add alternative filekey generator; closes #52

README.md

@@ -88,6 +88,7 @@ turn almost any device into a file server with resumable uploads/downloads using
 * [security](#security) - there is a [discord server](https://discord.gg/25J8CdTT6G)
     * [gotchas](#gotchas) - behavior that might be unexpected
     * [cors](#cors) - cross-site request config
+    * [filekeys](#filekeys) - prevent filename bruteforcing
     * [password hashing](#password-hashing) - you can hash passwords
     * [https](#https) - both HTTP and HTTPS are accepted
 * [recovering from crashes](#recovering-from-crashes)
@@ -356,7 +357,7 @@ permissions:
 * `m` (move): move files/folders *from* this folder
 * `d` (delete): delete files/folders
 * `g` (get): only download files, cannot see folder contents or zip/tar
-* `G` (upget): same as `g` except uploaders get to see their own filekeys (see `fk` in examples below)
+* `G` (upget): same as `g` except uploaders get to see their own [filekeys](#filekeys) (see `fk` in examples below)
 * `h` (html): same as `g` except folders return their index.html, and filekeys are not necessary for index.html
 * `a` (admin): can see uploader IPs, config-reload
 
@@ -370,7 +371,7 @@ examples:
   * `u1` can open the `inc` folder, but cannot see the contents, only upload new files to it
   * `u2` can browse it and move files *from* `/inc` into any folder where `u2` has write-access
 * make folder `/mnt/ss` available at `/i`, read-write for u1, get-only for everyone else, and enable filekeys: `-v /mnt/ss:i:rw,u1:g:c,fk=4`
-  * `c,fk=4` sets the `fk` (filekey) volflag to 4, meaning each file gets a 4-character accesskey
+  * `c,fk=4` sets the `fk` ([filekey](#filekeys)) volflag to 4, meaning each file gets a 4-character accesskey
   * `u1` can upload files, browse the folder, and see the generated filekeys
   * other users cannot browse the folder, but can access the files if they have the full file URL with the filekey
   * replacing the `g` permission with `wg` would let anonymous users upload files, but not see the required filekey to access it
@@ -1647,9 +1648,7 @@ safety profiles:
 other misc notes:
 
 * you can disable directory listings by giving permission `g` instead of `r`, only accepting direct URLs to files
-  * combine this with volflag `c,fk` to generate filekeys (per-file accesskeys); users which have full read-access will then see URLs with `?k=...` appended to the end, and `g` users must provide that URL including the correct key to avoid a 404
-    * the default filekey entropy is fairly small so give `--fk-salt` around 30 characters if you want filekeys longer than 16 chars
-  * permissions `wG` lets users upload files and receive their own filekeys, still without being able to see other uploads
+  * you may want [filekeys](#filekeys) to prevent filename bruteforcing
   * permission `h` instead of `r` makes copyparty behave like a traditional webserver with directory listing/index disabled, returning index.html instead
     * compatibility with filekeys: index.html itself can be retrieved without the correct filekey, but all other files are protected
 
@@ -1679,6 +1678,17 @@ by default, except for `GET` and `HEAD` operations, all requests must either:
 cors can be configured with `--acao` and `--acam`, or the protections entirely disabled with `--allow-csrf`
 
 
+## filekeys
+
+prevent filename bruteforcing
+
+volflag `c,fk` generates filekeys (per-file accesskeys) for all files; users which have full read-access (permission `r`) will then see URLs with the correct filekey `?k=...` appended to the end, and `g` users must provide that URL including the correct key to avoid a 404
+
+by default, filekeys are generated based on salt (`--fk-salt`) + filesystem-path + file-size + inode (if not windows); add volflag `fka` to generate slightly weaker filekeys which will not be invalidated if the file is edited (only salt + path)
+
+permissions `wG` (write + upget) lets users upload files and receive their own filekeys, still without being able to see other uploads
+
+
 ## password hashing
 
 you can hash passwords  before putting them into config files / providing them as arguments; see `--help-pwhash` for all the details

copyparty/__main__.py

@@ -246,12 +246,7 @@ def get_fk_salt(cert_path) -> str:
         with open(fp, "rb") as f:
             ret = f.read().strip()
     except:
-        if os.path.exists(cert_path):
-            zi = os.path.getmtime(cert_path)
-            ret = "{}".format(zi).encode("utf-8")
-        else:
-            ret = base64.b64encode(os.urandom(18))
-
+        ret = base64.b64encode(os.urandom(18))
         with open(fp, "wb") as f:
             f.write(ret + b"\n")
 

copyparty/authsrv.py

@@ -12,7 +12,7 @@ import threading
 import time
 from datetime import datetime
 
-from .__init__ import ANYWIN, TYPE_CHECKING, WINDOWS
+from .__init__ import ANYWIN, E, TYPE_CHECKING, WINDOWS
 from .bos import bos
 from .cfg import flagdescs, permdescs, vf_bmap, vf_cmap, vf_vmap
 from .pwhash import PWHash
@@ -1390,6 +1390,9 @@ class AuthSrv(object):
         have_fk = False
         for vol in vfs.all_vols.values():
             fk = vol.flags.get("fk")
+            fka = vol.flags.get("fka")
+            if fka and not fk:
+                fk = fka
             if fk:
                 vol.flags["fk"] = int(fk) if fk is not True else 8
                 have_fk = True
@@ -1397,6 +1400,12 @@ class AuthSrv(object):
         if have_fk and re.match(r"^[0-9\.]+$", self.args.fk_salt):
             self.log("filekey salt: {}".format(self.args.fk_salt))
 
+        fk_len = len(self.args.fk_salt)
+        if have_fk and fk_len < 14:
+            t = "WARNING: filekeys are enabled, but the salt is only %d chars long; %d or longer is recommended. Either specify a stronger salt using --fk-salt or delete this file and restart copyparty: %s"
+            zs = os.path.join(E.cfg, "fk-salt.txt")
+            self.log(t % (fk_len, 16, zs), 3)
+
         for vol in vfs.all_vols.values():
             if "pk" in vol.flags and "gz" not in vol.flags and "xz" not in vol.flags:
                 vol.flags["gz"] = False  # def.pk

copyparty/httpcli.py

@@ -202,8 +202,10 @@ class HttpCli(object):
         if rem.startswith("/") or rem.startswith("../") or "/../" in rem:
             raise Exception("that was close")
 
-    def _gen_fk(self, salt: str, fspath: str, fsize: int, inode: int) -> str:
-        return gen_filekey_dbg(salt, fspath, fsize, inode, self.log, self.args.log_fk)
+    def _gen_fk(self, alg: int, salt: str, fspath: str, fsize: int, inode: int) -> str:
+        return gen_filekey_dbg(
+            alg, salt, fspath, fsize, inode, self.log, self.args.log_fk
+        )
 
     def j2s(self, name: str, **ka: Any) -> str:
         tpl = self.conn.hsrv.j2[name]
@@ -1712,7 +1714,9 @@ class HttpCli(object):
 
         vsuf = ""
         if (self.can_read or self.can_upget) and "fk" in vfs.flags:
+            alg = 2 if "fka" in vfs.flags else 1
             vsuf = "?k=" + self.gen_fk(
+                alg,
                 self.args.fk_salt,
                 path,
                 post_sz,
@@ -2445,7 +2449,9 @@ class HttpCli(object):
         for sz, sha_hex, sha_b64, ofn, lfn, ap in files:
             vsuf = ""
             if (self.can_read or self.can_upget) and "fk" in vfs.flags:
+                alg = 2 if "fka" in vfs.flags else 1
                 vsuf = "?k=" + self.gen_fk(
+                    alg,
                     self.args.fk_salt,
                     ap,
                     sz,
@@ -3412,7 +3418,7 @@ class HttpCli(object):
         t0 = time.time()
         lim = time.time() - self.args.unpost
         fk_vols = {
-            vol: vol.flags["fk"]
+            vol: (vol.flags["fk"], 2 if "fka" in vol.flags else 1)
             for vp, vol in self.asrv.vfs.all_vols.items()
             if "fk" in vol.flags and (vp in self.rvol or vp in self.upvol)
         }
@@ -3421,7 +3427,7 @@ class HttpCli(object):
             if not cur:
                 continue
 
-            nfk = fk_vols.get(vol, 0)
+            nfk, fk_alg = fk_vols.get(vol) or (0, 0)
 
             q = "select sz, rd, fn, at from up where ip=? and at>?"
             for sz, rd, fn, at in cur.execute(q, (self.ip, lim)):
@@ -3432,6 +3438,7 @@ class HttpCli(object):
                 rv = {"vp": quotep(vp), "sz": sz, "at": at, "nfk": nfk}
                 if nfk:
                     rv["ap"] = vol.canonical(vjoin(rd, fn))
+                    rv["fk_alg"] = fk_alg
 
                 ret.append(rv)
                 if len(ret) > 3000:
@@ -3445,6 +3452,7 @@ class HttpCli(object):
             if not nfk:
                 continue
 
+            alg = rv.pop("fk_alg")
             ap = rv.pop("ap")
             try:
                 st = bos.stat(ap)
@@ -3452,7 +3460,7 @@ class HttpCli(object):
                 continue
 
             fk = self.gen_fk(
-                self.args.fk_salt, ap, st.st_size, 0 if ANYWIN else st.st_ino
+                alg, self.args.fk_salt, ap, st.st_size, 0 if ANYWIN else st.st_ino
             )
             rv["vp"] += "?k=" + fk[:nfk]
 
@@ -3713,8 +3721,13 @@ class HttpCli(object):
 
         if not is_dir and (self.can_read or self.can_get):
             if not self.can_read and not fk_pass and "fk" in vn.flags:
+                alg = 2 if "fka" in vn.flags else 1
                 correct = self.gen_fk(
-                    self.args.fk_salt, abspath, st.st_size, 0 if ANYWIN else st.st_ino
+                    alg,
+                    self.args.fk_salt,
+                    abspath,
+                    st.st_size,
+                    0 if ANYWIN else st.st_ino,
                 )[: vn.flags["fk"]]
                 got = self.uparam.get("k")
                 if got != correct:
@@ -3922,6 +3935,7 @@ class HttpCli(object):
             ls_names = exclude_dotfiles(ls_names)
 
         add_fk = vn.flags.get("fk")
+        fk_alg = 2 if "fka" in vn.flags else 1
 
         dirs = []
         files = []
@@ -3978,11 +3992,15 @@ class HttpCli(object):
             except:
                 ext = "%"
 
-            if add_fk:
+            if add_fk and not is_dir:
                 href = "%s?k=%s" % (
                     quotep(href),
                     self.gen_fk(
-                        self.args.fk_salt, fspath, sz, 0 if ANYWIN else inf.st_ino
+                        fk_alg,
+                        self.args.fk_salt,
+                        fspath,
+                        sz,
+                        0 if ANYWIN else inf.st_ino,
                     )[:add_fk],
                 )
             else:

copyparty/u2idx.py

@@ -314,6 +314,7 @@ class U2idx(object):
             sret = []
             fk = flags.get("fk")
             dots = flags.get("dotsrch")
+            fk_alg = 2 if "fka" in flags else 1
             c = cur.execute(uq, tuple(vuv))
             for hit in c:
                 w, ts, sz, rd, fn, ip, at = hit[:7]
@@ -333,16 +334,17 @@ class U2idx(object):
                 else:
                     try:
                         ap = absreal(os.path.join(ptop, rd, fn))
-                        inf = bos.stat(ap)
+                        ino = 0 if ANYWIN or fk_alg == 2 else bos.stat(ap).st_ino
                     except:
                         continue
 
-                    suf = (
-                        "?k="
-                        + gen_filekey(
-                            self.args.fk_salt, ap, sz, 0 if ANYWIN else inf.st_ino
-                        )[:fk]
-                    )
+                    suf = "?k=" + gen_filekey(
+                        fk_alg,
+                        self.args.fk_salt,
+                        ap,
+                        sz,
+                        ino,
+                    )[:fk]
 
                 lim -= 1
                 if lim < 0:

copyparty/up2k.py

@@ -228,8 +228,10 @@ class Up2k(object):
 
         self.log_func("up2k", msg, c)
 
-    def _gen_fk(self, salt: str, fspath: str, fsize: int, inode: int) -> str:
-        return gen_filekey_dbg(salt, fspath, fsize, inode, self.log, self.args.log_fk)
+    def _gen_fk(self, alg: int, salt: str, fspath: str, fsize: int, inode: int) -> str:
+        return gen_filekey_dbg(
+            alg, salt, fspath, fsize, inode, self.log, self.args.log_fk
+        )
 
     def _block(self, why: str) -> None:
         self.blocked = why
@@ -2623,9 +2625,10 @@ class Up2k(object):
                 and not self.args.nw
                 and (cj["user"] in vfs.axs.uread or cj["user"] in vfs.axs.upget)
             ):
+                alg = 2 if "fka" in vfs.flags else 1
                 ap = absreal(djoin(job["ptop"], job["prel"], job["name"]))
                 ino = 0 if ANYWIN else bos.stat(ap).st_ino
-                fk = self.gen_fk(self.args.fk_salt, ap, job["size"], ino)
+                fk = self.gen_fk(alg, self.args.fk_salt, ap, job["size"], ino)
                 ret["fk"] = fk[: vfs.flags["fk"]]
 
             return ret

copyparty/util.py

@@ -1567,15 +1567,18 @@ def rand_name(fdir: str, fn: str, rnd: int) -> str:
     return fn
 
 
-def gen_filekey(salt: str, fspath: str, fsize: int, inode: int) -> str:
-    return base64.urlsafe_b64encode(
-        hashlib.sha512(
-            ("%s %s %s %s" % (salt, fspath, fsize, inode)).encode("utf-8", "replace")
-        ).digest()
-    ).decode("ascii")
+def gen_filekey(alg: int, salt: str, fspath: str, fsize: int, inode: int) -> str:
+    if alg == 1:
+        zs = "%s %s %s %s" % (salt, fspath, fsize, inode)
+    else:
+        zs = "%s %s" % (salt, fspath)
+
+    zb = zs.encode("utf-8", "replace")
+    return base64.urlsafe_b64encode(hashlib.sha512(zb).digest()).decode("ascii")
 
 
 def gen_filekey_dbg(
+    alg: int,
     salt: str,
     fspath: str,
     fsize: int,
@@ -1583,7 +1586,7 @@ def gen_filekey_dbg(
     log: "NamedLogger",
     log_ptn: Optional[Pattern[str]],
 ) -> str:
-    ret = gen_filekey(salt, fspath, fsize, inode)
+    ret = gen_filekey(alg, salt, fspath, fsize, inode)
 
     assert log_ptn
     if log_ptn.search(fspath):

tests/util.py

@@ -138,6 +138,7 @@ class Cfg(Namespace):
             dbd="wal",
             s_wr_sz=512 * 1024,
             th_size="320x256",
+            fk_salt="a" * 16,
             unpost=600,
             u2sort="s",
             mtp=[],