From b5a7aef1ef436ec005fef0efe31a676ec5f4ab31 Mon Sep 17 00:00:00 2001 From: Jaegeuk Kim Date: Wed, 4 May 2016 22:05:01 -0700 Subject: [PATCH] fscrypto/f2fs: allow fs-specific key prefix for fs encryption This patch allows fscrypto to handle a second key prefix given by filesystem. The main reason is to provide backward compatibility, since previously f2fs used "f2fs:" as a crypto prefix instead of "fscrypt:". Later, ext4 should also provide key_prefix() to give "ext4:". One concern decribed by Ted would be kinda double check overhead of prefixes. In x86, for example, validate_user_key consumes 8 ms after boot-up, which turns out derive_key_aes() consumed most of the time to load specific crypto module. After such the cold miss, it shows almost zero latencies, which treats as a negligible overhead. Note that request_key() detects wrong prefix in prior to derive_key_aes() even. Cc: Ted Tso Cc: stable@vger.kernel.org # v4.6 Signed-off-by: Jaegeuk Kim --- fs/crypto/keyinfo.c | 120 +++++++++++++++++++++++++-------------- fs/f2fs/f2fs.h | 8 +++ fs/f2fs/super.c | 13 +++++ include/linux/fscrypto.h | 1 + 4 files changed, 98 insertions(+), 44 deletions(-) diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c index 06f5aa478bf2..1ac263eddc4e 100644 --- a/fs/crypto/keyinfo.c +++ b/fs/crypto/keyinfo.c @@ -78,6 +78,67 @@ static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE], return res; } +static int validate_user_key(struct fscrypt_info *crypt_info, + struct fscrypt_context *ctx, u8 *raw_key, + u8 *prefix, int prefix_size) +{ + u8 *full_key_descriptor; + struct key *keyring_key; + struct fscrypt_key *master_key; + const struct user_key_payload *ukp; + int full_key_len = prefix_size + (FS_KEY_DESCRIPTOR_SIZE * 2) + 1; + int res; + + full_key_descriptor = kmalloc(full_key_len, GFP_NOFS); + if (!full_key_descriptor) + return -ENOMEM; + + memcpy(full_key_descriptor, prefix, prefix_size); + sprintf(full_key_descriptor + prefix_size, + "%*phN", FS_KEY_DESCRIPTOR_SIZE, + ctx->master_key_descriptor); + full_key_descriptor[full_key_len - 1] = '\0'; + keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL); + kfree(full_key_descriptor); + if (IS_ERR(keyring_key)) + return PTR_ERR(keyring_key); + + if (keyring_key->type != &key_type_logon) { + printk_once(KERN_WARNING + "%s: key type must be logon\n", __func__); + res = -ENOKEY; + goto out; + } + down_read(&keyring_key->sem); + ukp = user_key_payload(keyring_key); + if (ukp->datalen != sizeof(struct fscrypt_key)) { + res = -EINVAL; + up_read(&keyring_key->sem); + goto out; + } + master_key = (struct fscrypt_key *)ukp->data; + BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE); + + if (master_key->size != FS_AES_256_XTS_KEY_SIZE) { + printk_once(KERN_WARNING + "%s: key size incorrect: %d\n", + __func__, master_key->size); + res = -ENOKEY; + up_read(&keyring_key->sem); + goto out; + } + res = derive_key_aes(ctx->nonce, master_key->raw, raw_key); + up_read(&keyring_key->sem); + if (res) + goto out; + + crypt_info->ci_keyring_key = keyring_key; + return 0; +out: + key_put(keyring_key); + return res; +} + static void put_crypt_info(struct fscrypt_info *ci) { if (!ci) @@ -91,12 +152,7 @@ static void put_crypt_info(struct fscrypt_info *ci) int get_crypt_info(struct inode *inode) { struct fscrypt_info *crypt_info; - u8 full_key_descriptor[FS_KEY_DESC_PREFIX_SIZE + - (FS_KEY_DESCRIPTOR_SIZE * 2) + 1]; - struct key *keyring_key = NULL; - struct fscrypt_key *master_key; struct fscrypt_context ctx; - const struct user_key_payload *ukp; struct crypto_skcipher *ctfm; const char *cipher_str; u8 raw_key[FS_MAX_KEY_SIZE]; @@ -167,48 +223,24 @@ int get_crypt_info(struct inode *inode) memset(raw_key, 0x42, FS_AES_256_XTS_KEY_SIZE); goto got_key; } - memcpy(full_key_descriptor, FS_KEY_DESC_PREFIX, - FS_KEY_DESC_PREFIX_SIZE); - sprintf(full_key_descriptor + FS_KEY_DESC_PREFIX_SIZE, - "%*phN", FS_KEY_DESCRIPTOR_SIZE, - ctx.master_key_descriptor); - full_key_descriptor[FS_KEY_DESC_PREFIX_SIZE + - (2 * FS_KEY_DESCRIPTOR_SIZE)] = '\0'; - keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL); - if (IS_ERR(keyring_key)) { - res = PTR_ERR(keyring_key); - keyring_key = NULL; - goto out; - } - crypt_info->ci_keyring_key = keyring_key; - if (keyring_key->type != &key_type_logon) { - printk_once(KERN_WARNING - "%s: key type must be logon\n", __func__); - res = -ENOKEY; - goto out; - } - down_read(&keyring_key->sem); - ukp = user_key_payload(keyring_key); - if (ukp->datalen != sizeof(struct fscrypt_key)) { - res = -EINVAL; - up_read(&keyring_key->sem); - goto out; - } - master_key = (struct fscrypt_key *)ukp->data; - BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE); - if (master_key->size != FS_AES_256_XTS_KEY_SIZE) { - printk_once(KERN_WARNING - "%s: key size incorrect: %d\n", - __func__, master_key->size); - res = -ENOKEY; - up_read(&keyring_key->sem); + res = validate_user_key(crypt_info, &ctx, raw_key, + FS_KEY_DESC_PREFIX, FS_KEY_DESC_PREFIX_SIZE); + if (res && inode->i_sb->s_cop->key_prefix) { + u8 *prefix = NULL; + int prefix_size, res2; + + prefix_size = inode->i_sb->s_cop->key_prefix(inode, &prefix); + res2 = validate_user_key(crypt_info, &ctx, raw_key, + prefix, prefix_size); + if (res2) { + if (res2 == -ENOKEY) + res = -ENOKEY; + goto out; + } + } else if (res) { goto out; } - res = derive_key_aes(ctx.nonce, master_key->raw, raw_key); - up_read(&keyring_key->sem); - if (res) - goto out; got_key: ctfm = crypto_alloc_skcipher(cipher_str, 0, 0); if (!ctfm || IS_ERR(ctfm)) { diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index ccf8bf4debfc..dbd277eb9da7 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -711,6 +711,10 @@ enum { MAX_TIME, }; +#ifdef CONFIG_F2FS_FS_ENCRYPTION +#define F2FS_KEY_DESC_PREFIX "f2fs:" +#define F2FS_KEY_DESC_PREFIX_SIZE 5 +#endif struct f2fs_sb_info { struct super_block *sb; /* pointer to VFS super block */ struct proc_dir_entry *s_proc; /* proc entry */ @@ -718,6 +722,10 @@ struct f2fs_sb_info { int valid_super_block; /* valid super block no */ int s_flag; /* flags for sbi */ +#ifdef CONFIG_F2FS_FS_ENCRYPTION + u8 key_prefix[F2FS_KEY_DESC_PREFIX_SIZE]; + u8 key_prefix_size; +#endif /* for node-related operations */ struct f2fs_nm_info *nm_info; /* node manager */ struct inode *node_inode; /* cache node blocks */ diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index 8a28f799a24f..28c8992da6f6 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -964,6 +964,12 @@ static int f2fs_get_context(struct inode *inode, void *ctx, size_t len) ctx, len, NULL); } +static int f2fs_key_prefix(struct inode *inode, u8 **key) +{ + *key = F2FS_I_SB(inode)->key_prefix; + return F2FS_I_SB(inode)->key_prefix_size; +} + static int f2fs_set_context(struct inode *inode, const void *ctx, size_t len, void *fs_data) { @@ -980,6 +986,7 @@ static unsigned f2fs_max_namelen(struct inode *inode) static struct fscrypt_operations f2fs_cryptops = { .get_context = f2fs_get_context, + .key_prefix = f2fs_key_prefix, .set_context = f2fs_set_context, .is_encrypted = f2fs_encrypted_inode, .empty_dir = f2fs_empty_dir, @@ -1305,6 +1312,12 @@ static void init_sb_info(struct f2fs_sb_info *sbi) INIT_LIST_HEAD(&sbi->s_list); mutex_init(&sbi->umount_mutex); + +#ifdef CONFIG_F2FS_FS_ENCRYPTION + memcpy(sbi->key_prefix, F2FS_KEY_DESC_PREFIX, + F2FS_KEY_DESC_PREFIX_SIZE); + sbi->key_prefix_size = F2FS_KEY_DESC_PREFIX_SIZE; +#endif } /* diff --git a/include/linux/fscrypto.h b/include/linux/fscrypto.h index 6027f6bbb061..cfa6cde25f8e 100644 --- a/include/linux/fscrypto.h +++ b/include/linux/fscrypto.h @@ -175,6 +175,7 @@ struct fscrypt_name { */ struct fscrypt_operations { int (*get_context)(struct inode *, void *, size_t); + int (*key_prefix)(struct inode *, u8 **); int (*prepare_context)(struct inode *); int (*set_context)(struct inode *, const void *, size_t, void *); int (*dummy_context)(struct inode *);