From feed825861919ac3fac4b2ab83673dd5225f7f0d Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sun, 4 Aug 2019 19:35:45 -0700 Subject: fscrypt: rename keyinfo.c to keysetup.c Rename keyinfo.c to keysetup.c since this better describes what the file does (sets up the key), and it matches the new file keysetup_v1.c. Reviewed-by: Theodore Ts'o Signed-off-by: Eric Biggers --- fs/crypto/keysetup.c | 345 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 345 insertions(+) create mode 100644 fs/crypto/keysetup.c (limited to 'fs/crypto/keysetup.c') diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c new file mode 100644 index 000000000000..f4a47448e9ef --- /dev/null +++ b/fs/crypto/keysetup.c @@ -0,0 +1,345 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Key setup facility for FS encryption support. + * + * Copyright (C) 2015, Google, Inc. + * + * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar. + * Heavily modified since then. + */ + +#include +#include +#include +#include + +#include "fscrypt_private.h" + +static struct crypto_shash *essiv_hash_tfm; + +static struct fscrypt_mode available_modes[] = { + [FSCRYPT_MODE_AES_256_XTS] = { + .friendly_name = "AES-256-XTS", + .cipher_str = "xts(aes)", + .keysize = 64, + .ivsize = 16, + }, + [FSCRYPT_MODE_AES_256_CTS] = { + .friendly_name = "AES-256-CTS-CBC", + .cipher_str = "cts(cbc(aes))", + .keysize = 32, + .ivsize = 16, + }, + [FSCRYPT_MODE_AES_128_CBC] = { + .friendly_name = "AES-128-CBC", + .cipher_str = "cbc(aes)", + .keysize = 16, + .ivsize = 16, + .needs_essiv = true, + }, + [FSCRYPT_MODE_AES_128_CTS] = { + .friendly_name = "AES-128-CTS-CBC", + .cipher_str = "cts(cbc(aes))", + .keysize = 16, + .ivsize = 16, + }, + [FSCRYPT_MODE_ADIANTUM] = { + .friendly_name = "Adiantum", + .cipher_str = "adiantum(xchacha12,aes)", + .keysize = 32, + .ivsize = 32, + }, +}; + +static struct fscrypt_mode * +select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode) +{ + if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) { + fscrypt_warn(inode, + "Unsupported encryption modes (contents mode %d, filenames mode %d)", + ci->ci_data_mode, ci->ci_filename_mode); + return ERR_PTR(-EINVAL); + } + + if (S_ISREG(inode->i_mode)) + return &available_modes[ci->ci_data_mode]; + + if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) + return &available_modes[ci->ci_filename_mode]; + + WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", + inode->i_ino, (inode->i_mode & S_IFMT)); + return ERR_PTR(-EINVAL); +} + +/* Create a symmetric cipher object for the given encryption mode and key */ +struct crypto_skcipher *fscrypt_allocate_skcipher(struct fscrypt_mode *mode, + const u8 *raw_key, + const struct inode *inode) +{ + struct crypto_skcipher *tfm; + int err; + + tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0); + if (IS_ERR(tfm)) { + if (PTR_ERR(tfm) == -ENOENT) { + fscrypt_warn(inode, + "Missing crypto API support for %s (API name: \"%s\")", + mode->friendly_name, mode->cipher_str); + return ERR_PTR(-ENOPKG); + } + fscrypt_err(inode, "Error allocating '%s' transform: %ld", + mode->cipher_str, PTR_ERR(tfm)); + return tfm; + } + if (unlikely(!mode->logged_impl_name)) { + /* + * fscrypt performance can vary greatly depending on which + * crypto algorithm implementation is used. Help people debug + * performance problems by logging the ->cra_driver_name the + * first time a mode is used. Note that multiple threads can + * race here, but it doesn't really matter. + */ + mode->logged_impl_name = true; + pr_info("fscrypt: %s using implementation \"%s\"\n", + mode->friendly_name, + crypto_skcipher_alg(tfm)->base.cra_driver_name); + } + crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); + err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize); + if (err) + goto err_free_tfm; + + return tfm; + +err_free_tfm: + crypto_free_skcipher(tfm); + return ERR_PTR(err); +} + +static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt) +{ + struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm); + + /* init hash transform on demand */ + if (unlikely(!tfm)) { + struct crypto_shash *prev_tfm; + + tfm = crypto_alloc_shash("sha256", 0, 0); + if (IS_ERR(tfm)) { + if (PTR_ERR(tfm) == -ENOENT) { + fscrypt_warn(NULL, + "Missing crypto API support for SHA-256"); + return -ENOPKG; + } + fscrypt_err(NULL, + "Error allocating SHA-256 transform: %ld", + PTR_ERR(tfm)); + return PTR_ERR(tfm); + } + prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm); + if (prev_tfm) { + crypto_free_shash(tfm); + tfm = prev_tfm; + } + } + + { + SHASH_DESC_ON_STACK(desc, tfm); + desc->tfm = tfm; + + return crypto_shash_digest(desc, key, keysize, salt); + } +} + +static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key, + int keysize) +{ + int err; + struct crypto_cipher *essiv_tfm; + u8 salt[SHA256_DIGEST_SIZE]; + + if (WARN_ON(ci->ci_mode->ivsize != AES_BLOCK_SIZE)) + return -EINVAL; + + essiv_tfm = crypto_alloc_cipher("aes", 0, 0); + if (IS_ERR(essiv_tfm)) + return PTR_ERR(essiv_tfm); + + ci->ci_essiv_tfm = essiv_tfm; + + err = derive_essiv_salt(raw_key, keysize, salt); + if (err) + goto out; + + /* + * Using SHA256 to derive the salt/key will result in AES-256 being + * used for IV generation. File contents encryption will still use the + * configured keysize (AES-128) nevertheless. + */ + err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt)); + if (err) + goto out; + +out: + memzero_explicit(salt, sizeof(salt)); + return err; +} + +/* Given the per-file key, set up the file's crypto transform object(s) */ +int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key) +{ + struct fscrypt_mode *mode = ci->ci_mode; + struct crypto_skcipher *ctfm; + int err; + + ctfm = fscrypt_allocate_skcipher(mode, derived_key, ci->ci_inode); + if (IS_ERR(ctfm)) + return PTR_ERR(ctfm); + + ci->ci_ctfm = ctfm; + + if (mode->needs_essiv) { + err = init_essiv_generator(ci, derived_key, mode->keysize); + if (err) { + fscrypt_warn(ci->ci_inode, + "Error initializing ESSIV generator: %d", + err); + return err; + } + } + return 0; +} + +/* + * Find the master key, then set up the inode's actual encryption key. + */ +static int setup_file_encryption_key(struct fscrypt_info *ci) +{ + return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); +} + +static void put_crypt_info(struct fscrypt_info *ci) +{ + if (!ci) + return; + + if (ci->ci_direct_key) { + fscrypt_put_direct_key(ci->ci_direct_key); + } else { + crypto_free_skcipher(ci->ci_ctfm); + crypto_free_cipher(ci->ci_essiv_tfm); + } + kmem_cache_free(fscrypt_info_cachep, ci); +} + +int fscrypt_get_encryption_info(struct inode *inode) +{ + struct fscrypt_info *crypt_info; + struct fscrypt_context ctx; + struct fscrypt_mode *mode; + int res; + + if (fscrypt_has_encryption_key(inode)) + return 0; + + res = fscrypt_initialize(inode->i_sb->s_cop->flags); + if (res) + return res; + + res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + if (res < 0) { + if (!fscrypt_dummy_context_enabled(inode) || + IS_ENCRYPTED(inode)) { + fscrypt_warn(inode, + "Error %d getting encryption context", + res); + return res; + } + /* Fake up a context for an unencrypted directory */ + memset(&ctx, 0, sizeof(ctx)); + ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; + ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; + ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; + memset(ctx.master_key_descriptor, 0x42, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + } else if (res != sizeof(ctx)) { + fscrypt_warn(inode, + "Unknown encryption context size (%d bytes)", res); + return -EINVAL; + } + + if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) { + fscrypt_warn(inode, "Unknown encryption context version (%d)", + ctx.format); + return -EINVAL; + } + + if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) { + fscrypt_warn(inode, "Unknown encryption context flags (0x%02x)", + ctx.flags); + return -EINVAL; + } + + crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS); + if (!crypt_info) + return -ENOMEM; + + crypt_info->ci_inode = inode; + + crypt_info->ci_flags = ctx.flags; + crypt_info->ci_data_mode = ctx.contents_encryption_mode; + crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; + memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + + mode = select_encryption_mode(crypt_info, inode); + if (IS_ERR(mode)) { + res = PTR_ERR(mode); + goto out; + } + WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE); + crypt_info->ci_mode = mode; + + res = setup_file_encryption_key(crypt_info); + if (res) + goto out; + + if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) + crypt_info = NULL; +out: + if (res == -ENOKEY) + res = 0; + put_crypt_info(crypt_info); + return res; +} +EXPORT_SYMBOL(fscrypt_get_encryption_info); + +/** + * fscrypt_put_encryption_info - free most of an inode's fscrypt data + * + * Free the inode's fscrypt_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 + * + * 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); -- cgit v1.2.3-58-ga151