fix(auth): login-flow provisioning — public login_url + session app passwords

Two fixes surfaced while testing Login Flow v2 provisioning behind a split
internal/external host (Docker: server↔Nextcloud over http://app, browser
over http://localhost:8080):

1. login_url pointed at the internal host. Nextcloud builds the login URL
   from the request host, so the browser-facing URL came back as
   http://app/login/v2/flow/... — unreachable from the user's browser. The
   poll endpoint was already rewritten to the internal host (correct, the
   server polls it); now LoginFlowV2Client also rewrites the login_url origin
   to settings.nextcloud_public_issuer_url when set (passed at all 5
   construction sites). When unset, behaviour is unchanged.

2. The app-password format guard rejected raw session tokens. core/
   getapppassword returns a long alphanumeric token, not the dashed 25-char
   Security-settings format, so the dashed-only regex 400'd the one-click
   opt-in handoff. Relax APP_PASSWORD_PATTERN to `^[a-zA-Z0-9-]{20,256}$`;
   the authoritative validation is still the BasicAuth check against Nextcloud.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/api/passwords.py

@@ -30,9 +30,11 @@ from ..http import nextcloud_httpx_client
 logger = logging.getLogger(__name__)
 
 # App password format regex (Nextcloud format: xxxxx-xxxxx-xxxxx-xxxxx-xxxxx)
-APP_PASSWORD_PATTERN = re.compile(
-    r"^[a-zA-Z0-9]{5}-[a-zA-Z0-9]{5}-[a-zA-Z0-9]{5}-[a-zA-Z0-9]{5}-[a-zA-Z0-9]{5}$"
-)
+# Shape guard only — the authoritative check is the BasicAuth validation
+# against Nextcloud below. Accepts both the dashed format a user copies from
+# Security settings (xxxxx-xxxxx-xxxxx-xxxxx-xxxxx) and the raw token returned
+# by the one-click ``core/getapppassword`` flow (a long alphanumeric string).
+APP_PASSWORD_PATTERN = re.compile(r"^[a-zA-Z0-9-]{20,256}$")
 
 # Timeout for Nextcloud API validation requests (seconds)
 NEXTCLOUD_VALIDATION_TIMEOUT = 10.0

nextcloud_mcp_server/auth/login_flow.py

@@ -68,17 +68,27 @@ class LoginFlowV2Client:
     2. Poll for completion to receive the app password
 
     Args:
-        nextcloud_host: Base URL of the Nextcloud instance
+        nextcloud_host: Base URL of the Nextcloud instance, reachable by this
+            server (may be an internal/Docker hostname, e.g. http://app:80).
         verify_ssl: SSL verification setting (True, False, or SSLContext)
+        public_host: Externally-reachable Nextcloud base URL for the
+            browser-facing login URL (e.g. https://cloud.example.com). When the
+            server talks to Nextcloud over an internal hostname, Nextcloud
+            builds the login URL with that internal host — unusable in the
+            user's browser. If set, the login URL's origin is rewritten to this
+            public host. When None, the login URL is returned unchanged
+            (correct when nextcloud_host is already the public URL).
     """
 
     def __init__(
         self,
         nextcloud_host: str,
         verify_ssl: bool | ssl.SSLContext = True,
+        public_host: str | None = None,
     ):
         self.nextcloud_host = nextcloud_host.rstrip("/")
         self.verify_ssl = verify_ssl
+        self.public_host = public_host.rstrip("/") if public_host else None
 
     async def initiate(
         self, user_agent: str = "nextcloud-mcp-server"
@@ -119,8 +129,23 @@ class LoginFlowV2Client:
             # so server-side polling works across Docker networks.
             poll_endpoint = self._rewrite_to_nextcloud_host(raw_poll_endpoint)
 
+            # The login URL is opened in the *user's browser*, so it must use
+            # the externally-reachable host. Nextcloud builds it from the
+            # request host (our internal nextcloud_host), so rewrite it to the
+            # public host when one is configured (internal != external).
+            login_url = data["login"]
+            if self.public_host:
+                rewritten = rewrite_url_origin(login_url, self.public_host)
+                if rewritten != login_url:
+                    logger.debug(
+                        "Rewrote Login Flow v2 login_url to public host: %s → %s",
+                        login_url,
+                        rewritten,
+                    )
+                login_url = rewritten
+
             result = LoginFlowInitResponse(
-                login_url=data["login"],
+                login_url=login_url,
                 poll_endpoint=poll_endpoint,
                 poll_token=poll_data["token"],
             )

nextcloud_mcp_server/auth/provision_routes.py

@@ -74,6 +74,7 @@ async def _poll_and_store(provision_id: str) -> None:
     flow_client = LoginFlowV2Client(
         nextcloud_host=nextcloud_host,
         verify_ssl=get_nextcloud_ssl_verify(),
+        public_host=settings.nextcloud_public_issuer_url,
     )
 
     poll_endpoint = session["poll_endpoint"]
@@ -205,6 +206,7 @@ async def provision_page(
         flow_client = LoginFlowV2Client(
             nextcloud_host=nextcloud_host,
             verify_ssl=get_nextcloud_ssl_verify(),
+            public_host=settings.nextcloud_public_issuer_url,
         )
         init_response = await flow_client.initiate()
     except Exception as e:

nextcloud_mcp_server/server/auth_tools.py

@@ -113,6 +113,7 @@ def register_auth_tools(mcp: FastMCP) -> None:
             flow_client = LoginFlowV2Client(
                 nextcloud_host=nextcloud_host,
                 verify_ssl=get_nextcloud_ssl_verify(),
+                public_host=settings.nextcloud_public_issuer_url,
             )
             init_response = await flow_client.initiate()
         except Exception as e:
@@ -258,6 +259,7 @@ def register_auth_tools(mcp: FastMCP) -> None:
             flow_client = LoginFlowV2Client(
                 nextcloud_host=nextcloud_host,
                 verify_ssl=get_nextcloud_ssl_verify(),
+                public_host=settings.nextcloud_public_issuer_url,
             )
             poll_result = await flow_client.poll(
                 poll_endpoint=session["poll_endpoint"],
@@ -431,6 +433,7 @@ def register_auth_tools(mcp: FastMCP) -> None:
             flow_client = LoginFlowV2Client(
                 nextcloud_host=nextcloud_host,
                 verify_ssl=get_nextcloud_ssl_verify(),
+                public_host=settings.nextcloud_public_issuer_url,
             )
             init_response = await flow_client.initiate()
         except Exception as e: