proof.rs 95.9%

70 of 73 lines run, 21 of 29 functions · run #5 on main · run missed

//! Signed requests and the proofs events carry (spec §8.5, §9.5).
//!
//! A principal signs `"spectra1 request " || method || 0x00 || BLAKE3(body)
//! || time (8 bytes) || nonce (16 bytes)` with its key, through `oxy-core`'s
//! challenge signing. The signature, with what it covered, is the proof
//! kept on every event the request causes, so a verifier can check later,
//! from the ledger alone, which key asked for it.
//!
//! The CLI, writing to the ledger itself, signs with `method = "cli"` and
//! `body` = the event's canonical payload, so its proof also binds the
//! event's content.

use crate::keys::KeyPair;
use oxy_core::cbor::{self, Value};
use oxy_core::identity::{Identity, Signature};
use rand::RngCore;

/// How far a request's time may be from the server's clock (spec §8.5).
pub const WINDOW_MS: u64 = 5 * 60 * 1000;

/// A signature with everything it covered except the body itself.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Proof {
    pub sig: Signature,
    pub method: String,
    pub body_hash: [u8; 32],
    pub time_ms: u64,
    pub nonce: [u8; 16],
}

impl Proof {
    /// Sign `method` and `body` now with `pair`.
    pub fn sign(pair: &KeyPair, method: &str, body: &[u8]) -> Proof {
        let mut nonce = [0u8; 16];
        rand::rngs::OsRng.fill_bytes(&mut nonce);
        Proof::sign_at(pair, method, body, crate::ids::now_ms(), nonce)
    }

    pub fn sign_at(pair: &KeyPair, method: &str, body: &[u8], time_ms: u64, nonce: [u8; 16]) -> Proof {
        let body_hash = *blake3::hash(body).as_bytes();
        let sig = pair.sign(&message(method, &body_hash, time_ms, &nonce));
        Proof { sig, method: method.into(), body_hash, time_ms, nonce }
    }

    /// The signing key's KeyId.
    pub fn key(&self) -> [u8; 32] {
        self.sig.key.0
    }

    /// Check the signature against `identity` and, when given, the body.
    pub fn verify(&self, identity: &Identity, body: Option<&[u8]>) -> Result<(), String> {
        if let Some(b) = body {
            if *blake3::hash(b).as_bytes() != self.body_hash {
                return Err("the signature covers a different body".into());
            }
        }
        let msg = message(&self.method, &self.body_hash, self.time_ms, &self.nonce);
        oxy_core::identity::verify_challenge(identity, &self.sig, &msg).map_err(|e| format!("signature does not verify: {e}"))
    }

    pub fn encode(&self) -> Vec<u8> {
        cbor::encode(&Value::map([
            (0, self.sig.to_value()),
            (1, Value::Text(self.method.clone())),
            (2, Value::Bytes(self.body_hash.to_vec())),
            (3, Value::Uint(self.time_ms)),
            (4, Value::Bytes(self.nonce.to_vec())),
        ]))
    }

    pub fn decode(b: &[u8]) -> Result<Proof, String> {
        let v = cbor::decode(b).map_err(|e| format!("malformed proof: {e}"))?;
        let m = v.as_map().ok_or("malformed proof")?;
        let get = |k: u64| m.get(&k).ok_or_else(|| format!("proof lacks field {k}"));
        Ok(Proof {
            sig: Signature::from_value(get(0)?).map_err(|e| format!("malformed signature: {e}"))?,
            method: get(1)?.as_text().ok_or("proof method")?.to_string(),
            body_hash: get(2)?.as_bytes().and_then(|b| b.try_into().ok()).ok_or("proof body hash")?,
            time_ms: get(3)?.as_uint().ok_or("proof time")?,
            nonce: get(4)?.as_bytes().and_then(|b| b.try_into().ok()).ok_or("proof nonce")?,
        })
    }
}

/// `"spectra1 request " || method || 0 || body_hash || time || nonce`.
pub fn message(method: &str, body_hash: &[u8; 32], time_ms: u64, nonce: &[u8; 16]) -> Vec<u8> {
    let mut m = b"spectra1 request ".to_vec();
    m.extend_from_slice(method.as_bytes());
    m.push(0);
    m.extend_from_slice(body_hash);
    m.extend_from_slice(&time_ms.to_be_bytes());
    m.extend_from_slice(nonce);
    m
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn a_proof_round_trips_and_binds_key_method_body_and_time() {
        let a = KeyPair::generate("a", "");
        let b = KeyPair::generate("b", "");
        let p = Proof::sign(&a, "POST /mcp", b"{\"x\":1}");
        let q = Proof::decode(&p.encode()).unwrap();
        assert_eq!(p, q);
        q.verify(&a.identity, Some(b"{\"x\":1}")).unwrap();
        assert!(q.verify(&a.identity, Some(b"{\"x\":2}")).is_err(), "another body");
        assert!(q.verify(&b.identity, None).is_err(), "another key");
        let mut r = q.clone();
        r.method = "POST /api".into();
        assert!(r.verify(&a.identity, None).is_err(), "another method");
        let mut t = q.clone();
        t.time_ms += 1;
        assert!(t.verify(&a.identity, None).is_err(), "another time");
    }
}

1		//! Signed requests and the proofs events carry (spec §8.5, §9.5).
2		//!
3		//! A principal signs `"spectra1 request " \|\| method \|\| 0x00 \|\| BLAKE3(body)
4		//! \|\| time (8 bytes) \|\| nonce (16 bytes)` with its key, through `oxy-core`'s
5		//! challenge signing. The signature, with what it covered, is the proof
6		//! kept on every event the request causes, so a verifier can check later,
7		//! from the ledger alone, which key asked for it.
8		//!
9		//! The CLI, writing to the ledger itself, signs with `method = "cli"` and
10		//! `body` = the event's canonical payload, so its proof also binds the
11		//! event's content.
12
13		use crate::keys::KeyPair;
14		use oxy_core::cbor::{self, Value};
15		use oxy_core::identity::{Identity, Signature};
16		use rand::RngCore;
17
18		/// How far a request's time may be from the server's clock (spec §8.5).
19		pub const WINDOW_MS: u64 = 5 * 60 * 1000;
20
21		/// A signature with everything it covered except the body itself.
22		#[derive(Clone, Debug, PartialEq, Eq)]
23		pub struct Proof {
24		pub sig: Signature,
25		pub method: String,
26		pub body_hash: [u8; 32],
27		pub time_ms: u64,
28		pub nonce: [u8; 16],
29		}
30
31		impl Proof {
32		/// Sign `method` and `body` now with `pair`.
33	59×	pub fn sign(pair: &KeyPair, method: &str, body: &[u8]) -> Proof {
34	59×	let mut nonce = [0u8; 16];
35	59×	rand::rngs::OsRng.fill_bytes(&mut nonce);
36	59×	Proof::sign_at(pair, method, body, crate::ids::now_ms(), nonce)
37	59×	}
38
39	60×	pub fn sign_at(pair: &KeyPair, method: &str, body: &[u8], time_ms: u64, nonce: [u8; 16]) -> Proof {
40	60×	let body_hash = *blake3::hash(body).as_bytes();
41	60×	let sig = pair.sign(&message(method, &body_hash, time_ms, &nonce));
42	60×	Proof { sig, method: method.into(), body_hash, time_ms, nonce }
43	60×	}
44
45		/// The signing key's KeyId.
46	102×	pub fn key(&self) -> [u8; 32] {
47	102×	self.sig.key.0
48	102×	}
49
50		/// Check the signature against `identity` and, when given, the body.
51	103×	pub fn verify(&self, identity: &Identity, body: Option<&[u8]>) -> Result<(), String> {
52	103×	if let Some(b) = body {
53	100×	if *blake3::hash(b).as_bytes() != self.body_hash {
54	3×	return Err("the signature covers a different body".into());
55	97×	}
56	3×	}
57	100×	let msg = message(&self.method, &self.body_hash, self.time_ms, &self.nonce);
58	100×	oxy_core::identity::verify_challenge(identity, &self.sig, &msg).map_err(\|e\| format!("signature does not verify: {e}"))
59	103×	}
60
61	55×	pub fn encode(&self) -> Vec<u8> {
62	55×	cbor::encode(&Value::map([
63	55×	(0, self.sig.to_value()),
64	55×	(1, Value::Text(self.method.clone())),
65	55×	(2, Value::Bytes(self.body_hash.to_vec())),
66	55×	(3, Value::Uint(self.time_ms)),
67	55×	(4, Value::Bytes(self.nonce.to_vec())),
68	55×	]))
69	55×	}
70
71	93×	pub fn decode(b: &[u8]) -> Result<Proof, String> {
72	93×	let v = cbor::decode(b).map_err(\|e\| format!("malformed proof: {e}"))?;
73	93×	let m = v.as_map().ok_or("malformed proof")?;
74	465×	let get = \|k: u64\| m.get(&k).ok_or_else(\|\| format!("proof lacks field {k}"));
75		Ok(Proof {
76	93×	sig: Signature::from_value(get(0)?).map_err(\|e\| format!("malformed signature: {e}"))?,
77	93×	method: get(1)?.as_text().ok_or("proof method")?.to_string(),
78	93×	body_hash: get(2)?.as_bytes().and_then(\|b\| b.try_into().ok()).ok_or("proof body hash")?,
79	93×	time_ms: get(3)?.as_uint().ok_or("proof time")?,
80	93×	nonce: get(4)?.as_bytes().and_then(\|b\| b.try_into().ok()).ok_or("proof nonce")?,
81		})
82	93×	}
83		}
84
85		/// `"spectra1 request " \|\| method \|\| 0 \|\| body_hash \|\| time \|\| nonce`.
86	160×	pub fn message(method: &str, body_hash: &[u8; 32], time_ms: u64, nonce: &[u8; 16]) -> Vec<u8> {
87	160×	let mut m = b"spectra1 request ".to_vec();
88	160×	m.extend_from_slice(method.as_bytes());
89	160×	m.push(0);
90	160×	m.extend_from_slice(body_hash);
91	160×	m.extend_from_slice(&time_ms.to_be_bytes());
92	160×	m.extend_from_slice(nonce);
93	160×	m
94	160×	}
95
96		#[cfg(test)]
97		mod tests {
98		use super::*;
99
100		#[test]
101	1×	fn a_proof_round_trips_and_binds_key_method_body_and_time() {
102	1×	let a = KeyPair::generate("a", "");
103	1×	let b = KeyPair::generate("b", "");
104	1×	let p = Proof::sign(&a, "POST /mcp", b"{\"x\":1}");
105	1×	let q = Proof::decode(&p.encode()).unwrap();
106	1×	assert_eq!(p, q);
107	1×	q.verify(&a.identity, Some(b"{\"x\":1}")).unwrap();
108	1×	assert!(q.verify(&a.identity, Some(b"{\"x\":2}")).is_err(), "another body");
109	1×	assert!(q.verify(&b.identity, None).is_err(), "another key");
110	1×	let mut r = q.clone();
111	1×	r.method = "POST /api".into();
112	1×	assert!(r.verify(&a.identity, None).is_err(), "another method");
113	1×	let mut t = q.clone();
114	1×	t.time_ms += 1;
115	1×	assert!(t.verify(&a.identity, None).is_err(), "another time");
116	1×	}
117		}

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