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Python: Fix flow through deepcopy
Or, more generally, any copy step, as these presumably do not preserve object identity. (Arguably, `copy` could still be susceptible to interior mutability, but I think that's outside the scope of this query anyway.)
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‎python/ql/src/semmle/python/functions/ModificationOfParameterWithDefault.qll

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@@ -8,6 +8,7 @@
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private import python
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import semmle.python.dataflow.new.DataFlow
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private import semmle.python.dataflow.new.internal.TaintTrackingPrivate as TTP
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/**
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* Provides a data-flow configuration for detecting modifications of a parameters default value.
@@ -69,6 +70,10 @@ module ModificationOfParameterWithDefault {
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// if we are tracking a empty default, then it is ok to modify non-empty values,
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// so our tracking ends at those.
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state = false and node instanceof MustBeNonEmpty
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or
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// the target of a copy step is (presumably) a different object, and hence modifications of
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// this object no longer matter for the purposes of this query.
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TTP::copyStep(_, node) and state in [true, false]
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}
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}
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‎python/ql/test/query-tests/Functions/ModificationOfParameterWithDefault/ModificationOfParameterWithDefault.expected

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@@ -1,12 +1,4 @@
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edges
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:128:14:128:14 | ControlFlowNode for x | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:34:149:34 | ControlFlowNode for x |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:128:14:128:14 | ControlFlowNode for x | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:170:21:170:21 | ControlFlowNode for y |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:13:149:13 | ControlFlowNode for y | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:178:12:178:12 | ControlFlowNode for y |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:17:149:41 | ControlFlowNode for _deepcopy_atomic() | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:13:149:13 | ControlFlowNode for y |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:34:149:34 | ControlFlowNode for x | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:17:149:41 | ControlFlowNode for _deepcopy_atomic() |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:34:149:34 | ControlFlowNode for x | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:182:22:182:22 | ControlFlowNode for x |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:170:21:170:21 | ControlFlowNode for y | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:178:12:178:12 | ControlFlowNode for y |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:182:22:182:22 | ControlFlowNode for x | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:183:12:183:12 | ControlFlowNode for x |
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| test.py:2:12:2:12 | ControlFlowNode for l | test.py:3:5:3:5 | ControlFlowNode for l |
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| test.py:7:11:7:11 | ControlFlowNode for l | test.py:8:5:8:5 | ControlFlowNode for l |
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| test.py:12:14:12:14 | ControlFlowNode for l | test.py:13:9:13:9 | ControlFlowNode for l |
@@ -48,20 +40,7 @@ edges
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| test.py:195:28:195:28 | ControlFlowNode for x | test.py:181:28:181:28 | ControlFlowNode for x |
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| test.py:197:18:197:18 | ControlFlowNode for x | test.py:198:28:198:28 | ControlFlowNode for x |
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| test.py:198:28:198:28 | ControlFlowNode for x | test.py:181:28:181:28 | ControlFlowNode for x |
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| test.py:216:30:216:30 | ControlFlowNode for x | test.py:217:18:217:18 | ControlFlowNode for x |
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| test.py:217:5:217:5 | ControlFlowNode for y | test.py:218:5:218:5 | ControlFlowNode for y |
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| test.py:217:9:217:19 | ControlFlowNode for deepcopy() | test.py:217:5:217:5 | ControlFlowNode for y |
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| test.py:217:18:217:18 | ControlFlowNode for x | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:128:14:128:14 | ControlFlowNode for x |
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| test.py:217:18:217:18 | ControlFlowNode for x | test.py:217:9:217:19 | ControlFlowNode for deepcopy() |
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nodes
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:128:14:128:14 | ControlFlowNode for x | semmle.label | ControlFlowNode for x |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:13:149:13 | ControlFlowNode for y | semmle.label | ControlFlowNode for y |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:17:149:41 | ControlFlowNode for _deepcopy_atomic() | semmle.label | ControlFlowNode for _deepcopy_atomic() |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:34:149:34 | ControlFlowNode for x | semmle.label | ControlFlowNode for x |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:170:21:170:21 | ControlFlowNode for y | semmle.label | ControlFlowNode for y |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:178:12:178:12 | ControlFlowNode for y | semmle.label | ControlFlowNode for y |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:182:22:182:22 | ControlFlowNode for x | semmle.label | ControlFlowNode for x |
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:183:12:183:12 | ControlFlowNode for x | semmle.label | ControlFlowNode for x |
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| test.py:2:12:2:12 | ControlFlowNode for l | semmle.label | ControlFlowNode for l |
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| test.py:3:5:3:5 | ControlFlowNode for l | semmle.label | ControlFlowNode for l |
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| test.py:7:11:7:11 | ControlFlowNode for l | semmle.label | ControlFlowNode for l |
@@ -128,14 +107,7 @@ nodes
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| test.py:195:28:195:28 | ControlFlowNode for x | semmle.label | ControlFlowNode for x |
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| test.py:197:18:197:18 | ControlFlowNode for x | semmle.label | ControlFlowNode for x |
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| test.py:198:28:198:28 | ControlFlowNode for x | semmle.label | ControlFlowNode for x |
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| test.py:216:30:216:30 | ControlFlowNode for x | semmle.label | ControlFlowNode for x |
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| test.py:217:5:217:5 | ControlFlowNode for y | semmle.label | ControlFlowNode for y |
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| test.py:217:9:217:19 | ControlFlowNode for deepcopy() | semmle.label | ControlFlowNode for deepcopy() |
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| test.py:217:18:217:18 | ControlFlowNode for x | semmle.label | ControlFlowNode for x |
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| test.py:218:5:218:5 | ControlFlowNode for y | semmle.label | ControlFlowNode for y |
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subpaths
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| file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:34:149:34 | ControlFlowNode for x | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:182:22:182:22 | ControlFlowNode for x | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:183:12:183:12 | ControlFlowNode for x | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:149:17:149:41 | ControlFlowNode for _deepcopy_atomic() |
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| test.py:217:18:217:18 | ControlFlowNode for x | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:128:14:128:14 | ControlFlowNode for x | file:///usr/local/python/3.10.13/lib/python3.10/copy.py:178:12:178:12 | ControlFlowNode for y | test.py:217:9:217:19 | ControlFlowNode for deepcopy() |
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#select
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| test.py:3:5:3:5 | ControlFlowNode for l | test.py:2:12:2:12 | ControlFlowNode for l | test.py:3:5:3:5 | ControlFlowNode for l | This expression mutates a $@. | test.py:2:12:2:12 | ControlFlowNode for l | default value |
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| test.py:8:5:8:5 | ControlFlowNode for l | test.py:7:11:7:11 | ControlFlowNode for l | test.py:8:5:8:5 | ControlFlowNode for l | This expression mutates a $@. | test.py:7:11:7:11 | ControlFlowNode for l | default value |
@@ -166,4 +138,3 @@ subpaths
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| test.py:185:9:185:9 | ControlFlowNode for x | test.py:197:18:197:18 | ControlFlowNode for x | test.py:185:9:185:9 | ControlFlowNode for x | This expression mutates a $@. | test.py:197:18:197:18 | ControlFlowNode for x | default value |
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| test.py:187:9:187:9 | ControlFlowNode for x | test.py:194:18:194:18 | ControlFlowNode for x | test.py:187:9:187:9 | ControlFlowNode for x | This expression mutates a $@. | test.py:194:18:194:18 | ControlFlowNode for x | default value |
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| test.py:187:9:187:9 | ControlFlowNode for x | test.py:197:18:197:18 | ControlFlowNode for x | test.py:187:9:187:9 | ControlFlowNode for x | This expression mutates a $@. | test.py:197:18:197:18 | ControlFlowNode for x | default value |
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| test.py:218:5:218:5 | ControlFlowNode for y | test.py:216:30:216:30 | ControlFlowNode for x | test.py:218:5:218:5 | ControlFlowNode for y | This expression mutates a $@. | test.py:216:30:216:30 | ControlFlowNode for x | default value |

‎python/ql/test/query-tests/Functions/ModificationOfParameterWithDefault/test.py

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@@ -215,4 +215,4 @@ def flow_from_within_deepcopy_fp():
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def flow_through_deepcopy_fp(x=[]):
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y = deepcopy(x)
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y.append(1) #$ SPURIOUS: modification=y
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y.append(1)

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