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
57impl Storable for StableCellLedgerRecord {
58    const BOUND: Bound = Bound::Unbounded;
59
60    fn to_bytes(&self) -> Cow<'_, [u8]> {
61        Cow::Owned(serialize_record(self))
62    }
63
64    fn into_bytes(self) -> Vec<u8> {
65        serialize_record(&self)
66    }
67
68    fn from_bytes(bytes: Cow<'_, [u8]>) -> Self {
69        decode_stable_cell_ledger_record(&bytes).unwrap_or_else(|err| {
70            panic!("StableCellLedgerRecord deserialize failed: {err}");
71        })
72    }
73}
74
75///
76/// StableCellPayloadError
77///
78/// Stable-cell payload decode failure.
79#[non_exhaustive]
80#[derive(Clone, Debug, Eq, Error, PartialEq)]
81pub enum StableCellPayloadError {
82    /// Declared bytes exceed the current recovery ceiling before allocation.
83    #[error("stable-cell ledger payload length {value_len} exceeds recovery limit")]
84    TooLarge { value_len: u64 },
85    /// Memory contents do not start with the stable-cell marker.
86    #[error("memory is not an ic-stable-structures Cell")]
87    NotStableCell,
88    /// Stable-cell layout version does not match the adapter's current shape.
89    #[error("unexpected stable-cell layout version {version}")]
90    UnexpectedLayoutVersion {
91        /// Observed stable-cell version.
92        version: u8,
93    },
94    /// Stable-cell header length does not fit inside the memory.
95    #[error("stable-cell payload length {value_len} exceeds available bytes {available_bytes}")]
96    InvalidLength {
97        /// Encoded value length.
98        value_len: u64,
99        /// Available payload bytes in memory.
100        available_bytes: u64,
101    },
102    /// Stable-cell length cannot be represented on the current host.
103    #[error("stable-cell payload length {value_len} cannot fit in usize")]
104    LengthOverflow {
105        /// Encoded value length.
106        value_len: u64,
107    },
108}
109
110///
111/// StableCellLedgerError
112///
113/// Stable-cell ledger record validation failure.
114#[non_exhaustive]
115#[derive(Debug, Error)]
116pub enum StableCellLedgerError {
117    /// Stable-cell envelope is corrupt or unexpected.
118    #[error(transparent)]
119    Payload(#[from] StableCellPayloadError),
120    /// Stable-cell value bytes are not a valid ledger record.
121    #[error("stable-cell ledger record decode failed")]
122    Record(#[source] ciborium::de::Error<std::io::Error>),
123}
124
125/// Decode the raw value payload from an `ic-stable-structures::Cell` memory.
126///
127/// This helper is intentionally narrow: it recognizes the physical stable-cell
128/// envelope and returns the value bytes. It does not deserialize those bytes or
129/// decide whether they represent a valid allocation ledger.
130pub fn decode_stable_cell_payload<M: Memory>(
131    memory: &M,
132) -> Result<Vec<u8>, StableCellPayloadError> {
133    if memory.size() == 0 {
134        return Err(StableCellPayloadError::NotStableCell);
135    }
136
137    let mut header = [0; STABLE_CELL_HEADER_SIZE];
138    memory.read(0, &mut header);
139    if &header[0..3] != STABLE_CELL_MAGIC {
140        return Err(StableCellPayloadError::NotStableCell);
141    }
142    if header[3] != STABLE_CELL_LAYOUT_VERSION {
143        return Err(StableCellPayloadError::UnexpectedLayoutVersion { version: header[3] });
144    }
145
146    let value_len = u64::from(u32::from_le_bytes([
147        header[4], header[5], header[6], header[7],
148    ]));
149    let available_bytes = memory.size().saturating_mul(WASM_PAGE_SIZE_BYTES);
150    let payload_capacity = available_bytes.saturating_sub(STABLE_CELL_VALUE_OFFSET);
151    if value_len > payload_capacity {
152        return Err(StableCellPayloadError::InvalidLength {
153            value_len,
154            available_bytes: payload_capacity,
155        });
156    }
157    if value_len > crate::constants::MAX_LEDGER_RECORD_BYTES as u64 {
158        return Err(StableCellPayloadError::TooLarge { value_len });
159    }
160    let value_len = usize::try_from(value_len)
161        .map_err(|_| StableCellPayloadError::LengthOverflow { value_len })?;
162
163    let mut bytes = vec![0; value_len];
164    memory.read(STABLE_CELL_VALUE_OFFSET, &mut bytes);
165    Ok(bytes)
166}
167
168/// Decode a `StableCellLedgerRecord` from stable-cell value bytes.
169///
170/// This decodes only the cell value payload, not the enclosing stable-cell
171/// header. Use [`decode_stable_cell_payload`] first when inspecting raw stable
172/// memory.
173///
174/// The returned record is decoded DTO state, not authority. Recover through the
175/// embedded [`LedgerCommitStore`] before trusting any ledger payload.
176pub fn decode_stable_cell_ledger_record(
177    bytes: &[u8],
178) -> Result<StableCellLedgerRecord, ciborium::de::Error<std::io::Error>> {
179    crate::cbor::from_slice_exact(bytes)
180}
181
182pub fn decode_stable_cell_ledger_record_from_memory<M: Memory>(
183    memory: &M,
184) -> Result<StableCellLedgerRecord, StableCellLedgerError> {
185    if memory.size() == 0 {
186        return Ok(StableCellLedgerRecord::default());
187    }
188
189    let payload = decode_stable_cell_payload(memory)?;
190    decode_stable_cell_ledger_record(&payload).map_err(StableCellLedgerError::Record)
191}
192
193/// Validate an existing stable-cell ledger record before opening it with
194/// `ic-stable-structures::Cell`.
195///
196/// `Cell::init` decodes the existing value through [`Storable::from_bytes`].
197/// That trait is panic-based, so the runtime preflights the raw memory with
198/// this fallible helper first. Empty memory is treated as uninitialized and is
199/// safe for `Cell::init` to create.
200pub fn validate_stable_cell_ledger_memory<M: Memory>(
201    memory: &M,
202) -> Result<(), StableCellLedgerError> {
203    decode_stable_cell_ledger_record_from_memory(memory)?;
204    Ok(())
205}
206
207fn serialize_record(record: &StableCellLedgerRecord) -> Vec<u8> {
208    let mut bytes = Vec::new();
209    ciborium::into_writer(record, &mut bytes).unwrap_or_else(|err| {
210        panic!("StableCellLedgerRecord serialize failed: {err}");
211    });
212    bytes
213}
214
215#[cfg(test)]
216mod tests {
217    use super::*;
218    use crate::test_cbor::hex_fixture;
219    use ic_stable_structures::{Cell, VectorMemory};
220
221    #[test]
222    fn stable_cell_ledger_record_round_trips_through_cell() {
223        let memory = VectorMemory::default();
224        let record = StableCellLedgerRecord::default();
225        let cell = Cell::init(memory.clone(), record.clone());
226
227        assert_eq!(cell.get(), &record);
228        let payload = decode_stable_cell_payload(&memory).expect("decode stable cell payload");
229        let decoded = StableCellLedgerRecord::from_bytes(Cow::Owned(payload));
230        assert_eq!(decoded, record);
231    }
232
233    #[test]
234    fn current_stable_cell_record_fixture_recovers() {
235        let bytes = hex_fixture(include_str!(
236            "../fixtures/current/stable_cell_record.cbor.hex"
237        ));
238        let record = decode_stable_cell_ledger_record(&bytes).expect("stable-cell fixture");
239
240        assert_eq!(
241            bytes,
242            crate::test_cbor::to_vec(&record).expect("re-encoded stable-cell fixture")
243        );
244        assert_eq!(
245            record
246                .store()
247                .recover()
248                .expect("fixture store recovers")
249                .current_generation(),
250            1
251        );
252    }
253
254    #[test]
255    fn malformed_payload_bytes_fail_closed_without_mutating_memory() {
256        let original = hex_fixture(include_str!(
257            "../fixtures/current/stable_cell_record.cbor.hex"
258        ));
259        let start = original
260            .windows(8)
261            .position(|bytes| bytes == b"\x67payload")
262            .unwrap()
263            + 8;
264        let oversized = u32::try_from(crate::constants::MAX_COMMITTED_PAYLOAD_BYTES + 1).unwrap();
265        let mut cases = Vec::new();
266        for replacement in [
267            vec![0x5a, 0xff, 0xff, 0xff, 0xff],
268            vec![0x5f, 0xff],
269            vec![0x41],
270            vec![0xff],
271        ] {
272            let mut bytes = original[..start].to_vec();
273            bytes.extend(replacement);
274            cases.push(bytes);
275        }
276        let mut bytes = original[..start].to_vec();
277        bytes.push(0x5a);
278        bytes.extend_from_slice(&oversized.to_be_bytes());
279        bytes.resize(bytes.len() + oversized as usize, 0);
280        cases.push(bytes);
281        for bytes in cases {
282            let memory = VectorMemory::default();
283            let pages = (bytes.len() + STABLE_CELL_HEADER_SIZE).div_ceil(65_536);
284            memory.grow(pages as u64);
285            memory.write(0, STABLE_CELL_MAGIC);
286            memory.write(3, &[STABLE_CELL_LAYOUT_VERSION]);
287            memory.write(4, &u32::try_from(bytes.len()).unwrap().to_le_bytes());
288            memory.write(STABLE_CELL_VALUE_OFFSET, &bytes);
289            let before = memory.borrow().clone();
290            for _ in 0..2 {
291                assert!(matches!(
292                    decode_stable_cell_ledger_record_from_memory(&memory),
293                    Err(StableCellLedgerError::Record(_))
294                ));
295                assert!(matches!(
296                    validate_stable_cell_ledger_memory(&memory),
297                    Err(StableCellLedgerError::Record(_))
298                ));
299            }
300            assert_eq!(*memory.borrow(), before);
301        }
302    }
303
304    #[test]
305    fn stable_cell_ledger_record_rejects_trailing_bytes() {
306        let mut bytes = serialize_record(&StableCellLedgerRecord::default());
307        bytes.push(0);
308
309        let err =
310            decode_stable_cell_ledger_record(&bytes).expect_err("trailing bytes must fail closed");
311
312        assert!(err.to_string().contains("trailing bytes"));
313    }
314
315    #[test]
316    fn stable_cell_ledger_record_rejects_unknown_top_level_fields() {
317        use crate::test_cbor::Value;
318
319        let mut map = Vec::new();
320        crate::test_cbor::map_insert(
321            &mut map,
322            Value::Text("store".to_string()),
323            crate::test_cbor::to_value(LedgerCommitStore::default()).expect("store value"),
324        );
325        crate::test_cbor::map_insert(
326            &mut map,
327            Value::Text("future_field".to_string()),
328            Value::Bool(true),
329        );
330        let bytes = crate::test_cbor::to_vec(&Value::Map(map)).expect("unknown-field stable cell");
331
332        let err = decode_stable_cell_ledger_record(&bytes)
333            .expect_err("unknown stable-cell record field must fail closed");
334
335        assert!(err.to_string().contains("future_field"));
336    }
337
338    #[test]
339    fn stable_cell_ledger_record_requires_both_commit_slot_fields() {
340        use crate::test_cbor::Value;
341
342        for (missing, present) in [("slot0", "slot1"), ("slot1", "slot0")] {
343            let mut physical = Vec::new();
344            crate::test_cbor::map_insert(
345                &mut physical,
346                Value::Text(present.to_string()),
347                Value::Null,
348            );
349            let mut store = Vec::new();
350            crate::test_cbor::map_insert(
351                &mut store,
352                Value::Text("physical".to_string()),
353                Value::Map(physical),
354            );
355            let mut record = Vec::new();
356            crate::test_cbor::map_insert(
357                &mut record,
358                Value::Text("store".to_string()),
359                Value::Map(store),
360            );
361            let bytes = crate::test_cbor::to_vec(&Value::Map(record)).expect("record bytes");
362
363            let err = decode_stable_cell_ledger_record(&bytes)
364                .expect_err("missing commit slot must fail closed");
365
366            assert!(err.to_string().contains(missing));
367        }
368    }
369
370    #[test]
371    fn stable_cell_payload_rejects_non_cell_memory() {
372        let memory = VectorMemory::default();
373        memory.grow(1);
374        memory.write(0, b"BAD");
375
376        assert_eq!(
377            decode_stable_cell_payload(&memory),
378            Err(StableCellPayloadError::NotStableCell)
379        );
380    }
381
382    #[test]
383    fn stable_cell_payload_rejects_empty_memory_without_panic() {
384        let memory = VectorMemory::default();
385
386        assert_eq!(
387            decode_stable_cell_payload(&memory),
388            Err(StableCellPayloadError::NotStableCell)
389        );
390    }
391
392    #[test]
393    fn stable_cell_ledger_preflight_classifies_bad_record_without_panic() {
394        let memory = VectorMemory::default();
395        memory.grow(1);
396        memory.write(0, STABLE_CELL_MAGIC);
397        memory.write(3, &[STABLE_CELL_LAYOUT_VERSION]);
398        memory.write(4, &1_u32.to_le_bytes());
399        memory.write(STABLE_CELL_VALUE_OFFSET, &[0xff]);
400
401        let err =
402            validate_stable_cell_ledger_memory(&memory).expect_err("bad record must be classified");
403
404        assert!(matches!(err, StableCellLedgerError::Record(_)));
405    }
406    #[test]
407    fn oversized_cell_length_is_rejected_before_payload_read() {
408        struct HeaderOnly;
409        impl Memory for HeaderOnly {
410            fn size(&self) -> u64 {
411                2048
412            }
413            fn grow(&self, _: u64) -> i64 {
414                panic!("must not grow")
415            }
416            fn write(&self, _: u64, _: &[u8]) {
417                panic!("must not write")
418            }
419            fn read(&self, offset: u64, bytes: &mut [u8]) {
420                assert_eq!(offset, 0);
421                assert_eq!(bytes.len(), STABLE_CELL_HEADER_SIZE);
422                bytes[..4].copy_from_slice(b"SCL\x01");
423                bytes[4..8].copy_from_slice(
424                    &u32::try_from(crate::constants::MAX_LEDGER_RECORD_BYTES + 1)
425                        .unwrap()
426                        .to_le_bytes(),
427                );
428            }
429        }
430        assert!(matches!(
431            decode_stable_cell_ledger_record_from_memory(&HeaderOnly),
432            Err(StableCellLedgerError::Payload(
433                StableCellPayloadError::TooLarge { .. }
434            ))
435        ));
436    }
437
438    #[test]
439    fn hostile_cbor_is_rejected_on_production_record_decode() {
440        let huge_array = [0x9b, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff];
441        let huge_string = [0x7b, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff];
442        let mut nested = vec![0x81; crate::constants::MAX_LEDGER_NESTING + 1];
443        nested.push(0);
444        for bytes in [&huge_array[..], &huge_string[..], &nested, &[0xa1], &[0xff]] {
445            assert!(decode_stable_cell_ledger_record(bytes).is_err());
446        }
447    }
448}
ic_memory/stable_cell.rs

ic_memory/
stable_cell.rs
