1.0.0-alpha.6: share a vault, and see who changed what

README.md

@@ -13,7 +13,7 @@ package replaces it in one step (`Conflicts`/`Replaces: passman`), and your
 vaults stay in `~/.local/share/passman`, which SecretSpace keeps using —
 nothing is moved or renamed. The vault files are the same.
 
-**`main` is 1.0.0-alpha.5, a SecretSpace 3 test version — not for real passwords yet.**
+**`main` is 1.0.0-alpha.6, a SecretSpace 3 test version — not for real passwords yet.**
 For real use keep the [0.11.0 release](https://github.com/usermaneGermane/SecretSpace-Client-Linux/releases/tag/v0.11.0),
 which the rest of this README describes. It installs from a `.deb` on Ubuntu
 22.04 or newer, or runs from source. It has so far been tested in CI only,
@@ -31,14 +31,14 @@ on a virtual display, not yet on a real desktop.
 **Same vaults as on Windows.** The vault file, the sync protocol and the
 features match SecretSpace for Windows (see the version table under *What is
 different from Windows*): 0.11.0 = Windows 2.13.0, and this test version =
-Windows 3.0.0-alpha.5.
+Windows 3.0.0-alpha.6.
 A vault moves between a Windows PC and a Linux PC unchanged, and both sync
 with either server.
 
 ## SecretSpace 3 — the test version
 
-1.0.0-alpha.5 is the same as [SecretSpace for Windows
-3.0.0-alpha.5](https://github.com/usermaneGermane/SecretSpace-Client-Windows#secretspace-3--a-test-version-not-for-real-passwords-yet):
+1.0.0-alpha.6 is the same as [SecretSpace for Windows
+3.0.0-alpha.6](https://github.com/usermaneGermane/SecretSpace-Client-Windows#secretspace-3--a-test-version-not-for-real-passwords-yet):
 accounts with a Secret Key and a 12-word recovery phrase, Argon2id, and
 importing 2.x vaults with their history. It opens SecretSpace 3 accounts only,
 so do not install it over 0.11.0 — your vaults would not show up (they are
@@ -47,7 +47,12 @@ not changed). Since alpha.3 it syncs through a SecretSpace Server 2.0
 from a server*. Since alpha.5 an account can have **several vaults**
 (*Vaults* above the list): each with its own key, picked in the menu above
 the list, and all covered by **Sync** — which needs SecretSpace Server
-2.0.0-alpha.2 for more than the Personal vault. On Linux:
+2.0.0-alpha.2 for more than the Personal vault. Since alpha.6 a vault can be
+**shared** with other accounts of the same server (*Vaults → Members*:
+owner, editor or reader, a fingerprint check before the first share, and
+*Remove* gives the vault a new key), and every vault keeps a signed record
+of **who changed what** (*Vaults → Activity*) — never of who viewed or
+copied a password. Sharing needs SecretSpace Server 2.0.0-alpha.3. On Linux:
 
 - **The Secret Key is kept under your master password** (Argon2id, then
   AES-GCM), not by the system as Windows does with DPAPI. So a copy of the
@@ -57,7 +62,7 @@ the list, and all covered by **Sync** — which needs SecretSpace Server
 - The account folders are `700` and their files `600`, like the vault
   folder; a saved Emergency Kit is `600` too.
 - *Settings → Backup → Open folder* opens the folder with `xdg-open`.
-- The package spells the version `1.0.0~alpha.5`, which apt sorts after
+- The package spells the version `1.0.0~alpha.6`, which apt sorts after
   0.9.0 and before 1.0.0.
 
 | File | What it is |
@@ -191,6 +196,7 @@ Where that README names a Windows version, read the Linux one beside it:
 | 3.0.0-alpha.3 | 1.0.0-alpha.3 | accounts sync through SecretSpace Server 2.0; sign in from a server |
 | 3.0.0-alpha.4 | 1.0.0-alpha.4 | a smoother look: smoothed corners, redrawn sign-in backdrop |
 | 3.0.0-alpha.5 | 1.0.0-alpha.5 | several vaults per account; Sync covers them all (Server 2.0.0-alpha.2) |
+| 3.0.0-alpha.6 | 1.0.0-alpha.6 | sharing a vault (owner / editor / reader), who changed what (Server 2.0.0-alpha.3) |
 
 (0.2.0 added the `.deb` package, which has no Windows counterpart.)
 

sourceFiles/account_crypto.py

@@ -33,6 +33,8 @@
 import unicodedata
 
 from cryptography.hazmat.primitives import hashes, serialization
+from cryptography.hazmat.primitives.asymmetric.ed25519 import (Ed25519PrivateKey,
+                                                               Ed25519PublicKey)
 from cryptography.hazmat.primitives.asymmetric.x25519 import (X25519PrivateKey,
                                                               X25519PublicKey)
 from cryptography.hazmat.primitives.ciphers.aead import AESGCM
@@ -349,6 +351,49 @@ def fingerprint(public_key: bytes) -> str:
     return " ".join(digits[i:i + 4] for i in range(0, 24, 4))
 
 
+def account_fingerprint(public_key: bytes, signing_key: bytes) -> str:
+    """
+    The fingerprint two people compare before the first share: it covers
+    both of an account's public keys, so one check vouches for the key a
+    vault key is wrapped to *and* the key the account's changes are signed
+    with.
+    """
+    return fingerprint(public_key + signing_key)
+
+
+# ===========================================================================
+# Signing (the change log, phase 4)
+# ===========================================================================
+def _signing_private(keyset: dict) -> Ed25519PrivateKey:
+    # Derived from the account's private key rather than stored beside it:
+    # every keyset ever made already has one, the recovery copy included,
+    # and there is nothing new to keep in step. HKDF keeps the two keys
+    # independent in use.
+    seed = _hkdf(_unb64(keyset["x25519_private"], "account key"),
+                 b"PassMan3 signing", b"PassMan3 signing key")
+    return Ed25519PrivateKey.from_private_bytes(seed)
+
+
+def signing_key_of(keyset: dict) -> bytes:
+    """The public half of the account's signing key (32 bytes)."""
+    return _signing_private(keyset).public_key().public_bytes(
+        serialization.Encoding.Raw, serialization.PublicFormat.Raw)
+
+
+def sign(keyset: dict, message: bytes) -> str:
+    return _b64(_signing_private(keyset).sign(message))
+
+
+def verify(signing_key: bytes, message: bytes, signature: str) -> bool:
+    """Did the owner of ``signing_key`` sign ``message``? Never raises."""
+    try:
+        Ed25519PublicKey.from_public_bytes(signing_key).verify(
+            base64.b64decode(signature, validate=True), message)
+        return True
+    except Exception:
+        return False
+
+
 # ===========================================================================
 # PMV3: a vault's entries under its own key
 # ===========================================================================