This patch adds keyinfo.c supporting key management.
- fscrypt_get_encryption_info
- fscrypt_free_encryption_info
Signed-off-by: Michael Halcrow <mhalc...@google.com>
Signed-off-by: Ildar Muslukhov <muslukh...@gmail.com>
Signed-off-by: Theodore Ts'o <ty...@mit.edu>
Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
---
fs/crypto/keyinfo.c | 278 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fscrypto.h | 22 ++++
2 files changed, 300 insertions(+)
create mode 100644 fs/crypto/keyinfo.c
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
new file mode 100644
index 0000000..c662103
--- /dev/null
+++ b/fs/crypto/keyinfo.c
@@ -0,0 +1,278 @@
+/*
+ * key management facility for FS encryption support.
+ *
+ * Copyright (C) 2015, Google, Inc.
+ *
+ * This contains encryption key functions.
+ *
+ * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
+ */
+
+#include <keys/encrypted-type.h>
+#include <keys/user-type.h>
+#include <linux/random.h>
+#include <linux/scatterlist.h>
+#include <uapi/linux/keyctl.h>
+#include <crypto/hash.h>
+#include <linux/fscrypto.h>
+
+static void derive_crypt_complete(struct crypto_async_request *req, int rc)
+{
+ struct fscrypt_completion_result *ecr = req->data;
+
+ if (rc == -EINPROGRESS)
+ return;
+
+ ecr->res = rc;
+ complete(&ecr->completion);
+}
+
+/**
+ * derive_key_aes() - Derive a key using AES-128-ECB
+ * @deriving_key: Encryption key used for derivation.
+ * @source_key: Source key to which to apply derivation.
+ * @derived_key: Derived key.
+ *
+ * Return: Zero on success; non-zero otherwise.
+ */
+static int derive_key_aes(char deriving_key[FS_AES_128_ECB_KEY_SIZE],
+ char source_key[FS_AES_256_XTS_KEY_SIZE],
+ char derived_key[FS_AES_256_XTS_KEY_SIZE])
+{
+ int res = 0;
+ struct ablkcipher_request *req = NULL;
+ DECLARE_FS_COMPLETION_RESULT(ecr);
+ struct scatterlist src_sg, dst_sg;
+ struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0,
+ 0);
+
+ if (IS_ERR(tfm)) {
+ res = PTR_ERR(tfm);
+ tfm = NULL;
+ goto out;
+ }
+ crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
+ req = ablkcipher_request_alloc(tfm, GFP_NOFS);
+ if (!req) {
+ res = -ENOMEM;
+ goto out;
+ }
+ ablkcipher_request_set_callback(req,
+ CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+ derive_crypt_complete, &ecr);
+ res = crypto_ablkcipher_setkey(tfm, deriving_key,
+ FS_AES_128_ECB_KEY_SIZE);
+ if (res < 0)
+ goto out;
+
+ sg_init_one(&src_sg, source_key, FS_AES_256_XTS_KEY_SIZE);
+ sg_init_one(&dst_sg, derived_key, FS_AES_256_XTS_KEY_SIZE);
+ ablkcipher_request_set_crypt(req, &src_sg, &dst_sg,
+ FS_AES_256_XTS_KEY_SIZE, NULL);
+ res = crypto_ablkcipher_encrypt(req);
+ if (res == -EINPROGRESS || res == -EBUSY) {
+ wait_for_completion(&ecr.completion);
+ res = ecr.res;
+ }
+out:
+ if (req)
+ ablkcipher_request_free(req);
+ if (tfm)
+ crypto_free_ablkcipher(tfm);
+ return res;
+}
+
+static void put_crypt_info(struct fscrypt_info *ci)
+{
+ if (!ci)
+ return;
+
+ if (ci->ci_keyring_key)
+ key_put(ci->ci_keyring_key);
+ crypto_free_ablkcipher(ci->ci_ctfm);
+ kmem_cache_free(fscrypt_info_cachep, ci);
+}
+
+int get_crypt_info(struct inode *inode)
+{
+ struct fscrypt_info *crypt_info;
+ char 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_ablkcipher *ctfm;
+ const char *cipher_str;
+ char raw_key[FS_MAX_KEY_SIZE];
+ char mode;
+ int res;
+
+ res = fscrypt_initialize();
+ if (res)
+ return res;
+
+ if (!inode->i_sb->s_cop->get_context)
+ return -EOPNOTSUPP;
+retry:
+ crypt_info = ACCESS_ONCE(inode->i_crypt_info);
+ if (crypt_info) {
+ if (!crypt_info->ci_keyring_key ||
+ key_validate(crypt_info->ci_keyring_key) == 0)
+ return 0;
+ fscrypt_put_encryption_info(inode, crypt_info);
+ goto retry;
+ }
+
+ res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
+ if (res < 0) {
+ if (!fscrypt_dummy_context_enabled(inode))
+ return res;
+ ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
+ ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
+ ctx.flags = 0;
+ } else if (res != sizeof(ctx)) {
+ return -EINVAL;
+ }
+ res = 0;
+
+ crypt_info = kmem_cache_alloc(fscrypt_info_cachep, GFP_NOFS);
+ if (!crypt_info)
+ return -ENOMEM;
+
+ crypt_info->ci_flags = ctx.flags;
+ crypt_info->ci_data_mode = ctx.contents_encryption_mode;
+ crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
+ crypt_info->ci_ctfm = NULL;
+ crypt_info->ci_keyring_key = NULL;
+ memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
+ sizeof(crypt_info->ci_master_key));
+ if (S_ISREG(inode->i_mode))
+ mode = crypt_info->ci_data_mode;
+ else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
+ mode = crypt_info->ci_filename_mode;
+ else
+ BUG();
+
+ switch (mode) {
+ case FS_ENCRYPTION_MODE_AES_256_XTS:
+ cipher_str = "xts(aes)";
+ break;
+ case FS_ENCRYPTION_MODE_AES_256_CTS:
+ cipher_str = "cts(cbc(aes))";
+ break;
+ default:
+ printk_once(KERN_WARNING
+ "%s: unsupported key mode %d (ino %u)\n",
+ __func__, mode, (unsigned) inode->i_ino);
+ res = -ENOKEY;
+ goto out;
+ }
+ if (fscrypt_dummy_context_enabled(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);
+ 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_ablkcipher(cipher_str, 0, 0);
+ if (!ctfm || IS_ERR(ctfm)) {
+ res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
+ printk(KERN_DEBUG
+ "%s: error %d (inode %u) allocating crypto tfm\n",
+ __func__, res, (unsigned) inode->i_ino);
+ goto out;
+ }
+ crypt_info->ci_ctfm = ctfm;
+ crypto_ablkcipher_clear_flags(ctfm, ~0);
+ crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
+ CRYPTO_TFM_REQ_WEAK_KEY);
+ res = crypto_ablkcipher_setkey(ctfm, raw_key, fscrypt_key_size(mode));
+ if (res)
+ goto out;
+
+ memzero_explicit(raw_key, sizeof(raw_key));
+ if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) != NULL) {
+ put_crypt_info(crypt_info);
+ goto retry;
+ }
+ return 0;
+
+out:
+ if (res == -ENOKEY)
+ res = 0;
+ put_crypt_info(crypt_info);
+ memzero_explicit(raw_key, sizeof(raw_key));
+ return res;
+}
+
+void fscrypt_put_encryption_info(struct inode *inode, struct fscrypt_info *ci)
+{
+ struct fscrypt_info *prev;
+
+ if (ci == NULL)
+ ci = ACCESS_ONCE(inode->i_crypt_info);
+ if (ci == NULL)
+ return;
+
+ prev = cmpxchg(&inode->i_crypt_info, ci, NULL);
+ if (prev != ci)
+ return;
+
+ put_crypt_info(ci);
+}
+EXPORT_SYMBOL(fscrypt_put_encryption_info);
+
+int fscrypt_get_encryption_info(struct inode *inode)
+{
+ struct fscrypt_info *ci = inode->i_crypt_info;
+
+ if (!ci ||
+ (ci->ci_keyring_key &&
+ (ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) |
+ (1 << KEY_FLAG_REVOKED) |
+ (1 << KEY_FLAG_DEAD)))))
+ return get_crypt_info(inode);
+ return 0;
+}
+EXPORT_SYMBOL(fscrypt_get_encryption_info);
diff --git a/include/linux/fscrypto.h b/include/linux/fscrypto.h
index e17c6a4..4d17e10 100644
--- a/include/linux/fscrypto.h
+++ b/include/linux/fscrypto.h
@@ -256,6 +256,11 @@ int fscrypt_process_policy(struct inode *, const struct
fscrypt_policy *);
int fscrypt_get_policy(struct inode *, struct fscrypt_policy *);
int fscrypt_has_permitted_context(struct inode *, struct inode *);
int fscrypt_inherit_context(struct inode *, struct inode *, void *, bool);
+
+/* keyinfo.c */
+int get_crypt_info(struct inode *);
+int fscrypt_get_encryption_info(struct inode *);
+void fscrypt_put_encryption_info(struct inode *, struct fscrypt_info *);
#else
/* crypto.c */
static inline struct fscrypt_ctx *fscrypt_get_ctx(struct inode *i)
@@ -323,5 +328,22 @@ static inline int fscrypt_inherit_context(struct inode *p,
struct inode *i,
{
return -EOPNOTSUPP;
}
+
+/* keyinfo.c */
+static inline int get_crypt_info(struct inode *i)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline int fscrypt_get_encryption_info(struct inode *i)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline void fscrypt_put_encryption_info(struct inode *i,
+ struct fscrypt_info *f)
+{
+ return;
+}
#endif
#endif /* _LINUX_FSCRYPTO_H */
--
2.6.3
