Add 'fiscal/' from commit '102ba84500dbd9655a0471288c3e278652593ca9'

git-subtree-dir: fiscal
git-subtree-mainline: d95165fc8f
git-subtree-split: 102ba84500

fiscal/central/app/enrollment.py

@@ -0,0 +1,136 @@
+"""Secrets and package bundling for Agent distribution.
+
+Two independent secrets guard the distribution flow, both random(256 bits),
+single-use and short-TTL, both stored only as SHA-256 hashes:
+
+- the *download* token: embedded in the shareable link an operator hands to
+  whoever installs the Agent (or clicked directly, authenticated, from the
+  panel);
+- the *enrollment* token: embedded inside the downloaded bundle as
+  `enrollment.json`, consumed exactly once by `POST /v1/agents/enroll`.
+
+Neither token is ever the Agent's own permanent Bearer token (issued only
+after a successful enrollment) and neither is ever logged or audited in
+plaintext.
+"""
+from __future__ import annotations
+
+import hashlib
+import hmac
+import io
+import json
+import re
+import secrets
+import zipfile
+from dataclasses import dataclass
+
+
+class EnrollmentRejected(Exception):
+    def __init__(self, reason: str):
+        super().__init__(reason)
+        self.reason = reason
+
+
+def new_token() -> str:
+    """256 bits of randomness, URL-safe — usable directly in a link or a JSON field."""
+    return secrets.token_urlsafe(32)
+
+
+# ---- installation code (XXXX-XXXX-XXXX-XXXX) ----
+#
+# A 16-character Crockford Base32 code = 16 * 5 = 80 bits of entropy. The
+# alphabet deliberately excludes I/L/O/U (ambiguous when retyped by a human);
+# the same alphabet is used so a code cannot contain those letters.
+
+INSTALL_CODE_ALPHABET = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"
+_INSTALL_CODE_GROUPS = 4
+_INSTALL_CODE_PER_GROUP = 4
+_INSTALL_CODE_LENGTH = _INSTALL_CODE_GROUPS * _INSTALL_CODE_PER_GROUP
+# Crockford transliteration for input normalization: O -> 0, I/L -> 1.
+_INSTALL_CODE_TRANSLIT = str.maketrans({"O": "0", "I": "1", "L": "1"})
+_INSTALL_CODE_RE = re.compile(
+    r"^[" + re.escape(INSTALL_CODE_ALPHABET) + r"]{" + str(_INSTALL_CODE_LENGTH) + r"}$"
+)
+
+
+def generate_install_code() -> str:
+    """Return a fresh installation code formatted XXXX-XXXX-XXXX-XXXX."""
+    chars = "".join(secrets.choice(INSTALL_CODE_ALPHABET) for _ in range(_INSTALL_CODE_LENGTH))
+    return "-".join(
+        chars[i : i + _INSTALL_CODE_PER_GROUP] for i in range(0, _INSTALL_CODE_LENGTH, _INSTALL_CODE_PER_GROUP)
+    )
+
+
+def normalize_install_code(text: str | None) -> str:
+    """Upper-case, drop hyphen/space separators and map Crockford lookalikes,
+    so a human-typed code normalizes to the same digest regardless of how it
+    was entered. Raises ValueError if the result isn't a valid code."""
+    if not text:
+        raise ValueError("empty install code")
+    clean = "".join(ch for ch in text.upper().translate(_INSTALL_CODE_TRANSLIT) if ch.isalnum())
+    if not _INSTALL_CODE_RE.match(clean):
+        raise ValueError(f"invalid install code: {text!r}")
+    return clean
+
+
+def install_code_digest(code: str) -> str:
+    """Hash a normalized install code. Only the hash is ever persisted; the
+    plaintext code exists only in the operator's clipboard/UI and the EXE's
+    memory for the brief instant it is sent to the Hub."""
+    return token_digest(normalize_install_code(code))
+
+
+def valid_install_code(text: str | None) -> bool:
+    try:
+        normalize_install_code(text)
+        return True
+    except ValueError:
+        return False
+
+
+def token_digest(token: str) -> str:
+    return hashlib.sha256(token.encode()).hexdigest()
+
+
+def token_matches(token: str | None, stored_hash: str | None) -> bool:
+    if not token or not stored_hash:
+        return False
+    return hmac.compare_digest(token_digest(token), stored_hash)
+
+
+ENROLLMENT_UUID_RE = re.compile(r"^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$")
+
+
+def valid_uuid(value: str | None) -> bool:
+    return bool(value) and bool(ENROLLMENT_UUID_RE.match(value))
+
+
+@dataclass(frozen=True)
+class BundlePlan:
+    hub_url: str
+    enrollment_uuid: str
+    enrollment_token: str
+    enroll_path: str = "/v1/agents/enroll"
+
+
+def build_bundle(release_zip_bytes: bytes, plan: BundlePlan) -> bytes:
+    """Return a new zip = the release zip's entries plus one
+    `<package-root>/enrollment.json` holding only temporary, single-use data.
+    Never a permanent credential — that is issued only once enrollment succeeds."""
+    with zipfile.ZipFile(io.BytesIO(release_zip_bytes)) as source:
+        names = source.namelist()
+        if not names:
+            raise EnrollmentRejected("EMPTY_RELEASE_PACKAGE")
+        root = names[0].split("/", 1)[0]
+        out = io.BytesIO()
+        with zipfile.ZipFile(out, "w", zipfile.ZIP_DEFLATED) as dest:
+            for name in names:
+                dest.writestr(name, source.read(name))
+            payload = {
+                "installation_id": plan.enrollment_uuid,
+                "enrollment_token": plan.enrollment_token,
+                "hub_url": plan.hub_url,
+                "enroll_path": plan.enroll_path,
+            }
+            dest.writestr(f"{root}/enrollment.json", json.dumps(payload, indent=1))
+    return out.getvalue()