There OAuth to be a better way (Power BI)

Edit: The base URL has changed from https://api.powerbi.com/beta/myorg to https://api.powerbi.com/v1.0/myorg

OAuth is clearly becoming the de-facto standard for authenticating API calls around the web. In the business intelligence arena, while we can discuss its pros and cons, we undoubtedly must get acquainted with it because sooner or later we’ll be tasked with importing data from one of the many “OAuth protected” web services.

In this third release of the OAuth series I’ll show how to get an Access Token from Microsoft Power BI. The same procedure can be used for many other Azure services (by changing the appropriate scope in the resource parameter).

Our typical scenario would be an unattended server process downloading data; I’m using a headless Linux box with cURL and jq.

You can see here and here my previous posts about how to use cURL to authenticate with flickr or BigQuery and make API calls with an Access Token.

The way Azure works is a little different. You get an Access Token valid for 1 hour and a Refresh Token. You can reuse the Access Token for as many calls as you want during the hour, and then you’ll need to ask for a new Access Token presenting the Refresh Token.

Prerequisites:

  • An Azure subscription with a real work domain (no personal account)

loginazure

  • An Azure Active Directory so you can add users to @yourdomain

azuread

  • A Power BI subscription with a user belonging to your Azure Active Directory

azure users

Once you have the requisites in place, follow this article to create an app and get a Client ID.

clientid

With the username, password and the Client ID you can use this script to get an Access Token:

[code language=”bash” gutter=”true” light=”false”]
#!/bin/bash

OAUTH_CLIENT_ID="yourClientId"
OAUTH_USERNAME="youruser@yourdomain.com"
OAUTH_PASSWORD="yourpassword"

POST_RESULT="$(curl -s -X POST -d "resource=https://analysis.windows.net/powerbi/api&client_id="$OAUTH_CLIENT_ID"&grant_type=password&username="$OAUTH_USERNAME"&password="$OAUTH_PASSWORD"&scope=openid" "https://login.windows.net/common/oauth2/token" | jq -r .)"

REFRESH_TOKEN="$(echo ${POST_RESULT} | /usr/local/bin/jq -r .refresh_token)"
ACCESS_TOKEN="$(echo ${POST_RESULT} | /usr/local/bin/jq -r .access_token)"
AUTH_HEADER="Authorization: Bearer ${ACCESS_TOKEN}"
echo "${AUTH_HEADER}"

echo "${AUTH_HEADER}" > ./auth_header.txt
echo "${REFRESH_TOKEN}" > ./refresh_token.txt

[/code]

This script will save two files: one is the Authorization Header and the other is the Refresh Token. You will use the Authorization Header passing it to every API call that you make (during 1 hour), for example to get a list of the available datasets in your Power BI storage use:

[code language=”bash” gutter=”true” light=”false”]
#!/bin/bash

AUTH_HEADER=$(<./auth_header.txt)
curl -k -s "https://api.powerbi.com/beta/myorg/datasets" -H "$AUTH_HEADER" | /usr/local/bin/jq -r .

[/code]

After an hour or so, you will ask for a new Access Token and store the new Authorization Header (can also be crontabbed every nn minutes):

[code language=”bash” gutter=”true” light=”false”]
#!/bin/bash

REFRESH_TOKEN=$(<./refresh_token.txt)
OAUTH_CLIENT_ID="yourClientId"
OAUTH_USERNAME="youruser@yourdomain.com"
OAUTH_PASSWORD="yourpassword"

POST_RESULT="$(curl -k -s -X POST -d "resource=https://analysis.windows.net/powerbi/api&client_id="$OAUTH_CLIENT_ID"&grant_type=refresh_token&username="$OAUTH_USERNAME"&password="$OAUTH_PASSWORD"&scope=openid&refresh_token=${REFRESH_TOKEN}" "https://login.windows.net/common/oauth2/token" | jq -r .)"

REFRESH_TOKEN="$(echo ${POST_RESULT} | /usr/local/bin/jq -r .refresh_token)"
ACCESS_TOKEN="$(echo ${POST_RESULT} | /usr/local/bin/jq -r .access_token)"

AUTH_HEADER="Authorization: Bearer ${ACCESS_TOKEN}"

echo "${AUTH_HEADER}"
echo "${AUTH_HEADER}" > ./auth_header.txt
echo "${REFRESH_TOKEN}" > ./refresh_token.txt

[/code]

So, no browser, no GUI, no problem!

Microsoft Power BI to be generally available on July, 24 2015

Few days ago microsoft announced that the preview phase of Power BI is now over and the product will be launched later this month.

The Power BI that was available in SharePoint and Office 365 will be superseded. This means that Power View (the Silverlight powered dashboard) will cease to exist.

<my personal note>Given that Microsoft recently aquired DATAZEN, I suppose this Power BI will also have a very short life-span.</my personal note>

It will feature a Desktop component and a cloud based hosting service. Free accounts for up to 1GB of data.

It will be able to access both on-premise and cloud data and more connectors will be added after the launch. One point worth noting is that Microsoft released the code of the visualizations on GitHub, allowing developers to add their own D3.js (or other javascript) based charts under MIT license. This means that we could write plug-ins to embed into Power BI, but I have no clear idea whether we’ll be able to embed Power BI functionalities in our own web pages/applications.

What is your overall impression with this new BI tool?

Please answer a couple of questions here: https://www.surveymonkey.com/r/W8VTBS7

Some like it OAth (BigQuery)

Second issue of the series about OAuth (you can see the previous here). I’ll try to explain how to use the Google OAuth 2.0 mechanism to authorize a server side scripts without the need of the user’s credentials, in order to automate the INSERT or SELECT (or WHATEVER) processes.

I am testing this with BigQuery service, so in another post I’ll be able to get data from the sample datasets provided by Google.

Prerequisites:

First we need to enable BigQuery for our project (go create one if you don’t have one):

  1. enable google api
  2.  bigquery api

When we click on the Enabled APIs tab, we should see it listed:

bigquery api enabled

Go to APIs & auth / Credentials section on the left and Create new Client ID with the Service account option:

service account

Your browser will download a json file, that you should copy it in a safe place, but we’re not going to use it.

email address

note down the Email address that was generated for your Client ID.

You’ll need to generate also a P12 file, by clicking on the Generate new P12 key button, and download it:

p12 key

notice the pass-phrase for the P12 file (by default is notasecret).

Suppose the downloaded P12 file is named tutorial.p12. We will convert this P12 file to a PEM by issuing this command in a terminal console:

[code language=”bash” gutter=”true” light=”false”]
openssl pkcs12 -passin pass:notasecret -in tutorial.p12 -nocerts -nodes -out tutorial.pem
[/code]

this will remove the pass-phrase from the P12 file and generate a tutorial.pem that we can use with openssl.

Next step is to get an Access Token from Google with a JSON Web Token (JWT): we create the JWT with the Email address above plus some boilerplate constants. I’m not going into details on how the JWT is generated, but it is essentially a base64 encoded string composed by a header, a claim set and a signature; the signature is a little more tricky as it is calculated using SHA-256 hashing algorithm and has the characters forward slash [/] and underscore [_] substituted respectively with plus [+] and minus [-] signs. See documentation here. The JWT is finally sent via a HTTP POST call to https://www.googleapis.com/oauth2/v3/token.

here is the complete bash script, please change the EMAIL_ADDRESS variable with the appropriate value:

[code language=”bash” gutter=”true” light=”false”]

#!/bin/bash

JWT_HEADER="$(echo -n ‘{"alg":"RS256","typ":"JWT"}’ | /usr/bin/openssl base64 -A -e)"
#echo JWT_HEADER=$JWT_HEADER

EMAIL_ADDRESS="11327003054-us……………..g@developer.gserviceaccount.com"

JWT_CLAIM_SET="$(echo -n "{"iss":"$EMAIL_ADDRESS","scope":"https://www.googleapis.com/auth/bigquery.readonly","aud":"https://www.googleapis.com/oauth2/v3/token","exp":"$(($(date +%s)+3600))","iat":"$(date +%s)"}" | /usr/bin/openssl base64 -A -e  | /bin/sed ‘s/=//g’)"
#echo JWT_CLAIM_SET=$JWT_CLAIM_SET

JWT_SIGNATURE_INPUT=$JWT_HEADER.$JWT_CLAIM_SET
#echo JWT_SIGNATURE_INPUT=$JWT_SIGNATURE_INPUT

JWT_SIGNATURE="$(echo -n $JWT_SIGNATURE_INPUT | /usr/bin/openssl sha -sha256 -sign tutorial.pem | /usr/bin/openssl base64 -A -e | /bin/sed ‘s/=//g’ | /usr/bin/tr ‘/+’ ‘_-‘)"
#echo JWT_SIGNATURE=$JWT_SIGNATURE

JWT=$JWT_HEADER.$JWT_CLAIM_SET.$JWT_SIGNATURE
#echo JWT=$JWT

/usr/bin/curl -s -d "grant_type=urn:ietf:params:oauth:grant-type:jwt-bearer&assertion="$JWT -X POST "https://www.googleapis.com/oauth2/v3/token" | /usr/bin/jq -r .access_token

[/code]

this script will output the Access Token retrieved from Google. The Access token is valid for 1 hour, you can store it in a text file and reuse for your API calls until it expires, then redo from start.

# standing on the shoulders of giants: thanks to http://superuser.com/questions/606953/bash-oauth-2-0-jwt-script-for-server-to-google-server-applications