[PATCH] ecryptfs: Restore support for both encrypted and unencrypted file names

[PATCH] ecryptfs: Restore support for both encrypted and unencrypted file names

[Guenter Roeck]

Commit 88ae4ab9802e ("ecryptfs_lookup(): try either only encrypted or
plaintext name") was supposed to fix a situation where two files with
the same name and same inode could be created in ecryptfs. One of those
files had an encrypted file name, the other file name was unencrypted.

After commit 88ae4ab9802e, having a mix of encrypted and unencrypted file
names is no longer supposed to be possible. However, that is not the case.
The only difference is that it is now even easier to create a situation
where two files with the same name coexist (one encrypted and the other
not encrypted). In practice, this looks like the following (files
created with v4.14.12).

ecryptfs mounted with file name encryption enabled:

$ ls -li
total 48
5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
$ grep . *
myfile:encrypted
myfile:encrypted
myfile2:encrypted
myfile2:encrypted

$ ls -li
total 48
5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36
ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVun.BU8Zu5-njbcIPoApxk7-E--
5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02
ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVunt0fda7t9YCtJ70cm911yZ---
5252817 -rw-rw-r-- 1 groeck groeck 12 Jan 20 12:52 myfile
5252827 -rw-rw-r-- 1 groeck groeck 12 Jan 20 15:37 myfile2

$ grep . *
ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVun.BU8Zu5-njbcIPoApxk7-E--:encrypted
ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVunt0fda7t9YCtJ70cm911yZ---:encrypted
myfile:unencrypted
myfile2:unencrypted

Creating a file with file name encryption disabled and remounting with
file name encryption enabled results in the following.

$ ls -li
ls: cannot access 'myfile3': No such file or directory
total 48
5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
      ? -????????? ? ?      ?       ?            ? myfile3

Prior to commit 88ae4ab9802e, the file system had to be mounted with
encrypted file names first to create a file, then the same had to be
repeated after mounting with unencrypted file names. Now the duplicate
files can be created both ways (unencrypted _or_ encrypted first).

The only real difference is that it is no longer possible to have a
_working_ combination of encrypted and unencrypted file names. In other
words, commit 88ae4ab9802e results in reduced functionality with no
benefit whatsoever.

Restore ability to have a mix of unencrypted and encrypted files.
This effectively reverts commit 88ae4ab9802e, but the code is now
better readable since it avoids a number of goto statements.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 fs/ecryptfs/inode.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 847904aa63a9..14a5c096ead6 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -392,11 +392,11 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
 	int rc = 0;
 
 	lower_dir_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry->d_parent);
-
+	lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry, len);
 	mount_crypt_stat = &ecryptfs_superblock_to_private(
 				ecryptfs_dentry->d_sb)->mount_crypt_stat;
-	if (mount_crypt_stat
-	    && (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
+	if (IS_ERR(lower_dentry) &&
+	    (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
 		rc = ecryptfs_encrypt_and_encode_filename(
 			&encrypted_and_encoded_name, &len,
 			mount_crypt_stat, name, len);
@@ -405,10 +405,10 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
 			       "filename; rc = [%d]\n", __func__, rc);
 			return ERR_PTR(rc);
 		}
-		name = encrypted_and_encoded_name;
+		lower_dentry = lookup_one_len_unlocked(
+			encrypted_and_encoded_name, lower_dir_dentry, len);
 	}
 
-	lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry, len);
 	if (IS_ERR(lower_dentry)) {
 		ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_len() returned "
 				"[%ld] on lower_dentry = [%s]\n", __func__,
-- 
2.7.4

Re: ecryptfs: Restore support for both encrypted and unencrypted file names

[Guenter Roeck]

ping

On Tue, Feb 13, 2018 at 02:36:08PM -0800, Guenter Roeck wrote:
> Commit 88ae4ab9802e ("ecryptfs_lookup(): try either only encrypted or
> plaintext name") was supposed to fix a situation where two files with
> the same name and same inode could be created in ecryptfs. One of those
> files had an encrypted file name, the other file name was unencrypted.
> 
> After commit 88ae4ab9802e, having a mix of encrypted and unencrypted file
> names is no longer supposed to be possible. However, that is not the case.
> The only difference is that it is now even easier to create a situation
> where two files with the same name coexist (one encrypted and the other
> not encrypted). In practice, this looks like the following (files
> created with v4.14.12).
> 
> ecryptfs mounted with file name encryption enabled:
> 
> $ ls -li
> total 48
> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
> $ grep . *
> myfile:encrypted
> myfile:encrypted
> myfile2:encrypted
> myfile2:encrypted
> 
> $ ls -li
> total 48
> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36
> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVun.BU8Zu5-njbcIPoApxk7-E--
> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02
> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVunt0fda7t9YCtJ70cm911yZ---
> 5252817 -rw-rw-r-- 1 groeck groeck 12 Jan 20 12:52 myfile
> 5252827 -rw-rw-r-- 1 groeck groeck 12 Jan 20 15:37 myfile2
> 
> $ grep . *
> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVun.BU8Zu5-njbcIPoApxk7-E--:encrypted
> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVunt0fda7t9YCtJ70cm911yZ---:encrypted
> myfile:unencrypted
> myfile2:unencrypted
> 
> Creating a file with file name encryption disabled and remounting with
> file name encryption enabled results in the following.
> 
> $ ls -li
> ls: cannot access 'myfile3': No such file or directory
> total 48
> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
>       ? -????????? ? ?      ?       ?            ? myfile3
> 
> Prior to commit 88ae4ab9802e, the file system had to be mounted with
> encrypted file names first to create a file, then the same had to be
> repeated after mounting with unencrypted file names. Now the duplicate
> files can be created both ways (unencrypted _or_ encrypted first).
> 
> The only real difference is that it is no longer possible to have a
> _working_ combination of encrypted and unencrypted file names. In other
> words, commit 88ae4ab9802e results in reduced functionality with no
> benefit whatsoever.
> 
> Restore ability to have a mix of unencrypted and encrypted files.
> This effectively reverts commit 88ae4ab9802e, but the code is now
> better readable since it avoids a number of goto statements.
> 
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>  fs/ecryptfs/inode.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
> index 847904aa63a9..14a5c096ead6 100644
> --- a/fs/ecryptfs/inode.c
> +++ b/fs/ecryptfs/inode.c
> @@ -392,11 +392,11 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
>  	int rc = 0;
>  
>  	lower_dir_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry->d_parent);
> -
> +	lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry, len);
>  	mount_crypt_stat = &ecryptfs_superblock_to_private(
>  				ecryptfs_dentry->d_sb)->mount_crypt_stat;
> -	if (mount_crypt_stat
> -	    && (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
> +	if (IS_ERR(lower_dentry) &&
> +	    (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
>  		rc = ecryptfs_encrypt_and_encode_filename(
>  			&encrypted_and_encoded_name, &len,
>  			mount_crypt_stat, name, len);
> @@ -405,10 +405,10 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
>  			       "filename; rc = [%d]\n", __func__, rc);
>  			return ERR_PTR(rc);
>  		}
> -		name = encrypted_and_encoded_name;
> +		lower_dentry = lookup_one_len_unlocked(
> +			encrypted_and_encoded_name, lower_dir_dentry, len);
>  	}
>  
> -	lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry, len);
>  	if (IS_ERR(lower_dentry)) {
>  		ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_len() returned "
>  				"[%ld] on lower_dentry = [%s]\n", __func__,

Re: [PATCH] ecryptfs: Restore support for both encrypted and unencrypted file names

[Tyler Hicks]

[-- Attachment #1.1: Type: text/plain, Size: 5468 bytes --]

Hello Guenter

On 02/13/2018 04:36 PM, Guenter Roeck wrote:
> Commit 88ae4ab9802e ("ecryptfs_lookup(): try either only encrypted or
> plaintext name") was supposed to fix a situation where two files with
> the same name and same inode could be created in ecryptfs. One of those
> files had an encrypted file name, the other file name was unencrypted.

That's correct. Al was concerned about possible deadlocks with aliased
dentries and I thought it would be best to only support encrypted and
unencrypted but not both.

> 
> After commit 88ae4ab9802e, having a mix of encrypted and unencrypted file
> names is no longer supposed to be possible. However, that is not the case.
> The only difference is that it is now even easier to create a situation
> where two files with the same name coexist (one encrypted and the other
> not encrypted). In practice, this looks like the following (files
> created with v4.14.12).
> 
> ecryptfs mounted with file name encryption enabled:
> 
> $ ls -li
> total 48
> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
> $ grep . *
> myfile:encrypted
> myfile:encrypted
> myfile2:encrypted
> myfile2:encrypted
> 
> $ ls -li
> total 48
> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36
> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVun.BU8Zu5-njbcIPoApxk7-E--
> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02
> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVunt0fda7t9YCtJ70cm911yZ---
> 5252817 -rw-rw-r-- 1 groeck groeck 12 Jan 20 12:52 myfile
> 5252827 -rw-rw-r-- 1 groeck groeck 12 Jan 20 15:37 myfile2
> 
> $ grep . *
> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVun.BU8Zu5-njbcIPoApxk7-E--:encrypted
> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVunt0fda7t9YCtJ70cm911yZ---:encrypted
> myfile:unencrypted
> myfile2:unencrypted
> 
> Creating a file with file name encryption disabled and remounting with
> file name encryption enabled results in the following.
> 
> $ ls -li
> ls: cannot access 'myfile3': No such file or directory
> total 48
> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
>       ? -????????? ? ?      ?       ?            ? myfile3
> 
> Prior to commit 88ae4ab9802e, the file system had to be mounted with
> encrypted file names first to create a file, then the same had to be
> repeated after mounting with unencrypted file names. Now the duplicate
> files can be created both ways (unencrypted _or_ encrypted first).
> 
> The only real difference is that it is no longer possible to have a
> _working_ combination of encrypted and unencrypted file names. In other
> words, commit 88ae4ab9802e results in reduced functionality with no
> benefit whatsoever.
> 
> Restore ability to have a mix of unencrypted and encrypted files.
> This effectively reverts commit 88ae4ab9802e, but the code is now
> better readable since it avoids a number of goto statements.

I'd like for us to correctly fix 88ae4ab9802e rather than try to support
both filename types under a single mount since that's complex and there
are unknown corner cases to consider. I think this can be done by not
copying up the lower filename when an error is encountered in
ecryptfs_decode_and_decrypt_filename(). If filename encryption is
enabled, it should only return decrypted filenames or an error if it
isn't possible to decrypt the lower filename.

Tyler

> 
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>  fs/ecryptfs/inode.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
> index 847904aa63a9..14a5c096ead6 100644
> --- a/fs/ecryptfs/inode.c
> +++ b/fs/ecryptfs/inode.c
> @@ -392,11 +392,11 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
>  	int rc = 0;
>  
>  	lower_dir_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry->d_parent);
> -
> +	lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry, len);
>  	mount_crypt_stat = &ecryptfs_superblock_to_private(
>  				ecryptfs_dentry->d_sb)->mount_crypt_stat;
> -	if (mount_crypt_stat
> -	    && (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
> +	if (IS_ERR(lower_dentry) &&
> +	    (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
>  		rc = ecryptfs_encrypt_and_encode_filename(
>  			&encrypted_and_encoded_name, &len,
>  			mount_crypt_stat, name, len);
> @@ -405,10 +405,10 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
>  			       "filename; rc = [%d]\n", __func__, rc);
>  			return ERR_PTR(rc);
>  		}
> -		name = encrypted_and_encoded_name;
> +		lower_dentry = lookup_one_len_unlocked(
> +			encrypted_and_encoded_name, lower_dir_dentry, len);
>  	}
>  
> -	lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry, len);
>  	if (IS_ERR(lower_dentry)) {
>  		ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_len() returned "
>  				"[%ld] on lower_dentry = [%s]\n", __func__,
> 



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Re: [PATCH] ecryptfs: Restore support for both encrypted and unencrypted file names

[Guenter Roeck]

On 03/27/2018 08:58 AM, Tyler Hicks wrote:
> Hello Guenter
> 
> On 02/13/2018 04:36 PM, Guenter Roeck wrote:
>> Commit 88ae4ab9802e ("ecryptfs_lookup(): try either only encrypted or
>> plaintext name") was supposed to fix a situation where two files with
>> the same name and same inode could be created in ecryptfs. One of those
>> files had an encrypted file name, the other file name was unencrypted.
> 
> That's correct. Al was concerned about possible deadlocks with aliased
> dentries and I thought it would be best to only support encrypted and
> unencrypted but not both.
> 
>>
>> After commit 88ae4ab9802e, having a mix of encrypted and unencrypted file
>> names is no longer supposed to be possible. However, that is not the case.
>> The only difference is that it is now even easier to create a situation
>> where two files with the same name coexist (one encrypted and the other
>> not encrypted). In practice, this looks like the following (files
>> created with v4.14.12).
>>
>> ecryptfs mounted with file name encryption enabled:
>>
>> $ ls -li
>> total 48
>> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
>> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
>> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
>> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
>> $ grep . *
>> myfile:encrypted
>> myfile:encrypted
>> myfile2:encrypted
>> myfile2:encrypted
>>
>> $ ls -li
>> total 48
>> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36
>> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVun.BU8Zu5-njbcIPoApxk7-E--
>> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02
>> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVunt0fda7t9YCtJ70cm911yZ---
>> 5252817 -rw-rw-r-- 1 groeck groeck 12 Jan 20 12:52 myfile
>> 5252827 -rw-rw-r-- 1 groeck groeck 12 Jan 20 15:37 myfile2
>>
>> $ grep . *
>> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVun.BU8Zu5-njbcIPoApxk7-E--:encrypted
>> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVunt0fda7t9YCtJ70cm911yZ---:encrypted
>> myfile:unencrypted
>> myfile2:unencrypted
>>
>> Creating a file with file name encryption disabled and remounting with
>> file name encryption enabled results in the following.
>>
>> $ ls -li
>> ls: cannot access 'myfile3': No such file or directory
>> total 48
>> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
>> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
>> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
>> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
>>        ? -????????? ? ?      ?       ?            ? myfile3
>>
>> Prior to commit 88ae4ab9802e, the file system had to be mounted with
>> encrypted file names first to create a file, then the same had to be
>> repeated after mounting with unencrypted file names. Now the duplicate
>> files can be created both ways (unencrypted _or_ encrypted first).
>>
>> The only real difference is that it is no longer possible to have a
>> _working_ combination of encrypted and unencrypted file names. In other
>> words, commit 88ae4ab9802e results in reduced functionality with no
>> benefit whatsoever.
>>
>> Restore ability to have a mix of unencrypted and encrypted files.
>> This effectively reverts commit 88ae4ab9802e, but the code is now
>> better readable since it avoids a number of goto statements.
> 
> I'd like for us to correctly fix 88ae4ab9802e rather than try to support
> both filename types under a single mount since that's complex and there
> are unknown corner cases to consider. I think this can be done by not
> copying up the lower filename when an error is encountered in
> ecryptfs_decode_and_decrypt_filename(). If filename encryption is
> enabled, it should only return decrypted filenames or an error if it
> isn't possible to decrypt the lower filename.
> 

NP. I'll leave it alone, then. Since our use case requires both encrypted
and unencrypted file names, our "fix" will be to carry this patch along
locally as long as needed and stop using ecryptfs otherwise.

Guenter

> Tyler
> 
>>
>> Cc: Al Viro <viro@zeniv.linux.org.uk>
>> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>> ---
>>   fs/ecryptfs/inode.c | 10 +++++-----
>>   1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
>> index 847904aa63a9..14a5c096ead6 100644
>> --- a/fs/ecryptfs/inode.c
>> +++ b/fs/ecryptfs/inode.c
>> @@ -392,11 +392,11 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
>>   	int rc = 0;
>>   
>>   	lower_dir_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry->d_parent);
>> -
>> +	lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry, len);
>>   	mount_crypt_stat = &ecryptfs_superblock_to_private(
>>   				ecryptfs_dentry->d_sb)->mount_crypt_stat;
>> -	if (mount_crypt_stat
>> -	    && (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
>> +	if (IS_ERR(lower_dentry) &&
>> +	    (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
>>   		rc = ecryptfs_encrypt_and_encode_filename(
>>   			&encrypted_and_encoded_name, &len,
>>   			mount_crypt_stat, name, len);
>> @@ -405,10 +405,10 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
>>   			       "filename; rc = [%d]\n", __func__, rc);
>>   			return ERR_PTR(rc);
>>   		}
>> -		name = encrypted_and_encoded_name;
>> +		lower_dentry = lookup_one_len_unlocked(
>> +			encrypted_and_encoded_name, lower_dir_dentry, len);
>>   	}
>>   
>> -	lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry, len);
>>   	if (IS_ERR(lower_dentry)) {
>>   		ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_len() returned "
>>   				"[%ld] on lower_dentry = [%s]\n", __func__,
>>
> 
> 

Re: [PATCH] ecryptfs: Restore support for both encrypted and unencrypted file names

[Tyler Hicks]

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On 03/28/2018 08:33 AM, Guenter Roeck wrote:
> On 03/27/2018 08:58 AM, Tyler Hicks wrote:
>> Hello Guenter
>>
>> On 02/13/2018 04:36 PM, Guenter Roeck wrote:
>>> Commit 88ae4ab9802e ("ecryptfs_lookup(): try either only encrypted or
>>> plaintext name") was supposed to fix a situation where two files with
>>> the same name and same inode could be created in ecryptfs. One of those
>>> files had an encrypted file name, the other file name was unencrypted.
>>
>> That's correct. Al was concerned about possible deadlocks with aliased
>> dentries and I thought it would be best to only support encrypted and
>> unencrypted but not both.
>>
>>>
>>> After commit 88ae4ab9802e, having a mix of encrypted and unencrypted
>>> file
>>> names is no longer supposed to be possible. However, that is not the
>>> case.
>>> The only difference is that it is now even easier to create a situation
>>> where two files with the same name coexist (one encrypted and the other
>>> not encrypted). In practice, this looks like the following (files
>>> created with v4.14.12).
>>>
>>> ecryptfs mounted with file name encryption enabled:
>>>
>>> $ ls -li
>>> total 48
>>> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
>>> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
>>> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
>>> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
>>> $ grep . *
>>> myfile:encrypted
>>> myfile:encrypted
>>> myfile2:encrypted
>>> myfile2:encrypted
>>>
>>> $ ls -li
>>> total 48
>>> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36
>>> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVun.BU8Zu5-njbcIPoApxk7-E--
>>>
>>> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02
>>> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVunt0fda7t9YCtJ70cm911yZ---
>>>
>>> 5252817 -rw-rw-r-- 1 groeck groeck 12 Jan 20 12:52 myfile
>>> 5252827 -rw-rw-r-- 1 groeck groeck 12 Jan 20 15:37 myfile2
>>>
>>> $ grep . *
>>> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVun.BU8Zu5-njbcIPoApxk7-E--:encrypted
>>>
>>> ECRYPTFS_FNEK_ENCRYPTED.FWbF9U6H6L6ekEZYGWnkfR4wMiyeTVoCeVunt0fda7t9YCtJ70cm911yZ---:encrypted
>>>
>>> myfile:unencrypted
>>> myfile2:unencrypted
>>>
>>> Creating a file with file name encryption disabled and remounting with
>>> file name encryption enabled results in the following.
>>>
>>> $ ls -li
>>> ls: cannot access 'myfile3': No such file or directory
>>> total 48
>>> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
>>> 5252822 -rw-rw-r-- 1 groeck groeck 10 Jan 20 13:02 myfile
>>> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
>>> 5252824 -rw-rw-r-- 1 groeck groeck 10 Jan 20 15:36 myfile2
>>>        ? -????????? ? ?      ?       ?            ? myfile3
>>>
>>> Prior to commit 88ae4ab9802e, the file system had to be mounted with
>>> encrypted file names first to create a file, then the same had to be
>>> repeated after mounting with unencrypted file names. Now the duplicate
>>> files can be created both ways (unencrypted _or_ encrypted first).
>>>
>>> The only real difference is that it is no longer possible to have a
>>> _working_ combination of encrypted and unencrypted file names. In other
>>> words, commit 88ae4ab9802e results in reduced functionality with no
>>> benefit whatsoever.
>>>
>>> Restore ability to have a mix of unencrypted and encrypted files.
>>> This effectively reverts commit 88ae4ab9802e, but the code is now
>>> better readable since it avoids a number of goto statements.
>>
>> I'd like for us to correctly fix 88ae4ab9802e rather than try to support
>> both filename types under a single mount since that's complex and there
>> are unknown corner cases to consider. I think this can be done by not
>> copying up the lower filename when an error is encountered in
>> ecryptfs_decode_and_decrypt_filename(). If filename encryption is
>> enabled, it should only return decrypted filenames or an error if it
>> isn't possible to decrypt the lower filename.
>>
> 
> NP. I'll leave it alone, then. Since our use case requires both encrypted
> and unencrypted file names, our "fix" will be to carry this patch along
> locally as long as needed and stop using ecryptfs otherwise.

I think that's a good plan. While eCryptfs has been fairly stable for
quite some time, it is starved for maintenance attention these days as
you've noticed with this thread. :/

Thanks for bringing up this bug. I'll include you on any followup
patches to fix the 88ae4ab9802e change so that you'll be aware of any
additional local patches that you'll need to carry.

Tyler

> 
> Guenter
> 
>> Tyler
>>
>>>
>>> Cc: Al Viro <viro@zeniv.linux.org.uk>
>>> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>>> ---
>>>   fs/ecryptfs/inode.c | 10 +++++-----
>>>   1 file changed, 5 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
>>> index 847904aa63a9..14a5c096ead6 100644
>>> --- a/fs/ecryptfs/inode.c
>>> +++ b/fs/ecryptfs/inode.c
>>> @@ -392,11 +392,11 @@ static struct dentry *ecryptfs_lookup(struct
>>> inode *ecryptfs_dir_inode,
>>>       int rc = 0;
>>>         lower_dir_dentry =
>>> ecryptfs_dentry_to_lower(ecryptfs_dentry->d_parent);
>>> -
>>> +    lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry,
>>> len);
>>>       mount_crypt_stat = &ecryptfs_superblock_to_private(
>>>                   ecryptfs_dentry->d_sb)->mount_crypt_stat;
>>> -    if (mount_crypt_stat
>>> -        && (mount_crypt_stat->flags &
>>> ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
>>> +    if (IS_ERR(lower_dentry) &&
>>> +        (mount_crypt_stat->flags &
>>> ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
>>>           rc = ecryptfs_encrypt_and_encode_filename(
>>>               &encrypted_and_encoded_name, &len,
>>>               mount_crypt_stat, name, len);
>>> @@ -405,10 +405,10 @@ static struct dentry *ecryptfs_lookup(struct
>>> inode *ecryptfs_dir_inode,
>>>                      "filename; rc = [%d]\n", __func__, rc);
>>>               return ERR_PTR(rc);
>>>           }
>>> -        name = encrypted_and_encoded_name;
>>> +        lower_dentry = lookup_one_len_unlocked(
>>> +            encrypted_and_encoded_name, lower_dir_dentry, len);
>>>       }
>>>   -    lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry,
>>> len);
>>>       if (IS_ERR(lower_dentry)) {
>>>           ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_len() returned "
>>>                   "[%ld] on lower_dentry = [%s]\n", __func__,
>>>
>>
>>
> 



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[PATCH] eCryptfs: don't pass up plaintext names when using filename encryption

[Tyler Hicks]

Both ecryptfs_filldir() and ecryptfs_readlink_lower() use
ecryptfs_decode_and_decrypt_filename() to translate lower filenames to
upper filenames. The function correctly passes up lower filenames,
unchanged, when filename encryption isn't in use. However, it was also
passing up lower filenames when the filename wasn't encrypted or
when decryption failed. Since 88ae4ab9802e, eCryptfs refuses to lookup
lower plaintext names when filename encryption is enabled so this
resulted in a situation where userspace would see lower plaintext
filenames in calls to getdents(2) but then not be able to lookup those
filenames.

An example of this can be seen when enabling filename encryption on an
eCryptfs mount at the root directory of an Ext4 filesystem:

$ ls -1i /lower
12 ECRYPTFS_FNEK_ENCRYPTED.FWYZD8TcW.5FV-TKTEYOHsheiHX9a-w.NURCCYIMjI8pn5BDB9-h3fXwrE--
11 lost+found
$ ls -1i /upper
ls: cannot access '/upper/lost+found': No such file or directory
 ? lost+found
12 test

With this change, the lower lost+found dentry is ignored:

$ ls -1i /lower
12 ECRYPTFS_FNEK_ENCRYPTED.FWYZD8TcW.5FV-TKTEYOHsheiHX9a-w.NURCCYIMjI8pn5BDB9-h3fXwrE--
11 lost+found
$ ls -1i /upper
12 test

Additionally, some potentially noisy error/info messages in the related
code paths are turned into debug messages so that the logs can't be
easily filled.

Fixes: 88ae4ab9802e ("ecryptfs_lookup(): try either only encrypted or plaintext name")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
---
 fs/ecryptfs/crypto.c | 41 ++++++++++++++++++++++++++++-------------
 fs/ecryptfs/file.c   | 21 ++++++++++++++++-----
 2 files changed, 44 insertions(+), 18 deletions(-)

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index 846ca15..4dd842f 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -1997,6 +1997,16 @@ int ecryptfs_encrypt_and_encode_filename(
 	return rc;
 }
 
+static bool is_dot_dotdot(const char *name, size_t name_size)
+{
+	if (name_size == 1 && name[0] == '.')
+		return true;
+	else if (name_size == 2 && name[0] == '.' && name[1] == '.')
+		return true;
+
+	return false;
+}
+
 /**
  * ecryptfs_decode_and_decrypt_filename - converts the encoded cipher text name to decoded plaintext
  * @plaintext_name: The plaintext name
@@ -2021,13 +2031,21 @@ int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,
 	size_t packet_size;
 	int rc = 0;
 
-	if ((mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)
-	    && !(mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
-	    && (name_size > ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE)
-	    && (strncmp(name, ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
-			ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE) == 0)) {
-		const char *orig_name = name;
-		size_t orig_name_size = name_size;
+	if ((mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES) &&
+	    !(mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)) {
+		if (is_dot_dotdot(name, name_size)) {
+			rc = ecryptfs_copy_filename(plaintext_name,
+						    plaintext_name_size,
+						    name, name_size);
+			goto out;
+		}
+
+		if (name_size <= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE ||
+		    strncmp(name, ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
+			    ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE)) {
+			rc = -EINVAL;
+			goto out;
+		}
 
 		name += ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
 		name_size -= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
@@ -2047,12 +2065,9 @@ int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,
 						  decoded_name,
 						  decoded_name_size);
 		if (rc) {
-			printk(KERN_INFO "%s: Could not parse tag 70 packet "
-			       "from filename; copying through filename "
-			       "as-is\n", __func__);
-			rc = ecryptfs_copy_filename(plaintext_name,
-						    plaintext_name_size,
-						    orig_name, orig_name_size);
+			ecryptfs_printk(KERN_DEBUG,
+					"%s: Could not parse tag 70 packet from filename\n",
+					__func__);
 			goto out_free;
 		}
 	} else {
diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
index c74ed3c..b76a985 100644
--- a/fs/ecryptfs/file.c
+++ b/fs/ecryptfs/file.c
@@ -82,17 +82,28 @@ ecryptfs_filldir(struct dir_context *ctx, const char *lower_name,
 						  buf->sb, lower_name,
 						  lower_namelen);
 	if (rc) {
-		printk(KERN_ERR "%s: Error attempting to decode and decrypt "
-		       "filename [%s]; rc = [%d]\n", __func__, lower_name,
-		       rc);
-		goto out;
+		if (rc != -EINVAL) {
+			ecryptfs_printk(KERN_DEBUG,
+					"%s: Error attempting to decode and decrypt filename [%s]; rc = [%d]\n",
+					__func__, lower_name, rc);
+			return rc;
+		}
+
+		/* Mask -EINVAL errors as these are most likely due a plaintext
+		 * filename present in the lower filesystem despite filename
+		 * encryption being enabled. One unavoidable example would be
+		 * the "lost+found" dentry in the root directory of an Ext4
+		 * filesystem.
+		 */
+		return 0;
 	}
+
 	buf->caller->pos = buf->ctx.pos;
 	rc = !dir_emit(buf->caller, name, name_size, ino, d_type);
 	kfree(name);
 	if (!rc)
 		buf->entries_written++;
-out:
+
 	return rc;
 }
 
-- 
2.7.4