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fix(desktop): drop RegExp from dangling-fence close detection

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Previous attempt tried to break the dataflow by reconstructing the
close-fence regex from a literal char + marker.length, but CodeQL still
traced marker.length back to input and kept flagging the test-fixture
URLs as hostname-regex sources (js/incomplete-hostname-regexp).

Replace `new RegExp(...)` + `closeRe.test(body)` with a string-only
hasCloseFenceLine() helper that splits on '\n' and uses ===. No regex
on this path now, so input data can no longer reach a RegExp source.

Behavior preserved: matches lines that are (whitespace + marker +
whitespace), which is what the original `\n[ \t]*${marker}[ \t]*(?=\n|$)`
matched. All 12 markdown-text tests still pass.
This commit is contained in:
Brooklyn Nicholson
2026-05-11 17:01:41 -04:00
parent d760e6b7db
commit d37ea68822
1 changed files with 32 additions and 7 deletions
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apps/desktop/src/lib/markdown-preprocess.ts
+32 -7
View File
@@ -14,6 +14,37 @@ const LOCAL_PREVIEW_ONLY_RE = /^https?:\/\/(?:localhost|127\.0\.0\.1|0\.0\.0\.0|
const URL_ONLY_LINE_RE = /^\s*https?:\/\/\S+\s*$/i
const CITATION_MARKER_RE = /(?<=[\p{L}\p{N})\].,!?:;"'”’])\[(?:\d+(?:\s*,\s*\d+)*)\](?!\()/gu
/**
* Returns true when `body` contains a line that's exactly `marker` (modulo
* leading/trailing horizontal whitespace) — i.e. an unambiguous close fence
* for an opening fence with the same marker.
*
* Implemented with string comparisons (not RegExp) so that input-derived
* `marker` values can never bleed into a regex pattern. This matters for
* CodeQL's `js/incomplete-hostname-regexp` dataflow, which would otherwise
* trace test-fixture URLs from the input through `marker` into the regex
* source, even though `marker` is captured by `(`{3,}|~{3,})` and can only
* ever be backticks or tildes.
*/
function hasCloseFenceLine(body: string, marker: string): boolean {
const lines = body.split('\n')
// Original regex required `\n` immediately before the close fence, so the
// first line of `body` (which has no preceding newline within `body`)
// cannot itself be the close fence.
for (let i = 1; i < lines.length; i += 1) {
const line = lines[i]
let lo = 0
let hi = line.length
while (lo < hi && (line[lo] === ' ' || line[lo] === '\t')) lo += 1
while (hi > lo && (line[hi - 1] === ' ' || line[hi - 1] === '\t')) hi -= 1
if (line.slice(lo, hi) === marker) {
return true
}
}
return false
}
function scrubBacktickNoise(text: string): string {
const balancedFenceRe = /(^|\n)([ \t]*)(`{3,}|~{3,})([^\n]*)\n([\s\S]*?)\n[ \t]*\3[ \t]*(?=\n|$)/g
const protectedRanges: { end: number; start: number }[] = []
@@ -32,14 +63,8 @@ function scrubBacktickNoise(text: string): string {
const marker = match[2] || '```'
const info = match[3] || ''
const body = match[4] || ''
// `marker` is captured by `(`{3,}|~{3,})` above, so its only meta-character
// is the backtick or tilde. Reconstruct the close-fence pattern from a
// literal char + length to keep the regex source free of tainted input
// (and to keep CodeQL's hostname-regexp dataflow happy).
const fenceChar = marker[0] === '~' ? '\\~' : '`'
const closeRe = new RegExp(`\\n[ \\t]*${fenceChar}{${marker.length}}[ \\t]*(?=\\n|$)`)
if (!closeRe.test(body) && sanitizeLanguageTag(info) && !isLikelyProseFence(info, body)) {
if (!hasCloseFenceLine(body, marker) && sanitizeLanguageTag(info) && !isLikelyProseFence(info, body)) {
protectedRanges.push({ end: text.length, start })
break