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fix(publication): authenticate stable checkpoint retirement #52

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Merged
rynfar merged 1 commit into from
Sep 3, 2026
Merged

fix(publication): authenticate stable checkpoint retirement #52

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251 changes: 162 additions & 89 deletions scripts/lib/pylon-bounded-file.mjs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,17 +12,6 @@ export const PYLON_PUBLICATION_MANIFEST_MAX_BYTES = 64 * 1024;
export const PYLON_STABLE_HISTORY_MAX_MANIFESTS = 4096;
export const PYLON_STABLE_HISTORY_MAX_BYTES = 32 * 1024 * 1024;

export class BoundedFileUnlinkedDuringReadError extends Error {
constructor(path, description, bytes, expectedSha256) {
super(`${description} changed while it was read because the same opened inode was removed.`);
this.name = "BoundedFileUnlinkedDuringReadError";
this.path = path;
this.description = description;
this.bytes = Buffer.from(bytes);
this.expectedSha256 = expectedSha256;
}
}

function statEvidence(stat) {
return Object.freeze({
dev: stat.dev,
Expand All @@ -34,6 +23,24 @@ function statEvidence(stat) {
});
}

export class BoundedFileUnlinkedDuringReadError extends Error {
constructor(path, description, bytes, expectedSha256, pathEntry, before, after, confirmedHandle = null) {
super(`${description} changed while it was read because the same opened inode was removed.`);
this.name = "BoundedFileUnlinkedDuringReadError";
this.path = path;
this.description = description;
this.bytes = Buffer.from(bytes);
this.expectedSha256 = expectedSha256;
this.sha256 = createHash("sha256").update(this.bytes).digest("hex");
this.statTransition = Object.freeze({
pathEntry: statEvidence(pathEntry),
before: statEvidence(before),
after: statEvidence(after),
confirmedHandle: confirmedHandle === null ? null : statEvidence(confirmedHandle),
});
}
}

export class BoundedFileLinkRetiredBeforeReadError extends Error {
constructor(path, description, bytes, expectedSha256, pathEntry, openedHandle) {
super(`${description} changed while it was read because one publication hardlink was retired before the file was opened.`);
Expand All @@ -50,6 +57,24 @@ export class BoundedFileLinkRetiredBeforeReadError extends Error {
}
}

export class BoundedFileLinkRetiredDuringReadError extends Error {
constructor(path, description, bytes, expectedSha256, pathEntry, before, after, finalPathEntry) {
super(`${description} changed while it was read because one publication hardlink was retired during the bounded read.`);
this.name = "BoundedFileLinkRetiredDuringReadError";
this.path = path;
this.description = description;
this.bytes = Buffer.from(bytes);
this.expectedSha256 = expectedSha256;
this.sha256 = createHash("sha256").update(this.bytes).digest("hex");
this.statTransition = Object.freeze({
pathEntry: statEvidence(pathEntry),
before: statEvidence(before),
after: statEvidence(after),
finalPathEntry: statEvidence(finalPathEntry),
});
}
}

function sameInodeReadBounds(left, right) {
return left.dev === right.dev && left.ino === right.ino && left.size === right.size &&
left.mtimeMs === right.mtimeMs;
Expand All @@ -59,28 +84,40 @@ function sameStat(left, right) {
return sameInodeReadBounds(left, right) && left.ctimeMs === right.ctimeMs && left.nlink === right.nlink;
}

function isPinnedHandleRemoval(pathEntry, before, after, extraBytes, finalPathMissing) {
return finalPathMissing && extraBytes === 0 && sameStat(pathEntry, before) &&
sameInodeReadBounds(before, after) && before.nlink > 0 && after.nlink === 0;
}

function initialRetirementKind(pathEntry, openedHandle, expectedSha256) {
function exactMonotoneStatCut(observations, fromLinks, toLinks) {
if (
expectedSha256 === null || !sameInodeReadBounds(pathEntry, openedHandle) ||
pathEntry.ctimeMs === openedHandle.ctimeMs
observations.length < 2 || observations[0].nlink !== fromLinks ||
observations.at(-1).nlink !== toLinks ||
observations.some((stat) => !sameInodeReadBounds(observations[0], stat))
) return null;
if (pathEntry.nlink === 2 && openedHandle.nlink === 1) return "link-retired";
if (pathEntry.nlink === 1 && openedHandle.nlink === 0) return "unlinked";
return null;
let cut = null;
for (let index = 1; index < observations.length; index += 1) {
const previous = observations[index - 1];
const current = observations[index];
if (previous.nlink === current.nlink) {
if (previous.ctimeMs !== current.ctimeMs) return null;
continue;
}
if (
cut !== null || previous.nlink !== fromLinks || current.nlink !== toLinks ||
previous.ctimeMs === current.ctimeMs
) return null;
cut = index;
}
return cut;
}

function isStableLinkRetirementBeforeRead(before, after, extraBytes, finalPathEntry, finalPathMissing) {
return !finalPathMissing && extraBytes === 0 && !finalPathEntry.isSymbolicLink?.() && finalPathEntry.isFile() &&
sameStat(before, after) && sameStat(after, finalPathEntry);
function permitsInitialStatTransition(pathEntry, before, expectedSha256) {
return sameStat(pathEntry, before) || (
expectedSha256 !== null && (
exactMonotoneStatCut([pathEntry, before], 2, 1) === 1 ||
exactMonotoneStatCut([pathEntry, before], 1, 0) === 1
)
);
}

function isStableHandleRemovalBeforeRead(before, after, extraBytes, finalPathMissing) {
return finalPathMissing && extraBytes === 0 && sameStat(before, after);
function isRegularPathEntry(pathEntry) {
return !pathEntry.isSymbolicLink?.() && pathEntry.isFile();
}

function exactSha256(bytes, expectedSha256) {
Expand Down Expand Up @@ -130,10 +167,8 @@ export async function readBoundedRegularFile(
let before = await handle.stat();
if (!before.isFile()) throw new Error(`${description} is not one regular non-symlink file.`);
if (validateHandle) before = await validateHandle(handle, before, description);
let retirementBeforeRead = null;
if (!sameStat(pathEntry, before)) {
retirementBeforeRead = initialRetirementKind(pathEntry, before, expectedSha256);
if (retirementBeforeRead === null) throw new Error(`${description} changed while it was read.`);
if (!permitsInitialStatTransition(pathEntry, before, expectedSha256)) {
throw new Error(`${description} changed while it was read.`);
}
if (before.size < minBytes || before.size > maxBytes) throw new Error(`${description} exceeds its format byte limit or is malformed.`);
await hooks?.afterInitialStat?.({ path, handle, stat: before });
Expand All @@ -148,6 +183,7 @@ export async function readBoundedRegularFile(
const { bytesRead: extraBytes } = await handle.read(extra, 0, 1, bytes.length);
await hooks?.beforeFinalStat?.({ path, handle, bytes });
const after = await handle.stat();
await hooks?.afterFinalStat?.({ path, handle, stat: after, bytes });
let finalPathEntry;
let finalPathMissing = false;
try {
Expand All @@ -156,37 +192,56 @@ export async function readBoundedRegularFile(
if (error?.code !== "ENOENT") throw error;
finalPathMissing = true;
}
if (exactSha256(bytes, expectedSha256)) {
if (
retirementBeforeRead === "link-retired" &&
isStableLinkRetirementBeforeRead(before, after, extraBytes, finalPathEntry, finalPathMissing)
) {
throw new BoundedFileLinkRetiredBeforeReadError(
path,
description,
bytes,
expectedSha256,
pathEntry,
before,
);
}
if (
retirementBeforeRead === "unlinked" &&
isStableHandleRemovalBeforeRead(before, after, extraBytes, finalPathMissing)
) {
throw new BoundedFileUnlinkedDuringReadError(path, description, bytes, expectedSha256);
let confirmedHandle = null;
if (finalPathMissing && after.nlink === 1 && sameStat(pathEntry, before) && sameStat(before, after)) {
confirmedHandle = await handle.stat();
}
if (extraBytes === 0 && exactSha256(bytes, expectedSha256)) {
if (!finalPathMissing && isRegularPathEntry(finalPathEntry)) {
const retirementCut = exactMonotoneStatCut([pathEntry, before, after, finalPathEntry], 2, 1);
if (retirementCut === 1) {
throw new BoundedFileLinkRetiredBeforeReadError(
path,
description,
bytes,
expectedSha256,
pathEntry,
before,
);
}
if (retirementCut !== null) {
throw new BoundedFileLinkRetiredDuringReadError(
path,
description,
bytes,
expectedSha256,
pathEntry,
before,
after,
finalPathEntry,
);
}
}
if (
retirementBeforeRead === null &&
isPinnedHandleRemoval(pathEntry, before, after, extraBytes, finalPathMissing)
) {
throw new BoundedFileUnlinkedDuringReadError(path, description, bytes, expectedSha256);
if (finalPathMissing) {
const unlinkStats = [pathEntry, before, after];
if (confirmedHandle !== null) unlinkStats.push(confirmedHandle);
if (exactMonotoneStatCut(unlinkStats, 1, 0) !== null) {
throw new BoundedFileUnlinkedDuringReadError(
path,
description,
bytes,
expectedSha256,
pathEntry,
before,
after,
confirmedHandle,
);
}
}
}
if (
retirementBeforeRead !== null || extraBytes !== 0 || finalPathMissing ||
finalPathEntry.isSymbolicLink?.() || !finalPathEntry.isFile() ||
!sameStat(before, after) || !sameStat(after, finalPathEntry)
extraBytes !== 0 || finalPathMissing || !isRegularPathEntry(finalPathEntry) ||
!sameStat(pathEntry, before) || !sameStat(before, after) || !sameStat(after, finalPathEntry)
) throw new Error(`${description} changed while it was read.`);
return bytes;
} finally {
Expand Down Expand Up @@ -237,10 +292,8 @@ export function readBoundedRegularFileSync(
try {
const before = statFile(descriptor);
if (!before.isFile()) throw new Error(`${description} is not one regular non-symlink file.`);
let retirementBeforeRead = null;
if (!sameStat(pathEntry, before)) {
retirementBeforeRead = initialRetirementKind(pathEntry, before, expectedSha256);
if (retirementBeforeRead === null) throw new Error(`${description} changed while it was read.`);
if (!permitsInitialStatTransition(pathEntry, before, expectedSha256)) {
throw new Error(`${description} changed while it was read.`);
}
if (before.size < minBytes || before.size > maxBytes) throw new Error(`${description} exceeds its format byte limit or is malformed.`);
hooks?.afterInitialStat?.({ path, descriptor, stat: before });
Expand All @@ -255,6 +308,7 @@ export function readBoundedRegularFileSync(
const extraBytes = readFile(descriptor, extra, 0, 1, bytes.length);
hooks?.beforeFinalStat?.({ path, descriptor, bytes });
const after = statFile(descriptor);
hooks?.afterFinalStat?.({ path, descriptor, stat: after, bytes });
let finalPathEntry;
let finalPathMissing = false;
try {
Expand All @@ -263,37 +317,56 @@ export function readBoundedRegularFileSync(
if (error?.code !== "ENOENT") throw error;
finalPathMissing = true;
}
if (exactSha256(bytes, expectedSha256)) {
if (
retirementBeforeRead === "link-retired" &&
isStableLinkRetirementBeforeRead(before, after, extraBytes, finalPathEntry, finalPathMissing)
) {
throw new BoundedFileLinkRetiredBeforeReadError(
path,
description,
bytes,
expectedSha256,
pathEntry,
before,
);
}
if (
retirementBeforeRead === "unlinked" &&
isStableHandleRemovalBeforeRead(before, after, extraBytes, finalPathMissing)
) {
throw new BoundedFileUnlinkedDuringReadError(path, description, bytes, expectedSha256);
let confirmedHandle = null;
if (finalPathMissing && after.nlink === 1 && sameStat(pathEntry, before) && sameStat(before, after)) {
confirmedHandle = statFile(descriptor);
}
if (extraBytes === 0 && exactSha256(bytes, expectedSha256)) {
if (!finalPathMissing && isRegularPathEntry(finalPathEntry)) {
const retirementCut = exactMonotoneStatCut([pathEntry, before, after, finalPathEntry], 2, 1);
if (retirementCut === 1) {
throw new BoundedFileLinkRetiredBeforeReadError(
path,
description,
bytes,
expectedSha256,
pathEntry,
before,
);
}
if (retirementCut !== null) {
throw new BoundedFileLinkRetiredDuringReadError(
path,
description,
bytes,
expectedSha256,
pathEntry,
before,
after,
finalPathEntry,
);
}
}
if (
retirementBeforeRead === null &&
isPinnedHandleRemoval(pathEntry, before, after, extraBytes, finalPathMissing)
) {
throw new BoundedFileUnlinkedDuringReadError(path, description, bytes, expectedSha256);
if (finalPathMissing) {
const unlinkStats = [pathEntry, before, after];
if (confirmedHandle !== null) unlinkStats.push(confirmedHandle);
if (exactMonotoneStatCut(unlinkStats, 1, 0) !== null) {
throw new BoundedFileUnlinkedDuringReadError(
path,
description,
bytes,
expectedSha256,
pathEntry,
before,
after,
confirmedHandle,
);
}
}
}
if (
retirementBeforeRead !== null || extraBytes !== 0 || finalPathMissing ||
finalPathEntry.isSymbolicLink?.() || !finalPathEntry.isFile() ||
!sameStat(before, after) || !sameStat(after, finalPathEntry)
extraBytes !== 0 || finalPathMissing || !isRegularPathEntry(finalPathEntry) ||
!sameStat(pathEntry, before) || !sameStat(before, after) || !sameStat(after, finalPathEntry)
) throw new Error(`${description} changed while it was read.`);
return bytes;
} finally {
Expand Down
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