IdP initiated方式

前提条件

• 企业IdP服务器支持IdP Initiated方式的联邦认证。
• 客户端需要安装python模块beautifulsoup4。

流程图

IdP initiated联邦认证的流程如下图所示。

图1 流程图（IdP initiated方式）

步骤说明

1. Client调用IdP提供的基于IdP initiated方式的登录链接，并在登录链接中设置云平台的地址，即云平台Metadata文件中的“entityID”。
2. Client获取IdP的登录页面，用户通过Client提交身份信息给IdP进行认证。
3. 用户认证成功后，IdP构建携带用户身份信息的断言发送SAML Response，请求经过中间媒介Client。
4. Client对SAML Response进行重新封装后转发SAML Response，调用云平台提供的“通过IdP initiated方式获取联邦token”接口。
5. 云平台对断言进行校验和认证，并根据用户在身份提供商配置的身份转换规则生成临时访问凭证。
6. 用户根据分配的权限访问云平台资源。

客户端实现

1. 配置企业IdP的登录连接。

   表1 常用IdP产品的登录URL

   IdP	URL中标记SP的参数	登录URL示例
   ADFS	logintorp	https://adfs-server.contoso.com/adfs/ls/IdpInitiatedSignon.aspx?logintorp=https://iam.example.com
   Shibboleth	providerId	https://idp.example.org/idp/profile/SAML2/Unsolicited/SSO?providerId=iam.example.com
   SimpleSAMLphp	spentityid	https://idp.example.org/simplesaml/saml2/idp/SSOService.php?spentityid=iam.example.com

   配置完成后，在浏览器里输入登录URL，浏览器会呈现如下登录页面：

   图2 登录页面
   
   Client4ShibbolethIdP脚本实现：

   import sys
   import requests
   import getpass
   import re
   from bs4 import BeautifulSoup
   from urlparse import urlparse
   
   # SSL certificate verification: Whether or not strict certificate
   # verification is done, False should only be used for dev/test
   sslverification = True
   
   # Get the federated credentials from the user
   print "Username:",
   username = raw_input()
   password = getpass.getpass()
   print ''
   
   session = requests.Session()
   
   # The initial url that starts the authentication process.
   idp_entry_url = 'https://idp.example.com/idp/profile/SAML2/Unsolicited/SSO?providerId=https://iam.example.com'
   
   # Programmatically get the SAML assertion,open the initial IdP url# and follows all of the HTTP302 redirects, and gets the resulting# login page
   formresponse = session.get(idp_entry_url, verify=sslverification)
   # Capture the idp_authform_submit_url,which is the final url after# all the 302s
   idp_authform_submit_url = formresponse.url

2. 客户端提交认证信息。客户端通过beautifulsoup4模块解析登录页面，捕获用户信息输入框、请求action，构造请求的参数，发起向IdP的身份认证。

   通过浏览器获取登录页面提交的所有表单数据。

   图3 认证信息（1）
   

   Client4ShibbolethIdP脚本实现：

   # Parse the response and extract all the necessary values in order to build a dictionary of all of the form values the IdP expects
   formsoup = BeautifulSoup(formresponse.text.decode('utf8'), "lxml")
   payload = {}
   
   for inputtag in formsoup.find_all(re.compile('(INPUT|input)')):
       name = inputtag.get('name', '')
       value = inputtag.get('value', '')
       if "username" in name.lower():
           payload[name] = username
       elif "password" in name.lower():
           payload[name] = password
       else:
           payload[name] = value
   
   for inputtag in formsoup.find_all(re.compile('(FORM|form)')):
       action = inputtag.get('action')
       if action:
           parsedurl = urlparse(idp_entry_url)
           idp_authform_submit_url = parsedurl.scheme + "://" + parsedurl.netloc + action
   
   # please test on browser first, add other parameters in payload
   payload["_eventId_proceed"] = ""
   
   formresponse = session.post(
       idp_authform_submit_url, data=payload, verify=sslverification)

3. 客户端解析下一页（部分企业IdP会有展示用户属性的页面）。

   通过浏览器获取登录页面提交的所有表单数据。

   图4 认证信息（2）
   

   Client4ShibbolethIdP脚本实现：

   # In shebbleth IdP v3, browser will show attributes page for user,# so we need parse the page
   formsoup = BeautifulSoup(formresponse.text.decode('utf8'), "lxml")
   payload = {}
   
   # Add other form data required from browser to payload
   _shib_idp_consentIds = []
   for inputtag in formsoup.find_all(re.compile('input')):
       name = inputtag.get("name")
       value = inputtag.get("value")
       if name == "_shib_idp_consentIds":
           _shib_idp_consentIds.append(value)
   payload["_shib_idp_consentIds"] = _shib_idp_consentIds
   payload["_shib_idp_consentOptions"] = "_shib_idp_rememberConsent"
   payload["_eventId_proceed"] = "Accept"
   
   # user can get the action url from the html file
   nexturl = "https://idp.example.com/idp/profile/SAML2/Unsolicited/SSO?execution=e1s2"
   
   for inputtag in formsoup.find_all(re.compile('(FORM|form)')):
       action = inputtag.get('action')
       if action:
           parsedurl = urlparse(idp_entry_url)
           nexturl = parsedurl.scheme + "://" + parsedurl.netloc + action
   
   response = session.post(
       nexturl, data=payload, verify=sslverification)

4. 客户端解析IdP的响应。客户端提交用户信息给企业IdP系统认证，IdP认证用户信息成功后，发送响应给客户端，客户端解析出SAMLResponse参数。

   Client4ShibbolethIdP脚本实现：

   # Decode the response and extract the SAML assertion
   soup = BeautifulSoup(response.text.decode('utf8'), "lxml")
   SAMLResponse = ''
   
   # Look for the SAMLResponse attribute of the input tag
   for inputtag in soup.find_all('input'):
       if (inputtag.get('name') == 'SAMLResponse'):
           SAMLResponse = inputtag.get('value')
   
   # Better error handling is required for production use.
   if (SAMLResponse == ''):
       print 'Response did not contain a valid SAML assertion, please troubleshooting in Idp side.'
       sys.exit(0)

5. 获取Unscoped token。参考获取联邦认证unscoped token(IdP initiated)

   Client4ShibbolethIdP脚本实现：

   # Set headers
   headers = {}
   headers["X-Idp-Id"] = "test_local_idp"
   
   # IAM API url: get unscoped token on IDP initiated mode
   sp_unscoped_token_url = "https://iam.example.com/v3.0/OS-FEDERATION/tokens"
   
   # Set form data
   payload = {}
   payload["SAMLResponse"] = SAMLResponse
   response = session.post(
       sp_unscoped_token_url, data=payload, headers=headers, verify=sslverification)
   
   # Debug only
   print(response.text)
   print "Status Code: " + str(response.status_code)
   if response.status_code != 201:
       sys.exit(1)
   
   unscoped_token = response.headers.get("X-Subject-Token") if "X-Subject-Token" in response.headers.keys() else None
   if unscoped_token:
       print ">>>>>>X-Subject-Token: " + unscoped_token

6. 获取Scoped token。参考获取联邦认证scoped token

   Client4ShibbolethIdP脚本实现：

   payload = {
       "auth": {
           "identity": {
               "methods": ["token"],
               "token": {
                   "id": unscoped_token
               }
           },
           "scope": {
               "project": {
                   "name": "{region_id}_test1"
               }
           }
       }
   }
   
   sp_scoped_token_url = "https://iam.example.com/v3/auth/tokens"
   
   response = session.post(
       sp_scoped_token_url, json=payload, verify=sslverification)
   
   # Debug only
   print "Status Code: " + str(response.status_code)
   if response.status_code != 201:
       print response.text
       sys.exit(1)
   
   scoped_token = response.text if response.status_code == 201 else None
   if scoped_token:
       print ">>>>>>Scoped Token:" + scoped_token

7. 获取临时访问密钥。

   Client4ShibbolethIdP脚本实现：

   # Set form data
   payload = {
       "auth": {
           "identity": {
               "methods": ["token"],
               "token": {
                   "duration_seconds": "900"
               }
           }
       }
   }
   
   # Set headers
   headers = {}
   headers["X-Auth-Token"] = unscoped_token
   
   sp_STS_token_url = "https://iam.example.com/v3.0/OS-CREDENTIAL/securitytokens"
   
   response = session.post(
       sp_STS_token_url, json=payload, headers=headers, verify=sslverification)
   
   # Debug only
   print "Status Code: " + str(response.status_code)
   if response.status_code != 201:
       print response.text
       sys.exit(1)
   
   sts_token = response.text if response.status_code == 201 else None
   if sts_token:
       print ">>>>>>STS Token:" + sts_token