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-rw-r--r--fs/crypto/Makefile2
-rw-r--r--fs/crypto/hooks.c49
-rw-r--r--include/linux/fscrypt_notsupp.h9
-rw-r--r--include/linux/fscrypt_supp.h3
4 files changed, 62 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);
diff --git a/include/linux/fscrypt_notsupp.h b/include/linux/fscrypt_notsupp.h
index 7b390e356f7f..162da6517ac4 100644
--- a/include/linux/fscrypt_notsupp.h
+++ b/include/linux/fscrypt_notsupp.h
@@ -177,4 +177,13 @@ 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 */
diff --git a/include/linux/fscrypt_supp.h b/include/linux/fscrypt_supp.h
index 5a90e5ef4687..fd2f6decaee4 100644
--- a/include/linux/fscrypt_supp.h
+++ b/include/linux/fscrypt_supp.h
@@ -143,4 +143,7 @@ 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 */