY, AUTH_KEY };
>
> /* Derive authentication/encryption key from trusted key */
> static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
> const u8 *master_key, size_t master_keylen)
> {
> u8 *derived_buf;
> unsigned int derived_buf_len;
> - int ret;
>
> derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
> if (derived_buf_len < HASH_SIZE)
> derived_buf_len = HASH_SIZE;
>
> @@ -372,14 +346,13 @@ static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
> else
> strcpy(derived_buf, "ENC_KEY");
>
> memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
> master_keylen);
> - ret = crypto_shash_tfm_digest(hash_tfm, derived_buf, derived_buf_len,
> - derived_key);
> + sha256(derived_buf, derived_buf_len, derived_key);
> kfree_sensitive(derived_buf);
> - return ret;
> + return 0;
> }
>
> static struct skcipher_request *init_skcipher_req(const u8 *key,
> unsigned int key_len)
> {
> @@ -501,14 +474,14 @@ static int datablob_hmac_append(struct encrypted_key_payload *epayload,
> ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
> if (ret < 0)
> goto out;
>
> digest = epayload->format + epayload->datablob_len;
> - ret = calc_hmac(digest, derived_key, sizeof derived_key,
> - epayload->format, epayload->datablob_len);
> - if (!ret)
> - dump_hmac(NULL, digest, HASH_SIZE);
> + hmac_sha256_usingrawkey(derived_key, sizeof(derived_key),
> + epayload->format, epayload->datablob_len,
> + digest);
> + dump_hmac(NULL, digest, HASH_SIZE);
> out:
> memzero_explicit(derived_key, sizeof(derived_key));
> return ret;
> }
>
> @@ -532,13 +505,12 @@ static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
> p = epayload->master_desc;
> len -= strlen(epayload->format) + 1;
> } else
> p = epayload->format;
>
> - ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
> - if (ret < 0)
> - goto out;
> + hmac_sha256_usingrawkey(derived_key, sizeof(derived_key), p, len,
> + digest);
> ret = crypto_memneq(digest, epayload->format + epayload->datablob_len,
> sizeof(digest));
> if (ret) {
> ret = -EINVAL;
> dump_hmac("datablob",
> @@ -1009,33 +981,18 @@ EXPORT_SYMBOL_GPL(key_type_encrypted);
>
> static int __init init_encrypted(void)
> {
> int ret;
>
> - hash_tfm = crypto_alloc_shash(hash_alg, 0, 0);
> - if (IS_ERR(hash_tfm)) {
> - pr_err("encrypted_key: can't allocate %s transform: %ld\n",
> - hash_alg, PTR_ERR(hash_tfm));
> - return PTR_ERR(hash_tfm);
> - }
> -
> ret = aes_get_sizes();
> if (ret < 0)
> - goto out;
> - ret = register_key_type(&key_type_encrypted);
> - if (ret < 0)
> - goto out;
> - return 0;
> -out:
> - crypto_free_shash(hash_tfm);
> - return ret;
> -
> + return ret;
> + return register_key_type(&key_type_encrypted);
> }
>
> static void __exit cleanup_encrypted(void)
> {
> - crypto_free_shash(hash_tfm);
> unregister_key_type(&key_type_encrypted);
> }
>
> late_initcall(init_encrypted);
> module_exit(cleanup_encrypted);
>
> base-commit: d6084bb815c453de27af8071a23163a711586a6c
> --
> 2.50.1
>
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