Add authentication and user profile endpoint

Argon2 password hashing, JWT session issuing/verification
(auth/security.py), register/login routes, the bearer-token
get_current_user dependency, and GET /users/me for address + balance.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/api/routes/users.py

@@ -0,0 +1,18 @@
+from fastapi import APIRouter, Depends
+from pydantic import BaseModel
+
+from app.auth.dependencies import get_current_user
+from app.db.models import User
+
+router = APIRouter(prefix="/users", tags=["users"])
+
+
+class MeResponse(BaseModel):
+    username: str
+    address: str
+    balance_sats: int
+
+
+@router.get("/me", response_model=MeResponse)
+async def me(user: User = Depends(get_current_user)) -> MeResponse:
+    return MeResponse(username=user.username, address=user.address, balance_sats=user.cached_balance_sats)

app/auth/dependencies.py

@@ -0,0 +1,25 @@
+from fastapi import Depends, HTTPException, status
+from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.auth.security import decode_access_token
+from app.db.models import User
+from app.db.session import get_session
+
+_bearer = HTTPBearer()
+
+
+async def get_current_user(
+    credentials: HTTPAuthorizationCredentials = Depends(_bearer),
+    session: AsyncSession = Depends(get_session),
+) -> User:
+    try:
+        user_id = decode_access_token(credentials.credentials)
+    except Exception as exc:
+        raise HTTPException(status.HTTP_401_UNAUTHORIZED, "invalid token") from exc
+
+    user = await session.scalar(select(User).where(User.id == user_id))
+    if user is None:
+        raise HTTPException(status.HTTP_401_UNAUTHORIZED, "user not found")
+    return user

app/auth/routes.py

@@ -0,0 +1,70 @@
+from fastapi import APIRouter, Depends, HTTPException, Request, status
+from pydantic import BaseModel
+from sqlalchemy import func, select
+from sqlalchemy.exc import IntegrityError
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.auth.security import create_access_token, hash_password, verify_password
+from app.db.models import User
+from app.db.session import get_session
+from app.wallet.hd import derive_user_address
+
+router = APIRouter(prefix="/auth", tags=["auth"])
+
+_MAX_REGISTER_RETRIES = 5
+
+
+class RegisterRequest(BaseModel):
+    username: str
+    password: str
+
+
+class TokenResponse(BaseModel):
+    access_token: str
+    address: str
+
+
+@router.post("/register", response_model=TokenResponse, status_code=status.HTTP_201_CREATED)
+async def register(
+    body: RegisterRequest, request: Request, session: AsyncSession = Depends(get_session)
+) -> TokenResponse:
+    existing = await session.scalar(select(User).where(User.username == body.username))
+    if existing is not None:
+        raise HTTPException(status.HTTP_409_CONFLICT, "username already taken")
+
+    password_hash = hash_password(body.password)
+
+    for _ in range(_MAX_REGISTER_RETRIES):
+        max_index = await session.scalar(select(func.max(User.derivation_index)))
+        next_index = 0 if max_index is None else max_index + 1
+        address = derive_user_address(next_index)
+        user = User(
+            username=body.username,
+            password_hash=password_hash,
+            derivation_index=next_index,
+            address=address,
+        )
+        session.add(user)
+        try:
+            await session.commit()
+        except IntegrityError:
+            await session.rollback()
+            continue
+        await session.refresh(user)
+        request.app.state.electrum_listener.address_for_new_user(user.id, user.address)
+        return TokenResponse(access_token=create_access_token(user.id), address=user.address)
+
+    raise HTTPException(status.HTTP_409_CONFLICT, "could not allocate a derivation index, retry")
+
+
+class LoginRequest(BaseModel):
+    username: str
+    password: str
+
+
+@router.post("/login", response_model=TokenResponse)
+async def login(body: LoginRequest, session: AsyncSession = Depends(get_session)) -> TokenResponse:
+    user = await session.scalar(select(User).where(User.username == body.username))
+    if user is None or not verify_password(body.password, user.password_hash):
+        raise HTTPException(status.HTTP_401_UNAUTHORIZED, "invalid credentials")
+    return TokenResponse(access_token=create_access_token(user.id), address=user.address)

app/auth/security.py

@@ -0,0 +1,31 @@
+from datetime import datetime, timedelta, timezone
+
+import jwt
+from argon2 import PasswordHasher
+from argon2.exceptions import VerifyMismatchError
+
+from app.config import settings
+
+_hasher = PasswordHasher()
+
+
+def hash_password(password: str) -> str:
+    return _hasher.hash(password)
+
+
+def verify_password(password: str, password_hash: str) -> bool:
+    try:
+        return _hasher.verify(password_hash, password)
+    except VerifyMismatchError:
+        return False
+
+
+def create_access_token(user_id: int) -> str:
+    expires_at = datetime.now(timezone.utc) + timedelta(minutes=settings.jwt_expire_minutes)
+    payload = {"sub": str(user_id), "exp": expires_at}
+    return jwt.encode(payload, settings.jwt_secret, algorithm=settings.jwt_algorithm)
+
+
+def decode_access_token(token: str) -> int:
+    payload = jwt.decode(token, settings.jwt_secret, algorithms=[settings.jwt_algorithm])
+    return int(payload["sub"])

tests/unit/test_security.py

@@ -0,0 +1,13 @@
+from app.auth import security
+
+
+def test_password_hash_roundtrip():
+    hashed = security.hash_password("s3cret!")
+    assert security.verify_password("s3cret!", hashed)
+    assert not security.verify_password("wrong", hashed)
+
+
+def test_jwt_roundtrip(monkeypatch):
+    monkeypatch.setattr(security.settings, "jwt_secret", "test-secret")
+    token = security.create_access_token(user_id=42)
+    assert security.decode_access_token(token) == 42