Possible DoS when requesting profile events, limit parameter is NOT checked for an upper bound

HackerOne report #463010 by brandonnnn on 2018-12-14:

Summary:

Sending a GET request to a profile activity page (https://gitlab.com/PROFILENAME?limit=X) seems to have no upper bound, and appears to be an expensive operation.

Description:

The standard 10 limit which you call when visiting a profile took 700ms and was 19.52KB. When testing with 100 limit, it took 2,287ms and was 190.62KB. I only tested up to 1000 limit, which took 11,599ms, and returned an incomplete JSON payload of 1.76MB.

Some simple extrapolation would mean a request with a 50,000 activity limit would take roughly 9 minutes and return a ~93MB payload (if it managed to finish at all, which it seems like it wouldn't).

Steps To Reproduce:

1. Use curl to request the profile activity (I chose a user with >10k commits): [REDACTED]
2. Wait for the operation to return an incomplete JSON payload

Supporting Material/References:

• [Screenshot of developer console sending requests][REDACTED]

Impact

Denial of Service