src/client/backup_reader.rs: factor out download_fixed_index() helper

src/bin/proxmox-backup-client.rs

@@ -1095,14 +1095,8 @@ async fn restore_do(param: Value) -> Result<Value, Error> {
                 .map_err(|err| format_err!("unable to pipe data - {}", err))?;
         }
     } else if server_archive_name.ends_with(".fidx") {
-        let tmpfile = client.download(&server_archive_name, tmpfile).await?;
 
-        let index = FixedIndexReader::new(tmpfile)
+        let index = client.download_fixed_index(&manifest, &server_archive_name).await?;
-            .map_err(|err| format_err!("unable to read fixed index '{}' - {}", archive_name, err))?;
-
-        // Note: do not use values stored in index (not trusted) - instead, computed them again
-        let (csum, size) = index.compute_csum();
-        manifest.verify_file(&server_archive_name, &csum, size)?;
 
         let mut writer = if let Some(target) = target {
             std::fs::OpenOptions::new()

src/client/backup_reader.rs

@@ -162,4 +162,32 @@ impl BackupReader {
 
         Ok(index)
     }
+
+    /// Download fixed index file
+    ///
+    /// This creates a temorary file in /tmp (using O_TMPFILE). The index is verified using
+    /// the provided manifest.
+    pub async fn download_fixed_index(
+        &self,
+        manifest: &BackupManifest,
+        name: &str,
+    ) -> Result<FixedIndexReader, Error> {
+
+        let tmpfile = std::fs::OpenOptions::new()
+            .write(true)
+            .read(true)
+            .custom_flags(libc::O_TMPFILE)
+            .open("/tmp")?;
+
+        let tmpfile = self.download(name, tmpfile).await?;
+
+        let index = FixedIndexReader::new(tmpfile)
+            .map_err(|err| format_err!("unable to read fixed index '{}' - {}", name, err))?;
+
+        // Note: do not use values stored in index (not trusted) - instead, computed them again
+        let (csum, size) = index.compute_csum();
+        manifest.verify_file(name, &csum, size)?;
+
+        Ok(index)
+    }
 }