Move uploaded file handling to class

So uploading files via remote URLs was completely broken and
apparently nobody noticed. This commit fixes that, too.
Wouldn’t it be nice if there were a test suite!

fhost.py

@@ -22,6 +22,7 @@ from flask import Flask, abort, make_response, redirect, render_template, \
     Request, request, Response, send_from_directory, url_for
 from flask_sqlalchemy import SQLAlchemy
 from flask_migrate import Migrate
+from werkzeug.datastructures import FileStorage
 from sqlalchemy import and_, or_
 from sqlalchemy.orm import declared_attr
 import sqlalchemy.types as types
@@ -37,9 +38,11 @@ import sys
 import time
 import datetime
 import ipaddress
+import io
 import typing
 import requests
 import secrets
+import shutil
 import re
 from validators import url as url_valid
 from pathlib import Path
@@ -155,6 +158,65 @@ class IPAddress(types.TypeDecorator):
         return value
 
 
+class TransferFile():
+    def __init__(self, stream, name, content_type):
+        self.stream = stream
+        self.name = name
+        self.sha256 = file_digest(stream, "sha256").hexdigest()
+
+        stream.seek(0, os.SEEK_END)
+        self.size = stream.tell()
+        stream.seek(0)
+
+        self.mime, self.mime_detected = self.get_mime(content_type)
+        self.ext = self.get_ext()
+
+    def get_mime(self, content_type):
+        try:
+            guess = mimedetect.from_descriptor(self.stream.fileno())
+        except io.UnsupportedOperation:
+            guess = mimedetect.from_buffer(self.stream.getvalue())
+
+        app.logger.debug(f"MIME - specified: '{content_type}' - "
+                         f"detected: '{guess}'")
+
+        if (not content_type
+                or "/" not in content_type
+                or content_type == "application/octet-stream"):
+            mime = guess
+        else:
+            mime = content_type
+
+        if mime.startswith("text/") and "charset" not in mime:
+            mime += "; charset=utf-8"
+
+        return mime, guess
+
+    def get_ext(self):
+        ext = "".join(Path(self.name).suffixes[-2:])
+        if len(ext) > app.config["FHOST_MAX_EXT_LENGTH"]:
+            ext = Path(self.name).suffixes[-1]
+        gmime = self.mime.split(";")[0]
+        guess = guess_extension(gmime)
+
+        app.logger.debug(f"extension - specified: '{ext}' - detected: "
+                         f"'{guess}'")
+
+        if not ext:
+            if gmime in app.config["FHOST_EXT_OVERRIDE"]:
+                ext = app.config["FHOST_EXT_OVERRIDE"][gmime]
+            elif guess:
+                ext = guess
+            else:
+                ext = ""
+
+        return ext[:app.config["FHOST_MAX_EXT_LENGTH"]] or ".bin"
+
+    def save(self, path: os.PathLike):
+        with open(path, "wb") as of:
+            shutil.copyfileobj(self.stream, of)
+
+
 class File(db.Model):
     id = db.Column(db.Integer, primary_key=True)
     sha256 = db.Column(db.String, unique=True)
@@ -170,10 +232,10 @@ class File(db.Model):
     last_vscan = db.Column(db.DateTime)
     size = db.Column(db.BigInteger)
 
-    def __init__(self, sha256, ext, mime, addr, ua, expiration, mgmt_token):
+    def __init__(self, file_: TransferFile, addr, ua, expiration, mgmt_token):
-        self.sha256 = sha256
+        self.sha256 = file_.sha256
-        self.ext = ext
+        self.ext = file_.ext
-        self.mime = mime
+        self.mime = file_.mime
         self.addr = addr
         self.ua = ua
         self.expiration = expiration
@@ -246,62 +308,20 @@ class File(db.Model):
     down to that value.
     """
     @staticmethod
-    def store(file_, requested_expiration: typing.Optional[int], addr, ua,
+    def store(file_: TransferFile, requested_expiration: typing.Optional[int],
-              secret: bool):
+              addr, ua, secret: bool):
-        fstream = file_.stream
-        digest = file_digest(fstream, "sha256").hexdigest()
-        fstream.seek(0, os.SEEK_END)
-        flen = fstream.tell()
-        fstream.seek(0)
 
-        def get_mime():
+        if len(file_.mime) > 128:
-            guess = mimedetect.from_descriptor(fstream.fileno())
+            abort(400)
-            app.logger.debug(f"MIME - specified: '{file_.content_type}' - "
-                             f"detected: '{guess}'")
 
-            if (not file_.content_type
+        for flt in MIMEFilter.query.all():
-                    or "/" not in file_.content_type
+            if flt.check(file_.mime_detected):
-                    or file_.content_type == "application/octet-stream"):
+                abort(403, flt.reason)
-                mime = guess
-            else:
-                mime = file_.content_type
 
-            if len(mime) > 128:
+        expiration = File.get_expiration(requested_expiration, file_.size)
-                abort(400)
-
-            for flt in MIMEFilter.query.all():
-                if flt.check(guess):
-                    abort(403, flt.reason)
-
-            if mime.startswith("text/") and "charset" not in mime:
-                mime += "; charset=utf-8"
-
-            return mime
-
-        def get_ext(mime):
-            ext = "".join(Path(file_.filename).suffixes[-2:])
-            if len(ext) > app.config["FHOST_MAX_EXT_LENGTH"]:
-                ext = Path(file_.filename).suffixes[-1]
-            gmime = mime.split(";")[0]
-            guess = guess_extension(gmime)
-
-            app.logger.debug(f"extension - specified: '{ext}' - detected: "
-                             f"'{guess}'")
-
-            if not ext:
-                if gmime in app.config["FHOST_EXT_OVERRIDE"]:
-                    ext = app.config["FHOST_EXT_OVERRIDE"][gmime]
-                elif guess:
-                    ext = guess
-                else:
-                    ext = ""
-
-            return ext[:app.config["FHOST_MAX_EXT_LENGTH"]] or ".bin"
-
-        expiration = File.get_expiration(requested_expiration, flen)
         isnew = True
 
-        f = File.query.filter_by(sha256=digest).first()
+        f = File.query.filter_by(sha256=file_.sha256).first()
         if f:
             # If the file already exists
             if f.removed:
@@ -318,10 +338,8 @@ class File(db.Model):
                 f.expiration = max(f.expiration, expiration)
                 isnew = False
         else:
-            mime = get_mime()
-            ext = get_ext(mime)
             mgmt_token = secrets.token_urlsafe()
-            f = File(digest, ext, mime, addr, ua, expiration, mgmt_token)
+            f = File(file_, addr, ua, expiration, mgmt_token)
 
         f.addr = addr
         f.ua = ua
@@ -334,12 +352,12 @@ class File(db.Model):
 
         storage = Path(app.config["FHOST_STORAGE_PATH"])
         storage.mkdir(parents=True, exist_ok=True)
-        p = storage / digest
+        p = storage / file_.sha256
 
         if not p.is_file():
             file_.save(p)
 
-        f.size = flen
+        f.size = file_.size
 
         if not f.nsfw_score and app.config["NSFW_DETECT"]:
             f.nsfw_score = nsfw.detect(str(p))
@@ -527,8 +545,9 @@ requested_expiration can be:
 Any value greater that the longest allowed file lifespan will be rounded down
 to that value.
 """
-def store_file(f, requested_expiration: typing.Optional[int], addr, ua,
+def store_file(f: TransferFile, requested_expiration: typing.Optional[int],
-               secret: bool):
+               addr, ua, secret: bool):
+
     sf, isnew = File.store(f, requested_expiration, addr, ua, secret)
 
     response = make_response(sf.geturl())
@@ -556,13 +575,10 @@ def store_url(url, addr, ua, secret: bool):
         length = int(r.headers["content-length"])
 
         if length <= app.config["MAX_CONTENT_LENGTH"]:
-            def urlfile(**kwargs):
+            tf = TransferFile(io.BytesIO(r.raw.read()),
-                return type('', (), kwargs)()
+                              r.headers["content-type"], "")
 
-            f = urlfile(read=r.raw.read,
+            return store_file(tf, None, addr, ua, secret)
-                        content_type=r.headers["content-type"], filename="")
-
-            return store_file(f, None, addr, ua, secret)
         else:
             abort(413)
     else:
@@ -661,10 +677,13 @@ def fhost():
             addr = addr.ipv4_mapped or addr
 
         if "file" in request.files:
+            f = request.files["file"]
+            tf = TransferFile(f.stream, f.filename, f.content_type)
+
             try:
                 # Store the file with the requested expiration date
                 return store_file(
-                    request.files["file"],
+                    tf,
                     int(request.form["expires"]),
                     addr,
                     request.user_agent.string,
@@ -676,7 +695,7 @@ def fhost():
             except KeyError:
                 # No expiration date was requested, store with the max lifespan
                 return store_file(
-                    request.files["file"],
+                    tf,
                     None,
                     addr,
                     request.user_agent.string,