更新时间:2022-03-15 GMT+08:00
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IdP initiated方式

本章以“Client4ShibbolethIdP”脚本为例,介绍IdP initiated方式获取联邦认证Token的方法。“Client4ShibbolethIdP”脚本模拟用户在浏览器上登录企业IdP系统,通过呈现浏览器提交的表单数据和客户端实现的对比,帮助用户开发本企业IdP系统的客户端脚本。

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公有云的地址,即公有云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,调用公有云提供的“通过IdP initiated方式获取联邦token”接口。
  5. 公有云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公有云资源。

客户端实现

“Client4ShibbolethIdP.py”脚本(仅供参考),实现本企业IdP到本系统的API/CLI侧联邦认证的脚本。

脚本下载地址:https://obs-iam-download01.obs.cn-north-1.myhwclouds.com/non-ecp-script/Client4ShibblethIdP.py

  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

  1. 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)

  2. 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)

  3. 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)

  4. 获取Unscoped token。参考IdP initiated方式

    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

  5. 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://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. 获取临时访问密钥。参考通过token获取临时访问密钥和securitytoken

    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://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

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