IdP Initiated

Prerequisites

• Your IdP server supports IdP-initiated federated identity authentication.
• The Python library BeautifulSoup 4 has been installed on the client.

Flowchart

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

Figure 1 Flowchart (IdP-initiated)

Description

1. The client visits the login link provided by IdP for IdP-initiated login and sets the public cloud address (entityID in the metadata file of the cloud system) in the login link.
2. The client displays the IdP login page, allowing users to submit identity information to IdP for authentication.
3. After authenticating the user, IdP constructs an assertion carrying the user identity information and sends a SAML response to the client.
4. The client encapsulates the SAML response and forwards it to the cloud system to call the API used to obtain a federated token in the IdP-initiated mode.
5. The cloud system verifies and authenticates the assertion, and generates a temporary access credential according to the identity conversion rules of the user configured for the identity provider.
6. The user can access public cloud resources based on assigned permissions.

Implementation on the Client

This section uses the Client4ShibbolethIdP.py script to describe how to implement federated identity authentication for API/CLI access to the cloud system from an IdP.

You can download the script here:

https://obs-iam-download01.obs.cn-north-1.myhuaweicloud.com/non-ecp-script/Client4ShibblethIdP.py

1. Configure the login URL of the IdP.

   Table 1 Login URLs of common IdP products

   IdP	SP Parameter in URL	Example Login URL
   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 a login URL in the address bar of a browser. The following page is displayed.

   Figure 2 Login page
   
   Client4ShibbolethIdP script:

   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 uses Beautifulsoup 4 to capture the user information and requested action, and then constructs and sends an identity authentication request to the IdP.

   The client acquires all form data submitted through the login page.

   Figure 3 Authentication information (1)
   

     

   Client4ShibbolethIdP script:

   # 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 IdPs display a user attribute page.)

   The client acquires all form data submitted through the login page.

   Figure 4 Authentication information (2)
   

   Client4ShibbolethIdP script:

   # 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. If the authentication is successful, the client parses the SAML response sent by the IdP.

   Client4ShibbolethIdP script:

   # 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:

   # 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:

   payload = {
       "auth": {
           "identity": {
               "methods": ["token"],
               "token": {
                   "id": unscoped_token
               }
           },
           "scope": {
               "project": {
                   "name": "{region_id}_test1"
               }
           }
       }
   }
   
   sp_scoped_token_url = "https://10.120.171.90:31943/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 access key. For details, see Obtaining Temporary Access Keys and Security Tokens of an IAM User.

   Client4ShibbolethIdP script:

   # 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://10.120.171.90:31943/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