Develop Reference

Slack Interactive Messages: POST request payload has an unexpected format

I'm getting a POST request inside a Flask app from Slack. The request is sent when a user presses on an interactive message button. According to Slack docs I must extract the body of the request to verify the signature.
My computed signature doesn't match the one sent by Slack, though.
In fact, the body of the request comes as some encoded string. The string is actually an encoded dictionary instead of a query str parameters, as expected.
Here's the beginning of my view:
#app.route('/register', methods=['POST'])
def register_visit():
data = request.get_data()
signature = request.headers.get('X-Slack-Signature', None)
timestamp = request.headers.get('X-Slack-Request-Timestamp', None)
signing_secret = b'aaaaaaaaaaaaaaaa'
# old message, ignore
if round(actual_time.time() - float(timestamp)) > 60 * 5:
return
concatenated = ("v0:%s:%s" % (timestamp, data)).encode('utf-8')
computed_signature = 'v0=' + hmac.new(signing_secret, msg=concatenated, digestmod=hashlib.sha256).hexdigest()
if hmac.compare_digest(computed_signature, signature):
...
I've tried to format the received data to make it look like:
token=fdjkgjl&user_id=1234... but I am not aware of all of the necessary parameters that have to be present in the data.
Any ideas are highly appreciated.
The body of the message is following - after being URL decoded (note I've modified possibly sensitive data):
b'payload={"type":"interactive_message","actions":
[{"name":"yes_button","type":"button","value":"236"}],"callback_id":"visit_button","team":{"id":"fffff","domain":"ffff"},"channel":{"id":"ffff","name":"directmessage"},"user":{"id":"ffffff","name":"fffft"},"action_ts":"1540403943.419120","message_ts":"1541403949.000100","attachment_id":"1","token":"8LpjBuv13J7xAjhl2lEajoBU","is_app_unfurl":false,"original_message":{"text":"Test","bot_id":"DDDDDDDDD","attachments":[{"callback_id":"visit_button","text":"Register","id":1,"color":"3AA3E3","actions":[{"id":"1","name":"yes_button","text":"Yes","type":"button","value":"236","style":""}],"fallback":"Register"}],"type":"message","subtype":"bot_message","ts":"1540413949.000100"},"response_url":"https://hooks.slack.com/actions/ffffff/ffffff/tXJjx1XInaUhrikj6oEzK08e","trigger_id":"464662548327.425084163429.dda35a299eedb940ab98dbb9386b56f0"}'

The reason you are getting the "garbled" data is that you are using request.get_data(). That method will return the raw data of a request, but not do any decoding for you.
Much more convenient is to use request.form.get('payload'), which will directly give you the JSON string of the request object. You can then convert that into a dict object with json.loads() to process it further in your app.
Note that the format you received is the correct format for interactive messages. You will not get a query string (e.g. "token=abc;user_id?def...") as you suggested (like for slash command requests). Interactive message request will always contain the request as JSON string in a payload form property. See here for reference.
Here is a simple working example, which will reply a greeting to the user that pressed the button. It will work directly with Slack, but I recommend using Postman to test it.
#app.py
from flask import Flask, request #import main Flask class and request object
import json
app = Flask(__name__) #create the Flask app
#app.route('/register', methods=['POST'])
def register_visit():
slack_req = json.loads(request.form.get('payload'))
response = '{"text": "Hi, <#' + slack_req["user"]["id"] + '>"}'
return response, 200, {'content-type': 'application/json'}
if __name__ == '__main__':
app.run(debug=True, port=5000) #run app in debug mode on port 5000

OK, the issue wasn't related to how Slack sends me the message. It was about misunderstanding which data comes as bytes and which data is unicode. The culprit was string formatting in my case - the line concatenated = ("v0:%s:%s" % (timestamp, data)).encode('utf-8') should have been concatenated = (b"v0:%b:%b" % (timestamp.encode("utf-8"), data)). Data is already bytes, timestamp meanwhile is unicode.
Cannot believe I've banged my head on this for hours -_-
#app.route('/register', methods=['POST'])
def register_visit():
data = request.get_data()
signature = request.headers.get('X-Slack-Signature', None)
timestamp = request.headers.get('X-Slack-Request-Timestamp', None)
signing_secret = b'aaaaaaaaaaaaaaaa'
# old message, ignore
if round(actual_time.time() - float(timestamp)) > 60 * 5:
return
concatenated = (b"v0:%b:%b" % (timestamp.encode("utf-8"), data))
computed_signature = 'v0=' + hmac.new(signing_secret, msg=concatenated,
digestmod=hashlib.sha256).hexdigest()
if hmac.compare_digest(computed_signature, signature):
...

This worked for me
from urllib import parse
parsed_text = parse.unquote('your bytes text here')

Catch http-status code in Flask

I lately started using Flask in one of my projects to provide data via a simple route. So far I return a json file containing the data and some other information. When running my Flask app I see the status code of this request in terminal. I would like to return the status code as a part of my final json file. Is it possible to catch the same code I see in terminal?
Some simple might look like this
from flask import Flask
from flask import jsonify
app = Flask(__name__)
#app.route('/test/<int1>/<int2>/')
def test(int1,int2):
int_sum = int1 + int2
return jsonify({"result":int_sum})
if __name__ == '__main__':
app.run(port=8082)
And in terminal I get:

You are who set the response code (by default 200 on success response), you can't catch this value before the response is emited. But if you know the result of your operation you can put it on the final json.
#app.route('/test/<int1>/<int2>/')
def test(int1, int2):
int_sum = int1 + int2
response_data = {
"result": int_sum,
"sucess": True,
"status_code": 200
}
# make sure the status_code on your json and on the return match.
return jsonify(response_data), 200 # <- the status_code displayed code on console
By the way if you access this endpoint from a request library, on the response object you can find the status_code and all the http refered data plus the json you need.
Python requests library example
import requests
req = requests.get('your.domain/test/3/3')
print req.url # your.domain/test/3/3
print req.status_code # 200
print req.json() # {u'result': 6, u'status_code: 200, u'success': True}

You can send HTTP status code as follow:
#app.route('/test')
def test():
status_code = 200
return jsonify({'name': 'Nabin Khadka'}, status_code) # Notice second element of the return tuple(return)
This way you can control what status code to return to the client (typically to web browser.)

Creating POST request in python, need to send data as multipart/form-data?

I'm in the process of writing a very simple Python application for a friend that will query a service and get some data in return. I can manage the GET requests easily enough, but I'm having trouble with the POST requests. Just to get my feet wet, I've only slightly modified their example JSON data, but when I send it, I get an error. Here's the code (with identifying information changed):
import urllib.request
import json
def WebServiceClass(Object):
def __init__(self, user, password, host):
self.user = user
self.password = password
self.host = host
self.url = "https://{}/urldata/".format(self.host)
mgr = urllib.request.HTTPPasswordMgrWithDefaultRealm()
mgr.add_password(None, "https://{}".format(self.host), self.user, self.password)
self.opener = urllib.request.build_opener(urllib.request.HTTPDigestAuthHandler(mgr))
username = "myusername"
password = "mypassword"
service_host = "thisisthehostinfo"
web_service_object = WebServiceClass(username, password, service_host)
user_query = {"searchFields":
{
"First Name": "firstname",
"Last Name": "lastname"
},
"returnFields":["Entity ID","First Name","Last Name"]
}
user_query = json.dumps(user_query)
user_query = user_query.encode("ascii")
the_url = web_service_object.url + "modules/Users/search"
try:
user_data = web_service_object.opener.open(the_url, user_query)
user_data.read()
except urllib.error.HTTPError as e:
print(e.code)
print(e.read())
I got the class data from their API documentation.
As I said, I can do GET requests fine, but this POST request gives me a 500 error with the following text:
Content type 'application/x-www-form-urlencoded;charset=UTF-8' not supported
In researching this error, my assumption has become that the above error means I need to submit the data as multipart/form-data. Whether or not that assumption is correct is something I would like to test, but stock Python doesn't appear to have any easy way to create multipart/form-data - there are modules out there, but all of them appear to take a file and convert it to multipart/form-data, whereas I just want to convert this simple JSON data to test.
This leads me to two questions: does it seem as though I'm correct in my assumption that I need multipart/form-data to get this to work correctly? And if so, do I need to put my JSON data into a text file and use one of those modules out there to turn it into multipart, or is there some way to do it without creating a file?

Maybe you want to try the requests lib, You can pass a files param, then requests will send a multipart/form-data POST instead of an application/x-www-form-urlencoded POST. You are not limited to using actual files in that dictionary, however:
import requests
response = requests.post('http://httpbin.org/post', files=dict(foo='bar'))
print response.status_code
If you want to know more about the requests lib, and specially in sending multipart forms take a look at this:
http://docs.python-requests.org/en/master/
and
http://docs.python-requests.org/en/master/user/advanced/?highlight=Multipart-Encoded%20Files

handle http post request with json by python script on iis

i have trouble handling http post request with JSON as body of the request.
i am running IIS with python as server script.
this is the code that makes request:
var http = new XMLHttpRequest();
var url = "http://myurl.ext/py/script.py";
http.onreadystatechange = function() {
if(http.readyState == 4 && http.status == 200) {
console.log(http.responseText);
}
}
data = {"field":"value", "number":5}
http.open('POST', url, true);
http.setRequestHeader('Content-Type', 'application/json; charset=UTF-8');
http.send(JSON.stringify(data));
on server side i have:
import cgi
import http.client
print("Content-Type: text/text")
print("")
print(cgi.parse())
print(http.client.HTTPResponse)
cgi.parse() gives empty string
http.client.HTTPResponse gives empty string
cgi.FieldStorage() gives empty string, but if i submit a form, it returns values of the input fields.
i want to send JSON data in the background to the script and return some processed values as JSON as well.

The cgi module is designed primarily with form processing from a POST request, or query string parsing from a GET request, in mind. As such it does not really provide much that might help you process a JSON request.
Keep in mind that all the CGI script does is read data from the process' environment and its standard input. Thus you can just read the body of the POST from sys.stdin:
#!/usr/bin/env python3
import sys
import json
from pprint import pprint
print('Content-Type: text/plain')
print()
try:
data = json.load(sys.stdin)
print("Received:")
pprint(data)
except json.JSONDecodeError as exc:
print('Failed to decode JSON request: {}'.format(exc))
All this script does is to decode the standard input as JSON and pretty print it back out in the response.
You might be better off looking at something more usable such as flask, bottle, etc.

to make it work you have to explicitly tell how much to read.
data = "";
if int(os.environ.get('CONTENT_LENGTH', 0)) != 0:
for i in range(int(os.environ.get('CONTENT_LENGTH', 0))):
data += sys.stdin.read(1)
print(data)
this what worked for me

Why can't I decode a JSON message in the following situation?

I am trying to send a JSON message from a computer to another one via a post request.
The script which sends the message is the following:
message = {'station':'turn on'}
res = rest.send( 'POST', server_addr + "/newstation", json.dumps(message), {'Content-Type': 'application/json'} )
The rest.send(...) method should be correct as I used it before and it worked fine.
The PC which sends the post request runs Linux, while the receiving one runs Win 8, if that means anything.
On the receiving machine I have the following:
#app.route('/newstation', methods = ['POST'])
def new_station ():
j_data = request.get_json()
d = decode_data(j_data)
where decode_data(j_data) is the following
def decode_data(j_data):
d = json.loads(j_data)
return d
My problem is: whenever I try to send the post request from the first machine the response is "Internal server error" and on the machine with the server the error returned is "TypeError: expected string or buffer".
Now I am thinking that it may be a matter of encoding of the string.
The post request is received and I can print the json content without problems, the issue arises when I try to decode.

I fixed the issue, it was a mistake on my part (of course). I misunderstood the documentation.
#app.route('/newstation', methods = ['POST'])
def new_station ():
j_data = request.get_json()
#d = decode_data(j_data)
request.get_json() already returns me a dictionary, so the decode_data function isn't actually needed. I already have the result without the need for json.loads().