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fix(security): verify private runtime directories - #42
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📝 WalkthroughWalkthroughRefactors dgram proxy retry handling to retry sends in-place instead of via a retry-events channel, adds transport send-stall dead-link detection and packet-conn rebind hooks, introduces a ChangesDgram Proxy/Transport Resilience
Estimated code review effort: 4 (Complex) | ~60 minutes Private Directory Enforcement (safedir)
Estimated code review effort: 2 (Simple) | ~15 minutes Daemon Output-Ack-Gated Paint Deferral
Estimated code review effort: 3 (Moderate) | ~25 minutes Client Offline Link Reconnect Handling
Estimated code review effort: 2 (Simple) | ~10 minutes Sequence Diagram(s)sequenceDiagram
participant Client
participant Daemon
participant runConnLoop
Daemon->>Client: MsgOutput (ack lag reaches cap)
Daemon->>Daemon: paint() marks paintDeferred, returns early
Client->>runConnLoop: MsgAck
runConnLoop->>Daemon: takeDeferredPaint() returns true
Daemon->>Client: paint(sess, ac, false) flushes diff
sequenceDiagram
participant DaemonOutput
participant copyFrames
participant ClientTransport
DaemonOutput->>copyFrames: received frame
copyFrames->>ClientTransport: Send(frame)
ClientTransport-->>copyFrames: recoverable error
loop retryRecoverable
copyFrames->>copyFrames: wait RetryBackoff
copyFrames->>ClientTransport: retry Send(same frame)
end
ClientTransport-->>copyFrames: success
Possibly related PRs
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🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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Pull request overview
This PR hardens vev’s runtime and on-disk state handling by introducing a shared pkg/safedir.EnsurePrivate helper and routing multiple runtime directory creation points through it, so vev refuses to use pre-existing directories that are not private to the current user.
Changes:
- Added
pkg/safedir.EnsurePrivateto create/validate private (0700) vev-owned directories and reject symlinks / wrong ownership / wrong perms. - Wired directory setup for KV storage, logging, daemon spawn lock, IPC socket directory, snapshot storage, and UDP proxy registry through
safedir. - Added regression coverage for hostile directory scenarios and adjusted tests to exercise the “create nested vev dir” behavior.
Reviewed changes
Copilot reviewed 11 out of 11 changed files in this pull request and generated no comments.
Show a summary per file
| File | Description |
|---|---|
| pkg/safedir/safedir.go | Adds EnsurePrivate helper to create/validate private directories. |
| pkg/safedir/safedir_test.go | Adds unit tests covering permission, symlink, and non-directory rejection. |
| pkg/kv/kv.go | Uses EnsurePrivate for WAL directory creation before opening the store file. |
| internal/logging/logging.go | Secures the logging directory with EnsurePrivate before opening log files. |
| internal/app/spawn.go | Secures the daemon socket/spawn directory with EnsurePrivate before spawn locking. |
| internal/app/spawn_test.go | Updates tests to use nested “vev” dir paths consistent with hardened setup. |
| internal/app/daemon_integration_test.go | Starts daemons under a nested “vev” dir path. |
| internal/adapters/snapshot/store.go | Uses EnsurePrivate for snapshot dir creation (but retains a redundant chmod). |
| internal/adapters/ipc/listener.go | Secures socket dir with EnsurePrivate and wraps errors with clearer context. |
| internal/adapters/ipc/listener_test.go | Adds hostile socket-dir rejection test and updates temp dir usage. |
| internal/adapters/dgram/proxy_registry.go | Secures UDP proxy registry dir with EnsurePrivate before locking. |
Comments suppressed due to low confidence (1)
internal/adapters/snapshot/store.go:44
- After calling safedir.EnsurePrivate(s.dir), the directory is already verified to have exact 0700 perms. The subsequent os.Chmod(s.dir, 0o700) is therefore redundant and can also introduce a new failure mode on filesystems where chmod is unsupported/restricted (even when perms are already acceptable), causing snapshot writes to fail unnecessarily.
if err := safedir.EnsurePrivate(s.dir); err != nil {
return fmt.Errorf("create snapshot dir: %w", err)
}
if err := os.Chmod(s.dir, 0o700); err != nil {
return fmt.Errorf("chmod snapshot dir: %w", err)
}
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chore(ci): add build, lint, and test workflow
Add a per-frame first-send timestamp and a checkSendStall pass on the resend/heartbeat ticks: when the oldest unacked reliable frame stays unacked for deadAfter despite a retransmit, declare the link dead. This catches one-way-dead links whose receive side stays fresh from peer heartbeats, which the receive-silence check misses. Also move the one-shot socket hop from the Offline (30s) transition to Probing (20s) so the client rebind runs before the link is abandoned.
Retry the same daemon->client frame in place while the link error stays recoverable instead of restarting the copier and dropping the in-flight frame, which desynchronized the client screen on a reliable stream. Retries no longer arm the idle TTL: it is driven solely by link-state events (armed on Degraded/Probing/Offline, disarmed on Connected, Dead is immediate). A persistently pending-full but Connected link therefore survives rather than being killed after 30s. Send-stall death now comes from the transport layer.
Build the client transport with a RebindPacketConn that binds a fresh local UDP socket via the existing listen helper, so the probing-state socket hop can heal NAT rebinds and stale conntrack paths in production.
On a LinkStateOffline event, draw the toast and return a retryable errLinkOffline so Run re-dials with the resume token at ~30s of silence instead of waiting for the transport to reach Dead at 60s. Degraded and Probing stay toast-only.
Add maxUnackedOutputStates: when the client is that many output states behind, paint defers the diff instead of composing another, marking a per-client paintDeferred flag under sendMu. The MsgOutputAck handler flushes one cumulative paint once acks catch up. Reset paints (explicit invalidations) bypass the gate and clear the flag; park clears it too. This paces the daemon's paint rate to the client's ack rate so heavy output degrades to lower fps on a slow link instead of overflowing the UDP proxy window and tripping the 1s send watchdog.
Review findings on PR #47: exercise the flush end-to-end via runConnLoop instead of calling advanceOutputAck/takeDeferredPaint directly, and make requireNoOutputFrame drain non-output frames for the full window instead of returning on the first frame.
fix(remote): stop UDP attach collapsing under congestion
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Actionable comments posted: 2
Caution
Some comments are outside the diff and can’t be posted inline due to platform limitations.
⚠️ Outside diff range comments (1)
internal/adapters/snapshot/store.go (1)
39-44: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low valueRedundant
os.Chmodaftersafedir.EnsurePrivate.
safedir.EnsurePrivatealready fails the call unlesss.diris exactly0700(owned by the current uid). By the time execution reaches line 42, the directory is guaranteed to already be0700, making thisos.Chmoda no-op that only adds an unreachable error path. This was needed previously because bareos.MkdirAlldidn't re-verify existing-directory permissions, but that rationale no longer applies.♻️ Proposed cleanup
func (s *Store) Write(name string, data []byte) error { if err := safedir.EnsurePrivate(s.dir); err != nil { return fmt.Errorf("create snapshot dir: %w", err) } - if err := os.Chmod(s.dir, 0o700); err != nil { - return fmt.Errorf("chmod snapshot dir: %w", err) - } tmp, err := os.CreateTemp(s.dir, ".tmp-*")🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the rest with a brief reason, keep changes minimal, and validate. In `@internal/adapters/snapshot/store.go` around lines 39 - 44, Remove the redundant permission fix-up in snapshot store initialization: in the snapshot directory setup path inside the Store logic, `safedir.EnsurePrivate` already guarantees `s.dir` is private, so the subsequent `os.Chmod` call in that same block is unnecessary. Update the initialization flow to keep only the `safedir.EnsurePrivate` check and its error handling, leaving `Store` to fail early if the directory is not already `0700`.
🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
Inline comments:
In `@internal/adapters/dgram/proxy.go`:
- Around line 151-172: The retry loop in the copier can keep running after Run
exits because the shared context is not canceled on every exit path. Update Run
to derive a child context for the copier goroutines and defer its cancel so both
the daemon and client copy paths stop when Run returns, including idle-timer and
EOF exits. Make sure the retry/backoff logic in proxyCopySender (the Send loop
with recoverableClientLink and c.clk.NewTimer) observes that child context
instead of continuing to treat dgram closed errors as recoverable after
shutdown.
In `@pkg/safedir/safedir.go`:
- Around line 14-39: EnsurePrivate currently validates a path snapshot in
EnsurePrivate but still leaves callers using the string path afterward, which
allows a post-check swap. Update the safedir flow to return or retain a pinned
directory handle from EnsurePrivate using dirfd-based opening and fstat on that
handle, then have subsequent operations use that handle or relative lookups
instead of re-resolving the path. Keep the existing symlink, ownership, and 0700
checks in EnsurePrivate, but make them part of a handle-based validation so the
directory cannot be replaced after validation.
---
Outside diff comments:
In `@internal/adapters/snapshot/store.go`:
- Around line 39-44: Remove the redundant permission fix-up in snapshot store
initialization: in the snapshot directory setup path inside the Store logic,
`safedir.EnsurePrivate` already guarantees `s.dir` is private, so the subsequent
`os.Chmod` call in that same block is unnecessary. Update the initialization
flow to keep only the `safedir.EnsurePrivate` check and its error handling,
leaving `Store` to fail early if the directory is not already `0700`.
🪄 Autofix (Beta)
Fix all unresolved CodeRabbit comments on this PR:
- Push a commit to this branch (recommended)
- Create a new PR with the fixes
ℹ️ Review info
⚙️ Run configuration
Configuration used: Organization UI
Review profile: ASSERTIVE
Plan: Pro
Run ID: e6218331-d314-4cdb-8001-7e966c0ae71f
📒 Files selected for processing (29)
internal/adapters/dgram/proxy.gointernal/adapters/dgram/proxy_registry.gointernal/adapters/dgram/proxy_registry_test.gointernal/adapters/dgram/proxy_test.gointernal/adapters/dgram/ssh_dialer.gointernal/adapters/dgram/transport.gointernal/adapters/dgram/transport_test.gointernal/adapters/ipc/listener.gointernal/adapters/ipc/listener_test.gointernal/adapters/snapshot/store.gointernal/adapters/snapshot/store_test.gointernal/app/daemon_integration_test.gointernal/app/spawn.gointernal/app/spawn_test.gointernal/logging/logging.gointernal/logging/logging_test.gointernal/persist/persist_test.gointernal/usecase/client/client.gointernal/usecase/client/reconnect.gointernal/usecase/client/reconnect_toast_test.gointernal/usecase/daemon/client.gointernal/usecase/daemon/daemon.gointernal/usecase/daemon/paint_gate_test.gointernal/usecase/daemon/render.gointernal/usecase/daemon/resume.gopkg/kv/kv.gopkg/kv/kv_test.gopkg/safedir/safedir.gopkg/safedir/safedir_test.go
Comment on lines
+151
to
172
| // Retry the same frame in place while the destination link error stays | ||
| // recoverable (congestion, transient path loss). The frame is never | ||
| // dropped — on a reliable stream a gap desynchronizes the client screen. | ||
| for { | ||
| if err := dir.dst.Send(f); err != nil { | ||
| if dir.retryPendingFull && errors.Is(err, ErrPendingFull) && recoverableClientLink(dir.dst, err) { | ||
| if !retrying { | ||
| retrying = true | ||
| if !sendProxyRetryEvent(c.ctx, c.retryEvents, proxyRetryStart) { | ||
| return | ||
| } | ||
| } | ||
| t := c.clk.NewTimer(c.retryBackoff) | ||
| select { | ||
| case <-t.C(): | ||
| t.Stop() | ||
| continue | ||
| case <-c.ctx.Done(): | ||
| t.Stop() | ||
| return | ||
| } | ||
| } | ||
| c.errCh <- proxyCopyErr{kind: dir.sendKind, err: err} | ||
| return | ||
| err := dir.dst.Send(f) | ||
| if err == nil { | ||
| break | ||
| } | ||
| if retrying && !sendProxyRetryEvent(c.ctx, c.retryEvents, proxyRetryDone) { | ||
| return | ||
| if dir.retryRecoverable && recoverableClientLink(dir.dst, err) { | ||
| t := c.clk.NewTimer(c.retryBackoff) | ||
| select { | ||
| case <-t.C(): | ||
| t.Stop() | ||
| continue | ||
| case <-c.ctx.Done(): | ||
| t.Stop() | ||
| return | ||
| } | ||
| } | ||
| break | ||
| c.errCh <- proxyCopyErr{kind: dir.sendKind, err: err} | ||
| return | ||
| } |
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🩺 Stability & Availability | 🟠 Major | 🏗️ Heavy lift
🧩 Analysis chain
🏁 Script executed:
#!/bin/bash
# Inspect Close() and LinkState transition in the real transport to confirm
# whether Close forces a non-recoverable (Dead) link state.
fd -e go . internal/adapters/dgram --exec rg -nP -C4 'func .*Close\(|LinkState\s*\(|LinkStateDead' {}Repository: bnema/vev
Length of output: 6870
🏁 Script executed:
#!/bin/bash
set -euo pipefail
printf '\n== proxy.go outline ==\n'
ast-grep outline internal/adapters/dgram/proxy.go --view expanded || true
printf '\n== proxy.go relevant lines ==\n'
sed -n '1,260p' internal/adapters/dgram/proxy.go
printf '\n== transport.go outline ==\n'
ast-grep outline internal/adapters/dgram/transport.go --view expanded || true
printf '\n== transport.go relevant lines ==\n'
sed -n '1,420p' internal/adapters/dgram/transport.goRepository: bnema/vev
Length of output: 22535
🏁 Script executed:
#!/bin/bash
set -euo pipefail
printf '\n== closeWithError and surrounding transport state ==\n'
sed -n '780,860p' internal/adapters/dgram/transport.go
printf '\n== tests mentioning Close / LinkStateDead / offline states ==\n'
rg -n -C3 'Close\(\)|LinkStateDead|LinkStateOffline|LinkStateDegraded|LinkStateProbing|ErrLinkDead|ErrPendingFull' internal/adapters/dgram/*_test.goRepository: bnema/vev
Length of output: 28839
Cancel the copier context when Run exits. Client.Close() does not force LinkState() to Dead, so a daemon→client retry that was already in the backoff loop can keep treating errors.New("dgram: closed") as recoverable after the idle-timer or EOF exit paths. Derive a child context in Run and defer cancel() so both copier goroutines stop on every exit path.
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@internal/adapters/dgram/proxy.go` around lines 151 - 172, The retry loop in
the copier can keep running after Run exits because the shared context is not
canceled on every exit path. Update Run to derive a child context for the copier
goroutines and defer its cancel so both the daemon and client copy paths stop
when Run returns, including idle-timer and EOF exits. Make sure the
retry/backoff logic in proxyCopySender (the Send loop with recoverableClientLink
and c.clk.NewTimer) observes that child context instead of continuing to treat
dgram closed errors as recoverable after shutdown.
Comment on lines
+14
to
+39
| func EnsurePrivate(dir string) error { | ||
| if err := os.MkdirAll(dir, 0o700); err != nil { | ||
| return err | ||
| } | ||
| fi, err := os.Lstat(dir) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| if fi.Mode()&os.ModeSymlink != 0 { | ||
| return fmt.Errorf("safedir: %s is a symlink", dir) | ||
| } | ||
| if !fi.IsDir() { | ||
| return fmt.Errorf("safedir: %s is not a directory", dir) | ||
| } | ||
| st, ok := fi.Sys().(*syscall.Stat_t) | ||
| if !ok { | ||
| return fmt.Errorf("safedir: cannot stat %s", dir) | ||
| } | ||
| if int(st.Uid) != os.Getuid() { | ||
| return fmt.Errorf("safedir: %s is owned by uid %d, not current uid %d — refusing to use it", dir, st.Uid, os.Getuid()) | ||
| } | ||
| if perm := fi.Mode().Perm(); perm != 0o700 { | ||
| return fmt.Errorf("safedir: %s has permissions %04o, want 0700 — refusing to use it", dir, perm) | ||
| } | ||
| return nil | ||
| } |
There was a problem hiding this comment.
🔒 Security & Privacy | 🟠 Major | 🏗️ Heavy lift
🧩 Analysis chain
🏁 Script executed:
#!/bin/bash
set -euo pipefail
printf '\n== File list ==\n'
git ls-files 'pkg/safedir/*' 'pkg/**/*' | sed -n '1,120p'
printf '\n== safedir.go (lines with numbers) ==\n'
cat -n pkg/safedir/safedir.go
printf '\n== Search for EnsurePrivate call sites ==\n'
rg -n 'EnsurePrivate\(' .
printf '\n== Search for pkg/safedir imports ==\n'
rg -n 'pkg/safedir|safedir\.EnsurePrivate' .
printf '\n== Build tags / platform guards near safedir ==\n'
rg -n '^//go:build|^// \+build|syscall.Stat_t|ModeSymlink|MkdirAll' pkg/safedir pkg -g '!**/*_test.go'Repository: bnema/vev
Length of output: 4890
🏁 Script executed:
#!/bin/bash
set -euo pipefail
printf '\n== safedir tests ==\n'
cat -n pkg/safedir/safedir_test.go
printf '\n== caller snippets ==\n'
for f in internal/adapters/ipc/listener.go internal/adapters/dgram/proxy_registry.go internal/adapters/snapshot/store.go internal/logging/logging.go internal/app/spawn.go pkg/kv/kv.go; do
echo
echo "### $f"
sed -n '1,140p' "$f" | cat -n
done
printf '\n== openat / O_DIRECTORY / fstat search ==\n'
rg -n 'O_DIRECTORY|openat|fstat|Fstat|open\(' pkg internalRepository: bnema/vev
Length of output: 31951
Close the post-validation path race. EnsurePrivate checks a path snapshot, but callers keep using the string path for later opens/renames, so a writable parent can swap the entry after validation and bypass the 0700/ownership guarantee. Use a pinned directory handle (O_DIRECTORY/fstat, or keep operations relative to a dirfd) instead of re-resolving the path.
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@pkg/safedir/safedir.go` around lines 14 - 39, EnsurePrivate currently
validates a path snapshot in EnsurePrivate but still leaves callers using the
string path afterward, which allows a post-check swap. Update the safedir flow
to return or retain a pinned directory handle from EnsurePrivate using
dirfd-based opening and fstat on that handle, then have subsequent operations
use that handle or relative lookups instead of re-resolving the path. Keep the
existing symlink, ownership, and 0700 checks in EnsurePrivate, but make them
part of a handle-based validation so the directory cannot be replaced after
validation.
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Summary
pkg/safedir.EnsurePrivatefor vev-owned private directoriesVerification
Stack: 2/6. Base PR: #41.
Summary by CodeRabbit
New Features
Bug Fixes