vicrodh
1743c9e5ec
Foundation for the offline-cache hardening story. The offline cache needs to persist per-track AES content keys to disk, but storing them plaintext would make copying the SQLite DB enough to decrypt the cached audio on another machine. qbz-secrets provides a uniform wrap/unwrap API backed by: 1. **OS keyring** (preferred): libsecret/gnome-keyring on Linux, Keychain on macOS, DPAPI on Windows. A 256-bit master AES key lives inside the OS secure store; all wraps go through it. This is the gold-standard device binding used by commercial music apps (Spotify, Apple Music, Tidal) for the same class of data. 2. **HKDF fallback**: when the OS keyring is not reachable (headless setups — Raspberry Pi, Docker, the future qbzd daemon on a server), the master key is derived on demand via HKDF-SHA256 over service_name + machine_id + a persistent per-install UUID. Weaker than keyring (reversible by anyone with filesystem access to both sources) but still device-bound against cross-machine copy attacks, and lets daemon/headless variants work at all. Every wrap uses AES-256-GCM with a fresh random 12-byte nonce. The on-disk envelope carries a version byte + backend marker + nonce + ciphertext+tag, so (a) we detect tampering via GCM, (b) we refuse to silently unwrap a blob produced by a backend we can't reach, and (c) we have a forward-compat path for future key rotation. 4 unit tests cover: small-secret round-trip, 16-byte content-key round-trip (the exact CMAF use case), GCM tamper detection, and nonce-randomness (two wraps of the same input differ). This crate intentionally has zero QBZ dependencies — it's a generic primitive. Next commits wire it into the offline cache schema + the DB migration. cc
39 lines
1.0 KiB
TOML
39 lines
1.0 KiB
TOML
[package]
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name = "qbz-secrets"
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version.workspace = true
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edition.workspace = true
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license.workspace = true
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description = "Device-bound secret wrapping for QBZ (offline cache keys, tokens)"
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[dependencies]
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# AES-256-GCM for the at-rest wrap/unwrap
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aes-gcm = "0.10"
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# KDF for the fallback path when OS keyring isn't available
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hkdf = "0.12"
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sha2 = "0.10"
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# RNG for nonces + install UUID generation
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rand = "0.9"
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# OS keyring backends: libsecret/secret-service (Linux), Keychain (macOS),
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# DPAPI (Windows). Default features on v3 already pick the right backend
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# per platform; if it fails at runtime we fall through to the KDF path.
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keyring = "3"
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# UUID for the persistent install identifier (salt component for fallback)
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uuid = { version = "1", features = ["v4", "serde"] }
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# Serde for the on-disk wrapper blob envelope
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serde = { workspace = true }
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# Base64 for keyring-roundtripped master key (secret-service expects a UTF-8 string)
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base64 = { workspace = true }
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# Errors
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thiserror = { workspace = true }
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log = { workspace = true }
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[dev-dependencies]
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tempfile = "3"
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