Don't store padding in db

Trim padding when storing and repad on the fly when retrieving.

src/handlers.rs

@@ -557,10 +557,19 @@ pub fn insert_message(
     if recent_posts >= RATE_LIMIT_POSTS {
         return Err(warp::reject::custom(Error::RateLimited));
     }
+
+    // Don't store useless padding; we'll repad (since it's needed for signature verification) when
+    // we retrieve.
+    let size = data.len();
+    let trimmed = match data.iter().rposition(|&c| c != 0u8) {
+        Some(last) => &data[0..last+1],
+        None => &data
+    };
+
     // Insert the message
-    let message = match tx.prepare_cached("INSERT INTO messages (room, user, data, signature) VALUES (?, ?, ?, ?) RETURNING *")
+    let message = match tx.prepare_cached("INSERT INTO messages (room, user, data, data_size, signature) VALUES (?, ?, ?, ?, ?) RETURNING *")
         .map_err(db_error)?
-        .query_row(params![room.id, user.id, data, signature], OldMessage::from_row) {
+        .query_row(params![room.id, user.id, trimmed, size, signature], OldMessage::from_row) {
         Ok(m) => m,
         Err(e) => {
             error!("Couldn't insert message: {}.", e);
@@ -670,7 +679,7 @@ pub fn delete_message(
 
     require_authorization(conn, user, room, auth_req)?;
 
-    let mut del_st = conn.prepare_cached("UPDATE messages SET data = NULL, signature = NULL WHERE id = ?")
+    let mut del_st = conn.prepare_cached("UPDATE messages SET data = NULL, data_size = NULL, signature = NULL WHERE id = ?")
         .map_err(db_error)?;
 
     if let Err(e) = del_st.execute(params![id]) {
@@ -879,7 +888,7 @@ pub async fn ban(session_id: &str, delete_all: bool, user: &User, room: &Room) -
     let mut posts_removed = 0;
     let mut files_removed = 0;
     if delete_all {
-        posts_removed += match tx.prepare_cached("UPDATE messages SET data = NULL, signature = NULL WHERE room = ? AND user = ?")
+        posts_removed += match tx.prepare_cached("UPDATE messages SET data = NULL, data_size = NULL, signature = NULL WHERE room = ? AND user = ?")
             .map_err(db_error)?
             .execute(params![room.id, userid]) {
             Ok(count) => count,

src/models.rs

@@ -56,7 +56,8 @@ pub struct OldMessage {
 
 impl OldMessage {
     pub fn from_row(row: &rusqlite::Row) -> Result<OldMessage, rusqlite::Error> {
-        let data: Option<Vec<u8>> = row.get(row.column_index("data")?)?;
+        let mut data: Option<Vec<u8>> = row.get(row.column_index("data")?)?;
+        repad(&mut data, row.get::<_, Option<usize>>(row.column_index("data_size")?)?);
         let session_id = match row.column_index("session_id") {
             Ok(index) => Some(row.get(index)?),
             Err(_) => None
@@ -98,9 +99,18 @@ pub struct Message {
     pub deleted: Option<bool>,
 }
 
+fn repad(data: &mut Option<Vec<u8>>, size: Option<usize>) {
+    if let Some(size) = size {
+        if data.is_some() && data.as_ref().unwrap().len() < size {
+            data.as_mut().unwrap().resize(size, 0);
+        }
+    }
+}
+
 impl Message {
     pub fn from_row(row: &rusqlite::Row) -> Result<Message, rusqlite::Error> {
-        let data: Option<Vec<u8>> = row.get(row.column_index("data")?)?;
+        let mut data: Option<Vec<u8>> = row.get(row.column_index("data")?)?;
+        repad(&mut data, row.get::<_, Option<usize>>(row.column_index("data_size")?)?);
         let deleted = if data.is_none() { Some(true) } else { None };
         let session_id = match row.column_index("session_id") {
             Ok(index) => Some(row.get(index)?),

src/schema.sql

@@ -66,7 +66,8 @@ CREATE TABLE messages (
     posted FLOAT NOT NULL DEFAULT ((julianday('now') - 2440587.5)*86400.0), /* unix epoch */
     edited FLOAT,
     updated INTEGER NOT NULL DEFAULT 0, /* set to the room's `updates` counter when posted/edited/deleted */
-    data BLOB, /* Actual message content; set to null to delete a message */
+    data BLOB, /* Actual message content, not including trailing padding; set to null to delete a message */
+    data_size INTEGER, /* The message size, including trailing padding (needed because the signature is over the padded data) */
     signature BLOB /* Signature of `data` by `public_key`; set to null when deleting a message */
 );
 CREATE INDEX messages_room ON messages(room, posted);
@@ -184,7 +185,7 @@ SELECT messages.*, users.session_id FROM messages JOIN users ON messages.user =
 -- View of `messages` that is useful for manually inspecting table contents by only returning the
 -- length (rather than raw bytes) for data/signature.
 CREATE VIEW message_metadata AS
-SELECT id, room, user, session_id, posted, edited, updated, length(data) AS data_length, length(signature) as signature_length
+SELECT id, room, user, session_id, posted, edited, updated, length(data) AS data_unpadded, data_size, length(signature) as signature_length
     FROM message_details;