kill-guard

1import type { Register } from 'claude-code'
2
3const MOD = 'kill-guard'
4
5const WAY_OUT =
6  'Kill the PID you saved (`$!` or a pid file), or check the PID\'s working directory is inside this worktree ' +
7  '(`lsof -a -p <pid> -d cwd` or `ps -o command= -p <pid>`) and kill that PID.'
8
9const DENY_TEXT = `${MOD}: a kill by name or port can stop another checkout's process. ${WAY_OUT}`
10
11const FINDERS = new Set(['lsof', 'pgrep', 'pidof', 'ps', 'ss', 'netstat', 'fuser'])
12const KILL_BY_NAME = new Set(['pkill', 'killall'])
13const PREFIX = new Set(['!', 'if', 'then', 'do', 'else', 'elif', 'while', 'until', '{', 'time', 'exec', 'command', 'builtin', 'nohup', 'sudo', 'doas', 'env', 'nice'])
14const XARGS_WITH_ARG = new Set(['-I', '-n', '-P', '-L', '-d', '-E', '-s', '-a'])
15
16type Frame = { parent?: Seg; segs: Seg[] }
17type Seg = { text: string; piped: boolean; frame: Frame; words?: string[]; via?: string }
18
19function scan(input: string): Frame[] {
20  const frames: Frame[] = []
21  const open = (parent?: Seg): Frame => {
22    const frame: Frame = { parent, segs: [] }
23    frames.push(frame)
24    return frame
25  }
26  const stack: { frame: Frame; kind: 'top' | 'sub' | 'grp' | 'bt' | 'dq' | 'sq' }[] = [{ frame: open(), kind: 'top' }]
27  const begin = (frame: Frame, piped: boolean) => frame.segs.push({ text: '', piped, frame })
28  const cur = () => {
29    const frame = stack[stack.length - 1].frame
30    if (!frame.segs.length) begin(frame, false)
31    return frame.segs[frame.segs.length - 1]
32  }
33  const split = (piped: boolean) => begin(stack[stack.length - 1].frame, piped)
34  const enter = (kind: 'sub' | 'grp' | 'bt') => {
35    const parent = kind === 'grp' ? undefined : cur()
36    const frame = kind === 'grp' ? stack[stack.length - 1].frame : open(parent)
37    stack.push({ frame, kind })
38    split(false)
39  }
40
41  for (let i = 0; i < input.length; i++) {
42    const c = input[i]
43    const top = stack[stack.length - 1].kind
44    const next = input[i + 1]
45    if (top === 'sq') {
46      if (c === "'") stack.pop()
47      cur().text += '_'
48    } else if (top === 'dq') {
49      if (c === '\\') {
50        cur().text += '__'
51        i++
52      } else if (c === '"') {
53        stack.pop()
54        cur().text += '_'
55      } else if (c === '$' && next === '(') {
56        enter('sub')
57        i++
58      } else if (c === '`') {
59        enter('bt')
60      } else cur().text += '_'
61    } else if (c === '\\') {
62      cur().text += next === '\n' ? ' ' : '__'
63      i++
64    } else if (c === "'") {
65      stack.push({ frame: stack[stack.length - 1].frame, kind: 'sq' })
66      cur().text += '_'
67    } else if (c === '"') {
68      stack.push({ frame: stack[stack.length - 1].frame, kind: 'dq' })
69      cur().text += '_'
70    } else if (c === '#' && (i === 0 || /\s/.test(input[i - 1]))) {
71      while (i + 1 < input.length && input[i + 1] !== '\n') i++
72    } else if (c === '$' && next === '(') {
73      enter('sub')
74      i++
75    } else if (c === '`') {
76      if (top === 'bt') {
77        stack.pop()
78        cur()
79      } else enter('bt')
80    } else if (c === '(') {
81      enter('grp')
82    } else if (c === ')') {
83      if (top === 'sub' || top === 'grp') stack.pop()
84      split(false)
85    } else if (c === '|' && next === '|') {
86      split(false)
87      i++
88    } else if (c === '|') {
89      split(true)
90    } else if (c === '&' && next === '&') {
91      split(false)
92      i++
93    } else if (c === '&' && input[i - 1] === '>') {
94      cur().text += c
95    } else if (c === ';' || c === '&' || c === '\n') {
96      split(false)
97    } else {
98      cur().text += c
99    }
100  }
101  return frames
102}
103
104function command(seg: Seg): string | undefined {
105  const words = seg.text.split(/\s+/).filter(Boolean)
106  let i = 0
107  while (i < words.length) {
108    const w = words[i]
109    const base = w.replace(/^.*\//, '')
110    if (/^[A-Za-z_]\w*=/.test(w) || PREFIX.has(base)) {
111      i++
112      if (base === 'sudo' || base === 'doas') while (words[i]?.startsWith('-')) i += /^-[ughCT]$/.test(words[i]) ? 2 : 1
113    } else if (base === 'xargs') {
114      seg.via = 'xargs'
115      i++
116      while (words[i]?.startsWith('-')) i += XARGS_WITH_ARG.has(words[i]) ? 2 : 1
117    } else break
118  }
119  seg.words = words.slice(i)
120  return seg.words[0]?.replace(/^.*\//, '')
121}
122
123function judge(input: string): boolean {
124  const frames = scan(input)
125  for (const frame of frames) {
126    let pipeline: Seg[] = []
127    for (const seg of frame.segs) {
128      pipeline = seg.piped ? [...pipeline, seg] : [seg]
129      const name = command(seg)
130      if (!name) continue
131      if (KILL_BY_NAME.has(name)) return true
132      if (name === 'fuser' && seg.words!.slice(1).some(w => /^-[A-Za-z]*k/.test(w))) return true
133      if (name === 'kill' && seg.via === 'xargs' && pipeline.slice(0, -1).some(p => FINDERS.has(command(p) ?? ''))) return true
134    }
135    const parent = frame.parent && command(frame.parent)
136    if (parent === 'kill' && frame.segs.some(s => FINDERS.has(command(s) ?? ''))) return true
137  }
138  return false
139}
140
141export const register: Register = on => {
142  on('tool.call', { tool: 'Bash' }, async ($, e, next) => {
143    return judge(e.command) ? { deny: DENY_TEXT } : next(e)
144  }).catch(($, e, next) =>
145    next.called ? next(e) : { deny: `${MOD}: could not check this command (${next.error.message}). ${WAY_OUT}` },
146  )
147}
148