IdP Initiated

Prerequisites

• IdP-initiated federated identity authentication is supported by the enterprise IdP server.
• The beautifulsoup4 package of the Python module has been installed on the client.

Flowchart

The following figure shows the IdP-initiated federation authentication process.

Figure 1 Flowchart (IdP-initiated)

Description

1. The client calls the login link provided by IdP based on the IdP-initiated mode and sets the cloud platform address in the login link, that is, entityID in the metadata file of the cloud platform.
2. The client obtains the login page of the IdP. Users submit identity information to IdP for authentication through the client.
3. After users pass the authentication, IdP constructs an assertion carrying the user identity information and sends the SAML response. The response passes through the client.
4. The client encapsulates the SAML response, forwards the SAML response, and calls the API (federated token obtained in the IdP-initiated mode) provided by the cloud platform.
5. The cloud platform verifies and authenticates the assertion, and generates a temporary access credential according to the identity conversion rule configured by users in the identity provider.
6. Users can access cloud resources according to their permissions.

Implementation on the Client

1. Configure the login URL of enterprise IdP.

   Table 1 Login URLs of common IdP products

   IdP	SP Identification Parameter in URL	Login URL Example
   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

   After the configuration, enter the login URL in the browser address box. The following page is displayed.

   Figure 2 Login Page
   
   Client4ShibbolethIdP script implementation:

   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. The client submits authentication information. The client parses the login page using the beautifulsoup4 module, captures the user information input box and requested action, constructs the request parameters, and initiates identity authentication to the IdP.

   Obtain all form data submitted for the login page from the browser.

   Figure 3 Authentication information (1)
   

   Client4ShibbolethIdP script implementation:

   # 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. The client parses the next page. (Some enterprise IdPs provide pages containing user attributes.)

   Obtain all form data submitted for the login page from the browser.

   Figure 4 Authentication information (2)
   

   Client4ShibbolethIdP script implementation:

   # 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. The client parses the response message sent from the IdP. The client submits user information to the enterprise IdP for authentication. After authenticating the user information, the IdP sends a response message to the client. The client parses the SAMLResponse parameter in the response message.

   Client4ShibbolethIdP script implementation:

   # 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. Obtain an unscoped token. For details, see Obtaining an Unscoped Token (IdP Initiated).

   Client4ShibbolethIdP script implementation:

   # 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. Obtain a scoped token. For details, see Obtaining a Scoped Token.

   Client4ShibbolethIdP script implementation:

   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. Obtain a temporary AK/SK.

   Client4ShibbolethIdP script implementation:

   # 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