fix: set private trace mask before namespace tracer startup

Author: siriushex

AI_NOTES.md

@@ -1,5 +1,12 @@
 # Synthetic Native Login Protocol - 2026-10-14
 
+- Separate-trace no-client preflight refused trace metadata before compilation.
+  Set077 explicitly in the trusted namespace setup before the tracer starts,
+  rather than relying on the host wrapper mask or the later Python setup.
+  Retained0600 admission and added bounded mode/owner/link diagnostics; the
+  diagnostic regression failed first. All53 local tooling cases pass; actual
+  retry pending, not an authorization/runtime readiness claim.
+
 - The constrained native process reached the final syscall audit after the
   cancel scenario's initialize/code/poll/wrong-ID/correct-ID/repeat/silence checks.
   The final audit refused an execution record; protocol suite not passed. Split

tools/session_store/protocol_smoke.py

@@ -156,7 +156,9 @@ def read_trace(prefix: Path) -> str:
         if (not re.fullmatch(re.escape(prefix.name) + r"\.[0-9]+", file.name)
                 or not stat.S_ISREG(metadata.st_mode) or metadata.st_uid != os.geteuid()
                 or stat.S_IMODE(metadata.st_mode) != 0o600 or metadata.st_nlink != 1):
-            raise ValueError("process trace metadata rejected")
+            raise ValueError(f"process trace metadata rejected: {file.name[:128]} "
+                             f"mode={stat.S_IMODE(metadata.st_mode):04o} uid={metadata.st_uid} "
+                             f"links={metadata.st_nlink}")
         total += metadata.st_size
         if total > 1024 * 1024:
             raise ValueError("trace byte budget exceeded")

tools/session_store/protocol_smoke.sh

@@ -50,7 +50,7 @@ timeout --signal=TERM --kill-after=5s 100s sudo -n setpriv --no-new-privs bwrap
   --ro-bind "$scratch/peer.pem" /work/peer.pem --ro-bind "$scratch/peer.key" /work/peer.key \
   --ro-bind "$scratch/wrong.pem" /work/wrong.pem --ro-bind "$scratch/wrong.key" /work/wrong.key \
   --chdir /work --clearenv --setenv PATH /usr/bin:/bin \
-  -- /bin/sh -eu -c 'ip link set lo up; exec setpriv --reuid=65534 --regid=65534 --clear-groups \
+  -- /bin/sh -eu -c 'umask 077; ip link set lo up; exec setpriv --reuid=65534 --regid=65534 --clear-groups \
      --bounding-set=-all --inh-caps=-all --ambient-caps=-all --no-new-privs \
      "$@"' session-setup "${check_command[@]}" > "$scratch/receipt.json" || {
   cat "$scratch/receipt.json"

tools/session_store/test_protocol_smoke.py

@@ -213,7 +213,7 @@ def test_per_process_trace_is_read_without_interleaved_syscalls(self):
                 file.chmod(0o600)
             self.assertEqual(self.module.read_trace(prefix), "exec complete\nconnect complete\n")
             (prefix.parent / "trace.12").chmod(0o644)
-            with self.assertRaises(ValueError):
+            with self.assertRaisesRegex(ValueError, "process trace metadata rejected.*mode=0644"):
                 self.module.read_trace(prefix)
             (prefix.parent / "trace.12").chmod(0o600)
             (prefix.parent / "trace.12").write_bytes(b"x" * (1024 * 1024 + 1))