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fix(#3493): confine key_links from:/to: to the project directory (#3506)

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`cmdVerifyKeyLinks` resolved `from:` and `to:` with `path.join(cwd, <value>)` where the value comes verbatim from plan YAML. `path.join` normalizes `../` rather than rejecting it, so a plan travelling with a repository could name any file the process can read, and the command reports whether the link's `pattern` matched it — an arbitrary-file-read oracle reachable from `verify-phase`.

Both reads now go through `validatePath` in src/security.cts, the existing realpath-based confinement seam already used at 11 call sites. Not a missing capability — a bypassed one.

Two defects in that seam, found by adversarial review and fixed here because they affect all 11 callers:

1. A dangling in-project symlink escaped confinement. A link to an EXISTING outside path was refused (realpath lands outside) while a link to a MISSING outside path took the parent-resolution fallback and was accepted — an existence oracle for arbitrary absolute paths. lstat succeeds on a dangling link and throws ENOENT on a truly absent path; an unresolvable link is now refused. A symlink resolving inside the project is still accepted.

2. A canonicalized base was compared against an uncanonicalized path when a file and its parent were both missing, wrongly refusing legitimate in-project paths on any non-canonical cwd (every macOS temp dir). This was a live regression in this PR: the wave-pending classification (#1202) depends on the not-yet-created case. Resolution now walks up to the nearest existing ancestor.

Two adjacent aborts fixed: the from: read sat outside the per-link try, so a non-ENOENT errno killed the whole command; and an empty from: read the cwd directory, throwing EISDIR. Both now fail per-link.

The issue was filed as a fourth ADR-0174 consolidation loss. It is not one — validatePath/requireSafePath never went away, only the SDK's name for the concept did. This is an instance of epic #3473's F2 family. The ADR-0174 loss count is three.

Closes #3493

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Tom Boucher
2026-08-14 17:29:58 -04:00
committed by GitHub
parent e57e3b5d6e
commit 7a02f98574
7 changed files with 475 additions and 8 deletions
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46
src/security.cts
View File

@@ -56,12 +56,50 @@ export function validatePath(filePath: unknown, baseDir: unknown, opts: { allowA
try {
resolvedPath = fs.realpathSync(resolvedPath);
} catch {
const parentDir = path.dirname(resolvedPath);
// realpathSync failed — either resolvedPath doesn't exist at all, or it's
// a dangling symlink (the link itself exists but its target doesn't).
// lstat (unlike stat/realpath) stats the link itself and does NOT follow
// it, so it succeeds for a dangling symlink and throws ENOENT for a
// genuinely absent path. That's the discriminator: without it, a dangling
// symlink to a non-existent OUTSIDE path would fall through to the
// parent-resolution fallback below and be re-accepted as an in-project
// path, while a symlink to an EXISTING outside path is correctly
// rejected via the realpathSync success branch above — a state
// difference an attacker can use as an existence oracle for arbitrary
// absolute paths.
try {
const realParent = fs.realpathSync(parentDir);
resolvedPath = path.join(realParent, path.basename(resolvedPath));
if (fs.lstatSync(resolvedPath).isSymbolicLink()) {
return { safe: false, resolved: '', error: 'Path is an unresolvable symbolic link' };
}
} catch {
// Parent doesn't exist either — keep the resolved path as-is
// lstat also threw — resolvedPath (and its would-be link) genuinely
// doesn't exist. Fall through to ancestor resolution below.
}
// Walk up to the nearest ancestor that exists and realpath THAT, then
// re-append the remaining (not-yet-created) segments. This canonicalizes
// resolvedPath the same way resolvedBase was canonicalized above,
// regardless of how many leading directories are missing — a single
// parent-only check would leave resolvedPath un-canonicalized whenever
// the parent is also missing, which breaks the startsWith comparison
// below on any non-canonical cwd (e.g. macOS /var/... vs
// /private/var/...).
let ancestor = path.dirname(resolvedPath);
const remainder: string[] = [path.basename(resolvedPath)];
for (;;) {
try {
const realAncestor = fs.realpathSync(ancestor);
resolvedPath = path.join(realAncestor, ...remainder);
break;
} catch {
const parent = path.dirname(ancestor);
if (parent === ancestor) {
// Reached filesystem root without finding an existing ancestor —
// keep resolvedPath as-is.
break;
}
remainder.unshift(path.basename(ancestor));
ancestor = parent;
}
}
}
const normalizedBase = resolvedBase + path.sep;

57
src/verify.cts
View File

@@ -27,6 +27,7 @@ const { findOrphanSummaries, findUnsummarizedPlans } = coreUtilsMod;
import planningScopeMod = require('./planning-scope.cjs');
const { SCOPE } = planningScopeMod;
import { execGit, platformReadSync as safeReadFile } from './shell-command-projection.cjs';
import { validatePath } from './security.cjs';
import { formatGsdSlash, resolveRuntime } from './runtime-slash.cjs';
import { detectSchemaFiles, checkSchemaDrift } from './schema-detect.cjs';
import { extractTaggedBlocks } from './markdown-sectionizer.cjs';
@@ -1222,8 +1223,39 @@ function cmdVerifyKeyLinks(cwd: string, planFilePath: string, raw: boolean): voi
detail: '',
};
const fromPath = (link['from'] as string) || '';
const sourceContent = safeReadFile(path.join(cwd, fromPath));
const fromRaw = link['from'];
const fromPath = typeof fromRaw === 'string' ? fromRaw : '';
let sourceContent: string | null = null;
if (fromPath !== '') {
// An empty/missing `from:` is a malformed plan, not a path-confinement
// violation — validatePath's traversal check (and path_rejected) only
// applies to a non-empty path that actually resolves outside the
// project. Leave sourceContent as null so the existing not-found /
// pending classification below runs unchanged. Note this guard is
// narrower than it may look: `from: "."` is a non-empty string, so it
// still reaches validatePath and safeReadFile below, and DOES read the
// cwd directory (yielding "Source read failed: EISDIR") — this branch
// only short-circuits the true empty-string case.
const fromCheck = validatePath(fromPath, cwd);
if (!fromCheck.safe) {
// Do not echo result.error — it embeds absolute host paths.
check['path_rejected'] = 'from';
check['detail'] = 'Source path rejected — resolves outside the project directory';
results.push(check);
continue;
}
try {
sourceContent = safeReadFile(fromCheck.resolved);
} catch (err) {
// Report the errno only — never the message or path (untrusted `from:`
// can trigger EISDIR/EACCES, which platformReadSync re-throws for any
// non-ENOENT errno). A single bad link must not abort the whole command.
const code = (err as NodeJS.ErrnoException)?.code ?? 'unknown';
check['detail'] = `Source read failed: ${code}`;
results.push(check);
continue;
}
}
if (!sourceContent) {
// Check if the missing file is promised by a plan at the same or later wave.
const promised = getPromisedFiles();
@@ -1269,11 +1301,28 @@ function cmdVerifyKeyLinks(cwd: string, planFilePath: string, raw: boolean): voi
check['verified'] = true;
check['detail'] = 'Pattern found in source';
} else {
const targetContent = safeReadFile(path.join(cwd, (link['to'] as string) || ''));
const toRaw = link['to'];
const toPath = typeof toRaw === 'string' ? toRaw : '';
let targetContent: string | null = null;
if (toPath !== '') {
// An empty/missing `to:` is a malformed plan, not a
// path-confinement violation — only a non-empty path that
// actually resolves outside the project is path_rejected.
const toCheck = validatePath(toPath, cwd);
if (!toCheck.safe) {
// Do not read a rejected `to:` — treat as no target content
// and do not echo result.error, which embeds absolute host
// paths.
check['path_rejected'] = 'to';
check['detail'] = `Pattern "${link['pattern'] as string}" not found in source; target path rejected — resolves outside the project directory`;
} else {
targetContent = safeReadFile(toCheck.resolved);
}
}
if (targetContent && pat.test(targetContent)) {
check['verified'] = true;
check['detail'] = 'Pattern found in target';
} else {
} else if (!check['path_rejected']) {
check['detail'] = `Pattern "${link['pattern'] as string}" not found in source or target`;
}
}