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Add Termux Remote File Manager: SSH-based file browsing, transfer, editing, and preview with zero re-authentication#5058

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Add Termux Remote File Manager: SSH-based file browsing, transfer, editing, and preview with zero re-authentication#5058
kqnan wants to merge 46 commits intotermux:masterfrom
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@kqnan kqnan commented Apr 8, 2026

Pull Request

Title

Add Termux Remote File Manager: SSH-based file browsing, transfer, editing, and preview with zero re-authentication


Description

Overview

This PR adds a native Android remote file manager to Termux that seamlessly integrates with SSH sessions established via password authentication in the terminal. The key innovation: users can switch to graphical file management with a single tap—no re-entering passwords, no SSH key configuration required.

Core Value: Zero-friction SSH connection reuse via OpenSSH ControlMaster socket injection.

What's Included

4 development phases delivered (14 features, 44 commits):

Phase 1 — Remote File Manager Core (7 features)

  • SSH ControlMaster Auto-Injection: Wrapper script that intercepts SSH commands and enables socket sharing for password-based sessions
  • F Button Entry Point: Folder icon (📁) in Extra Keys toolbar—tap to launch file manager for active SSH session
  • Remote File Browser: Full directory navigation with path breadcrumb, async loading, and error handling
  • File Operations (CRUD): Long-press context menu for delete, rename, and new folder creation with confirmation dialogs
  • Bidirectional File Transfer: Upload/download via Android SAF picker with real-time progress UI; supports binary-safe base64 encoding
  • Code Editor: WebView + CodeMirror integration with 21 language modes (Python, JavaScript, Go, Rust, etc.) and 51 extension mappings
  • Image Preview: Native ImageView with pinch-zoom and pan gestures for remote images

Phase 2 — UX Polish (4 features)

  • SSH Wrapper Dynamic Installation: Fallback install trigger for users who install openssh after first launch
  • Back Key Navigation: Pressing back navigates to parent directory; exits Activity only at root
  • Chinese Localization: 54 translated strings covering all file manager modules
  • Morandi Color Theme: 20-color palette with light/dark mode auto-adaptation

Phase 3 — Large File Transfer Fix (2 features)

  • Event-Driven SSH Wrapper Install: FileObserver-based monitoring replaces polling—installs wrapper automatically when ssh binary appears
  • Chunked File Transfer: 1MB streaming chunks replace single-shot base64 encoding, eliminating OOM for files >50MB; tested up to 100MB

Phase 4 — Symlink Handling (partial, 3 commits)

  • Symlink-to-Directory Display: Folder icon + directory styling for symlinks pointing to directories
  • Symlink Navigation Fix: Correct path handling when entering symlink directories
  • Safe Symlink Deletion: Confirmation dialog clarifies only the link is deleted, not target contents

Stats

Metric Value
Files changed 50
Lines added ~11,000
Unit tests 170+ (all passing)
Test coverage RemoteFileLister, RemoteFileOperator, RemoteFileTransfer, RemoteFileReader, RemoteImageLoader, SSHControlMasterInstaller, SymlinkPath

Key Architecture Decisions

  1. ControlMaster Socket Reuse (not custom SSH stack): Leverages battle-tested OpenSSH; password auth works identically to key auth
  2. base64 Encoding for Transfer: Binary-safe transport without scp/sftp dependencies; SAF provides content URIs, not file paths
  3. 1MB Chunked Streaming: Memory footprint capped at ~2.5MB regardless of file size; dd skip=N seek=N for seekable upload/download
  4. WebView + CodeMirror: Lightweight editor without heavy native dependencies; JavaScript bridge for file read/write via SSH

Files Added

Activities (3):

  • RemoteFileBrowserActivity.java — Main file browser UI
  • RemoteCodeEditorActivity.java — CodeMirror-based editor
  • RemoteImagePreviewActivity.java — Zoomable image preview

Services (8):

  • SSHControlMasterInstaller.java — Wrapper injection logic
  • SSHConnectionInfo.java — Active session detection
  • RemoteFileLister.java — Directory listing via ls -l
  • RemoteFileOperator.java — CRUD via cp/mv/rm/mkdir
  • RemoteFileTransfer.java — Chunked upload/download
  • RemoteFileReader.java / RemoteFileWriter.java — File content access via cat/base64
  • RemoteImageLoader.java — Image fetching with size preview

UI/Resources:

  • Layouts for browser, editor, preview, progress dialog, file list items
  • Morandi color palette (20 colors, light/dark variants)
  • Chinese strings (values-zh/strings.xml)
  • Context menu for file operations
  • Icons for files, folders, symlinks

Testing

All unit tests pass:

./gradlew test --tests "com.termux.app.ssh.*"

How to Test

  1. Build and install APK: ./gradlew assembleDebug && adb install app/build/outputs/apk/debug/termux-app_apt-android-7-debug_arm64-v8a.apk
  2. In Termux terminal: ssh user@host (enter password)
  3. Tap F button (📁) in Extra Keys toolbar
  4. File manager opens showing remote files—no password prompt

Reviewer Notes: This is a substantial feature addition (~11K lines) with full test coverage. Recommend reviewing by phase—Phase 1 core functionality first, then Phase 2/3 polish and fixes. Phase 4 symlink work is minimal (3 commits) and backward-compatible.

kqnan added 30 commits March 29, 2026 16:09
- "app/src/main/java/com/termux/app/ssh/SSHControlMasterInstaller.java"
- "app/src/main/java/com/termux/app/TermuxApplication.java"

GSD-Task: S01/T02
- "app/src/main/java/com/termux/app/ssh/SSHControlMasterInstaller.java"
- "app/build/outputs/apk/debug/termux-app_apt-android-7-debug_x86_64.apk"
- ".gsd/milestones/M001/slices/S01/S01-UAT.md"

GSD-Task: S01/T03
- "app/src/main/java/com/termux/app/ssh/SSHConnectionInfo.java"
- "app/src/main/java/com/termux/app/ssh/SSHControlMasterInstaller.java"

GSD-Task: S02/T01
- "termux-shared/src/main/java/com/termux/shared/termux/extrakeys/ExtraKeysConstants.java"
- "termux-shared/src/main/java/com/termux/shared/termux/settings/properties/TermuxPropertyConstants.java"

GSD-Task: S02/T02
- "app/src/main/java/com/termux/app/terminal/io/TermuxTerminalExtraKeys.java"

GSD-Task: S02/T03
- "app/src/main/java/com/termux/app/ssh/RemoteFile.java"
- "app/src/main/java/com/termux/app/ssh/RemoteFileLister.java"
- "app/src/test/java/com/termux/app/ssh/RemoteFileListerTest.java"

GSD-Task: S03/T01
- "app/src/main/res/layout/activity_remote_file_browser.xml"
- "app/src/main/res/layout/item_remote_file.xml"
- "app/src/main/java/com/termux/app/ssh/RemoteFileListAdapter.java"
- "app/src/main/res/drawable/ic_folder.xml"
- "app/src/main/res/drawable/ic_file.xml"
- "app/src/main/res/drawable/ic_symlink.xml"
- "app/src/main/res/values/strings.xml"

GSD-Task: S03/T02
- "app/src/main/java/com/termux/app/activities/RemoteFileBrowserActivity.java"
- "app/src/main/java/com/termux/app/ssh/SSHConnectionInfo.java"
- "app/src/main/res/layout/activity_remote_file_browser.xml"
- "app/src/main/AndroidManifest.xml"

GSD-Task: S03/T03
- "app/src/main/java/com/termux/app/terminal/io/TermuxTerminalExtraKeys.java"
- "app/src/main/AndroidManifest.xml"

GSD-Task: S03/T04
- "app/src/main/java/com/termux/app/ssh/RemoteFileOperator.java"
- "app/src/test/java/com/termux/app/ssh/RemoteFileOperatorTest.java"

GSD-Task: S04/T01
- "app/src/main/java/com/termux/app/activities/RemoteFileBrowserActivity.java"
- "app/src/main/res/menu/context_menu_remote_file.xml"
- "app/src/main/res/values/strings.xml"

GSD-Task: S04/T02
- "app/src/main/res/layout/activity_remote_file_browser.xml"
- "app/src/main/java/com/termux/app/activities/RemoteFileBrowserActivity.java"

GSD-Task: S04/T03
- "app/src/main/java/com/termux/app/ssh/RemoteFileTransfer.java"
- "app/src/test/java/com/termux/app/ssh/RemoteFileTransferTest.java"

GSD-Task: S05/T01
- "app/src/main/java/com/termux/app/activities/RemoteFileBrowserActivity.java"
- "app/src/main/res/layout/activity_remote_file_browser.xml"
- "app/src/main/res/menu/context_menu_remote_file.xml"
- "app/src/main/res/layout/dialog_transfer_progress.xml"
- "app/src/main/res/values/strings.xml"

GSD-Task: S05/T02
- "app/src/main/java/com/termux/app/ssh/RemoteFileReader.java"
- "app/src/main/java/com/termux/app/ssh/RemoteFileWriter.java"
- "app/src/test/java/com/termux/app/ssh/RemoteFileReaderTest.java"

GSD-Task: S06/T01
- "app/src/main/java/com/termux/app/ssh/CodeMirrorMode.java"
- "app/src/main/assets/code_editor.html"

GSD-Task: S06/T02
- "app/src/main/java/com/termux/app/activities/RemoteCodeEditorActivity.java"
- "app/src/main/res/layout/activity_remote_code_editor.xml"
- "app/src/main/res/menu/menu_code_editor.xml"

GSD-Task: S06/T03
- "app/src/main/java/com/termux/app/activities/RemoteFileBrowserActivity.java"

GSD-Task: S06/T04
- "app/build.gradle"
- "app/src/main/java/com/termux/app/ssh/ImageFileType.java"
- "app/src/test/java/com/termux/app/ssh/ImageFileTypeTest.java"

GSD-Task: S07/T01
- "app/src/main/java/com/termux/app/ssh/RemoteImageLoader.java"
- "app/src/test/java/com/termux/app/ssh/RemoteImageLoaderTest.java"

GSD-Task: S07/T02
- "app/src/main/res/layout/activity_remote_image_preview.xml"
- "app/src/main/java/com/termux/app/activities/RemoteImagePreviewActivity.java"
- "app/src/main/AndroidManifest.xml"
- "app/src/main/java/com/termux/app/activities/RemoteFileBrowserActivity.java"
- "app/src/main/res/values/strings.xml"

GSD-Task: S07/T03
- 将 ssh 命令改为 ssh-real,避免 wrapper 调用自身导致无限递归
- 将 ?attr/termuxActivityDrawerBackground 改为 @color/grey_200,修复主题属性未定义错误
- "app/src/main/java/com/termux/app/terminal/io/TermuxTerminalExtraKeys.java"

GSD-Task: S01/T01
- "app/src/main/java/com/termux/app/activities/RemoteFileBrowserActivity.java"

GSD-Task: S02/T01
- "app/src/main/res/values/colors.xml"
- "app/src/main/res/values/colors_remote_file_browser.xml"
- "app/src/main/res/values-night/colors_remote_file_browser.xml"
- "app/src/main/res/values/themes.xml"
- "app/src/main/res/values-night/themes.xml"
- "app/src/main/res/values/attrs.xml"

GSD-Task: S04/T01
- "app/src/main/java/com/termux/app/ssh/RemoteFileListAdapter.java"
- "app/src/main/res/layout/activity_remote_file_browser.xml"
- "app/src/main/AndroidManifest.xml"

GSD-Task: S04/T02
kqnan added 16 commits April 3, 2026 06:50
- "app/src/main/java/com/termux/app/ssh/SSHControlMasterInstaller.java"

GSD-Task: S01/T01
- "app/src/main/java/com/termux/app/TermuxApplication.java"

GSD-Task: S01/T02
- "app/src/main/java/com/termux/app/ssh/RemoteFileTransfer.java"

GSD-Task: S02/T01
- "app/src/main/java/com/termux/app/ssh/RemoteFileTransfer.java"
- "app/src/test/java/com/termux/app/ssh/RemoteFileTransferTest.java"

GSD-Task: S02/T02
- "app/src/test/java/com/termux/app/ssh/RemoteFileTransferTest.java"

GSD-Task: S02/T03
- "app/src/main/java/com/termux/app/activities/RemoteFileBrowserActivity.java"

GSD-Task: S02/T04
- "e2e-evidence/01-ssh-install.png"
- "e2e-evidence/02-ssh-install-attempt.png"
- "e2e-evidence/03-ssh-install-result.png"
- "e2e-evidence/04-final-status.png"

GSD-Task: S02/T05
FileObserver failed to detect ssh binary creation during openssh package
installation. This commit replaces it with a reliable polling mechanism:

- Poll every 2 seconds to check for ssh binary existence
- Stop polling immediately after ssh is detected and wrapper installed
- Add install-apk-to-emulator.sh and restart-android-emulator.sh scripts

The polling mechanism is more reliable than FileObserver on Android where
SELinux policies and dpkg installation methods may prevent file system
events from being delivered to the application layer.
When a symlink points to a directory, the file browser should navigate
into it instead of trying to open it as a file.

Changes:
- Use 'ls -laF' to get type indicators (/ for dirs, @ for symlinks)
- Add symlinkTargetIsDirectory field to RemoteFile
- Add isDirectoryOrSymlinkToDirectory() method for navigation decisions
- Update RemoteFileListAdapter to show '-' for symlink-to-directory size
- Hide download context menu for symlinks pointing to directories

This fixes the 'cat: Is a directory' error when clicking on symlinks
that point to directories like .gsd -> /root/.gsd/projects/xxx
- "app/src/main/java/com/termux/app/ssh/RemoteFileListAdapter.java"
- "app/src/test/java/com/termux/app/ssh/RemoteFileListerTest.java"

GSD-Task: S01/T01
- "app/src/main/java/com/termux/app/activities/RemoteFileBrowserActivity.java"
- "app/src/main/res/values/strings.xml"
- "app/src/main/res/values-zh/strings.xml"

GSD-Task: S03/T01
Problem: Clicking a symlink-to-directory caused incorrect path concatenation.
For example, clicking .gsd symlink would navigate to:
  /root/termux-app/.gsd/root/termux-app/.gsd

Root cause: When ls -laF executes on a symlink path without trailing slash,
it returns the symlink info itself (with full path in name field) instead
of listing the target directory contents.

Fix 1: Append trailing slash to directory paths in buildSSHCommand.
This ensures ls follows symlinks to directories:
  - "ls -laF symlink" → returns symlink info (wrong)
  - "ls -laF symlink/" → lists directory contents (correct)

Fix 2: Handle abnormal ls output where name field contains absolute path.
Extract last path segment as actual name to prevent path duplication.

Added SymlinkPathTest with 6 test cases covering:
- Normal symlink with absolute path target
- Abnormal symlink where name is absolute path
- Symlink with/without trailing slash
- Regular directories and files
@twaik
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twaik commented Apr 8, 2026

Is it vibe coded?

@sylirre
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sylirre commented Apr 8, 2026

Author vibe coded it but didn't really thought about proper architecture.

@robertkirkman
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robertkirkman commented Apr 8, 2026

I tested it, but unfortunately I was unable to figure out how to use it as intended. I see this:

edit: oh, I think I understand. To activate the functionality, I think it is probably necessary to use these commands:

pkg upgrade
pkg install openssh
passwd
sshd
ssh -p 8022 localhost

only then after that, the folder button might start doing something.

image

private static final String LOG_TAG = "RemoteFileReader";

/** SSH binary path (the wrapper that uses ControlMaster) */
private static final String SSH_BINARY = "/data/data/com.termux/files/usr/bin/ssh";
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Hardcoded prefix.

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@robertkirkman robertkirkman Apr 8, 2026

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In addition, I hadn't mentioned this yet, but since you brought this up, the string /data/data/com.termux is hardcoded multiple times throughout the PR (not only once)

Comment on lines +525 to +536
// Build SSH command: base64 -d | dd of=file bs=1M seek=N conv=notrunc
// For first chunk, we don't need seek; subsequent chunks use seek to append
String remoteCommand;
if (chunkIndex == 0) {
// First chunk: create file
remoteCommand = "base64 -d | dd of=" + escapedPath + " bs=" + TRANSFER_CHUNK_SIZE +
" count=1 2>/dev/null";
} else {
// Subsequent chunks: append at correct offset
remoteCommand = "base64 -d | dd of=" + escapedPath + " bs=" + TRANSFER_CHUNK_SIZE +
" seek=" + chunkIndex + " conv=notrunc 2>/dev/null";
}
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Why not to just implement a proper SFTP client using pure Java? It would be countless times better than such implementation.

If you still want to rely on OpenSSH, ok. But there are scp and sftp designed specifically for file transfer.

Mentioned lines tell everything about implementation quality.

Comment on lines +32 to +45
public void testParseDirectoryLine() {
String line = "drwxr-xr-x 2 user group 4096 Jan 15 10:30 mydir";
Matcher matcher = LS_LINE_PATTERN.matcher(line);

assertTrue("Should match directory line", matcher.matches());
assertEquals("permissions", "drwxr-xr-x", matcher.group(1));
assertEquals("links", "2", matcher.group(2));
assertEquals("owner", "user", matcher.group(3));
assertEquals("group", "group", matcher.group(4));
assertEquals("size", "4096", matcher.group(5));
assertEquals("date", "Jan 15", matcher.group(6));
assertEquals("time", "10:30", matcher.group(7));
assertEquals("name", "mydir", matcher.group(8));
}
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This is not a valid unit test. You are testing hardcoded string against regex rather than behavior of added functionality.

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robertkirkman commented Apr 8, 2026

Ok, after doing that, I was able to progress to this screen. However, the next problem I encountered is that I am unable to see any of the files that I created in the /data/data/com.termux/files/home folder as tests, and when I touch "new folder", it shows an error.

image

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sylirre commented Apr 8, 2026

@robertkirkman It shows files when connected to laptop. But design is utterly bad.

It executes ls -laF / on remote host and then parses output to display file listing.

This will not work for regular Android ROM because listing rootfs is not allowed.


Another issue: it won't work too if you connected first to localhost, exited, then connected to actual remote host. All because ~/.ssh/control directory will have two sockets.

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It executes ls -laF / on remote host and then parses output to display file listing.

hm, yes that is a very bad design and will not work properly, even on desktop linux, because I would not expect / to be the folder I see when I touch that button. I would expect the current working directory of the remote session to be the folder initially shown by the button. I think that the design of the PR needs some rethinking to accommodate that.

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sylirre commented Apr 8, 2026

It does everything through shell commands: file listing (ls -laF), copying (cp or cp -r, conditional), moving (mv <src> <dst>), deleting (rm, conditionally with -f and -r), viewing (cat), directory making (mkdir, conditionally with -p).

File transfer is a similar story: encodes local file to base64, sends it over SSH, on remote decodes it with base64 and writes with dd.

I don't see a way to configure starting directory.

I don't see a way to select desired SSH connection (socket in ~/.ssh/control) when multiple connections are active.

Besides said above, we have also an issue of another kind: silent hijacking of ssh executable with a wrapper script which unconditionally enables SSH sockets under ~/.ssh/control.

https://github.com/kqnan/termux-app/blob/b1a9b9942d9c14be28f2bf121fd4b15ba135219c/app/src/main/java/com/termux/app/ssh/SSHControlMasterInstaller.java#L257

Wrapper script: https://github.com/kqnan/termux-app/blob/b1a9b9942d9c14be28f2bf121fd4b15ba135219c/app/src/main/assets/termux-ssh-wrapper.sh

Finally, this SSH socket is a security issue and should never be set up by default. User must acknowledge the risks before enabling session multiplexing via ControlMaster. I understand that "this is convenience and etc", but I don't want to have this enabled on any of my devices.

SSH client behavior modifications should be done through configuration files. No wrapper scripts should be used.

And as said before, good implementation should include custom SFTP client. This is what all remote file managers use for SSH hosts.

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4 participants