ic_memory/
stable_cell.rs

1use crate::{LedgerCommitStore, constants::WASM_PAGE_SIZE_BYTES};
2use ic_stable_structures::{Memory, Storable, storable::Bound};
3use serde::{Deserialize, Serialize};
4use std::borrow::Cow;
5use thiserror::Error;
6
7/// Stable-cell magic prefix written by `ic-stable-structures::Cell`.
8pub const STABLE_CELL_MAGIC: &[u8; 3] = b"SCL";
9/// Stable-cell layout version supported by this adapter.
10pub const STABLE_CELL_LAYOUT_VERSION: u8 = 1;
11/// Stable-cell header byte length.
12pub const STABLE_CELL_HEADER_SIZE: usize = 8;
13/// Byte offset where the stable-cell value payload starts.
14pub const STABLE_CELL_VALUE_OFFSET: u64 = 8;
15
16///
17/// StableCellLedgerRecord
18///
19/// `ic-stable-structures::Cell` record containing an `ic-memory` allocation
20/// ledger commit store.
21///
22/// This is a substrate adapter DTO. It owns no framework policy and does not
23/// open application allocations.
24///
25
26#[derive(Clone, Debug, Default, Deserialize, Eq, PartialEq, Serialize)]
27#[serde(deny_unknown_fields)]
28pub struct StableCellLedgerRecord {
29    store: LedgerCommitStore,
30}
31
32impl StableCellLedgerRecord {
33    /// Construct a record from a commit store.
34    #[must_use]
35    pub const fn new(store: LedgerCommitStore) -> Self {
36        Self { store }
37    }
38
39    /// Borrow the embedded commit store.
40    #[must_use]
41    pub const fn store(&self) -> &LedgerCommitStore {
42        &self.store
43    }
44
45    /// Mutably borrow the embedded commit store.
46    pub const fn store_mut(&mut self) -> &mut LedgerCommitStore {
47        &mut self.store
48    }
49
50    /// Consume this record and return the embedded commit store.
51    #[must_use]
52    pub fn into_store(self) -> LedgerCommitStore {
53        self.store
54    }
55
56    /// Measure the current encoded record without allocating a payload buffer.
57    pub(crate) fn encoded_size(&self) -> usize {
58        let mut writer = CountingWriter(0);
59        encode_record(self, &mut writer);
60        writer.0
61    }
62}
63
64impl Storable for StableCellLedgerRecord {
65    const BOUND: Bound = Bound::Unbounded;
66
67    fn to_bytes(&self) -> Cow<'_, [u8]> {
68        Cow::Owned(serialize_record(self))
69    }
70
71    fn into_bytes(self) -> Vec<u8> {
72        serialize_record(&self)
73    }
74
75    fn from_bytes(bytes: Cow<'_, [u8]>) -> Self {
76        decode_stable_cell_ledger_record(&bytes).unwrap_or_else(|err| {
77            panic!("StableCellLedgerRecord deserialize failed: {err}");
78        })
79    }
80}
81
82///
83/// StableCellPayloadError
84///
85/// Stable-cell payload decode failure.
86///
87
88#[non_exhaustive]
89#[derive(Clone, Debug, Eq, Error, PartialEq)]
90pub enum StableCellPayloadError {
91    /// Declared bytes exceed the current recovery ceiling before allocation.
92    #[error("stable-cell ledger payload length {value_len} exceeds recovery limit")]
93    TooLarge { value_len: u64 },
94    /// Memory contents do not start with the stable-cell marker.
95    #[error("memory is not an ic-stable-structures Cell")]
96    NotStableCell,
97    /// Stable-cell layout version does not match the adapter's current shape.
98    #[error("unexpected stable-cell layout version {version}")]
99    UnexpectedLayoutVersion {
100        /// Observed stable-cell version.
101        version: u8,
102    },
103    /// Stable-cell header length does not fit inside the memory.
104    #[error("stable-cell payload length {value_len} exceeds available bytes {available_bytes}")]
105    InvalidLength {
106        /// Encoded value length.
107        value_len: u64,
108        /// Available payload bytes in memory.
109        available_bytes: u64,
110    },
111}
112
113///
114/// StableCellLedgerError
115///
116/// Stable-cell ledger record validation failure.
117#[non_exhaustive]
118#[derive(Debug, Error)]
119pub enum StableCellLedgerError {
120    /// Stable-cell envelope is corrupt or unexpected.
121    #[error(transparent)]
122    Payload(#[from] StableCellPayloadError),
123    /// Stable-cell value bytes are not a valid ledger record.
124    #[error("stable-cell ledger record decode failed: {0}")]
125    Record(#[source] ciborium::de::Error<std::io::Error>),
126}
127
128/// Decode the raw value payload from an `ic-stable-structures::Cell` memory.
129///
130/// This helper is intentionally narrow: it recognizes the physical stable-cell
131/// envelope and returns the value bytes. It does not deserialize those bytes or
132/// decide whether they represent a valid allocation ledger.
133pub fn decode_stable_cell_payload<M: Memory>(
134    memory: &M,
135) -> Result<Vec<u8>, StableCellPayloadError> {
136    if memory.size() == 0 {
137        return Err(StableCellPayloadError::NotStableCell);
138    }
139
140    let mut header = [0; STABLE_CELL_HEADER_SIZE];
141    memory.read(0, &mut header);
142    if &header[0..3] != STABLE_CELL_MAGIC {
143        return Err(StableCellPayloadError::NotStableCell);
144    }
145    if header[3] != STABLE_CELL_LAYOUT_VERSION {
146        return Err(StableCellPayloadError::UnexpectedLayoutVersion { version: header[3] });
147    }
148
149    let value_len = u64::from(u32::from_le_bytes([
150        header[4], header[5], header[6], header[7],
151    ]));
152    let available_bytes = memory.size().saturating_mul(WASM_PAGE_SIZE_BYTES);
153    let payload_capacity = available_bytes.saturating_sub(STABLE_CELL_VALUE_OFFSET);
154    if value_len > payload_capacity {
155        return Err(StableCellPayloadError::InvalidLength {
156            value_len,
157            available_bytes: payload_capacity,
158        });
159    }
160    if value_len > crate::constants::MAX_LEDGER_RECORD_BYTES as u64 {
161        return Err(StableCellPayloadError::TooLarge { value_len });
162    }
163    #[expect(
164        clippy::cast_possible_truncation,
165        reason = "the admitted recovery ceiling is representable as usize"
166    )]
167    let value_len = value_len as usize;
168
169    let mut bytes = vec![0; value_len];
170    memory.read(STABLE_CELL_VALUE_OFFSET, &mut bytes);
171    Ok(bytes)
172}
173
174/// Decode a `StableCellLedgerRecord` from stable-cell value bytes.
175///
176/// This decodes only the cell value payload, not the enclosing stable-cell
177/// header. Use [`decode_stable_cell_payload`] first when inspecting raw stable
178/// memory.
179///
180/// The returned record is decoded DTO state, not authority. Recover through the
181/// embedded [`LedgerCommitStore`] before trusting any ledger payload.
182pub fn decode_stable_cell_ledger_record(
183    bytes: &[u8],
184) -> Result<StableCellLedgerRecord, ciborium::de::Error<std::io::Error>> {
185    crate::cbor::from_slice_exact(bytes)
186}
187
188pub fn decode_stable_cell_ledger_record_from_memory<M: Memory>(
189    memory: &M,
190) -> Result<StableCellLedgerRecord, StableCellLedgerError> {
191    if memory.size() == 0 {
192        return Ok(StableCellLedgerRecord::default());
193    }
194
195    let payload = decode_stable_cell_payload(memory)?;
196    decode_stable_cell_ledger_record(&payload).map_err(StableCellLedgerError::Record)
197}
198
199/// Validate an existing stable-cell ledger record before opening it with
200/// `ic-stable-structures::Cell`.
201///
202/// `Cell::init` decodes the existing value through [`Storable::from_bytes`].
203/// That trait is panic-based, so the runtime preflights the raw memory with
204/// this fallible helper first. Empty memory is treated as uninitialized and is
205/// safe for `Cell::init` to create.
206pub fn validate_stable_cell_ledger_memory<M: Memory>(
207    memory: &M,
208) -> Result<(), StableCellLedgerError> {
209    decode_stable_cell_ledger_record_from_memory(memory)?;
210    Ok(())
211}
212
213fn serialize_record(record: &StableCellLedgerRecord) -> Vec<u8> {
214    let mut bytes = Vec::new();
215    encode_record(record, &mut bytes);
216    bytes
217}
218
219fn encode_record(record: &StableCellLedgerRecord, writer: impl std::io::Write) {
220    ciborium::into_writer(record, writer).unwrap_or_else(|err| {
221        panic!("StableCellLedgerRecord serialize failed: {err}");
222    });
223}
224
225struct CountingWriter(usize);
226
227impl std::io::Write for CountingWriter {
228    fn write(&mut self, bytes: &[u8]) -> std::io::Result<usize> {
229        self.0 = self
230            .0
231            .checked_add(bytes.len())
232            .ok_or_else(|| std::io::Error::other("encoded record length overflow"))?;
233        Ok(bytes.len())
234    }
235
236    fn flush(&mut self) -> std::io::Result<()> {
237        Ok(())
238    }
239}
240
241#[cfg(test)]
242mod tests {
243    use super::*;
244    use crate::test_cbor::hex_fixture;
245    use ic_stable_structures::{Cell, VectorMemory};
246
247    #[test]
248    fn stable_cell_ledger_record_round_trips_through_cell() {
249        let memory = VectorMemory::default();
250        let record = StableCellLedgerRecord::default();
251        let cell = Cell::init(memory.clone(), record.clone());
252
253        assert_eq!(cell.get(), &record);
254        let payload = decode_stable_cell_payload(&memory).expect("decode stable cell payload");
255        let decoded = StableCellLedgerRecord::from_bytes(Cow::Owned(payload));
256        assert_eq!(decoded, record);
257    }
258
259    #[test]
260    fn current_stable_cell_record_fixture_recovers() {
261        let bytes = hex_fixture(include_str!(
262            "../fixtures/current/stable_cell_record.cbor.hex"
263        ));
264        let record = decode_stable_cell_ledger_record(&bytes).expect("stable-cell fixture");
265
266        assert_eq!(record.encoded_size(), bytes.len());
267        assert_eq!(
268            bytes,
269            crate::test_cbor::to_vec(&record).expect("re-encoded stable-cell fixture")
270        );
271        assert_eq!(
272            record
273                .store()
274                .recover()
275                .expect("fixture store recovers")
276                .current_generation(),
277            1
278        );
279    }
280
281    #[test]
282    fn malformed_payload_bytes_fail_closed_without_mutating_memory() {
283        let original = hex_fixture(include_str!(
284            "../fixtures/current/stable_cell_record.cbor.hex"
285        ));
286        let start = original
287            .windows(8)
288            .position(|bytes| bytes == b"\x67payload")
289            .unwrap()
290            + 8;
291        let oversized = u32::try_from(crate::constants::MAX_COMMITTED_PAYLOAD_BYTES + 1).unwrap();
292        let mut cases = Vec::new();
293        for replacement in [
294            vec![0x5a, 0xff, 0xff, 0xff, 0xff],
295            vec![0x5f, 0xff],
296            vec![0x41],
297            vec![0xff],
298        ] {
299            let mut bytes = original[..start].to_vec();
300            bytes.extend(replacement);
301            cases.push(bytes);
302        }
303        let mut bytes = original[..start].to_vec();
304        bytes.push(0x5a);
305        bytes.extend_from_slice(&oversized.to_be_bytes());
306        bytes.resize(bytes.len() + oversized as usize, 0);
307        cases.push(bytes);
308        for bytes in cases {
309            let memory = VectorMemory::default();
310            let pages = (bytes.len() + STABLE_CELL_HEADER_SIZE).div_ceil(65_536);
311            memory.grow(pages as u64);
312            memory.write(0, STABLE_CELL_MAGIC);
313            memory.write(3, &[STABLE_CELL_LAYOUT_VERSION]);
314            memory.write(4, &u32::try_from(bytes.len()).unwrap().to_le_bytes());
315            memory.write(STABLE_CELL_VALUE_OFFSET, &bytes);
316            let before = memory.borrow().clone();
317            for _ in 0..2 {
318                assert!(matches!(
319                    decode_stable_cell_ledger_record_from_memory(&memory),
320                    Err(StableCellLedgerError::Record(_))
321                ));
322                assert!(matches!(
323                    validate_stable_cell_ledger_memory(&memory),
324                    Err(StableCellLedgerError::Record(_))
325                ));
326            }
327            assert_eq!(*memory.borrow(), before);
328        }
329    }
330
331    #[test]
332    fn stable_cell_ledger_record_rejects_trailing_bytes() {
333        let mut bytes = serialize_record(&StableCellLedgerRecord::default());
334        bytes.push(0);
335
336        let err =
337            decode_stable_cell_ledger_record(&bytes).expect_err("trailing bytes must fail closed");
338
339        assert!(err.to_string().contains("trailing bytes"));
340    }
341
342    #[test]
343    fn stable_cell_ledger_record_rejects_unknown_top_level_fields() {
344        use crate::test_cbor::Value;
345
346        let map = vec![
347            (
348                Value::Text("store".to_string()),
349                crate::test_cbor::to_value(LedgerCommitStore::default()).expect("store value"),
350            ),
351            (Value::Text("future_field".to_string()), Value::Bool(true)),
352        ];
353        let bytes = crate::test_cbor::to_vec(&Value::Map(map)).expect("unknown-field stable cell");
354
355        let err = decode_stable_cell_ledger_record(&bytes)
356            .expect_err("unknown stable-cell record field must fail closed");
357
358        assert!(err.to_string().contains("future_field"));
359    }
360
361    #[test]
362    fn stable_cell_ledger_record_requires_both_commit_slot_fields() {
363        use crate::test_cbor::Value;
364
365        for (missing, present) in [("slot0", "slot1"), ("slot1", "slot0")] {
366            let physical = vec![(Value::Text(present.to_string()), Value::Null)];
367            let store = vec![(Value::Text("physical".to_string()), Value::Map(physical))];
368            let record = vec![(Value::Text("store".to_string()), Value::Map(store))];
369            let bytes = crate::test_cbor::to_vec(&Value::Map(record)).expect("record bytes");
370
371            let err = decode_stable_cell_ledger_record(&bytes)
372                .expect_err("missing commit slot must fail closed");
373
374            assert!(err.to_string().contains(missing));
375        }
376    }
377
378    #[test]
379    fn stable_cell_payload_rejects_non_cell_memory() {
380        let memory = VectorMemory::default();
381        memory.grow(1);
382        memory.write(0, b"BAD");
383
384        assert_eq!(
385            decode_stable_cell_payload(&memory),
386            Err(StableCellPayloadError::NotStableCell)
387        );
388    }
389
390    #[test]
391    fn stable_cell_payload_rejects_empty_memory_without_panic() {
392        let memory = VectorMemory::default();
393
394        assert_eq!(
395            decode_stable_cell_payload(&memory),
396            Err(StableCellPayloadError::NotStableCell)
397        );
398    }
399
400    #[test]
401    fn stable_cell_ledger_preflight_classifies_bad_record_without_panic() {
402        let memory = VectorMemory::default();
403        memory.grow(1);
404        memory.write(0, STABLE_CELL_MAGIC);
405        memory.write(3, &[STABLE_CELL_LAYOUT_VERSION]);
406        memory.write(4, &1_u32.to_le_bytes());
407        memory.write(STABLE_CELL_VALUE_OFFSET, &[0xff]);
408
409        let err =
410            validate_stable_cell_ledger_memory(&memory).expect_err("bad record must be classified");
411
412        assert!(matches!(err, StableCellLedgerError::Record(_)));
413    }
414    #[test]
415    fn oversized_cell_length_is_rejected_before_payload_read() {
416        struct HeaderOnly {
417            value_len: u32,
418            pages: u64,
419        }
420        impl Memory for HeaderOnly {
421            fn size(&self) -> u64 {
422                self.pages
423            }
424            fn grow(&self, _: u64) -> i64 {
425                panic!("must not grow")
426            }
427            fn write(&self, _: u64, _: &[u8]) {
428                panic!("must not write")
429            }
430            fn read(&self, offset: u64, bytes: &mut [u8]) {
431                assert_eq!(offset, 0);
432                assert_eq!(bytes.len(), STABLE_CELL_HEADER_SIZE);
433                bytes[..4].copy_from_slice(b"SCL\x01");
434                bytes[4..8].copy_from_slice(&self.value_len.to_le_bytes());
435            }
436        }
437        for value_len in [
438            u32::try_from(crate::constants::MAX_LEDGER_RECORD_BYTES + 1).unwrap(),
439            u32::MAX,
440        ] {
441            // The advertised value fits the backing, but exceeds the recovery ceiling.
442            let memory = HeaderOnly {
443                value_len,
444                pages: 65_537,
445            };
446            assert!(matches!(
447                decode_stable_cell_ledger_record_from_memory(&memory),
448                Err(StableCellLedgerError::Payload(StableCellPayloadError::TooLarge {
449                    value_len: rejected,
450                })) if rejected == u64::from(value_len)
451            ));
452            // Physical-capacity rejection keeps precedence when both checks fail.
453            let memory = HeaderOnly {
454                value_len,
455                pages: 1,
456            };
457            assert_eq!(
458                decode_stable_cell_payload(&memory),
459                Err(StableCellPayloadError::InvalidLength {
460                    value_len: u64::from(value_len),
461                    available_bytes: WASM_PAGE_SIZE_BYTES - STABLE_CELL_VALUE_OFFSET,
462                })
463            );
464        }
465    }
466
467    #[test]
468    fn hostile_cbor_is_rejected_on_production_record_decode() {
469        let huge_array = [0x9b, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff];
470        let huge_string = [0x7b, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff];
471        let mut nested = vec![0x81; crate::constants::MAX_LEDGER_NESTING + 1];
472        nested.push(0);
473        for bytes in [&huge_array[..], &huge_string[..], &nested, &[0xa1], &[0xff]] {
474            assert!(decode_stable_cell_ledger_record(bytes).is_err());
475        }
476    }
477}
ic_memory/stable_cell.rs

ic_memory/
stable_cell.rs
