SilentSilo core

The engine behind SilentSilo: the cryptography, the persisted formats, the operation log, sync against storage the user controls, and the standalone extraction tool. AGPL-3.0.

Nothing here knows about a user interface. The desktop application lives in silentsilo/desktop and pins a tag from this repository. Mobile clients will do the same.

No independent security audit has been done. Nobody outside this project has been paid to attack it. The cryptography is specified in docs/CRYPTO.md, the formats in FORMATS.md, and all of this is readable here. That makes the design reviewable; it is not the same as an audit, and a serious flaw could sit in code that looks right and passes its tests.

Crates

Crate	Role
silentsilo-core	Shared types and errors
silentsilo-crypto	AES-GCM streaming, envelope encryption, blob format
silentsilo-vault	Silo provisioning, keys on disk, the index sealed at rest and ciphered while open
silentsilo-vfs	Operation log, folder and file tree, name resolution, snapshots
silentsilo-sync	Bucket layout and the transport half of a sync pass
silentsilo-store	Backup storage: bucket, folder, WebDAV or SFTP
silentsilo-s3	S3-compatible object storage client
silentsilo-fido	FIDO2 security keys and Windows Hello
silentsilo-extract	Standalone recovery binary, no interface, no hardware key
silentsilo-fixture	Format compatibility corpus
silentsilo-testkit	Dev-only: hostile conditions, skip detector

Recovering a silo without this project

silentsilo-extract is the answer to "what if the project disappears". It takes a silo folder or a bucket and a recovery code, and writes out the files, the trash to one side, the passwords as CSV and the attachments. No interface, no security key, one source that builds on Windows, Linux and macOS.

Binaries for all three ship with every desktop release, on the silentsilo/desktop releases page, built from the core tag that release pins and signed with the same minisign key the updater checks. The public half is in SIGNING-PUBKEY.txt. This repository publishes tags, not releases.

Unfinished uploads on S3

Files over 16 MiB go up to S3 in parts. If the app is killed mid-upload, the parts already sent stay in the bucket, billed, and no object listing shows them. SilentSilo aborts them when it uploads that file again, and its daily sweep aborts any older than 24 hours. As a second line of defence, add a lifecycle rule to the bucket with the action "AbortIncompleteMultipartUpload" (7 days is a sensible value). Most S3-compatible providers accept the same rule.

Dev

cargo test --all

Integration tests

The sync and storage tests run against real servers, and skip themselves unless one is configured. scripts/test-local.ps1 brings up MinIO (built from source, which needs Go), WebDAV and SFTP (in containers), points the tests at them, and runs the whole CI sequence:

./scripts/test-local.ps1

It sets SILENTSILO_TEST_REQUIRE_BACKENDS, which turns a suite that skips itself into a failure: asking for those tests and getting a silent pass is how they went a development cycle without running. -Stop takes the containers down again.

To point the tests at a server you already have, set the endpoint yourself:

SILENTSILO_TEST_S3_ENDPOINT=http://127.0.0.1:9000 cargo test -p silentsilo-s3 -p silentsilo-sync

Compatibility fixtures

cargo test -p silentsilo-fixture rebuilds a silo written by a past release from its storage, using only a recovery code, and compares what comes out. A fixture whose output changes means released data no longer reads the same way. The fix goes in the code, never in the fixture.

A note for Windows

The fixture corpus has file names long enough that a clone into a deeply nested directory can hit the 260-character path limit. If git clone reports "Filename too long", enable long paths once:

git config --global core.longpaths true

SQLCipher builds a vendored OpenSSL, which needs Perl. Git Bash's own Perl does not work: install Strawberry Perl, and from Git Bash point at it with PERL=/c/Strawberry/perl/bin/perl.exe. OpenSSL's configure also fails when a path under the target directory passes 260 characters, so keep the checkout, or CARGO_TARGET_DIR, short. The first build takes several minutes longer.

Cross-building for Android from Windows needs a Unix-style Perl with its full module set (MSYS2's /c/msys64/usr/bin/perl.exe, not Git's), make on the path, and the NDK's clang.exe as CC_aarch64_linux_android with CFLAGS_aarch64_linux_android=--target=aarch64-linux-android31: OpenSSL's build runs under sh, which loses the backslash in the .cmd wrapper's path.

HTTPS on Android

S3 and WebDAV check certificates with Android's own verifier (rustls-platform-verifier), which calls into the JVM. An app linking these crates has to do three things, or every HTTPS handshake fails with "secure connections are not set up":

1. Call silentsilo_store::init_android_tls(env, context) once from its JNI entry point, before any sync, with the raw JNIEnv pointer and a raw reference to the application Context. Raw pointers, so the app can use any jni release.
2. Ship the verifier's Kotlin half. It comes inside the rustls-platform-verifier-android crate as a local Maven repository: add that crate's maven folder as a repository (find it with cargo metadata --filter-platform aarch64-linux-android) and depend on rustls:rustls-platform-verifier:latest.release. The crate's README has the Gradle snippet.
3. Keep the class from shrinking: -keep, includedescriptorclasses class org.rustls.platformverifier.** { *; }

Docs

Persisted formats, their versions, and what an older build does when it meets a newer one: FORMATS.md

Cryptography specification: docs/CRYPTO.md

How the pieces fit and which invariants a change must preserve: docs/ARCHITECTURE.md