[CTX] [ALL] Server Side Include in SHTML files

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Server Side Include in SHTML files

On an origin HTTP-DeleGate, a local file with suffix ".shtml" is regarded, like a file with ".html", as a HTML file except that it includes special tags for Server Side Include (SSI) and META which are to be interpreted and substituted by the HTTP-DeleGate before it is sent to a client.

SSI tags

<!--#echo var="varName" -->

will be substituted with the value specified by varName. varName can be arbitrary CGI compatible name like "REMOTE_HOST" or "HTTP_SERVER", as well as followings.

DATE_GMT -- current time in GMT

DATE_LOCAL -- current time local to the server host

LAST_MODIFIED -- the last modified time of the .shtml file

REFERER -- equiv. to HTTP_REFERER

DOCUMENT_NAME -- equiv. to SCRIPT_NAME

DOCUMENT_URI -- equiv. to REQUEST_URI

* -- all of variables as name=value pairs

<!--#include virtual="URL" -->

will be substituted with the data specified by "virtual" attribute. "virtual" can be full URL like "proto://server/upath" or partial URL like "/upath" which will be interpreted as http://delegate/upath. Relative URLs like "upath" without leading "/" are interpreted as relative to the base (current) shtml file.

Note that including a resource by SSI is under the access control of DeleGate (as origin or proxy server) common to the access control against client users. That is, if a client user is forbidden to access the included resource, it is also forbidden even via SSI-include.
Especially allowing including a resource out of the DeleGate server, with URL like virtual=http://exserver/dir/fileX can make a security hole made by a user as a SHTML writer. In an origin server, relaying as a proxy must be forbidden by RELAY=no, but it also forbids SSI-include to do from other servers.
A simple workaround in version 9 is adding a limited RELAY as RELAY="proxy:http:exserver:*" that only allows relaying to exserver. Another safer workaround is using MOUNT like MOUNT="/ex/* http://exserver/dir/*" then write SSI-include like virtual="/ex/fileX". But both of these allows client users to access to resources other than the intended virtual URL in the exserver.

To cope with the above problem in version 10, RELAY=ssi is introduced to be used together with RELAY=no. RELAY=ssi allows SHTML writers to do include from other servers, leaving the permission for client users unchanged (as RELAY=no). In other words without RELAY=ssi, you (as the administrator of DeleGate) can forbid SHTML writers to include from other servers. Also you can restrict the includable target server (and protocols or clients) by the generic notation of DeleGate as RELAY=ssi:protocolList:serverList:clientList.
Another (and maybe more important) extension in version 10 is relaying request/response message header (as Cookie or User-Agent) back and forth between client and server via SSI-include.

NOTE: Maybe it is impossible to forbid CGIs to access arbitrary servers in a way independent of platforms and languages. But at least we can forbid CGIs completely with REMITTABLE="+,-cgi".

<!--#fsize virtual="URL" -->

<!--#flastmod virtual="URL" -->

will be substituted with the size or the last modified time of the specified data respectively.

<!--#config timefmt=timeFormat -->

will specify the format of generated time string by "#echo","#flastmod" or so, in strftime(3) compatible format. (default: timefmt="%a, %d %b %Y %H:%M:%S %z")

META tags

<META HTTP-EQUIV=fieldName content="fieldBody">

will generate "fieldName: fieldBody" header in the HTTP response message. The following patterns in fileBody will be substituted as described above.

${varName} or <!--#echo var=varName -->

${flastmod:URL} or <!--#flastmod virtual=URL -->

${fsize:URL} or <!--#fsize virtual=URL -->

${include:URL} or <!--#include virtual=URL -->

Example:

<META HTTP-EQUIV=Status content="200 OK">

<META HTTP-EQUIV=Content-Type content="text/html">

<META HTTP-EQUIV=Pragma content="no-cache">

<META HTTP-EQUIV=Date content="${DATE_GMT}">

<META HTTP-EQUIV=Last-Modified content="${flastmod:URL}">

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