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Overview

The BillBuddy API uses JSON Web Tokens (JWT) for authentication. After registering or logging in, you’ll receive a token that must be included in the Authorization header for all protected endpoints.

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Authentication Flow

1

Register or Login

Create a new account with /api/auth/register or login with existing credentials using /api/auth/login.
2

Receive JWT Token

Upon successful authentication, you’ll receive a JWT token in the response.
3

Include Token in Requests

Add the token to the Authorization header as a Bearer token for all protected endpoints.

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Register a New User

Create a new user account and receive an authentication token. Endpoint: POST /api/auth/register Access: Public

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Request Body

​
name
string
required
User’s full name (max 50 characters)
​
email
string
required
Valid email address (must be unique)
​
password
string
required
Password (minimum 6 characters)

​
Example Request

curl -X POST http://localhost:5000/api/auth/register \
  -H "Content-Type: application/json" \
  -d '{
    "name": "John Doe",
    "email": "john@example.com",
    "password": "mypassword123"
  }'

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Response

Success (201 Created):
​
success
boolean
Indicates successful registration
​
token
string
JWT authentication token (expires in 30 days)
{
  "success": true,
  "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6IjY1YTVkMzIxZjc4OTBhYmNkZWYxMjM0NSIsImlhdCI6MTcwNTMxNzYwMSwiZXhwIjoxNzA3OTA5NjAxfQ.Xj4kR8pQ2vN9mK3sL7tY6uZ1wA5bC9dE2fG3hI4jK5l"
}
Error (400 Bad Request): 
{
  "message": "User already exists"
}

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Login

Authenticate with existing credentials and receive a token. Endpoint: POST /api/auth/login Access: Public

​
Request Body

​
email
string
required
User’s email address
​
password
string
required
User’s password

​
Example Request

curl -X POST http://localhost:5000/api/auth/login \
  -H "Content-Type: application/json" \
  -d '{
    "email": "john@example.com",
    "password": "mypassword123"
  }'

​
Response

Success (200 OK):
​
success
boolean
Indicates successful login
​
token
string
JWT authentication token (expires in 30 days)
{
  "success": true,
  "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6IjY1YTVkMzIxZjc4OTBhYmNkZWYxMjM0NSIsImlhdCI6MTcwNTMxNzYwMSwiZXhwIjoxNzA3OTA5NjAxfQ.Xj4kR8pQ2vN9mK3sL7tY6uZ1wA5bC9dE2fG3hI4jK5l"
}
Error (400 Bad Request): 
{
  "message": "Invalid credentials"
}

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Get Current User

Retrieve the authenticated user’s profile information. Endpoint: GET /api/auth/me Access: Private (requires authentication)

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Headers

​
Authorization
string
required
Bearer token obtained from login or registration

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Example Request

curl -X GET http://localhost:5000/api/auth/me \
  -H "Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..."

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Response

Success (200 OK):
​
_id
string
User’s unique identifier
​
name
string
User’s full name
​
email
string
User’s email address
​
groups
array
Array of group IDs the user belongs to
​
createdAt
string
ISO 8601 timestamp of account creation
{
  "_id": "65a5d321f7890abcdef12345",
  "name": "John Doe",
  "email": "john@example.com",
  "groups": [
    "65a5d456f7890abcdef12346",
    "65a5d567f7890abcdef12347"
  ],
  "createdAt": "2024-01-15T10:30:00.000Z"
}
Error (401 Unauthorized): 
{
  "message": "Not authorized, no token"
}

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Using Authentication Tokens

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Token Format

Tokens must be sent in the Authorization header using the Bearer authentication scheme: 
Authorization: Bearer <token>

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Token Expiration

JWT tokens expire after 30 days. The expiration time is encoded in the token payload: 
{
  "id": "65a5d321f7890abcdef12345",
  "iat": 1705317601,
  "exp": 1707909601
}
  • iat: Issued at timestamp
  • exp: Expiration timestamp

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Token Verification

The API verifies tokens on protected endpoints using the following process:
  1. Extracts the token from the Authorization header
  2. Verifies the token signature using the JWT secret
  3. Decodes the user ID from the token payload
  4. Fetches the user from the database (excluding password)
  5. Attaches the user object to req.user for use in route handlers
See the implementation in /backend/middleware/auth.js:4-31.

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Protected Routes

The following endpoints require authentication:

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Authentication

  • GET /api/auth/me - Get current user profile

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Groups

  • POST /api/groups - Create a group
  • GET /api/groups - List user’s groups
  • GET /api/groups/:id - Get group details
  • PUT /api/groups/:id - Update group
  • DELETE /api/groups/:id - Delete group
  • POST /api/groups/:id/members - Add member to group

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Expenses

  • GET /api/expenses/recent - Get recent expenses
  • POST /api/expenses - Create an expense
  • GET /api/expenses/group/:groupId - List group expenses
  • GET /api/expenses/:id - Get expense details
  • PUT /api/expenses/:id - Update expense
  • DELETE /api/expenses/:id - Delete expense

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Settlements

  • POST /api/settlements - Create a settlement
  • GET /api/settlements/group/:groupId - List group settlements
  • PUT /api/settlements/:id/status - Update settlement status

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Authentication Errors

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Missing Token

When no token is provided: 
{
  "message": "Not authorized, no token"
}
Status Code: 401 Unauthorized

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Invalid Token

When the token is malformed, expired, or has an invalid signature: 
{
  "message": "Not authorized"
}
Status Code: 401 Unauthorized

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Security Best Practices

Never commit your JWT secret to version control. Use environment variables to store sensitive configuration.
Store tokens securely on the client side using:
  • HttpOnly cookies for web applications
  • Secure storage APIs for mobile apps
  • Never store tokens in localStorage if XSS is a concern

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Complete Authentication Example

Here’s a complete workflow from registration to making authenticated requests:

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Step 1: Register

curl -X POST http://localhost:5000/api/auth/register \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Jane Smith",
    "email": "jane@example.com",
    "password": "securepass123"
  }'
Response: 
{
  "success": true,
  "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6IjY1YTVkOTg3ZjdkYWJjZGVmMTIzNDUiLCJpYXQiOjE3MDUzMTk3NDMsImV4cCI6MTcwNzkxMTc0M30.9sK3mN2pQ7rV8tX4uY5zA1bC6dE9fG2hI3jK4lM7nO8"
}

​
Step 2: Use Token in Requests

# Get your profile
curl -X GET http://localhost:5000/api/auth/me \
  -H "Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6IjY1YTVkOTg3ZjdkYWJjZGVmMTIzNDUiLCJpYXQiOjE3MDUzMTk3NDMsImV4cCI6MTcwNzkxMTc0M30.9sK3mN2pQ7rV8tX4uY5zA1bC6dE9fG2hI3jK4lM7nO8"

# Create a group
curl -X POST http://localhost:5000/api/groups \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..." \
  -d '{
    "name": "Roommates",
    "description": "Shared apartment expenses",
    "members": [{"email": "bob@example.com"}]
  }'

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