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/**
* AST-based bash command analysis using tree-sitter.
*
* This module replaces the shell-quote + hand-rolled char-walker approach in
* bashSecurity.ts / commands.ts. Instead of detecting parser differentials
* one-by-one, we parse with tree-sitter-bash and walk the tree with an
* EXPLICIT allowlist of node types. Any node type not in the allowlist causes
* the entire command to be classified as 'too-complex', which means it goes
* through the normal permission prompt flow.
*
* The key design property is FAIL-CLOSED: we never interpret structure we
* don't understand. If tree-sitter produces a node we haven't explicitly
* allowlisted, we refuse to extract argv and the caller must ask the user.
*
* This is NOT a sandbox. It does not prevent dangerous commands from running.
* It answers exactly one question: "Can we produce a trustworthy argv[] for
* each simple command in this string?" If yes, downstream code can match
* argv[0] against permission rules and flag allowlists. If no, ask the user.
*/
import { SHELL_KEYWORDS } from './bashParser.js'
import type { Node } from './parser.js'
import { PARSE_ABORTED, parseCommandRaw } from './parser.js'
export type Redirect = {
op: '>' | '>>' | '<' | '<<' | '>&' | '>|' | '<&' | '&>' | '&>>' | '<<<'
target: string
fd?: number
}
export type SimpleCommand = {
/** argv[0] is the command name, rest are arguments with quotes already resolved */
argv: string[]
/** Leading VAR=val assignments */
envVars: { name: string; value: string }[]
/** Output/input redirects */
redirects: Redirect[]
/** Original source span for this command (for UI display) */
text: string
}
export type ParseForSecurityResult =
| { kind: 'simple'; commands: SimpleCommand[] }
| { kind: 'too-complex'; reason: string; nodeType?: string }
| { kind: 'parse-unavailable' }
/**
* Structural node types that represent composition of commands. We recurse
* through these to find the leaf `command` nodes. `program` is the root;
* `list` is `a && b || c`; `pipeline` is `a | b`; `redirected_statement`
* wraps a command with its redirects. Semicolon-separated commands appear
* as direct siblings under `program` (no wrapper node).
*/
const STRUCTURAL_TYPES = new Set([
'program',
'list',
'pipeline',
'redirected_statement',
])
/**
* Operator tokens that separate commands. These are leaf nodes that appear
* between commands in `list`/`pipeline`/`program` and carry no payload.
*/
const SEPARATOR_TYPES = new Set(['&&', '||', '|', ';', '&', '|&', '\n'])
/**
* Placeholder string used in outer argv when a $() is recursively extracted.
* The actual $() output is runtime-determined; the inner command(s) are
* checked against permission rules separately. Using a placeholder keeps
* the outer argv clean (no multi-line heredoc bodies polluting path
* extraction or triggering newline checks).
*/
const CMDSUB_PLACEHOLDER = '__CMDSUB_OUTPUT__'
/**
* Placeholder for simple_expansion ($VAR) references to variables set earlier
* in the same command via variable_assignment. Since we tracked the assignment,
* we know the var exists and its value is either a static string or
* __CMDSUB_OUTPUT__ (if set via $()). Either way, safe to substitute.
*/
const VAR_PLACEHOLDER = '__TRACKED_VAR__'
/**
* All placeholder strings. Used for defense-in-depth: if a varScope value
* contains ANY placeholder (exact or embedded), the value is NOT a pure
* literal and cannot be trusted as a bare argument. Covers composites like
* `VAR="prefix$(cmd)"` → `"prefix__CMDSUB_OUTPUT__"` — the substring check
* catches these where exact-match Set.has() would miss.
*
* Also catches user-typed literals that collide with placeholder strings:
* `VAR=__TRACKED_VAR__ && rm $VAR` — treated as non-literal (conservative).
*/
function containsAnyPlaceholder(value: string): boolean {
return value.includes(CMDSUB_PLACEHOLDER) || value.includes(VAR_PLACEHOLDER)
}
/**
* Unquoted $VAR in bash undergoes word-splitting (on $IFS: space/tab/NL)
* and pathname expansion (glob matching on * ? [). Our argv stores a
* single string — but at runtime bash may produce MULTIPLE args, or paths
* matched by a glob. A value containing these metacharacters cannot be
* trusted as a bare arg: `VAR="-rf /" && rm $VAR` → bash runs `rm -rf /`
* (two args) but our argv would have `['rm', '-rf /']` (one arg). Similarly
* `VAR="/etc/*" && cat $VAR` → bash expands to all /etc files.
*
* Inside double-quotes ("$VAR"), neither splitting nor globbing applies —
* the value IS a single literal argument.
*/
const BARE_VAR_UNSAFE_RE = /[ \t\n*?[]/
// stdbuf flag forms — hoisted from the wrapper-stripping while-loop
const STDBUF_SHORT_SEP_RE = /^-[ioe]$/
const STDBUF_SHORT_FUSED_RE = /^-[ioe]./
const STDBUF_LONG_RE = /^--(input|output|error)=/
/**
* Known-safe environment variables that bash sets automatically. Their values
* are controlled by the shell/OS, not arbitrary user input. Referencing these
* via $VAR is safe — the expansion is deterministic and doesn't introduce
* injection risk. Covers `$HOME`, `$PWD`, `$USER`, `$PATH`, `$SHELL`, etc.
* Intentionally small: only vars that are always set by bash/login and whose
* values are paths/names (not arbitrary content).
*/
const SAFE_ENV_VARS = new Set([
'HOME', // user's home directory
'PWD', // current working directory (bash maintains)
'OLDPWD', // previous directory
'USER', // current username
'LOGNAME', // login name
'SHELL', // user's login shell
'PATH', // executable search path
'HOSTNAME', // machine hostname
'UID', // user id
'EUID', // effective user id
'PPID', // parent process id
'RANDOM', // random number (bash builtin)
'SECONDS', // seconds since shell start
'LINENO', // current line number
'TMPDIR', // temp directory
// Special bash variables — always set, values are shell-controlled:
'BASH_VERSION', // bash version string
'BASHPID', // current bash process id
'SHLVL', // shell nesting level
'HISTFILE', // history file path
'IFS', // field separator (NOTE: only safe INSIDE strings; as bare arg
// $IFS is the classic injection primitive and the insideString
// gate in resolveSimpleExpansion correctly blocks it)
])
/**
* Special shell variables ($?, $$, $!, $#, $0-$9). tree-sitter uses
* `special_variable_name` for these (not `variable_name`). Values are
* shell-controlled: exit status, PIDs, positional args. Safe to resolve
* ONLY inside strings (same rationale as SAFE_ENV_VARS — as bare args
* their value IS the argument and might be a path/flag from $1 etc.).
*
* SECURITY: '@' and '*' are NOT in this set. Inside "...", they expand to
* the positional params — which are EMPTY in a fresh BashTool shell (how we
* always spawn). Returning VAR_PLACEHOLDER would lie: `git "push$*"` gives
* argv ['git','push__TRACKED_VAR__'] while bash passes ['git','push']. Deny
* rule Bash(git push:*) fails on both .text (raw `$*`) AND rebuilt argv
* (placeholder). With them removed, resolveSimpleExpansion falls through to
* tooComplex for `$*` / `$@`. `echo "args: $*"` becomes too-complex —
* acceptable (rare in BashTool usage; `"$@"` even rarer).
*/
const SPECIAL_VAR_NAMES = new Set([
'?', // exit status of last command
'$', // current shell PID
'!', // last background PID
'#', // number of positional params
'0', // script name
'-', // shell option flags
])
/**
* Node types that mean "this command cannot be statically analyzed." These
* either execute arbitrary code (substitutions, subshells, control flow) or
* expand to values we can't determine statically (parameter/arithmetic
* expansion, brace expressions).
*
* This set is not exhaustive — it documents KNOWN dangerous types. The real
* safety property is the allowlist in walkArgument/walkCommand: any type NOT
* explicitly handled there also triggers too-complex.
*/
const DANGEROUS_TYPES = new Set([
'command_substitution',
'process_substitution',
'expansion',
'simple_expansion',
'brace_expression',
'subshell',
'compound_statement',
'for_statement',
'while_statement',
'until_statement',
'if_statement',
'case_statement',
'function_definition',
'test_command',
'ansi_c_string',
'translated_string',
'herestring_redirect',
'heredoc_redirect',
])
/**
* Numeric IDs for analytics (logEvent doesn't accept strings). Index into
* DANGEROUS_TYPES. Append new entries at the end to keep IDs stable.
* 0 = unknown/other, -1 = ERROR (parse failure), -2 = pre-check.
*/
const DANGEROUS_TYPE_IDS = [...DANGEROUS_TYPES]
export function nodeTypeId(nodeType: string | undefined): number {
if (!nodeType) return -2
if (nodeType === 'ERROR') return -1
const i = DANGEROUS_TYPE_IDS.indexOf(nodeType)
return i >= 0 ? i + 1 : 0
}
/**
* Redirect operator tokens → canonical operator. tree-sitter produces these
* as child nodes of `file_redirect`.
*/
const REDIRECT_OPS: Record<string, Redirect['op']> = {
'>': '>',
'>>': '>>',
'<': '<',
'>&': '>&',
'<&': '<&',
'>|': '>|',
'&>': '&>',
'&>>': '&>>',
'<<<': '<<<',
}
/**
* Brace expansion pattern: {a,b} or {a..b}. Must have , or .. inside
* braces. We deliberately do NOT try to determine whether the opening brace
* is backslash-escaped: tree-sitter doesn't unescape backslashes, so
* distinguishing `\{a,b}` (escaped, literal) from `\\{a,b}` (literal
* backslash + expansion) would require reimplementing bash quote removal.
* Reject both — the escaped-brace case is rare and trivially rewritten
* with single quotes.
*/
const BRACE_EXPANSION_RE = /\{[^{}\s]*(,|\.\.)[^{}\s]*\}/
/**
* Control characters that bash silently drops but confuse static analysis.
* Includes CR (0x0D): tree-sitter treats CR as a word separator but bash's
* default IFS does not include CR, so tree-sitter and bash disagree on
* word boundaries.
*/
// eslint-disable-next-line no-control-regex
const CONTROL_CHAR_RE = /[\x00-\x08\x0B-\x1F\x7F]/
/**
* Unicode whitespace beyond ASCII. These render invisibly (or as regular
* spaces) in terminals so a user reviewing the command can't see them, but
* bash treats them as literal word characters. Blocks NBSP, zero-width
* spaces, line/paragraph separators, BOM.
*/
const UNICODE_WHITESPACE_RE =
/[\u00A0\u1680\u2000-\u200B\u2028\u2029\u202F\u205F\u3000\uFEFF]/
/**
* Backslash immediately before whitespace. bash treats `\ ` as a literal
* space inside the current word, but tree-sitter returns the raw text with
* the backslash still present. argv[0] from tree-sitter is `cat\ test`
* while bash runs `cat test` (with a literal space). Rather than
* reimplement bash's unescaping rules, we reject these — they're rare in
* practice and trivial to rewrite with quotes.
*
* Also matches `\` before newline (line continuation) when adjacent to a
* non-whitespace char. `tr\<NL>aceroute` — bash joins to `traceroute`, but
* tree-sitter splits into two words (differential). When `\<NL>` is preceded
* by whitespace (e.g. `foo && \<NL>bar`), there's no word to join — both
* parsers agree, so we allow it.
*/
const BACKSLASH_WHITESPACE_RE = /\\[ \t]|[^ \t\n\\]\\\n/
/**
* Zsh dynamic named directory expansion: ~[name]. In zsh this invokes the
* zsh_directory_name hook, which can run arbitrary code. bash treats it as
* a literal tilde followed by a glob character class. Since BashTool runs
* via the user's default shell (often zsh), reject conservatively.
*/
const ZSH_TILDE_BRACKET_RE = /~\[/
/**
* Zsh EQUALS expansion: word-initial `=cmd` expands to the absolute path of
* `cmd` (equivalent to `$(which cmd)`). `=curl evil.com` runs as
* `/usr/bin/curl evil.com`. tree-sitter parses `=curl` as a literal word, so
* a `Bash(curl:*)` deny rule matching on base command name won't see `curl`.
* Only matches word-initial `=` followed by a command-name char — `VAR=val`
* and `--flag=val` have `=` mid-word and are not expanded by zsh.
*/
const ZSH_EQUALS_EXPANSION_RE = /(?:^|[\s;&|])=[a-zA-Z_]/
/**
* Brace character combined with quote characters. Constructions like
* `{a'}',b}` use quoted braces inside brace expansion context to obfuscate
* the expansion from regex-based detection. In bash, `{a'}',b}` expands to
* `a} b` (the quoted `}` becomes literal inside the first alternative).
* These are hard to analyze correctly and have no legitimate use in
* commands we'd want to auto-allow.
*
* This check runs on a version of the command with `{` masked out of
* single-quoted and double-quoted spans, so JSON payloads like
* `curl -d '{"k":"v"}'` don't trigger a false positive. Brace expansion
* cannot occur inside quotes, so a `{` there can never start an obfuscation
* pattern. The quote characters themselves stay visible so `{a'}',b}` and
* `{@'{'0},...}` still match via the outer unquoted `{`.
*/
const BRACE_WITH_QUOTE_RE = /\{[^}]*['"]/
/**
* Mask `{` characters that appear inside single- or double-quoted contexts.
* Uses a single-pass bash-aware quote-state scanner instead of a regex.
*
* A naive regex (`/'[^']*'/g`) mis-detects spans when a `'` appears inside
* a double-quoted string: for `echo "it's" {a'}',b}`, it matches from the
* `'` in `it's` across to the `'` in `{a'}`, masking the unquoted `{` and
* producing a false negative. The scanner tracks actual bash quote state:
* `'` toggles single-quote only in unquoted context; `"` toggles
* double-quote only outside single quotes; `\` escapes the next char in
* unquoted context and escapes `"` / `\\` inside double quotes.
*
* Brace expansion is impossible in both quote contexts, so masking `{` in
* either is safe. Secondary defense: BRACE_EXPANSION_RE in walkArgument.
*/
function maskBracesInQuotedContexts(cmd: string): string {
// Fast path: no `{` → nothing to mask. Skips the char-by-char scan for
// the >90% of commands with no braces (`ls -la`, `git status`, etc).
if (!cmd.includes('{')) return cmd
const out: string[] = []
let inSingle = false
let inDouble = false
let i = 0
while (i < cmd.length) {
const c = cmd[i]!
if (inSingle) {
// Bash single quotes: no escapes, `'` always terminates.
if (c === "'") inSingle = false
out.push(c === '{' ? ' ' : c)
i++
10BC8
} else if (inDouble) {
// Bash double quotes: `\` escapes `"` and `\` (also `$`, backtick,
// newline — but those don't affect quote state so we let them pass).
if (c === '\\' && (cmd[i + 1] === '"' || cmd[i + 1] === '\\')) {
out.push(c, cmd[i + 1]!)
i += 2
} else {
if (c === '"') inDouble = false
out.push(c === '{' ? ' ' : c)
i++
}
} else {
// Unquoted: `\` escapes any next char.
if (c === '\\' && i + 1 < cmd.length) {
out.push(c, cmd[i + 1]!)
i += 2
} else {
if (c === "'") inSingle = true
else if (c === '"') inDouble = true
out.push(c)
i++
}
}
}
return out.join('')
}
const DOLLAR = String.fromCharCode(0x24)
/**
* Parse a bash command string and extract a flat list of simple commands.
* Returns 'too-complex' if the command uses any shell feature we can't
* statically analyze. Returns 'parse-unavailable' if tree-sitter WASM isn't
* loaded — caller should fall back to conservative behavior.
*/
export async function parseForSecurity(
cmd: string,
): Promise<ParseForSecurityResult> {
// parseCommandRaw('') returns null (falsy check), so short-circuit here.
// Don't use .trim() — it strips Unicode whitespace (\u00a0 etc.) which the
// pre-checks in parseForSecurityFromAst need to see and reject.
if (cmd === '') return { kind: 'simple', commands: [] }
const root = await parseCommandRaw(cmd)
return root === null
? { kind: 'parse-unavailable' }
: parseForSecurityFromAst(cmd, root)
}
/**
* Same as parseForSecurity but takes a pre-parsed AST root so callers that
* need the tree for other purposes can parse once and share. Pre-checks
* still run on `cmd` — they catch tree-sitter/bash differentials that a
* successful parse doesn't.
*/
export function parseForSecurityFromAst(
cmd: string,
root: Node | typeof PARSE_ABORTED,
): ParseForSecurityResult {
// Pre-checks: characters that cause tree-sitter and bash to disagree on
// word boundaries. These run before tree-sitter because they're the known
// tree-sitter/bash differentials. Everything after this point trusts
// tree-sitter's tokenization.
if (CONTROL_CHAR_RE.test(cmd)) {
return { kind: 'too-complex', reason: 'Contains control characters' }
}
if (UNICODE_WHITESPACE_RE.test(cmd)) {
return { kind: 'too-complex', reason: 'Contains Unicode whitespace' }
}
if (BACKSLASH_WHITESPACE_RE.test(cmd)) {
return {
kind: 'too-complex',
reason: 'Contains backslash-escaped whitespace',
}
}
if (ZSH_TILDE_BRACKET_RE.test(cmd)) {
return {
kind: 'too-complex',
reason: 'Contains zsh ~[ dynamic directory syntax',
}
}
if (ZSH_EQUALS_EXPANSION_RE.test(cmd)) {
return {
kind: 'too-complex',
reason: 'Contains zsh =cmd equals expansion',
}
}
if (BRACE_WITH_QUOTE_RE.test(maskBracesInQuotedContexts(cmd))) {
return {
kind: 'too-complex',
reason: 'Contains brace with quote character (expansion obfuscation)',
}
}
const trimmed = cmd.trim()
if (trimmed === '') {
return { kind: 'simple', commands: [] }
}
if (root === PARSE_ABORTED) {
// SECURITY: module loaded but parse aborted (timeout / node budget /
// panic). Adversarially triggerable — `(( a[0][0]... ))` with ~2800
// subscripts hits PARSE_TIMEOUT_MICROS under the 10K length limit.
// Previously indistinguishable from module-not-loaded → routed to
// legacy (parse-unavailable), which lacks EVAL_LIKE_BUILTINS — `trap`,
// `enable`, `hash` leaked with Bash(*). Fail closed: too-complex → ask.
return {
kind: 'too-complex',
reason:
'Parser aborted (timeout or resource limit) — possible adversarial input',
nodeType: 'PARSE_ABORT',
}
}
return walkProgram(root)
}
function walkProgram(root: Node): ParseForSecurityResult {
// ERROR-node check folded into collectCommands — any unhandled node type
// (including ERROR) falls through to tooComplex() in the default branch.
// Avoids a separate full-tree walk for error detection.
const commands: SimpleCommand[] = []
// Track variables assigned earlier in the same command. When a
// simple_expansion ($VAR) references a tracked var, we can substitute
// a placeholder instead of returning too-complex. Enables patterns like
// `NOW=$(date) && jq --arg now "$NOW" ...` — $NOW is known to be the
// $(date) output (already extracted as inner command).
const varScope = new Map<string, string>()
const err = collectCommands(root, commands, varScope)
if (err) return err
return { kind: 'simple', commands }
}
/**
* Recursively collect leaf `command` nodes from a structural wrapper node.
* Returns an error result on any disallowed node type, or null on success.
*/
function collectCommands(
node: Node,
commands: SimpleCommand[],
varScope: Map<string, string>,
): ParseForSecurityResult | null {
if (node.type === 'command') {
// Pass `commands` as the innerCommands accumulator — any $() extracted
// during walkCommand gets appended alongside the outer command.
const result = walkCommand(node, [], commands, varScope)
if (result.kind !== 'simple') return result
commands.push(...result.commands)
return null
}
if (node.type === 'redirected_statement') {
return walkRedirectedStatement(node, commands, varScope)
}
if (node.type === 'comment') {
return null
}
if (STRUCTURAL_TYPES.has(node.type)) {
// SECURITY: `||`, `|`, `|&`, `&` must NOT carry varScope linearly. In bash:
// `||` RHS runs conditionally → vars set there MAY not be set
// `|`/`|&` stages run in subshells → vars set there are NEVER visible after
// `&` LHS runs in a background subshell → same as above
// Flag-omission attack: `true || FLAG=--dry-run && cmd $FLAG` — bash skips
// the `||` RHS (FLAG unset → $FLAG empty), runs `cmd` WITHOUT --dry-run.
// With linear scope, our argv has ['cmd','--dry-run'] → looks SAFE → bypass.
//
// Fix: snapshot incoming scope at entry. After these separators, reset to
// the snapshot — vars set in clauses between separators don't leak. `scope`
// for clauses BETWEEN `&&`/`;` chains shares state (common `VAR=x && cmd
// $VAR`). `scope` crosses `||`/`|`/`&` as the pre-structure snapshot only.
//
// `&&` and `;` DO carry scope: `VAR=x && cmd $VAR` is sequential, VAR is set.
//
// NOTE: `scope` and `varScope` diverge after the first `||`/`|`/`&`. The
// caller's varScope is only mutated for the `&&`/`;` prefix — this is
// conservative (vars set in `A && B | C && D` leak A+B into caller, not
// C+D) but safe.
//
// Efficiency: snapshot is only needed if we hit `||`/`|`/`|&`/`&`. For
// the dominant case (`ls`, `git status` — no such separators), skip the
// Map alloc via a cheap pre-scan. For `pipeline`, node.type already tells
// us stages are subshells — copy once at entry, no snapshot needed (each
// reset uses the entry copy pattern via varScope, which is untouched).
const isPipeline = node.type === 'pipeline'
let needsSnapshot = false
if (!isPipeline) {
for (const c of node.children) {
if (c && (c.type === '||' || c.type === '&')) {
needsSnapshot = true
break
}
}
}
const snapshot = needsSnapshot ? new Map(varScope) : null
// For `pipeline`, ALL stages run in subshells — start with a copy so
// nothing mutates caller's scope. For `list`/`program`, the `&&`/`;`
// chain mutates caller's scope (sequential); fork only on `||`/`&`.
let scope = isPipeline ? new Map(varScope) : varScope
for (const child of node.children) {
if (!child) continue
if (SEPARATOR_TYPES.has(child.type)) {
if (
child.type === '||' ||
child.type === '|' ||
child.type === '|&' ||
child.type === '&'
) {
// For pipeline: varScope is untouched (we started with a copy).
// For list/program: snapshot is non-null (pre-scan set it).
// `|`/`|&` only appear under `pipeline` nodes; `||`/`&` under list.
scope = new Map(snapshot ?? varScope)
}
continue
}
const err = collectCommands(child, commands, scope)
if (err) return err
}
return null
}
if (node.type === 'negated_command') {
// `! cmd` inverts exit code only — doesn't execute code or affect
// argv. Recurse into the wrapped command. Common in CI: `! grep err`,
// `! test -f lock`, `! git diff --quiet`.
for (const child of node.children) {
if (!child) continue
if (child.type === '!') continue
return collectCommands(child, commands, varScope)
}
return null
}
if (node.type === 'declaration_command') {
// `export`/`local`/`readonly`/`declare`/`typeset`. tree-sitter emits
// these as declaration_command, not command, so they previously fell
// through to tooComplex. Values are validated via walkVariableAssignment:
// `$()` in the value is recursively extracted (inner command pushed to
// commands[], outer argv gets CMDSUB_PLACEHOLDER); other disallowed
// expansions still reject via walkArgument. argv[0] is the builtin name so
// `Bash(export:*)` rules match.
const argv: string[] = []
for (const child of node.children) {
if (!child) continue
switch (child.type) {
case 'export':
case 'local':
case 'readonly':
case 'declare':
case 'typeset':
argv.push(child.text)
break
case 'word':
case 'number':
case 'raw_string':
case 'string':
case 'concatenation': {
// Flags (`declare -r`), quoted names (`export "FOO=bar"`), numbers
// (`declare -i 42`). Mirrors walkCommand's argv handling — before
// this, `export "FOO=bar"` hit tooComplex on the `string` child.
// walkArgument validates each (expansions still reject).
const arg = walkArgument(child, commands, varScope)
if (typeof arg !== 'string') return arg
// SECURITY: declare/typeset/local flags that change assignment
// semantics break our static model. -n (nameref): `declare -n X=Y`
// then `$X` dereferences to $Y's VALUE — varScope stores 'Y'
// (target NAME), argv[0] shows 'Y' while bash runs whatever $Y
// holds. -i (integer): `declare -i X='a[$(cmd)]'` arithmetically
// evaluates the RHS at assignment time, running $(cmd) even from
// a single-quoted raw_string (same primitive walkArithmetic
// guards in $((…))). -a/-A (array): subscript arithmetic on
// assignment. -r/-x/-g/-p/-f/-F are inert. Check the resolved
// arg (not child.text) so `\-n` and quoted `-n` are caught.
// Scope to declare/typeset/local only: `export -n` means "remove
// export attribute" (not nameref), and export/readonly don't
// accept -i; readonly -a/-A rejects subscripted args as invalid
// identifiers so subscript-arith doesn't fire.
if (
(argv[0] === 'declare' ||
argv[0] === 'typeset' ||
argv[0] === 'local') &&
/^-[a-zA-Z]*[niaA]/.test(arg)
) {
return {
kind: 'too-complex',
reason: `declare flag ${arg} changes assignment semantics (nameref/integer/array)`,
nodeType: 'declaration_command',
}
}
// SECURITY: bare positional assignment with a subscript also
// evaluates — no -a/-i flag needed. `declare 'x[$(id)]=val'`
// implicitly creates an array element, arithmetically evaluating
// the subscript and running $(id). tree-sitter delivers the
// single-quoted form as a raw_string leaf so walkArgument sees
// only the literal text. Scoped to declare/typeset/local:
// export/readonly reject `[` in identifiers before eval.
if (
(argv[0] === 'declare' ||
argv[0] === 'typeset' ||
argv[0] === 'local') &&
arg[0] !== '-' &&
/^[^=]*\[/.test(arg)
) {
return {
kind: 'too-complex',
reason: `declare positional '${arg}' contains array subscript — bash evaluates $(cmd) in subscripts`,
nodeType: 'declaration_command',
}
}
argv.push(arg)
break
}
case 'variable_assignment': {
const ev = walkVariableAssignment(child, commands, varScope)
if ('kind' in ev) return ev
// export/declare assignments populate the scope so later $VAR refs resolve.
applyVarToScope(varScope, ev)
argv.push(`${ev.name}=${ev.value}`)
break
}
case 'variable_name':
// `export FOO` — bare name, no assignment.
argv.push(child.text)
break
default:
return tooComplex(child)
}
}
commands.push({ argv, envVars: [], redirects: [], text: node.text })
return null
}
if (node.type === 'variable_assignment') {
// Bare `VAR=value` at statement level (not a command env prefix).
// Sets a shell variable — no code execution, no filesystem I/O.
// The value is validated via walkVariableAssignment → walkArgument,
// so `VAR=$(evil)` still recursively extracts/rejects based on the
// inner command. Does NOT push to commands — a bare assignment needs
// no permission rule (it's inert). Common pattern: `VAR=x && cmd`
// where cmd references $VAR. ~35% of too-complex in top-5k ant cmds.
const ev = walkVariableAssignment(node, commands, varScope)
if ('kind' in ev) return ev
// Populate scope so later `$VAR` references resolve.
applyVarToScope(varScope, ev)
return null
}
if (node.type === 'for_statement') {
// `for VAR in WORD...; do BODY; done` — iterate BODY once per word.
// Body commands extracted once; every iteration runs the same commands.
//
// SECURITY: Loop var is ALWAYS treated as unknown-value (VAR_PLACEHOLDER).
// Even "static" iteration words can be:
// - Absolute paths: `for i in /etc/passwd; do rm $i; done` — body argv
// would have placeholder, path validation never sees /etc/passwd.
// - Globs: `for i in /etc/*; do rm $i; done` — `/etc/*` is a static word
// at parse time but bash expands it at runtime.
// - Flags: `for i in -rf /; do rm $i; done` — flag smuggling.
//
// VAR_PLACEHOLDER means bare `$i` in body → too-complex. Only
// string-embedding (`echo "item: $i"`) stays simple. This reverts some
// of the too-complex→simple rescues in the original PR — each one was a
// potential path-validation bypass.
let loopVar: string | null = null
let doGroup: Node | null = null
for (const child of node.children) {
if (!child) continue
if (child.type === 'variable_name') {
loopVar = child.text
} else if (child.type === 'do_group') {
doGroup = child
} else if (
child.type === 'for' ||
child.type === 'in' ||
child.type === 'select' ||
child.type === ';'
) {
continue // structural tokens
} else if (child.type === 'command_substitution') {
// `for i in $(seq 1 3)` — inner cmd IS extracted and rule-checked.
const err = collectCommandSubstitution(child, commands, varScope)
if (err) return err
} else {
// Iteration values — validated via walkArgument. Value discarded:
// body argv gets VAR_PLACEHOLDER regardless of the iteration words,
// and bare `$i` in body → too-complex (see SECURITY comment above).
// We still validate to reject e.g. `for i in $(cmd); do ...; done`
// where the iteration word itself is a disallowed expansion.
const arg = walkArgument(child, commands, varScope)
if (typeof arg !== 'string') return arg
}
}
if (loopVar === null || doGroup === null) return tooComplex(node)
// SECURITY: `for PS4 in '$(id)'; do set -x; :; done` sets PS4 directly
// via varScope.set below — walkVariableAssignment's PS4/IFS checks never
// fire. Trace-time RCE (PS4) or word-split bypass (IFS). No legit use.
if (loopVar === 'PS4' || loopVar === 'IFS') {
return {
kind: 'too-complex',
reason: `${loopVar} as loop variable bypasses assignment validation`,
nodeType: 'for_statement',
}
}
// SECURITY: Body uses a scope COPY — vars assigned inside the loop
// body don't leak to commands after `done`. The loop var itself is
// set in the REAL scope (bash semantics: $i still set after loop)
// and copied into the body scope. ALWAYS VAR_PLACEHOLDER — see above.
varScope.set(loopVar, VAR_PLACEHOLDER)
const bodyScope = new Map(varScope)
for (const c of doGroup.children) {
if (!c) continue
if (c.type === 'do' || c.type === 'done' || c.type === ';') continue
const err = collectCommands(c, commands, bodyScope)
if (err) return err
}
return null
}
if (node.type === 'if_statement' || node.type === 'while_statement') {
// `if COND; then BODY; [elif...; else...;] fi`
// `while COND; do BODY; done`
// Extract condition command(s) + all branch/body commands. All get
// checked against permission rules. `while read VAR` tracks VAR so
// body can reference $VAR.
//
// SECURITY: Branch bodies use scope COPIES — vars assigned inside a
// conditional branch (which may not execute) must not leak to commands
// after fi/done. `if false; then T=safe; fi && rm $T` must reject $T.
// Condition commands use the REAL varScope (they always run for the
// check, so assignments there are unconditional — e.g., `while read V`
// tracking must persist to the body copy).
//
// tree-sitter if_statement children: if, COND..., then, THEN-BODY...,
// [elif_clause...], [else_clause], fi. We distinguish condition from
// then-body by tracking whether we've seen the `then` token.
let seenThen = false
for (const child of node.children) {
if (!child) continue
if (
child.type === 'if' ||
child.type === 'fi' ||
child.type === 'else' ||
child.type === 'elif' ||
child.type === 'while' ||
child.type === 'until' ||
child.type === ';'
) {
continue
}
if (child.type === 'then') {
seenThen = true
continue
}
if (child.type === 'do_group') {
// while body: recurse with scope COPY (body assignments don't leak
// past done). The COPY contains any `read VAR` tracking from the
// condition (already in real varScope at this point).
const bodyScope = new Map(varScope)
for (const c of child.children) {
if (!c) continue
if (c.type === 'do' || c.type === 'done' || c.type === ';') continue
const err = collectCommands(c, commands, bodyScope)
if (err) return err
}
continue
}
if (child.type === 'elif_clause' || child.type === 'else_clause') {
// elif_clause: elif, cond, ;, then, body... / else_clause: else, body...
// Scope COPY — elif/else branch assignments don't leak past fi.
const branchScope = new Map(varScope)
for (const c of child.children) {
if (!c) continue
if (
c.type === 'elif' ||
c.type === 'else' ||
c.type === 'then' ||
c.type === ';'
) {
continue
}
const err = collectCommands(c, commands, branchScope)
if (err) return err
}
continue
}
// Condition (seenThen=false) or then-body (seenThen=true).
// Condition uses REAL varScope (always runs). Then-body uses a COPY.
// Special-case `while read VAR`: after condition `read VAR` is
// collected, track VAR in the REAL scope so the body COPY inherits it.
const targetScope = seenThen ? new Map(varScope) : varScope
const before = commands.length
const err = collectCommands(child, commands, targetScope)
if (err) return err
// If condition included `read VAR...`, track vars in REAL scope.
// read var value is UNKNOWN (stdin input) → use VAR_PLACEHOLDER
// (unknown-value sentinel, string-only).
if (!seenThen) {
for (let i = before; i < commands.length; i++) {
const c = commands[i]
if (c?.argv[0] === 'read') {
for (const a of c.argv.slice(1)) {
// Skip flags (-r, -d, etc.); track bare identifier args as var names.
if (!a.startsWith('-') && /^[A-Za-z_][A-Za-z0-9_]*$/.test(a)) {
// SECURITY: commands[] is a flat accumulator. `true || read
// VAR` in the condition: the list handler correctly uses a
// scope COPY for the ||-RHS (may not run), but `read VAR`
// IS still pushed to commands[] — we can't tell it was
// scope-isolated from here. Same for `echo | read VAR`
// (pipeline, subshell in bash) and `(read VAR)` (subshell).
// Overwriting a tracked literal with VAR_PLACEHOLDER hides
// path traversal: `VAR=../../etc/passwd && if true || read
// VAR; then cat "/tmp/$VAR"; fi` — parser would see
// /tmp/__TRACKED_VAR__, bash reads /etc/passwd. Fail closed
// when a tracked literal would be overwritten. Safe case
// (no prior value or already a placeholder) → proceed.
const existing = varScope.get(a)
if (
existing !== undefined &&
!containsAnyPlaceholder(existing)
) {
return {
kind: 'too-complex',
reason: `'read ${a}' in condition may not execute (||/pipeline/subshell); cannot prove it overwrites tracked literal '${existing}'`,
nodeType: 'if_statement',
}
}
varScope.set(a, VAR_PLACEHOLDER)
}
}
}
}
}
}
return null
}
if (node.type === 'subshell') {
// `(cmd1; cmd2)` — run commands in a subshell. Inner commands ARE
// executed, so extract them for permission checking. Subshell has
// isolated scope: vars set inside don't leak out. Use a COPY of
// varScope (outer vars visible, inner changes discarded).
const innerScope = new Map(varScope)
for (const child of node.children) {
if (!child) continue
if (child.type === '(' || child.type === ')') continue
const err = collectCommands(child, commands, innerScope)
if (err) return err
}
return null
}
if (node.type === 'test_command') {
// `[[ EXPR ]]` or `[ EXPR ]` — conditional test. Evaluates to true/false
// based on file tests (-f, -d), string comparisons (==, !=), etc.
// No code execution (no command_substitution inside — that would be a
// child and we'd recurse into it via walkArgument and reject it).
// Push as a synthetic command with argv[0]='[[' so permission rules
// can match — `Bash([[ :*)` would be unusual but legal.
// Walk arguments to validate (no cmdsub/expansion inside operands).
const argv: string[] = ['[[']
for (const child of node.children) {
if (!child) continue
if (child.type === '[[' || child.type === ']]') continue
if (child.type === '[' || child.type === ']') continue
// Recurse into test expression structure: unary_expression,
// binary_expression, parenthesized_expression, negated_expression.
// The leaves are test_operator (-f, -d, ==) and operand words.
const err = walkTestExpr(child, argv, commands, varScope)
if (err) return err
}
commands.push({ argv, envVars: [], redirects: [], text: node.text })
return null
}
if (node.type === 'unset_command') {
// `unset FOO BAR`, `unset -f func`. Safe: only removes shell
// variables/functions from the current shell — no code execution, no
// filesystem I/O. tree-sitter emits a dedicated node type so it
// previously fell through to tooComplex. Children: `unset` keyword,
// `variable_name` for each name, `word` for flags like `-f`/`-v`.
const argv: string[] = []
for (const child of node.children) {
if (!child) continue
switch (child.type) {
case 'unset':
argv.push(child.text)
break
case 'variable_name':
argv.push(child.text)
// SECURITY: unset removes the var from bash's scope. Remove from
// varScope so subsequent `$VAR` references correctly reject.
// `VAR=safe && unset VAR && rm $VAR` must NOT resolve $VAR.
varScope.delete(child.text)
break
case 'word': {
const arg = walkArgument(child, commands, varScope)
if (typeof arg !== 'string') return arg
argv.push(arg)
break
}
default:
return tooComplex(child)
}
}
commands.push({ argv, envVars: [], redirects: [], text: node.text })
return null
}
return tooComplex(node)
}
/**
* Recursively walk a test_command expression tree (unary/binary/negated/
* parenthesized expressions). Leaves are test_operator tokens and operands
* (word/string/number/etc). Operands are validated via walkArgument.
*/
function walkTestExpr(
node: Node,
argv: string[],
innerCommands: SimpleCommand[],
varScope: Map<string, string>,
): ParseForSecurityResult | null {
switch (node.type) {
case 'unary_expression':
case 'binary_expression':
case 'negated_expression':
case 'parenthesized_expression': {
for (const c of node.children) {
if (!c) continue
const err = walkTestExpr(c, argv, innerCommands, varScope)
if (err) return err
}
return null
}
case 'test_operator':
case '!':
case '(':
case ')':
case '&&':
case '||':
case '==':
case '=':
case '!=':
case '<':
case '>':
case '=~':
argv.push(node.text)
return null
case 'regex':
case 'extglob_pattern':
// RHS of =~ or ==/!= in [[ ]]. Pattern text only — no code execution.
// Parser emits these as leaf nodes with no children (any $(...) or ${...}
// inside the pattern is a sibling, not a child, and is walked separately).
argv.push(node.text)
return null