feat: fail on too new backups (#6580)

this PR checks the number from `DCBACKUP?:` and also adds it to the
backup file and checks it there

closes #2294 if we would reopen it

src/imex.rs

@@ -23,6 +23,7 @@ use crate::events::EventType;
 use crate::key::{self, DcKey, DcSecretKey, SignedPublicKey, SignedSecretKey};
 use crate::log::LogExt;
 use crate::pgp;
+use crate::qr::DCBACKUP_VERSION;
 use crate::sql;
 use crate::tools::{
     create_folder, delete_file, get_filesuffix_lc, read_file, time, write_file, TempPathGuard,
@@ -392,6 +393,9 @@ async fn import_backup_stream_inner<R: tokio::io::AsyncRead + Unpin>(
             .await
             .context("cannot import unpacked database");
     }
+    if res.is_ok() {
+        res = check_backup_version(context).await;
+    }
     if res.is_ok() {
         res = adjust_bcc_self(context).await;
     }
@@ -776,6 +780,10 @@ async fn export_database(
         .sql
         .set_raw_config_int("backup_time", timestamp)
         .await?;
+    context
+        .sql
+        .set_raw_config_int("backup_version", DCBACKUP_VERSION)
+        .await?;
     sql::housekeeping(context).await.log_err(context).ok();
     context
         .sql
@@ -813,6 +821,15 @@ async fn adjust_bcc_self(context: &Context) -> Result<()> {
     Ok(())
 }
 
+async fn check_backup_version(context: &Context) -> Result<()> {
+    let version = (context.sql.get_raw_config_int("backup_version").await?).unwrap_or(2);
+    ensure!(
+        version <= DCBACKUP_VERSION,
+        "Backup too new, please update Delta Chat"
+    );
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
     use std::time::Duration;

src/qr.rs

@@ -40,7 +40,11 @@ const HTTPS_SCHEME: &str = "https://";
 const SHADOWSOCKS_SCHEME: &str = "ss://";
 
 /// Backup transfer based on iroh-net.
-pub(crate) const DCBACKUP2_SCHEME: &str = "DCBACKUP2:";
+pub(crate) const DCBACKUP_SCHEME_PREFIX: &str = "DCBACKUP";
+
+/// Version written to Backups and Backup-QR-Codes.
+/// Imports will fail when they have a larger version.
+pub(crate) const DCBACKUP_VERSION: i32 = 2;
 
 /// Scanned QR code.
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -118,6 +122,9 @@ pub enum Qr {
         auth_token: String,
     },
 
+    /// The QR code is a backup, but it is too new. The user has to update its Delta Chat.
+    BackupTooNew {},
+
     /// Ask the user if they want to use the given service for video chats.
     WebrtcInstance {
         /// Server domain name.
@@ -296,7 +303,7 @@ pub async fn check_qr(context: &Context, qr: &str) -> Result<Qr> {
         decode_tg_socks_proxy(context, qr)?
     } else if qr.starts_with(SHADOWSOCKS_SCHEME) {
         decode_shadowsocks_proxy(qr)?
-    } else if starts_with_ignore_case(qr, DCBACKUP2_SCHEME) {
+    } else if starts_with_ignore_case(qr, DCBACKUP_SCHEME_PREFIX) {
         let qr_fixed = fix_add_second_device_qr(qr);
         decode_backup2(&qr_fixed)?
     } else if qr.starts_with(MAILTO_SCHEME) {
@@ -367,7 +374,9 @@ pub fn format_backup(qr: &Qr) -> Result<String> {
             ref auth_token,
         } => {
             let node_addr = serde_json::to_string(node_addr)?;
-            Ok(format!("{DCBACKUP2_SCHEME}{auth_token}&{node_addr}"))
+            Ok(format!(
+                "{DCBACKUP_SCHEME_PREFIX}{DCBACKUP_VERSION}:{auth_token}&{node_addr}"
+            ))
         }
         _ => Err(anyhow!("Not a backup QR code")),
     }
@@ -643,11 +652,19 @@ fn decode_shadowsocks_proxy(qr: &str) -> Result<Qr> {
     })
 }
 
-/// Decodes a [`DCBACKUP2_SCHEME`] QR code.
+/// Decodes a `DCBACKUP` QR code.
 fn decode_backup2(qr: &str) -> Result<Qr> {
-    let payload = qr
-        .strip_prefix(DCBACKUP2_SCHEME)
-        .ok_or_else(|| anyhow!("Invalid DCBACKUP2 scheme"))?;
+    let version_and_payload = qr
+        .strip_prefix(DCBACKUP_SCHEME_PREFIX)
+        .ok_or_else(|| anyhow!("Invalid DCBACKUP scheme"))?;
+    let (version, payload) = version_and_payload
+        .split_once(':')
+        .context("DCBACKUP scheme separator missing")?;
+    let version: i32 = version.parse().context("Not a valid number")?;
+    if version > DCBACKUP_VERSION {
+        return Ok(Qr::BackupTooNew {});
+    }
+
     let (auth_token, node_addr) = payload
         .split_once('&')
         .context("Backup QR code has no separator")?;

src/qr/qr_tests.rs

@@ -917,5 +917,11 @@ async fn test_decode_backup() -> Result<()> {
     let qr = check_qr(&ctx, r#"DCBACKUP2:AIvFjRFBt_aMiisSZ8P33JqY&{"node_id":"buzkyd4x76w66qtanjk5fm6ikeuo4quletajowsl3a3p7l6j23pa","info":{"relay_url":null,"direct_addresses":["192.168.1.5:12345"]}}"#).await?;
     assert!(matches!(qr, Qr::Backup2 { .. }));
 
+    let qr = check_qr(&ctx, r#"DCBACKUP9:from-the-future"#).await?;
+    assert!(matches!(qr, Qr::BackupTooNew { .. }));
+
+    let qr = check_qr(&ctx, r#"DCBACKUP99:far-from-the-future"#).await?;
+    assert!(matches!(qr, Qr::BackupTooNew { .. }));
+
     Ok(())
 }