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Commit b811faac authored by Eric Biggers's avatar Eric Biggers Committed by Jaegeuk Kim
Browse files

fscrypt: new helper function - fscrypt_file_open() 



Add a helper function which prepares to open a regular file which may be
encrypted.  It handles setting up the file's encryption key, then
checking that the file's encryption policy matches that of its parent
directory (if the parent directory is encrypted).  It may be set as the
->open() method or it can be called from another ->open() method.

Acked-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent e9f57e37

fs/crypto/Makefile

+1 −1
Original line number Diff line number Diff line 
obj-$(CONFIG_FS_ENCRYPTION)	+= fscrypto.o



fscrypto-y := crypto.o fname.o policy.o keyinfo.o

fscrypto-y := crypto.o fname.o hooks.o keyinfo.o policy.o

fscrypto-$(CONFIG_BLOCK) += bio.o

fs/crypto/hooks.c

0 → 100644
+49 −0
Original line number Diff line number Diff line 
/*

 * fs/crypto/hooks.c

 *

 * Encryption hooks for higher-level filesystem operations.

 */



#include <linux/ratelimit.h>

#include "fscrypt_private.h"



/**

 * fscrypt_file_open - prepare to open a possibly-encrypted regular file

 * @inode: the inode being opened

 * @filp: the struct file being set up

 *

 * Currently, an encrypted regular file can only be opened if its encryption key

 * is available; access to the raw encrypted contents is not supported.

 * Therefore, we first set up the inode's encryption key (if not already done)

 * and return an error if it's unavailable.

 *

 * We also verify that if the parent directory (from the path via which the file

 * is being opened) is encrypted, then the inode being opened uses the same

 * encryption policy.  This is needed as part of the enforcement that all files

 * in an encrypted directory tree use the same encryption policy, as a

 * protection against certain types of offline attacks.  Note that this check is

 * needed even when opening an *unencrypted* file, since it's forbidden to have

 * an unencrypted file in an encrypted directory.

 *

 * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code

 */

int fscrypt_file_open(struct inode *inode, struct file *filp)

{

	int err;

	struct dentry *dir;



	err = fscrypt_require_key(inode);

	if (err)

		return err;



	dir = dget_parent(file_dentry(filp));

	if (IS_ENCRYPTED(d_inode(dir)) &&

	    !fscrypt_has_permitted_context(d_inode(dir), inode)) {

		pr_warn_ratelimited("fscrypt: inconsistent encryption contexts: %lu/%lu",

				    d_inode(dir)->i_ino, inode->i_ino);

		err = -EPERM;

	}

	dput(dir);

	return err;

}

EXPORT_SYMBOL_GPL(fscrypt_file_open);

include/linux/fscrypt_notsupp.h

+9 −0
Original line number Diff line number Diff line
@@ -178,4 +178,13 @@ static inline int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk, 
	return -EOPNOTSUPP;

}



/* hooks.c */



static inline int fscrypt_file_open(struct inode *inode, struct file *filp)

{

	if (IS_ENCRYPTED(inode))

		return -EOPNOTSUPP;

	return 0;

}



#endif	/* _LINUX_FSCRYPT_NOTSUPP_H */

include/linux/fscrypt_supp.h

+3 −0
Original line number Diff line number Diff line
@@ -144,4 +144,7 @@ extern void fscrypt_pullback_bio_page(struct page **, bool); 
extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,

				 unsigned int);



/* hooks.c */

extern int fscrypt_file_open(struct inode *inode, struct file *filp);



#endif	/* _LINUX_FSCRYPT_SUPP_H */