Bug report
Originally reported to the security address on September 9.
('xn--016c'+'a'*5000).encode('utf-8').decode('idna')The execution time is not linear in relation to the input string size, which can cause slowness with large inputs:
10 chars = 0.016 seconds
100 chars = 0.047 seconds
1000 chars = 2.883 seconds
2500 chars = 17.724 seconds
5000 chars = 1 min 10 seconds
Comment by @tiran:
According to spec https://unicode.org/reports/tr46/ an IDNA label must not be longer than 63 characters. Python's idna module enforces the restriction, but too late.
This may be abused in some cases, for example by passing a crafted host name to asyncio create_connection:
import asyncio
async def main():
loop = asyncio.get_running_loop()
await loop.create_connection(
lambda: [], ('xn--016c'+'a'*5000).encode('utf-8'), 443
)
asyncio.run(main())Your environment
- CPython versions tested on: CPython repository 'main' branch checkout, version 3.8.12, version 2.7.18
- Operating system and architecture: Ubuntu Linux x64
Bug report
Originally reported to the security address on September 9.
The execution time is not linear in relation to the input string size, which can cause slowness with large inputs:
10 chars = 0.016 seconds
100 chars = 0.047 seconds
1000 chars = 2.883 seconds
2500 chars = 17.724 seconds
5000 chars = 1 min 10 seconds
Comment by @tiran:
This may be abused in some cases, for example by passing a crafted host name to
asyncio create_connection:Your environment