Updated on 2023-07-05 GMT+08:00

IdP Initiated

This section uses the Client4ShibbolethIdP script as an example to describe how to obtain a federated authentication token in the IdP-initiated mode. The Client4ShibbolethIdP script simulates a user logging in to an IdP system using a browser, helping you to develop your own IdP client script.

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.myhwclouds.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

  1. 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)

  2. 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)

  3. 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)

  4. 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

  5. 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

  6. Obtain a temporary access key. For details, see Obtaining a Temporary Access Key and Security Token Through a Token.

    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