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🐛 Indicate weak validator in ETag header #1711

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merged 1 commit into from
Jan 4, 2025
Merged

🐛 Indicate weak validator in ETag header #1711

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1 change: 0 additions & 1 deletion packages/web-api-server/src/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,6 @@ const DELAY_AFTER = 50

const app = express()
.set('trust proxy', 1)
.set('etag', 'strong')
.use(cors({
exposedHeaders: [
'ETag',
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9 changes: 7 additions & 2 deletions packages/web-api-server/src/utils.ts
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Expand Up @@ -92,7 +92,11 @@ export async function sendGitFile(
path: string,
) {
const hash = (await git.log(['--format=%H', '-1', branch, '--', path])).latest!.hash
res.setHeader('ETag', hash)
// Git commit sha is a [weak validator](https://datatracker.ietf.org/doc/html/rfc2616#section-3.11),
// since the same value is used for different representations of the same resource (e.g. gzip
// compressed v.s. no compression). It can only guarantee semantic equivalence, not byte-for-byte
// equivalence.
res.setHeader('ETag', `W/"${hash}"`)
if (req.headers['if-none-match'] === hash) {
res.status(304).end()
await rateLimiter.reward(req.ip!, CHEAP_REQUEST_POINTS)
Expand All @@ -117,7 +121,8 @@ export async function sendGitTarball(
fileName = branch,
) {
const hash = (await git.log(['--format=%H', '-1', branch])).latest!.hash
res.setHeader('ETag', hash)
// See comments in sendGitFile() for why this is a weak validator.
res.setHeader('ETag', `W/"${hash}"`)
if (req.headers['if-none-match'] === hash) {
res.status(304).end()
await rateLimiter.reward(req.ip!, EXPENSIVE_REQUEST_POINTS)
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