As the kernel crypto API implements HKDF, replace the file-system-specific HKDF implementation with the generic HKDF implementation.
Signed-off-by: Stephan Mueller <smuel...@chronox.de> --- fs/crypto/Kconfig | 2 +- fs/crypto/fscrypt_private.h | 4 +- fs/crypto/hkdf.c | 108 +++++++++--------------------------- 3 files changed, 30 insertions(+), 84 deletions(-) diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig index a5f5c30368a2..9450e958f1d1 100644 --- a/fs/crypto/Kconfig +++ b/fs/crypto/Kconfig @@ -2,7 +2,7 @@ config FS_ENCRYPTION bool "FS Encryption (Per-file encryption)" select CRYPTO - select CRYPTO_HASH + select CRYPTO_HKDF select CRYPTO_SKCIPHER select CRYPTO_LIB_SHA256 select KEYS diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 3fa965eb3336..0d6871838099 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -304,7 +304,7 @@ struct fscrypt_hkdf { struct crypto_shash *hmac_tfm; }; -int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, +int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, u8 *master_key, unsigned int master_key_size); /* @@ -323,7 +323,7 @@ int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, #define HKDF_CONTEXT_INODE_HASH_KEY 7 /* info=<empty> */ int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context, - const u8 *info, unsigned int infolen, + u8 *info, unsigned int infolen, u8 *okm, unsigned int okmlen); void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf); diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c index e0ec21055505..f837cb8ec0a5 100644 --- a/fs/crypto/hkdf.c +++ b/fs/crypto/hkdf.c @@ -9,7 +9,7 @@ * Copyright 2019 Google LLC */ -#include <crypto/hash.h> +#include <crypto/hkdf.h> #include <crypto/sha2.h> #include "fscrypt_private.h" @@ -37,34 +37,25 @@ * unnecessarily long master keys. Thus fscrypt still does HKDF-Extract. No * salt is used, since fscrypt master keys should already be pseudorandom and * there's no way to persist a random salt per master key from kernel mode. - */ - -/* HKDF-Extract (RFC 5869 section 2.2), unsalted */ -static int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm, - unsigned int ikmlen, u8 prk[HKDF_HASHLEN]) -{ - static const u8 default_salt[HKDF_HASHLEN]; - int err; - - err = crypto_shash_setkey(hmac_tfm, default_salt, HKDF_HASHLEN); - if (err) - return err; - - return crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk); -} - -/* + * * Compute HKDF-Extract using the given master key as the input keying material, * and prepare an HMAC transform object keyed by the resulting pseudorandom key. * * Afterwards, the keyed HMAC transform object can be used for HKDF-Expand many * times without having to recompute HKDF-Extract each time. */ -int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, +int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, u8 *master_key, unsigned int master_key_size) { + /* HKDF-Extract (RFC 5869 section 2.2), unsalted */ + const struct kvec seed[] = { { + .iov_base = NULL, + .iov_len = 0 + }, { + .iov_base = master_key, + .iov_len = master_key_size + } }; struct crypto_shash *hmac_tfm; - u8 prk[HKDF_HASHLEN]; int err; hmac_tfm = crypto_alloc_shash(HKDF_HMAC_ALG, 0, 0); @@ -74,16 +65,12 @@ int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, return PTR_ERR(hmac_tfm); } - if (WARN_ON(crypto_shash_digestsize(hmac_tfm) != sizeof(prk))) { + if (WARN_ON(crypto_shash_digestsize(hmac_tfm) != HKDF_HASHLEN)) { err = -EINVAL; goto err_free_tfm; } - err = hkdf_extract(hmac_tfm, master_key, master_key_size, prk); - if (err) - goto err_free_tfm; - - err = crypto_shash_setkey(hmac_tfm, prk, sizeof(prk)); + err = crypto_hkdf_setkey(hmac_tfm, seed, ARRAY_SIZE(seed)); if (err) goto err_free_tfm; @@ -93,7 +80,6 @@ int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, err_free_tfm: crypto_free_shash(hmac_tfm); out: - memzero_explicit(prk, sizeof(prk)); return err; } @@ -109,65 +95,25 @@ int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, * accidentally repeat an info string when using HKDF for different purposes.) */ int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context, - const u8 *info, unsigned int infolen, + u8 *info, unsigned int infolen, u8 *okm, unsigned int okmlen) { - SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm); - u8 prefix[9]; - unsigned int i; - int err; - const u8 *prev = NULL; - u8 counter = 1; - u8 tmp[HKDF_HASHLEN]; - - if (WARN_ON(okmlen > 255 * HKDF_HASHLEN)) - return -EINVAL; - - desc->tfm = hkdf->hmac_tfm; - - memcpy(prefix, "fscrypt\0", 8); - prefix[8] = context; - - for (i = 0; i < okmlen; i += HKDF_HASHLEN) { + const struct kvec info_iov[] = { { + .iov_base = "fscrypt\0", + .iov_len = 8, + }, { + .iov_base = &context, + .iov_len = 1, + }, { + .iov_base = info, + .iov_len = infolen, + } }; + int err = crypto_hkdf_generate(hkdf->hmac_tfm, + info_iov, ARRAY_SIZE(info_iov), + okm, okmlen); - err = crypto_shash_init(desc); - if (err) - goto out; - - if (prev) { - err = crypto_shash_update(desc, prev, HKDF_HASHLEN); - if (err) - goto out; - } - - err = crypto_shash_update(desc, prefix, sizeof(prefix)); - if (err) - goto out; - - err = crypto_shash_update(desc, info, infolen); - if (err) - goto out; - - BUILD_BUG_ON(sizeof(counter) != 1); - if (okmlen - i < HKDF_HASHLEN) { - err = crypto_shash_finup(desc, &counter, 1, tmp); - if (err) - goto out; - memcpy(&okm[i], tmp, okmlen - i); - memzero_explicit(tmp, sizeof(tmp)); - } else { - err = crypto_shash_finup(desc, &counter, 1, &okm[i]); - if (err) - goto out; - } - counter++; - prev = &okm[i]; - } - err = 0; -out: if (unlikely(err)) memzero_explicit(okm, okmlen); /* so caller doesn't need to */ - shash_desc_zero(desc); return err; } -- 2.26.2