MicroBin Share

A minimal Android share-sheet target that uploads files (and text) to a self-hosted MicroBin instance, mirroring the request contract of mb-cli. It adds an Upload to MicroBin entry to the system share sheet. Files are sent with the configured uploader_password; text pastes are sent without one, since the reference instance requires the password for file uploads only.

There is intentionally no admin/list/delete surface — open the instance in a browser for that.

What it does

• Share one or more files → each is POSTed to /upload with the saved file password; the resulting …/p/{key} links are shown and copied to the clipboard.
• Share text → POSTed to /upload as a paste with an empty password.
• Tapping the app icon opens a small settings screen (instance URL, file password, default expiration and privacy, plus a connection test).

Request contract

The upload path reproduces mb-cli exactly and was validated against a live instance:

• POST {base}/upload, multipart/form-data, fixed Content-Length (non-chunked).
• Fields, in order: content, expiration, burn_after, privacy, syntax_highlight, uploader_password, encrypt_client, plain_key, random_key, encrypted_random_key, then a file part for file uploads.
• Redirects are not followed; the Location header of the 302 is read directly. A location ending in /incorrect means the password was rejected; otherwise the final path segment is the key and the share link is {base}/p/{key}.

The Uploader class has no Android dependencies, so its multipart output can be diffed against the reference client byte-for-byte.

Layout

AndroidManifest.xml
build.sh                       no-Gradle build (aapt2 / d8 / zipalign / apksigner)
src/ph/dgsd/mbshare/
    Uploader.java              multipart POST, redirect + /incorrect handling
    Prefs.java                 SharedPreferences configuration
    ShareActivity.java         ACTION_SEND / ACTION_SEND_MULTIPLE handler
    SettingsActivity.java      launcher + configuration screen
res/values/strings.xml
res/values/arrays.xml          expiration / privacy option values
res/layout/activity_share.xml
res/layout/activity_settings.xml

No third-party dependencies: the app compiles against android.jar alone, which is what makes the Gradle-free build practical. The launcher icon references the framework drawable ic_menu_upload; drop in a real icon later if desired.

Build

Prerequisites: a JDK (javac, keytool), Android SDK build-tools (aapt2, d8, zipalign, apksigner), a platform android.jar, and zip.

./build.sh

The script auto-detects ANDROID_SDK_ROOT (or set it explicitly) and picks the highest installed build-tools and platform. Override with BUILD_TOOLS, PLATFORM, MIN_SDK, TARGET_SDK, OUT.

If build-tools or a platform are missing:

sdkmanager "build-tools;34.0.0" "platforms;android-34"

Signing

The script signs in this order of precedence:

1. Java keystore — set KEYSTORE (and optionally KEY_ALIAS, KEYSTORE_PASS, KEY_PASS):

   KEYSTORE=~/keys/release.jks KEY_ALIAS=release \
   KEYSTORE_PASS=... KEY_PASS=... ./build.sh

2. Platform PEM + PKCS#8 — sign with the platform key so the app can run as android:sharedUserId="android.uid.system" or live in priv-app on your ROM:

   PLATFORM_CERT=~/keys/platform.x509.pem \
   PLATFORM_KEY=~/keys/platform.pk8 ./build.sh

3. Debug key — if nothing is supplied, a throwaway build/debug.keystore is generated so the build completes.

The app requests only INTERNET (a normal permission), so platform signing and system placement are optional — a plain user install works. Sign with the platform key only if you specifically want it in priv-app.

Install

adb install -r mbshare.apk

To install as a system app on your ROM, place the platform-signed APK under priv-app (or product/priv-app) in the usual way for your build. No privileged permissions are declared, so this is not required for normal use.

Use

1. Open the app once; set the instance URL and the file upload password; Save. (Use Test connection to confirm reachability and that the instance advertises the uploader_password field.)
2. From any app, Share → Upload to MicroBin. The link(s) are shown and copied to the clipboard; Open launches the first in a browser.

Notes

• Password storage. The file password is kept in plain text in the app's private SharedPreferences (/data/data/ph.dgsd.mbshare/shared_prefs/), readable only by the app's UID and root. This is a deliberate tradeoff for a single-user utility and avoids pulling in androidx.security. Substitute EncryptedSharedPreferences in Prefs if a stronger guarantee is wanted.
• Temp copy. Shared content is copied to the app cache before upload so the exact byte length is known for the fixed-length POST regardless of what the content provider reports for size. The copy is deleted after each item. For routine shares (photos, documents, screenshots) the transient disk use is negligible; adjust copyToCache if streaming very large files directly is preferred.
• Expiration cap. The instance caps expiration at 1week; the spinner offers only values it accepts.
• Defaults. The instance URL defaults to https://p.dgsd.ph and privacy to public; change these in settings as needed.