datumesh_core/
envelope.rs

1//! Response envelopes (5.5): the mesh's unsigned statement around a receipt.
2
3use crate::error::{err, Error, ErrorCode, Result};
4use crate::json::{self, Value};
5use crate::keys::Keys;
6use crate::lexical::{self, limits};
7use crate::receipt::Receipt;
8use crate::schema;
9
10/// The eight outcomes of 5.5.
11#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
12pub enum Outcome {
13    /// 200: the receipt answers the cell as of the requested `asof`: its `asof` is at or
14    /// before the requested one, and the mesh asserts it is the cell's latest version known
15    /// as of then.
16    Ok,
17    /// 200: as `Ok`, except that the mesh cannot assert the receipt is current; it serves the
18    /// last receipt it knows.
19    Stale,
20    /// 404: no receipt for this cell. With a `fault` (`spec-0.4.0`, see
21    /// [`check_envelope_extras`]), the cell is a computed cell whose evaluation faulted.
22    NotCovered,
23    /// 403: the requester may not receive this cell.
24    Unlicensed,
25    /// 402: available for the quoted price.
26    PaymentRequired,
27    /// 429: too many requests.
28    RateLimited,
29    /// 400: the cell URI does not parse.
30    BadRequest,
31    /// 5xx: the mesh failed.
32    Error,
33}
34
35impl Outcome {
36    /// The outcome as written in JSON.
37    pub const fn as_str(self) -> &'static str {
38        match self {
39            Outcome::Ok => "ok",
40            Outcome::Stale => "stale",
41            Outcome::NotCovered => "not_covered",
42            Outcome::Unlicensed => "unlicensed",
43            Outcome::PaymentRequired => "payment_required",
44            Outcome::RateLimited => "rate_limited",
45            Outcome::BadRequest => "bad_request",
46            Outcome::Error => "error",
47        }
48    }
49
50    fn from_name(s: &str) -> Option<Outcome> {
51        Some(match s {
52            "ok" => Outcome::Ok,
53            "stale" => Outcome::Stale,
54            "not_covered" => Outcome::NotCovered,
55            "unlicensed" => Outcome::Unlicensed,
56            "payment_required" => Outcome::PaymentRequired,
57            "rate_limited" => Outcome::RateLimited,
58            "bad_request" => Outcome::BadRequest,
59            "error" => Outcome::Error,
60            _ => return None,
61        })
62    }
63
64    /// Required and optional members besides `outcome`.
65    fn members(self) -> (&'static [&'static str], &'static [&'static str]) {
66        match self {
67            Outcome::Ok => (&["receipt", "trust"], &["superseded_by", "reason"]),
68            Outcome::Stale => (&["receipt", "trust", "age_seconds"], &["superseded_by", "reason"]),
69            Outcome::NotCovered => (&[], &["fault"]),
70            Outcome::Unlicensed => (&[], &[]),
71            Outcome::PaymentRequired => (&["quote"], &[]),
72            Outcome::RateLimited => (&["retry_after_seconds"], &[]),
73            Outcome::BadRequest | Outcome::Error => (&["error"], &[]),
74        }
75    }
76
77    fn status_ok(self, status: u16) -> bool {
78        match self {
79            Outcome::Ok | Outcome::Stale => status == 200,
80            Outcome::NotCovered => status == 404,
81            Outcome::Unlicensed => status == 403,
82            Outcome::PaymentRequired => status == 402,
83            Outcome::RateLimited => status == 429,
84            Outcome::BadRequest => status == 400,
85            Outcome::Error => (500..=599).contains(&status),
86        }
87    }
88}
89
90/// The mesh's trust label (5.5).
91#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
92pub enum Trust {
93    /// Signed by the namespace's host, with no inputs.
94    Primary,
95    /// The mesh says it recomputed the receipt.
96    Verified,
97    /// Neither.
98    Unverified,
99}
100
101impl Trust {
102    /// The label as written in JSON.
103    pub const fn as_str(self) -> &'static str {
104        match self {
105            Trust::Primary => "primary",
106            Trust::Verified => "verified",
107            Trust::Unverified => "unverified",
108        }
109    }
110}
111
112/// A formula evaluation fault (SPEC 5.5, 15.11; `spec-0.4.0`): the optional `fault` member
113/// of a `not_covered` envelope. The cell has no value, deterministically; this is not
114/// missing data. These are formula codes, not verification codes, so they are not
115/// [`ErrorCode`]s.
116#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
117#[non_exhaustive]
118pub enum Fault {
119    /// `E_FORMULA_DIV_ZERO`
120    DivZero,
121    /// `E_FORMULA_DOMAIN`
122    Domain,
123    /// `E_FORMULA_RANGE`
124    Range,
125    /// `E_FORMULA_EMPTY`
126    Empty,
127    /// `E_FORMULA_ABSENT`
128    Absent,
129    /// `E_FORMULA_FUTURE`
130    Future,
131}
132
133impl Fault {
134    /// Every fault an envelope may carry, in the order of SPEC 5.5.
135    pub const ALL: &'static [Fault] =
136        &[Fault::DivZero, Fault::Domain, Fault::Range, Fault::Empty, Fault::Absent, Fault::Future];
137
138    /// The code as written, e.g. `"E_FORMULA_DIV_ZERO"`.
139    pub const fn as_str(self) -> &'static str {
140        match self {
141            Fault::DivZero => "E_FORMULA_DIV_ZERO",
142            Fault::Domain => "E_FORMULA_DOMAIN",
143            Fault::Range => "E_FORMULA_RANGE",
144            Fault::Empty => "E_FORMULA_EMPTY",
145            Fault::Absent => "E_FORMULA_ABSENT",
146            Fault::Future => "E_FORMULA_FUTURE",
147        }
148    }
149
150    /// Looks a fault up by its code; `None` for any other text (a budget, a cycle or too deep
151    /// an evaluation is not a fault but the mesh's failure, SPEC 5.5).
152    pub fn from_code(text: &str) -> Option<Fault> {
153        Fault::ALL.iter().copied().find(|f| f.as_str() == text)
154    }
155}
156
157impl core::fmt::Display for Fault {
158    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
159        f.write_str(self.as_str())
160    }
161}
162
163/// The members of a checked envelope that [`Envelope`] has no field for, because they were
164/// added to SPEC 5.5 after it was frozen (0.3.0): see [`check_envelope_extras`].
165#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
166#[non_exhaustive]
167pub struct EnvelopeExtras {
168    /// The formula evaluation fault of a `not_covered` envelope (`spec-0.4.0`).
169    pub fault: Option<Fault>,
170}
171
172/// A price quote (`payment_required`).
173#[derive(Clone, Debug, PartialEq, Eq, Hash)]
174pub struct Quote {
175    /// A canonical decimal greater than zero.
176    pub amount: String,
177    /// A currency code from `units.md`.
178    pub currency: String,
179    /// Where to pay: an https URL.
180    pub authorise: String,
181}
182
183/// What the client asked for, for the binding of 5.5 step 5.
184#[derive(Clone, Debug, PartialEq, Eq, Hash)]
185pub struct Request {
186    cell_id: String,
187    asof: Option<String>,
188}
189
190/// A malformed request description (5.5 step 5): the caller's mistake, not an `E_*` code.
191#[derive(Clone, Debug, PartialEq, Eq, Hash)]
192pub struct InvalidRequest(String);
193
194impl core::fmt::Display for InvalidRequest {
195    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
196        write!(f, "invalid request: {}", self.0)
197    }
198}
199
200impl std::error::Error for InvalidRequest {}
201
202impl Request {
203    /// A request for the cell with id `cell_id` (64 lowercase hex digits) as of `asof` (an
204    /// instant) or now. Anything else is [`InvalidRequest`]: SPEC 5.5 makes a malformed
205    /// request the caller's error, reported outside the `E_*` codes.
206    pub fn new(cell_id: &str, asof: Option<&str>) -> core::result::Result<Request, InvalidRequest> {
207        if lexical::check_hex(cell_id, 64, "").is_err() {
208            return Err(InvalidRequest(format!("cell_id must be 64 lowercase hex digits: {cell_id:?}")));
209        }
210        if let Some(a) = asof {
211            if !lexical::is_instant(a) {
212                return Err(InvalidRequest(format!("asof must be an instant: {a:?}")));
213            }
214        }
215        Ok(Request { cell_id: cell_id.into(), asof: asof.map(String::from) })
216    }
217
218    /// The requested cell id.
219    pub fn cell_id(&self) -> &str {
220        &self.cell_id
221    }
222
223    /// The requested `asof`, if any.
224    pub fn asof(&self) -> Option<&str> {
225        self.asof.as_deref()
226    }
227}
228
229/// A checked envelope.
230#[derive(Clone, Debug, PartialEq, Eq)]
231pub struct Envelope {
232    /// The outcome.
233    pub outcome: Outcome,
234    /// The receipt (`ok`, `stale`), signature-valid and bound to the request.
235    pub receipt: Option<Receipt>,
236    /// The trust label (`ok`, `stale`).
237    pub trust: Option<Trust>,
238    /// Seconds since the mesh last confirmed the receipt (`stale`).
239    pub age_seconds: Option<u64>,
240    /// Hash of a newer receipt for the same cell.
241    pub superseded_by: Option<String>,
242    /// Why the receipt was superseded.
243    pub reason: Option<String>,
244    /// The quote (`payment_required`).
245    pub quote: Option<Quote>,
246    /// Seconds to wait (`rate_limited`).
247    pub retry_after_seconds: Option<u64>,
248    /// The failure code (`bad_request`, `error`).
249    pub error: Option<ErrorCode>,
250}
251
252const BAD_REQUEST_CODES: [ErrorCode; 15] = [
253    ErrorCode::ParseUri,
254    ErrorCode::CanonName,
255    ErrorCode::CanonArgName,
256    ErrorCode::CanonArgDuplicate,
257    ErrorCode::CanonArgOrder,
258    ErrorCode::CanonPercent,
259    ErrorCode::CanonType,
260    ErrorCode::CanonNumber,
261    ErrorCode::CanonDate,
262    ErrorCode::CanonInstant,
263    ErrorCode::CanonString,
264    ErrorCode::CanonBlob,
265    ErrorCode::CanonLimit,
266    ErrorCode::ArgUnknown,
267    ErrorCode::ArgMissing,
268];
269
270fn env_err<T>(path: &str, detail: impl Into<String>) -> Result<T> {
271    err(ErrorCode::Envelope, path, detail)
272}
273
274/// `0` or `[1-9][0-9]*`, at most 2^53 - 1, judged on the number's text.
275fn integer_member(v: &Value, path: &str) -> Result<u64> {
276    let Some(t) = v.as_number_text() else {
277        return env_err(path, "must be a non-negative integer");
278    };
279    let ok =
280        !t.is_empty() && t.bytes().all(|c| c.is_ascii_digit()) && (t == "0" || !t.starts_with('0')) && t.len() <= 16;
281    match (ok, t.parse::<u64>()) {
282        (true, Ok(x)) if x <= limits::BLOB_LENGTH => Ok(x),
283        _ => env_err(path, format!("must be written 0|[1-9][0-9]* and at most 2^53 - 1, not {t}")),
284    }
285}
286
287/// Checks a response envelope (5.5) in the order of its procedure: strict JSON, members,
288/// HTTP status, the receipt through step 6 of 10.1, the binding to `request`, then `trust`
289/// and `superseded_by`. Never touches the network. A `not_covered` envelope's `fault`
290/// (`spec-0.4.0`) is checked and accepted; [`check_envelope_extras`] also returns it.
291pub fn check_envelope(status: u16, body: &[u8], keys: &Keys, request: &Request) -> Result<Envelope> {
292    check_envelope_extras(status, body, keys, request).map(|(env, _)| env)
293}
294
295/// [`check_envelope`], also returning the members [`Envelope`] has no field for
296/// ([`EnvelopeExtras`]): the `fault` of a `not_covered` envelope, one of the six formula
297/// evaluation faults of SPEC 5.5 (`E_ENVELOPE` for any other value, or on another outcome).
298pub fn check_envelope_extras(
299    status: u16,
300    body: &[u8],
301    keys: &Keys,
302    request: &Request,
303) -> Result<(Envelope, EnvelopeExtras)> {
304    // 1.
305    let v = json::parse(body)?;
306    // 2.
307    let m = match &v {
308        Value::Object(m) if matches!(schema::opt(m, "outcome"), Some(Value::String(_))) => m,
309        _ => return env_err("$", "an envelope is an object with a string outcome"),
310    };
311    let oname = schema::get(m, "outcome").as_str().unwrap_or("");
312    let Some(outcome) = Outcome::from_name(oname) else {
313        return env_err("$.outcome", format!("unknown outcome {oname:?}"));
314    };
315    let (req, optional) = outcome.members();
316    let mut allowed: Vec<&str> = vec!["outcome"];
317    allowed.extend_from_slice(req);
318    schema::exact(m, &allowed, optional, "$", ErrorCode::Envelope)?;
319    let mut env = Envelope {
320        outcome,
321        receipt: None,
322        trust: None,
323        age_seconds: None,
324        superseded_by: None,
325        reason: None,
326        quote: None,
327        retry_after_seconds: None,
328        error: None,
329    };
330    let receipt_v = schema::opt(m, "receipt");
331    if let Some(r) = receipt_v {
332        if !matches!(r, Value::Object(_)) {
333            return env_err("$.receipt", "receipt is a receipt object");
334        }
335    }
336    if let Some(t) = schema::opt(m, "trust") {
337        env.trust = Some(match t.as_str() {
338            Some("primary") => Trust::Primary,
339            Some("verified") => Trust::Verified,
340            Some("unverified") => Trust::Unverified,
341            _ => return env_err("$.trust", "trust is primary, verified or unverified"),
342        });
343    }
344    if let Some(a) = schema::opt(m, "age_seconds") {
345        env.age_seconds = Some(integer_member(a, "$.age_seconds")?);
346    }
347    if let Some(a) = schema::opt(m, "retry_after_seconds") {
348        env.retry_after_seconds = Some(integer_member(a, "$.retry_after_seconds")?);
349    }
350    if let Some(s) = schema::opt(m, "superseded_by") {
351        let s = s.as_str().unwrap_or("");
352        lexical::check_hex(s, 64, "$.superseded_by").map_err(|e| e.recode(ErrorCode::Envelope))?;
353        env.superseded_by = Some(s.into());
354    }
355    if let Some(r) = schema::opt(m, "reason") {
356        let Some(r) = r.as_str() else { return env_err("$.reason", "reason must be a string") };
357        if schema::opt(m, "superseded_by").is_none() {
358            return env_err("$.reason", "reason is only present with superseded_by");
359        }
360        lexical::check_text(r, limits::SUMMARY, false, "$.reason").map_err(|e| e.recode(ErrorCode::Envelope))?;
361        if r.is_empty() {
362            return env_err("$.reason", "reason must not be empty");
363        }
364        env.reason = Some(r.into());
365    }
366    if let Some(q) = schema::opt(m, "quote") {
367        env.quote = Some(quote(q)?);
368    }
369    if let Some(e) = schema::opt(m, "error") {
370        let code = e.as_str().and_then(ErrorCode::from_code);
371        let ok = match (outcome, code) {
372            (Outcome::BadRequest, Some(c)) => BAD_REQUEST_CODES.contains(&c),
373            // Any code of 10.2 but the client's E_ENVELOPE; E_EVAL_UNAVAILABLE included since
374            // spec-0.3.0.
375            (_, Some(c)) => c != ErrorCode::Envelope,
376            (_, None) => false,
377        };
378        if !ok {
379            return env_err("$.error", format!("{e:?} is not a code this outcome can carry"));
380        }
381        env.error = code;
382    }
383    let mut extras = EnvelopeExtras::default();
384    if let Some(f) = schema::opt(m, "fault") {
385        let Some(fault) = f.as_str().and_then(Fault::from_code) else {
386            return env_err("$.fault", format!("{f:?} is not a formula evaluation fault"));
387        };
388        extras.fault = Some(fault);
389    }
390    // 3.
391    if !outcome.status_ok(status) {
392        return env_err("$.outcome", format!("status {status} does not match outcome {}", outcome.as_str()));
393    }
394    let Some(rv) = receipt_v else { return Ok((env, extras)) };
395    // 4.
396    let r = crate::verify::signature_valid_value(rv, keys).map_err(|(e, _)| {
397        let inner = e.path().strip_prefix('$').unwrap_or(e.path());
398        Error::new(e.code(), format!("$.receipt{inner}"), e.detail())
399    })?;
400    // 5.
401    if r.cell().id() != request.cell_id {
402        return env_err("$.receipt.cell", "the receipt is for another cell than the one requested");
403    }
404    if let Some(asked) = &request.asof {
405        // D31 (revised in spec-0.3.0): at or before the requested asof, for ok and stale
406        // alike; instants are canonical, so text order is time order.
407        if r.asof() > asked.as_str() {
408            return env_err("$.receipt.asof", "the receipt's asof is after the requested asof");
409        }
410    }
411    // 6.
412    let primary = r.signer_host() == lexical::host_of(&r.cell().ns) && r.inputs().is_empty();
413    if (env.trust == Some(Trust::Primary)) != primary {
414        return env_err(
415            "$.trust",
416            if primary { "a primary receipt is labelled primary" } else { "the receipt is not primary" },
417        );
418    }
419    if env.superseded_by.as_deref() == Some(r.hash()) {
420        return env_err("$.superseded_by", "a receipt cannot supersede itself");
421    }
422    env.receipt = Some(r);
423    Ok((env, extras))
424}
425
426fn quote(q: &Value) -> Result<Quote> {
427    let m = schema::object_or(q, "$.quote", ErrorCode::Envelope, "quote")?;
428    schema::exact(m, &["amount", "authorise", "currency"], &[], "$.quote", ErrorCode::Envelope)?;
429    let amount = schema::string_or(m, "amount", "$.quote", ErrorCode::Envelope)?;
430    let authorise = schema::string_or(m, "authorise", "$.quote", ErrorCode::Envelope)?;
431    let currency = schema::string_or(m, "currency", "$.quote", ErrorCode::Envelope)?;
432    if lexical::check_number(amount, "").is_err() || amount.starts_with('-') || amount == "0" {
433        return env_err("$.quote.amount", "amount is a canonical decimal greater than zero");
434    }
435    let url_ok = authorise
436        .strip_prefix("https://")
437        .is_some_and(|r| !r.is_empty() && r.bytes().all(|c| (0x21..=0x7E).contains(&c)))
438        && authorise.len() <= limits::LICENCE_URL;
439    if !url_ok {
440        return env_err("$.quote.authorise", "authorise is an https URL");
441    }
442    if !lexical::is_currency(currency) {
443        return env_err("$.quote.currency", "currency is a currency code from units.md");
444    }
445    Ok(Quote { amount: amount.into(), currency: currency.into(), authorise: authorise.into() })
446}
datumesh_core/envelope.rs

datumesh_core/
envelope.rs
