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进程沙箱
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dsh-sandbox 的进程沙箱 seam 将同世界子进程的 argv 包装在文件效果策略中，而不将消费方耦合到特定平台运行器。dsh-sandbox-local 提供 Linux bwrap/Landlock 与 macOS Seatbelt 后端；dsh-bash-sandbox 是第一个消费方。容器、microVM 和远程执行是完整能力 seam 的兄弟实现，而非 ctx.sandbox 的提供方。
源码：packages/sandbox/sandbox/src/index.ts
模式与强制执行
SandboxMode 仅管控文件系统效果。read-only 拒绝所有写入（必需的 /dev/null 接收器除外）；workspace-write 允许在工作区根目录及后端承诺的临时区域下写入；danger-full-access 绕过隔离。网络与进程可见性不在此处的定义范围内。
/**
* File-effect policy for confined processes. `read-only` permits only required
* sinks such as `/dev/null`; `workspace-write` also permits the workspace and a
* backend-defined temp area; `danger-full-access` bypasses confinement. Network
* and process visibility are outside this vocabulary.
*/
type SandboxMode = 'read-only' | 'workspace-write' | 'danger-full-access'
只有前两种模式可以发送给提供方。danger-full-access 的消费方直接 spawn 原始 argv，不调用 ctx.sandbox。
/** A confining (non-`danger-full-access`) mode — the modes a {@link SandboxPolicy} can carry. */
type ConfinedSandboxMode = Exclude<SandboxMode, 'danger-full-access'>
强制执行程度是一个报告事实。full 表示后端管控了该模式承诺的所有文件效果；partial 表示活跃后端或较旧的内核 ABI 仅管控其中一个子集，因此要求绝对保证的消费方必须拒绝或向上暴露这一区别。
/**
* Enforcement completeness for this host. `partial` means an active backend or
* older kernel ABI cannot govern every promised file effect; callers requiring
* an absolute boundary must not treat it as `full`.
*/
type SandboxEnforcement = 'full' | 'partial'
逐调用策略
完整执行策略会按每次能力调用解析并携带。它包括 danger-full-access，因此消费方可以只解析一次策略，再决定是否绕过约束。普通工具调用从调用会话的不可变 cwd 派生 workspaceRoot；部署配置是没有 agent（智能体）时的回退值。root 会先按文件系统语义规范化，再做词法规范化，因此包含 symlink/.. 的 cwd 会标识所生成进程实际运行的目录。
/**
* The complete file-effect policy resolved for one capability call. The root
* is carried even under modes that do not consume it so callers can resolve
* policy once before choosing the enforcement path.
*/
interface SandboxExecutionPolicy {
/** The file-effect mode this execution runs under. */
mode: SandboxMode
/** Absolute root directory `workspace-write` may write under. */
workspaceRoot: string
}
ctx.sandboxPolicy.resolve() 接收活跃会话；对于已批准的重试，还接收显式模式。该服务拥有优先级与 root 回退规则，使 bash 和 fs 不必重复实现。
/** Inputs that select the sandbox policy for one capability call. */
interface SandboxPolicyRequest {
/** Calling session; its immutable cwd becomes the workspace boundary. */
session?: Session
/** Explicit approved mode override, which outranks session policy. */
mode?: SandboxMode
}
只有受约束的执行会到达 ctx.sandbox；其提供方策略在保留同一 root 的同时收窄模式。这使并发会话、消费方与一次性提权重试可以向同一提供方请求不同边界，而无需改变提供方状态。
/**
* What one confined execution is allowed to touch — carried PER CALL, not
* fixed on the provider: two consumers may confine under different policies
* at the same instant (bash under `read-only` while a confined child agent
* needs its state directory writable), and an approved escalated retry is a
* new call with a wider policy. Defaulting/resolution is an explicit step at
* the consumer boundary; the provider treats the policy as fully specified.
*/
interface SandboxPolicy extends SandboxExecutionPolicy {
/** The file-effect mode this execution runs under. */
mode: ConfinedSandboxMode
}
包装后的 argv 与分类方言
ConfinedArgv 是消费方实际 spawn 的内容。除了替换后的 argv，它还携带后端的强制执行事实和两种正交的 stderr 方言。denialSignatures 用于识别沙箱正常工作时被隔离命令被阻止的情况。runnerFailureSignatures 用于识别沙箱运行器在执行命令之前拒绝或失败的情况；消费方应先检查后者，将其作为沙箱基础设施故障上报，而非普通任务失败。
/**
* A {@link SandboxProvider.confine} result: the argv to spawn in place of
* the caller's own, plus the enforcement completeness the selected backend
* achieves for it.
*/
interface ConfinedArgv {
/** The wrapped argv (runner, profile, separator, then the caller's argv). */
argv: string[]
/** How completely the selected backend enforces the policy's file effects. */
enforcement: SandboxEnforcement
/**
* The selected backend's denial DIALECT: the case-insensitive stderr
* substrings a file effect denied by THIS backend produces (EROFS text
* under bwrap's read-only binds, EACCES under Landlock, EPERM under
* Seatbelt). A consumer that infers denials from a failed run's stderr
* matches against exactly these rather than a cross-backend union — the
* union claims denials a given backend never produces.
*/
denialSignatures: readonly string[]
/**
* Case-insensitive signatures for runner failure before command execution.
* Consumers check these before denial signatures: runner failure means the
* command never ran, while denial means confinement worked and blocked it.
*/
runnerFailureSignatures: readonly string[]
}
运维人员配置的本地运行器必须为自身的 pre-exec 拒绝方言提供至少一条 runnerFailureSignatures 条目；提供方会自动添加外层 shell 的 missing 和 unexecutable 形式。这使得可执行的自定义运行器拒绝其 profile 的情况能够与被包装命令以相同状态码退出的情况区分开来。
提供方与 fail-closed 错误
ctx.sandbox.confine(argv, policy) 返回一个 ConfinedArgv，或在没有可用后端时抛出 SandboxUnavailableError（错误码 SANDBOX_UNAVAILABLE）。已选定的运行器也可能在执行时 fail-closed，此时其失败签名承载相同的基础设施含义。对于受限策略，静默的无隔离透传永远不合法。
提供方探测在多个候选后端之间仲裁，结果在提供方生命周期内缓存。只有一个候选后端的平台可以直接选定它；执行时拒绝仍保留安全属性。本地提供方将 bwrap 和 Seatbelt 报告为 full，并保留 Landlock 启动器的 full/partial 内核裁定。