feat: Secure prompt-based skills system (Phases 1-4) (#51)

* feat: Add secure prompt-based skills system (Phase 1 MVP)

Implement a skills system that extends the agent with prompt-level
instructions from local directories. Skills declare activation criteria,
tool permissions, and trust tiers that determine authority attenuation.

Core security model: the minimum trust level of any active skill
determines a tool ceiling -- tools above the ceiling are removed from
the LLM's tool list entirely at the API level, preventing prompt-based
manipulation.

New modules:
- skills/mod.rs: Core types (SkillTrust, SkillManifest, LoadedSkill)
- skills/scanner.rs: Content scanner for manipulation detection
- skills/registry.rs: Filesystem discovery and manifest parsing
- skills/selector.rs: Deterministic two-phase prefilter (no LLM)
- skills/attenuation.rs: Trust-based tool filtering

Integration:
- Agent loop selects skills per-turn and applies tool attenuation
- Reasoning engine injects skill context with structural isolation
- Config supports SKILLS_ENABLED, SKILLS_DIR, SKILLS_MAX_ACTIVE,
  SKILLS_MAX_CONTEXT_TOKENS environment variables
- Disabled by default (SKILLS_ENABLED=false)

41 new tests covering all modules.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: Address all adversarial review findings for skills system

Security fixes:
- Escape skill name/version in XML attributes to prevent trust spoofing
- Escape prompt content to prevent </skill> tag breakout
- Require integrity hash for Verified/Community tier skills
- Validate skill names against [a-zA-Z0-9][a-zA-Z0-9._-]{0,63}
- Add 64 KiB file size limit on prompt.md

Bug fixes:
- Use actual SkillsConfig from AgentDeps instead of SkillsConfig::default()
- Add skills_config field to AgentDeps, wired through from main.rs

Performance:
- Pre-compile regex patterns at load time (cached on LoadedSkill)
- Selector uses pre-compiled patterns instead of recompiling per message
- Switch all std::fs to tokio::fs for non-blocking async I/O

Hardening:
- Cap keyword score at 30 points to prevent keyword stuffing attacks
- Enforce max 20 keywords and 5 patterns per skill
- Normalize line endings (CRLF/CR to LF) before hashing
- Also includes cargo fmt formatting fixes for adjacent code

Tests: 54 skills tests pass (up from 41), zero new clippy warnings.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: Address medium/low severity findings from adversarial review

Fixes all 18 medium/low severity findings identified by the security review:

- mod.rs: Add MAX_TAGS_PER_SKILL cap (10) in enforce_limits(); use
  RegexBuilder with 64 KiB size_limit to prevent ReDoS; replace
  case-enumerated escape_skill_content with regex matching all case
  variants plus whitespace/null byte injection between </ and skill;
  document allowed_patterns as unenforced until Phase 2; document
  Marketplace URL validation as Phase 3 concern

- registry.rs: Add MAX_MANIFEST_FILE_SIZE (16 KiB) check before reading;
  add symlink detection via symlink_metadata to reject symlinks in
  discover_local; add MAX_DISCOVERED_SKILLS (100) cap; validate
  prompt_hash format (sha256: + 64 hex chars); warn on name collision
  before overwriting; accept SkillSource parameter in load_skill instead
  of always using Local; add InvalidHashFormat, ManifestTooLarge,
  SymlinkDetected error variants

- selector.rs: Add MAX_TAG_SCORE (15) cap parallel to keyword cap; warn
  when declared max_context_tokens diverges >2x from actual prompt size

- scanner.rs: Add mixed-script homoglyph detection (Cyrillic, Greek,
  Armenian unicode ranges); document token-boundary bypass and semantic
  paraphrasing as known limitations

- attenuation.rs: Document READ_ONLY_TOOLS maintenance requirements

- agent_loop.rs: Surface scan warnings via structured tracing; add
  structured audit events for skill activation and tool attenuation

61 tests pass, 0 new clippy warnings.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: Address 12 findings from second adversarial security review

HIGH:
- Escape opening <skill tags in prompt content (prevents fake skill block injection)
- Scan manifest metadata fields (description, author, tags, reasons) not just prompt
- Block trust downgrade on name collision (existing Local can't be replaced by Community)

MEDIUM:
- Eliminate TOCTOU gap: read files then check size instead of metadata-then-read
- Reject file-level symlinks in load_skill (prompt.md, skill.toml)
- Truncate and filter manifest.skill.tags (prevent unlimited tag scoring)
- Cap regex pattern score at 40 (prevent 5x20=100 dominating keyword+tag)
- Add doc comment about skill_list tool exposing metadata (sanitization required)
- Move Community disclaimer inside <skill> tags (not outside structural boundary)
- Filter keywords/tags shorter than 3 chars (prevent broad matching)

LOW:
- Enforce minimum token_cost of 1 (max_context_tokens=0 can't bypass budget)
- Remove redundant try_exists checks in discover_local (let load_skill handle errors)

70 skills tests passing.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* feat: Add HTTP endpoint scoping for skills (Phase 1)

Skills that declare an [http] section in skill.toml now have their HTTP
requests constrained to declared endpoints at runtime. This addresses
the gap where allowed_patterns was parsed but never enforced -- once the
http tool was visible via attenuation, the LLM could reach any URL.

Enforcement reuses EndpointPattern/AllowlistValidator from the WASM
capability system. Semantics: if no active skill declares [http], all
requests pass through (backward compat). If any skill declares [http],
URLs must match at least one skill's allowlist (union). Community skills'
[http] declarations are silently ignored (defense in depth).

Shell commands using curl/wget are also validated against scopes.

Scanner gains detection for known exfiltration domains (webhook.site,
ngrok.io, etc.), overly broad wildcards, and credential/host mismatches.

Closes #38

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* style: Apply cargo fmt to http_scoping.rs

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* style: Apply cargo fmt across codebase

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* feat: Add parameter-level permission enforcement for skills (Phase 2)

Activates enforcement of `allowed_patterns` in skill.toml permissions.
Previously these patterns were parsed but not enforced -- a Verified skill
declaring `permissions.shell` with `allowed_patterns = [{command = "cargo *"}]`
could still run any shell command. Now the enforcer validates tool parameters
against declared glob patterns before execution.

Key changes:
- New `enforcer.rs` module with `SkillPermissionEnforcer`, `glob_to_regex()`,
  and `validate_tool_call()` with union semantics across active skills
- Typed pattern enums (`ShellPattern`, `FilePathPattern`, `MemoryTargetPattern`)
  replace the previous `Vec<serde_json::Value>` in `ToolPermissionDeclaration`
- Scanner gains `scan_permission_patterns()` detecting dangerous patterns
  (rm, sudo, curl, bare wildcards, command chaining, sensitive paths, identity files)
- Registry blocks non-Local skills with critical permission pattern warnings
- Agent loop threads enforcer into `execute_chat_tool` alongside HTTP scoping

Trust interaction: Community patterns ignored, Verified enforced, Local without
patterns unrestricted, Local with patterns enforced as guidance. Union semantics
across skills -- tool call allowed if ANY skill's patterns permit it.

34 new tests. All 818 library tests pass.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* feat: Add worker permission enforcement and LLM behavioral analysis (Phase 3+4)

Phase 3 - Worker-side permission enforcement:
- Add SerializedToolPermission/SerializedPattern DTOs for HTTP boundary crossing
- Extend JobDescription, ContainerHandle, and orchestrator API to carry permissions
- CreateJobTool snapshots and forwards skill permissions to spawned workers
- Worker runtime builds SkillPermissionEnforcer and checks before tool execution
- Load-time token budget enforcement rejects prompts exceeding 2x declared budget
- Deduplicate enforcer construction: from_active_skills() delegates to from_serialized()

Phase 4 - LLM behavioral analysis:
- BehavioralAnalyzer with cached, LLM-based semantic content analysis
- Structured output parsing (FINDING|CATEGORY|SEVERITY|DESCRIPTION or CLEAN)
- Content-hash caching with bounded size (MAX_CACHE_ENTRIES=256)
- Graceful degradation when LLM unavailable
- Integrated into load_skill() for non-Local skills; critical findings block loading

Review fixes:
- Real cache tests with CountingLlm mock (test_cache_hit, test_cache_miss, test_cache_bounded)
- UTF-8-safe truncate() in worker runtime
- Few-shot examples in behavioral analysis prompt
- Documented max_context_tokens=0 opt-out and create_job() permission gap

848 tests passing, no new clippy warnings.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: Address review feedback from serrrfirat on skills-phase2

- Fix truncate_cmd UTF-8 panic: use char-boundary-aware slicing
- Remove redundant effective_tools branching in reasoning.rs
- Document cache eviction as known limitation (arbitrary, not LRU)
- Add safety comment on SkillTrust enum ordering (security-critical)
- Simplify active_skills selection (prefilter_skills handles empty input)

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: address remaining skills review feedback

* refactor: replace skills system with OpenClaw SKILL.md format + 2-state trust

Replace the 5-gate, 3-tier trust hierarchy (scanner, behavioral analyzer,
parameter-level enforcer, HTTP endpoint scoping) with a simplified 3-layer
security model: gating -> attenuation -> Docker confinement.

Key changes:
- SKILL.md format (YAML frontmatter + markdown prompt) replaces skill.toml + prompt.md
- 2-state trust (Installed/Trusted) replaces 3-tier (Community/Verified/Local)
- New parser.rs for SKILL.md parsing with serde_yaml
- New gating.rs for requirements checking (bins/env/config)
- Simplified registry with 2-location discovery (workspace + user dirs)
- Removed scanner, behavioral_analyzer, enforcer, http_scoping (~4,100 lines)
- Removed skill_permissions propagation through job/orchestrator/worker pipeline
- Added serde_yaml dependency for YAML frontmatter parsing

Net: -5,298 lines, 59 skills tests pass, 907 total tests pass.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* feat: add in-app skill management tools and ClawHub catalog integration

Add 4 chat-callable tools (skill_list, skill_search, skill_install,
skill_remove) plus matching web gateway endpoints for managing skills
at runtime. The catalog fetches from ClawHub's public registry API
at runtime rather than bundling entries at compile time.

Key changes:
- SkillRegistry gains mutation methods (install_skill, remove_skill,
  reload, find_by_name) with Arc<RwLock> for concurrent access
- New catalog module queries ClawHub /api/v1/search with in-memory
  caching (5-min TTL, configurable via CLAWHUB_REGISTRY env var)
- skill_list and skill_search added to READ_ONLY_TOOLS for safe use
  under Installed trust ceiling
- Web gateway gets /api/skills, /api/skills/search, /api/skills/install,
  and /api/skills/{name} DELETE endpoints

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: address PR #51 review feedback from ilblackdragon

Security:
- Add SSRF protection to fetch_skill_content: require HTTPS, reject
  private/loopback/link-local IPs and internal hostnames, disable
  redirects. Gateway install handler now reuses the same validation.
- URL-encode slug in skill_download_url to prevent query injection.
- Require X-Confirm-Action header on gateway skill install/remove
  endpoints (equivalent to chat tool requires_approval gate).

Correctness:
- Eliminate all block_in_place/block_on usage in skill tools and
  gateway handlers. Split install into prepare_install_to_disk (static
  async, no lock) + commit_install (sync, brief write lock). Same
  pattern for remove: validate_remove + delete_skill_files + commit_remove.
- Write normalized content to disk in install_skill (was writing
  original un-normalized content, causing hash mismatch on re-read).
- Fix token estimation from 0.75 to 0.25 tokens/byte (~4 chars per
  token) in registry.rs, selector.rs, and standalone loader.

Dependencies:
- Replace deprecated serde_yaml 0.9 with serde_yml 0.0.12.
- Remove unused toml dependency.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>

Cargo.lock

@@ -2533,6 +2533,7 @@ dependencies = [
  "security-framework 3.5.1",
  "serde",
  "serde_json",
+ "serde_yml",
  "sha2",
  "subtle",
  "tempfile",
@@ -2857,6 +2858,16 @@ dependencies = [
  "zerocopy 0.7.35",
 ]
 
+[[package]]
+name = "libyml"
+version = "0.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3302702afa434ffa30847a83305f0a69d6abd74293b6554c18ec85c7ef30c980"
+dependencies = [
+ "anyhow",
+ "version_check",
+]
+
 [[package]]
 name = "linux-raw-sys"
 version = "0.4.15"
@@ -4616,6 +4627,21 @@ dependencies = [
  "syn 2.0.114",
 ]
 
+[[package]]
+name = "serde_yml"
+version = "0.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59e2dd588bf1597a252c3b920e0143eb99b0f76e4e082f4c92ce34fbc9e71ddd"
+dependencies = [
+ "indexmap 2.13.0",
+ "itoa",
+ "libyml",
+ "memchr",
+ "ryu",
+ "serde",
+ "version_check",
+]
+
 [[package]]
 name = "sha1"
 version = "0.10.6"