1 files changed, 142 insertions, 0 deletions
diff --git a/app/util/authentication.py b/app/util/authentication.py
new file mode 100644
index 0000000..b94b1c6
--- /dev/null
+++ b/app/util/authentication.py
@@ -0,0 +1,142 @@
+import random
+import bcrypt
+from fastapi import Depends, HTTPException, status, Cookie
+from fastapi.security import OAuth2PasswordBearer
+from fastapi.responses import RedirectResponse
+from jwt.exceptions import InvalidTokenError
+from datetime import datetime, timedelta
+from typing import Annotated, Optional
+import jwt
+
+from app.util.db_dependency import get_db
+from sqlalchemy.orm import sessionmaker
+from app.schemas.auth_schemas import *
+from models import User as UserDB
+
+secret_key = random.randbytes(32)
+algorithm = "HS256"
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")
+
+"""
+Helper functions for authentication
+"""
+
+
+def verify_password(plain_password, hashed_password):
+    return bcrypt.checkpw(
+        plain_password.encode("utf-8"), hashed_password.encode("utf-8")
+    )
+
+
+def get_user(db, username: str):
+    """
+    Get the user object from the database
+    """
+    user = db.query(UserDB).filter(UserDB.username == username).first()
+    if user:
+        return UserInDB(**user.__dict__)
+
+
+def authenticate_user(db, username: str, password: str):
+    """
+    Determine if the correct username and password were provided
+    If so, return the user object
+    """
+    user = get_user(db, username)
+    if not user:
+        return False
+    if not verify_password(password, user.hashed_password):
+        return False
+    return user
+
+
+def create_access_token(data: dict, expires_delta: timedelta):
+    """
+    Return an encoded JWT token with the given data
+    """
+    to_encode = data.copy()
+    expire = datetime.utcnow() + expires_delta
+    to_encode.update({"exp": expire})
+    encoded_jwt = jwt.encode(to_encode, secret_key, algorithm=algorithm)
+    return encoded_jwt
+
+
+async def get_current_user_from_cookie(
+    access_token: str = Cookie(None), db=Depends(get_db)
+):
+    """
+    Return the user based on the access token in the cookie
+
+    Used for authentication into UI pages - so if no cookie
+    exists, redirect to login page rather than returning a 401
+
+    Also pass is_ui=True to alert get_current_user that we need
+    to use RedirectResponse rather than raising an HTTPException
+    """
+    if access_token:
+        return await get_current_user(access_token, is_ui=True, db=db)
+    return RedirectResponse(url="/login")
+
+
+async def get_current_user_from_token(
+    token: Annotated[str, Depends(oauth2_scheme)], db=Depends(get_db)
+):
+    return await get_current_user(token, db=db)
+
+
+# Backwards kinda of way to get refresh token support
+# `refresh_get_current_user` is only called from /refresh
+# and alerts `get_current_user` that it should expect a refresh token
+async def refresh_get_current_user(
+    token: Annotated[str, Depends(oauth2_scheme)], db=Depends(get_db)
+):
+    return await get_current_user(token, is_refresh=True, db=db)
+
+
+async def get_current_user(
+    token: str,
+    is_refresh: bool = False,
+    is_ui: bool = False,
+    db: Optional[sessionmaker] = None,
+):
+    """
+    Return the current user based on the token
+
+    OR on error -
+    If is_ui=True, the request is from a UI page and we should redirect to login
+    Otherwise, the request is from an API and we should return a 401
+    """
+
+    def raise_unauthorized():
+        if is_ui:
+            return RedirectResponse(url="/login")
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Could not validate credentials",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+
+    try:
+        payload = jwt.decode(token, secret_key, algorithms=[algorithm])
+        username: str = payload.get("sub")
+        refresh: bool = payload.get("refresh")
+        if username is None:
+            return raise_unauthorized()
+        # For some reason, an access token was passed when a refresh
+        # token was expected - some likely malicious activity
+        if not refresh and is_refresh:
+            return raise_unauthorized()
+        # If the token passed is a refresh token and the function
+        # is not expecting a refresh token, raise an error
+        if refresh and not is_refresh:
+            return raise_unauthorized()
+
+        token_data = TokenData(username=username)
+    except InvalidTokenError:
+        return raise_unauthorized()
+
+    user = get_user(db, username=token_data.username)
+    if user is None:
+        return raise_unauthorized()
+
+    return user