fix(interpreter): add max_subst_depth limit to prevent OOM from nested $()#1107
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fix(interpreter): add max_subst_depth limit to prevent OOM from nested $()#1107
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…d $() Each command substitution level clones the full interpreter state (variables, arrays, functions, etc.), so memory grows as depth × state_size. Previously, command substitution shared the function depth counter (max_function_depth=100), which allowed deep nesting to exhaust memory. Add a dedicated max_subst_depth limit (default 32) with its own counter. This bounds memory consumption from nested $(...) chains while keeping the function depth limit independent. - Add max_subst_depth field to ExecutionLimits (default 32) - Add subst_depth counter to ExecutionCounters with push_subst/pop_subst - Switch CommandSubstitution handler to use subst depth tracking - Harden arithmetic_fuzz target with tighter limits - Update blackbox_security_tests to set max_subst_depth - Add regression tests with fuzz crash input from #1088 - Add TM-DOS-088 to threat model Closes #1088
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Summary
max_subst_depthlimit (default 32) toExecutionLimitsto prevent OOM from deeply nested command substitutions$(...)level clones the full interpreter state — memory grows as depth × state_sizemax_function_depthcounter (default 100) was too generous for expensive state-cloning operationsarithmetic_fuzztarget with tighter resource limitsChanges
limits.rs: newmax_subst_depthfield,subst_depthcounter,push_subst/pop_substmethods,MaxSubstDeptherror variantinterpreter/mod.rs: switch both command substitution paths frompush_function/pop_functiontopush_subst/pop_substarithmetic_fuzz.rs: addmax_function_depth(10),max_subst_depth(5),max_stdout_bytes(4096),max_stderr_bytes(4096)blackbox_security_tests.rs: setmax_subst_depthintight_bash()anddos_bash()helperssubst_depth_limit_tests.rs: 3 regression tests including decoded fuzz crash inputspecs/006-threat-model.md: add TM-DOS-088Test plan
cargo test --test subst_depth_limit_tests— 3 new tests passcargo test --test blackbox_security_tests— 78 tests pass (previously stack-overflowed)cargo test --all-features -- --skip ssh_supabase— all passcargo clippy --all-targets --all-features -- -D warnings— cleancargo fmt --check— cleanCloses #1088