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Date: Fri, 28 Nov 2003 13:03:04 +0100
From: Michael Bell <michael.bell@....hu-berlin.de>
To: OpenCA-Users@...ts.sourceforge.net
Cc: OpenCA-Devel@...ts.sourceforge.net, OpenCA-Core@...ts.sourceforge.net,
   OpenCA-Announce@...ts.sourceforge.net, bugtraq@...urityfocus.com,
   full-disclosure@...ts.netsys.com
Subject: [OpenCA Advisory] Vulnerabilities in signature verification


OpenCA Security Advisory [28 November 2003]

Vulnerabilities in signature validation
=======================================

Multiple flaws in OpenCA before version 0.9.1.4 could cause OpenCA to
use an incorrect certificate in the chain to determine the serial being
checked which could lead to certificates that are revoked or expired
being incorrectly accepted.

Chris Covell and Gottfried Scheckenbach performed tests with OpenCA and
CA hierarchies. They had problems to verify signatures with some
functions in OpenCA which test the signer's certificate.

Michael Bell of the OpenCA core team identified and fixed the problems
for OpenCA 0.9.1 and the CVS HEAD.

Vulnerabilities
-----------------

1. OpenCA has a library for common crypto operations - crypto-utils.lib.
    This library includes a function to determine the serial of the
    certificate which somebody used to create a PKCS#7 signature. The
    function uses this serial to load and return the certificate. The
    function used the interface of OpenCA::PKCS7 (the OpenCA PKCS#7
    module) in a wrong way.

2. The crypto library crypto-utils.lib uses all certificates which were
    included into the signature to create the X.509 object of the
    signer's certificate. The result is a object which was created from
    one of the certificates of the certificate chain. This means that
    the result is haphazard.

3. OpenCA::PKCS7 includes a wrong regular expression to detect lines
    which have nothing to do with the parsing of the certificate chain.

4. The serial in the certificate chain were parsed with a wrong regular
    expression in OpenCA::PKCS7. Big letters like A, C, B, D, E and F
    were ignored.

Who is affected?
------------------

All version of OpenCA including 0.9.1.3. A security risk is present for
people who are using digital signatures to secure approved requests
or role based access control (RBAC).

Recommendations
-----------------

Upgrade to 0.9.1.4 and use newer snapshots than
openca-0.9-SNAP-20031125.tar.gz. You can fix the problem by yourself too
with the included patches. The original files which we used to create
the diffs are from OpenCA 0.9.1.3.

-----BEGIN PATCH-----

--- openca-0.9.1.3/src/modules/openca-pkcs7/PKCS7.pm    2002-09-10 
16:42:02.000000000 +0200
+++ openca-0.9.1.4/src/modules/openca-pkcs7/PKCS7.pm    2003-11-26 
15:54:08.000000000 +0100
@@ -69,7 +69,7 @@

  our ($errno, $errval);

-($OpenCA::PKCS7::VERSION = '$Revision: 1.12 $' )=~ s/(?:^.*: 
(\d+))|(?:\s+\$$)/defined $1?"0\.9":""/eg;
+($OpenCA::PKCS7::VERSION = '$Revision: 1.12.2.1 $' )=~ s/(?:^.*: 
(\d+))|(?:\s+\$$)/defined $1?"0\.9":""/eg;

  my %params = (
          inFile => undef,
@@ -167,6 +167,8 @@

         my ( $ret, $tmp );

+       return $self->{parsed} if ($self->{parsed});
+
         $tmp = $self->{backend}->verify( SIGNATURE=>$self->{signature},
                         DATA_FILE=>$self->{dataFile},
                         CA_CERT=>$self->{caCert},
@@ -292,10 +294,10 @@
                         ($self->{status}) = ( $line =~ 
/^\s*error:([^:]*):/ );
                 }

-               next if( $line != /^depth/i );
+               next if( $line !~ /^depth/i );

                 ( $currentDepth, $serial, $dn ) =
-                       ( $line =~ /depth:([\d]+) serial:([a-f\d]+) 
subject:(.*)/ );
+                       ( $line =~ /depth:([\d]+) serial:([a-fA-F\d]+) 
subject:(.*)/ );
                 $ret->{$currentDepth}->{SERIAL} = hex ($serial) ;
                 $ret->{$currentDepth}->{DN} = $dn;

--- openca-0.9.1.3/src/common/lib/functions/crypto-utils.lib 
2002-12-22 13:08:19.000000000 +0100
+++ openca-0.9.1.4/src/common/lib/functions/crypto-utils.lib 
2003-11-26 13:04:50.000000000 +0100
@@ -176,19 +176,36 @@
                 return undef;
         }

-       ## Get signer certificate from the pkcs7 structure
-       $sigCert = new OpenCA::X509 ( SHELL => $cryptoShell,
-                       DATA => $sig->getSigner()->{CERTIFICATE});
-
-       if( not $sigCert ) {
-               $errno  = 6103;
-               $errval = i18nGettext ("Signer's certificate is 
corrupt!\nOpenCA::X509 returns errorcode __ERRNO__ (__ERRVAL__).",
-                                      "__ERRNO__", $OpenCA::X509::errno,
-                                      "__ERRVAL__", $OpenCA::X509::errval);
-               return undef;
+       ## Get signer certificate chain from the pkcs7 structure
+       my @chain = split /-----END CERTIFICATE-----/,
+                   $sig->getSigner()->{CERTIFICATE};
+       for (my $i=0; $i < scalar @chain; $i++)
+       {
+               if (not $chain[$i])
+               {
+                       delete $chain[$i];
+                       next;
+               }
+               $chain[$i] .= "-----END CERTIFICATE-----";
+               $chain[$i] =~ s/^.*-----BEGIN 
CERTIFICATE-----/-----BEGIN CERTIFICATE-----/s;
+       }
+       $sigCert = undef;
+       for (my $i=0; $i < scalar @chain; $i++)
+       {
+               $sigCert = new OpenCA::X509 ( SHELL => $cryptoShell,
+                               DATA => $chain[$i]);
+               if( not $sigCert ) {
+                       $errno  = 6103;
+                       $errval = i18nGettext ("Signer's certificate is 
corrupt!\nOpenCA::X509 returns errorcode __ERRNO__ (__ERRVAL__).",
+                                              "__ERRNO__", 
$OpenCA::X509::errno,
+                                              "__ERRVAL__", 
$OpenCA::X509::errval);
+                       return undef;
+               }
+               last if ( $tmpCert->getSerial() eq $sigCert->getSerial() );
+               $sigCert = undef;
         }

-       if( $tmpCert->getSerial() ne $sigCert->getSerial() ) {
+       if( not $sigCert ) {
                 $errno  = 6104;
                 $errval = gettext ("Signer's Certificate and DB's 
Certificate do not match");
                 return undef;
@@ -281,19 +298,8 @@
                 return undef;
         }

-       my $sigCert = new OpenCA::X509 ( SHELL => $cryptoShell,
-                                  DATA => 
$sig->getSigner()->{CERTIFICATE});
-
-       if (not $sigCert) {
-               $errno  = 6302;
-               $errval = i18nGettext ("Cannot create X509-object from 
the certificate of the signer! OpenCA::X509 returns errorcode __ERRNO__ 
(__ERRVAL__).",
-                                      "__ERRNO__", $OpenCA::X509::errno,
-                                      "__ERRVAL__", $OpenCA::X509::errval);
-               return undef;
-       }
-
         my $db_cert = $db->getItem( DATATYPE => 'CERTIFICATE',
-                               KEY => $sigCert->getSerial() );
+                               KEY => $sig->getSigner()->{SERIAL} );

         if( not $db_cert ) {
                 $errno  = 6303;

--- openca-0.9.1.3/src/common/lib/cmds/verifySignature  2003-03-31 
15:45:19.000000000 +0200
+++ openca-0.9.1.4/src/common/lib/cmds/verifySignature  2003-11-26 
13:04:34.000000000 +0100
@@ -11,7 +11,7 @@
  ## Get the Configuration parameters ...
  my ( $parsed, $lnk, $serLink, $sigInfo, $sigStatus, $signer, $signature);
  my ( $baseDoc, $info, $sigCertStatus, $def, $dbStatus, $dbMessage);
-my ( $myCN, $myEmail, $mySerial, @sigCert, $tmpCert, $pCert );
+my ( $myCN, $myEmail, $mySerial, $tmpCert, $pCert );

  ## Get Required Parameters from Configuration
  my $baseDoc    = getRequired ('verifySignatureform');
@@ -53,10 +53,7 @@
  $myDN = $signer->{DN};
  $myDN =~ s/^\///; $myDN =~ s/\//<BR>/g;

-$sigCert = new OpenCA::X509 ( SHELL => $cryptoShell,
-                             DATA => $sign->getSigner()->{CERTIFICATE});
-
-$issuerDN = $sigCert->getParsed()->{ISSUER};
+$issuerDN = $sign->getParsed()->{CHAIN}->{1}->{DN};
  $issuerDN =~ s/^\///; $issuerDN =~ s/[\/\,]/<BR>/g;

  ## Check Signature Status
@@ -71,7 +68,7 @@
                 $dbStatus = $errno;
                 $sigStatus = "<FONT 
COLOR=\"Red\">".gettext("Unknown")."</FONT>";

-               $serLink = $sigCert->getSerial();
+               $serLink = $sign->getSigner()->{SERIAL};
         } else {
                 $sigMessage = gettext("Signature correctly verified");
         }
@@ -96,11 +93,7 @@
         $serLink    = $tmpCert->getSerial();
  }

-if( $sigCert ) {
-       $pCert = $sigCert->getParsed();
-} elsif ( $tmpCert ) {
-       $pCert = $tmpCert->getParsed();
-}
+$pCert = $tmpCert->getParsed();

  ## View the Operator Used Certificate Data
  $page = $query->subVar( $page, '@DN@',       ($myDN or "n/a" ) );

--- openca-0.9.1.3/src/common/lib/cmds/viewSignature    2002-12-10 
16:18:15.000000000 +0100
+++ openca-0.9.1.4/src/common/lib/cmds/viewSignature    2003-11-26 
13:04:34.000000000 +0100
@@ -11,7 +11,7 @@
  ## Get the Configuration parameters ...
  my ( $parsed, $lnk, $serLink, $sigInfo, $sigStatus, $signer, $signature);
  my ( $baseDoc, $info, $sigCertStatus, $def, $dbStatus, $dbMessage);
-my ( $myCN, $myEmail, $mySerial, @sigCert, $tmpCert, $pCert );
+my ( $myCN, $myEmail, $mySerial, $tmpCert, $pCert );

  my $dataType   = $query->param('dataType' );
  my $key        = $query->param('key');
@@ -54,9 +54,6 @@
                 name=>"EMAIL", 
value=>$signer->{DN_HASH}->{EMAILADDRESS}[0]} );
  $myEmail = $lnk->a({-href=>$lnk->self_url()}, 
$signer->{DN_HASH}->{EMAILADDRESS}[0]);

-$sigCert = new OpenCA::X509 ( SHELL => $cryptoShell,
-                             DATA => 
$signature->getSigner()->{CERTIFICATE});
-
  ## Check Signature Status
  if( not libCheckSignature( SIGNATURE=>$signature ) ) {
         $sigStatus = "<FONT COLOR=\"Red\">".gettext("Error")."</FONT>";
@@ -105,7 +102,7 @@
         $serLink = $lnk->a({-href=>$lnk->self_url()},
                         $tmpCert->getSerial() );

-       $decSerLink = "( " . hex( $sigCert->getSerial() ) . " )";
+       $decSerLink = "( " . hex( $tmpCert->getSerial() ) . " )";

      $lnk = new CGI({cmd      => "search",
                      dataType => "CERTIFICATE",
@@ -114,11 +111,7 @@
      $myEmail = $lnk->a({-href=>$lnk->self_url()}, 
$tmpCert->getParsed()->{EMAILADDRESS});
  }

-if( $sigCert ) {
-       $pCert = $sigCert->getParsed();
-} elsif ( $tmpCert ) {
-       $pCert = $tmpCert->getParsed();
-}
+$pCert = $tmpCert->getParsed();

  ## View the Operator Used Certificate Data
  $page = $query->subVar( $page, '@CN@',       ($myCN or "n/a" ) );
-----END PATCH-----

References
------------

The Common Vulnerabilities and Exposures project (cve.mitre.org) has
assigned the name CAN-2003-0960 to this issue.

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-0960

URL for this Security Advisory:
http://www.openca.org/news/CAN-2003-0960.txt

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