linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: don't allow rename unencrypted file to encrypted directory

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Date:   Thu, 9 Mar 2017 09:33:03 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Kinglong Mee <kinglongmee@...il.com>, <jaegeuk@...nel.org>
CC:     <chao@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH] f2fs: don't allow rename unencrypted file to
 encrypted directory

On 2017/3/8 21:35, Kinglong Mee wrote:
> On 3/8/2017 20:08, Chao Yu wrote:
>> In commit d9cdc9033181 ("ext4 crypto: enforce context consistency") we
>> declared that:
>>
>> 2) All files or directories in a directory must be protected using the
>>     same key as their containing directory.
>>
>> But in f2fs_cross_rename there is a vulnerability that allow to cross
>> rename unencrypted file into encrypted directory, it needs to be refused.
> 
> fscrypt_has_permitted_context has do the checking as this patch,
> 
> 168         /* no restrictions if the parent directory is not encrypted */
> 169         if (!parent->i_sb->s_cop->is_encrypted(parent))
> 170                 return 1;
> 171         /* if the child directory is not encrypted, this is always a problem */
> 172         if (!parent->i_sb->s_cop->is_encrypted(child))
> 173                 return 0;
> 
> So, the cross rename unencrypted file into encrypted directory is permitted right now. 
> 
> I have a encrypted directory "ncry",  "new" is unencrypted file.
> 
> [root@...testnic f2fs]# renameat2 -x encry/hello new
> Operation not permitted
> [root@...testnic f2fs]# renameat2 -x encry/hello new
> Operation not permitted

I've tried this, the same result as yours, so this patch is wrong, please ignore
it, sorry about the noise.

Thanks,

> 
> How do you test it? 
> 
> thanks,
> Kinglong Mee
>>
>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>> ---
>>  fs/f2fs/namei.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
>> index 25c073f6c7d4..8de684b84cb9 100644
>> --- a/fs/f2fs/namei.c
>> +++ b/fs/f2fs/namei.c
>> @@ -855,6 +855,10 @@ static int f2fs_cross_rename(struct inode *old_dir, struct dentry *old_dentry,
>>  			!fscrypt_has_encryption_key(new_dir)))
>>  		return -ENOKEY;
>>  
>> +	if (f2fs_encrypted_inode(old_dir) && !f2fs_encrypted_inode(new_inode) ||
>> +		f2fs_encrypted_inode(new_dir) && !f2fs_encrypted_inode(old_inode))
>> +		return -EPERM;
>> +
>>  	if ((f2fs_encrypted_inode(old_dir) || f2fs_encrypted_inode(new_dir)) &&
>>  			(old_dir != new_dir) &&
>>  			(!fscrypt_has_permitted_context(new_dir, old_inode) ||
>>
> 
> .
>