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authorEric Biggers <ebiggers@google.com>2017-10-09 12:15:40 -0700
committerTheodore Ts'o <tytso@mit.edu>2017-10-18 19:52:37 -0400
commitefcc7ae2c9172d9a7ae94afdaf066a7abf0b9a90 (patch)
treefbaef3000dea4cc606671055f08f2272c5025d77 /fs/crypto
parentd293c3e4e07334d761c88df9d68b3aa800a83dd9 (diff)
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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: Dave Chinner <dchinner@redhat.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/crypto')
-rw-r--r--fs/crypto/Makefile2
-rw-r--r--fs/crypto/hooks.c49
2 files changed, 50 insertions, 1 deletions
diff --git a/fs/crypto/Makefile b/fs/crypto/Makefile
index 9f6607f17b53..cb496989a6b6 100644
--- a/fs/crypto/Makefile
+++ b/fs/crypto/Makefile
@@ -1,4 +1,4 @@
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
diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
new file mode 100644
index 000000000000..069088e91ea9
--- /dev/null
+++ b/fs/crypto/hooks.c
@@ -0,0 +1,49 @@
+/*
+ * 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);