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DeltaFeedback

Self-hosted contact form for a personal site. Visitors submit messages via a tiny HTML form; messages reach you over Delta Chat, where you reply through the standard DC "reply" feature. Replies appear on the visitor's ticket page in real time.

• Single C++ binary, single SQLite file.
• POW captcha (SHA-256 hashcash, 18 bits default) + honeypot + form fill-time check.
• Per-locale welcome HTML, browser-language switcher (ru / en).
• One admin: the first contact to message the bot becomes admin; everyone else is silently blocked.
• Tickets are purged 7 days after the last activity (any side).
• Admin replies route via DC's quote/reply — no [ID] typing required; [ID] fallback still works for cross-device cases.

License: GPLv3.

Dependencies

• C++17 toolchain (g++ or clang)
• CMake ≥ 3.16
• libsqlite3-dev, libssl-dev, libasio-dev
• libdeltachat from deltachat-core-rust, built ahead of time

CrowCpp 1.2.0 and gtest are fetched by CMake.

Build

cmake -S . -B build
cmake --build build -j$(nproc)
ctest --test-dir build

CMakeLists.txt looks for libdeltachat.so under ../deltachatbot-cpp/deltachat-core-rust/target/release/. Override with -DDC_CORE=/path/to/deltachat-core-rust if it lives elsewhere.

Configure and run

cp config.example.ini config.ini
./build/deltafeedback --register <chatmail-domain> config.ini
./build/deltafeedback --run config.ini

--register creates a new chatmail account and writes credentials either into the same config file (dev) or into the account file referenced by the account_path= key (production — see the Debian package section). --run starts the DC event loop and the HTTP server (default 0.0.0.0:8080). On the first run the bot prints a Delta Chat invite URL — open it in your DC client to add the bot; your account becomes admin.

If config is omitted, ./config.ini is used.

Show invite URL

./build/deltafeedback --invite config.ini

Prints the current Delta Chat invite URL to stdout. Useful under systemd where the service's stdout goes to journald, or after --reset-admin.

Reset admin

./build/deltafeedback --reset-admin config.ini

Clears the owner contact id and removes all tickets and POW state. The next contact to message the bot becomes the new admin.

Behind a reverse proxy

Visitor IP is read from X-Forwarded-For (leftmost), then X-Real-IP, falling back to the connecting peer. Bind to 127.0.0.1 in production and let caddy/nginx terminate TLS.

Debian package

Pre-built .deb artifacts for Debian 12 (bookworm) and 13 (trixie) are produced by GitHub Actions on every push to main — see the workflow at .github/workflows/deb.yml. Releases (tags v*) attach the artifacts to the GitHub Release.

To build locally:

cmake -S . -B build && cmake --build build -j
./packaging/build-deb.sh   # writes dist/deltafeedback_<ver>_<codename>_<arch>.deb

The package installs:

Path	Purpose
/usr/bin/deltafeedback	binary
/usr/lib/deltafeedback/libdeltachat.so	bundled DC core (rpath wired)
/usr/share/deltafeedback/web/	frontend assets — overwritten on upgrade EXCEPT welcome.{ru,en}.html
/usr/share/deltafeedback/welcome.defaults/	seed copies for the welcome block; postinst installs them into web/ only when missing
/etc/deltafeedback/config.example.ini	reference config — overwritten on upgrade
/etc/deltafeedback/config.ini	active config — never overwritten
/var/lib/deltafeedback/account.ini	mutable creds + hmac_secret (writable by service user)
/var/lib/deltafeedback/	SQLite + DC database (created on install)
/lib/systemd/system/deltafeedback.service	systemd unit

/etc/deltafeedback/config.ini stays root-owned and read-only. Mutable runtime state (addr, mail_pw, hmac_secret) goes into /var/lib/deltafeedback/account.ini, which the postinst creates owned by the deltafeedback user. The link between them is the account_path= key in the main config.

Post-install:

sudo -u deltafeedback deltafeedback --register <chatmail-domain> /etc/deltafeedback/config.ini
sudo systemctl enable --now deltafeedback.service
sudo -u deltafeedback deltafeedback --invite /etc/deltafeedback/config.ini   # show invite URL

Customise the welcome block

Plain HTML; an empty file hides the block. Re-fetched on language switch.

• Dev: edit web/welcome.ru.html and web/welcome.en.html in the source tree.
• Debian package: edit /usr/share/deltafeedback/web/welcome.{ru,en}.html. These files are NOT in the package data archive at the served path — they're seeded by postinst from welcome.defaults/ on first install, so subsequent apt upgrade runs leave your customisations alone.