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oauth_authorization_code_flow.livemd

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Neil Berkman
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DocuSign OAuth2 Authorization Code Flow with Elixir

Introduction

Run in Livebook

This LiveBook demonstrates how to implement the OAuth2 Authorization Code Flow with the DocuSign Elixir SDK using the battle-tested oauth2 library. This flow is ideal for web applications where users need to grant permission for your application to access their DocuSign account.

The Authorization Code Flow is more secure than JWT impersonation for user-facing applications because:

  • Users grant permission explicitly through DocuSign’s consent screen
  • No need for admin pre-approval (like JWT impersonation requires)
  • Tokens can be refreshed without user interaction
  • Standard OAuth2 compliance
  • Uses proven OAuth2 library patterns 
IO.puts("Installing dependencies...")

# Suppress Tesla deprecation warnings
Application.put_env(:tesla, :disable_deprecated_builder_warning, true)

Mix.install([
  {:docusign, "~> 2.2.1"},
  {:kino, "~> 0.16.0"},
  {:bandit, "~> 1.7"}
])

IO.puts("✅ Dependencies installed successfully!")

OAuth Callback Server

Let’s start a simple web server to handle the OAuth callback:

# Create a shared state store for OAuth data
defmodule OAuthState do
  use Agent

  def start_link(_) do
    Agent.start_link(fn -> %{} end, name: __MODULE__)
  end

  def put(key, value) do
    Agent.update(__MODULE__, &Map.put(&1, key, value))
  end

  def get(key) do
    Agent.get(__MODULE__, &Map.get(&1, key))
  end
end

# Start the state store
{:ok, _} = OAuthState.start_link([])

defmodule OAuthCallbackServer do
  use Plug.Router

  plug(:match)
  plug(:dispatch)

  get "/auth/docusign/callback" do
    # Parse query parameters manually from query_string
    query_params = if conn.query_string && conn.query_string != "" do
      URI.decode_query(conn.query_string)
    else
      %{}
    end

    code = query_params["code"]
    state = query_params["state"]

    # Store the code in our shared state
    OAuthState.put(:code, code)
    OAuthState.put(:state, state)
    OAuthState.put(:received_at, DateTime.utc_now())

    send_resp(conn, 200, """
    
      DocuSign OAuth Callback
      
        
✅ Authorization Successful!

        
You can now close this window and return to LiveBook.

        
Authorization Code: #{String.slice(code || "none", 0, 20)}...

        
The code has been automatically captured for use in LiveBook.

        
          setTimeout(() => window.close(), 3000);
        
      
    
    """)
  end

  match _ do
    send_resp(conn, 404, "Not found")
  end
end

# Start the server
{:ok, _} = Bandit.start_link(plug: OAuthCallbackServer, port: 4000)

IO.puts("🚀 OAuth callback server started on http://localhost:4000")

OAuth2 Authorization Code Flow Overview

The OAuth2 Authorization Code Flow consists of these steps:

  1. Generate Authorization URL - Redirect user to DocuSign for consent
  2. User Grants Permission - User signs in and authorizes your app
  3. Receive Authorization Code - DocuSign redirects back with a code
  4. Exchange Code for Tokens - Trade the code for access/refresh tokens
  5. Use Tokens for API Calls - Make authenticated requests to DocuSign
  6. Refresh Tokens - Get new access tokens when they expire

Configuration

First, let’s set up our DocuSign OAuth2 configuration:

alias Kino.Input

# Set up input forms for OAuth configuration
client_id_input = Input.text("Integration Key",
  label: "Found in the DocuSign admin under Apps & Keys")
client_secret_input = Input.password("Client Secret",
  label: "Found in the DocuSign admin under Apps & Keys")
redirect_uri_input = Input.text("Redirect URI",
  label: "Must match what's configured in DocuSign admin",
  default: "http://localhost:4000/auth/docusign/callback")
is_sandbox_input = Input.checkbox("Use Sandbox", default: true)

# Display input forms individually for proper rendering
Kino.render(client_id_input)
Kino.render(client_secret_input)
Kino.render(redirect_uri_input)
Kino.render(is_sandbox_input)

Now let’s configure the DocuSign OAuth client:

# Get values from inputs
client_id = Kino.Input.read(client_id_input)
client_secret = Kino.Input.read(client_secret_input)
redirect_uri = Kino.Input.read(redirect_uri_input)
is_sandbox = Kino.Input.read(is_sandbox_input)

# Configure DocuSign application
Application.put_env(:docusign, :client_id, client_id)
Application.put_env(:docusign, :client_secret, client_secret)

# Debug: Check configuration
IO.puts("OAuth Configuration set:")
IO.puts("Integration Key: #{client_id}")
IO.puts("Client Secret: #{String.slice(client_secret, 0, 10)}...")
IO.puts("Redirect URI: #{redirect_uri}")
IO.puts("Is sandbox: #{is_sandbox}")
IO.puts("Hostname: will be auto-detected from account base URI")

Step 1: Generate Authorization URL

The first step is to create an OAuth2 client and generate an authorization URL where users can grant permission to your application:

# Create OAuth2 client
oauth_client = DocuSign.OAuth.AuthorizationCodeStrategy.client(
  redirect_uri: redirect_uri,
  scope: "signature"
)

# Generate the authorization URL with CSRF protection
state = "demo-state-#{:crypto.strong_rand_bytes(8) |> Base.encode16()}"
authorization_url = OAuth2.Client.authorize_url!(
  oauth_client,
  state: state
)

# Display the authorization URL with a clickable link
Kino.HTML.new("""

  
Step 1: User Authorization

  
Click this link to authorize the application in DocuSign:

  #{authorization_url}" target="_blank">
    🔐 Authorize DocuSign Access
  
  


  
    🔗 Full Authorization URL (click to expand)
    
      #{authorization_url}
    
  
  

  
    📝 What happens next:
    
    
      
  1. Click the authorization link above
    2. 
      
  2. Sign in to your DocuSign account
    3. 
      
  3. Review the permissions and click "ALLOW ACCESS"
    4. 
      
  4. You'll be redirected to your redirect URI with a code parameter
    5. 
      
  5. Copy the code value and paste it in the next section
    6. 
    

  

""")

Step 2: Authorization Code Input

After clicking the authorization link and granting permission, DocuSign will redirect you back to the callback server. The authorization code will be automatically captured:

# Check if we have a code from the callback
callback_code = OAuthState.get(:code)
callback_state = OAuthState.get(:state)
received_at = OAuthState.get(:received_at)

if callback_code do
  Kino.Markdown.new("""
  ## ✅ Authorization Code Received!

  **Code**: `#{String.slice(callback_code, 0, 30)}...`
  **State**: `#{callback_state}`
  **Received**: `#{received_at}`

  The authorization code has been automatically captured from the OAuth callback.
  """)
else
  Kino.Markdown.new("""
  ## ⏳ Waiting for Authorization...

  Please click the authorization link above and complete the OAuth flow.
  The authorization code will appear here automatically once you authorize.
  """)
end

Step 3: Exchange Authorization Code for Tokens

Now let’s exchange the authorization code for access and refresh tokens:

# Get the authorization code from the shared state
auth_code = OAuthState.get(:code)

# Create a frame to display the token exchange results
token_frame = Kino.Frame.new() |> Kino.render()

if auth_code do
  Kino.Frame.render(token_frame, Kino.Markdown.new("🔄 Exchanging authorization code for tokens..."))

  # Exchange the authorization code for tokens using OAuth2 library
  try do
    oauth_client_with_tokens = OAuth2.Client.get_token!(
      oauth_client,
      code: auth_code
    )

    # Store OAuth2 client for later use (in a real app, you'd store these securely)
    Process.put(:oauth_client, oauth_client_with_tokens)

    # Extract token information for display
    token = oauth_client_with_tokens.token
    expires_in = if token.expires_at do
      token.expires_at - System.system_time(:second)
    else
      "Unknown"
    end

    Kino.Frame.render(token_frame, Kino.Markdown.new("""
    ## ✅ Token Exchange Successful!

    Your authorization code has been successfully exchanged for OAuth tokens:

    - **Access Token**: `#{String.slice(token.access_token, 0, 30)}...`
    - **Refresh Token**: `#{if token.refresh_token, do: String.slice(token.refresh_token, 0, 30) <> "...", else: "Not provided"}`
    - **Token Type**: `#{token.token_type}`
    - **Expires In**: `#{expires_in}` seconds

    🎉 You can now use this OAuth2 client to make authenticated API calls to DocuSign!
    """))

  rescue
    error ->
      Kino.Frame.render(token_frame, Kino.Markdown.new("""
      ## ❌ Token Exchange Failed

      **Error**: `#{inspect(error)}`

      **Common causes:**
      - Authorization code has expired (they're only valid for a few minutes)
      - Authorization code has already been used
      - Redirect URI doesn't match what was used in the authorization step
      - Invalid client credentials

      **Solution**: Go back to Step 1 and generate a new authorization URL.
      """))
  end
else
  Kino.Frame.render(token_frame, Kino.Markdown.new("""
  ⏳ **Waiting for authorization code...**

  Please complete the authorization flow above and paste the authorization code here.
  """))
end

Step 4: Get User Information

Let’s use our OAuth tokens to get information about the authenticated user and their DocuSign accounts:

# Create frame for user info
user_info_frame = Kino.Frame.new() |> Kino.render()

# Check if we have OAuth2 client from the previous step
oauth_client = Process.get(:oauth_client)

if oauth_client do
  Kino.Frame.render(user_info_frame, Kino.Markdown.new("🔄 Fetching user information..."))

  # Get user info using the OAuth2 strategy
  try do
    user_info = DocuSign.OAuth.AuthorizationCodeStrategy.get_user_info!(oauth_client)

      # Display user information
      accounts_info = if user_info["accounts"] do
        user_info["accounts"]
        |> Enum.with_index(1)
        |> Enum.map(fn {account, index} ->
          is_default = Map.get(account, "is_default", "false")
          default_marker = if is_default == "true", do: " (Default)", else: ""

          """
          **Account #{index}#{default_marker}:**
          - Account ID: `#{account["account_id"]}`
          - Account Name: `#{account["account_name"]}`
          - Base URI: `#{account["base_uri"]}`
          """
        end)
        |> Enum.join("\n")
      else
        "No account information available"
      end

      Kino.Frame.render(user_info_frame, Kino.Markdown.new("""
      ## 👤 User Information Retrieved

      **User Details:**
      - **Name**: #{user_info["name"]}
      - **Email**: #{user_info["email"]}
      - **User ID**: `#{user_info["sub"]}`
      - **Created**: #{user_info["created"]}

      **DocuSign Accounts:**
      #{accounts_info}

      🎯 **Next**: We'll use the default account to create a DocuSign connection for API calls.
      """))

    # Store user info for next step
    Process.put(:user_info, user_info)

  rescue
    error ->
      Kino.Frame.render(user_info_frame, Kino.Markdown.new("""
      ## ❌ Failed to Get User Information

      **Error**: #{inspect(error)}

      This might indicate that your access token is invalid or expired.
      Please try refreshing the token or re-authorizing.
      """))
  end
else
  Kino.Frame.render(user_info_frame, Kino.Markdown.new("""
  ⏳ **Waiting for OAuth tokens...**

  Please complete the token exchange step above first.
  """))
end

Step 5: Create DocuSign Connection

Now let’s create a DocuSign connection using our OAuth tokens that we can use for API calls:

# Create frame for connection setup
connection_frame = Kino.Frame.new() |> Kino.render()

oauth_client = Process.get(:oauth_client)
user_info = Process.get(:user_info)

if oauth_client &amp;&amp; user_info do
  Kino.Frame.render(connection_frame, Kino.Markdown.new("🔄 Creating DocuSign connection..."))

  # Find the default account or use the first one
  default_account = user_info["accounts"]
    |> Enum.find(fn account -> Map.get(account, "is_default") == "true" end)

  default_account = default_account || List.first(user_info["accounts"])

  if default_account do
    account_id = default_account["account_id"]
    base_uri = "#{default_account["base_uri"]}/restapi"

    # Create DocuSign connection from OAuth2 client with auto-detection
    case DocuSign.Connection.from_oauth_client_with_detection(
      oauth_client,
      account_id: account_id,
      base_uri: base_uri,
      auto_detect_hostname: true  # Automatically set hostname based on base_uri
    ) do
      {:ok, conn} ->
        # Store connection for API usage
        Process.put(:docusign_connection, conn)

        Kino.Frame.render(connection_frame, Kino.Markdown.new("""
        ## ✅ DocuSign Connection Created!

        Successfully created a DocuSign connection using OAuth2.Client:

        - **Account ID**: `#{account_id}`
        - **Account Name**: `#{default_account["account_name"]}`
        - **API Base URI**: `#{base_uri}`
        - **Connection Type**: OAuth2 Authorization Code Flow (using oauth2 library)

        🚀 **Ready for API calls!** You can now use this connection with any DocuSign API function.
        """))

      {:error, reason} ->
        Kino.Frame.render(connection_frame, Kino.Markdown.new("""
        ## ❌ Failed to Create Connection

        **Error**: #{inspect(reason)}

        This is unexpected - please check your token and account information.
        """))
    end
  else
    Kino.Frame.render(connection_frame, Kino.Markdown.new("""
    ## ❌ No DocuSign Accounts Found

    The user information doesn't contain any DocuSign accounts. This might indicate:
    - The user doesn't have access to any DocuSign accounts
    - There's an issue with the OAuth scope or permissions

    Please check your DocuSign account access.
    """))
  end
else
  Kino.Frame.render(connection_frame, Kino.Markdown.new("""
  ⏳ **Waiting for tokens and user info...**

  Please complete the previous steps first.
  """))
end

Step 6: Test API Call - Get Account Information

Let’s test our OAuth connection by making an API call to get account information:

# Create frame for API test
api_test_frame = Kino.Frame.new() |> Kino.render()

conn = Process.get(:docusign_connection)
user_info = Process.get(:user_info)

if conn &amp;&amp; user_info do
  default_account = user_info["accounts"]
    |> Enum.find(fn account -> Map.get(account, "is_default") == "true" end)
  default_account = default_account || List.first(user_info["accounts"])

  account_id = default_account["account_id"]

  Kino.Frame.render(api_test_frame, Kino.Markdown.new("🔄 Testing API call..."))

  # Make an API call to get account information
  case DocuSign.Api.Accounts.accounts_get_account(conn, account_id) do
    {:ok, account_info} ->
      Kino.Frame.render(api_test_frame, Kino.Markdown.new("""
      ## ✅ API Call Successful!

      Successfully retrieved account information using OAuth connection:

      **Account Details:**
      - **Account Name**: #{account_info.accountName}
      - **Account ID**: `#{account_info.accountIdGuid}`
      - **Plan Name**: #{account_info.planName}
      - **External Account ID**: #{account_info.externalAccountId}
      - **Created Date**: #{account_info.createdDate}
      - **Suspension Status**: #{account_info.suspensionStatus}

      **Billing Information:**
      - **Billing Period**: #{account_info.billingPeriodStartDate} to #{account_info.billingPeriodEndDate}
      - **Payment Method**: #{account_info.paymentMethod}
      - **Envelope Unit Price**: #{account_info.envelopeUnitPrice}

      🎉 **OAuth Authorization Code Flow Complete!**

      Your application is now successfully authenticated with DocuSign using OAuth2 tokens and can make API calls on behalf of the user.
      """))

    {:error, %Tesla.Env{status: status, body: body}} ->
      Kino.Frame.render(api_test_frame, Kino.Markdown.new("""
      ## ❌ API Call Failed

      **Status**: #{status}
      **Response**: #{inspect(body)}

      This might indicate:
      - Access token has expired
      - Insufficient permissions
      - Account access issues
      """))

    {:error, reason} ->
      Kino.Frame.render(api_test_frame, Kino.Markdown.new("""
      ## ❌ API Call Error

      **Error**: #{inspect(reason)}

      There was an unexpected error making the API call.
      """))
  end
else
  Kino.Frame.render(api_test_frame, Kino.Markdown.new("""
  ⏳ **Waiting for DocuSign connection...**

  Please complete the connection setup step above first.
  """))
end

Step 7: Token Refresh (Optional)

OAuth access tokens expire (typically after 8 hours). Here’s how you can refresh them using the refresh token:

# Create frame for token refresh demo
refresh_frame = Kino.Frame.new() |> Kino.render()

oauth_client = Process.get(:oauth_client)

if oauth_client &amp;&amp; oauth_client.token &amp;&amp; oauth_client.token.refresh_token do
  refresh_button = Kino.Control.button("🔄 Refresh Access Token")
  Kino.render(refresh_button)

  Kino.listen(refresh_button, fn _ ->
    Kino.Frame.render(refresh_frame, Kino.Markdown.new("🔄 Refreshing access token..."))

    try do
      refreshed_client = OAuth2.Client.refresh_token!(oauth_client)

      # Store new OAuth2 client
      Process.put(:oauth_client, refreshed_client)

      new_token = refreshed_client.token
      expires_in = if new_token.expires_at do
        new_token.expires_at - System.system_time(:second)
      else
        "Unknown"
      end

      Kino.Frame.render(refresh_frame, Kino.Markdown.new("""
      ## ✅ Token Refresh Successful!

      Your access token has been refreshed:

      - **New Access Token**: `#{String.slice(new_token.access_token, 0, 30)}...`
      - **New Refresh Token**: `#{if new_token.refresh_token, do: String.slice(new_token.refresh_token, 0, 30) <> "...", else: "Same as before"}`
      - **Expires In**: `#{expires_in}` seconds

      💡 **Note**: Some OAuth providers rotate refresh tokens, meaning you get a new refresh token each time you refresh. Always use the latest tokens.
      """))

    rescue
      error ->
        Kino.Frame.render(refresh_frame, Kino.Markdown.new("""
        ## ❌ Token Refresh Failed

        **Error**: `#{inspect(error)}`

        **Common causes:**
        - Refresh token has expired
        - Refresh token has been revoked
        - Invalid client credentials

        **Solution**: The user will need to re-authorize through the full OAuth flow.
        """))
    end
  end)

  Kino.Frame.render(refresh_frame, Kino.Markdown.new("""
  ## 🔄 Token Refresh

  Click the button above to refresh your access token using the refresh token.

  **When to refresh:**
  - Before the access token expires (typically 8 hours)
  - When you receive 401 Unauthorized responses
  - As part of a scheduled token refresh process

  **In production applications:**
  - Implement automatic token refresh before expiration
  - Store tokens securely (encrypted in database)
  - Handle refresh token rotation properly
  - Implement fallback to re-authorization flow if refresh fails
  """))
else
  Kino.Frame.render(refresh_frame, Kino.Markdown.new("""
  ## ℹ️ Token Refresh Not Available

  #{if oauth_client &amp;&amp; oauth_client.token do
      if oauth_client.token.refresh_token do
        "No refresh token available. Some OAuth flows don't provide refresh tokens."
      else
        "No refresh token available from the token exchange."
      end
    else
      "Please complete the OAuth flow first to get tokens."
    end}
  """))
end

Production Implementation Notes

This LiveBook demonstrates the OAuth2 Authorization Code Flow for DocuSign in an interactive way. When implementing this in a production web application, consider these important points:

Security Best Practices

  1. HTTPS Only: Always use HTTPS for redirect URIs in production
  2. State Parameter: Always validate the state parameter to prevent CSRF attacks
  3. Secure Token Storage: Store tokens encrypted in a secure database
  4. Token Scoping: Only request the minimum required OAuth scopes

Implementation Patterns

For production Phoenix applications, refer to the comprehensive examples in the DocuSign Elixir README which includes complete Phoenix controller implementation, token management patterns, and security best practices.

Conclusion

🎉 Congratulations! You’ve successfully implemented the OAuth2 Authorization Code Flow with DocuSign:

  1. ✅ Generated authorization URL for user consent
  2. ✅ Exchanged authorization code for access/refresh tokens
  3. ✅ Retrieved user information using OAuth tokens
  4. ✅ Created DocuSign connection from OAuth tokens
  5. ✅ Made authenticated API calls to DocuSign
  6. ✅ Demonstrated token refresh functionality

Key Benefits of OAuth2 Authorization Code Flow:

  • User Control: Users explicitly grant permission through DocuSign’s interface
  • No Admin Pre-approval: Unlike JWT impersonation, no admin setup required
  • Standard Compliance: Uses industry-standard OAuth2 flow
  • Token Refresh: Long-term access through refresh tokens
  • Secure: Follows OAuth2 security best practices

Next Steps:

  • Implement this flow in your web application
  • Set up secure token storage and management
  • Handle token refresh and expiration gracefully
  • Add error handling and user feedback
  • Consider implementing webhook notifications for document status updates

For more information, check out the DocuSign Elixir GitHub repository and the official DocuSign API documentation.

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