ubifs: Add skeleton for fscrypto

This is the first building block to provide file level
encryption on UBIFS.

Signed-off-by: Richard Weinberger <richard@nod.at>

9 files changed, 178 insertions, 2 deletions

diff --git a/fs/ubifs/Kconfig b/fs/ubifs/Kconfig
index 7ff7712f284e..0a908ae7af13 100644
--- a/fs/ubifs/Kconfig
+++ b/fs/ubifs/Kconfig
@@ -50,3 +50,14 @@ config UBIFS_ATIME_SUPPORT
           strictatime is the "heavy", relatime is "lighter", etc.
 
           If unsure, say 'N'
+
+config UBIFS_FS_ENCRYPTION
+        bool "UBIFS Encryption"
+        depends on UBIFS_FS
+        select FS_ENCRYPTION
+        default n
+        help
+          Enable encryption of UBIFS files and directories. This
+          feature is similar to ecryptfs, but it is more memory
+          efficient since it avoids caching the encrypted and
+          decrypted pages in the page cache.
diff --git a/fs/ubifs/Makefile b/fs/ubifs/Makefile
index c54a24360f85..6f3251c2bf08 100644
--- a/fs/ubifs/Makefile
+++ b/fs/ubifs/Makefile
@@ -5,3 +5,4 @@ ubifs-y += tnc.o master.o scan.o replay.o log.o commit.o gc.o orphan.o
 ubifs-y += budget.o find.o tnc_commit.o compress.o lpt.o lprops.o
 ubifs-y += recovery.o ioctl.o lpt_commit.o tnc_misc.o xattr.o debug.o
 ubifs-y += misc.o
+ubifs-$(CONFIG_UBIFS_FS_ENCRYPTION) += crypto.o
diff --git a/fs/ubifs/crypto.c b/fs/ubifs/crypto.c
new file mode 100644
index 000000000000..12a0072bddd3
--- /dev/null
+++ b/fs/ubifs/crypto.c
@@ -0,0 +1,46 @@
+#include "ubifs.h"
+
+static int ubifs_crypt_get_context(struct inode *inode, void *ctx, size_t len)
+{
+        return ubifs_xattr_get(inode, UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT,
+                               ctx, len);
+}
+
+static int ubifs_crypt_set_context(struct inode *inode, const void *ctx,
+                                   size_t len, void *fs_data)
+{
+        return ubifs_xattr_set(inode, UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT,
+                               ctx, len, 0);
+}
+
+static bool ubifs_crypt_empty_dir(struct inode *inode)
+{
+        return ubifs_check_dir_empty(inode) == 0;
+}
+
+static unsigned int ubifs_crypt_max_namelen(struct inode *inode)
+{
+        if (S_ISLNK(inode->i_mode))
+                return UBIFS_MAX_INO_DATA;
+        else
+                return UBIFS_MAX_NLEN;
+}
+
+static int ubifs_key_prefix(struct inode *inode, u8 **key)
+{
+        static char prefix[] = "ubifs:";
+
+        *key = prefix;
+
+        return sizeof(prefix) - 1;
+}
+
+struct fscrypt_operations ubifs_crypt_operations = {
+        .flags                  = FS_CFLG_INPLACE_ENCRYPTION,
+        .get_context            = ubifs_crypt_get_context,
+        .set_context            = ubifs_crypt_set_context,
+        .is_encrypted           = ubifs_crypt_is_encrypted,
+        .empty_dir              = ubifs_crypt_empty_dir,
+        .max_namelen            = ubifs_crypt_max_namelen,
+        .key_prefix             = ubifs_key_prefix,
+};
diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 14a226d47f4c..2315cb864c39 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -85,11 +85,26 @@ static int inherit_flags(const struct inode *dir, umode_t mode)
  * initializes it. Returns new inode in case of success and an error code in
  * case of failure.
  */
-struct inode *ubifs_new_inode(struct ubifs_info *c, const struct inode *dir,
+struct inode *ubifs_new_inode(struct ubifs_info *c, struct inode *dir,
                               umode_t mode)
 {
+        int err;
         struct inode *inode;
         struct ubifs_inode *ui;
+        bool encrypted = false;
+
+        if (ubifs_crypt_is_encrypted(dir)) {
+                err = fscrypt_get_encryption_info(dir);
+                if (err) {
+                        ubifs_err(c, "fscrypt_get_encryption_info failed: %i", err);
+                        return ERR_PTR(err);
+                }
+
+                if (!fscrypt_has_encryption_key(dir))
+                        return ERR_PTR(-EPERM);
+
+                encrypted = true;
+        }
 
         inode = new_inode(c->vfs_sb);
         ui = ubifs_inode(inode);
@@ -165,6 +180,17 @@ struct inode *ubifs_new_inode(struct ubifs_info *c, const struct inode *dir,
          */
         ui->creat_sqnum = ++c->max_sqnum;
         spin_unlock(&c->cnt_lock);
+
+        if (encrypted) {
+                err = fscrypt_inherit_context(dir, inode, &encrypted, true);
+                if (err) {
+                        ubifs_err(c, "fscrypt_inherit_context failed: %i", err);
+                        make_bad_inode(inode);
+                        iput(inode);
+                        return ERR_PTR(err);
+                }
+        }
+
         return inode;
 }
 
diff --git a/fs/ubifs/ioctl.c b/fs/ubifs/ioctl.c
index 3c7b29de0ca7..6bb5b35050de 100644
--- a/fs/ubifs/ioctl.c
+++ b/fs/ubifs/ioctl.c
@@ -181,6 +181,41 @@ long ubifs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
                 mnt_drop_write_file(file);
                 return err;
         }
+        case FS_IOC_SET_ENCRYPTION_POLICY: {
+#ifdef CONFIG_UBIFS_FS_ENCRYPTION
+                struct fscrypt_policy policy;
+
+                if (copy_from_user(&policy,
+                                   (struct fscrypt_policy __user *)arg,
+                                   sizeof(policy)))
+                        return -EFAULT;
+
+                err = fscrypt_process_policy(file, &policy);
+
+                return err;
+#else
+                return -EOPNOTSUPP;
+#endif
+        }
+        case FS_IOC_GET_ENCRYPTION_POLICY: {
+#ifdef CONFIG_UBIFS_FS_ENCRYPTION
+                struct fscrypt_policy policy;
+
+                if (!ubifs_crypt_is_encrypted(inode))
+                        return -ENOENT;
+
+                err = fscrypt_get_policy(inode, &policy);
+                if (err)
+                        return err;
+
+                if (copy_to_user((void __user *)arg, &policy, sizeof(policy)))
+                        return -EFAULT;
+
+                return 0;
+#else
+                return -EOPNOTSUPP;
+#endif
+        }
 
         default:
                 return -ENOTTY;
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 4ec051089186..e85d5a47aeac 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -380,6 +380,9 @@ out:
         }
 done:
         clear_inode(inode);
+#ifdef CONFIG_UBIFS_FS_ENCRYPTION
+        fscrypt_put_encryption_info(inode, NULL);
+#endif
 }
 
 static void ubifs_dirty_inode(struct inode *inode, int flags)
@@ -1995,6 +1998,12 @@ static struct ubifs_info *alloc_ubifs_info(struct ubi_volume_desc *ubi)
         return c;
 }
 
+#ifndef CONFIG_UBIFS_FS_ENCRYPTION
+struct fscrypt_operations ubifs_crypt_operations = {
+        .is_encrypted           = ubifs_crypt_is_encrypted,
+};
+#endif
+
 static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
 {
         struct ubifs_info *c = sb->s_fs_info;
@@ -2041,6 +2050,7 @@ static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
                 sb->s_maxbytes = c->max_inode_sz = MAX_LFS_FILESIZE;
         sb->s_op = &ubifs_super_operations;
         sb->s_xattr = ubifs_xattr_handlers;
+        sb->s_cop = &ubifs_crypt_operations;
 
         mutex_lock(&c->umount_mutex);
         err = mount_ubifs(c);
diff --git a/fs/ubifs/ubifs-media.h b/fs/ubifs/ubifs-media.h
index d47e9569b3de..aa302b11aec8 100644
--- a/fs/ubifs/ubifs-media.h
+++ b/fs/ubifs/ubifs-media.h
@@ -316,6 +316,7 @@ enum {
  * UBIFS_APPEND_FL: writes to the inode may only append data
  * UBIFS_DIRSYNC_FL: I/O on this directory inode has to be synchronous
  * UBIFS_XATTR_FL: this inode is the inode for an extended attribute value
+ * UBIFS_CRYPT_FL: use encryption for this inode
  *
  * Note, these are on-flash flags which correspond to ioctl flags
  * (@FS_COMPR_FL, etc). They have the same values now, but generally, do not
@@ -328,6 +329,7 @@ enum {
         UBIFS_APPEND_FL    = 0x08,
         UBIFS_DIRSYNC_FL   = 0x10,
         UBIFS_XATTR_FL     = 0x20,
+        UBIFS_CRYPT_FL     = 0x40,
 };
 
 /* Inode flag bits used by UBIFS */
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 0f8a3ec6a7fe..27a85015e3ff 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -38,6 +38,7 @@
 #include <linux/backing-dev.h>
 #include <linux/security.h>
 #include <linux/xattr.h>
+#include <linux/fscrypto.h>
 #include "ubifs-media.h"
 
 /* Version of this UBIFS implementation */
@@ -1724,7 +1725,7 @@ int ubifs_update_time(struct inode *inode, struct timespec *time, int flags);
 #endif
 
 /* dir.c */
-struct inode *ubifs_new_inode(struct ubifs_info *c, const struct inode *dir,
+struct inode *ubifs_new_inode(struct ubifs_info *c, struct inode *dir,
                               umode_t mode);
 int ubifs_getattr(struct vfsmount *mnt, struct dentry *dentry,
                   struct kstat *stat);
@@ -1773,10 +1774,44 @@ void ubifs_compress(const struct ubifs_info *c, const void *in_buf, int in_len,
 int ubifs_decompress(const struct ubifs_info *c, const void *buf, int len,
                      void *out, int *out_len, int compr_type);
 
+extern struct fscrypt_operations ubifs_crypt_operations;
+
 #include "debug.h"
 #include "misc.h"
 #include "key.h"
 
+#ifndef CONFIG_UBIFS_FS_ENCRYPTION
+#define fscrypt_set_d_op(i)
+#define fscrypt_get_ctx                 fscrypt_notsupp_get_ctx
+#define fscrypt_release_ctx             fscrypt_notsupp_release_ctx
+#define fscrypt_encrypt_page            fscrypt_notsupp_encrypt_page
+#define fscrypt_decrypt_page            fscrypt_notsupp_decrypt_page
+#define fscrypt_decrypt_bio_pages       fscrypt_notsupp_decrypt_bio_pages
+#define fscrypt_pullback_bio_page       fscrypt_notsupp_pullback_bio_page
+#define fscrypt_restore_control_page    fscrypt_notsupp_restore_control_page
+#define fscrypt_zeroout_range           fscrypt_notsupp_zeroout_range
+#define fscrypt_process_policy          fscrypt_notsupp_process_policy
+#define fscrypt_get_policy              fscrypt_notsupp_get_policy
+#define fscrypt_has_permitted_context   fscrypt_notsupp_has_permitted_context
+#define fscrypt_inherit_context         fscrypt_notsupp_inherit_context
+#define fscrypt_get_encryption_info     fscrypt_notsupp_get_encryption_info
+#define fscrypt_put_encryption_info     fscrypt_notsupp_put_encryption_info
+#define fscrypt_setup_filename          fscrypt_notsupp_setup_filename
+#define fscrypt_free_filename           fscrypt_notsupp_free_filename
+#define fscrypt_fname_encrypted_size    fscrypt_notsupp_fname_encrypted_size
+#define fscrypt_fname_alloc_buffer      fscrypt_notsupp_fname_alloc_buffer
+#define fscrypt_fname_free_buffer       fscrypt_notsupp_fname_free_buffer
+#define fscrypt_fname_disk_to_usr       fscrypt_notsupp_fname_disk_to_usr
+#define fscrypt_fname_usr_to_disk       fscrypt_notsupp_fname_usr_to_disk
+#endif
+
+static inline bool ubifs_crypt_is_encrypted(struct inode *inode)
+{
+        struct ubifs_inode *ui = ubifs_inode(inode);
+
+        return ui->flags & UBIFS_CRYPT_FL;
+}
+
 /* Normal UBIFS messages */
 __printf(2, 3)
 void ubifs_msg(const struct ubifs_info *c, const char *fmt, ...);
diff --git a/fs/ubifs/xattr.c b/fs/ubifs/xattr.c
index 2d09dbeecd58..95a16028bbdb 100644
--- a/fs/ubifs/xattr.c
+++ b/fs/ubifs/xattr.c
@@ -158,6 +158,15 @@ static int create_xattr(struct ubifs_info *c, struct inode *host,
         host_ui->xattr_size += CALC_XATTR_BYTES(size);
         host_ui->xattr_names += nm->len;
 
+        /*
+         * We handle UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT here because we
+         * have to set the UBIFS_CRYPT_FL flag on the host inode.
+         * To avoid multiple updates of the same inode in the same operation,
+         * let's do it here.
+         */
+        if (strcmp(nm->name, UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT) == 0)
+                host_ui->flags |= UBIFS_CRYPT_FL;
+
         err = ubifs_jnl_update(c, host, nm, inode, 0, 1);
         if (err)
                 goto out_cancel;
@@ -173,6 +182,7 @@ out_cancel:
         host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
         host_ui->xattr_size -= CALC_XATTR_BYTES(size);
         host_ui->xattr_names -= nm->len;
+        host_ui->flags &= ~UBIFS_CRYPT_FL;
         mutex_unlock(&host_ui->ui_mutex);
 out_free:
         make_bad_inode(inode);