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from base64 import b64decode, b64encode
from functools import wraps
from wsgiref.util import request_uri
from typing import Optional, Any, Protocol
from collections.abc import Callable, Iterable
import binascii
import traceback
from sqlite3 import Connection
from . import db
from . import store
class StartResponse(Protocol):
def __call__(
self,
status: str,
headers: list[tuple[str, str]],
exc_info: Optional[tuple] = ...,
/,
) -> Callable[[bytes], object]:
...
Env = dict[str, Any]
App = Callable[[Env, StartResponse], Iterable[bytes]]
Response = Iterable[bytes]
DB_PATH = "paste.sqlite3"
def simple_response(start_response: StartResponse, status: str) -> Response:
body = (status + "\n").encode()
start_response(
status,
[
("Content-Type", "text/plain"),
("Content-Length", str(len(body))),
],
)
return [body]
def redirect(start_response: StartResponse, location: bytes, typ: str) -> Response:
status = {
"text/x.redirect.301": "301 Moved Permanently",
"text/x.redirect.302": "302 Found",
}.get(typ)
if not status:
return simple_response(start_response, "500 Internal Server Error")
body = location
start_response(
status,
[
("Location", location.decode()),
("Content-Type", "text/plain"),
("Content-Length", str(len(body))),
],
)
return [body]
ProtoMiddleware = Callable[[App, Env, StartResponse], Response]
Middleware = Callable[[App], App]
def middleware(f: ProtoMiddleware) -> Middleware:
@wraps(f)
def outer(app: App):
@wraps(app)
def inner(environ: Env, start_response: StartResponse):
return f(app, environ, start_response)
return inner
return outer
@middleware
def catch_exceptions(app: App, environ: Env, start_response: StartResponse) -> Response:
try:
return app(environ, start_response)
except Exception as e:
print("".join(traceback.format_exception(type(e), e, e.__traceback__)))
return simple_response(start_response, "500 Internal Server Error")
@middleware
def validate_method(app: App, environ: Env, start_response: StartResponse) -> Response:
if environ["REQUEST_METHOD"] in {"GET", "HEAD", "POST", "PUT", "DELETE", "OPTIONS"}:
return app(environ, start_response)
if environ["REQUEST_METHOD"] in {"CONNECT", "TRACE", "PATCH"}:
return simple_response(start_response, "405 Method Not Allowed")
return simple_response(start_response, "501 Not Implemented")
@middleware
def options(app: App, environ: Env, start_response: StartResponse) -> Response:
if environ["REQUEST_METHOD"] != "OPTIONS":
return app(environ, start_response)
start_response(
"204 No Content",
[
("Allow", "GET, HEAD, POST, PUT, DELETE, OPTIONS"),
],
)
return []
@middleware
def open_database(app: App, environ: Env, start_response: StartResponse) -> Response:
db_path = environ.get("PASTE_DB", DB_PATH)
with db.connect(db_path) as conn:
environ["paste.db_conn"] = conn
return app(environ, start_response)
def check_auth(conn: Connection, auth: Optional[str]) -> bool:
if not auth or not auth.startswith("Bearer "):
return False
try:
token = b64decode(auth.removeprefix("Bearer ").encode())
except binascii.Error:
return False
(count,) = conn.execute(
"SELECT COUNT(*) FROM token WHERE hash = sha256(?)", (token,)
).fetchone()
return count == 1
@middleware
def authenticate(app: App, environ: Env, start_response: StartResponse) -> Response:
conn = environ["paste.db_conn"]
token = environ.get("HTTP_AUTHORIZATION")
if environ["REQUEST_METHOD"] in {"GET", "HEAD"} or check_auth(conn, token):
return app(environ, start_response)
return simple_response(start_response, "401 Unauthorized")
@catch_exceptions
@validate_method
@options
@open_database
@authenticate
def application(environ: Env, start_response: StartResponse) -> Response:
conn = environ["paste.db_conn"]
name = environ["PATH_INFO"]
if environ["REQUEST_METHOD"] == "GET":
row = store.get(conn, name)
if not row:
return simple_response(start_response, "404 Not Found")
content_type, content_hash, content = row
if content_type.startswith("text/x.redirect"):
return redirect(start_response, content, content_type)
start_response(
"200 OK",
[
("Content-Type", content_type),
("Content-Length", str(len(content))),
("ETag", b64encode(content_hash).decode()),
],
)
return [content]
elif environ["REQUEST_METHOD"] == "HEAD":
row = store.head(conn, name)
if not row:
return simple_response(start_response, "404 Not Found")
content_type, content_hash, content_length, opt_content = row
if content_type.startswith("text/x.redirect"):
return redirect(start_response, opt_content, content_type)
start_response(
"200 OK",
[
("Content-Type", content_type),
("Content-Length", content_length),
("ETag", b64encode(content_hash).decode()),
],
)
return []
elif environ["REQUEST_METHOD"] in {"POST", "PUT"}:
content_type = environ.get("CONTENT_TYPE", "text/plain")
content_length = int(environ["CONTENT_LENGTH"])
content = environ["wsgi.input"].read(content_length)
store.put(conn, name, content, content_type)
return redirect(
start_response, request_uri(environ).encode(), "text/x.redirect.302"
)
elif environ["REQUEST_METHOD"] == "DELETE":
store.delete(conn, name)
return simple_response(start_response, "204 No Content")
return simple_response(start_response, "500 Internal Server Error")
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