This patch adds policy.c supporting context management.
1. For ioctls:
- fscrypt_process_policy
- fscrypt_get_policy
2. For context permission
- fscrypt_has_permitted_context
- fscrypt_inherit_context
Signed-off-by: Michael Halcrow <mhalc...@google.com>
Signed-off-by: Theodore Ts'o <ty...@mit.edu>
Signed-off-by: Ildar Muslukhov <muslukh...@gmail.com>
Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
---
fs/crypto/policy.c | 229 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fscrypto.h | 30 +++++++
2 files changed, 259 insertions(+)
create mode 100644 fs/crypto/policy.c
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
new file mode 100644
index 0000000..0f9961e
--- /dev/null
+++ b/fs/crypto/policy.c
@@ -0,0 +1,229 @@
+/*
+ * Encryption policy functions for per-file encryption support.
+ *
+ * Copyright (C) 2015, Google, Inc.
+ * Copyright (C) 2015, Motorola Mobility.
+ *
+ * Written by Michael Halcrow, 2015.
+ * Modified by Jaegeuk Kim, 2015.
+ */
+
+#include <linux/random.h>
+#include <linux/string.h>
+#include <linux/fscrypto.h>
+
+static int inode_has_encryption_context(struct inode *inode)
+{
+ if (!inode->i_sb->s_cop->get_context)
+ return 0;
+ return (inode->i_sb->s_cop->get_context(inode, NULL, 0L) > 0);
+}
+
+/*
+ * check whether the policy is consistent with the encryption context
+ * for the inode
+ */
+static int is_encryption_context_consistent_with_policy(struct inode *inode,
+ const struct fscrypt_policy *policy)
+{
+ struct fscrypt_context ctx;
+ int res;
+
+ if (!inode->i_sb->s_cop->get_context)
+ return 0;
+
+ res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
+ if (res != sizeof(ctx))
+ return 0;
+
+ return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
+ FS_KEY_DESCRIPTOR_SIZE) == 0 &&
+ (ctx.flags == policy->flags) &&
+ (ctx.contents_encryption_mode ==
+ policy->contents_encryption_mode) &&
+ (ctx.filenames_encryption_mode ==
+ policy->filenames_encryption_mode));
+}
+
+static int create_encryption_context_from_policy(struct inode *inode,
+ const struct fscrypt_policy *policy)
+{
+ struct fscrypt_context ctx;
+ int res;
+
+ if (!inode->i_sb->s_cop->set_context)
+ return -EOPNOTSUPP;
+
+ if (inode->i_sb->s_cop->prepare_context) {
+ res = inode->i_sb->s_cop->prepare_context(inode);
+ if (res)
+ return res;
+ }
+
+ ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
+ memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
+ FS_KEY_DESCRIPTOR_SIZE);
+
+ if (!fscrypt_valid_contents_enc_mode(
+ policy->contents_encryption_mode)) {
+ printk(KERN_WARNING
+ "%s: Invalid contents encryption mode %d\n", __func__,
+ policy->contents_encryption_mode);
+ return -EINVAL;
+ }
+
+ if (!fscrypt_valid_filenames_enc_mode(
+ policy->filenames_encryption_mode)) {
+ printk(KERN_WARNING
+ "%s: Invalid filenames encryption mode %d\n", __func__,
+ policy->filenames_encryption_mode);
+ return -EINVAL;
+ }
+
+ if (policy->flags & ~FS_POLICY_FLAGS_VALID)
+ return -EINVAL;
+
+ ctx.contents_encryption_mode = policy->contents_encryption_mode;
+ ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
+ ctx.flags = policy->flags;
+ BUILD_BUG_ON(sizeof(ctx.nonce) != FS_KEY_DERIVATION_NONCE_SIZE);
+ get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
+
+ return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL);
+}
+
+int fscrypt_process_policy(struct inode *inode,
+ const struct fscrypt_policy *policy)
+{
+ if (policy->version != 0)
+ return -EINVAL;
+
+ if (!inode_has_encryption_context(inode)) {
+ if (!inode->i_sb->s_cop->empty_dir)
+ return -EOPNOTSUPP;
+ if (!inode->i_sb->s_cop->empty_dir(inode))
+ return -ENOTEMPTY;
+ return create_encryption_context_from_policy(inode, policy);
+ }
+
+ if (is_encryption_context_consistent_with_policy(inode, policy))
+ return 0;
+
+ printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
+ __func__);
+ return -EINVAL;
+}
+EXPORT_SYMBOL(fscrypt_process_policy);
+
+int fscrypt_get_policy(struct inode *inode, struct fscrypt_policy *policy)
+{
+ struct fscrypt_context ctx;
+ int res;
+
+ if (!inode->i_sb->s_cop->get_context ||
+ !inode->i_sb->s_cop->is_encrypted(inode))
+ return -ENODATA;
+
+ res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
+ if (res != sizeof(ctx))
+ return -ENODATA;
+ if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
+ return -EINVAL;
+
+ policy->version = 0;
+ policy->contents_encryption_mode = ctx.contents_encryption_mode;
+ policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
+ policy->flags = ctx.flags;
+ memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
+ FS_KEY_DESCRIPTOR_SIZE);
+ return 0;
+}
+EXPORT_SYMBOL(fscrypt_get_policy);
+
+int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
+{
+ struct fscrypt_info *parent_ci, *child_ci;
+ int res;
+
+ if ((parent == NULL) || (child == NULL)) {
+ printk(KERN_ERR "parent %p child %p\n", parent, child);
+ BUG_ON(1);
+ }
+
+ /* no restrictions if the parent directory is not encrypted */
+ if (!parent->i_sb->s_cop->is_encrypted(parent))
+ return 1;
+ /* if the child directory is not encrypted, this is always a problem */
+ if (!parent->i_sb->s_cop->is_encrypted(child))
+ return 0;
+ res = fscrypt_get_encryption_info(parent);
+ if (res)
+ return 0;
+ res = fscrypt_get_encryption_info(child);
+ if (res)
+ return 0;
+ parent_ci = parent->i_crypt_info;
+ child_ci = child->i_crypt_info;
+ if (!parent_ci && !child_ci)
+ return 1;
+ if (!parent_ci || !child_ci)
+ return 0;
+
+ return (memcmp(parent_ci->ci_master_key,
+ child_ci->ci_master_key,
+ FS_KEY_DESCRIPTOR_SIZE) == 0 &&
+ (parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
+ (parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
+ (parent_ci->ci_flags == child_ci->ci_flags));
+}
+EXPORT_SYMBOL(fscrypt_has_permitted_context);
+
+/**
+ * fscrypt_inherit_context() - Sets a child context from its parent
+ * @parent: Parent inode from which the context is inherited.
+ * @child: Child inode that inherits the context from @parent.
+ * @fs_data: private data given by FS.
+ * @preload: preload child i_crypt_info
+ *
+ * Return: Zero on success, non-zero otherwise
+ */
+int fscrypt_inherit_context(struct inode *parent, struct inode *child,
+ void *fs_data, bool preload)
+{
+ struct fscrypt_context ctx;
+ struct fscrypt_info *ci;
+ int res;
+
+ if (!parent->i_sb->s_cop->set_context)
+ return -EOPNOTSUPP;
+
+ res = fscrypt_get_encryption_info(parent);
+ if (res < 0)
+ return res;
+
+ ci = parent->i_crypt_info;
+ if (ci == NULL)
+ return -ENOKEY;
+
+ ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
+ if (fscrypt_dummy_context_enabled(parent)) {
+ ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
+ ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
+ ctx.flags = 0;
+ memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
+ res = 0;
+ } else {
+ ctx.contents_encryption_mode = ci->ci_data_mode;
+ ctx.filenames_encryption_mode = ci->ci_filename_mode;
+ ctx.flags = ci->ci_flags;
+ memcpy(ctx.master_key_descriptor, ci->ci_master_key,
+ FS_KEY_DESCRIPTOR_SIZE);
+ }
+ get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
+ res = parent->i_sb->s_cop->set_context(child, &ctx,
+ sizeof(ctx), fs_data);
+ if (res)
+ return res;
+ return preload ? fscrypt_get_encryption_info(child): 0;
+}
+EXPORT_SYMBOL(fscrypt_inherit_context);
diff --git a/include/linux/fscrypto.h b/include/linux/fscrypto.h
index 09fbcfb..5b18b89 100644
--- a/include/linux/fscrypto.h
+++ b/include/linux/fscrypto.h
@@ -251,6 +251,12 @@ void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *,
struct bio *);
void fscrypt_pullback_bio_page(struct page **, bool);
void fscrypt_restore_control_page(struct page *);
int fscrypt_zeroout_range(struct inode *, pgoff_t, sector_t, unsigned int);
+
+/* policy.c */
+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);
#else
/* crypto.c */
static inline struct fscrypt_ctx *fscrypt_get_ctx(struct inode *i)
@@ -294,5 +300,29 @@ static inline int fscrypt_zeroout_range(struct inode *i,
pgoff_t p,
{
return -EOPNOTSUPP;
}
+
+/* policy.c */
+static inline int fscrypt_process_policy(struct inode *i,
+ const struct fscrypt_policy *p)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline int fscrypt_get_policy(struct inode *i, struct fscrypt_policy *p)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline int fscrypt_has_permitted_context(struct inode *p,
+ struct inode *i)
+{
+ return 0;
+}
+
+static inline int fscrypt_inherit_context(struct inode *p, struct inode *i,
+ void *v, bool b)
+{
+ return -EOPNOTSUPP;
+}
#endif
#endif /* _LINUX_FSCRYPTO_H */
--
2.6.3
------------------------------------------------------------------------------
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