ceph: encode encrypted name in ceph_mdsc_build_path and dentry release

Allow ceph_mdsc_build_path to encrypt and base64 encode the filename
when the parent is encrypted and we're sending the path to the MDS. In
a similar fashion, encode encrypted dentry names if including a dentry
release in a request.

In most cases, we just encrypt the filenames and base64 encode them,
but when the name is longer than CEPH_NOHASH_NAME_MAX, we use a similar
scheme to fscrypt proper, and hash the remaning bits with sha256.

When doing this, we then send along the full crypttext of the name in
the new alternate_name field of the MClientRequest. The MDS can then
send that along in readdir responses and traces.

[ idryomov: drop duplicate include reported by Abaci Robot ]

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>

fs/ceph/caps.c

@@ -4663,6 +4663,18 @@ int ceph_encode_inode_release(void **p, struct inode *inode,
 	return ret;
 }
 
+/**
+ * ceph_encode_dentry_release - encode a dentry release into an outgoing request
+ * @p: outgoing request buffer
+ * @dentry: dentry to release
+ * @dir: dir to release it from
+ * @mds: mds that we're speaking to
+ * @drop: caps being dropped
+ * @unless: unless we have these caps
+ *
+ * Encode a dentry release into an outgoing request buffer. Returns 1 if the
+ * thing was released, or a negative error code otherwise.
+ */
 int ceph_encode_dentry_release(void **p, struct dentry *dentry,
 			       struct inode *dir,
 			       int mds, int drop, int unless)
@@ -4695,13 +4707,25 @@ int ceph_encode_dentry_release(void **p, struct dentry *dentry,
 	if (ret && di->lease_session && di->lease_session->s_mds == mds) {
 		dout("encode_dentry_release %p mds%d seq %d\n",
 		     dentry, mds, (int)di->lease_seq);
+		rel->dname_seq = cpu_to_le32(di->lease_seq);
+		__ceph_mdsc_drop_dentry_lease(dentry);
+		spin_unlock(&dentry->d_lock);
+		if (IS_ENCRYPTED(dir) && fscrypt_has_encryption_key(dir)) {
+			int ret2 = ceph_encode_encrypted_fname(dir, dentry, *p);
+
+			if (ret2 < 0)
+				return ret2;
+
+			rel->dname_len = cpu_to_le32(ret2);
+			*p += ret2;
+		} else {
 			rel->dname_len = cpu_to_le32(dentry->d_name.len);
 			memcpy(*p, dentry->d_name.name, dentry->d_name.len);
 			*p += dentry->d_name.len;
-		rel->dname_seq = cpu_to_le32(di->lease_seq);
-		__ceph_mdsc_drop_dentry_lease(dentry);
 		}
+	} else {
 		spin_unlock(&dentry->d_lock);
+	}
 	return ret;
 }
 

fs/ceph/crypto.c

@@ -191,3 +191,56 @@ void ceph_fscrypt_as_ctx_to_req(struct ceph_mds_request *req,
 {
 	swap(req->r_fscrypt_auth, as->fscrypt_auth);
 }
+
+int ceph_encode_encrypted_fname(const struct inode *parent,
+				struct dentry *dentry, char *buf)
+{
+	u32 len;
+	int elen;
+	int ret;
+	u8 *cryptbuf;
+
+	WARN_ON_ONCE(!fscrypt_has_encryption_key(parent));
+
+	/*
+	 * Convert cleartext d_name to ciphertext. If result is longer than
+	 * CEPH_NOHASH_NAME_MAX, sha256 the remaining bytes
+	 *
+	 * See: fscrypt_setup_filename
+	 */
+	if (!fscrypt_fname_encrypted_size(parent, dentry->d_name.len, NAME_MAX,
+					  &len))
+		return -ENAMETOOLONG;
+
+	/* Allocate a buffer appropriate to hold the result */
+	cryptbuf = kmalloc(len > CEPH_NOHASH_NAME_MAX ? NAME_MAX : len,
+			   GFP_KERNEL);
+	if (!cryptbuf)
+		return -ENOMEM;
+
+	ret = fscrypt_fname_encrypt(parent, &dentry->d_name, cryptbuf, len);
+	if (ret) {
+		kfree(cryptbuf);
+		return ret;
+	}
+
+	/* hash the end if the name is long enough */
+	if (len > CEPH_NOHASH_NAME_MAX) {
+		u8 hash[SHA256_DIGEST_SIZE];
+		u8 *extra = cryptbuf + CEPH_NOHASH_NAME_MAX;
+
+		/*
+		 * hash the extra bytes and overwrite crypttext beyond that
+		 * point with it
+		 */
+		sha256(extra, len - CEPH_NOHASH_NAME_MAX, hash);
+		memcpy(extra, hash, SHA256_DIGEST_SIZE);
+		len = CEPH_NOHASH_NAME_MAX + SHA256_DIGEST_SIZE;
+	}
+
+	/* base64 encode the encrypted name */
+	elen = ceph_base64_encode(cryptbuf, len, buf);
+	kfree(cryptbuf);
+	dout("base64-encoded ciphertext name = %.*s\n", elen, buf);
+	return elen;
+}

fs/ceph/crypto.h

@@ -6,6 +6,7 @@
 #ifndef _CEPH_CRYPTO_H
 #define _CEPH_CRYPTO_H
 
+#include <crypto/sha2.h>
 #include <linux/fscrypt.h>
 
 struct ceph_fs_client;
@@ -67,6 +68,8 @@ int ceph_fscrypt_prepare_context(struct inode *dir, struct inode *inode,
 				 struct ceph_acl_sec_ctx *as);
 void ceph_fscrypt_as_ctx_to_req(struct ceph_mds_request *req,
 				struct ceph_acl_sec_ctx *as);
+int ceph_encode_encrypted_fname(const struct inode *parent,
+				struct dentry *dentry, char *buf);
 
 #else /* CONFIG_FS_ENCRYPTION */
 
@@ -91,6 +94,12 @@ static inline void ceph_fscrypt_as_ctx_to_req(struct ceph_mds_request *req,
 						struct ceph_acl_sec_ctx *as_ctx)
 {
 }
+
+static inline int ceph_encode_encrypted_fname(const struct inode *parent,
+					      struct dentry *dentry, char *buf)
+{
+	return -EOPNOTSUPP;
+}
 #endif /* CONFIG_FS_ENCRYPTION */
 
 #endif

fs/ceph/mds_client.c

@@ -2435,18 +2435,29 @@ static inline  u64 __get_oldest_tid(struct ceph_mds_client *mdsc)
 	return mdsc->oldest_tid;
 }
 
-/*
+/**
- * Build a dentry's path.  Allocate on heap; caller must kfree.  Based
+ * ceph_mdsc_build_path - build a path string to a given dentry
- * on build_path_from_dentry in fs/cifs/dir.c.
+ * @dentry: dentry to which path should be built
+ * @plen: returned length of string
+ * @pbase: returned base inode number
+ * @for_wire: is this path going to be sent to the MDS?
  *
- * If @stop_on_nosnap, generate path relative to the first non-snapped
+ * Build a string that represents the path to the dentry. This is mostly called
- * inode.
+ * for two different purposes:
+ *
+ * 1) we need to build a path string to send to the MDS (for_wire == true)
+ * 2) we need a path string for local presentation (e.g. debugfs)
+ *    (for_wire == false)
+ *
+ * The path is built in reverse, starting with the dentry. Walk back up toward
+ * the root, building the path until the first non-snapped inode is reached
+ * (for_wire) or the root inode is reached (!for_wire).
  *
  * Encode hidden .snap dirs as a double /, i.e.
  *   foo/.snap/bar -> foo//bar
  */
 char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase,
-			   int stop_on_nosnap)
+			   int for_wire)
 {
 	struct dentry *cur;
 	struct inode *inode;
@@ -2468,30 +2479,67 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase,
 	seq = read_seqbegin(&rename_lock);
 	cur = dget(dentry);
 	for (;;) {
-		struct dentry *temp;
+		struct dentry *parent;
 
 		spin_lock(&cur->d_lock);
 		inode = d_inode(cur);
 		if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {
 			dout("build_path path+%d: %p SNAPDIR\n",
 			     pos, cur);
-		} else if (stop_on_nosnap && inode && dentry != cur &&
+			spin_unlock(&cur->d_lock);
+			parent = dget_parent(cur);
+		} else if (for_wire && inode && dentry != cur &&
 			   ceph_snap(inode) == CEPH_NOSNAP) {
 			spin_unlock(&cur->d_lock);
 			pos++; /* get rid of any prepended '/' */
 			break;
-		} else {
+		} else if (!for_wire || !IS_ENCRYPTED(d_inode(cur->d_parent))) {
 			pos -= cur->d_name.len;
 			if (pos < 0) {
 				spin_unlock(&cur->d_lock);
 				break;
 			}
 			memcpy(path + pos, cur->d_name.name, cur->d_name.len);
+			spin_unlock(&cur->d_lock);
+			parent = dget_parent(cur);
+		} else {
+			int len, ret;
+			char buf[NAME_MAX];
+
+			/*
+			 * Proactively copy name into buf, in case we need to
+			 * present it as-is.
+			 */
+			memcpy(buf, cur->d_name.name, cur->d_name.len);
+			len = cur->d_name.len;
+			spin_unlock(&cur->d_lock);
+			parent = dget_parent(cur);
+
+			ret = __fscrypt_prepare_readdir(d_inode(parent));
+			if (ret < 0) {
+				dput(parent);
+				dput(cur);
+				return ERR_PTR(ret);
 			}
-		temp = cur;
+
-		spin_unlock(&temp->d_lock);
+			if (fscrypt_has_encryption_key(d_inode(parent))) {
-		cur = dget_parent(temp);
+				len = ceph_encode_encrypted_fname(d_inode(parent),
-		dput(temp);
+								  cur, buf);
+				if (len < 0) {
+					dput(parent);
+					dput(cur);
+					return ERR_PTR(len);
+				}
+			}
+			pos -= len;
+			if (pos < 0) {
+				dput(parent);
+				break;
+			}
+			memcpy(path + pos, buf, len);
+		}
+		dput(cur);
+		cur = parent;
 
 		/* Are we at the root? */
 		if (IS_ROOT(cur))
@@ -2515,8 +2563,8 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase,
 		 * A rename didn't occur, but somehow we didn't end up where
 		 * we thought we would. Throw a warning and try again.
 		 */
-		pr_warn("build_path did not end path lookup where "
+		pr_warn("build_path did not end path lookup where expected (pos = %d)\n",
-			"expected, pos is %d\n", pos);
+			pos);
 		goto retry;
 	}
 
@@ -2536,7 +2584,8 @@ static int build_dentry_path(struct dentry *dentry, struct inode *dir,
 	rcu_read_lock();
 	if (!dir)
 		dir = d_inode_rcu(dentry->d_parent);
-	if (dir && parent_locked && ceph_snap(dir) == CEPH_NOSNAP) {
+	if (dir && parent_locked && ceph_snap(dir) == CEPH_NOSNAP &&
+	    !IS_ENCRYPTED(dir)) {
 		*pino = ceph_ino(dir);
 		rcu_read_unlock();
 		*ppath = dentry->d_name.name;
@@ -2765,15 +2814,23 @@ static struct ceph_msg *create_request_message(struct ceph_mds_session *session,
 		      req->r_inode ? req->r_inode : d_inode(req->r_dentry),
 		      mds, req->r_inode_drop, req->r_inode_unless,
 		      req->r_op == CEPH_MDS_OP_READDIR);
-	if (req->r_dentry_drop)
+	if (req->r_dentry_drop) {
-		releases += ceph_encode_dentry_release(&p, req->r_dentry,
+		ret = ceph_encode_dentry_release(&p, req->r_dentry,
 				req->r_parent, mds, req->r_dentry_drop,
 				req->r_dentry_unless);
-	if (req->r_old_dentry_drop)
+		if (ret < 0)
-		releases += ceph_encode_dentry_release(&p, req->r_old_dentry,
+			goto out_err;
+		releases += ret;
+	}
+	if (req->r_old_dentry_drop) {
+		ret = ceph_encode_dentry_release(&p, req->r_old_dentry,
 				req->r_old_dentry_dir, mds,
 				req->r_old_dentry_drop,
 				req->r_old_dentry_unless);
+		if (ret < 0)
+			goto out_err;
+		releases += ret;
+	}
 	if (req->r_old_inode_drop)
 		releases += ceph_encode_inode_release(&p,
 		      d_inode(req->r_old_dentry),
@@ -2815,6 +2872,10 @@ static struct ceph_msg *create_request_message(struct ceph_mds_session *session,
 		ceph_mdsc_free_path((char *)path1, pathlen1);
 out:
 	return msg;
+out_err:
+	ceph_msg_put(msg);
+	msg = ERR_PTR(ret);
+	goto out_free2;
 }
 
 /*

fs/ceph/mds_client.h

@@ -565,7 +565,7 @@ static inline void ceph_mdsc_free_path(char *path, int len)
 }
 
 extern char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *base,
-				  int stop_on_nosnap);
+				  int for_wire);
 
 extern void __ceph_mdsc_drop_dentry_lease(struct dentry *dentry);
 extern void ceph_mdsc_lease_send_msg(struct ceph_mds_session *session,