P3P是什么
P3P（Platform for Privacy Preferences）是W3C公布的一项隐私保护推荐标准，以为用户提供隐私保护。 P3P标准的构想是：Web 站点的隐私策略应该告之访问者该站点所收集的信息类型、信息将提供给哪些人、信息将被保留多少时间及其使用信息的方式，如站点应做诸如 “本网站将监测您所访问的页面以提高站点的使用率”或“本网站将尽可能为您提供更合适的广告”等申明。访问支持P3P网站的用户有权查看站点隐私报告，然 后决定是否接受cookie 或是否使用该网站。
利用P3P实现跨域
有别于JS跨域、IFRAME跨域等的常用处理办法，通过发送P3P头信息而实现的跨域。
PHP 使用P3P协议
header('P3P: CP="CURa ADMa DEVa PSAo PSDo OUR BUS UNI PUR INT DEM STA PRE COM NAV OTC NOI DSP COR"');
JS 使用P3P协议
xmlhttp.setRequestHeader( "P3P" , 'CP="CURa ADMa DEVa PSAo PSDo OUR BUS UNI PUR INT DEM STA PRE COM NAV OTC NOI DSP COR"' );
ASP.NET 使用P3P协议
HttpContext.Current.Response.AddHeader("p3p", "CP=\"IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT\"")
JSP 使用P3P协议
response.addHeader("P3P", "CP=IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT");
策略说明
(http://www.w3.org/2002/04/P3Pv1-header.html)
compact-policy-field = `CP="` compact-policy `"`
compact-policy = compact-token *(" " compact-token)
compact-token = compact-access |
compact-disputes |
compact-remedies |
compact-non-identifiable |
compact-purpose |
compact-recipient |
compact-retention |
compact-categories |
compact-test
compact-access = "NOI" | "ALL" | "CAO" | "IDC" | "OTI" | "NON"
compact-disputes = "DSP"
compact-remedies = "COR" | "MON" | "LAW"
compact-non-identifiable = "NID"
compact-purpose = "CUR" | "ADM" [creq] | "DEV" [creq] | "TAI" [creq] |
"PSA" [creq] | "PSD" [creq] | "IVA" [creq] | "IVD" [creq] |
"CON" [creq] | "HIS" [creq] | "TEL" [creq] | "OTP" [creq]
creq = "a" | "i" | "o"
compact-recipient = "OUR" | "DEL" [creq] | "SAM" [creq] | "UNR" [creq] |
"PUB" [creq] | "OTR" [creq]
compact-retention = "NOR" | "STP" | "LEG" | "BUS" | "IND"
compact-category = "PHY" | "ONL" | "UNI" | "PUR" | "FIN" | "COM" |
"NAV" | "INT" | "DEM" | "CNT" | "STA" | "POL" |
"HEA" | "PRE" | "LOC" | "GOV" | "OTC"
compact-test = "TST"
简洁策略
常用的简洁策略的 P3P头为 - P3P : CP=CAO PSA OUR
最简洁的写法是 P3P:CP=.
compact-access(访问): CAO - contact-and-other 允许第三方cookie的读写)
compact-purpose(目的): PSA - pseudo-analysis .目的就是做身份验证、分析
compact-recipient(受体): OUR - ours 声明使用相关信息的人是谁,ours 第三方自己
浏览器支持情况
| 浏览器 | 默认允许第三方Cookie | 是否支持P3P | 禁止第三方Cookie后,配置P3P简明策略头的效果 |
| IE6 | 否 | 是 | HTTP可读写Cookie JS可读Cookie 首次读到P3P头,JS无写Cookie权限.第二次才OK (第二次.直接Cache.也不行.除非第一次非Cache并读到p3p头.后面我会提到解决方案.) 应当避免JS的写操作 |
IE7-IE9 | 否 | 是 | HTTP、JS,可随意读写. |
| FireFox | 是 | 否 | HTTP、JS都不可读写 |
| Chrome | 是 | 部分支持,趋势-否 | 趋势为HTTP、JS可读不可写. |
| Safari | 否 | 否 | HTTP、JS可读不可写 可以借助借助Post提交表单,实现写操作. |
| Opera | 是 | 否 | JS可读写 HTTP可读不可写. |