NTLM authentication fails on certain endpoints - Cannot read properties of null (reading 'length')

[Wisienkaa]

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📝 Describe your problem

Hi,

I'm trying to monitor endpoints that require NTLM authentication using Uptime Kuma (v2.0.2) on Node.js v20.19.5.

When I configure a monitor with NTLM, the request fails and I get the following error in the logs:

Cannot read properties of null (reading 'length')

It seems that the response body (res.data) is null in some cases, causing the crash when the code tries to read res.data.length. Could someone help fix NTLM support so that empty responses do not cause crashes?

📝 Error Message(s) or Log

Cannot read properties of null (reading 'length')

🐻 Uptime-Kuma Version

v2.0.2

💻 Operating System and Arch

Operating System: Oracle Linux Server 9.7 (x86_64) Kernel: 5.15.0-315.196.5.1.el9uek Architecture: x86_64

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N/A

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[CommanderStorm]

@FlorianFeka I think this is the www-authenticate header being missing. What does this mean? Is this a defect in us or @Wisienkaa server?

[Wisienkaa]

@FlorianFeka I think this is the www-authenticate header being missing. What does this mean? Is this a defect in us or @Wisienkaa server?

I verified the behavior on my side and the www-authenticate header is present in the initial response. The authentication flow appears to follow the standard NTLM handshake

• First response: 401 Unauthorized with WWW-Authenticate: NTLM and Negotiate
• After NTLM authentication succeeds, the server returns 302 Redirect
• The redirect points to the actual application page, for example:
• Location: https://sample-page.pl/mysiteredirect.aspx with header Persistent-Auth: true

Curl command used:
curl --ntlm -u domain_name\user:pass https://endpoint -k -L -v

So from the server, authentication and redirect seem to work correctly.
However, in Uptime Kuma the monitor fails with:
Cannot read properties of null (reading 'length') or Cannot read properties of null (reading 'headers')
Maybe the issue is when handling the NTLM authentication flow combined with the 302 redirect?

Could you please confirm whether Uptime Kuma fully supports NTLM authentication with redirects 401 > NTLM > 302?

[louislam]

FYI, we are using axios-ntlm

This may be related issue from their repo.
Catbuttes/axios-ntlm#4

Also we are using 1.3.0, which is an old version.
https://www.npmjs.com/package/axios-ntlm/v/1.3.0

We cannot update to the latest version due to the breaking change on their side, but not sure if they fixed redirection issue in newer versions.