ubifs: Add authentication nodes to journal

Nodes that are written to flash can only be authenticated through the
index after the next commit. When a journal replay is necessary the
nodes are not yet referenced by the index and thus can't be
authenticated.

This patch overcomes this situation by creating a hash over all nodes
beginning from the commit start node over the reference node(s) and
the buds themselves. From
time to time we insert authentication nodes. Authentication nodes
contain a HMAC from the current hash state, so that they can be
used to authenticate a journal replay up to the point where the
authentication node is. The hash is continued afterwards
so that theoretically we would only have to check the HMAC of
the last authentication node we find.

Overall we get this picture:

,,,,,,,,
,......,...........................................
,. CS  ,               hash1.----.           hash2.----.
,.  |  ,                    .    |hmac            .    |hmac
,.  v  ,                    .    v                .    v
,.REF#0,-> bud -> bud -> bud.-> auth -> bud -> bud.-> auth ...
,..|...,...........................................
,  |   ,
,  |   ,,,,,,,,,,,,,,,
.  |            hash3,----.
,  |                 ,    |hmac
,  v                 ,    v
, REF#1 -> bud -> bud,-> auth ...
,,,|,,,,,,,,,,,,,,,,,,
   v
  REF#2 -> ...
   |
   V
  ...

Note how hash3 covers CS, REF#0 and REF#1 so that it is not possible to
exchange or skip any reference nodes. Unlike the picture suggests the
auth nodes themselves are not hashed.

With this it is possible for an offline attacker to cut each journal
head or to drop the last reference node(s), but not to skip any journal
heads or to reorder any operations.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 107 insertions, 17 deletions

diff --git a/fs/ubifs/journal.c b/fs/ubifs/journal.c
index 7c12bdfa9a7a..729dc76c83df 100644
--- a/fs/ubifs/journal.c
+++ b/fs/ubifs/journal.c
@@ -90,6 +90,12 @@ static inline void zero_trun_node_unused(struct ubifs_trun_node *trun)
         memset(trun->padding, 0, 12);
 }
 
+static void ubifs_add_auth_dirt(struct ubifs_info *c, int lnum)
+{
+        if (ubifs_authenticated(c))
+                ubifs_add_dirt(c, lnum, ubifs_auth_node_sz(c));
+}
+
 /**
  * reserve_space - reserve space in the journal.
  * @c: UBIFS file-system description object
@@ -228,6 +234,35 @@ out_return:
         return err;
 }
 
+static int ubifs_hash_nodes(struct ubifs_info *c, void *node,
+                             int len, struct shash_desc *hash)
+{
+        int auth_node_size = ubifs_auth_node_sz(c);
+        int err;
+
+        while (1) {
+                const struct ubifs_ch *ch = node;
+                int nodelen = le32_to_cpu(ch->len);
+
+                ubifs_assert(c, len >= auth_node_size);
+
+                if (len == auth_node_size)
+                        break;
+
+                ubifs_assert(c, len > nodelen);
+                ubifs_assert(c, ch->magic == cpu_to_le32(UBIFS_NODE_MAGIC));
+
+                err = ubifs_shash_update(c, hash, (void *)node, nodelen);
+                if (err)
+                        return err;
+
+                node += ALIGN(nodelen, 8);
+                len -= ALIGN(nodelen, 8);
+        }
+
+        return ubifs_prepare_auth_node(c, node, hash);
+}
+
 /**
  * write_head - write data to a journal head.
  * @c: UBIFS file-system description object
@@ -255,6 +290,12 @@ static int write_head(struct ubifs_info *c, int jhead, void *buf, int len,
         dbg_jnl("jhead %s, LEB %d:%d, len %d",
                 dbg_jhead(jhead), *lnum, *offs, len);
 
+        if (ubifs_authenticated(c)) {
+                err = ubifs_hash_nodes(c, buf, len, c->jheads[jhead].log_hash);
+                if (err)
+                        return err;
+        }
+
         err = ubifs_wbuf_write_nolock(wbuf, buf, len);
         if (err)
                 return err;
@@ -543,7 +584,10 @@ int ubifs_jnl_update(struct ubifs_info *c, const struct inode *dir,
 
         len = aligned_dlen + aligned_ilen + UBIFS_INO_NODE_SZ;
         /* Make sure to also account for extended attributes */
-        len += host_ui->data_len;
+        if (ubifs_authenticated(c))
+                len += ALIGN(host_ui->data_len, 8) + ubifs_auth_node_sz(c);
+        else
+                len += host_ui->data_len;
 
         dent = kzalloc(len, GFP_NOFS);
         if (!dent)
@@ -611,6 +655,7 @@ int ubifs_jnl_update(struct ubifs_info *c, const struct inode *dir,
         }
         release_head(c, BASEHD);
         kfree(dent);
+        ubifs_add_auth_dirt(c, lnum);
 
         if (deletion) {
                 if (nm->hash)
@@ -690,8 +735,9 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode,
                          const union ubifs_key *key, const void *buf, int len)
 {
         struct ubifs_data_node *data;
-        int err, lnum, offs, compr_type, out_len, compr_len;
+        int err, lnum, offs, compr_type, out_len, compr_len, auth_len;
         int dlen = COMPRESSED_DATA_NODE_BUF_SZ, allocated = 1;
+        int write_len;
         struct ubifs_inode *ui = ubifs_inode(inode);
         bool encrypted = ubifs_crypt_is_encrypted(inode);
         u8 hash[UBIFS_HASH_ARR_SZ];
@@ -703,7 +749,9 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode,
         if (encrypted)
                 dlen += UBIFS_CIPHER_BLOCK_SIZE;
 
-        data = kmalloc(dlen, GFP_NOFS | __GFP_NOWARN);
+        auth_len = ubifs_auth_node_sz(c);
+
+        data = kmalloc(dlen + auth_len, GFP_NOFS | __GFP_NOWARN);
         if (!data) {
                 /*
                  * Fall-back to the write reserve buffer. Note, we might be
@@ -742,15 +790,20 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode,
         }
 
         dlen = UBIFS_DATA_NODE_SZ + out_len;
+        if (ubifs_authenticated(c))
+                write_len = ALIGN(dlen, 8) + auth_len;
+        else
+                write_len = dlen;
+
         data->compr_type = cpu_to_le16(compr_type);
 
         /* Make reservation before allocating sequence numbers */
-        err = make_reservation(c, DATAHD, dlen);
+        err = make_reservation(c, DATAHD, write_len);
         if (err)
                 goto out_free;
 
         ubifs_prepare_node(c, data, dlen, 0);
-        err = write_head(c, DATAHD, data, dlen, &lnum, &offs, 0);
+        err = write_head(c, DATAHD, data, write_len, &lnum, &offs, 0);
         if (err)
                 goto out_release;
 
@@ -761,6 +814,8 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode,
         ubifs_wbuf_add_ino_nolock(&c->jheads[DATAHD].wbuf, key_inum(c, key));
         release_head(c, DATAHD);
 
+        ubifs_add_auth_dirt(c, lnum);
+
         err = ubifs_tnc_add(c, key, lnum, offs, dlen, hash);
         if (err)
                 goto out_ro;
@@ -799,7 +854,8 @@ int ubifs_jnl_write_inode(struct ubifs_info *c, const struct inode *inode)
         int err, lnum, offs;
         struct ubifs_ino_node *ino;
         struct ubifs_inode *ui = ubifs_inode(inode);
-        int sync = 0, len = UBIFS_INO_NODE_SZ, last_reference = !inode->i_nlink;
+        int sync = 0, write_len, ilen = UBIFS_INO_NODE_SZ;
+        int last_reference = !inode->i_nlink;
         u8 hash[UBIFS_HASH_ARR_SZ];
 
         dbg_jnl("ino %lu, nlink %u", inode->i_ino, inode->i_nlink);
@@ -809,15 +865,21 @@ int ubifs_jnl_write_inode(struct ubifs_info *c, const struct inode *inode)
          * need to synchronize the write-buffer either.
          */
         if (!last_reference) {
-                len += ui->data_len;
+                ilen += ui->data_len;
                 sync = IS_SYNC(inode);
         }
-        ino = kmalloc(len, GFP_NOFS);
+
+        if (ubifs_authenticated(c))
+                write_len = ALIGN(ilen, 8) + ubifs_auth_node_sz(c);
+        else
+                write_len = ilen;
+
+        ino = kmalloc(write_len, GFP_NOFS);
         if (!ino)
                 return -ENOMEM;
 
         /* Make reservation before allocating sequence numbers */
-        err = make_reservation(c, BASEHD, len);
+        err = make_reservation(c, BASEHD, write_len);
         if (err)
                 goto out_free;
 
@@ -826,7 +888,7 @@ int ubifs_jnl_write_inode(struct ubifs_info *c, const struct inode *inode)
         if (err)
                 goto out_release;
 
-        err = write_head(c, BASEHD, ino, len, &lnum, &offs, sync);
+        err = write_head(c, BASEHD, ino, write_len, &lnum, &offs, sync);
         if (err)
                 goto out_release;
         if (!sync)
@@ -834,17 +896,19 @@ int ubifs_jnl_write_inode(struct ubifs_info *c, const struct inode *inode)
                                           inode->i_ino);
         release_head(c, BASEHD);
 
+        ubifs_add_auth_dirt(c, lnum);
+
         if (last_reference) {
                 err = ubifs_tnc_remove_ino(c, inode->i_ino);
                 if (err)
                         goto out_ro;
                 ubifs_delete_orphan(c, inode->i_ino);
-                err = ubifs_add_dirt(c, lnum, len);
+                err = ubifs_add_dirt(c, lnum, ilen);
         } else {
                 union ubifs_key key;
 
                 ino_key_init(c, &key, inode->i_ino);
-                err = ubifs_tnc_add(c, &key, lnum, offs, len, hash);
+                err = ubifs_tnc_add(c, &key, lnum, offs, ilen, hash);
         }
         if (err)
                 goto out_ro;
@@ -973,6 +1037,8 @@ int ubifs_jnl_xrename(struct ubifs_info *c, const struct inode *fst_dir,
         if (twoparents)
                 len += plen;
 
+        len += ubifs_auth_node_sz(c);
+
         dent1 = kzalloc(len, GFP_NOFS);
         if (!dent1)
                 return -ENOMEM;
@@ -1042,6 +1108,8 @@ int ubifs_jnl_xrename(struct ubifs_info *c, const struct inode *fst_dir,
         }
         release_head(c, BASEHD);
 
+        ubifs_add_auth_dirt(c, lnum);
+
         dent_key_init(c, &key, snd_dir->i_ino, snd_nm);
         err = ubifs_tnc_add_nm(c, &key, lnum, offs, dlen1, hash_dent1, snd_nm);
         if (err)
@@ -1143,6 +1211,9 @@ int ubifs_jnl_rename(struct ubifs_info *c, const struct inode *old_dir,
         len = aligned_dlen1 + aligned_dlen2 + ALIGN(ilen, 8) + ALIGN(plen, 8);
         if (move)
                 len += plen;
+
+        len += ubifs_auth_node_sz(c);
+
         dent = kzalloc(len, GFP_NOFS);
         if (!dent)
                 return -ENOMEM;
@@ -1240,6 +1311,8 @@ int ubifs_jnl_rename(struct ubifs_info *c, const struct inode *old_dir,
         }
         release_head(c, BASEHD);
 
+        ubifs_add_auth_dirt(c, lnum);
+
         dent_key_init(c, &key, new_dir->i_ino, new_nm);
         err = ubifs_tnc_add_nm(c, &key, lnum, offs, dlen1, hash_dent1, new_nm);
         if (err)
@@ -1411,6 +1484,9 @@ int ubifs_jnl_truncate(struct ubifs_info *c, const struct inode *inode,
 
         sz = UBIFS_TRUN_NODE_SZ + UBIFS_INO_NODE_SZ +
              UBIFS_MAX_DATA_NODE_SZ * WORST_COMPR_FACTOR;
+
+        sz += ubifs_auth_node_sz(c);
+
         ino = kmalloc(sz, GFP_NOFS);
         if (!ino)
                 return -ENOMEM;
@@ -1456,8 +1532,12 @@ int ubifs_jnl_truncate(struct ubifs_info *c, const struct inode *inode,
 
         /* Must make reservation before allocating sequence numbers */
         len = UBIFS_TRUN_NODE_SZ + UBIFS_INO_NODE_SZ;
-        if (dlen)
+
+        if (ubifs_authenticated(c))
+                len += ALIGN(dlen, 8) + ubifs_auth_node_sz(c);
+        else
                 len += dlen;
+
         err = make_reservation(c, BASEHD, len);
         if (err)
                 goto out_free;
@@ -1482,6 +1562,8 @@ int ubifs_jnl_truncate(struct ubifs_info *c, const struct inode *inode,
                 ubifs_wbuf_add_ino_nolock(&c->jheads[BASEHD].wbuf, inum);
         release_head(c, BASEHD);
 
+        ubifs_add_auth_dirt(c, lnum);
+
         if (dlen) {
                 sz = offs + UBIFS_INO_NODE_SZ + UBIFS_TRUN_NODE_SZ;
                 err = ubifs_tnc_add(c, &key, lnum, sz, dlen, hash_dn);
@@ -1545,7 +1627,7 @@ int ubifs_jnl_delete_xattr(struct ubifs_info *c, const struct inode *host,
                            const struct inode *inode,
                            const struct fscrypt_name *nm)
 {
-        int err, xlen, hlen, len, lnum, xent_offs, aligned_xlen;
+        int err, xlen, hlen, len, lnum, xent_offs, aligned_xlen, write_len;
         struct ubifs_dent_node *xent;
         struct ubifs_ino_node *ino;
         union ubifs_key xent_key, key1, key2;
@@ -1565,12 +1647,14 @@ int ubifs_jnl_delete_xattr(struct ubifs_info *c, const struct inode *host,
         hlen = host_ui->data_len + UBIFS_INO_NODE_SZ;
         len = aligned_xlen + UBIFS_INO_NODE_SZ + ALIGN(hlen, 8);
 
-        xent = kzalloc(len, GFP_NOFS);
+        write_len = len + ubifs_auth_node_sz(c);
+
+        xent = kzalloc(write_len, GFP_NOFS);
         if (!xent)
                 return -ENOMEM;
 
         /* Make reservation before allocating sequence numbers */
-        err = make_reservation(c, BASEHD, len);
+        err = make_reservation(c, BASEHD, write_len);
         if (err) {
                 kfree(xent);
                 return err;
@@ -1595,10 +1679,12 @@ int ubifs_jnl_delete_xattr(struct ubifs_info *c, const struct inode *host,
         if (err)
                 goto out_release;
 
-        err = write_head(c, BASEHD, xent, len, &lnum, &xent_offs, sync);
+        err = write_head(c, BASEHD, xent, write_len, &lnum, &xent_offs, sync);
         if (!sync && !err)
                 ubifs_wbuf_add_ino_nolock(&c->jheads[BASEHD].wbuf, host->i_ino);
         release_head(c, BASEHD);
+
+        ubifs_add_auth_dirt(c, lnum);
         kfree(xent);
         if (err)
                 goto out_ro;
@@ -1680,6 +1766,8 @@ int ubifs_jnl_change_xattr(struct ubifs_info *c, const struct inode *inode,
         aligned_len1 = ALIGN(len1, 8);
         aligned_len = aligned_len1 + ALIGN(len2, 8);
 
+        aligned_len += ubifs_auth_node_sz(c);
+
         ino = kzalloc(aligned_len, GFP_NOFS);
         if (!ino)
                 return -ENOMEM;
@@ -1709,6 +1797,8 @@ int ubifs_jnl_change_xattr(struct ubifs_info *c, const struct inode *inode,
         if (err)
                 goto out_ro;
 
+        ubifs_add_auth_dirt(c, lnum);
+
         ino_key_init(c, &key, host->i_ino);
         err = ubifs_tnc_add(c, &key, lnum, offs, len1, hash_host);
         if (err)