01734e5449
Default fuzzy reconcile threshold to 0 and refuse merges when digit runs differ so numbered labels like Bay 311 never bind to Bay 310. Keep edit forms from clearing saved model fields when category filtering hides untyped rows. Includes in-progress computers policy and endpoints command feature work.
97 lines
3.7 KiB
Python
97 lines
3.7 KiB
Python
"""Boolean scope evaluation for Configuration Policies.
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A policy's scopejson is a small typed boolean AST over two endpoint dimensions,
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PC type and installed application. This module is the ONLY place that interprets
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that AST: it validates the shape (known node types, bounded depth) and evaluates
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a validated tree against a resolved endpoint context.
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Node grammar (all dict nodes carry a "type"):
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{"type": "and", "nodes": [<node>, ...]}
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{"type": "or", "nodes": [<node>, ...]}
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{"type": "not", "node": <node>}
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{"type": "pctype", "id": <computertypeid:int>}
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{"type": "app", "id": <appid:int>}
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{"type": "true"} # matches everything (an unscoped/global policy)
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Kept pure and dependency-free (no db, no Flask) so it is trivially unit-tested
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and so a future GE-Enforce assembly engine can reuse the exact same evaluator on
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the exact same AST when it composes policies.
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"""
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# Bound the tree so a hand-crafted or imported AST cannot cause pathological
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# recursion. Ten levels is far past any policy a human would author.
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MAX_SCOPE_DEPTH = 10
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_LOGICAL = {'and', 'or', 'not'}
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_LEAF = {'pctype', 'app', 'true'}
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class ScopeError(ValueError):
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"""Raised when a scope AST is malformed. Carries a human-readable reason."""
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def validate_scope(node, _depth=0):
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"""Validate a scope AST, raising ScopeError on any problem.
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Returns None on success. Call this at write time (CRUD) so a bad tree never
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reaches the database; evaluate_scope then trusts the stored shape.
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"""
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if _depth > MAX_SCOPE_DEPTH:
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raise ScopeError(f'scope nested deeper than {MAX_SCOPE_DEPTH} levels')
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if not isinstance(node, dict):
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raise ScopeError('scope node must be an object')
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ntype = node.get('type')
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if ntype not in _LOGICAL and ntype not in _LEAF:
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raise ScopeError(f'unknown scope node type: {ntype!r}')
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if ntype in ('and', 'or'):
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nodes = node.get('nodes')
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if not isinstance(nodes, list) or not nodes:
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raise ScopeError(f'{ntype} requires a non-empty "nodes" list')
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for child in nodes:
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validate_scope(child, _depth + 1)
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elif ntype == 'not':
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child = node.get('node')
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if child is None:
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raise ScopeError('not requires a "node"')
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validate_scope(child, _depth + 1)
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elif ntype in ('pctype', 'app'):
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ident = node.get('id')
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if not isinstance(ident, int) or isinstance(ident, bool):
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raise ScopeError(f'{ntype} requires an integer "id"')
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# 'true' carries no payload.
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def evaluate_scope(node, context):
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"""Evaluate a validated scope AST against an endpoint context.
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context is expected to expose:
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context['computertypeid'] -> int or None
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context['appids'] -> set/collection of installed appids
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Returns True when the endpoint falls in scope. An empty/None scope means the
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policy is unscoped and matches everything (same as {"type": "true"}), which
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keeps a freshly-created policy usable before a scope is drawn.
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"""
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if node is None:
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return True
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ntype = node['type']
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if ntype == 'true':
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return True
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if ntype == 'and':
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return all(evaluate_scope(child, context) for child in node['nodes'])
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if ntype == 'or':
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return any(evaluate_scope(child, context) for child in node['nodes'])
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if ntype == 'not':
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return not evaluate_scope(node['node'], context)
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if ntype == 'pctype':
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return context.get('computertypeid') == node['id']
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if ntype == 'app':
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return node['id'] in (context.get('appids') or ())
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# validate_scope should have caught this; be strict rather than silently
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# matching an endpoint against an unknown node.
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raise ScopeError(f'unknown scope node type at evaluation: {ntype!r}')
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