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I have a strange problem that looks to me like a bug.

I am using apache 2.2 as a simple forward proxy.

The same setup works on another server (same operation system, same version).

I simply install apache2 and enable the modules proxy, proxy_http and proxy_connect and set up proper authentication methods.

Normal http requests work fine, but https requests display (after some waiting time) the following erro in the browser (chrome);

Error 111 (net::ERR_TUNNEL_CONNECTION_FAILED): Unknown error.

The apache errror log displays the following:

[Tue Dec 27 18:30:17 2011] [error] [client ***] (20014)Internal error: proxy: error reading status line from remote server ***.com
[Tue Dec 27 18:30:17 2011] [error] [client ***] proxy: Error reading from remote server returned by ***.com:443

I read some bug reports and googled for the error and found some stuff that in reverse proxy setups and set some some environment variables to disable keep alives, but it did not solve the problem.

The strange thing is that on another server it seems to work just fine!

Can anybody point me in the right direction with this error?


The servers run on Ubuntu 10.04.3 LTS but I also reproduced the probelm on a test server which runs Ubuntu 10.04 LTS

The exact apache version affected is:

root@dev:/home/pm-peer# apache2ctl -V
Server version: Apache/2.2.14 (Ubuntu)
Server built:   Nov  3 2011 03:29:23
Server's Module Magic Number: 20051115:23
Server loaded:  APR 1.3.8, APR-Util 1.3.9
Compiled using: APR 1.3.8, APR-Util 1.3.9
Architecture:   64-bit
Server MPM:     Prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APACHE_MPM_DIR="server/mpm/prefork"
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D SUEXEC_BIN="/usr/lib/apache2/suexec"
 -D DEFAULT_PIDLOG="/var/run/"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_LOCKFILE="/var/run/apache2/accept.lock"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="/etc/apache2/mime.types"
 -D SERVER_CONFIG_FILE="/etc/apache2/apache2.conf"

My configuration which differs from the default is the following:

ServerLimit 1024

ProxyRequests On
ProxyVia Block
ProxyStatus Off

# i tried the following to solve the problem
#SetEnv force-proxy-request-1.0 1
#SetEnv proxy-nokeepalive 1
#SSLProxyEngine on

DefineExternalAuth proxy_auth pipe /home/pm-peer/proxy_auth.php

<Proxy *>

        Allow from

        AuthType Basic
        AuthName "Password Required"
        AuthBasicProvider external
        AuthExternal proxy_auth
        Require valid-user

    # tried the following directives also inside the proxy container
    #SetEnv force-proxy-request-1.0 1
    #SetEnv proxy-nokeepalive 1


I also tried upgrading the other server where everything works with apt-get upgrade, because I suspected that maby an update caused this error. But after the ugprade and an apache restart everything still worked.

I think I must have (without knowing it) done something on the other server that made it work, but I have no clue what it could be. Maby I installed a package or library that is missing?

I start with a ubuntu minimal version and isntall the following, thats pretty much it:

apt-get install -y php5-cli libapache2-mod-php5 php5-curl libapache2-mod-authnz-external logrotate php5-mysql
a2enmod proxy
a2enmod proxy_http
a2enmod proxy_connect
a2enmod rewrite
a2enmod headers
a2enmod authnz_external
share|improve this question
Do you have SSLProxyEngine on in your configuration? – lvmisooners Dec 27 '11 at 17:55
Can you provide the relevant config from Apache? – Shane Madden Dec 27 '11 at 17:58
No, but I tried and it didnt change anything. – The Shurrican Dec 27 '11 at 20:50
I added everything to the question. Thanks for your help – The Shurrican Dec 27 '11 at 21:06
up vote 1 down vote accepted

Wow, there could be a lot of things wrong. How sure are you that your Apache2 proxy was compiled with SSL support (not saying that it needs to be but it might help)? Your compile options that you listed do not show this. Also, can you tell us what your destination SSL server is? Is it also a Apache2 server? If so, is it listening on all interfaces or just localhost?

What happens if you set Apache environment variable for "proxy-initial-not-pooled" ?

share|improve this answer
accepting this answer because it was just right "a lot could be wrong". including things i did not consider and id made me look at it from a wider perspective which immediately resolved the issue. – The Shurrican Dec 29 '11 at 15:16

As so often the solution was trivial and the cause pure stupidity.

I had a ProxyMatch rule defined that interfered with the configuration.

Thanks for the help anway.

share|improve this answer

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