xah30
9b98004424
Closes the v3.1 unlinkability gap and resists volume/timing correlation:
1) Per-hop client cert (identity-unlinkable hops). [[client.circuit.hops]]
now accepts {addr, cert_path, key_path, [server_name]} per hop — each
hop sees a different CN, so a relay and an exit cannot correlate the
same client by certificate. Old flat `hops = ["ip:port"]` form still
parses (serde untagged enum) and falls back to [pki] cert/key.
`aura provision-client --circuit-hops N` mints N fresh UUIDv4 certs.
2) Cell padding. CellPaddingConn wrapper pads every outgoing packet to a
fixed size (default 1280 bytes; `cell_size = N` configurable) before
it hits the inner AEAD. Format: u16_be(real_len) || pkt || zero_pad.
On-wire sizes become constant -> defeats volume/timing fingerprints.
Opt-in via [client.circuit] cell_padding = true and the mirror
[server] cell_padding_for_circuit_clients = true.
3) 3-hop support. dial_circuit now accepts N >= 2 hops; iterative
ExtendBridge nests N-1 forwarders and N handshakes. Client owns the
full chain via CircuitConnection (forwarders abort on drop).
New integration test multihop_v3_2_three_hops_end_to_end runs three
in-process actors (A relay -> B relay -> C exit) on loopback and
verifies peer_id == C's CN.
4) CIDR whitelist. [server.relay] allow_extend_to entries accept
"10.0.0.0/24" (subnet, any port), "10.0.0.0/24:443" (subnet + port),
"[2001:db8::/32]:443" (IPv6 with port), as well as exact IP:port.
Empty list keeps the v3.1 open-relay (warn).
19 new tests; workspace 276 passed (+19), clippy -D warnings clean, fmt clean.
257 baseline tests untouched; all v2 / v3.1 / LE configs work as before.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
173 lines
7.9 KiB
TOML
173 lines
7.9 KiB
TOML
# Aura VPN client configuration (project §9).
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# Copy to client.toml and adjust. Paths may begin with `~` (expands to your home directory).
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[client]
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# Human-readable client name / id.
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name = "laptop"
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# Server UDP socket address.
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server_addr = "203.0.113.10:443"
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# Outer-TLS SNI (camouflage hostname) presented to the server. Also the name verified
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# inside the Aura handshake against the server certificate's SAN.
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sni = "cdn.example.com"
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# Optional: drop privileges to this non-root user AFTER the TUN device has been brought up.
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# Recommended when `aura client` is launched via sudo so the long-running router loop runs
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# as an ordinary user. Linux uses setresuid/setresgid; macOS uses setgid/setuid; Windows is a
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# no-op (use a service account instead). When omitted (or already running as non-root) no
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# privilege change happens.
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# run_as = "nobody"
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# Suppress identifier fields (peer_id, client_ip, source_addr, ...) from log output. The events
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# still fire; only the identifying fields are dropped before formatting. Default: false. Set to
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# true to keep the local log file from accumulating per-session identifiers.
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no_logs = false
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# Optional fallback server addresses (IP or IP:port). When the primary `server_addr` cannot be
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# reached on any transport, the client retries the bridges in a process-randomised order, using
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# the same per-transport ports from [transport]. The bridge `:port` part is parsed but ignored.
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# bridges = ["203.0.113.11", "203.0.113.12"]
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[pki]
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# Trust anchor (the Aura CA) and this client's leaf cert/key, all PEM.
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# Issue with: aura pki issue-client --id laptop --out ~/.aura --ca ~/.aura
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ca_cert = "~/.aura/ca.crt"
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cert = "~/.aura/client.crt"
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key = "~/.aura/client.key"
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[tunnel]
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# Requested TUN interface name (advisory on macOS, where the kernel assigns utunN).
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tun_name = "aura0"
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# Local address assigned to the TUN device, and its prefix length.
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local_ip = "10.7.0.2"
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prefix = 24
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# TUN MTU.
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mtu = 1420
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# Tunnel resolver DNS (informational; the system resolver is used in v1).
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dns = "10.7.0.1"
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# Split-tunnel routing: the default action plus per-destination overrides.
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[tunnel.split]
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# Default for destinations matching no rule below: "VPN" or "DIRECT".
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default = "VPN"
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# Send these directly (bypass the tunnel): RFC1918 ranges stay on the LAN...
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[[tunnel.split.direct]]
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cidr = "192.168.0.0/16"
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[[tunnel.split.direct]]
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cidr = "10.0.0.0/8"
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# ...and a corporate domain egresses directly (resolved to host routes at startup).
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[[tunnel.split.direct]]
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domain = "intranet.example.com"
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# Force a more-specific range back through the VPN (longest-prefix wins over 10.0.0.0/8).
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[[tunnel.split.vpn]]
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cidr = "10.7.0.0/24"
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# v2: OS-level split-tunnel routing. With `enabled = true` (the default) the client programs the
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# system routing table at startup so DIRECT destinations bypass the TUN entirely — they continue
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# to use the host's original default gateway, while only VPN-classified traffic reaches the
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# tunnel. This eliminates the v1 user-space `send_direct` stub, where DIRECT packets were merely
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# logged and dropped. The guard is RAII: the routes are rolled back when `aura client` exits.
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#
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# Linux: uses `ip route add ... via <gw> dev <egress>` for bypasses and `ip route add ... dev <tun>`
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# for the VPN default; the VPN default carries metric 50 so it wins over DHCP-installed defaults.
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# macOS: uses `route add -net <cidr> <gw>` for bypasses and `route add -net <cidr> -interface <tun>`
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# for VPN routes.
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# Windows: not implemented in v1 (the section is parsed but the install is a logged no-op).
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[tunnel.os_routes]
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# Master switch. `false` falls back to the v1 user-space router (the `send_direct` path drops
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# DIRECT packets; kept intentionally as a fallback). Default: true.
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enabled = true
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# When `true`, every routing command is only logged (`would run: ...`) and not executed —
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# useful for testing the plan without root. Default: false.
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dry_run = false
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# Optional explicit IPv4 default gateway. When omitted, auto-detected (Linux:
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# `ip route show default`; macOS: `route -n get default`).
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# gateway = "192.168.1.1"
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# Optional explicit egress interface name (e.g. "eth0" on Linux, "en0" on macOS). When omitted,
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# auto-detected alongside the gateway.
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# egress_iface = "en0"
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[mimicry]
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# Enable traffic padding to blend packet sizes into HTTPS buckets.
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padding = false
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[transport]
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# Fallback order tried left-to-right ("handover"): the first transport that connects wins. Aura's
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# own UDP transport is primary; TCP/443 and QUIC (HTTP/3 mimicry) are fallbacks for networks that
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# throttle or block plain UDP. Omitting this whole section uses ["udp","tcp","quic"] on 443/443/444.
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order = ["udp", "tcp", "quic"]
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# Per-transport server ports. The server IP comes from [client] server_addr above (its port there is
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# ignored). The UDP transport and QUIC both ride UDP, so udp_port and quic_port MUST differ; TCP may
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# reuse the UDP port number.
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udp_port = 443
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tcp_port = 443
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quic_port = 444
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# UDP: pad datagrams up to HTTPS size buckets to blur the on-wire size distribution.
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obfuscate = true
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# TCP: prepend a minimal HTTP/1.1 preamble (Host = [client] sni) so the open resembles plain HTTP.
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masquerade = true
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[transport.masks]
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# Daily protocol-mask rotation. When `true`, every day at 05:00 MSK (= 02:00 UTC) the client
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# derives a new (SNI, User-Agent, Server-header, padding-profile) tuple from
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# HKDF-SHA256(CA-fingerprint, MSK-date) and uses it for any subsequent connect — the server derives
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# the same tuple independently from the same CA fingerprint, so no wire coordination is needed.
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# Existing connections keep the mask they connected with. Default: true.
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# When `false`, the static values above ([client] sni, [transport] obfuscate, ...) are used as-is.
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enabled = true
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[transport.knock]
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# UDP port-knocking. Must match the server's setting. Default: false.
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enabled = false
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knock_secret_source = "ca_fingerprint"
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[transport.cover]
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# Idle-time cover traffic. Must match the server's setting. Default: false.
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enabled = false
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mean_interval_ms = 500
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jitter = 0.5
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# v3.1 / v3.2 multi-hop / onion routing: dial through 1 or 2 intermediate hops before reaching
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# the exit-server. When `enabled = true`, the client opens an OUTER Aura UDP connection to
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# `hops[0]` (the entry-relay), sends one ExtendBridge envelope describing the next hop, waits for
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# CircuitReady, then either dials the exit directly (2-hop) or repeats the ExtendBridge dance
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# through a middle relay (3-hop). The innermost handshake authenticates the EXIT's cert opaquely
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# — every relay sees only the next-hop address and AEAD ciphertext.
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#
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# v3.2 adds:
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# * per-hop client certificates (the entry-relay and the exit see DIFFERENT CNs — they cannot
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# link the two handshakes by identity), and
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# * cell padding (every packet is padded to a constant `cell_size` bytes before sending — the
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# exit MUST also enable `[server] cell_padding_for_circuit_clients = true` to decode), and
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# * 3-hop support (just add a third [[client.circuit.hops]] table).
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#
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# Omitting the section (or `enabled = false`) keeps the v2 single-hop dial path intact.
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#
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# --- v3.1 FLAT FORM (back-compat) — every hop uses the [pki] cert/key above (NOT unlinkable):
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# [client.circuit]
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# enabled = true
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# hops = ["198.51.100.5:443", "203.0.113.10:443"]
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#
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# --- v3.2 PER-HOP FORM — each hop has its own cert/key (identity-unlinkable):
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# [client.circuit]
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# enabled = true
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# cell_padding = true
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# cell_size = 1280
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#
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# [[client.circuit.hops]]
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# addr = "198.51.100.5:443"
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# cert_path = "~/.config/aura/circuit/entry.crt"
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# key_path = "~/.config/aura/circuit/entry.key"
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#
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# [[client.circuit.hops]] # OPTIONAL middle hop for a 3-hop circuit
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# addr = "198.51.100.99:443"
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# cert_path = "~/.config/aura/circuit/middle.crt"
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# key_path = "~/.config/aura/circuit/middle.key"
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#
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# [[client.circuit.hops]]
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# addr = "203.0.113.10:443"
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# cert_path = "~/.config/aura/circuit/exit.crt"
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# key_path = "~/.config/aura/circuit/exit.key"
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#
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# Generate per-hop certs in one command: `aura provision-client --circuit-hops 3 ...`
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