@sema-agent/core/dist/core/read-only-shell.js

Stateless, task-oriented AI agent core

import { posix } from "node:path";
import { readShellCommand } from "./shell-lexer.js";
import { FIND_ACTION_PRIMARIES, FIND_NEWER_PRIMARY, FIND_VALUE_PRIMARIES, FLAG_VALUE_ACCEPTS, READ_ONLY_BARE_ONLY, READ_ONLY_BARE_PROGRAMS, READ_ONLY_COMMAND_TABLE, READ_ONLY_ENV_NAMES, READ_ONLY_EXACT_FORMS, READ_ONLY_GLOB_PROGRAMS, XARGS_READ_ONLY_TARGETS, dockerRetargetDanger, } from "./read-only-shell-table.js";
const NOT = (reason) => ({ readOnly: false, reason });
export const CD_GIT_COMPOUND_SENTENCE = "This command changes directory before running a version-control command, which can pick up untrusted hooks or repository configuration from the target directory. Approve only if you trust it.";
export function changesDirectoryBeforeGit(shape, cwd) {
    const programs = shape.segments.map((s) => peelBuiltinPrefix(s.argv.slice(leadingAssignmentCount(s.argv)).map((w) => w.text))[0] ?? "");
    if (shape.segments.length < 2 || !programs.includes("cd") || !programs.includes("git"))
        return false;
    const cds = shape.segments.filter((_, i) => programs[i] === "cd");
    const [cd] = cds;
    if (cwd === undefined || cds.length !== 1 || cd === undefined || cd.redirections.length > 0 || cd.argv.length !== 2 || cd.argv[0].raw !== "cd")
        return true;
    const target = cd.argv[1];
    if (target.expands !== false || !/^(?:\.\.?(?:\/|$)|\/)/.test(target.text) || /[$`*?[\\]/.test(target.raw))
        return true;
    const trim = (p) => p.replace(/\/+$/, "") || "/";
    return trim(posix.resolve(cwd, target.text)) !== trim(cwd);
}
const READ_ONLY = { readOnly: true };
const BARE_PROGRAMS = new Set(READ_ONLY_BARE_PROGRAMS.filter((p) => !p.includes(" ")));
const BARE_MULTIWORD = READ_ONLY_BARE_PROGRAMS.filter((p) => p.includes(" ")).map((p) => p.split(" "));
const GLOB_PROGRAMS = new Set(READ_ONLY_GLOB_PROGRAMS);
const BARE_ONLY = new Set(READ_ONLY_BARE_ONLY);
const ENV_NAMES = new Set(READ_ONLY_ENV_NAMES);
const FIND_ACTIONS = new Set(FIND_ACTION_PRIMARIES);
const FIND_VALUES = new Set(FIND_VALUE_PRIMARIES);
const XARGS_TARGETS = XARGS_READ_ONLY_TARGETS;
const TABLE_ROWS = Object.entries(READ_ONLY_COMMAND_TABLE)
    .map(([key, row]) => ({ words: key.split(" "), row }))
    .sort((a, b) => b.words.length - a.words.length);
const READING_REDIRECTS = new Set(["<", "<<", "<<-", "<&", "<<<"]);
const LITERAL_ASSIGNMENT = /^([A-Za-z_][A-Za-z0-9_]*)\+?=(?:"[^"$`\\]*"|'[^']*'|[A-Za-z0-9_./:+-]*)$/;
const ASSIGNMENT_NAME = /^([A-Za-z_][A-Za-z0-9_]*)(?:\[[^\]]*\])?\+?=/;
const FLAG_WORD = /^-[a-zA-Z0-9_-]/;
const NUMBER_LITERAL = /^[-+]?(0[xX][0-9a-fA-F]+|[0-9]+#[0-9a-zA-Z]+|[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?)$/;
const PRINTF_LENGTH = "[lLhqjzZt]*";
const PRINTF_ESCAPE = new RegExp(`%[^%a-zA-Z]*${PRINTF_LENGTH}\\\\[0-7xX]`);
const PRINTF_NUMERIC = new RegExp(`%[-+ 0#']*[0-9.*]*${PRINTF_LENGTH}[diouxXeEfFgGaAn]`);
const JQ_DANGER_FLAG = /^['"]?-[a-zA-Z]*[fL]/;
const JQ_DANGER_TEXT = /--from-file|--rawfile|--slurpfile|--run-tests|--library-path|\benv\b|\$ENV\b|\binclude\b|\bimport\b/;
export function readOnlyShellVerdict(command, shape = readShellCommand(command), cwd) {
    const line = lineStructureObjection(shape);
    if (line !== undefined)
        return NOT(line);
    for (const seg of shape.segments) {
        if (seg.unreadable !== undefined)
            return NOT(seg.unreadable);
        if (seg.peelUnreadable !== undefined)
            return NOT(seg.peelUnreadable);
        for (const w of [...seg.argv, ...seg.redirections.map((r) => r.target)]) {
            if (expansionKind(w) === "variable")
                return NOT("a variable, arithmetic or command substitution — its value is not known at approval time");
            if (w.expands !== false && /[()]/.test(w.raw))
                return NOT("a pattern with a parenthesised part (an extended pattern or a shell-specific glob qualifier)");
            if (/^=[A-Za-z_]/.test(w.raw) || w.raw.includes("~["))
                return NOT("a shell-specific expansion spelling (`=cmd`, `~[…]`)");
        }
    }
    if (changesDirectoryBeforeGit(shape, cwd))
        return NOT(CD_GIT_REASON);
    for (const seg of shape.segments) {
        const verdict = segmentVerdict(seg);
        if (!verdict.readOnly)
            return verdict;
    }
    return READ_ONLY;
}
const CD_GIT_REASON = "a compound that changes directory and runs git";
function lineStructureObjection(shape) {
    if (shape.grouped)
        return "a subshell, group or control structure — not a flat list of simple commands";
    if (shape.segments.length === 0)
        return "no command";
    if (shape.backgrounded)
        return "a background `&` defers execution past the approval-time reading";
    if (shape.strayRedirection)
        return "a redirection on a piece that runs no program — the shell still opens its target";
    return undefined;
}
export function readOnlyLineObjection(command, cwd) {
    const shape = readShellCommand(command);
    return lineStructureObjection(shape) ?? (changesDirectoryBeforeGit(shape, cwd) ? CD_GIT_REASON : undefined);
}
function expansionKind(w) {
    if (w.expands === false)
        return "none";
    if (/[$`]|[<>]\(/.test(w.raw))
        return "variable";
    if (w.expands === "many")
        return "glob";
    return "none";
}
function leadingAssignmentCount(argv) {
    let k = 0;
    while (k < argv.length && ASSIGNMENT_NAME.test(argv[k].raw))
        k++;
    return k;
}
function peelBuiltinPrefix(words) {
    let t = words;
    for (;;) {
        if (t[0] === "command") {
            let r = 1;
            while (t[r] !== undefined && /^-p+$/.test(t[r]))
                r++;
            if (t[r] === "--")
                r++;
            if (r >= t.length || t[r].startsWith("-"))
                return t;
            t = t.slice(r);
        }
        else if (t[0] === "builtin") {
            const r = t[1] === "--" ? 2 : 1;
            if (r >= t.length)
                return t;
            t = t.slice(r);
        }
        else if (t[0] === "noglob") {
            if (t.length <= 1)
                return t;
            t = t.slice(1);
        }
        else
            return t;
    }
}
function segmentVerdict(seg) {
    for (const r of seg.redirections) {
        const target = r.target.text;
        if (!READING_REDIRECTS.has(r.op) && target !== "/dev/null" && !(r.op === ">&" && /^\d+$/.test(target)))
            return NOT(`the redirection \`${r.op} ${target}\` writes`);
        if (/^\/dev\/(tcp|udp)\//.test(target))
            return NOT("a redirection to a network pseudo-device");
    }
    const k = leadingAssignmentCount(seg.argv);
    for (const w of seg.argv.slice(0, k)) {
        const m = LITERAL_ASSIGNMENT.exec(w.raw);
        if (m === null)
            return NOT(`the assignment \`${w.raw}\` is not a literal value`);
        if (!ENV_NAMES.has(m[1]))
            return NOT(`the environment variable \`${m[1]}\` can alter what a program does`);
    }
    const run = seg.argv.slice(k);
    if (run.length === 0)
        return NOT("a bare assignment runs no program");
    const words = peelBuiltinPrefix(run.map((w) => w.text));
    const program = words[0];
    if (run.some((w) => expansionKind(w) === "glob"))
        return GLOB_PROGRAMS.has(program) ? READ_ONLY : NOT(`\`${program}\` with a glob argument — the glob may name anything`);
    const structural = structuralReading(words);
    if (structural !== null)
        return structural ? READ_ONLY : NOT(`\`${program}\` with these arguments is not a read-only form`);
    return tableReading(words, run);
}
function structuralReading(words) {
    const program = words[0];
    if (BARE_ONLY.has(program))
        return words.length === 1;
    for (const form of READ_ONLY_EXACT_FORMS)
        if (words.length === form.length && words.every((w, i) => w === form[i]))
            return true;
    if (BARE_PROGRAMS.has(program))
        return true;
    for (const form of BARE_MULTIWORD)
        if (words.length >= form.length && form.every((w, i) => words[i] === w))
            return form[0] !== "docker" || !dockerRetargetDanger(words);
    if (program === "echo")
        return true;
    if (program === "printf")
        return printfReading(words);
    if (program === "ls")
        return true;
    if (program === "cd")
        return words.length <= 2;
    if (program === "find") {
        for (let i = 1; i < words.length; i++) {
            const w = words[i];
            if (FIND_ACTIONS.has(w))
                return false;
            if (FIND_VALUES.has(w) || FIND_NEWER_PRIMARY.test(w)) {
                i++;
                continue;
            }
        }
        return true;
    }
    if (program === "history")
        return words.length === 1 || (words.length === 2 && /^\d+$/.test(words[1]));
    if (program === "arch")
        return words.length === 1 || (words.length === 2 && (words[1] === "-h" || words[1] === "--help"));
    if (program === "ifconfig")
        return words.length === 1 || (words.length === 2 && /^[a-zA-Z]/.test(words[1]));
    return null;
}
function printfReading(words) {
    if (words[1]?.startsWith("-") === true && words[1] !== "--")
        return false;
    const at = words[1] === "--" ? 2 : 1;
    const format = words[at] ?? "";
    if (format.includes("$"))
        return false;
    const stripped = format.replace(/%%/g, "");
    if (PRINTF_ESCAPE.test(stripped) || /\\[uU]/.test(stripped))
        return false;
    if (PRINTF_NUMERIC.test(stripped) || /%[^%a-zA-Z]*\*/.test(stripped)) {
        for (let i = at + 1; i < words.length; i++) {
            const operand = words[i];
            if (operand.includes("[") || operand.includes("`") || operand.includes("$(") || !NUMBER_LITERAL.test(operand))
                return false;
        }
    }
    return true;
}
function tableReading(words, run) {
    const program = words[0];
    const hit = TABLE_ROWS.find((r) => words.length >= r.words.length && r.words.every((w, i) => words[i] === w));
    if (hit !== undefined) {
        const args = words.slice(hit.words.length);
        for (const a of args) {
            if (a.includes("$"))
                return NOT(`\`${program}\`: an argument spells \`$\``);
            if (a.includes("{") && (a.includes(",") || a.includes("..")))
                return NOT(`\`${program}\`: a brace pattern argument`);
        }
        if (!flagWalk(args, hit.row, program))
            return NOT(`\`${program}\`: an option outside its read-only set (or a malformed option value)`);
        if (hit.row.wordsShape !== undefined ? !hit.row.wordsShape(args) : run.some((w) => w.raw.includes("`")))
            return NOT(`\`${program}\`: arguments outside its read-only form`);
        if (hit.row.wordsShape === undefined && (program === "rg" || program === "grep" || program === "egrep" || program === "fgrep") && run.some((w) => /[\n\r]/.test(w.raw)))
            return NOT(`\`${program}\`: a line break inside an argument`);
        if (hit.row.dangerous?.(args) === true)
            return NOT(`\`${program}\`: an argument form upstream marks as writing, executing or resolving`);
        return READ_ONLY;
    }
    if (program === "uniq" && words.slice(1).every((w, i, all) => /^-[a-zA-Z]+$/.test(w) || /^--[a-zA-Z-]+(=\S+)?$/.test(w) || (i > 0 && /^-[fsw]$/.test(all[i - 1]) && /^\d+$/.test(w))))
        return gitOptionGuard(words);
    if (program === "jq" && jqReading(run.slice(run.length - words.length + 1)))
        return gitOptionGuard(words);
    return NOT(`\`${program}\` is not a read-only program (or not in a read-only form)`);
}
function gitOptionGuard(words) {
    if (words.includes("git") && words.some((w) => /^-c(=|$)|^--exec-path(=|$)|^--config-env(=|$)/.test(w)))
        return NOT("a git configuration override on the line");
    return READ_ONLY;
}
function jqReading(args) {
    if (args.some((w) => JQ_DANGER_FLAG.test(w.raw) || JQ_DANGER_TEXT.test(w.raw)))
        return false;
    let i = 0;
    while (i < args.length && (/^-[a-zA-Z]+$/.test(args[i].raw) || /^--[a-zA-Z-]+(=\S+)?$/.test(args[i].raw)))
        i++;
    if (i >= args.length)
        return false;
    for (; i < args.length; i++) {
        const w = args[i];
        const quoted = /^'[^'`]*'$|^"[^"`]*"$/.test(w.raw);
        if (!quoted && (/^[-'"\s]/.test(w.raw) || /['"]/.test(w.raw)))
            return false;
    }
    return true;
}
function flagWalk(args, row, program) {
    let i = 0;
    while (i < args.length) {
        let word = args[i];
        if (word === "") {
            i++;
            continue;
        }
        if (program === "xargs" && (!word.startsWith("-") || word === "--")) {
            if (word === "--" && i + 1 < args.length) {
                i++;
                word = args[i];
            }
            return XARGS_TARGETS.includes(word);
        }
        if (word === "--") {
            if (row.respectsDoubleDash !== false)
                break;
            i++;
            continue;
        }
        if (FLAG_WORD.test(word)) {
            const eq = word.indexOf("=");
            const flag = eq === -1 ? word : word.slice(0, eq);
            const attached = eq === -1 ? undefined : word.slice(eq + 1);
            const arity = row.safeFlags[flag];
            if (arity === undefined) {
                if (program === "git" && /^-\d+$/.test(flag)) {
                    i++;
                    continue;
                }
                if ((program === "grep" || program === "egrep" || program === "fgrep" || program === "rg") && !flag.startsWith("--") && flag.length > 2) {
                    const base = flag.slice(0, 2);
                    const rest = flag.slice(2);
                    const baseArity = row.safeFlags[base];
                    if (baseArity !== undefined && /^\d+$/.test(rest) && (baseArity === "number" || baseArity === "string")) {
                        if (FLAG_VALUE_ACCEPTS[baseArity](rest)) {
                            i++;
                            continue;
                        }
                        return false;
                    }
                }
                if (!flag.startsWith("--") && flag.length > 2) {
                    for (let c = 1; c < flag.length; c++)
                        if (row.safeFlags[`-${flag[c]}`] !== "none")
                            return false;
                    i++;
                    continue;
                }
                return false;
            }
            if (arity === "none") {
                if (attached !== undefined)
                    return false;
                i++;
                continue;
            }
            let value;
            if (attached !== undefined) {
                value = attached;
                i++;
            }
            else {
                const next = args[i + 1];
                if (next === undefined || FLAG_WORD.test(next))
                    return false;
                value = next;
                i += 2;
            }
            if (arity === "string" && value.startsWith("-") && !(flag === "--sort" && program === "git" && /^-[a-zA-Z]/.test(value)))
                return false;
            if (!FLAG_VALUE_ACCEPTS[arity](value))
                return false;
            continue;
        }
        i++;
    }
    return true;
}