Harden file resume prefix validation

tests/integration_smoke.rs

@@ -3,6 +3,7 @@
 use std::fs;
 use std::io::{Read, Write};
 use std::net::{TcpListener, TcpStream, UdpSocket};
+use std::os::unix::fs::PermissionsExt;
 use std::os::unix::net::{UnixListener, UnixStream};
 use std::path::{Path, PathBuf};
 use std::process::{Child, Command, Stdio};
@@ -1241,6 +1242,80 @@ fn native_file_copy_resume_truncates_oversized_destinations() {
     let _ = server.wait();
 }
 
+#[test]
+fn native_file_copy_resume_prefix_mismatch_preserves_destinations() {
+    let dir = tempfile::tempdir().unwrap();
+    let port = free_udp_port();
+    let config = write_server_config(&dir, port);
+    write_native_client_auth(&dir, &config);
+    let mut server = start_server(&dir, &config);
+    let client_bin = env!("CARGO_BIN_EXE_dosh-client");
+
+    let local_upload = dir.path().join("upload-prefix.txt");
+    let remote_upload = dir.path().join("remote-upload.txt");
+    fs::write(&local_upload, b"local-prefix\n").unwrap();
+    fs::write(&remote_upload, b"remote-prefix-with-tail\n").unwrap();
+    fs::set_permissions(&local_upload, fs::Permissions::from_mode(0o755)).unwrap();
+    fs::set_permissions(&remote_upload, fs::Permissions::from_mode(0o600)).unwrap();
+
+    let bad_upload_resume = Command::new(client_bin)
+        .arg("--dosh-host")
+        .arg("127.0.0.1")
+        .arg("--dosh-port")
+        .arg(port.to_string())
+        .arg("cp")
+        .arg("--resume")
+        .arg(&local_upload)
+        .arg("local:remote-upload.txt")
+        .env("HOME", dir.path())
+        .output()
+        .unwrap();
+    assert!(
+        !bad_upload_resume.status.success(),
+        "bad upload resume unexpectedly succeeded: stdout={} stderr={}",
+        String::from_utf8_lossy(&bad_upload_resume.stdout),
+        String::from_utf8_lossy(&bad_upload_resume.stderr)
+    );
+    assert_eq!(
+        fs::read_to_string(&remote_upload).unwrap(),
+        "remote-prefix-with-tail\n"
+    );
+    assert_eq!(
+        fs::metadata(&remote_upload).unwrap().permissions().mode() & 0o777,
+        0o600
+    );
+
+    fs::write(dir.path().join("remote-download.txt"), b"remote-download\n").unwrap();
+    let local_download = dir.path().join("download-prefix.txt");
+    fs::write(&local_download, b"local-download-with-tail\n").unwrap();
+
+    let bad_download_resume = Command::new(client_bin)
+        .arg("--dosh-host")
+        .arg("127.0.0.1")
+        .arg("--dosh-port")
+        .arg(port.to_string())
+        .arg("cp")
+        .arg("--resume")
+        .arg("local:remote-download.txt")
+        .arg(&local_download)
+        .env("HOME", dir.path())
+        .output()
+        .unwrap();
+    assert!(
+        !bad_download_resume.status.success(),
+        "bad download resume unexpectedly succeeded: stdout={} stderr={}",
+        String::from_utf8_lossy(&bad_download_resume.stdout),
+        String::from_utf8_lossy(&bad_download_resume.stderr)
+    );
+    assert_eq!(
+        fs::read_to_string(&local_download).unwrap(),
+        "local-download-with-tail\n"
+    );
+
+    let _ = server.kill();
+    let _ = server.wait();
+}
+
 #[test]
 fn native_exec_command_smoke() {
     let dir = tempfile::tempdir().unwrap();