diff mbox series

[RFC,v2,18/18] ceph: create symlinks with encrypted and base64-encoded targets

Message ID 20200904160537.76663-19-jlayton@kernel.org
State Superseded
Headers show
Series ceph+fscrypt: context, filename and symlink support | expand

Commit Message

Jeff Layton Sept. 4, 2020, 4:05 p.m. UTC
When creating symlinks in encrypted directories, encrypt and
base64-encode the target with the new inode's key before sending to the
MDS.

When filling a symlinked inode, base64-decode it into a buffer that
we'll keep in ci->i_symlink. When get_link is called, decrypt the buffer
into a new one that will hang off i_link.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/ceph/dir.c   | 32 ++++++++++++++++---
 fs/ceph/inode.c | 82 +++++++++++++++++++++++++++++++++++++++----------
 fs/ceph/super.h |  3 ++
 3 files changed, 96 insertions(+), 21 deletions(-)

Comments

Jeff Layton Sept. 4, 2020, 4:11 p.m. UTC | #1
On Fri, 2020-09-04 at 12:05 -0400, Jeff Layton wrote:
> When creating symlinks in encrypted directories, encrypt and
> base64-encode the target with the new inode's key before sending to the
> MDS.
> 
> When filling a symlinked inode, base64-decode it into a buffer that
> we'll keep in ci->i_symlink. When get_link is called, decrypt the buffer
> into a new one that will hang off i_link.
> 
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  fs/ceph/dir.c   | 32 ++++++++++++++++---
>  fs/ceph/inode.c | 82 +++++++++++++++++++++++++++++++++++++++----------
>  fs/ceph/super.h |  3 ++
>  3 files changed, 96 insertions(+), 21 deletions(-)
> 

FWIW, this patch is not working right, and I'm not sure why.

I've validated that I'm getting the same crypttext out
of fscrypt_encrypt_symlink that I'm feeding into fscrypt_get_symlink,
but the contents always look like gibberish in a readlink.

Did I make an obvious mistake somewhere?


> diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
> index 0ba17c592fe1..7ff8921dd3a7 100644
> --- a/fs/ceph/dir.c
> +++ b/fs/ceph/dir.c
> @@ -948,6 +948,7 @@ static int ceph_symlink(struct inode *dir, struct dentry *dentry,
>  	struct ceph_mds_client *mdsc = fsc->mdsc;
>  	struct ceph_mds_request *req;
>  	struct ceph_acl_sec_ctx as_ctx = {};
> +	struct fscrypt_str osd_link = FSTR_INIT(NULL, 0);
>  	umode_t mode = S_IFLNK | 0777;
>  	int err;
>  
> @@ -973,11 +974,33 @@ static int ceph_symlink(struct inode *dir, struct dentry *dentry,
>  		goto out_req;
>  	}
>  
> -	req->r_path2 = kstrdup(dest, GFP_KERNEL);
> -	if (!req->r_path2) {
> -		err = -ENOMEM;
> -		goto out_req;
> +	if (IS_ENCRYPTED(req->r_new_inode)) {
> +		int len = strlen(dest);
> +
> +		err = fscrypt_prepare_symlink(dir, dest, len, PATH_MAX, &osd_link);
> +		if (err)
> +			goto out_req;
> +
> +		err = fscrypt_encrypt_symlink(req->r_new_inode, dest, len, &osd_link);
> +		if (err)
> +			goto out_req;
> +
> +		req->r_path2 = kmalloc(BASE64_CHARS(osd_link.len) + 1, GFP_KERNEL);
> +		if (!req->r_path2) {
> +			err = -ENOMEM;
> +			goto out_req;
> +		}
> +
> +		len = base64_encode_fname(osd_link.name, osd_link.len, req->r_path2);
> +		req->r_path2[len] = '\0';
> +	} else {
> +		req->r_path2 = kstrdup(dest, GFP_KERNEL);
> +		if (!req->r_path2) {
> +			err = -ENOMEM;
> +			goto out_req;
> +		}
>  	}
> +
>  	req->r_parent = dir;
>  	set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
>  	req->r_dentry = dget(dentry);
> @@ -997,6 +1020,7 @@ static int ceph_symlink(struct inode *dir, struct dentry *dentry,
>  	if (err)
>  		d_drop(dentry);
>  	ceph_release_acl_sec_ctx(&as_ctx);
> +	fscrypt_fname_free_buffer(&osd_link);
>  	return err;
>  }
>  
> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> index e578e4cdcf30..dd39f886b03c 100644
> --- a/fs/ceph/inode.c
> +++ b/fs/ceph/inode.c
> @@ -14,6 +14,7 @@
>  #include <linux/random.h>
>  #include <linux/sort.h>
>  #include <linux/iversion.h>
> +#include <linux/base64_fname.h>
>  
>  #include "super.h"
>  #include "mds_client.h"
> @@ -33,8 +34,6 @@
>   * (typically because they are in the message handler path).
>   */
>  
> -static const struct inode_operations ceph_symlink_iops;
> -
>  static void ceph_inode_work(struct work_struct *work);
>  
>  /*
> @@ -503,6 +502,7 @@ struct inode *ceph_alloc_inode(struct super_block *sb)
>  	atomic64_set(&ci->i_complete_seq[0], 0);
>  	atomic64_set(&ci->i_complete_seq[1], 0);
>  	ci->i_symlink = NULL;
> +	ci->i_symlink_len = 0;
>  
>  	ci->i_max_bytes = 0;
>  	ci->i_max_files = 0;
> @@ -590,6 +590,7 @@ void ceph_free_inode(struct inode *inode)
>  	struct ceph_inode_info *ci = ceph_inode(inode);
>  
>  	kfree(ci->i_symlink);
> +	fscrypt_free_inode(inode);
>  	kmem_cache_free(ceph_inode_cachep, ci);
>  }
>  
> @@ -991,34 +992,60 @@ int ceph_fill_inode(struct inode *inode, struct page *locked_page,
>  		inode->i_fop = &ceph_file_fops;
>  		break;
>  	case S_IFLNK:
> -		inode->i_op = &ceph_symlink_iops;
>  		if (!ci->i_symlink) {
>  			u32 symlen = iinfo->symlink_len;
>  			char *sym;
>  
>  			spin_unlock(&ci->i_ceph_lock);
>  
> -			if (symlen != i_size_read(inode)) {
> -				pr_err("%s %llx.%llx BAD symlink "
> -					"size %lld\n", __func__,
> -					ceph_vinop(inode),
> -					i_size_read(inode));
> +			if (IS_ENCRYPTED(inode)) {
> +				/* Do base64 decode so that we get the right size (maybe?) */
> +				err = -ENOMEM;
> +				sym = kmalloc(symlen + 1, GFP_NOFS);
> +				if (!sym)
> +					goto out;
> +
> +				symlen = base64_decode_fname(iinfo->symlink, symlen, sym);
> +				/*
> +				 * i_size as reported by the MDS may be wrong, due to base64
> +				 * inflation and padding. Fix it up here.
> +				 */
>  				i_size_write(inode, symlen);
>  				inode->i_blocks = calc_inode_blocks(symlen);
> -			}
> +			} else {
> +				if (symlen != i_size_read(inode)) {
> +					pr_err("%s %llx.%llx BAD symlink size %lld\n",
> +						__func__, ceph_vinop(inode), i_size_read(inode));
> +					i_size_write(inode, symlen);
> +					inode->i_blocks = calc_inode_blocks(symlen);
> +				}
>  
> -			err = -ENOMEM;
> -			sym = kstrndup(iinfo->symlink, symlen, GFP_NOFS);
> -			if (!sym)
> -				goto out;
> +				err = -ENOMEM;
> +				sym = kstrndup(iinfo->symlink, symlen, GFP_NOFS);
> +				if (!sym)
> +					goto out;
> +			}
>  
>  			spin_lock(&ci->i_ceph_lock);
> -			if (!ci->i_symlink)
> +			if (!ci->i_symlink) {
>  				ci->i_symlink = sym;
> -			else
> +				ci->i_symlink_len = symlen;
> +			} else {
>  				kfree(sym); /* lost a race */
> +			}
> +		}
> +
> +		if (IS_ENCRYPTED(inode)) {
> +			/*
> +			 * Encrypted symlinks need to be decrypted before we can
> +			 * cache their targets in i_link. Leave it blank for now.
> +			 */
> +			inode->i_link = NULL;
> +			inode->i_op = &ceph_encrypted_symlink_iops;
> +		} else {
> +			inode->i_link = ci->i_symlink;
> +			inode->i_op = &ceph_symlink_iops;
>  		}
> -		inode->i_link = ci->i_symlink;
>  		break;
>  	case S_IFDIR:
>  		inode->i_op = &ceph_dir_iops;
> @@ -2123,16 +2150,37 @@ static void ceph_inode_work(struct work_struct *work)
>  	iput(inode);
>  }
>  
> +static const char *ceph_encrypted_get_link(struct dentry *dentry, struct inode *inode,
> +					   struct delayed_call *done)
> +{
> +	struct ceph_inode_info *ci = ceph_inode(inode);
> +
> +	if (inode->i_link)
> +		return inode->i_link;
> +
> +	if (!dentry)
> +		return ERR_PTR(-ECHILD);
> +
> +	return fscrypt_get_symlink(inode, ci->i_symlink, ci->i_symlink_len, done);
> +}
> +
>  /*
>   * symlinks
>   */
> -static const struct inode_operations ceph_symlink_iops = {
> +const struct inode_operations ceph_symlink_iops = {
>  	.get_link = simple_get_link,
>  	.setattr = ceph_setattr,
>  	.getattr = ceph_getattr,
>  	.listxattr = ceph_listxattr,
>  };
>  
> +const struct inode_operations ceph_encrypted_symlink_iops = {
> +	.get_link = ceph_encrypted_get_link,
> +	.setattr = ceph_setattr,
> +	.getattr = ceph_getattr,
> +	.listxattr = ceph_listxattr,
> +};
> +
>  int __ceph_setattr(struct inode *inode, struct iattr *attr)
>  {
>  	struct ceph_inode_info *ci = ceph_inode(inode);
> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> index 7c859824f64c..eea0ee17b747 100644
> --- a/fs/ceph/super.h
> +++ b/fs/ceph/super.h
> @@ -344,6 +344,7 @@ struct ceph_inode_info {
>  	u64 i_max_bytes, i_max_files;
>  
>  	s32 i_dir_pin;
> +	u32 i_symlink_len;
>  
>  	struct rb_root i_fragtree;
>  	int i_fragtree_nsplits;
> @@ -932,6 +933,8 @@ struct ceph_mds_reply_dirfrag;
>  struct ceph_acl_sec_ctx;
>  
>  extern const struct inode_operations ceph_file_iops;
> +extern const struct inode_operations ceph_symlink_iops;
> +extern const struct inode_operations ceph_encrypted_symlink_iops;
>  
>  extern struct inode *ceph_alloc_inode(struct super_block *sb);
>  extern void ceph_evict_inode(struct inode *inode);
Eric Biggers Sept. 8, 2020, 5:43 a.m. UTC | #2
On Fri, Sep 04, 2020 at 12:05:37PM -0400, Jeff Layton wrote:
> +static const char *ceph_encrypted_get_link(struct dentry *dentry, struct inode *inode,
> +					   struct delayed_call *done)
> +{
> +	struct ceph_inode_info *ci = ceph_inode(inode);
> +
> +	if (inode->i_link)
> +		return inode->i_link;

Checking ->i_link here is unnecessary since the VFS already does it before
calling inode_operations::get_link().  It's also wrong since it's missing
READ_ONCE() to handle ->i_link being set concurrently.

- Eric
diff mbox series

Patch

diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index 0ba17c592fe1..7ff8921dd3a7 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -948,6 +948,7 @@  static int ceph_symlink(struct inode *dir, struct dentry *dentry,
 	struct ceph_mds_client *mdsc = fsc->mdsc;
 	struct ceph_mds_request *req;
 	struct ceph_acl_sec_ctx as_ctx = {};
+	struct fscrypt_str osd_link = FSTR_INIT(NULL, 0);
 	umode_t mode = S_IFLNK | 0777;
 	int err;
 
@@ -973,11 +974,33 @@  static int ceph_symlink(struct inode *dir, struct dentry *dentry,
 		goto out_req;
 	}
 
-	req->r_path2 = kstrdup(dest, GFP_KERNEL);
-	if (!req->r_path2) {
-		err = -ENOMEM;
-		goto out_req;
+	if (IS_ENCRYPTED(req->r_new_inode)) {
+		int len = strlen(dest);
+
+		err = fscrypt_prepare_symlink(dir, dest, len, PATH_MAX, &osd_link);
+		if (err)
+			goto out_req;
+
+		err = fscrypt_encrypt_symlink(req->r_new_inode, dest, len, &osd_link);
+		if (err)
+			goto out_req;
+
+		req->r_path2 = kmalloc(BASE64_CHARS(osd_link.len) + 1, GFP_KERNEL);
+		if (!req->r_path2) {
+			err = -ENOMEM;
+			goto out_req;
+		}
+
+		len = base64_encode_fname(osd_link.name, osd_link.len, req->r_path2);
+		req->r_path2[len] = '\0';
+	} else {
+		req->r_path2 = kstrdup(dest, GFP_KERNEL);
+		if (!req->r_path2) {
+			err = -ENOMEM;
+			goto out_req;
+		}
 	}
+
 	req->r_parent = dir;
 	set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
 	req->r_dentry = dget(dentry);
@@ -997,6 +1020,7 @@  static int ceph_symlink(struct inode *dir, struct dentry *dentry,
 	if (err)
 		d_drop(dentry);
 	ceph_release_acl_sec_ctx(&as_ctx);
+	fscrypt_fname_free_buffer(&osd_link);
 	return err;
 }
 
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index e578e4cdcf30..dd39f886b03c 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -14,6 +14,7 @@ 
 #include <linux/random.h>
 #include <linux/sort.h>
 #include <linux/iversion.h>
+#include <linux/base64_fname.h>
 
 #include "super.h"
 #include "mds_client.h"
@@ -33,8 +34,6 @@ 
  * (typically because they are in the message handler path).
  */
 
-static const struct inode_operations ceph_symlink_iops;
-
 static void ceph_inode_work(struct work_struct *work);
 
 /*
@@ -503,6 +502,7 @@  struct inode *ceph_alloc_inode(struct super_block *sb)
 	atomic64_set(&ci->i_complete_seq[0], 0);
 	atomic64_set(&ci->i_complete_seq[1], 0);
 	ci->i_symlink = NULL;
+	ci->i_symlink_len = 0;
 
 	ci->i_max_bytes = 0;
 	ci->i_max_files = 0;
@@ -590,6 +590,7 @@  void ceph_free_inode(struct inode *inode)
 	struct ceph_inode_info *ci = ceph_inode(inode);
 
 	kfree(ci->i_symlink);
+	fscrypt_free_inode(inode);
 	kmem_cache_free(ceph_inode_cachep, ci);
 }
 
@@ -991,34 +992,60 @@  int ceph_fill_inode(struct inode *inode, struct page *locked_page,
 		inode->i_fop = &ceph_file_fops;
 		break;
 	case S_IFLNK:
-		inode->i_op = &ceph_symlink_iops;
 		if (!ci->i_symlink) {
 			u32 symlen = iinfo->symlink_len;
 			char *sym;
 
 			spin_unlock(&ci->i_ceph_lock);
 
-			if (symlen != i_size_read(inode)) {
-				pr_err("%s %llx.%llx BAD symlink "
-					"size %lld\n", __func__,
-					ceph_vinop(inode),
-					i_size_read(inode));
+			if (IS_ENCRYPTED(inode)) {
+				/* Do base64 decode so that we get the right size (maybe?) */
+				err = -ENOMEM;
+				sym = kmalloc(symlen + 1, GFP_NOFS);
+				if (!sym)
+					goto out;
+
+				symlen = base64_decode_fname(iinfo->symlink, symlen, sym);
+				/*
+				 * i_size as reported by the MDS may be wrong, due to base64
+				 * inflation and padding. Fix it up here.
+				 */
 				i_size_write(inode, symlen);
 				inode->i_blocks = calc_inode_blocks(symlen);
-			}
+			} else {
+				if (symlen != i_size_read(inode)) {
+					pr_err("%s %llx.%llx BAD symlink size %lld\n",
+						__func__, ceph_vinop(inode), i_size_read(inode));
+					i_size_write(inode, symlen);
+					inode->i_blocks = calc_inode_blocks(symlen);
+				}
 
-			err = -ENOMEM;
-			sym = kstrndup(iinfo->symlink, symlen, GFP_NOFS);
-			if (!sym)
-				goto out;
+				err = -ENOMEM;
+				sym = kstrndup(iinfo->symlink, symlen, GFP_NOFS);
+				if (!sym)
+					goto out;
+			}
 
 			spin_lock(&ci->i_ceph_lock);
-			if (!ci->i_symlink)
+			if (!ci->i_symlink) {
 				ci->i_symlink = sym;
-			else
+				ci->i_symlink_len = symlen;
+			} else {
 				kfree(sym); /* lost a race */
+			}
+		}
+
+		if (IS_ENCRYPTED(inode)) {
+			/*
+			 * Encrypted symlinks need to be decrypted before we can
+			 * cache their targets in i_link. Leave it blank for now.
+			 */
+			inode->i_link = NULL;
+			inode->i_op = &ceph_encrypted_symlink_iops;
+		} else {
+			inode->i_link = ci->i_symlink;
+			inode->i_op = &ceph_symlink_iops;
 		}
-		inode->i_link = ci->i_symlink;
 		break;
 	case S_IFDIR:
 		inode->i_op = &ceph_dir_iops;
@@ -2123,16 +2150,37 @@  static void ceph_inode_work(struct work_struct *work)
 	iput(inode);
 }
 
+static const char *ceph_encrypted_get_link(struct dentry *dentry, struct inode *inode,
+					   struct delayed_call *done)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+
+	if (inode->i_link)
+		return inode->i_link;
+
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
+	return fscrypt_get_symlink(inode, ci->i_symlink, ci->i_symlink_len, done);
+}
+
 /*
  * symlinks
  */
-static const struct inode_operations ceph_symlink_iops = {
+const struct inode_operations ceph_symlink_iops = {
 	.get_link = simple_get_link,
 	.setattr = ceph_setattr,
 	.getattr = ceph_getattr,
 	.listxattr = ceph_listxattr,
 };
 
+const struct inode_operations ceph_encrypted_symlink_iops = {
+	.get_link = ceph_encrypted_get_link,
+	.setattr = ceph_setattr,
+	.getattr = ceph_getattr,
+	.listxattr = ceph_listxattr,
+};
+
 int __ceph_setattr(struct inode *inode, struct iattr *attr)
 {
 	struct ceph_inode_info *ci = ceph_inode(inode);
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 7c859824f64c..eea0ee17b747 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -344,6 +344,7 @@  struct ceph_inode_info {
 	u64 i_max_bytes, i_max_files;
 
 	s32 i_dir_pin;
+	u32 i_symlink_len;
 
 	struct rb_root i_fragtree;
 	int i_fragtree_nsplits;
@@ -932,6 +933,8 @@  struct ceph_mds_reply_dirfrag;
 struct ceph_acl_sec_ctx;
 
 extern const struct inode_operations ceph_file_iops;
+extern const struct inode_operations ceph_symlink_iops;
+extern const struct inode_operations ceph_encrypted_symlink_iops;
 
 extern struct inode *ceph_alloc_inode(struct super_block *sb);
 extern void ceph_evict_inode(struct inode *inode);