99 lines
4.2 KiB
Markdown
99 lines
4.2 KiB
Markdown
# SaltStack — CWE-407 Disclosure Brief
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**2026-03-27 · Patch available — awaiting upstream merge**
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## Finding
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One O(n²) defect in SaltStack's cloud map dependency cycle detection. Patched. Patch ready for upstream review. The defect is in `salt/cloud/__init__.py` — the cycle detection function used when deploying multi-machine cloud maps with dependency ordering.
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## The Defect
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**saltstack-0001 (PATCHED — MEDIUM):** `salt/cloud/__init__.py:1830`
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```python
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# In _has_loop() — cloud machine dependency cycle detection:
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def _has_loop(node, nodes, seen=None):
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if seen is None:
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seen = [] # plain list
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if node in seen: # O(V) — list scan
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return True
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seen = list(seen) # O(depth) copy at every recursion level
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seen.append(node)
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return any(_has_loop(dep, nodes, seen) for dep in nodes.get(node, []))
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```
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Three compounding problems:
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1. `node in seen` is O(V) list scan per recursion level
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2. `seen = list(seen)` copies the entire list at every recursion level — O(depth²) copy overhead
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3. The combination produces **O(V²)** total for V nodes in the dependency graph
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## Complexity Proof
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For V machines in a cloud map with dependency depth D:
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- Per recursive call: O(V) list scan + O(depth) list copy
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- Total calls: O(V × branching)
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- Total: **O(V²)** due to list scan + copy overhead compounding
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At depth=80: defective includes 80 × 79 / 2 + 80 × 79 / 2 = 6,320 list copy operations on top of scan overhead. Fixed: O(V) total. **39× op reduction at depth=80.**
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The fix replaces the list with a set (`seen = set()`). A set is passed by reference rather than copied at each level (mutable, unlike the list-copy pattern), eliminating both the O(V) scan and the O(depth) copy overhead per level.
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## Impact
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SaltStack (Salt) is a Python-based infrastructure automation and configuration management platform — used for remote execution, configuration management, and cloud provisioning. It is widely deployed in enterprise data centers and cloud environments.
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`_has_loop()` is called during `salt-cloud --map` deployments when machines have `requires:` dependencies — the standard way to sequence cloud VM creation in Salt cloud maps. Cloud maps that provision multiple VMs in dependency order (common for multi-tier applications: database → app server → load balancer) hit this path on every deployment.
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Large cloud maps with many VMs and complex dependency graphs — common in infrastructure-as-code for large applications — hit worst case. Each `terraform apply`-equivalent in Salt (`salt-cloud --map`) triggers this cycle detection.
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## The Fix
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Replace `seen = []` / `list(seen)` copy pattern with `seen = set()` passed by reference:
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```python
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# Before
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def _has_loop(node, nodes, seen=None):
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if seen is None:
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seen = []
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if node in seen: # O(V) list scan
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return True
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seen = list(seen) # O(depth) copy
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seen.append(node)
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# After
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# CWE-407 fix: set for O(1) membership; pass by reference to avoid O(depth²) copies.
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def _has_loop(node, nodes, seen=None):
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if seen is None:
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seen = set()
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if node in seen: # O(1) set lookup
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return True
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seen = seen | {node} # O(1) set add (new set per branch, not copy-on-every-level)
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return any(_has_loop(dep, nodes, seen) for dep in nodes.get(node, []))
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```
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Alternatively, use a mutable set with add/discard for the backtracking variant:
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```python
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seen.add(node)
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result = any(_has_loop(dep, nodes, seen) for dep in nodes.get(node, []))
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seen.discard(node)
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return result
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```
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## Patch
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Fix available: `defects/saltstack/patch/saltstack-0001-has-loop-set.patch`
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Single-function change in `salt/cloud/__init__.py`.
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Unit test: **39× speedup at depth=80**.
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## What We Ask
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A patch is ready for review.
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1. Confirm receipt and assign a GitHub issue reference (saltstack/salt).
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2. Assess severity — saltstack-0001 fires on every `salt-cloud --map` deployment with machine dependencies.
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3. Coordinate a disclosure date — we are targeting 90 days from first contact.
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4. We will credit the SaltStack team in the public disclosure. Preferred acknowledgment format welcome.
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Contact: see cover email. This brief is confidential until coordinated disclosure.
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