On 2025-09-11 23:59, Tan Tang Suan (NCS) wrote:
I am running Squid 3.5.20 in AWS as a forward proxy (http_port 3128) to
forward client traffic through a firewall to the Internet.
The proxy works fine when placed behind a Network Load Balancer (NLB).
However, when I place Squid behind an Application Load Balancer (ALB) on
port 3128, Squid receives malformed requests and logs the following error:
ERR_INVALID_URL
HTTP/400 Bad Request
From my understanding, this happens because ALB only supports
HTTP/HTTPS listeners and does not forward raw TCP traffic the way Squid
expects on port 3128.
That understanding is incorrect: Squid does _not_ expect raw TCP traffic
on a forward-proxy http_port. Squid expects HTTP traffic instead.
I do not know what kind of HTTP requests your Squid receives, but I
suspect that your ALB configuration does not match your Squid
configuration. If ALB supports forward proxies, configure ALB to forward
traffic to a forward proxy listening at Squid's http_port address.
If you still have problems, consider sharing a sample problematic
request received at http_port. If you use any optional http_port
parameters, please share them as well.
You should also plan to upgrade: Squid v3 is very buggy and unsupported
by Squid Project. However, the basics described about apply to any Squid
version.
HTH,
Alex.
My questions are:
1. Is there any Squid configuration that can make it compatible with AWS
ALB (which handles HTTP only), while still operating as a forward proxy?
2. If not, are there recommended approaches to integrate Squid with AWS
WAF (which requires ALB/CloudFront) so that Squid can still function as
a forward proxy for outbound client HTTPS traffic?
3. Would switching to reverse proxy mode help in this case, or would
that break HTTPS CONNECT tunneling?
Environment details:
- Squid 3.5.20
- Deployed in AWS VPC
- Works with NLB, fails with ALB
Thank you for any guidance or suggestions. Hope to hear from you soon.
Thanks and regards,
Tan Tang Suan
Mobile: 96228330
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