double validate downloaded demo

src/backup.rs

@@ -20,10 +20,21 @@ impl Backup {
     async fn backup_demo(&self, name: &str, demo: &Demo) -> Result<(), Error> {
         info!("backing up");
 
-        let mut file = self.store.create(name).await?;
+        {
+            let file = self.store.create(name).await?;
+            demo.save(&self.client, file).await?;
+        }
 
-        demo.save(&self.client, &mut file).await?;
-        Ok(())
+        let digest = self.store.hash(name)?;
+        if digest == demo.hash || digest == [0; 16] {
+            Ok(())
+        } else {
+            let _ = self.store.remove(name);
+            Err(Error::DigestMismatch {
+                expected: demo.hash,
+                got: digest,
+            })
+        }
     }
 
     #[instrument(skip(self))]

src/main.rs

@@ -16,6 +16,8 @@ pub enum Error {
     Request(#[from] std::io::Error),
     #[error(transparent)]
     Api(#[from] demostf_client::Error),
+    #[error("MD5 digest mismatch for downloaded demo, expected {expected:?}, received {got:?}")]
+    DigestMismatch { expected: [u8; 16], got: [u8; 16] },
 }
 
 #[tokio::main]

src/store.rs

@@ -1,6 +1,8 @@
 use crate::Error;
+use md5::Context;
 use std::fs;
 use std::fs::{File, Permissions};
+use std::io::Read;
 use std::os::unix::fs::PermissionsExt;
 use std::path::{Path, PathBuf};
 
@@ -33,6 +35,28 @@ impl Store {
         fs::remove_file(self.generate_path(name))
     }
 
+    pub fn hash(&self, name: &str) -> Result<[u8; 16], Error> {
+        let path = self.generate_path(name);
+        let mut file = File::open(path)?;
+
+        let mut hash = Context::new();
+
+        let mut buff = vec![0; 1024 * 1024];
+
+        loop {
+            let read = file.read(&mut buff)?;
+
+            if read == 0 {
+                break;
+            }
+
+            let data = &buff[0..read];
+            hash.consume(&data);
+        }
+
+        Ok(hash.compute().0)
+    }
+
     fn generate_path(&self, name: &str) -> PathBuf {
         let mut path = self.basedir.clone();
         path.push(&name[0..2]);