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Bug #80496 Issue with large Kerberos tickets and Request headers
Submitted: 2020-12-08 15:14 UTC Modified: 2021-01-10 04:22 UTC
From: martin at pentagrid dot ch Assigned: bukka (profile)
Status: No Feedback Package: FPM related
PHP Version: Irrelevant OS: centos 7, 3.10.0-1160.2.2
Private report: No CVE-ID: None
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 [2020-12-08 15:14 UTC] martin at pentagrid dot ch

Setup: centos 7, 3.10.0-1160.2.2
apache: 2.4.6-97
php: 7.2.34, but also tested with php 7.0 and 7.4


We are using kerberos for sso to login into our website. In some cases users can have have a lot of groups (1000+), so the kerberos ticket and also the request header is very large.

If the limit of the header exceeds a not clearly defined value due to the increased size of the kerberos ticket, the user gets back a white blank page.
Status code is 200 and the size of the response header is 0.

This can be caused by setting the HTTP_AUTHORIZATION variable via setenvif in apache.
SetEnvIf Authorization "(.*)" HTTP_AUTHORIZATION=$1
We need this variable for another application, so its necessary.

We are facing this issue only when we are using php-fpm, with the internal apache php_module this issuse disappears.
There are no errors in the log of apache or php-fpm, even I set it to debug or trace8.

The LimitRequestFieldSize is not the problem, I already increased this value and if this was the problem the user gets a normal error message.

I hope somebody as an idea, was this problem caused.
Look forward to any help.

Here is our config of apache and php-fpm.

<VirtualHost *:80>
    ServerName XXX

    RewriteEngine On
    RewriteRule ^(.*)$ https://XXX$1 [R=301,L]

<VirtualHost *:443>
    ServerName XXX
    ServerAlias XXX
    ServerAdmin XXX

    # Let apache know we're behind a SSL reverse proxy
    SetEnvIf X-Forwarded-Proto "^http$" HTTPS=on

    # override client IP from Header with mod_remoteip
    RemoteIPHeader X-Forwarded-For

    SetEnvIf Authorization "(.*)" HTTP_AUTHORIZATION=$1

    # haproxy
    RemoteIPInternalProxy 10.XX.XX.XX
    RemoteIPTrustedProxy 10.XX.XX.XX

    SSLEngine on
    SSLProtocol -all +TLSv1.2
    SSLHonorCipherOrder on
    SSLCompression off

    SSLCertificateFile /etc/pki/httpd/XXX.crt
    SSLCertificateKeyFile /etc/pki/httpd/XXX.key

    DirectoryIndex index.html index.php

    ProxyTimeout 240
    <Proxy "unix:/run/php-fpm/XXX.sock|fcgi://php-fpm">
	    # Note: If you configure php-fpm to use the "pm = ondemand" then use "ProxySet disablereuse=on"
        ProxySet disablereuse=off

    <FilesMatch \.php$>
        SetHandler proxy:fcgi://php-fpm

    DocumentRoot /var/www/html/XXX/current/public_html/
    <Directory /var/www/html/XXX/current/public_html/>
        Options -ExecCGI +FollowSymlinks -Includes -IncludesNOEXEC -Indexes -MultiViews -SymlinksIfOwnerMatch
        AllowOverride All

        Require all granted

    <Location />
            SetEnvIf Request_URI ^/XXX/.*$ noauth=1
            SetEnvIf Request_URI ^/XXX/.*$ noauth=1
                AuthType KerberosV5
                AuthName "XXX"
                KrbMethodNegotiate On
                KrbMethodK5Passwd On
                KrbAuthoritative On
                KrbAuthRealms XXX
                KrbVerifyKDC Off
                KrbServiceName HTTP
                Krb5KeyTab /etc/httpd/conf/XXX.http.keytab
                KrbSaveCredentials On
                KrbLocalUserMapping Off
                require valid-user

                # Monitoring - Icinga2 (Master Node I)
                Require ip 10.XXX.XX.XXX
                # Monitoring - Icinga2 (Master Node II)
                Require ip 10.XXX.XX.XXX
                # Monitoring - Icinga2 (DMZ Satellite Node)
                Require ip 10.XXX.XX.XX
                # Monitoring - Lokale Checks
                Require ip

                Require ip 10.XX.XX.XXX
                Require ip 10.XX.XX.XXX

                Require ip 10.XX.XXX.XX

                Require env noauth
                Require env REDIRECT_noauth
                Require valid-user

    <IfModule mod_negotiation.c>
        <IfModule mod_include.c>
            Alias /error/ "/var/www/html/XXX/shared/config"
            <Directory "/var/www/html/XXX/shared/config/error/">
                Options -ExecCGI +FollowSymlinks -Includes -IncludesNOEXEC -Indexes +MultiViews -SymlinksIfOwnerMatch
                # AllowOverride None
                AddOutputFilter Includes html
                AddHandler type-map var
                LanguagePriority de en es fr
                ForceLanguagePriority Prefer Fallback

                Require all granted
            ErrorDocument 400 /error/HTTP_BAD_REQUEST.html.var
            ErrorDocument 401 /error/HTTP_UNAUTHORIZED.html.var
            ErrorDocument 403 /error/HTTP_FORBIDDEN.html.var
            ErrorDocument 404 /error/HTTP_NOT_FOUND.html.var
            ErrorDocument 405 /error/HTTP_METHOD_NOT_ALLOWED.html.var
            ErrorDocument 408 /error/HTTP_REQUEST_TIME_OUT.html.var
            ErrorDocument 410 /error/HTTP_GONE.html.var
            ErrorDocument 411 /error/HTTP_LENGTH_REQUIRED.html.var
            ErrorDocument 412 /error/HTTP_PRECONDITION_FAILED.html.var
            ErrorDocument 413 /error/HTTP_REQUEST_ENTITY_TOO_LARGE.html.var
            ErrorDocument 414 /error/HTTP_REQUEST_URI_TOO_LARGE.html.var
            ErrorDocument 415 /error/HTTP_UNSUPPORTED_MEDIA_TYPE.html.var
            ErrorDocument 500 /error/HTTP_INTERNAL_SERVER_ERROR.html.var
            ErrorDocument 501 /error/HTTP_NOT_IMPLEMENTED.html.var
            ErrorDocument 502 /error/HTTP_BAD_GATEWAY.html.var
            ErrorDocument 503 /error/HTTP_SERVICE_UNAVAILABLE.html.var
            ErrorDocument 506 /error/HTTP_VARIANT_ALSO_VARIES.html.var

    Alias /icons/ "/var/www/html/XXX/shared/config"
    <Directory "/var/www/html/XXX/shared/config/icons/">
        Options -ExecCGI +FollowSymlinks -Includes -IncludesNOEXEC -Indexes +MultiViews -SymlinksIfOwnerMatch
        AllowOverride None
        Require all granted

    <IfModule mod_headers.c>
        Header set X-XSS-Protection "1; mode=block"
        Header set X-Content-Type-Options nosniff
        Header set Content-Security-Policy "script-src 'unsafe-inline' 'self' collab1-XXX; connect-src 'self' https://collab1-XXX wss://collab1-XXX;"
        Header always set Strict-Transport-Security "max-age=15552000; includeSubDomains"
        Header set Content-Security-Policy "frame-ancestors 'self'
        Header always edit Set-Cookie (.*) "$1; HttpOnly; Secure"
        Header set Referrer-Policy "strict-origin-when-cross-origin"
        Header always set Feature-Policy "geolocation 'none'; midi 'none'; camera 'none'; usb 'none'; magnetometer 'none'; accelerometer 'none'; vr 'none'; speaker 'none'; ambient-light-sensor 'none'; gyroscope 'none'; microphone 'none'"

    LogLevel warn

    ErrorLogFormat "[%{u}t] [%-m:%l] [pid %P:tid %T] %7F: %E: [client\ %a] %M% ,\ referer\ %{Referer}i"
    LogFormat "%h %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %D" combined
    LogFormat "%{X-Forwarded-For}i %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %D" proxy
    SetEnvIf X-Forwarded-For "^.*\..*\..*\..*" forwarded

    ErrorLog /var/log/httpd/XXX-error.log
    CustomLog /var/log/httpd/XXX-access.log combined env=!forwarded
    CustomLog /var/log/httpd/XXX-access.log proxy env=forwarded


; This file is managed by ansible; manual changes are overwritten ;

    user = apache
    group = apache
    listen = /run/php-fpm/XXX.sock
    listen.backlog = 511
    listen.owner = apache = apache
    listen.mode = 0660
    pm = dynamic
    pm.max_children = 150
    pm.start_servers = 10
    pm.min_spare_servers = 10
    pm.max_spare_servers = 35
    pm.process_idle_timeout = 10s
    pm.max_requests = 2500
    pm.status_path = /fpm-status
    ping.path = /fpm-ping
    ping.response = pong
    access.format = "%R - %u %t \"%m %r\" %s"
    slowlog = /var/log/php-fpm/XXX-slow.log
    request_slowlog_timeout = 5s
    request_terminate_timeout = 240s
    catch_workers_output = no
    clear_env = yes
    security.limit_extensions = .php
    php_admin_value[session.save_path] = "/var/www/html/XXX/shared/session"
    php_admin_value[upload_tmp_dir] = "/var/www/html/XXX/shared/tmp/upload_tmp_dir"
    php_admin_value[soap.wsdl_cache_dir] = "/var/www/html/XXX/current/cache/wsdl_cache_dir"
    php_admin_value[opcache.file_cache]  = "/var/www/html/XXX/current/cache/opcache_file_cache"
    php_admin_value[session.save_handler] = files
    php_admin_value[date.timezone] = Europe/Berlin
    php_admin_value[max_execution_time] = "180"
    php_admin_value[max_input_time] = "180"
    php_admin_flag[expose_php] = off
    php_admin_flag[log_errors] = on
    php_admin_value[error_log] = /var/log/php-fpm/XXX-php-error.log
    php_admin_flag[display_startup_errors] = off
    php_admin_flag[display_errors] = on
    php_admin_value[error_reporting] = E_ALL & ~E_DEPRECATED & ~E_STRICT
    php_admin_flag[track_errors] = off
    php_admin_value[memory_limit] = "512M"
    php_admin_value[post_max_size] = "100M"
    php_admin_value[upload_max_filesize] = "100M"
    php_admin_value[realpath_cache_size] = "64k"
    php_admin_value[opcache.memory_consumption] = 320
    php_admin_value[opcache.max_accelerated_files] = 13000
    php_admin_value[opcache.validate_timestamps]  = on
    php_admin_value[opcache.revalidate_freq]  = 30


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 [2020-12-28 19:44 UTC]
-Assigned To: +Assigned To: bukka
 [2020-12-28 19:44 UTC]
I'm afraid it's not much info to recreate your issue. 

I'm not really an expert on Apache
 [2020-12-28 19:46 UTC]
Sorry sent a bit faster than I wanted... :) I wanted to say that I would need a bit more info and some specific example with the size of variable when this happens. Try to maybe extracted to a minimal script and minimal configuration.

Also do you mean that you need that env to be sent to PHP application or is it for another module in Apache? If you don't need to be sent, could you maybe use something like ProxyFCGISetEnvIf?
 [2020-12-28 21:27 UTC]
-Status: Assigned +Status: Feedback
 [2021-01-10 04:22 UTC] php-bugs at lists dot php dot net
No feedback was provided. The bug is being suspended because
we assume that you are no longer experiencing the problem.
If this is not the case and you are able to provide the
information that was requested earlier, please do so and
change the status of the bug back to "Re-Opened". Thank you.
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Last updated: Tue Sep 28 20:03:36 2021 UTC