CVE-2018-18854 Use TreeMap instead of HashMap for JsObject key/value pairs, fixes #277 #280
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jrudolph
commented
Oct 30, 2018
| val regularTime = nanoBench { JsonParser(regularJson) } | ||
| val collidingTime = nanoBench { JsonParser(collidingJson) } | ||
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| collidingTime / regularTime must be < 2L // speed must be in same order of magnitude |
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If you undo the fix, the ratio is ~ 100x slowdown for this test on my machine.
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jrudolph
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Oct 30, 2018
| | "yes": 1, | ||
| | "no": 0 | ||
| | }, ["a", "b", null], false] | ||
| | "no": 0, |
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New rendering output is now ordered by the key Strings. However, that's not guaranteed anywhere so I fixed the test not to assume anything.
johanandren
approved these changes
Nov 7, 2018
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LGTM |
…pairs, fixes spray#277 The problem is that with String's hashCode implementation it is too simple to create synthetic collisions. This allows an attacker to create an object with keys that all collide which leads to a performance drop for the HashMap just for creating the map in the first place. See scala/bug#11203 for more information about the underlying HashMap issue. For the time being, it seems safer to use a TreeMap which uses String ordering. Benchmarks suggest that using a TreeMap is only ~6% slower for reasonably sized JSON objects up to 100 keys. Benchmark for non-colliding keys: Benchmark (_size) (parser) Mode Cnt Score Error Units ExtractFieldsBenchmark.readSpray 1 HashMap thrpt 5 1195832.262 ± 64366.605 ops/s ExtractFieldsBenchmark.readSpray 1 TreeMap thrpt 5 1342009.641 ± 17307.555 ops/s ExtractFieldsBenchmark.readSpray 10 HashMap thrpt 5 237173.327 ± 70341.742 ops/s ExtractFieldsBenchmark.readSpray 10 TreeMap thrpt 5 233510.618 ± 69638.750 ops/s ExtractFieldsBenchmark.readSpray 100 HashMap thrpt 5 23202.016 ± 1514.763 ops/s ExtractFieldsBenchmark.readSpray 100 TreeMap thrpt 5 21899.072 ± 823.225 ops/s ExtractFieldsBenchmark.readSpray 1000 HashMap thrpt 5 2073.754 ± 66.093 ops/s ExtractFieldsBenchmark.readSpray 1000 TreeMap thrpt 5 1793.329 ± 43.603 ops/s ExtractFieldsBenchmark.readSpray 10000 HashMap thrpt 5 208.160 ± 7.466 ops/s ExtractFieldsBenchmark.readSpray 10000 TreeMap thrpt 5 160.349 ± 5.809 ops/s
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The problem is that with String's hashCode implementation it is too simple to
create synthetic collisions. This allows an attacker to create an object with
keys that all collide which leads to a performance drop for the HashMap
just for creating the map in the first place. See scala/bug#11203
for more information about the underlying HashMap issue.
For the time being, it seems safer to use a TreeMap which uses String ordering.
Benchmarks suggest that using a TreeMap is only ~6% slower for reasonably sized JSON objects
up to 100 keys.
Benchmark for non-colliding keys:
/cc @plokhotnyuk