ceph: fscrypt_auth handling for ceph

Most fscrypt-enabled filesystems store the crypto context in an xattr,
but that's problematic for ceph as xatts are governed by the XATTR cap,
but we really want the crypto context as part of the AUTH cap.

Because of this, the MDS has added two new inode metadata fields:
fscrypt_auth and fscrypt_file. The former is used to hold the crypto
context, and the latter is used to track the real file size.

Parse new fscrypt_auth and fscrypt_file fields in inode traces. For now,
we don't use fscrypt_file, but fscrypt_auth is used to hold the fscrypt
context.

Allow the client to use a setattr request for setting the fscrypt_auth
field. Since this is not a standard setattr request from the VFS, we add
a new field to __ceph_setattr that carries ceph-specific inode attrs.

Have the set_context op do a setattr that sets the fscrypt_auth value,
and get_context just return the contents of that field (since it should
always be available).

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Reviewed-and-tested-by: Luís Henriques <lhenriques@suse.de>
Reviewed-by: Milind Changire <mchangir@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 62 insertions, 2 deletions

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index e23172024707..a3aa7870a6a2 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -14,10 +14,12 @@
 #include <linux/random.h>
 #include <linux/sort.h>
 #include <linux/iversion.h>
+#include <linux/fscrypt.h>
 
 #include "super.h"
 #include "mds_client.h"
 #include "cache.h"
+#include "crypto.h"
 #include <linux/ceph/decode.h>
 
 /*
@@ -617,6 +619,10 @@ struct inode *ceph_alloc_inode(struct super_block *sb)
 	INIT_WORK(&ci->i_work, ceph_inode_work);
 	ci->i_work_mask = 0;
 	memset(&ci->i_btime, '\0', sizeof(ci->i_btime));
+#ifdef CONFIG_FS_ENCRYPTION
+	ci->fscrypt_auth = NULL;
+	ci->fscrypt_auth_len = 0;
+#endif
 	return &ci->netfs.inode;
 }
 
@@ -625,6 +631,9 @@ void ceph_free_inode(struct inode *inode)
 	struct ceph_inode_info *ci = ceph_inode(inode);
 
 	kfree(ci->i_symlink);
+#ifdef CONFIG_FS_ENCRYPTION
+	kfree(ci->fscrypt_auth);
+#endif
 	kmem_cache_free(ceph_inode_cachep, ci);
 }
 
@@ -645,6 +654,7 @@ void ceph_evict_inode(struct inode *inode)
 	clear_inode(inode);
 
 	ceph_fscache_unregister_inode_cookie(ci);
+	fscrypt_put_encryption_info(inode);
 
 	__ceph_remove_caps(ci);
 
@@ -935,6 +945,17 @@ int ceph_fill_inode(struct inode *inode, struct page *locked_page,
 
 	__ceph_update_quota(ci, iinfo->max_bytes, iinfo->max_files);
 
+#ifdef CONFIG_FS_ENCRYPTION
+	if (iinfo->fscrypt_auth_len && (inode->i_state & I_NEW)) {
+		kfree(ci->fscrypt_auth);
+		ci->fscrypt_auth_len = iinfo->fscrypt_auth_len;
+		ci->fscrypt_auth = iinfo->fscrypt_auth;
+		iinfo->fscrypt_auth = NULL;
+		iinfo->fscrypt_auth_len = 0;
+		inode_set_flags(inode, S_ENCRYPTED, S_ENCRYPTED);
+	}
+#endif
+
 	if ((new_version || (new_issued & CEPH_CAP_AUTH_SHARED)) &&
 	    (issued & CEPH_CAP_AUTH_EXCL) == 0) {
 		inode->i_mode = mode;
@@ -2079,7 +2100,8 @@ static const struct inode_operations ceph_symlink_iops = {
 	.listxattr = ceph_listxattr,
 };
 
-int __ceph_setattr(struct inode *inode, struct iattr *attr)
+int __ceph_setattr(struct inode *inode, struct iattr *attr,
+		   struct ceph_iattr *cia)
 {
 	struct ceph_inode_info *ci = ceph_inode(inode);
 	unsigned int ia_valid = attr->ia_valid;
@@ -2119,6 +2141,43 @@ int __ceph_setattr(struct inode *inode, struct iattr *attr)
 	}
 
 	dout("setattr %p issued %s\n", inode, ceph_cap_string(issued));
+#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
+	if (cia && cia->fscrypt_auth) {
+		u32 len = ceph_fscrypt_auth_len(cia->fscrypt_auth);
+
+		if (len > sizeof(*cia->fscrypt_auth)) {
+			err = -EINVAL;
+			spin_unlock(&ci->i_ceph_lock);
+			goto out;
+		}
+
+		dout("setattr %llx:%llx fscrypt_auth len %u to %u)\n",
+			ceph_vinop(inode), ci->fscrypt_auth_len, len);
+
+		/* It should never be re-set once set */
+		WARN_ON_ONCE(ci->fscrypt_auth);
+
+		if (issued & CEPH_CAP_AUTH_EXCL) {
+			dirtied |= CEPH_CAP_AUTH_EXCL;
+			kfree(ci->fscrypt_auth);
+			ci->fscrypt_auth = (u8 *)cia->fscrypt_auth;
+			ci->fscrypt_auth_len = len;
+		} else if ((issued & CEPH_CAP_AUTH_SHARED) == 0 ||
+			   ci->fscrypt_auth_len != len ||
+			   memcmp(ci->fscrypt_auth, cia->fscrypt_auth, len)) {
+			req->r_fscrypt_auth = cia->fscrypt_auth;
+			mask |= CEPH_SETATTR_FSCRYPT_AUTH;
+			release |= CEPH_CAP_AUTH_SHARED;
+		}
+		cia->fscrypt_auth = NULL;
+	}
+#else
+	if (cia && cia->fscrypt_auth) {
+		err = -EINVAL;
+		spin_unlock(&ci->i_ceph_lock);
+		goto out;
+	}
+#endif /* CONFIG_FS_ENCRYPTION */
 
 	if (ia_valid & ATTR_UID) {
 		dout("setattr %p uid %d -> %d\n", inode,
@@ -2282,6 +2341,7 @@ int __ceph_setattr(struct inode *inode, struct iattr *attr)
 		req->r_stamp = attr->ia_ctime;
 		err = ceph_mdsc_do_request(mdsc, NULL, req);
 	}
+out:
 	dout("setattr %p result=%d (%s locally, %d remote)\n", inode, err,
 	     ceph_cap_string(dirtied), mask);
 
@@ -2322,7 +2382,7 @@ int ceph_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 	    ceph_quota_is_max_bytes_exceeded(inode, attr->ia_size))
 		return -EDQUOT;
 
-	err = __ceph_setattr(inode, attr);
+	err = __ceph_setattr(inode, attr, NULL);
 
 	if (err >= 0 && (attr->ia_valid & ATTR_MODE))
 		err = posix_acl_chmod(&nop_mnt_idmap, dentry, attr->ia_mode);