accounts-db: unpack_archive: unpack accounts straight into their fina…

…l destination (solana-labs#289)

* accounts-db: unpack_archive: avoid extra iteration on each path

We used to do a iterator.clone().any(...) followed by
iterator.collect(). Merge the two and avoid an extra iteration and
re-parsing of the path.

* accounts-db: unpack_archive: unpack accounts straight into their final destination

We used to unpack accounts into account_path/accounts/<account> then
rename to account_path/<account>. We now unpack them into their final
destination directly and avoid the rename syscall.

accounts-db/src/hardened_unpack.rs

@@ -112,27 +112,26 @@ where
         // first by ourselves when there are odd paths like including `..` or /
         // for our clearer pattern matching reasoning:
         //   https://docs.rs/tar/0.4.26/src/tar/entry.rs.html#371
-        let parts = path.components().map(|p| match p {
-            CurDir => Some("."),
-            Normal(c) => c.to_str(),
-            _ => None, // Prefix (for Windows) and RootDir are forbidden
-        });
+        let parts = path
+            .components()
+            .map(|p| match p {
+                CurDir => Ok("."),
+                Normal(c) => c.to_str().ok_or(()),
+                _ => Err(()), // Prefix (for Windows) and RootDir are forbidden
+            })
+            .collect::<std::result::Result<Vec<_>, _>>();
 
         // Reject old-style BSD directory entries that aren't explicitly tagged as directories
         let legacy_dir_entry =
             entry.header().as_ustar().is_none() && entry.path_bytes().ends_with(b"/");
         let kind = entry.header().entry_type();
         let reject_legacy_dir_entry = legacy_dir_entry && (kind != Directory);
-
-        if parts.clone().any(|p| p.is_none()) || reject_legacy_dir_entry {
+        let (Ok(parts), false) = (parts, reject_legacy_dir_entry) else {
             return Err(UnpackError::Archive(format!(
                 "invalid path found: {path_str:?}"
             )));
-        }
+        };
 
-        let parts: Vec<_> = parts.map(|p| p.unwrap()).collect();
-        let account_filename =
-            (parts.len() == 2 && parts[0] == "accounts").then(|| PathBuf::from(parts[1]));
         let unpack_dir = match entry_checker(parts.as_slice(), kind) {
             UnpackPath::Invalid => {
                 return Err(UnpackError::Archive(format!(
@@ -159,30 +158,32 @@ where
         )?;
         total_count = checked_total_count_increment(total_count, limit_count)?;
 
-        let target = sanitize_path(&entry.path()?, unpack_dir)?; // ? handles file system errors
-        if target.is_none() {
+        let account_filename = match parts.as_slice() {
+            ["accounts", account_filename] => Some(PathBuf::from(account_filename)),
+            _ => None,
+        };
+        let entry_path = if let Some(account) = account_filename {
+            // Special case account files. We're unpacking an account entry inside one of the
+            // account_paths returned by `entry_checker`. We want to unpack into
+            // account_path/<account> instead of account_path/accounts/<account> so we strip the
+            // accounts/ prefix.
+            sanitize_path(&account, unpack_dir)
+        } else {
+            sanitize_path(&path, unpack_dir)
+        }?; // ? handles file system errors
+        let Some(entry_path) = entry_path else {
             continue; // skip it
-        }
-        let target = target.unwrap();
+        };
 
-        let unpack = entry.unpack(target);
+        let unpack = entry.unpack(&entry_path);
         check_unpack_result(unpack.map(|_unpack| true)?, path_str)?;
 
         // Sanitize permissions.
         let mode = match entry.header().entry_type() {
             GNUSparse | Regular => 0o644,
             _ => 0o755,
         };
-        let entry_path_buf = unpack_dir.join(entry.path()?);
-        set_perms(&entry_path_buf, mode)?;
-
-        let entry_path = if let Some(account_filename) = account_filename {
-            let stripped_path = unpack_dir.join(account_filename); // strip away "accounts"
-            fs::rename(&entry_path_buf, &stripped_path)?;
-            stripped_path
-        } else {
-            entry_path_buf
-        };
+        set_perms(&entry_path, mode)?;
 
         // Process entry after setting permissions
         entry_processor(entry_path);
@@ -1029,4 +1030,27 @@ mod tests {
                 if message == "too many files in snapshot: 1000000000000"
         );
     }
+
+    #[test]
+    fn test_archive_unpack_account_path() {
+        let mut header = Header::new_gnu();
+        header.set_path("accounts/123.456").unwrap();
+        header.set_size(4);
+        header.set_cksum();
+        let data: &[u8] = &[1, 2, 3, 4];
+
+        let mut archive = Builder::new(Vec::new());
+        archive.append(&header, data).unwrap();
+        let result = with_finalize_and_unpack(archive, |ar, tmp| {
+            unpack_snapshot_with_processors(
+                ar,
+                tmp,
+                &[tmp.join("accounts_dest")],
+                None,
+                |_, _| {},
+                |path| assert_eq!(path, tmp.join("accounts_dest/123.456")),
+            )
+        });
+        assert_matches!(result, Ok(()));
+    }
 }