From f592efe735a29c764e0d473307dab0f59665f02b Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Mon, 20 Jan 2020 14:31:58 -0800 Subject: fscrypt: clarify what is meant by a per-file key Now that there's sometimes a second type of per-file key (the dirhash key), clarify some function names, macros, and documentation that specifically deal with per-file *encryption* keys. Link: https://lore.kernel.org/r/20200120223201.241390-4-ebiggers@kernel.org Reviewed-by: Daniel Rosenberg Signed-off-by: Eric Biggers --- fs/crypto/keysetup.c | 39 ++++++++++++++++++++------------------- 1 file changed, 20 insertions(+), 19 deletions(-) (limited to 'fs/crypto/keysetup.c') diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c index 74d61d827d91..65cb09fa6ead 100644 --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -107,12 +107,12 @@ err_free_tfm: return ERR_PTR(err); } -/* Given the per-file key, set up the file's crypto transform object */ -int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key) +/* Given a per-file encryption key, set up the file's crypto transform object */ +int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key) { struct crypto_skcipher *tfm; - tfm = fscrypt_allocate_skcipher(ci->ci_mode, derived_key, ci->ci_inode); + tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode); if (IS_ERR(tfm)) return PTR_ERR(tfm); @@ -121,10 +121,10 @@ int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key) return 0; } -static int setup_per_mode_key(struct fscrypt_info *ci, - struct fscrypt_master_key *mk, - struct crypto_skcipher **tfms, - u8 hkdf_context, bool include_fs_uuid) +static int setup_per_mode_enc_key(struct fscrypt_info *ci, + struct fscrypt_master_key *mk, + struct crypto_skcipher **tfms, + u8 hkdf_context, bool include_fs_uuid) { const struct inode *inode = ci->ci_inode; const struct super_block *sb = inode->i_sb; @@ -196,15 +196,15 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci, if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { /* - * DIRECT_KEY: instead of deriving per-file keys, the per-file - * nonce will be included in all the IVs. But unlike v1 - * policies, for v2 policies in this case we don't encrypt with - * the master key directly but rather derive a per-mode key. - * This ensures that the master key is consistently used only - * for HKDF, avoiding key reuse issues. + * DIRECT_KEY: instead of deriving per-file encryption keys, the + * per-file nonce will be included in all the IVs. But unlike + * v1 policies, for v2 policies in this case we don't encrypt + * with the master key directly but rather derive a per-mode + * encryption key. This ensures that the master key is + * consistently used only for HKDF, avoiding key reuse issues. */ - err = setup_per_mode_key(ci, mk, mk->mk_direct_tfms, - HKDF_CONTEXT_DIRECT_KEY, false); + err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_tfms, + HKDF_CONTEXT_DIRECT_KEY, false); } else if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { /* @@ -213,20 +213,21 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci, * the IVs. This format is optimized for use with inline * encryption hardware compliant with the UFS or eMMC standards. */ - err = setup_per_mode_key(ci, mk, mk->mk_iv_ino_lblk_64_tfms, - HKDF_CONTEXT_IV_INO_LBLK_64_KEY, true); + err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_tfms, + HKDF_CONTEXT_IV_INO_LBLK_64_KEY, + true); } else { u8 derived_key[FSCRYPT_MAX_KEY_SIZE]; err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, - HKDF_CONTEXT_PER_FILE_KEY, + HKDF_CONTEXT_PER_FILE_ENC_KEY, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE, derived_key, ci->ci_mode->keysize); if (err) return err; - err = fscrypt_set_derived_key(ci, derived_key); + err = fscrypt_set_per_file_enc_key(ci, derived_key); memzero_explicit(derived_key, ci->ci_mode->keysize); } if (err) -- cgit