xah30
a070da0be9
Lays the foundation for sing-box mobile clients (Option B from
docs/sing-box.md): an independent Go module that speaks the AuraVPN wire
protocol byte-for-byte. Proof of equivalence is in KAT tests cross-loaded
from a Rust-side deterministic vector exporter.
- tools/export-kat (new Rust bin in workspace): captures a handshake +
derived keys + a sealed datagram record + a knock token using seeded
RNGs (rand::rngs::StdRng + ml-kem's *_deterministic public API), emits
JSON. Reproducible byte-for-byte.
- singbox-aura/ (new Go module, ~3000 LOC, 22 files):
- aura/frame: 5-byte protocol header + Frame{Data,Ping,Pong,Close,
Control} + magic envelope (0xAA,0xAA,0xC0,0x01) — encode/decode
matching aura-proto::frame.
- aura/crypto: hybrid X25519 + ML-KEM-768 (stdlib crypto/ecdh +
crypto/mlkem on Go 1.24+; falls back to circl on older Go via a
documented swap), HKDF-SHA256 derive_session_keys, ChaCha20-Poly1305
with the **LE(u64 counter) || [0;4]** nonce scheme that matches
aura-crypto::AeadKey/AeadSession.
- aura/handshake: client_handshake state machine reproducing protocol.md
§6.2 exactly (CH→SH→ServerAuth→ClientAuth→Finished×2; transcript hash;
ECDSA-P256 transcript signature; HMAC-SHA256 Finished).
- aura/session: DatagramSender/Receiver + 64-wide sliding replay window.
- aura/transport: reliable HS-adapter (DTLS-flight retransmit) + UDP
datagram data path + 16-byte HMAC port-knock with ±1-minute window.
- aura/outbound: sing-box-shaped shim (interface signatures only — sing-
box upstream registration is one more step, documented in README).
- cmd/aura-client: standalone Go binary; reads client.toml via
pelletier/go-toml/v2 and connects to a real aura server. Validates
end-to-end interop with the Rust side.
- KAT: 6 comparisons against Rust vectors — session_keys (HKDF), hybrid
KEM ek/encaps roundtrip, c2s + s2c Finished HMAC, sealed datagram
record at seq=2 (incl. 16-byte Poly1305 tag), knock token. All byte-
for-byte.
Go: 29 tests across 5 packages, all green. Only deps: golang.org/x/crypto
and pelletier/go-toml/v2. Rust: 293 tests still green; tools/export-kat
added to workspace members.
v1 limits documented in singbox-aura/README.md: UDP-only (no TCP/QUIC
fallback yet), no cell padding / cover traffic, no relay/exit role, no
multi-hop, sing-box upstream-registration sketch (vendor sagernet/sing-box +
init() RegisterOutbound) for follow-up.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
47 lines
1.4 KiB
Go
47 lines
1.4 KiB
Go
package crypto
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import (
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"crypto/sha256"
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"hash"
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"golang.org/x/crypto/hkdf"
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)
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// HKDFInfo is the domain-separation string bound into the HKDF expansion.
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// MUST match HKDF_INFO in crates/aura-crypto/src/kdf.rs.
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var HKDFInfo = []byte("aura-v1-session")
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// SessionKeyLen is the size of one directional AEAD key.
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const SessionKeyLen = 32
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// SessionKeys is the pair of directional 256-bit keys produced by the HKDF expansion.
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type SessionKeys struct {
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ClientToServer [SessionKeyLen]byte
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ServerToClient [SessionKeyLen]byte
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}
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// DeriveSessionKeys runs HKDF-SHA256 with
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//
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// salt = client_nonce || server_nonce (64 bytes)
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// IKM = x25519_ss || mlkem_ss (64 bytes)
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// info = "aura-v1-session", OKM 64 bytes -> (c2s, s2c)
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//
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// matching the production helper in crates/aura-crypto/src/kdf.rs byte-for-byte.
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func DeriveSessionKeys(shared *HybridSharedSecret, clientNonce, serverNonce [32]byte) *SessionKeys {
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salt := make([]byte, 64)
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copy(salt[:32], clientNonce[:])
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copy(salt[32:], serverNonce[:])
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ikm := shared.Concat()
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hk := hkdf.New(func() hash.Hash { return sha256.New() }, ikm, salt, HKDFInfo)
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okm := make([]byte, 64)
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if _, err := hk.Read(okm); err != nil {
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// HKDF-Read for 64 bytes from SHA-256 is infallible; treat any error as a bug.
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panic(err)
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}
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var keys SessionKeys
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copy(keys.ClientToServer[:], okm[:32])
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copy(keys.ServerToClient[:], okm[32:])
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return &keys
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}
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