🔒 [Fix unsafe timing-safe comparison with user input]#125
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When using crypto.timingSafeEqual, comparing the string lengths before buffer creation is unsafe because strings with multibyte characters can have the same length but different byte sizes. This causes timingSafeEqual to throw an error, which in this case might just get caught and ignored, but is bad practice and can result in unwanted behaviors or crashes. This fix correctly converts the strings into Buffers first, and then compares the length of those buffers before calling timingSafeEqual. Co-authored-by: cmuench <211294+cmuench@users.noreply.github.com>
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🎯 What: Fixed an unsafe usage of
⚠️ Risk: If a provided token had the same string length as the expected token but contained multi-byte characters, its Buffer length would differ. Calling
crypto.timingSafeEqualinlib/mcp.js. The previous implementation compared the length of the tokens as strings (string.length) before callingcrypto.timingSafeEqualon their Buffer representations.crypto.timingSafeEqualwith unequal length buffers causes it to throw an exception. While the exception was caught in atry...catchblock, relying on exception handling for standard authentication flows or passing unequal-length buffers to security functions can introduce unexpected behaviors, crashes, or minor timing discrepancies in some environments.🛡️ Solution: The tokens are now converted into
Bufferobjects first. We then ensure that the byte lengths (buffer.length) match before executingcrypto.timingSafeEqual(bufferA, bufferB). A unit test was added (tests/mcp-timing.test.js) to explicitly reproduce the issue and verify the fix against multi-byte characters.PR created automatically by Jules for task 13534182648930956210 started by @cmuench