如何在 python 中表示来自 postman 的 pm.request.body

Question

I want to hash a dictionary in python 2.7 to obtain the same result as I get in postman by calling pm.request body. The hashing method works correctly when I try with strings, but I can't get the body to hash the same. I'm using OrderedDictionary from collections package in python. I assumed that the pm.body.request would be a JSON but it does not seem to be the case.

pm-body

{
  "personNumber": "195012161930",
  "requestDescription": "Detta ar ett test",
  "verksamhetId": "1ac12a80-819a-42ca-bd51-97bd3e19c443",
  "stadsDelID": "f55a5bea-2398-11e9-8140-0e9ccdb68c09"
}

Pre-request script in PM

var hmacKey = 'c811f8ae-dd9f-4b15-9a09-97a09bdbb485'; 

var contentToHash = pm.request.body.raw;
var cryptoJs = require('crypto-js'); 
var hash = cryptoJs.HmacSHA256(contentToHash, hmacKey); 
var hashInBase64 = cryptoJs.enc.Base64.stringify(hash); 
  
console.log(hashInBase64 + " This is the result");

What I've tried in Python

        key = "c811f8ae-dd9f-4b15-9a09-97a09bdbb485"

        od = OrderedDict() 
        od['personNumber'] = "195012161111"
        od['requestDescription'] = "Detta ar ett test"
        od['verksamhetId'] = "1ac12a80-819a-42ca-bd51-97bd3e19c443"
        od['stadsDelID'] = "f55a5bea-2398-11e9-8140-0e9ccdb68c09"

        contentToHash = (json.dumps((od)))

        hash = hmac.new( key, (contentToHash), hashlib.sha256)
        
        baseHash = base64.b64encode(hash.digest())
        print(baseHash + " This is the result in Python")

        

This is the expected value for hashInBase64 after running the Pre-request script '25iZC8NycCILZJCGN9T2jachFANGD4HkLSp+8X0W/Jk='

Answer 1

Solution for your problem:

Python2:

from collections import OrderedDict
import json
import hmac
import hashlib
import base64

key = bytearray("c811f8ae-dd9f-4b15-9a09-97a09bdbb485","utf-8")

od = OrderedDict() 
od['personNumber'] = "195012161930"
od['requestDescription'] = "Detta ar ett test"
od['verksamhetId'] = "1ac12a80-819a-42ca-bd51-97bd3e19c443"
od['stadsDelID'] = "f55a5bea-2398-11e9-8140-0e9ccdb68c09"

contentToHash = json.dumps(od,indent=2,separators=(',', ': '))

contentToHash = contentToHash.replace("\n","\r\n")

print(repr(contentToHash))

hash = hmac.new( key, (contentToHash).encode('utf-8'), hashlib.sha256)

baseHash = base64.b64encode(hash.digest())
print(str(baseHash) + " This is the result in Python")

Python3:

from collections import OrderedDict
import json
import hmac
import hashlib
import base64

key = bytearray("c811f8ae-dd9f-4b15-9a09-97a09bdbb485","utf-8")

od = OrderedDict() 
od['personNumber'] = "195012161930"
od['requestDescription'] = "Detta ar ett test"
od['verksamhetId'] = "1ac12a80-819a-42ca-bd51-97bd3e19c443"
od['stadsDelID'] = "f55a5bea-2398-11e9-8140-0e9ccdb68c09"

contentToHash = json.dumps(od,indent="\r  ",separators=(',', ': '))

contentToHash=contentToHash.replace("\n\r","\r\n")
contentToHash = contentToHash.replace("\n}","\r\n}")

print(repr(contentToHash))

hash = hmac.new( key, (contentToHash).encode('utf-8'), hashlib.sha256)

baseHash = base64.b64encode(hash.digest())
print(str(baseHash) + " This is the result in Python")

Postman:

var hmacKey = 'c811f8ae-dd9f-4b15-9a09-97a09bdbb485'; 

var contentToHash = pm.request.body.raw;
console.log(JSON.stringify(contentToHash))
var cryptoJs = require('crypto-js'); 
var hash = cryptoJs.HmacSHA256(contentToHash, hmacKey); 
var hashInBase64 = cryptoJs.enc.Base64.stringify(hash); 
  
console.log(hashInBase64 + " This is the result"); 

The correct approach:

You should remove spaces to make it work across all applications:

pm.request.body doesn't return just the body content but the full body object with the content type

so you should use

pm.request.body.raw

But still this will have space in it, you can remove it using

JSON.stringify(JSON.parse(pm.request.body.raw))

Now the same space issue is there in the python code you can remove it using

contentToHash = json.dumps(od,separators=(',', ':'))

Python code:

from collections import OrderedDict
import json
import hmac
import hashlib
import base64

key = bytearray("c811f8ae-dd9f-4b15-9a09-97a09bdbb485","utf-8")

od = OrderedDict() 
od['personNumber'] = "195012161111"
od['requestDescription'] = "Detta ar ett test"
od['verksamhetId'] = "1ac12a80-819a-42ca-bd51-97bd3e19c443"
od['stadsDelID'] = "f55a5bea-2398-11e9-8140-0e9ccdb68c09"

contentToHash = json.dumps(od,separators=(',', ':'))

hash = hmac.new( key, (contentToHash).encode('utf-8'), hashlib.sha256)

baseHash = base64.b64encode(hash.digest())
print(str(baseHash) + " This is the result in Python")

Postman pre-request:

var hmacKey = 'c811f8ae-dd9f-4b15-9a09-97a09bdbb485'; 

var contentToHash = JSON.stringify(JSON.parse(pm.request.body.raw),null,null)

var cryptoJs = require('crypto-js'); 
var hash = cryptoJs.HmacSHA256(contentToHash, hmacKey); 
console.log(hash)
var hashInBase64 = cryptoJs.enc.Base64.stringify(hash); 
  
console.log(hashInBase64 + " This is the result");