dotnet/aspnetcore

Kestrel port binding default to 80 or 443 / No error/warn/info/debug when "{abc}" provided

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#24,384 opened on Jul 28, 2020

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affected-very-fewarea-networkingbughelp wantedseverity-minor

Description

Hello 👋

Describe the bug

Invalid Http/Https binding can be defaulted without any log and go on

After few long minutes (hours?) of debugging we found out that invalid port configuration will not say anything and silent. Why did it takes so long ? Because we were looking for the https binding that was https://*:8443 on our POD, and it seems that another appsettings...json file still had an http://*:{place.holder} that was not replaced So it seems that it defaulted to port 80 without saying anything at all.

The behavior was AccessDeniedException on a Socket binding attempt (because Pods should not run as root so any binding bellow 1024 is forbidden)

Questions

so I wonder about 3 things now :

  • should the SocketException / AccessDenied be explicit on the full binding url that was denied ? => http://[::]:80 or http://*:80`
  • should there be at least a WARNING on the fact that a string with letter and placerhoder is probably not a valid URI / Port ?
  • is there any form of URI that would makes this valid: http://*:{foo.bar.kix} with the port 80 ?

To Reproduce

dotnet new webapi
dotnet publish
cd ./bin/Debug/net5.0/publish/
$env:ASPNETCORE_URLS="https://*:{abc}"
./foo.exe

image

Further technical details

  • ASP.NET Core version : both 3.1.x and 5.0-preview6
  • Include the output of dotnet --info

Contributor guide

Tech stack
csharp
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
basic knowledge of ASP.NET Corefamiliarity with Kestrelunderstanding of environment variable configurationC# knowledge
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
The issue highlights that invalid port bindings like 'https://*:{abc}' silently default to port 80 without any warning. To fix, locate the Kestrel server initialization code where URL bindings are parsed, likely in the Microsoft.AspNetCore.Server.Kestrel namespace. Add a warning log when a binding string contains unresolved placeholders or invalid ports. Refer to comments in the issue for further discussion on desired behavior.