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Posted to bugs@httpd.apache.org by bu...@apache.org on 2012/08/02 16:35:51 UTC

[Bug 53643] New: apache segfaults with mod_authn_dbd when dbd_min is zero

https://issues.apache.org/bugzilla/show_bug.cgi?id=53643

          Priority: P2
            Bug ID: 53643
          Assignee: bugs@httpd.apache.org
           Summary: apache segfaults with mod_authn_dbd when dbd_min is
                    zero
          Severity: critical
    Classification: Unclassified
                OS: Linux
          Reporter: erno.kovacs@freemail.hu
          Hardware: PC
            Status: NEW
           Version: 2.2.22
         Component: mod_authn_dbd
           Product: Apache httpd-2

apache segfaults with mod_authn_dbd when dbd_min is zero:

# tail -f error.log
[Thu Aug 02 16:27:37 2012] [info] mod_ssl/2.2.22 compiled against Server:
Apache/2.2.22, Library: OpenSSL/0.9.8o
[Thu Aug 02 16:27:37 2012] [notice] Apache/2.2.22 (Unix) mod_ssl/2.2.22
OpenSSL/0.9.8o configured -- resuming normal operations
[Thu Aug 02 16:27:37 2012] [info] Server built: Aug  2 2012 15:37:02
[Thu Aug 02 16:27:37 2012] [debug] worker.c(1757): AcceptMutex: sysvsem
(default: sysvsem)
[Thu Aug 02 16:27:39 2012] [notice] child pid 13127 exit signal Segmentation
fault (11)

Config line for compiling against the Squeeze packages is:

./configure --prefix=/usr/local/apachetest --disable-echo --enable-cache
--disable-include \
            --enable-ssl --enable-http --enable-cgi   --disable-imap
--disable-userdir \
            --enable-dbd --enable-authn-dbd --with-apr=/usr
--with-apr-util=/usr \
            --enable-so --enable-rewrite --disable-vhost-alias 
--with-mpm=worker

# dpkg -l|grep apr
ii  libapr1                             1.4.2-6+squeeze4             The Apache
Portable Runtime Library
ii  libapr1-dev                         1.4.2-6+squeeze4             The Apache
Portable Runtime Library - Development Headers
ii  libaprutil1                         1.3.9+dfsg-5                 The Apache
Portable Runtime Utility Library
ii  libaprutil1-dbd-mysql               1.3.9+dfsg-5                 The Apache
Portable Runtime Utility Library - MySQL Driver
ii  libaprutil1-dev                     1.3.9+dfsg-5                 The Apache
Portable Runtime Utility Library - Development Headers


httpd.conf:
############################################################### alapveto adatok
begin
ServerRoot "/usr/local/apachetest"
Listen 50080
User nobody
Group nogroup
ServerAdmin tech@xxxxxxx.hu
ServerName xxxxxxx.hu:80
DocumentRoot "/usr/local/apachetest/htdocs"
DirectoryIndex index.html index.htm index.php
ExtendedStatus on
ServerTokens Prod
ServerSignature Off
DefaultType text/plain
Timeout 30
Keepalive on
MaxKeepAliveRequests 100
KeepAliveTimeout 5
UseCanonicalName Off
AccessFilename .htaccess
HostnameLookups off
CoreDumpDirectory /tmp
############################################################### alapveto adatok
end

############################################################### MPM begin
ThreadLimit 10
ThreadsPerChild 1
ServerLimit 10
MaxClients 10
StartServers 1
MinSpareThreads 1
MaxSpareThreads 1
ThreadStackSize 131072
MaxRequestsPerChild  10000
############################################################### MPM end

#################################################################### mod_dbd
begin
DBDriver mysql
DBDParams "host=mysql.xxxxxxx.hu dbname=xxxxxxx user=xxxxxxx password=xxxxxxx"

DBDMin  0
DBDKeep 5
DBDMax  10
DBDExptime 60
#################################################################### mod_dbd
end

############################################################### access control
begin
<Directory />
    Options FollowSymLinks
    AllowOverride None
    Order deny,allow
    Deny from all

</Directory>

<Directory /usr/local/apachetest/htdocs>
  Order allow,deny
  Allow from all

  AuthType Basic
  AuthName "My Server"
  AuthBasicProvider dbd

  # core authorization configuration
  Require valid-user

  AuthDBDUserPWQuery "SELECT pd_password FROM w3_protecteddirs WHERE
pd_username = %s"
</Directory>

<FilesMatch "^\.ht">
    Order allow,deny
    Deny from all
    Satisfy All
</FilesMatch>
############################################################### access control
end

################################################################### logging
begin
PidFile "logs/httpd.pid"
ErrorLog "logs/error.log"
LogLevel debug
LogFormat "%h %V %u %t \"%r\" %s %b \"%{Referer}i\" \"%{User-Agent}i\""
TransferLog "logs/access.log"
#################################################################### logging
end



If I increase DBD_Min to 1, Apache does not crash.

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[Bug 53643] apache segfaults with mod_authn_dbd when dbd_min is zero

Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=53643

--- Comment #1 from erno.kovacs@freemail.hu ---
However DBD_Min 0 is definetly a problem, and with a higher value
authentication works fine, I can still reproduce the segfaults by pushing F5
(refresh) in the browser for a few minutes.
I believe this is a stack issue, as I increase ThreadStackSize it works OK, no
segfaults. I would recommend mentioning this in documentation. 256KByte seems
to be enough.

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[Bug 53643] apache segfaults with mod_authn_dbd when dbd_min is zero

Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=53643

--- Comment #2 from erno.kovacs@freemail.hu ---
Nevertheles, Apache even segfaults, when DBD is not configured at all in
rsrc_conf and an attacker has the ability to upload .htaccess files with
content of AuthBasicProvider dbd and AllowOverride AuthConfig is on.

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