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2f944c66ae
Calling CBC with ciphertext stealing "CBC-CTS" seems to be more common than calling it "CTS-CBC". E.g., CBC-CTS is used by OpenSSL, Crypto++, RFC3962, and RFC6803. The NIST SP800-38A addendum uses CBC-CS1, CBC-CS2, and CBC-CS3, distinguishing between different CTS conventions but similarly putting the CBC part first. In the interest of avoiding any idiosyncratic terminology, update the fscrypt documentation and the fscrypt_mode "friendly names" to align with the more common convention. Changing the "friendly names" only affects some log messages. The actual mode constants in the API are unchanged; those call it simply "CTS". Add a note to the documentation that clarifies that "CBC" and "CTS" in the API really mean CBC-ESSIV and CBC-CTS, respectively. Link: https://lore.kernel.org/r/20240224053550.44659-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
818 lines
24 KiB
C
818 lines
24 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Key setup facility for FS encryption support.
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*
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* Copyright (C) 2015, Google, Inc.
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*
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* Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
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* Heavily modified since then.
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*/
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#include <crypto/skcipher.h>
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#include <linux/random.h>
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#include "fscrypt_private.h"
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struct fscrypt_mode fscrypt_modes[] = {
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[FSCRYPT_MODE_AES_256_XTS] = {
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.friendly_name = "AES-256-XTS",
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.cipher_str = "xts(aes)",
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.keysize = 64,
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.security_strength = 32,
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.ivsize = 16,
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.blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_256_XTS,
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},
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[FSCRYPT_MODE_AES_256_CTS] = {
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.friendly_name = "AES-256-CBC-CTS",
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.cipher_str = "cts(cbc(aes))",
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.keysize = 32,
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.security_strength = 32,
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.ivsize = 16,
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},
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[FSCRYPT_MODE_AES_128_CBC] = {
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.friendly_name = "AES-128-CBC-ESSIV",
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.cipher_str = "essiv(cbc(aes),sha256)",
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.keysize = 16,
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.security_strength = 16,
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.ivsize = 16,
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.blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV,
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},
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[FSCRYPT_MODE_AES_128_CTS] = {
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.friendly_name = "AES-128-CBC-CTS",
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.cipher_str = "cts(cbc(aes))",
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.keysize = 16,
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.security_strength = 16,
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.ivsize = 16,
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},
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[FSCRYPT_MODE_SM4_XTS] = {
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.friendly_name = "SM4-XTS",
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.cipher_str = "xts(sm4)",
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.keysize = 32,
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.security_strength = 16,
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.ivsize = 16,
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.blk_crypto_mode = BLK_ENCRYPTION_MODE_SM4_XTS,
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},
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[FSCRYPT_MODE_SM4_CTS] = {
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.friendly_name = "SM4-CBC-CTS",
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.cipher_str = "cts(cbc(sm4))",
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.keysize = 16,
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.security_strength = 16,
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.ivsize = 16,
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},
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[FSCRYPT_MODE_ADIANTUM] = {
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.friendly_name = "Adiantum",
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.cipher_str = "adiantum(xchacha12,aes)",
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.keysize = 32,
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.security_strength = 32,
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.ivsize = 32,
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.blk_crypto_mode = BLK_ENCRYPTION_MODE_ADIANTUM,
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},
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[FSCRYPT_MODE_AES_256_HCTR2] = {
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.friendly_name = "AES-256-HCTR2",
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.cipher_str = "hctr2(aes)",
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.keysize = 32,
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.security_strength = 32,
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.ivsize = 32,
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},
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};
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static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex);
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static struct fscrypt_mode *
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select_encryption_mode(const union fscrypt_policy *policy,
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const struct inode *inode)
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{
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BUILD_BUG_ON(ARRAY_SIZE(fscrypt_modes) != FSCRYPT_MODE_MAX + 1);
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if (S_ISREG(inode->i_mode))
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return &fscrypt_modes[fscrypt_policy_contents_mode(policy)];
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if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
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return &fscrypt_modes[fscrypt_policy_fnames_mode(policy)];
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WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
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inode->i_ino, (inode->i_mode & S_IFMT));
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return ERR_PTR(-EINVAL);
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}
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/* Create a symmetric cipher object for the given encryption mode and key */
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static struct crypto_skcipher *
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fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key,
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const struct inode *inode)
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{
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struct crypto_skcipher *tfm;
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int err;
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tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
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if (IS_ERR(tfm)) {
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if (PTR_ERR(tfm) == -ENOENT) {
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fscrypt_warn(inode,
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"Missing crypto API support for %s (API name: \"%s\")",
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mode->friendly_name, mode->cipher_str);
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return ERR_PTR(-ENOPKG);
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}
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fscrypt_err(inode, "Error allocating '%s' transform: %ld",
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mode->cipher_str, PTR_ERR(tfm));
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return tfm;
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}
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if (!xchg(&mode->logged_cryptoapi_impl, 1)) {
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/*
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* fscrypt performance can vary greatly depending on which
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* crypto algorithm implementation is used. Help people debug
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* performance problems by logging the ->cra_driver_name the
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* first time a mode is used.
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*/
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pr_info("fscrypt: %s using implementation \"%s\"\n",
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mode->friendly_name, crypto_skcipher_driver_name(tfm));
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}
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if (WARN_ON_ONCE(crypto_skcipher_ivsize(tfm) != mode->ivsize)) {
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err = -EINVAL;
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goto err_free_tfm;
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}
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crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
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err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize);
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if (err)
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goto err_free_tfm;
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return tfm;
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err_free_tfm:
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crypto_free_skcipher(tfm);
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return ERR_PTR(err);
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}
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/*
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* Prepare the crypto transform object or blk-crypto key in @prep_key, given the
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* raw key, encryption mode (@ci->ci_mode), flag indicating which encryption
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* implementation (fs-layer or blk-crypto) will be used (@ci->ci_inlinecrypt),
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* and IV generation method (@ci->ci_policy.flags).
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*/
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int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
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const u8 *raw_key, const struct fscrypt_inode_info *ci)
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{
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struct crypto_skcipher *tfm;
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if (fscrypt_using_inline_encryption(ci))
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return fscrypt_prepare_inline_crypt_key(prep_key, raw_key, ci);
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tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode);
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if (IS_ERR(tfm))
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return PTR_ERR(tfm);
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/*
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* Pairs with the smp_load_acquire() in fscrypt_is_key_prepared().
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* I.e., here we publish ->tfm with a RELEASE barrier so that
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* concurrent tasks can ACQUIRE it. Note that this concurrency is only
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* possible for per-mode keys, not for per-file keys.
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*/
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smp_store_release(&prep_key->tfm, tfm);
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return 0;
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}
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/* Destroy a crypto transform object and/or blk-crypto key. */
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void fscrypt_destroy_prepared_key(struct super_block *sb,
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struct fscrypt_prepared_key *prep_key)
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{
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crypto_free_skcipher(prep_key->tfm);
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fscrypt_destroy_inline_crypt_key(sb, prep_key);
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memzero_explicit(prep_key, sizeof(*prep_key));
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}
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/* Given a per-file encryption key, set up the file's crypto transform object */
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int fscrypt_set_per_file_enc_key(struct fscrypt_inode_info *ci,
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const u8 *raw_key)
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{
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ci->ci_owns_key = true;
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return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci);
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}
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static int setup_per_mode_enc_key(struct fscrypt_inode_info *ci,
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struct fscrypt_master_key *mk,
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struct fscrypt_prepared_key *keys,
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u8 hkdf_context, bool include_fs_uuid)
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{
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const struct inode *inode = ci->ci_inode;
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const struct super_block *sb = inode->i_sb;
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struct fscrypt_mode *mode = ci->ci_mode;
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const u8 mode_num = mode - fscrypt_modes;
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struct fscrypt_prepared_key *prep_key;
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u8 mode_key[FSCRYPT_MAX_KEY_SIZE];
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u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)];
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unsigned int hkdf_infolen = 0;
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int err;
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if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX))
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return -EINVAL;
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prep_key = &keys[mode_num];
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if (fscrypt_is_key_prepared(prep_key, ci)) {
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ci->ci_enc_key = *prep_key;
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return 0;
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}
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mutex_lock(&fscrypt_mode_key_setup_mutex);
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if (fscrypt_is_key_prepared(prep_key, ci))
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goto done_unlock;
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BUILD_BUG_ON(sizeof(mode_num) != 1);
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BUILD_BUG_ON(sizeof(sb->s_uuid) != 16);
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BUILD_BUG_ON(sizeof(hkdf_info) != 17);
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hkdf_info[hkdf_infolen++] = mode_num;
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if (include_fs_uuid) {
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memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid,
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sizeof(sb->s_uuid));
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hkdf_infolen += sizeof(sb->s_uuid);
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}
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err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
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hkdf_context, hkdf_info, hkdf_infolen,
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mode_key, mode->keysize);
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if (err)
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goto out_unlock;
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err = fscrypt_prepare_key(prep_key, mode_key, ci);
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memzero_explicit(mode_key, mode->keysize);
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if (err)
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goto out_unlock;
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done_unlock:
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ci->ci_enc_key = *prep_key;
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err = 0;
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out_unlock:
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mutex_unlock(&fscrypt_mode_key_setup_mutex);
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return err;
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}
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/*
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* Derive a SipHash key from the given fscrypt master key and the given
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* application-specific information string.
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*
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* Note that the KDF produces a byte array, but the SipHash APIs expect the key
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* as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an
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* endianness swap in order to get the same results as on little endian CPUs.
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*/
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static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk,
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u8 context, const u8 *info,
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unsigned int infolen, siphash_key_t *key)
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{
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int err;
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err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen,
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(u8 *)key, sizeof(*key));
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if (err)
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return err;
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BUILD_BUG_ON(sizeof(*key) != 16);
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BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2);
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le64_to_cpus(&key->key[0]);
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le64_to_cpus(&key->key[1]);
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return 0;
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}
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int fscrypt_derive_dirhash_key(struct fscrypt_inode_info *ci,
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const struct fscrypt_master_key *mk)
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{
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int err;
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err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY,
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ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,
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&ci->ci_dirhash_key);
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if (err)
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return err;
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ci->ci_dirhash_key_initialized = true;
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return 0;
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}
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void fscrypt_hash_inode_number(struct fscrypt_inode_info *ci,
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const struct fscrypt_master_key *mk)
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{
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WARN_ON_ONCE(ci->ci_inode->i_ino == 0);
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WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized);
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ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino,
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&mk->mk_ino_hash_key);
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}
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static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_inode_info *ci,
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struct fscrypt_master_key *mk)
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{
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int err;
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err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys,
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HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true);
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if (err)
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return err;
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/* pairs with smp_store_release() below */
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if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) {
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mutex_lock(&fscrypt_mode_key_setup_mutex);
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if (mk->mk_ino_hash_key_initialized)
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goto unlock;
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err = fscrypt_derive_siphash_key(mk,
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HKDF_CONTEXT_INODE_HASH_KEY,
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NULL, 0, &mk->mk_ino_hash_key);
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if (err)
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goto unlock;
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/* pairs with smp_load_acquire() above */
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smp_store_release(&mk->mk_ino_hash_key_initialized, true);
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unlock:
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mutex_unlock(&fscrypt_mode_key_setup_mutex);
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if (err)
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return err;
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}
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/*
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* New inodes may not have an inode number assigned yet.
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* Hashing their inode number is delayed until later.
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*/
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if (ci->ci_inode->i_ino)
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fscrypt_hash_inode_number(ci, mk);
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return 0;
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}
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static int fscrypt_setup_v2_file_key(struct fscrypt_inode_info *ci,
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struct fscrypt_master_key *mk,
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bool need_dirhash_key)
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{
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int err;
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if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
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/*
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* DIRECT_KEY: instead of deriving per-file encryption keys, the
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* per-file nonce will be included in all the IVs. But unlike
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* v1 policies, for v2 policies in this case we don't encrypt
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* with the master key directly but rather derive a per-mode
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* encryption key. This ensures that the master key is
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* consistently used only for HKDF, avoiding key reuse issues.
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*/
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err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys,
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HKDF_CONTEXT_DIRECT_KEY, false);
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} else if (ci->ci_policy.v2.flags &
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FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
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/*
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* IV_INO_LBLK_64: encryption keys are derived from (master_key,
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* mode_num, filesystem_uuid), and inode number is included in
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* the IVs. This format is optimized for use with inline
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* encryption hardware compliant with the UFS standard.
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*/
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err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys,
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HKDF_CONTEXT_IV_INO_LBLK_64_KEY,
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true);
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} else if (ci->ci_policy.v2.flags &
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FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) {
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err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk);
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} else {
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u8 derived_key[FSCRYPT_MAX_KEY_SIZE];
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err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
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HKDF_CONTEXT_PER_FILE_ENC_KEY,
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ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,
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derived_key, ci->ci_mode->keysize);
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if (err)
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return err;
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err = fscrypt_set_per_file_enc_key(ci, derived_key);
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memzero_explicit(derived_key, ci->ci_mode->keysize);
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}
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if (err)
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return err;
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/* Derive a secret dirhash key for directories that need it. */
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if (need_dirhash_key) {
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err = fscrypt_derive_dirhash_key(ci, mk);
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if (err)
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return err;
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}
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return 0;
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}
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/*
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* Check whether the size of the given master key (@mk) is appropriate for the
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* encryption settings which a particular file will use (@ci).
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*
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* If the file uses a v1 encryption policy, then the master key must be at least
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* as long as the derived key, as this is a requirement of the v1 KDF.
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*
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* Otherwise, the KDF can accept any size key, so we enforce a slightly looser
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* requirement: we require that the size of the master key be at least the
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* maximum security strength of any algorithm whose key will be derived from it
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* (but in practice we only need to consider @ci->ci_mode, since any other
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* possible subkeys such as DIRHASH and INODE_HASH will never increase the
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* required key size over @ci->ci_mode). This allows AES-256-XTS keys to be
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* derived from a 256-bit master key, which is cryptographically sufficient,
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* rather than requiring a 512-bit master key which is unnecessarily long. (We
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* still allow 512-bit master keys if the user chooses to use them, though.)
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*/
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static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk,
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const struct fscrypt_inode_info *ci)
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{
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unsigned int min_keysize;
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if (ci->ci_policy.version == FSCRYPT_POLICY_V1)
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min_keysize = ci->ci_mode->keysize;
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else
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min_keysize = ci->ci_mode->security_strength;
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if (mk->mk_secret.size < min_keysize) {
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fscrypt_warn(NULL,
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"key with %s %*phN is too short (got %u bytes, need %u+ bytes)",
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master_key_spec_type(&mk->mk_spec),
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master_key_spec_len(&mk->mk_spec),
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(u8 *)&mk->mk_spec.u,
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mk->mk_secret.size, min_keysize);
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return false;
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}
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return true;
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}
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/*
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* Find the master key, then set up the inode's actual encryption key.
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*
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* If the master key is found in the filesystem-level keyring, then it is
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* returned in *mk_ret with its semaphore read-locked. This is needed to ensure
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* that only one task links the fscrypt_inode_info into ->mk_decrypted_inodes
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* (as multiple tasks may race to create an fscrypt_inode_info for the same
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* inode), and to synchronize the master key being removed with a new inode
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* starting to use it.
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*/
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static int setup_file_encryption_key(struct fscrypt_inode_info *ci,
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bool need_dirhash_key,
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|
struct fscrypt_master_key **mk_ret)
|
|
{
|
|
struct super_block *sb = ci->ci_inode->i_sb;
|
|
struct fscrypt_key_specifier mk_spec;
|
|
struct fscrypt_master_key *mk;
|
|
int err;
|
|
|
|
err = fscrypt_select_encryption_impl(ci);
|
|
if (err)
|
|
return err;
|
|
|
|
err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec);
|
|
if (err)
|
|
return err;
|
|
|
|
mk = fscrypt_find_master_key(sb, &mk_spec);
|
|
if (unlikely(!mk)) {
|
|
const union fscrypt_policy *dummy_policy =
|
|
fscrypt_get_dummy_policy(sb);
|
|
|
|
/*
|
|
* Add the test_dummy_encryption key on-demand. In principle,
|
|
* it should be added at mount time. Do it here instead so that
|
|
* the individual filesystems don't need to worry about adding
|
|
* this key at mount time and cleaning up on mount failure.
|
|
*/
|
|
if (dummy_policy &&
|
|
fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) {
|
|
err = fscrypt_add_test_dummy_key(sb, &mk_spec);
|
|
if (err)
|
|
return err;
|
|
mk = fscrypt_find_master_key(sb, &mk_spec);
|
|
}
|
|
}
|
|
if (unlikely(!mk)) {
|
|
if (ci->ci_policy.version != FSCRYPT_POLICY_V1)
|
|
return -ENOKEY;
|
|
|
|
/*
|
|
* As a legacy fallback for v1 policies, search for the key in
|
|
* the current task's subscribed keyrings too. Don't move this
|
|
* to before the search of ->s_master_keys, since users
|
|
* shouldn't be able to override filesystem-level keys.
|
|
*/
|
|
return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
|
|
}
|
|
down_read(&mk->mk_sem);
|
|
|
|
if (!mk->mk_present) {
|
|
/* FS_IOC_REMOVE_ENCRYPTION_KEY has been executed on this key */
|
|
err = -ENOKEY;
|
|
goto out_release_key;
|
|
}
|
|
|
|
if (!fscrypt_valid_master_key_size(mk, ci)) {
|
|
err = -ENOKEY;
|
|
goto out_release_key;
|
|
}
|
|
|
|
switch (ci->ci_policy.version) {
|
|
case FSCRYPT_POLICY_V1:
|
|
err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
|
|
break;
|
|
case FSCRYPT_POLICY_V2:
|
|
err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key);
|
|
break;
|
|
default:
|
|
WARN_ON_ONCE(1);
|
|
err = -EINVAL;
|
|
break;
|
|
}
|
|
if (err)
|
|
goto out_release_key;
|
|
|
|
*mk_ret = mk;
|
|
return 0;
|
|
|
|
out_release_key:
|
|
up_read(&mk->mk_sem);
|
|
fscrypt_put_master_key(mk);
|
|
return err;
|
|
}
|
|
|
|
static void put_crypt_info(struct fscrypt_inode_info *ci)
|
|
{
|
|
struct fscrypt_master_key *mk;
|
|
|
|
if (!ci)
|
|
return;
|
|
|
|
if (ci->ci_direct_key)
|
|
fscrypt_put_direct_key(ci->ci_direct_key);
|
|
else if (ci->ci_owns_key)
|
|
fscrypt_destroy_prepared_key(ci->ci_inode->i_sb,
|
|
&ci->ci_enc_key);
|
|
|
|
mk = ci->ci_master_key;
|
|
if (mk) {
|
|
/*
|
|
* Remove this inode from the list of inodes that were unlocked
|
|
* with the master key. In addition, if we're removing the last
|
|
* inode from an incompletely removed key, then complete the
|
|
* full removal of the key.
|
|
*/
|
|
spin_lock(&mk->mk_decrypted_inodes_lock);
|
|
list_del(&ci->ci_master_key_link);
|
|
spin_unlock(&mk->mk_decrypted_inodes_lock);
|
|
fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk);
|
|
}
|
|
memzero_explicit(ci, sizeof(*ci));
|
|
kmem_cache_free(fscrypt_inode_info_cachep, ci);
|
|
}
|
|
|
|
static int
|
|
fscrypt_setup_encryption_info(struct inode *inode,
|
|
const union fscrypt_policy *policy,
|
|
const u8 nonce[FSCRYPT_FILE_NONCE_SIZE],
|
|
bool need_dirhash_key)
|
|
{
|
|
struct fscrypt_inode_info *crypt_info;
|
|
struct fscrypt_mode *mode;
|
|
struct fscrypt_master_key *mk = NULL;
|
|
int res;
|
|
|
|
res = fscrypt_initialize(inode->i_sb);
|
|
if (res)
|
|
return res;
|
|
|
|
crypt_info = kmem_cache_zalloc(fscrypt_inode_info_cachep, GFP_KERNEL);
|
|
if (!crypt_info)
|
|
return -ENOMEM;
|
|
|
|
crypt_info->ci_inode = inode;
|
|
crypt_info->ci_policy = *policy;
|
|
memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE);
|
|
|
|
mode = select_encryption_mode(&crypt_info->ci_policy, inode);
|
|
if (IS_ERR(mode)) {
|
|
res = PTR_ERR(mode);
|
|
goto out;
|
|
}
|
|
WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
|
|
crypt_info->ci_mode = mode;
|
|
|
|
crypt_info->ci_data_unit_bits =
|
|
fscrypt_policy_du_bits(&crypt_info->ci_policy, inode);
|
|
crypt_info->ci_data_units_per_block_bits =
|
|
inode->i_blkbits - crypt_info->ci_data_unit_bits;
|
|
|
|
res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk);
|
|
if (res)
|
|
goto out;
|
|
|
|
/*
|
|
* For existing inodes, multiple tasks may race to set ->i_crypt_info.
|
|
* So use cmpxchg_release(). This pairs with the smp_load_acquire() in
|
|
* fscrypt_get_inode_info(). I.e., here we publish ->i_crypt_info with
|
|
* a RELEASE barrier so that other tasks can ACQUIRE it.
|
|
*/
|
|
if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) {
|
|
/*
|
|
* We won the race and set ->i_crypt_info to our crypt_info.
|
|
* Now link it into the master key's inode list.
|
|
*/
|
|
if (mk) {
|
|
crypt_info->ci_master_key = mk;
|
|
refcount_inc(&mk->mk_active_refs);
|
|
spin_lock(&mk->mk_decrypted_inodes_lock);
|
|
list_add(&crypt_info->ci_master_key_link,
|
|
&mk->mk_decrypted_inodes);
|
|
spin_unlock(&mk->mk_decrypted_inodes_lock);
|
|
}
|
|
crypt_info = NULL;
|
|
}
|
|
res = 0;
|
|
out:
|
|
if (mk) {
|
|
up_read(&mk->mk_sem);
|
|
fscrypt_put_master_key(mk);
|
|
}
|
|
put_crypt_info(crypt_info);
|
|
return res;
|
|
}
|
|
|
|
/**
|
|
* fscrypt_get_encryption_info() - set up an inode's encryption key
|
|
* @inode: the inode to set up the key for. Must be encrypted.
|
|
* @allow_unsupported: if %true, treat an unsupported encryption policy (or
|
|
* unrecognized encryption context) the same way as the key
|
|
* being unavailable, instead of returning an error. Use
|
|
* %false unless the operation being performed is needed in
|
|
* order for files (or directories) to be deleted.
|
|
*
|
|
* Set up ->i_crypt_info, if it hasn't already been done.
|
|
*
|
|
* Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So
|
|
* generally this shouldn't be called from within a filesystem transaction.
|
|
*
|
|
* Return: 0 if ->i_crypt_info was set or was already set, *or* if the
|
|
* encryption key is unavailable. (Use fscrypt_has_encryption_key() to
|
|
* distinguish these cases.) Also can return another -errno code.
|
|
*/
|
|
int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported)
|
|
{
|
|
int res;
|
|
union fscrypt_context ctx;
|
|
union fscrypt_policy policy;
|
|
|
|
if (fscrypt_has_encryption_key(inode))
|
|
return 0;
|
|
|
|
res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
|
|
if (res < 0) {
|
|
if (res == -ERANGE && allow_unsupported)
|
|
return 0;
|
|
fscrypt_warn(inode, "Error %d getting encryption context", res);
|
|
return res;
|
|
}
|
|
|
|
res = fscrypt_policy_from_context(&policy, &ctx, res);
|
|
if (res) {
|
|
if (allow_unsupported)
|
|
return 0;
|
|
fscrypt_warn(inode,
|
|
"Unrecognized or corrupt encryption context");
|
|
return res;
|
|
}
|
|
|
|
if (!fscrypt_supported_policy(&policy, inode)) {
|
|
if (allow_unsupported)
|
|
return 0;
|
|
return -EINVAL;
|
|
}
|
|
|
|
res = fscrypt_setup_encryption_info(inode, &policy,
|
|
fscrypt_context_nonce(&ctx),
|
|
IS_CASEFOLDED(inode) &&
|
|
S_ISDIR(inode->i_mode));
|
|
|
|
if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */
|
|
res = 0;
|
|
if (res == -ENOKEY)
|
|
res = 0;
|
|
return res;
|
|
}
|
|
|
|
/**
|
|
* fscrypt_prepare_new_inode() - prepare to create a new inode in a directory
|
|
* @dir: a possibly-encrypted directory
|
|
* @inode: the new inode. ->i_mode and ->i_blkbits must be set already.
|
|
* ->i_ino doesn't need to be set yet.
|
|
* @encrypt_ret: (output) set to %true if the new inode will be encrypted
|
|
*
|
|
* If the directory is encrypted, set up its ->i_crypt_info in preparation for
|
|
* encrypting the name of the new file. Also, if the new inode will be
|
|
* encrypted, set up its ->i_crypt_info and set *encrypt_ret=true.
|
|
*
|
|
* This isn't %GFP_NOFS-safe, and therefore it should be called before starting
|
|
* any filesystem transaction to create the inode. For this reason, ->i_ino
|
|
* isn't required to be set yet, as the filesystem may not have set it yet.
|
|
*
|
|
* This doesn't persist the new inode's encryption context. That still needs to
|
|
* be done later by calling fscrypt_set_context().
|
|
*
|
|
* Return: 0 on success, -ENOKEY if the encryption key is missing, or another
|
|
* -errno code
|
|
*/
|
|
int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode,
|
|
bool *encrypt_ret)
|
|
{
|
|
const union fscrypt_policy *policy;
|
|
u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
|
|
|
|
policy = fscrypt_policy_to_inherit(dir);
|
|
if (policy == NULL)
|
|
return 0;
|
|
if (IS_ERR(policy))
|
|
return PTR_ERR(policy);
|
|
|
|
if (WARN_ON_ONCE(inode->i_blkbits == 0))
|
|
return -EINVAL;
|
|
|
|
if (WARN_ON_ONCE(inode->i_mode == 0))
|
|
return -EINVAL;
|
|
|
|
/*
|
|
* Only regular files, directories, and symlinks are encrypted.
|
|
* Special files like device nodes and named pipes aren't.
|
|
*/
|
|
if (!S_ISREG(inode->i_mode) &&
|
|
!S_ISDIR(inode->i_mode) &&
|
|
!S_ISLNK(inode->i_mode))
|
|
return 0;
|
|
|
|
*encrypt_ret = true;
|
|
|
|
get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE);
|
|
return fscrypt_setup_encryption_info(inode, policy, nonce,
|
|
IS_CASEFOLDED(dir) &&
|
|
S_ISDIR(inode->i_mode));
|
|
}
|
|
EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode);
|
|
|
|
/**
|
|
* fscrypt_put_encryption_info() - free most of an inode's fscrypt data
|
|
* @inode: an inode being evicted
|
|
*
|
|
* Free the inode's fscrypt_inode_info. Filesystems must call this when the
|
|
* inode is being evicted. An RCU grace period need not have elapsed yet.
|
|
*/
|
|
void fscrypt_put_encryption_info(struct inode *inode)
|
|
{
|
|
put_crypt_info(inode->i_crypt_info);
|
|
inode->i_crypt_info = NULL;
|
|
}
|
|
EXPORT_SYMBOL(fscrypt_put_encryption_info);
|
|
|
|
/**
|
|
* fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay
|
|
* @inode: an inode being freed
|
|
*
|
|
* Free the inode's cached decrypted symlink target, if any. Filesystems must
|
|
* call this after an RCU grace period, just before they free the inode.
|
|
*/
|
|
void fscrypt_free_inode(struct inode *inode)
|
|
{
|
|
if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) {
|
|
kfree(inode->i_link);
|
|
inode->i_link = NULL;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(fscrypt_free_inode);
|
|
|
|
/**
|
|
* fscrypt_drop_inode() - check whether the inode's master key has been removed
|
|
* @inode: an inode being considered for eviction
|
|
*
|
|
* Filesystems supporting fscrypt must call this from their ->drop_inode()
|
|
* method so that encrypted inodes are evicted as soon as they're no longer in
|
|
* use and their master key has been removed.
|
|
*
|
|
* Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0
|
|
*/
|
|
int fscrypt_drop_inode(struct inode *inode)
|
|
{
|
|
const struct fscrypt_inode_info *ci = fscrypt_get_inode_info(inode);
|
|
|
|
/*
|
|
* If ci is NULL, then the inode doesn't have an encryption key set up
|
|
* so it's irrelevant. If ci_master_key is NULL, then the master key
|
|
* was provided via the legacy mechanism of the process-subscribed
|
|
* keyrings, so we don't know whether it's been removed or not.
|
|
*/
|
|
if (!ci || !ci->ci_master_key)
|
|
return 0;
|
|
|
|
/*
|
|
* With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes
|
|
* protected by the key were cleaned by sync_filesystem(). But if
|
|
* userspace is still using the files, inodes can be dirtied between
|
|
* then and now. We mustn't lose any writes, so skip dirty inodes here.
|
|
*/
|
|
if (inode->i_state & I_DIRTY_ALL)
|
|
return 0;
|
|
|
|
/*
|
|
* We can't take ->mk_sem here, since this runs in atomic context.
|
|
* Therefore, ->mk_present can change concurrently, and our result may
|
|
* immediately become outdated. But there's no correctness problem with
|
|
* unnecessarily evicting. Nor is there a correctness problem with not
|
|
* evicting while iput() is racing with the key being removed, since
|
|
* then the thread removing the key will either evict the inode itself
|
|
* or will correctly detect that it wasn't evicted due to the race.
|
|
*/
|
|
return !READ_ONCE(ci->ci_master_key->mk_present);
|
|
}
|
|
EXPORT_SYMBOL_GPL(fscrypt_drop_inode);
|