1cd05d91200172c3d5a1b03fe34f7e0b224f9012
2
Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
  octoturgeandClaude Opus 5
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1cd05d9120
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Accept an AES-encrypted config bundle from the cloud
The bundle is authored by Continuum Cloud's configurator and downloaded by
the customer, so it travels over the internet and then on a USB stick while
holding the gateway token and possibly a wifi PSK. That makes it a secret at
rest, and confidentiality is the benefit encryption actually delivers here.
WinZip AES-256 ("AE-x"), via the zip crate's `aes-crypto` feature. That
pulls in aes, hmac, pbkdf2, sha1, constant_time_eq and zeroize - all
permissive (MIT/Apache-2.0, and CC0-1.0 OR MIT-0 OR Apache-2.0 for
constant_time_eq), each checked against docs/LICENSES.md, and
`cargo deny check licenses` passes.
**Legacy ZipCrypto is refused outright**, whatever key is configured: it
falls to a known-plaintext attack. The test is on metadata, not on a failed
decrypt - `encrypted()` is set for ZipCrypto and AES alike, but only AES
carries the AE-x extra field, so encrypted-without-it is ZipCrypto and the
whole bundle is rejected. Judged in the first pass, before any decrypt call,
so the crate's ZipCrypto path never runs on our input. Mixed bundles - one
entry encrypted, the other not - are rejected too.
The caps now bound *decrypted* output, so a small ciphertext that inflates
is capped exactly as a plaintext bomb is. Everything else holds unchanged
for an encrypted bundle: zip-slip, the inner config.toml.sha256, the
no-environment validation, atomic install, and a rejected bundle never
touching the installed config.
Failures are distinguished, because "wrong key" and "damaged" need different
answers: no key on the box and a wrong key both say "not for this box", while
tampered or damaged ciphertext says it failed its AES integrity check. A
wrong key passes AES's 16-bit password check 1 time in 65536 and then fails
the HMAC, so that message names a wrong key as a possibility.
**The limitation to be clear about: with plaintext bundles still accepted,
encryption does nothing against tampering.** An attacker supplies a
plaintext bundle and never touches the crypto. The tamper goal only begins to
hold once `accept_unencrypted` is false, which is one line in main.rs and is
deliberately not flipped yet - doing so breaks every stick made before the
configurator encrypts, and every hand-made development stick. That is a
product decision, not a code one.
More generally, encryption is not authenticity: the AES HMAC detects
modification only by someone without the password, and the password has to
live on the box, so extracting it from one image breaks every box sharing it.
It raises the bar from "anyone with a text editor" to "anyone who can read a
firmware image". The module docs say exactly that and do not call it
tamper-proof. `check_authenticity` is a named no-op where an Ed25519 check
over the config, verified against a *public* key in the box image, belongs -
it verifies nothing and says so, so the missing authenticity is a searchable
gap rather than an implicit one.
`load_bundle_key` is the single marked seam where provisioning lands. Its
current `$CONTINUUM_BUNDLE_KEY_FILE` / `/etc/continuum/bundle.key` lookup is
a placeholder, not a decision: shared-vs-per-box keys, where the key lives,
and rotation are open product questions and the mechanism depends on none of
them.
Encrypted fixtures are genuine AES ZIPs written by the zip crate itself, and
one test confirms the config text is absent from the ciphertext. The
ZipCrypto fixture sets the encrypted flag without an AE-x field, which is the
metadata shape this must refuse. Unproven: interop with whatever ZIP writer
the cloud actually uses (only archives written by this same crate version
were read back), AES-128/192, and `load_bundle_key` itself, which reads
process env and so has no test.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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octoturgeandClaude Opus 5
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47c48ee02d
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Load proxy settings from a file, and import them from a pendrive
Everything came from CONTINUUM_* environment variables, which suits neither shape the product ships in. A Proxy Box is an appliance whose settings arrive on a USB stick; a proxy on someone's PC is a config file they edit. Precedence is stated once, in config.rs: the file is the base, env overrides it, defaults fill the rest. `Config::from_env` keeps its behaviour and the struct is unchanged, so existing callers and tests are untouched. Layering is `Config::layered(file, env_lookup)` with the environment injected as a closure, so tests do not have to mutate process env to cover it. The bootstrap is read from $CONTINUUM_BOOTSTRAP, then /etc/continuum/bootstrap.toml, then nowhere - and nowhere means PC mode with ./continuum.toml, so an env-only deployment behaves exactly as before. The working directory is deliberately not searched, and the bootstrap itself must never come from a stick: it is what says whether sticks are trusted at all. Bundle format is continuum-config.zip holding config.toml and config.toml.sha256. The hash is checked before the bytes are parsed - the TOML parser should not be the first thing to read possibly-corrupt input - and **the comments say plainly what that buys: corruption and change, not forgery.** Anyone who can write the stick writes both files. It is an integrity check under a recorded trust assumption, that physical access to the box is trusted; a signature with the key in the box image is named as the follow-up that would give authenticity. sha256 via openssl, already a direct dependency, so no new crate and `cargo deny check licenses` still passes. The hazards of ingesting a file off removable media, all tested: Zip-slip is refused on absolute paths, `..` components, backslash separators, drive prefixes, NUL and non-UTF-8 names, and one bad entry rejects the whole bundle rather than being skipped. The stronger guarantee is structural though: entries are only ever read **by index, matched against two literal names**, and no write path is ever derived from an archive name, so a hole in the name check still writes nothing. A test confirms a bundle carrying `../evil.toml` alongside a valid config writes nothing outside the target and leaves the installed config alone. Zip bombs are capped at 16 entries, 256 KiB per entry and a 1 MiB file on the stick. Declared sizes are refused in a first pass that decompresses nothing, and a bounded reader then caps actual output so a lying header gains nothing. Installing is atomic: temp file in the destination directory - not /tmp, since rename is only atomic within a filesystem - created 0600 from the first byte because the config holds the gateway token, fsync, rename, then a best-effort directory fsync. A write that fails halfway leaves the previous config intact and no temp file behind. A bad stick never costs the box its config: a bad hash, bad TOML, an unsafe entry or missing settings all return Rejected and are logged as keeping the existing config. A correctly-hashed config is also validated **with no environment at all**, so a stick cannot install something that parses now and fails to start on the next boot - which would be a bricked box caused by exactly the stick we were being careful about. PC mode ignores pendrives twice over, by mode and by an emptied directory list, because on a general-purpose machine importing settings from a USB stick would be a way to change them behind the user's back. A [network] block is parsed, validated and exposed, and stops there. main.rs logs a warning that this build does not apply it, so a box given network settings cannot look like it acted on them. Applying them needs root, is specific to the appliance image, and a wrong write strands the box - it wants its own decision, not a side effect of reading a file. continuum.toml is gitignored, since it holds the gateway token. Not done, and not claimed: no signature, so no authenticity. There is no real pendrive here, so the removable-media path was tested with ordinary directories standing in for mount points - real udisks/udev mounts, FAT behaviour, a genuinely yanked stick and how promptly the 5s poll notices a mount are all unproven. The watcher's install-then-exit flow, which relies on a supervisor restarting the process, has no test and no supervisor exists in this environment; a stick left permanently inserted reports Unchanged rather than looping, because the hash matches. Env still overrides on a box, so a box is only pendrive-only to the extent its environment is trusted - bootstrap.rs says so. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> |