In Python you could write the code to interact with the ACI library directly without the need of a library. Yet the advantage of some of these libraries is that another person has provided a foundation that is easier to work with than going at it alone. The Requests Library is a very popular library available in Python that really helps you when doing REST calls using Python.

The best description for Requests is available on their site as: "Requests is the only Non-GMO HTTP library for Python, safe for human consumption."

Step 1 - Goto the home directory

Change to the top directory to modify your bash resource file.

cd ~

Step 2 - Set credentials as environment variables

In this lab we have been growing into different concepts. One area that we have been glossing over is security of your credentials. You should never hard code your credentials into your code, and we skipped this in the Ansible section. In this section we will show you how to set your credentials as environment variables. This is a best practice in the industry.

Why use environment variables? For starters is avoids your credentials to exist inside code that could eventualy be stored inside of an SCM like GIT. Removing passwords inside of a source code repository is a complicated task that even seasoned profesionals have a hard time doing. The second part is that it allows for control from pipelines as we saw earlier. Environment variables can be set in the pipeline software allowing for specific control of who can change network devices.

To accelerate the process of setting environment variables, we have created a script that will set the environment variables for you in the profile for the linux shell and then enable the environment variables for the current session.

cat << EOF >> ~/.bashrc

export APIC_USERNAME='aciproglab01'
export APIC_PASSWORD='cisco.123'
export APIC_IP='10.0.226.41'
EOF

Now that you have set the environment variables, you have to enable them for the current session. You can do this by executing the following command:

source ~/.bashrc

Step 3 - Create first file and edit

As we had mentioned we will be using this web based IDE. You have complete view of the files in the working directory ltrdcn-3225. From here you can create files in the different directories we will create for the different components in the lab.

To create a file you just use the IDE itself.

And name the file aci_auth.py

Building the Authentication Request script

For our simple request script we are going to just interact directly with the fabric. We have to get the request library imported into our script, and then work with the authentication to the ACI fabric like we did in the Postman section of the lab.

Step 4 - import request library

On the first line of aci_auth.py you will add:

import requests, json, os

This will import into our script the request library and the JSON library to be able to construct the ReST API calls to the ACI fabric.

Step 5 - Define python function to get aci tokens

You are going to now create a python function that we will call get_aci_token that will contain the code to get the token from the APIC controller. This function will be called from the main part of the script. This is a best practice in programming to have your code in functions that can be called from the main part of the script. This makes your code more modular and easier to read and understand.

The first part of the function will be to get the environment variables that we set earlier. This is done by using the os.environ method that is part of the Python standard library. This method will return a dictionary of all the environment variables that are set in the current session. You can then access the environment variables by using the key of the dictionary that is the name of the environment variable. In this case we are going to get the APIC IP, the APIC username and the APIC password.

import requests, json, os

def get_aci_token():
    apic_ip = os.environ["APIC_IP"] 
    apic_username = os.environ["APIC_USERNAME"]
    apic_password = os.environ["APIC_PASSWORD"] 

With thee you will then create a python dictionary that will be the structure that is required for REST request to the APIC in JSON format.

import requests, json, os


def get_aci_token():
    apic_ip = os.environ["APIC_IP"] 
    apic_username = os.environ["APIC_USERNAME"]
    apic_password = os.environ["APIC_PASSWORD"] 

    credentials = {'aaaUser':
                {'attributes':
                    {'name': apic_username, 'pwd': apic_password }
                }
        }

Step 6 - Build URL to reach ACI fabric

Now that you have the structure of the authentication request, you have to build the code to send the request to the APIC controller. The first thing is to set the base URL that we will use to make the request against the AAA object models of the fabric to gain a authentication token. For better results we will create two variables. base_url and login_url where we can append to that base string, base_url, with the specific object we want to reach in the fabric.

If you remember when we talked about the API, you can see the structure was like:

So what we do is set a variable to be the protocol, APIC host and the API that is standard across all references of the ACI fabric.

import requests, json, os


def get_aci_token():
    apic_ip = os.environ["APIC_IP"] 
    apic_username = os.environ["APIC_USERNAME"]
    apic_password = os.environ["APIC_PASSWORD"] 

    credentials = {'aaaUser':
                {'attributes':
                    {'name': apic_username, 'pwd': apic_password }
                }
        }

    apic_auth_url = "https://{}/api/aaaLogin.json".format(apic_ip)

Step 7 - Create request to the APIC controller

With the login_url built for this fabric, we have to convert the dictionary for the credentials information to JSON. Using the JSON library that is part of Python, we will take the dictionary that we built for Python and create a variable that will be called json_credentials that is what will be sent to the APIC in the REST request using the request library.

import requests, json, os


def get_aci_token():
    apic_ip = os.environ["APIC_IP"] 
    apic_username = os.environ["APIC_USERNAME"]
    apic_password = os.environ["APIC_PASSWORD"] 

    credentials = {'aaaUser':
                {'attributes':
                    {'name': apic_username, 'pwd': apic_password }
                }
        }

    apic_auth_url = "https://{}/api/aaaLogin.json".format(apic_ip)

    json_credentials = json.dumps(credentials)

With the credentials in JSON format, you can proceed to create the POST request to the ACI fabric. Whenever you make a request to a REST endpoint, you will get a response. The response will be in the form of a response object that will contain the response from the server. This response object will contain the status code of the response, the headers of the response and the body of the response.

"

import requests, json, os


def get_aci_token():
    apic_ip = os.environ["APIC_IP"] 
    apic_username = os.environ["APIC_USERNAME"]
    apic_password = os.environ["APIC_PASSWORD"] 

    credentials = {'aaaUser':
                {'attributes':
                    {'name': apic_username, 'pwd': apic_password }
                }
        }

    apic_auth_url = "https://{}/api/aaaLogin.json".format(apic_ip)

    json_credentials = json.dumps(credentials)

    response = requests.post(apic_auth_url, data=json_credentials, verify=False)

    return reponse

Step 8 - Call the function get_aci_token function.

Now that you have the function to get the token from the APIC controller, you can call the function from the main part of the script. This is done by simply calling the function by its name and then assigning the response object to a variable that you can then use to process the response from the APIC controller.

But there is a slight twist that we want to show you. Since we will want to use this code from other scripts, we have to make sure that the code is not executed when the script is imported. To achieve this we will use the if __name__ == "__main__": statement. This is a special variable in Python that is set to the name of the script when the script is executed. If the script is imported into another script, the __name__ variable will be set to the name of the script that is importing the script. This is a way to make sure that the code in the if __name__ == "__main__": statement is only executed when the script is executed and not when the script is imported into another script.

import requests, json, os


def get_aci_token():
    apic_ip = os.environ["APIC_IP"] 
    apic_username = os.environ["APIC_USERNAME"]
    apic_password = os.environ["APIC_PASSWORD"] 

    credentials = {'aaaUser':
                {'attributes':
                    {'name': apic_username, 'pwd': apic_password }
                }
        }

    apic_auth_url = "https://{}/api/aaaLogin.json".format(apic_ip)

    json_credentials = json.dumps(credentials)

    response = requests.post(apic_auth_url, data=json_credentials, verify=False)

    return reponse

if __name__ == "__main__":
    post_response = get_aci_token()
    print(post_response)

At this point make sure you have saved your file. Then, return to your Terminal window.You will now execute the script in the terminal. Make sure you are in the correct directory.

cd ~/ltrdcn-3225/requests

And then run the Python script.

python3 aci_auth.py

The output of the command should be similar to the following output:

InsecureRequestWarning: Unverified HTTPS request is being made. Adding certificate verification is strongly advised. See:
https://urllib3.readthedocs.io/en/latest/advanced-usage.html#ssl-warnings
InsecureRequestWarning)
<Response [200]>

The following table shows you just a couple of the various response codes to assist you understanding this concept.

The key in that output is going to be the proper Response code, that should be 200 for OK. Also as you can see we have the warning that the request is unverified. This is because the APIC controller has a self signed certificate that is not trusted by the requests library. Let's configure requests to ignore this warning.

Step 9 - Configure requests to ignore self signed certificate

import requests, json, os
from urllib3.exceptions import InsecureRequestWarning

def get_aci_token():
    apic_ip = os.environ["APIC_IP"] 
    apic_username = os.environ["APIC_USERNAME"]
    apic_password = os.environ["APIC_PASSWORD"] 

    credentials = {'aaaUser':
                {'attributes':
                    {'name': apic_username, 'pwd': apic_password }
                }
        }

    apic_auth_url = "https://{}/api/aaaLogin.json".format(apic_ip)

    json_credentials = json.dumps(credentials)

    requests.packages.urllib3.disable_warnings(category=InsecureRequestWarning)
    response = requests.post(apic_auth_url, data=json_credentials, verify=False)

    return reponse

if __name__ == "__main__":
    post_response = get_aci_token()
    print(post_response)

If you run the same script again, you will see that the warning is no longer present.

Step 10 - Extracting token from APIC Authentication response

In the response object created by the requests library is the authentication token that we are looking for to gain access to the APIC controller API. The simple print command that we did print(post_response) was to validate the response. You can extract more details on the response by simply doing a print to the same object but invoking the text method of the object print(post_response.text).

The output will be EXTENSIVE as the text of the response is printed in itself. You can make this change if you wish to see the output. If not you can jump straight to the code that we are interested in that would extract the token from the response directly. What we are looking for is the authentication token that is needed for you to issue commands into the ACI fabric in itself.

First, we have to take the response that the APIC sent back and convert that into a dictionary that Python can process. The response is in essence just text inside the response object of the request library. Using the json.loads command, the string response will be converted into a Python dictionary. At that point you can easily extract the login attributes field from the response to get the token.

Then you have to parse the object in return to extract the token. The response dictionary will look as follows (ordering of fields is different every time):

Return to your editor. To extract that value you have to select exactly the right position in the dictionary to get the value. In this case post_response_json['imdata'][0]['aaaLogin']['attributes']

import requests, json, os
from urllib3.exceptions import InsecureRequestWarning

def get_aci_token():
    apic_ip = os.environ["APIC_IP"] 
    apic_username = os.environ["APIC_USERNAME"]
    apic_password = os.environ["APIC_PASSWORD"] 

    credentials = {'aaaUser':
                {'attributes':
                    {'name': apic_username, 'pwd': apic_password }
                }
        }

    apic_auth_url = "https://{}/api/aaaLogin.json".format(apic_ip)

    json_credentials = json.dumps(credentials)

    requests.packages.urllib3.disable_warnings(category=InsecureRequestWarning)
    response = requests.post(apic_auth_url, data=json_credentials, verify=False)
    response_json = json.loads(response.text)
    login_attributes = response_json['imdata'][0]['aaaLogin']['attributes']

    return reponse

if __name__ == "__main__":
    post_response = get_aci_token()
    print(post_response)

With that you can extract the token directly as the token would be in login_attributes['token'] and we can built the cookie dictionary that will be needed for further connections. It is always good to correctly identify the variables. Since we are now just returning the cookie we will be needing for further connections, change the declaration name of the variable and also the references.

import requests, json, os
from urllib3.exceptions import InsecureRequestWarning

def get_aci_token():
    apic_ip = os.environ["APIC_IP"] 
    apic_username = os.environ["APIC_USERNAME"]
    apic_password = os.environ["APIC_PASSWORD"] 

    credentials = {'aaaUser':
                {'attributes':
                    {'name': apic_username, 'pwd': apic_password }
                }
        }

    apic_auth_url = "https://{}/api/aaaLogin.json".format(apic_ip)

    json_credentials = json.dumps(credentials)

    requests.packages.urllib3.disable_warnings(category=InsecureRequestWarning)
    response = requests.post(apic_auth_url, data=json_credentials, verify=False)
    response_json = json.loads(response.text)
    login_attributes = response_json['imdata'][0]['aaaLogin']['attributes']
    cookies = {}
    cookies['APIC-Cookie'] = login_attributes['token']

    return cookies

if __name__ == "__main__":
    apic_token = get_aci_token()
    print(apic_token)

With that, make sure you save your Python file again and return to your Terminal window. Then, execute the script and see the cookie definition.

python3 aci_auth.py

{'APIC-Cookie': u'IP2IOcGIqUuf3u7Jb3EItLeZDDRknypcQPruHzVV25p5iveE/nACcT2jiTV56G
N051ZU61WGhj21tAM5sb5uSzOUgzjtt2hntR5MV7+em6Fgj7CEkni+4bWjAVi/Hlw9czDJp2hCCj
oOjuqZ5MExCmqHw4RNR+PXFPxLaSn0csTY+W4Kpyn2mIsLfWwfsXqsLydk4i+iiHgsZNxxKxL0H1
Woj4e6cRdBFX37W7b6ZP/RJ0Wlz1hDEd6+D+yUQQnZ0BCYrtYBWvf8q6ZsiOoR6g=='}

And with that token, all future requests to the ACI fabric can be performed. The token will expire over time, but you can write your code in such a way that it can execute all the sequence of requests to the fabric using the same authentication token. Then when completed, that token can expire and you would re-execute the authentication code to refresh and get a new token.