OXYGENHUB
# 17dc8de4fca8 oxygenhub / crates / hub / src / provenance.rs
5.9 KiB · Rust · last changed Flow: SLSA provenance for artifacts, in DSSE, that cosign verifies 19 days ago source blame history raw
1 
//! Provenance others can verify (oxygenhub#239): a Flow artifact's in-toto
2 
//! Statement with an SLSA provenance v1 predicate, in a DSSE envelope signed
3 
//! with the hub's Ed25519 key, as `cosign verify-blob-attestation` and other
4 
//! in-toto and SLSA verifiers read it. The runner signed the job's receipt
5 
//! with a key the hub holds no secret of; the hub checked that receipt when
6 
//! it kept it, and this envelope is the hub's statement of what the receipt
7 
//! says, in the shape the wider tools understand. `/.well-known/oxyhub-signing.pem`
8 
//! is the public key, as cosign's `--key` takes it.
9
10 
use crate::Shared;
11
12 
/// DSSE's payload type for in-toto statements.
13 
pub const PAYLOAD_TYPE: &str = "application/vnd.in-toto+json";
14
15 
/// What the statement says of one artifact.
16 
pub struct Subject<'a> {
17 
    /// The artifact's file name.
18 
    pub name: &'a str,
19 
    pub bytes: &'a [u8],
20 
    /// `owner/name` and the hub's URL of the run.
21 
    pub repo: &'a str,
22 
    pub run_url: &'a str,
23 
    pub bookmark: &'a str,
24 
    /// The state the run built, and the heads it is.
25 
    pub state: &'a str,
26 
    pub heads: &'a str,
27 
    pub pipeline_hash: &'a str,
28 
    pub job: &'a str,
29 
    /// The runner that ran it and signed its receipt.
30 
    pub runner: &'a str,
31 
    pub receipt_signer: &'a str,
32 
    pub receipt_attest: &'a str,
33 
    pub started_ms: Option<i64>,
34 
    pub finished_ms: Option<i64>,
35 
}
36
37 
/// The in-toto Statement v1 with an SLSA provenance v1 predicate.
38 
pub fn statement(base_url: &str, s: &Subject) -> serde_json::Value {
39 
    use sha2::Digest;
40 
    let sha256 = hex::encode(sha2::Sha256::digest(s.bytes));
41 
    let when = |ms: Option<i64>| {
42 
        ms.and_then(|t| time::OffsetDateTime::from_unix_timestamp_nanos(t as i128 * 1_000_000).ok())
43 
            .and_then(|t| t.format(&time::format_description::well_known::Rfc3339).ok())
44 
    };
45 
    let mut metadata = serde_json::json!({ "invocationId": s.run_url });
46 
    if let Some(t) = when(s.started_ms) {
47 
        metadata["startedOn"] = t.into();
48 
    }
49 
    if let Some(t) = when(s.finished_ms) {
50 
        metadata["finishedOn"] = t.into();
51 
    }
52 
    serde_json::json!({
53 
        "_type": "https://in-toto.io/Statement/v1",
54 
        "subject": [{ "name": s.name, "digest": { "sha256": sha256, "blake3": blake3::hash(s.bytes).to_hex().to_string() } }],
55 
        "predicateType": "https://slsa.dev/provenance/v1",
56 
        "predicate": {
57 
            "buildDefinition": {
58 
                "buildType": format!("{base_url}/oxygenflow/job/v1"),
59 
                "externalParameters": {
60 
                    "repository": format!("{base_url}/{}", s.repo),
61 
                    "bookmark": s.bookmark,
62 
                    "job": s.job,
63 
                    "pipeline": s.pipeline_hash,
64 
                },
65 
                "resolvedDependencies": [{
66 
                    "uri": format!("{base_url}/{}", s.repo),
67 
                    "digest": { "oxygen-state": s.state },
68 
                    "annotations": { "heads": s.heads },
69 
                }],
70 
            },
71 
            "runDetails": {
72 
                "builder": {
73 
                    "id": format!("{base_url}/oxygenflow/runner/{}", s.runner),
74 
                },
75 
                "metadata": metadata,
76 
                "byproducts": [{
77 
                    "name": "oxygen-receipt",
78 
                    "digest": { "oxygen-attestation": s.receipt_attest },
79 
                    "annotations": { "signedBy": s.receipt_signer },
80 
                }],
81 
            },
82 
        },
83 
    })
84 
}
85
86 
/// DSSE's pre-authentication encoding: what the signature covers.
87 
pub fn pae(payload_type: &str, payload: &[u8]) -> Vec<u8> {
88 
    let mut out = format!("DSSEv1 {} {} {} ", payload_type.len(), payload_type, payload.len()).into_bytes();
89 
    out.extend_from_slice(payload);
90 
    out
91 
}
92
93 
/// `statement` in a DSSE envelope signed with the hub's key.
94 
pub fn envelope(app: &Shared, statement: &serde_json::Value) -> anyhow::Result<serde_json::Value> {
95 
    let payload = serde_json::to_vec(statement)?;
96 
    let (key, secret) = crate::keys::load_secret(&app.config.keys_dir())?;
97 
    let pair = ring::signature::Ed25519KeyPair::from_seed_unchecked(&secret.ed_seed)
98 
        .map_err(|_| anyhow::anyhow!("the hub's key is not an Ed25519 seed"))?;
99 
    let sig = pair.sign(&pae(PAYLOAD_TYPE, &payload));
100 
    Ok(serde_json::json!({
101 
        "payloadType": PAYLOAD_TYPE,
102 
        "payload": base64(&payload),
103 
        "signatures": [{ "keyid": key.to_hex(), "sig": base64(sig.as_ref()) }],
104 
    }))
105 
}
106
107 
/// The hub's Ed25519 public key as a PEM SubjectPublicKeyInfo.
108 
pub fn public_pem(app: &Shared) -> String {
109 
    // SEQUENCE { SEQUENCE { OID 1.3.101.112 }, BIT STRING { key } }
110 
    let mut der = vec![0x30, 0x2a, 0x30, 0x05, 0x06, 0x03, 0x2b, 0x65, 0x70, 0x03, 0x21, 0x00];
111 
    der.extend_from_slice(&app.hub_key.identity.ed25519_pk);
112 
    let body = base64(&der);
113 
    format!("-----BEGIN PUBLIC KEY-----\n{body}\n-----END PUBLIC KEY-----\n")
114 
}
115
116 
/// Standard base64 with padding, as DSSE and PEM use.
117 
pub fn base64(bytes: &[u8]) -> String {
118 
    const T: &[u8; 64] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
119 
    let mut out = String::with_capacity(bytes.len().div_ceil(3) * 4);
120 
    for chunk in bytes.chunks(3) {
121 
        let n = chunk.iter().fold(0u32, |acc, b| (acc << 8) | *b as u32) << (8 * (3 - chunk.len()));
122 
        for i in 0..4 {
123 
            if i <= chunk.len() {
124 
                out.push(T[((n >> (18 - 6 * i)) & 63) as usize] as char);
125 
            } else {
126 
                out.push('=');
127 
            }
128 
        }
129 
    }
130 
    out
131 
}
132
133 
#[cfg(test)]
134 
mod tests {
135 
    #[test]
136 
    fn pae_and_base64_are_the_specs() {
137 
        // DSSE's own example: PAE("http://example.com/HelloWorld", "hello world").
138 
        assert_eq!(
139 
            super::pae("http://example.com/HelloWorld", b"hello world"),
140 
            b"DSSEv1 29 http://example.com/HelloWorld 11 hello world".to_vec()
141 
        );
142 
        assert_eq!(super::base64(b"f"), "Zg==");
143 
        assert_eq!(super::base64(b"fo"), "Zm8=");
144 
        assert_eq!(super::base64(b"foo"), "Zm9v");
145 
        assert_eq!(super::base64(b"foobar"), "Zm9vYmFy");
146 
    }
147 
}