author: Eric Biggers <ebiggers@google.com> 2021-06-05 00:50:33 -0700
committer: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 2021-07-14 17:07:50 +0200
commit: 5859c67160c32337a43813b5c0b93efa55929fd5
parent: 119782bf159e43fe1ca08a8bbe52d8492b6506c4
Commit Summary:
Diffstat:
1 file changed, 30 insertions, 8 deletions
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 261293fb7097..bca9c6658a7c 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -210,15 +210,40 @@ out_unlock:
return err;
}
+/*
+ * Derive a SipHash key from the given fscrypt master key and the given
+ * application-specific information string.
+ *
+ * Note that the KDF produces a byte array, but the SipHash APIs expect the key
+ * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an
+ * endianness swap in order to get the same results as on little endian CPUs.
+ */
+static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk,
+ u8 context, const u8 *info,
+ unsigned int infolen, siphash_key_t *key)
+{
+ int err;
+
+ err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen,
+ (u8 *)key, sizeof(*key));
+ if (err)
+ return err;
+
+ BUILD_BUG_ON(sizeof(*key) != 16);
+ BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2);
+ le64_to_cpus(&key->key[0]);
+ le64_to_cpus(&key->key[1]);
+ return 0;
+}
+
int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
const struct fscrypt_master_key *mk)
{
int err;
- err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, HKDF_CONTEXT_DIRHASH_KEY,
- ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,
- (u8 *)&ci->ci_dirhash_key,
- sizeof(ci->ci_dirhash_key));
+ err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY,
+ ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,
+ &ci->ci_dirhash_key);
if (err)
return err;
ci->ci_dirhash_key_initialized = true;
@@ -253,10 +278,9 @@ static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info *ci,
if (mk->mk_ino_hash_key_initialized)
goto unlock;
- err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
- HKDF_CONTEXT_INODE_HASH_KEY, NULL, 0,
- (u8 *)&mk->mk_ino_hash_key,
- sizeof(mk->mk_ino_hash_key));
+ err = fscrypt_derive_siphash_key(mk,
+ HKDF_CONTEXT_INODE_HASH_KEY,
+ NULL, 0, &mk->mk_ino_hash_key);
if (err)
goto unlock;
/* pairs with smp_load_acquire() above */