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[spark-compete] fix(security): prevent timing side-channel in constantTimeEquals length comparison #857

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[spark-compete] fix(security): prevent timing side-channel in constantTimeEquals length comparison #857

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8 changes: 7 additions & 1 deletion src/lib/server/hosted-ui-auth.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,13 @@ const hostedUiSessions = new Map<
function constantTimeEquals(left: string, right: string): boolean {
const leftBuffer = Buffer.from(left);
const rightBuffer = Buffer.from(right);
return leftBuffer.length === rightBuffer.length && timingSafeEqual(leftBuffer, rightBuffer);
// Use the longer length to prevent timing leak on length comparison
const maxLen = Math.max(leftBuffer.length, rightBuffer.length);
const leftPadded = Buffer.alloc(maxLen, 0);
const rightPadded = Buffer.alloc(maxLen, 0);
leftBuffer.copy(leftPadded);
rightBuffer.copy(rightPadded);
return timingSafeEqual(leftPadded, rightPadded) && leftBuffer.length === rightBuffer.length;
}

function hashSessionId(sessionId: string): string {
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13 changes: 7 additions & 6 deletions src/lib/server/mcp-auth.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -9,12 +9,13 @@ const rateLimitBuckets = new Map<string, number[]>();
function constantTimeEquals(left: string, right: string): boolean {
const leftBuffer = Buffer.from(left);
const rightBuffer = Buffer.from(right);

if (leftBuffer.length !== rightBuffer.length) {
return false;
}

return timingSafeEqual(leftBuffer, rightBuffer);
// Use the longer length to prevent timing leak on length comparison
const maxLen = Math.max(leftBuffer.length, rightBuffer.length);
const leftPadded = Buffer.alloc(maxLen, 0);
const rightPadded = Buffer.alloc(maxLen, 0);
leftBuffer.copy(leftPadded);
rightBuffer.copy(rightPadded);
return timingSafeEqual(leftPadded, rightPadded) && leftBuffer.length === rightBuffer.length;
}

interface ApiKeyExtractionOptions {
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