A symlinked journal folder lets the host chmod and write into a folder outside the home

changelog.d/2056-journal-folder-symlink.fixed.md

@@ -0,0 +1 @@
+A journal folder that is a symlink now records nothing, instead of letting the host change the permissions of the folder it points at and write the team's state journal there ([#2056](https://github.com/ThinkFlowLab/FlyBot/issues/2056)): the folder that holds `<home>/journal/state.jsonl` must be a real directory, checked before anything is created, permissions changed or written, so a link to a folder outside the home stops recording with one warning the same way any other journal problem does. A real journal folder records exactly as before.

core/src/host/journal.js

@@ -16,6 +16,7 @@
 // not match what the earlier lines built refuses the whole journal (no partial team).
 import { chmod, lstat, mkdir, readFile, rename, unlink, writeFile, appendFile } from 'node:fs/promises'
 import { dirname } from 'node:path'
+import { dirKind } from './real-dir.js'
 
 export const JOURNAL_MAX_BYTES = 20 * 1024 * 1024
 export const JOURNAL_MAX_AGE_MS = 7 * 24 * 60 * 60 * 1000
@@ -239,8 +240,15 @@ export function openJournal({ path, warn, now = Date.now, maxBytes = JOURNAL_MAX
   }
 
   const open = async () => {
-    await mkdir(dirname(path), { recursive: true, mode: 0o700 })
-    await chmod(dirname(path), 0o700)
+    // The folder is this host's own bookkeeping too: a name that stands for a link would point
+    // the mkdir and chmod below, and every later write, at a folder the team never named. Only a
+    // real directory is this host's own -- a link, a plain file or a check that could not run
+    // refuses here, before anything is created, chmod-ed or written; no folder yet is still this
+    // writer's to create, as it was before (#2055's rule, #2056).
+    const folder = dirname(path)
+    if (await dirKind(folder) === 'other') throw new JournalError('the journal folder is not a plain directory')
+    await mkdir(folder, { recursive: true, mode: 0o700 })
+    await chmod(folder, 0o700)
     let info
     try {
       info = await lstat(path)

core/test/state-journal.test.js

@@ -1,7 +1,7 @@
 import assert from 'node:assert/strict'
 import { spawnSync } from 'node:child_process'
 import { randomUUID } from 'node:crypto'
-import { existsSync, mkdirSync, mkdtempSync, readFileSync, rmSync, statSync, writeFileSync } from 'node:fs'
+import { chmodSync, existsSync, lstatSync, mkdirSync, mkdtempSync, readdirSync, readFileSync, rmSync, statSync, symlinkSync, writeFileSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { test } from 'node:test'
@@ -273,3 +273,73 @@ test('the dev replay script rebuilds a team to a seq, writes it 0600 and refuses
   assert.match(bad.stderr, /refused/)
   rmSync(home, { recursive: true, force: true })
 })
+
+// The folder above the journal is the host's own bookkeeping: a name that stands for a link
+// points the journal at a folder the team never named, and the `mkdir`/`chmod` prologue would
+// follow it. A folder that is not a real directory is therefore absent, like every other
+// journal problem: one warning, recording stops, nothing is created or changed through the link.
+test('a journal folder that is a symlink to a real folder outside the home records nothing and stays silent on disk (#2056)', async () => {
+  const home = tempHome()
+  const outside = mkdtempSync(join(tmpdir(), 'ds-bot-journal-outside-'))
+  chmodSync(outside, 0o755)
+  symlinkSync(outside, join(home, 'journal'))
+  const path = join(home, 'journal', 'state.jsonl')
+  const warnings = []
+  const journal = openJournal({ path, warn: (...args) => warnings.push(args.join(' ')) })
+  await journal.record(stateText({ version: 2, revision: 1 }))
+  await journal.record(stateText({ version: 2, revision: 2 }))
+  assert.equal(warnings.length, 1, 'the folder is refused once, not once per save')
+  assert.match(warnings[0], /not recording/)
+  if (posix) assert.equal(statSync(outside).mode & 0o777, 0o755, 'the folder the link points at keeps its mode')
+  assert.deepEqual(readdirSync(outside), [], 'nothing is written into the folder the link points at')
+  rmSync(home, { recursive: true, force: true })
+  rmSync(outside, { recursive: true, force: true })
+})
+
+test('a journal folder that is a symlink to a missing path records nothing (#2056)', async () => {
+  const home = tempHome()
+  const missing = join(home, 'not-created')
+  symlinkSync(missing, join(home, 'journal'))
+  const path = join(home, 'journal', 'state.jsonl')
+  const warnings = []
+  const journal = openJournal({ path, warn: (...args) => warnings.push(args.join(' ')) })
+  await journal.record(stateText({ version: 2, revision: 1 }))
+  assert.equal(warnings.length, 1)
+  assert.match(warnings[0], /not recording/)
+  assert.equal(existsSync(missing), false, 'the missing target is not created')
+  assert.equal(existsSync(path), false)
+  rmSync(home, { recursive: true, force: true })
+})
+
+test('a journal folder that is a plain file records nothing (#2056)', async () => {
+  const home = tempHome()
+  writeFileSync(join(home, 'journal'), 'not a folder\n')
+  const path = join(home, 'journal', 'state.jsonl')
+  const warnings = []
+  const journal = openJournal({ path, warn: (...args) => warnings.push(args.join(' ')) })
+  await journal.record(stateText({ version: 2, revision: 1 }))
+  assert.equal(warnings.length, 1)
+  assert.match(warnings[0], /not recording/)
+  assert.equal(existsSync(path), false)
+  assert.equal(readFileSync(join(home, 'journal'), 'utf8'), 'not a folder\n', 'the plain file is left as it was')
+  rmSync(home, { recursive: true, force: true })
+})
+
+test('a real journal folder still records (#2056)', async () => {
+  const home = tempHome()
+  mkdirSync(join(home, 'journal'))
+  const path = join(home, 'journal', 'state.jsonl')
+  const warnings = []
+  const journal = openJournal({ path, warn: (...args) => warnings.push(args.join(' ')) })
+  await journal.record(stateText({ version: 2, n: 1 }))
+  await journal.record(stateText({ version: 2, n: 2 }))
+  assert.deepEqual(warnings, [])
+  const text = readFileSync(path, 'utf8')
+  assert.equal(stateText(replayTo(text)), stateText({ version: 2, n: 2 }))
+  assert.equal(lstatSync(path).isSymbolicLink(), false)
+  if (posix) {
+    assert.equal(statSync(join(home, 'journal')).mode & 0o777, 0o700)
+    assert.equal(statSync(path).mode & 0o777, 0o600)
+  }
+  rmSync(home, { recursive: true, force: true })
+})

docs/subsystems/core-host.md

@@ -554,7 +554,7 @@ A local, replayable record of every change to the saved team, for multi-Bot bugs
 - **On.** `stateJournal: true` in the `bot` config. Off (the default) nothing is opened or written, so every other test runs as before.
 - **What.** `src/host/journal.js`. After each successful `state.json` write, `store.js` hands the exact snapshot text to the journal, which appends the difference from the last recorded snapshot to `<home>/journal/state.jsonl` (file mode 0600, folder 0700). Lines are `{ seq, t, op, key, prev, next, botId?, actor }`; `op` is `base` (the whole team: the first line, and any change only a key reorder explains), `set`, `delete`, or `append` (`prevLength`, `drop`, the new items: a group log or other list that grew or slid). Paths go at most three keys deep (`bots.<id>.<field>`); `botId` is set on a `bots.<id>` path; `actor` is `host` for a save and `retention` for a folded base (per-call attribution is not recorded). Only the host that holds the state lock writes, so a read-only window records nothing.
 - **Retention.** When a write would pass 20 MB, or the oldest change is older than 7 days, the oldest lines are dropped down to 90% of each cap and folded into the base line (atomic rewrite), so the kept lines still replay. A team that alone exceeds the cap stops recording.
-- **Fail closed.** Replay (`replayTo(text, seq)`) refuses the whole journal on an unreadable or incomplete line, an unknown op, a gap in `seq`, a first line that is not a base, or a `prev` that does not match what the earlier lines built; a `seq` outside the file is refused, not approximated. On start the writer replays the existing file the same way; a journal that does not replay, a path that is not a plain file, or a failed write stops recording for that run with a warning and leaves the file as it is. Saving the team never depends on the journal.
+- **Fail closed.** Replay (`replayTo(text, seq)`) refuses the whole journal on an unreadable or incomplete line, an unknown op, a gap in `seq`, a first line that is not a base, or a `prev` that does not match what the earlier lines built; a `seq` outside the file is refused, not approximated. On start the writer replays the existing file the same way; a journal that does not replay, a path that is not a plain file, or a failed write stops recording for that run with a warning and leaves the file as it is. Saving the team never depends on the journal. The folder above the journal must be a real directory too (#2056): a link, a plain file or a check that cannot run refuses before the `mkdir`/`chmod` that would follow it, so neither the permissions nor a write reach the folder a link names; a folder that does not exist yet is still this writer's to create, as before.
 - **Replay.** `core/scripts/replay.mjs` (dev-only, not in the package, see [install](install.md)) prints or writes (`--out`, new file only, 0600) the team after a given `--to <seq>`; it makes no network or process calls. Test: `core/test/state-journal.test.js` (a 3-Bot round replays byte-identical at every step).
 
 ### Standing tool approvals (#540)

patches/ds-bot/files/src/host/journal.js

@@ -16,6 +16,7 @@
 // not match what the earlier lines built refuses the whole journal (no partial team).
 import { chmod, lstat, mkdir, readFile, rename, unlink, writeFile, appendFile } from 'node:fs/promises'
 import { dirname } from 'node:path'
+import { dirKind } from './real-dir.js'
 
 export const JOURNAL_MAX_BYTES = 20 * 1024 * 1024
 export const JOURNAL_MAX_AGE_MS = 7 * 24 * 60 * 60 * 1000
@@ -239,8 +240,15 @@ export function openJournal({ path, warn, now = Date.now, maxBytes = JOURNAL_MAX
   }
 
   const open = async () => {
-    await mkdir(dirname(path), { recursive: true, mode: 0o700 })
-    await chmod(dirname(path), 0o700)
+    // The folder is this host's own bookkeeping too: a name that stands for a link would point
+    // the mkdir and chmod below, and every later write, at a folder the team never named. Only a
+    // real directory is this host's own -- a link, a plain file or a check that could not run
+    // refuses here, before anything is created, chmod-ed or written; no folder yet is still this
+    // writer's to create, as it was before (#2055's rule, #2056).
+    const folder = dirname(path)
+    if (await dirKind(folder) === 'other') throw new JournalError('the journal folder is not a plain directory')
+    await mkdir(folder, { recursive: true, mode: 0o700 })
+    await chmod(folder, 0o700)
     let info
     try {
       info = await lstat(path)

patches/ds-bot/files/test/state-journal.test.js

@@ -1,7 +1,7 @@
 import assert from 'node:assert/strict'
 import { spawnSync } from 'node:child_process'
 import { randomUUID } from 'node:crypto'
-import { existsSync, mkdirSync, mkdtempSync, readFileSync, rmSync, statSync, writeFileSync } from 'node:fs'
+import { chmodSync, existsSync, lstatSync, mkdirSync, mkdtempSync, readdirSync, readFileSync, rmSync, statSync, symlinkSync, writeFileSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { test } from 'node:test'
@@ -273,3 +273,73 @@ test('the dev replay script rebuilds a team to a seq, writes it 0600 and refuses
   assert.match(bad.stderr, /refused/)
   rmSync(home, { recursive: true, force: true })
 })
+
+// The folder above the journal is the host's own bookkeeping: a name that stands for a link
+// points the journal at a folder the team never named, and the `mkdir`/`chmod` prologue would
+// follow it. A folder that is not a real directory is therefore absent, like every other
+// journal problem: one warning, recording stops, nothing is created or changed through the link.
+test('a journal folder that is a symlink to a real folder outside the home records nothing and stays silent on disk (#2056)', async () => {
+  const home = tempHome()
+  const outside = mkdtempSync(join(tmpdir(), 'ds-bot-journal-outside-'))
+  chmodSync(outside, 0o755)
+  symlinkSync(outside, join(home, 'journal'))
+  const path = join(home, 'journal', 'state.jsonl')
+  const warnings = []
+  const journal = openJournal({ path, warn: (...args) => warnings.push(args.join(' ')) })
+  await journal.record(stateText({ version: 2, revision: 1 }))
+  await journal.record(stateText({ version: 2, revision: 2 }))
+  assert.equal(warnings.length, 1, 'the folder is refused once, not once per save')
+  assert.match(warnings[0], /not recording/)
+  if (posix) assert.equal(statSync(outside).mode & 0o777, 0o755, 'the folder the link points at keeps its mode')
+  assert.deepEqual(readdirSync(outside), [], 'nothing is written into the folder the link points at')
+  rmSync(home, { recursive: true, force: true })
+  rmSync(outside, { recursive: true, force: true })
+})
+
+test('a journal folder that is a symlink to a missing path records nothing (#2056)', async () => {
+  const home = tempHome()
+  const missing = join(home, 'not-created')
+  symlinkSync(missing, join(home, 'journal'))
+  const path = join(home, 'journal', 'state.jsonl')
+  const warnings = []
+  const journal = openJournal({ path, warn: (...args) => warnings.push(args.join(' ')) })
+  await journal.record(stateText({ version: 2, revision: 1 }))
+  assert.equal(warnings.length, 1)
+  assert.match(warnings[0], /not recording/)
+  assert.equal(existsSync(missing), false, 'the missing target is not created')
+  assert.equal(existsSync(path), false)
+  rmSync(home, { recursive: true, force: true })
+})
+
+test('a journal folder that is a plain file records nothing (#2056)', async () => {
+  const home = tempHome()
+  writeFileSync(join(home, 'journal'), 'not a folder\n')
+  const path = join(home, 'journal', 'state.jsonl')
+  const warnings = []
+  const journal = openJournal({ path, warn: (...args) => warnings.push(args.join(' ')) })
+  await journal.record(stateText({ version: 2, revision: 1 }))
+  assert.equal(warnings.length, 1)
+  assert.match(warnings[0], /not recording/)
+  assert.equal(existsSync(path), false)
+  assert.equal(readFileSync(join(home, 'journal'), 'utf8'), 'not a folder\n', 'the plain file is left as it was')
+  rmSync(home, { recursive: true, force: true })
+})
+
+test('a real journal folder still records (#2056)', async () => {
+  const home = tempHome()
+  mkdirSync(join(home, 'journal'))
+  const path = join(home, 'journal', 'state.jsonl')
+  const warnings = []
+  const journal = openJournal({ path, warn: (...args) => warnings.push(args.join(' ')) })
+  await journal.record(stateText({ version: 2, n: 1 }))
+  await journal.record(stateText({ version: 2, n: 2 }))
+  assert.deepEqual(warnings, [])
+  const text = readFileSync(path, 'utf8')
+  assert.equal(stateText(replayTo(text)), stateText({ version: 2, n: 2 }))
+  assert.equal(lstatSync(path).isSymbolicLink(), false)
+  if (posix) {
+    assert.equal(statSync(join(home, 'journal')).mode & 0o777, 0o700)
+    assert.equal(statSync(path).mode & 0o777, 0o600)
+  }
+  rmSync(home, { recursive: true, force: true })
+})