fix: execute sandboxed file ops inside containers (#4026)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: 795ec6aa2f
Co-authored-by: davidbors-snyk <240482518+davidbors-snyk@users.noreply.github.com>
Co-authored-by: steipete <58493+steipete@users.noreply.github.com>
Reviewed-by: @steipete

src/agents/sandbox/fs-bridge.ts

@@ -0,0 +1,257 @@
+import path from "node:path";
+import type { SandboxContext, SandboxWorkspaceAccess } from "./types.js";
+import { resolveSandboxPath } from "../sandbox-paths.js";
+import { execDockerRaw, type ExecDockerRawResult } from "./docker.js";
+
+type RunCommandOptions = {
+  args?: string[];
+  stdin?: Buffer | string;
+  allowFailure?: boolean;
+  signal?: AbortSignal;
+};
+
+export type SandboxResolvedPath = {
+  hostPath: string;
+  relativePath: string;
+  containerPath: string;
+};
+
+export type SandboxFsStat = {
+  type: "file" | "directory" | "other";
+  size: number;
+  mtimeMs: number;
+};
+
+export type SandboxFsBridge = {
+  resolvePath(params: { filePath: string; cwd?: string }): SandboxResolvedPath;
+  readFile(params: { filePath: string; cwd?: string; signal?: AbortSignal }): Promise<Buffer>;
+  writeFile(params: {
+    filePath: string;
+    cwd?: string;
+    data: Buffer | string;
+    encoding?: BufferEncoding;
+    mkdir?: boolean;
+    signal?: AbortSignal;
+  }): Promise<void>;
+  mkdirp(params: { filePath: string; cwd?: string; signal?: AbortSignal }): Promise<void>;
+  remove(params: {
+    filePath: string;
+    cwd?: string;
+    recursive?: boolean;
+    force?: boolean;
+    signal?: AbortSignal;
+  }): Promise<void>;
+  rename(params: { from: string; to: string; cwd?: string; signal?: AbortSignal }): Promise<void>;
+  stat(params: {
+    filePath: string;
+    cwd?: string;
+    signal?: AbortSignal;
+  }): Promise<SandboxFsStat | null>;
+};
+
+export function createSandboxFsBridge(params: { sandbox: SandboxContext }): SandboxFsBridge {
+  return new SandboxFsBridgeImpl(params.sandbox);
+}
+
+class SandboxFsBridgeImpl implements SandboxFsBridge {
+  private readonly sandbox: SandboxContext;
+
+  constructor(sandbox: SandboxContext) {
+    this.sandbox = sandbox;
+  }
+
+  resolvePath(params: { filePath: string; cwd?: string }): SandboxResolvedPath {
+    return resolveSandboxFsPath({
+      sandbox: this.sandbox,
+      filePath: params.filePath,
+      cwd: params.cwd,
+    });
+  }
+
+  async readFile(params: {
+    filePath: string;
+    cwd?: string;
+    signal?: AbortSignal;
+  }): Promise<Buffer> {
+    const target = this.resolvePath(params);
+    const result = await this.runCommand('set -eu; cat -- "$1"', {
+      args: [target.containerPath],
+      signal: params.signal,
+    });
+    return result.stdout;
+  }
+
+  async writeFile(params: {
+    filePath: string;
+    cwd?: string;
+    data: Buffer | string;
+    encoding?: BufferEncoding;
+    mkdir?: boolean;
+    signal?: AbortSignal;
+  }): Promise<void> {
+    this.ensureWriteAccess("write files");
+    const target = this.resolvePath(params);
+    const buffer = Buffer.isBuffer(params.data)
+      ? params.data
+      : Buffer.from(params.data, params.encoding ?? "utf8");
+    const script =
+      params.mkdir === false
+        ? 'set -eu; cat >"$1"'
+        : 'set -eu; dir=$(dirname -- "$1"); if [ "$dir" != "." ]; then mkdir -p -- "$dir"; fi; cat >"$1"';
+    await this.runCommand(script, {
+      args: [target.containerPath],
+      stdin: buffer,
+      signal: params.signal,
+    });
+  }
+
+  async mkdirp(params: { filePath: string; cwd?: string; signal?: AbortSignal }): Promise<void> {
+    this.ensureWriteAccess("create directories");
+    const target = this.resolvePath(params);
+    await this.runCommand('set -eu; mkdir -p -- "$1"', {
+      args: [target.containerPath],
+      signal: params.signal,
+    });
+  }
+
+  async remove(params: {
+    filePath: string;
+    cwd?: string;
+    recursive?: boolean;
+    force?: boolean;
+    signal?: AbortSignal;
+  }): Promise<void> {
+    this.ensureWriteAccess("remove files");
+    const target = this.resolvePath(params);
+    const flags = [params.force === false ? "" : "-f", params.recursive ? "-r" : ""].filter(
+      Boolean,
+    );
+    const rmCommand = flags.length > 0 ? `rm ${flags.join(" ")}` : "rm";
+    await this.runCommand(`set -eu; ${rmCommand} -- "$1"`, {
+      args: [target.containerPath],
+      signal: params.signal,
+    });
+  }
+
+  async rename(params: {
+    from: string;
+    to: string;
+    cwd?: string;
+    signal?: AbortSignal;
+  }): Promise<void> {
+    this.ensureWriteAccess("rename files");
+    const from = this.resolvePath({ filePath: params.from, cwd: params.cwd });
+    const to = this.resolvePath({ filePath: params.to, cwd: params.cwd });
+    await this.runCommand(
+      'set -eu; dir=$(dirname -- "$2"); if [ "$dir" != "." ]; then mkdir -p -- "$dir"; fi; mv -- "$1" "$2"',
+      {
+        args: [from.containerPath, to.containerPath],
+        signal: params.signal,
+      },
+    );
+  }
+
+  async stat(params: {
+    filePath: string;
+    cwd?: string;
+    signal?: AbortSignal;
+  }): Promise<SandboxFsStat | null> {
+    const target = this.resolvePath(params);
+    const result = await this.runCommand('set -eu; stat -c "%F|%s|%Y" -- "$1"', {
+      args: [target.containerPath],
+      signal: params.signal,
+      allowFailure: true,
+    });
+    if (result.code !== 0) {
+      const stderr = result.stderr.toString("utf8");
+      if (stderr.includes("No such file or directory")) {
+        return null;
+      }
+      const message = stderr.trim() || `stat failed with code ${result.code}`;
+      throw new Error(`stat failed for ${target.containerPath}: ${message}`);
+    }
+    const text = result.stdout.toString("utf8").trim();
+    const [typeRaw, sizeRaw, mtimeRaw] = text.split("|");
+    const size = Number.parseInt(sizeRaw ?? "0", 10);
+    const mtime = Number.parseInt(mtimeRaw ?? "0", 10) * 1000;
+    return {
+      type: coerceStatType(typeRaw),
+      size: Number.isFinite(size) ? size : 0,
+      mtimeMs: Number.isFinite(mtime) ? mtime : 0,
+    };
+  }
+
+  private async runCommand(
+    script: string,
+    options: RunCommandOptions = {},
+  ): Promise<ExecDockerRawResult> {
+    const dockerArgs = [
+      "exec",
+      "-i",
+      this.sandbox.containerName,
+      "sh",
+      "-c",
+      script,
+      "moltbot-sandbox-fs",
+    ];
+    if (options.args?.length) {
+      dockerArgs.push(...options.args);
+    }
+    return execDockerRaw(dockerArgs, {
+      input: options.stdin,
+      allowFailure: options.allowFailure,
+      signal: options.signal,
+    });
+  }
+
+  private ensureWriteAccess(action: string) {
+    if (!allowsWrites(this.sandbox.workspaceAccess)) {
+      throw new Error(
+        `Sandbox workspace (${this.sandbox.workspaceAccess}) does not allow ${action}.`,
+      );
+    }
+  }
+}
+
+function allowsWrites(access: SandboxWorkspaceAccess): boolean {
+  return access === "rw";
+}
+
+function resolveSandboxFsPath(params: {
+  sandbox: SandboxContext;
+  filePath: string;
+  cwd?: string;
+}): SandboxResolvedPath {
+  const root = params.sandbox.workspaceDir;
+  const cwd = params.cwd ?? root;
+  const { resolved, relative } = resolveSandboxPath({
+    filePath: params.filePath,
+    cwd,
+    root,
+  });
+  const normalizedRelative = relative
+    ? relative.split(path.sep).filter(Boolean).join(path.posix.sep)
+    : "";
+  const containerPath = normalizedRelative
+    ? path.posix.join(params.sandbox.containerWorkdir, normalizedRelative)
+    : params.sandbox.containerWorkdir;
+  return {
+    hostPath: resolved,
+    relativePath: normalizedRelative,
+    containerPath,
+  };
+}
+
+function coerceStatType(typeRaw?: string): "file" | "directory" | "other" {
+  if (!typeRaw) {
+    return "other";
+  }
+  const normalized = typeRaw.trim().toLowerCase();
+  if (normalized.includes("directory")) {
+    return "directory";
+  }
+  if (normalized.includes("file")) {
+    return "file";
+  }
+  return "other";
+}