Apache JServ Protocol
{{Short description|Computer networking protocol}}
The Apache JServ Protocol (AJP) is a binary protocol that can proxy inbound requests from a web server through to an application server that sits behind the web server. AJP is a highly trusted protocol and should never be exposed to untrusted clients, which could use it to gain access to sensitive information or execute code on the application server.{{cite web |title=AJP File Read/Inclusion in Apache Tomcat (CVE-2020-1938) and Undertow (CVE-2020-1745) |url=https://access.redhat.com/solutions/4851251 |website=Red Hat Customer Portal |access-date=1 March 2020}}
It also supports some monitoring in that the web server can ping the application server. Web implementors typically use AJP in a load-balanced deployment where one or more front-end web servers feed requests into one or more application servers. Sessions are redirected to the correct application server using a routing mechanism wherein each application server instance gets a name (called a route). In this scenario the web server functions as a reverse proxy for the application server. Lastly, AJP supports request attributes which, when populated with environment-specific settings in the reverse proxy, provides for secure communication between the reverse proxy and application server.{{cite web|title=NativeSPAttributeAccess|url=https://wiki.shibboleth.net/confluence/display/SHIB2/NativeSPAttributeAccess|website=Shibboleth Consortium|access-date=13 November 2017}}{{cite web |title=Apache Module mod_proxy_ajp |url=https://httpd.apache.org/docs/2.4/mod/mod_proxy_ajp.html |website=Apache HTTP Server Project |access-date=13 November 2017}}
AJP runs in Apache HTTP Server 1.x using the {{kbd|mod_jk}} plugin and in Apache 2.x using {{kbd|mod_proxy_ajp}}, {{kbd|mod_proxy}} and proxy balancer modules together. Other web server implementations exist for: lighttpd 1.4.59,{{cite web |url=https://redmine.lighttpd.net/projects/lighttpd/wiki/Docs_ModAJP13 |title=Docs - Lighttpd - lighty labs |website=redmine.lighttpd.net |access-date=14 July 2021}} nginx,{{cite web |url=https://github.com/yaoweibin/nginx_ajp_module |title=nginx_ajp_module: support AJP protocol proxy with Nginx |first=Weibin|last=Yao(姚伟斌) |date=6 October 2017 |access-date=9 October 2017 |via=GitHub}} Grizzly 2.1,{{cite web |url=https://grizzly.java.net/nonav/docs/docbkx2.3/html/ajp.html |title=AJP |publisher=java.net |work=Grizzly 2.3 User's Guide |access-date=2013-04-29}} and the Internet Information Services.{{cite web |url=http://boncode.net/connector/webdocs/Tomcat_Connector.htm |title=BonCode Apache Tomcat AJP 1.3 Connector |website=boncode.net |access-date=9 October 2017}}
Web container application servers supporting AJP include: Apache Tomcat, WildFly (formerly JBoss AS), and GlassFish.
History
Alexei Kosut originally developed the Apache JServ Protocol in July 1997{{cite web |last1=Barbieri |first1=Federico |last2=Fumagalli |first2=Pierpaolo |last3=Kluft |first3=Ian |last4=Korthof |first4=Ed |last5=Mazzocchi |first5=Stefano |last6=Pool |first6=Martin |title=Apache JServ Protocol Version 2.1 |date=June 30, 1998 |work=Java Apache Project |url=http://java.apache.org/jserv/protocol/AJPv21.html |archive-url=https://web.archive.org/web/20030804213216/http://java.apache.org/jserv/protocol/AJPv21.html |archive-date=2003-08-04}} but the version 1.0 specification was published later on July 29, 1998.{{cite web |last1=Kosut |first1=Alexei |title=Apache JServ Protocol Version 1.0 |date=July 29, 1998 |work=Java Apache Project |url=http://java.apache.org/jserv/protocol/AJPv1.html |archive-url=https://web.archive.org/web/20030415202643/http://java.apache.org/jserv/protocol/AJPv1.html |archive-date=2003-04-15}} He also wrote the first implementations of it in the same month, with the releases of the Apache JServ servlet engine 0.9 and the Apache mod_jserv 0.9a (released on July 30, 1997).{{cite web |title=History of Changes - Apache JServ Project |work=Java Apache Project |url=http://java.apache.org/jserv/changes.html |archive-url=https://web.archive.org/web/20030416024540/http://java.apache.org/jserv/changes.html |archive-date=2003-04-16}}
The specification was updated to version 1.1 on September 9, 1998.{{cite web |last1=Kosut |first1=Alexei |title=Apache JServ Protocol Version 1.1 |date=September 9, 1998 |work=Java Apache Project |url=http://java.apache.org/jserv/protocol/AJPv11.html |archive-url=https://web.archive.org/web/20030804080332/http://java.apache.org/jserv/protocol/AJPv11.html |archive-date=2003-08-04}} Also in 1998, a revamped protocol was created and published in specification versions 2{{cite web |last1=Kluft |first1=Ian |last2=Korthof |first2=Ed |last3=Mazzocchi |first3=Stefano |title=Apache JServ Protocol Version 2 |date=February 15, 1998 |work=Java Apache Project |url=http://java.apache.org/jserv/protocol/AJPv2.html |archive-url=https://web.archive.org/web/20030805035548/http://java.apache.org/jserv/protocol/AJPv2.html |archive-date=2003-08-05}} and 2.1, however it was never adopted.
In 1999, Sun Microsystems donated their JavaServer Web Development Kit (JSWDK; codenamed Tomcat) reference implementation to Apache Software Foundation. This became Apache Tomcat version 3.0, the successor to JSWDK 2.1, and derailed further development of Apache JServ servlet engine and AJP towards support of Java servlet API version 2.1.{{cite web |title=The Origin Story of Tomcat |url=https://technotif.com/the-origin-story-of-tomcat/ |website=TechNotif |access-date=2018-07-25}}
The current specification remains at version 1.3,{{cite web |title=AJP Protocol Reference - AJPv13 |work=Apache Tomcat |url=https://tomcat.apache.org/connectors-doc/ajp/ajpv13a.html |access-date=2016-08-20}} however there is a published extension proposal{{cite web |title=AJP Protocol Reference - AJPv13 Extension Proposal |work=Apache Tomcat |url=https://tomcat.apache.org/connectors-doc/ajp/ajpv13ext.html |access-date=2016-08-20}} as well as an archived experimental 1.4 proposal.{{cite web |title=AJPv14 Proposal |work=Apache Tomcat |url=https://archive.apache.org/dist/tomcat/tomcat-connectors/jk2/v2.0.0/doc/common/AJPv14-proposal.html |access-date=2019-05-06}}
See also
References
{{Reflist}}
External links
- [http://tomcat.apache.org/connectors-doc/ajp/ajpv13a.html The Apache Tomcat Connector - AJP Protocol Reference] AJPv13
- [http://tomcat.apache.org/tomcat-3.3-doc/AJPv13.html Apache JServ Protocol version 1.3] Dan Milstein, December 2000.
- {{cite web | title=BonCode Connector | website=BonCode | date=2016-08-16 | url=http://www.boncode.net/boncode-connector | access-date=2017-10-09}} BonCode IIS implementation of AJP
{{Web interfaces}}