I think I've found a bug in apache httpd (https://bz.apache.org/bugzilla/show_bug.cgi?id=69261) and this repository is meant to demonstrate and reproduce that bug.
Run run.sh and the script will build and interact with two containers.
One based off of apache 2.4.50 that works and one based off of 2.4.62 that doesn't.
The script uses podman to build containers, but could easily be modified to use docker
instead.
When the script uses curl to the Location that's been added - we can see logs like this where
the request is sucessfully being reverse proxied back to the UDS socket that was started in the
container's entrypoint.
[Wed Aug 14 16:06:11.632955 2024] [proxy:trace2] [pid 8:tid 137483257747200] proxy_util.c(2355): [client 10.0.2.100:40248] *: using default reverse proxy worker for unix:/tmp/bug_test.sock|http://localhost/test (no keepalive)
[Wed Aug 14 16:06:11.632958 2024] [proxy:trace2] [pid 8:tid 137483257747200] proxy_util.c(2312): [client 10.0.2.100:40248] *: rewrite of url due to UDS(/tmp/bug_test.sock): http://localhost/test (proxy:http://localhost/test)
[Wed Aug 14 16:06:11.632960 2024] [proxy:debug] [pid 8:tid 137483257747200] mod_proxy.c(1504): [client 10.0.2.100:40248] AH01143: Running scheme unix handler (attempt 0)
[Wed Aug 14 16:06:11.632967 2024] [proxy_wstunnel:trace5] [pid 8:tid 137483257747200] mod_proxy_wstunnel.c(340): [client 10.0.2.100:40248] handler fallback
[Wed Aug 14 16:06:11.632974 2024] [proxy_http:trace1] [pid 8:tid 137483257747200] mod_proxy_http.c(1875): [client 10.0.2.100:40248] HTTP: serving URL http://localhost/test
[Wed Aug 14 16:06:11.632981 2024] [proxy:debug] [pid 8:tid 137483257747200] proxy_util.c(2528): AH00942: http: has acquired connection for (*)
[Wed Aug 14 16:06:11.632984 2024] [proxy:debug] [pid 8:tid 137483257747200] proxy_util.c(2583): [client 10.0.2.100:40248] AH00944: connecting http://localhost/test to localhost:80
[Wed Aug 14 16:06:11.632985 2024] [proxy:debug] [pid 8:tid 137483257747200] proxy_util.c(2620): [client 10.0.2.100:40248] AH02545: http: has determined UDS as /tmp/bug_test.sock
[Wed Aug 14 16:06:11.633037 2024] [proxy:debug] [pid 8:tid 137483257747200] proxy_util.c(2806): [client 10.0.2.100:40248] AH00947: connected /test to httpd-UDS:0
[Wed Aug 14 16:06:11.633062 2024] [proxy:debug] [pid 8:tid 137483257747200] proxy_util.c(3177): AH02823: http: connection established with Unix domain socket /tmp/bug_test.sock (*)
Version 2.4.62 however fails, with these entries in the log. And indeed the result from curl shows httpd
returns a 500 error page. 2.4.62 cannot determine the correct handler for the request. Notably mod_proxy_http declines
the URL.
[Wed Aug 14 16:06:31.593622 2024] [proxy:trace2] [pid 11:tid 28] proxy_util.c(2625): [client 10.0.2.100:50980] *: using default reverse proxy worker for unix:/tmp/bug_test.sock|http://localhost/test (no keepalive)
[Wed Aug 14 16:06:31.593624 2024] [proxy:debug] [pid 11:tid 28] mod_proxy.c(1465): [client 10.0.2.100:50980] AH01143: Running scheme unix handler (attempt 0)
[Wed Aug 14 16:06:31.593628 2024] [proxy_wstunnel:trace5] [pid 11:tid 28] mod_proxy_wstunnel.c(364): [client 10.0.2.100:50980] handler fallback
[Wed Aug 14 16:06:31.593633 2024] [proxy_http:debug] [pid 11:tid 28] mod_proxy_http.c(1901): [client 10.0.2.100:50980] AH01113: HTTP: declining URL unix:/tmp/bug_test.sock|http://localhost/test
[Wed Aug 14 16:06:31.593637 2024] [proxy_fcgi:debug] [pid 11:tid 28] mod_proxy_fcgi.c(1078): [client 10.0.2.100:50980] AH01076: url: unix:/tmp/bug_test.sock|http://localhost/test proxyname: (null) proxyport: 0
[Wed Aug 14 16:06:31.593639 2024] [proxy_fcgi:debug] [pid 11:tid 28] mod_proxy_fcgi.c(1083): [client 10.0.2.100:50980] AH01077: declining URL unix:/tmp/bug_test.sock|http://localhost/test
[Wed Aug 14 16:06:31.593643 2024] [proxy_scgi:debug] [pid 11:tid 28] mod_proxy_scgi.c(547): [client 10.0.2.100:50980] AH00865: declining URL unix:/tmp/bug_test.sock|http://localhost/test
[Wed Aug 14 16:06:31.593646 2024] [:debug] [pid 11:tid 28] mod_proxy_uwsgi.c(512): [client 10.0.2.100:50980] declining URL unix:/tmp/bug_test.sock|http://localhost/test
[Wed Aug 14 16:06:31.593652 2024] [proxy_ajp:debug] [pid 11:tid 28] mod_proxy_ajp.c(785): [client 10.0.2.100:50980] AH00894: declining URL unix:/tmp/bug_test.sock|http://localhost/test
[Wed Aug 14 16:06:31.593659 2024] [proxy_connect:trace1] [pid 11:tid 28] mod_proxy_connect.c(177): [client 10.0.2.100:50980] declining URL unix:/tmp/bug_test.sock|http://localhost/test
[Wed Aug 14 16:06:31.593664 2024] [proxy_ftp:trace3] [pid 11:tid 28] mod_proxy_ftp.c(1014): [client 10.0.2.100:50980] declining URL unix:/tmp/bug_test.sock|http://localhost/test - not ftp:
[Wed Aug 14 16:06:31.593665 2024] [proxy:warn] [pid 11:tid 28] [client 10.0.2.100:50980] AH01144: No protocol handler was valid for the URL /test (scheme 'unix'). If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule.
10.0.2.100 - - [14/Aug/2024:16:06:31 +0000] "GET /test HTTP/1.1" 500 531