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 who logs in to the enterprise IdP using a browser. Therefore, by comparing the form data submitted by the browser and the client implementation data, this section helps users develop the client scripts of their enterprise IdP.

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)
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Description

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.
The client obtains the login page of the IdP. Users submit identity information to IdP for authentication through the client.
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.
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.
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.
Users can access cloud resources according to their permissions.

Implementation on the Client

Download the Client4ShibbolethIdP.py script (for reference only) from the following website to implement the federated identity authentication script from the enterprise IdP to the API/CLI side of the cloud system:

https://obs-iam-download.obs.eu-de.otc.t-systems.com/non-ecp-script/Client4ShibblethIdP.py

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
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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

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)
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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)

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)
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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)

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)

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

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

Obtain a temporary AK/SK. For details, see Obtaining 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

Parent topic: Obtaining a Token in Federated Identity Authentication Mode