Attachment 91435 Details for Bug 23290 – Bug 23290: XSLT system preferences allow administrators to exploit XML and XSLT vulnerabilities

[patch] Bug 23290: XSLT system preferences allow administrators to exploit XML and XSLT vulnerabilities

Bug-23290-XSLT-system-preferences-allow-administra.patch (text/plain), 2.57 KB, created by David Cook on 2019-07-10 03:56:09 UTC

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Creator: David Cook

Created: 2019-07-10 03:56:09 UTC

Size: 2.57 KB

patch

obsolete

>From 0c17c3470e0888f592a93f8caa67cbbadfd76efb Mon Sep 17 00:00:00 2001
>From: David Cook <dcook@prosentient.com.au>
>Date: Thu, 23 May 2019 16:53:57 +1000
>Subject: [PATCH] Bug 23290: XSLT system preferences allow administrators to
> exploit XML and XSLT vulnerabilities
>
>The problem is that administrators can provide XSLTs that
>can read from the server and network and write to the server. The
>
>This patch prevents the Koha::XSLT_Handler from running
>XSLT stylesheets that call actions such as read_file, write_file,
>read_net, and write_net as documented at
>https://metacpan.org/pod/XML::LibXSLT#XML::LibXSLT::Security
>
>(Previous tests suggested issues with XML external entities
>causing read file like vulnerabilities but these were not
>reproducible)
>---
> Koha/XSLT_Handler.pm | 33 +++++++++++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
>diff --git a/Koha/XSLT_Handler.pm b/Koha/XSLT_Handler.pm
>index 0682c3ca20..55ce24c53f 100644
>--- a/Koha/XSLT_Handler.pm
>+++ b/Koha/XSLT_Handler.pm
>@@ -320,8 +320,41 @@ sub _load {
>         return;
>     }
> 
>+    my $security = XML::LibXSLT::Security->new();
>+    $security->register_callback( read_file  => sub {
>+        warn "read_file called in XML::LibXSLT";
>+        #i.e. when using the exsl:document() element or document() function (to read a XML file)
>+        my ($tctxt,$value) = @_;
>+        return 0;
>+    });
>+    $security->register_callback( write_file => sub {
>+        warn "write_file called in XML::LibXSLT";
>+        #i.e. when using the exsl:document element (or document() function?) (to write an output file of many possible types)
>+        #e.g.
>+        #<exsl:document href="file:///tmp/breached.txt">
>+        #   <xsl:text>breached!</xsl:text>
>+        #</exsl:document>
>+        my ($tctxt,$value) = @_;
>+        return 0;
>+    });
>+    $security->register_callback( read_net   => sub {
>+        warn "read_net called in XML::LibXSLT";
>+        #i.e. when using the document() function (to read XML from the network)
>+        #e.g. <xsl:copy-of select="document('http://localhost')" />
>+        my ($tctxt,$value) = @_;
>+        return 0;
>+    });
>+    $security->register_callback( write_net  => sub {
>+        warn "write_net called in XML::LibXSLT";
>+        #NOTE: it's unknown how one would invoke this, but covering our bases anyway
>+        my ($tctxt,$value) = @_;
>+        return 0;
>+    });
>+
>     #parse sheet
>     my $xslt = XML::LibXSLT->new;
>+    $xslt->security_callbacks( $security );
>+
>     $rv = $code? $digest.$codelen: $filename;
>     $self->{xslt_hash}->{$rv} = eval { $xslt->parse_stylesheet($style_doc) };
>     if ($@) {
>-- 
>2.16.4

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