fix(eval): refuse Docker DNS after pinning the egress proxy host - #3009
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Thanks for working through the Docker DNS behavior. The address-level rejection is the right fix: Docker rewrites port 53 before the filter hook, so rejecting 127.0.0.11 ahead of the generic local-address allowance is the smallest rule that closes this path without breaking the other loopback services.
I found two lifecycle cases worth addressing, noted inline:
- A
deny-allbaseline disables Docker DNS before the sidecar has populated its proxy-IP cache, so the first laterallowcannot resolve the proxy. _pin_proxy_hostnameinherits the task's default agent user, so a supported non-rootagent.usercannot update/etc/hosts.
Both have small fixes at their natural owners. The proxy's published proxy-ipv4 file can be the single address source for the sidecar and relay, which lets the sidecar cache and DNS fallback be deleted. The /etc/hosts update can run explicitly as root without changing the Agent's identity for any other command.
It would also help to make the namespace test prove that 127.0.0.11 is reachable before policy application. Otherwise the new negative assertion can pass on a host where the Docker resolver was unavailable to begin with.
I would keep this as one PR. Publishing the address, pinning the hostname, and rejecting Docker DNS are one lifecycle and are not independently useful.
I used Codex reviewers and Claude to inspect the Harbor lifecycle and then independently checked the current head, the real default-user propagation, the policy ordering, and CI state.
中文审查结论
感谢处理 Docker DNS 的实际行为。按地址拒绝是正确方向：Docker 会在 filter hook 前改写 53 端口，因此在通用 local-address allowance 之前拒绝 127.0.0.11，是既关闭这条路径、又不破坏其他 loopback 服务的最小规则。
目前还有两个需要处理的生命周期问题，已分别写在行内：
- baseline 为
deny-all时，Docker DNS 会在 sidecar 写入代理 IP 缓存前被关闭；之后第一次allow无法再解析代理。 _pin_proxy_hostname会继承 task 的默认 agent user；合法的非 rootagent.user无权更新/etc/hosts。
两者都可以在自然 owner 处做小幅修正。让代理发布的 proxy-ipv4 文件成为 sidecar 和 relay 的唯一地址来源，就可以删除 sidecar 的缓存和 DNS fallback。修改 /etc/hosts 的单次基础设施操作则可以显式以 root 执行，不影响 Agent 其他命令的身份。
namespace test 还应先证明策略生效前 127.0.0.11 确实可达。否则在本来就没有 Docker resolver 的宿主上，新增的否定断言也可能通过。
这个 PR 不需要拆分。发布地址、pin hostname 和拒绝 Docker DNS 属于同一个生命周期，任何一部分单独存在都不完整。
本次使用 Codex reviewers 与 Claude 辅助检查 Harbor 生命周期；随后独立核对了当前 head、默认用户传播、策略顺序和 CI 状态。
Publish the proxy IPv4 into the certificate volume and pin maka-eval-mitmproxy in /etc/hosts before the subject starts. The namespace policy then rejects 127.0.0.11:53 so the local exemption no longer forwards names to the host resolver. Fixes apache#2976
Docker DNATs 127.0.0.11:53 onto another local port before the filter hook. Matching only dport 53 missed, and the local exemption then accepted the rewritten packet. Reject the resolver address instead. Fixes apache#2976
deny-all already closes Docker DNS, so the sidecar cannot getent the proxy on the first later allow. Read /opt/maka-egress/proxy-ipv4 from the certificate volume instead. Pin the hostname as root so a supported non-root agent.user can still start.
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Addressed in 5340bef, rebased onto current
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Harbor scopes exec to the task agent.user. The /etc/hosts pin is infrastructure, so the contract must keep it as root when that default is a supported non-root identity.
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📝 WalkthroughSummary
Source of truth and solution scopeThe PR extends the existing egress-proxy and namespace-policy path. It does not create a parallel egress-control system. The certificate volume carries the proxy metadata. The existing relay and nftables policy consume it. Host pinning removes the post-policy DNS dependency. The This is the smallest coherent solution evident in the diff. The metadata file, root-only hosts update, strict validation, and DNS probe are required to close the identified bypass without breaking proxy access or weakening regression coverage. Simplification opportunitiesNo safe deletion is evident. The health check, lifecycle assertions, namespace probe, and relay contract tests cover distinct failure modes. User propagation is required to verify root-only pinning with non-root defaults. Validation and risks
Review-relevant risksThe diff changes security-sensitive egress filtering. It rejects traffic to The diff changes The diff adds optional The person performing the merge must review the final diff. A maintainer makes the final determination. WalkthroughThe egress proxy publishes its IPv4 address through the shared CA volume. The relay pins the proxy hostname before policy enforcement. The network policy blocks Docker’s embedded DNS resolver. Tests verify address publication, hostname pinning, execution users, and DNS isolation. ChangesEgress isolation
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🔵 Low · up to The PR blocks Docker DNS as an unaudited egress path and relies on a pinned proxy address for continued hostname resolution. Malformed address metadata can still be accepted as pinned, leaving the proxy unreachable once DNS is blocked; this is a bounded correctness risk requiring owner follow-up, along with a minor test-lint fix. Sequence Diagram(s)sequenceDiagram
participant EgressProxy
participant SharedVolume
participant RelayAgent
participant Subject
participant NetworkPolicy
EgressProxy->>SharedVolume: publish proxy-ipv4
RelayAgent->>SharedVolume: read proxy-ipv4
RelayAgent->>Subject: pin proxy hostname in /etc/hosts
RelayAgent->>NetworkPolicy: apply egress policy
NetworkPolicy-->>Subject: reject Docker DNS traffic
Subject->>EgressProxy: send proxy traffic
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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Inline comments:
In `@packages/eval/harbor/relay_agent.py`:
- Around line 369-389: Strengthen hostname validation in the proxy-host setup
before modifying /etc/hosts: accept only a valid single DNS hostname without
whitespace, newlines, regex metacharacters, slashes, NULs, or dot-only values.
Update the /etc/hosts filtering in the generated script to compare aliases as
exact fields rather than interpolating host into a grep regular expression,
while preserving the new mapping output and existing cleanup behavior.
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packages/eval/README.mdpackages/eval/harbor/docker-compose-egress-proxy.yamlpackages/eval/harbor/egress-proxy/entrypoint.shpackages/eval/harbor/egress-proxy/network-policypackages/eval/harbor/relay_agent.pypackages/eval/harbor/test_cell_egress_namespace.pypackages/eval/harbor/test_relay_contract.pypackages/eval/src/__tests__/lifecycle-boundaries.test.ts
Reject regex metacharacters and whitespace, and drop existing hosts aliases by exact field match so an invalid host cannot wipe /etc/hosts.
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packages/eval/harbor/relay_agent.py (1)
398-417: 🎯 Functional Correctness | 🟠 Major | ⚡ Quick winValidate all IPv4 octets before writing
/etc/hosts.Lines 399-401 accept
999.1.1.1,1..2.3, and.... Line 417 also accepts these values. The script then writes the invalid mapping and reports success. After the policy rejects127.0.0.11, the proxy hostname cannot resolve and egress fails.Validate exactly four decimal octets in the range
0through255. Apply the same validation inpackages/eval/harbor/egress-proxy/network-policy, which consumes the same file.Proposed validation
case "$ip" in ""|*.*.*.*.*|*[!0-9.]*) exit 1 ;; esac +if ! printf '%s\n' "$ip" | awk -F. ' + NF != 4 { exit 1 } + { + for (i = 1; i <= 4; i++) { + if ($i !~ /^[0-9]+$/ || $i > 255) exit 1 + } + } +'; then + exit 1 +fipackages/eval/harbor/test_relay_contract.py (1)
463-468: 🎯 Functional Correctness | 🟡 Minor | ⚡ Quick winKeep command and user tracking consistent in the fake.
MissingAddressEnvironment.execrecords the proxy command without recording its effective user. For non-proxy commands, it records the command before delegating toSubjectEnvironment.exec, which records it again. This can makecommandsandusersdisagree and can duplicate evidence.Record both fields only in the simulated-failure branch, or let one method own all tracking.
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packages/eval/harbor/test_relay_contract.py (2)
475-485: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick winDelete the redundant root-only test.
test_proxy_hostname_pin_does_not_inherit_a_non_root_default_useralready verifies that pinning uses"root"under the stricter non-root default. It also verifies the probe user.test_proxy_hostname_pin_runs_as_rootadds no distinct observable coverage.As per path instructions, flag tests that duplicate existing coverage and keep the smallest coherent solution.
Source: Path instructions
523-525: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick winRemove assertions about the chosen command implementation.
The input/output assertion below tests the observable filtering behavior. These checks require the exact
awkandgrepconstruction and can reject an equivalent safe implementation without detecting a behavioral regression. Delete them.As per path instructions, flag tests that assert implementation details instead of observable behavior.
Source: Path instructions
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Thanks for working through the Docker DNS channel — the address-level rejection is the right layer, and the proxy-ipv4 file + hostname pin is a coherent design. The review found one P1 worth resolving before merge. Conclusion: needs work — one P1 (signature verification) plus related P2s. P1 — P2-1 — the core behavior (refusing 127.0.0.11) has no CI-visible behavioral test. The DNS probe in P2-2 — weak IPv4 validation can fail open. The shell and Python checks accept values like Optional nits (P3): validation is split across shell and Python with already-divergent rules (the shell check writes AI-assisted review disclosure: this review was produced with AI assistance (pi review subagents on 中文摘要（AI 辅助审查）结论：FAIL，需先验证一个关键点。P1：relay_agent.py:412 的 |
Reject 999.1.1.1 and other malformed published addresses in both the relay pin and the sidecar policy. Contract tests now use the Harbor 0.20.0 exec(user=) signature instead of **kwargs, cover proxy* and later hosts aliases, and lock that 127.0.0.11 is rejected before the local accept.
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Addressed in 5414b44. P1. Checked against Harbor 0.20.0, the version pinned as P2-1. The live cell test stays opt-in. It needs a kernel that can load this P2-2. The pin script and The two root-user tests stay: one is Harbor's default
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📒 Files selected for processing (6)
packages/eval/README.mdpackages/eval/harbor/egress-proxy/network-policypackages/eval/harbor/relay_agent.pypackages/eval/harbor/test_cell_egress_namespace.pypackages/eval/harbor/test_relay_contract.pypackages/eval/src/__tests__/lifecycle-boundaries.test.ts
🚧 Files skipped from review as they are similar to previous changes (5)
- packages/eval/README.md
- packages/eval/harbor/egress-proxy/network-policy
- packages/eval/src/tests/lifecycle-boundaries.test.ts
- packages/eval/harbor/relay_agent.py
- packages/eval/harbor/test_cell_egress_namespace.py
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Pull request overview
This PR closes an egress-policy gap where Docker’s embedded DNS resolver (127.0.0.11) could be used as an unaudited bidirectional channel out of Eval cells, by (1) publishing the proxy’s IPv4 into the existing CA/cert volume, (2) pinning the proxy hostname in /etc/hosts as root before the subject starts, and (3) rejecting traffic to 127.0.0.11 ahead of the local-destination exemption in nftables.
Changes:
- Publish the egress proxy IPv4 to
/opt/maka-egress/proxy-ipv4and mount it into the sidecar/subject where needed. - Pin
maka-eval-mitmproxyto the published IPv4 in/etc/hosts(as root) so proxy resolution works after Docker DNS is refused. - Update nftables policy + tests/docs to reject
127.0.0.11correctly (address-based reject beforefib daddr type local accept) and lock the contract with new test coverage.
Reviewed changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
| packages/eval/src/tests/lifecycle-boundaries.test.ts | Locks in new contract expectations: sidecar CA mount, 127.0.0.11 reject ordering, proxy-ipv4 usage, and no getent in network-policy. |
| packages/eval/README.md | Updates documentation to reflect published proxy-ipv4, /etc/hosts pinning, and address-based Docker DNS refusal rationale. |
| packages/eval/harbor/test_relay_contract.py | Extends relay contract tests for hostname pinning (root), fail-closed behavior, host/IP validation, and policy ordering. |
| packages/eval/harbor/test_cell_egress_namespace.py | Adds a live Docker DNS probe and ensures hostname pinning happens before policy application; supports exec-as-user for root pinning. |
| packages/eval/harbor/relay_agent.py | Implements _pin_proxy_hostname() and associated validation/constants; integrates pin step into _require_constrained_subject(). |
| packages/eval/harbor/egress-proxy/network-policy | Removes DNS-based proxy resolution and rejects 127.0.0.11 before local accept; reads proxy IPv4 from the published file. |
| packages/eval/harbor/egress-proxy/entrypoint.sh | Publishes the proxy’s own IPv4 into the cert volume (atomic rename) alongside the CA cert. |
| packages/eval/harbor/docker-compose-egress-proxy.yaml | Mounts the CA/proxy-ipv4 volume into the sidecar and adds a proxy-ipv4 presence check to the proxy healthcheck. |
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Reject Unicode letters in Python before exec so they fail as an invalid host, matching the pin script. Drop the 0.0.0.0 fixture so a bind-all lint does not fire on a format-only IPv4 case.
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Astro-Han
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Thanks for tightening this boundary. The change solves the actual bootstrap cycle cleanly: the trusted proxy publishes its concrete IPv4, the relay validates and pins exactly that host in the subject, and only then may the namespace policy refuse Docker DNS. The validation is bounded and fail-closed, and the contract/adversarial tests cover malformed host/IP data and the intended DNS refusal.
From first principles, the subject needs one stable name before DNS disappears; persisting a single proxy address through the existing trusted volume is the smallest authority needed. I did not find a simpler solution that preserves fail-closed startup, nor any low-value production code or tests to remove.
I reviewed the latest head with independent @reviewer passes and a separate read-only ollama-cloud/deepseek-v4-flash high-effort pass. I did not run a local test suite; current CI is green. AI-assisted review; I verified the changed bootstrap and policy ordering, and excluded an initially raised namespace concern after confirming it was pre-existing in main, not introduced by this diff.
中文评论
感谢继续收紧这个边界。这个改动正确解决了启动依赖环：可信 proxy 先发布具体 IPv4，relay 校验后只把该 host 固定到 subject，随后 namespace policy 才拒绝 Docker DNS。整个过程有界、fail closed，契约测试和对抗测试覆盖了非法 host/IP 与预期的 DNS 拒绝。
从第一性原理看，subject 在 DNS 消失前只需要一个稳定名称；通过已有可信 volume 传递单个 proxy 地址，是足够且最小的 authority。没有发现更简单且仍保持 fail-closed 的方案，也没有需要删除的低质量代码或测试。
本次基于最新 head、独立 reviewer 和一次只读的 DeepSeek V4 Flash high-effort 审查；未运行本地测试，当前 CI 为绿色。AI 辅助审查；我已人工复核启动和 policy 顺序，并确认一条最初提出的 namespace 风险属于 main 既有行为，不是本 diff 引入，因此没有误归责给本 PR。
Summary
The namespace-local exemption keeps loopback provider proxies reachable, and with them Docker's resolver at
127.0.0.11. That resolver forwards unknown names to the host, so a TXT query can leave the cell and come back without touching mitmproxy./opt/maka-egress/proxy-ipv4on the certificate volume./tmpcache and nogetent, sodeny-allthen the firstallowstill has an address after Docker DNS is refused.maka-eval-mitmproxyin/etc/hostsas root after the isolation gate, soHTTPS_PROXYstill resolves for a supported non-rootagent.user.127.0.0.11before the generic local accept. Docker DNATs:53onto another local port before the filter hook; matching onlydport 53missed, andfib daddr type localthen accepted the rewritten packet.Fixes #2976
Verification
python3.13Harbor units — 47 pass (lifecycle 2 skipped, no GNUsetsidon macOS). Includes missingproxy-ipv4fail-closed and pin-as-root.node --test packages/eval/dist/**/*.test.js— 52/52, including lifecycle-boundaries locks for127.0.0.11reject,proxy-ipv4, nogetent, sidecar CA mount, andtouchof the audit log.MAKA_EVAL_EGRESS_NAMESPACE_TEST=1— 2/4. Cert volume (mitmproxy-ca-cert.pem+proxy-ipv4) and the isolation gate pass. Applying the checked-intable inetruleset fails on this Docker Desktop VM at the pre-existingfib daddr type localrule (NFT_FIB_INETis unset). Linux CI is the environment that can apply that family.maka-eval-egress-proxy:12.2.3+ subject + sidecar sharing the netns), closesttable ipequivalent (this kernel can loadipfib): 23/23.172.20.0.2; sidecar reads the same file withoutgetent./etc/hosts; root pin succeeds;getent hosts maka-eval-mitmproxyreturns the published IPv4.deny-allthen firstallowfrom the published file: proxy HTTPS 200;--noproxy, direct TCP, external UDP, Docker DNS, and ICMP blocked; loopback still reachable.Not run: full
maka eval runcohort (no Harbor / provider env on this host). Full workspacenpm testblocked by an unrelatedunlockAutoFollowtype error on currentmain.Checklist
Does this PR entail a change in behavior?