fix(skills): validate skill names and quote provisioning paths

Skill names become host/guest path segments interpolated into the
`bottle.exec` shell strings in each contrib provider's provision_skills.
They were validated only as strings, so a name with shell metacharacters
or path traversal could reach the command.

Layer two defenses:
  - Primary: reject any skill name that isn't kebab-case
    ([a-z][a-z0-9-]*) at manifest load, reusing the convention already
    enforced on bottle/agent filenames (new is_valid_entity_name helper
    in manifest_schema). Fails loud and early, protecting every consumer
    of the name — not just the exec call sites.
  - Failsafe: shlex.quote the interpolated skills_dir / dst paths in the
    claude, codex, and pi providers, so a future unvalidated field can't
    inject shell metacharacters even if it bypasses the load-time check.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NkwFXLFff9PYPy4wgVBJp9

bot_bottle/contrib/claude/agent_provider.py

@@ -217,7 +217,7 @@ class ClaudeAgentProvider(AgentProvider):
         if not agent.skills:
             return
         skills_dir = _skills_dir(plan.guest_home)
-        bottle.exec(f"mkdir -p {skills_dir}", user="root")
+        bottle.exec(f"mkdir -p {shlex.quote(skills_dir)}", user="root")
         for name in agent.skills:
             src = host_skill_dir(name)
             if not os.path.isdir(src):
@@ -227,9 +227,13 @@ class ClaudeAgentProvider(AgentProvider):
                 )
             dst = f"{skills_dir}/{name}"
             info(f"copying skill {name} into {bottle.name}:{dst}")
-            bottle.exec(f"rm -rf {dst} && mkdir -p {dst}", user="root")
+            # Defense in depth: skill names are validated kebab-case at
+            # manifest load, but quote the path so a future unvalidated
+            # field can't inject shell metacharacters here either.
+            dst_q = shlex.quote(dst)
+            bottle.exec(f"rm -rf {dst_q} && mkdir -p {dst_q}", user="root")
             bottle.cp_in(f"{src}/.", f"{dst}/")
-            bottle.exec(f"chown -R node:node {dst}", user="root")
+            bottle.exec(f"chown -R node:node {dst_q}", user="root")
 
     def provision_prompt(self, plan: "BottlePlan", bottle: "Bottle") -> str | None:
         """Copy the prompt file into the guest, fix ownership/mode.

bot_bottle/contrib/codex/agent_provider.py

@@ -183,7 +183,7 @@ class CodexAgentProvider(AgentProvider):
         if not agent.skills:
             return
         skills_dir = _skills_dir(plan.guest_home)
-        bottle.exec(f"mkdir -p {skills_dir}", user="root")
+        bottle.exec(f"mkdir -p {shlex.quote(skills_dir)}", user="root")
         for name in agent.skills:
             src = host_skill_dir(name)
             if not os.path.isdir(src):
@@ -193,9 +193,13 @@ class CodexAgentProvider(AgentProvider):
                 )
             dst = f"{skills_dir}/{name}"
             info(f"copying skill {name} into {bottle.name}:{dst}")
-            bottle.exec(f"rm -rf {dst} && mkdir -p {dst}", user="root")
+            # Defense in depth: skill names are validated kebab-case at
+            # manifest load, but quote the path so a future unvalidated
+            # field can't inject shell metacharacters here either.
+            dst_q = shlex.quote(dst)
+            bottle.exec(f"rm -rf {dst_q} && mkdir -p {dst_q}", user="root")
             bottle.cp_in(f"{src}/.", f"{dst}/")
-            bottle.exec(f"chown -R node:node {dst}", user="root")
+            bottle.exec(f"chown -R node:node {dst_q}", user="root")
 
     def provision_prompt(self, plan: "BottlePlan", bottle: "Bottle") -> str | None:
         """Copy the prompt file into the guest, fix ownership/mode.

bot_bottle/contrib/pi/agent_provider.py

@@ -238,7 +238,7 @@ class PiAgentProvider(AgentProvider):
         if not agent.skills:
             return
         skills_dir = _skills_dir(plan.guest_home)
-        bottle.exec(f"mkdir -p {skills_dir}", user="root")
+        bottle.exec(f"mkdir -p {shlex.quote(skills_dir)}", user="root")
         for name in agent.skills:
             src = host_skill_dir(name)
             if not os.path.isdir(src):
@@ -248,9 +248,13 @@ class PiAgentProvider(AgentProvider):
                 )
             dst = f"{skills_dir}/{name}"
             info(f"copying skill {name} into {bottle.name}:{dst}")
-            bottle.exec(f"rm -rf {dst} && mkdir -p {dst}", user="root")
+            # Defense in depth: skill names are validated kebab-case at
+            # manifest load, but quote the path so a future unvalidated
+            # field can't inject shell metacharacters here either.
+            dst_q = shlex.quote(dst)
+            bottle.exec(f"rm -rf {dst_q} && mkdir -p {dst_q}", user="root")
             bottle.cp_in(f"{src}/.", f"{dst}/")
-            bottle.exec(f"chown -R node:node {dst}", user="root")
+            bottle.exec(f"chown -R node:node {dst_q}", user="root")
 
     def provision_prompt(self, plan: "BottlePlan", bottle: "Bottle") -> str | None:
         prompt_path = _prompt_path(plan.guest_home)

bot_bottle/manifest_agent.py

@@ -8,7 +8,7 @@ from typing import cast
 from .agent_provider import PROVIDER_TEMPLATES
 from .manifest_util import ManifestError, as_json_object
 from .manifest_git import ManifestGitUser
-from .manifest_schema import AGENT_MODEL_KEYS
+from .manifest_schema import AGENT_MODEL_KEYS, is_valid_entity_name
 
 
 @dataclass(frozen=True)
@@ -161,6 +161,16 @@ class ManifestAgent:
                         f"agent '{name}' skills[{i}] must be a string "
                         f"(was {type(skill).__name__})"
                     )
+                # Skill names become host/guest path segments and are
+                # interpolated into provisioning shell commands, so they
+                # must fit the same kebab-case convention as bottle/agent
+                # filenames — rejecting anything that could break out of a
+                # path segment or inject shell metacharacters.
+                if not is_valid_entity_name(skill):
+                    raise ManifestError(
+                        f"agent '{name}' skills[{i}] {skill!r} is not a valid "
+                        f"skill name; must match [a-z][a-z0-9-]*"
+                    )
                 collected.append(skill)
             skills = tuple(collected)
 

bot_bottle/manifest_schema.py

@@ -33,13 +33,20 @@ AGENT_KEYS = (
 AGENT_MODEL_KEYS = AGENT_KEYS | frozenset({"prompt"})
 
 
+def is_valid_entity_name(name: str) -> bool:
+    """True if `name` fits the kebab-case `[a-z][a-z0-9-]*` convention
+    shared by bottle/agent filenames and skill names. Names that satisfy
+    this are also safe to interpolate into a host/guest path segment."""
+    return bool(_FILENAME_RX.match(name))
+
+
 def entity_name_from_path(path: Path) -> str | None:
     """Return the entity name implied by the filename, or None if the
     filename does not fit the [a-z][a-z0-9-]* convention."""
     if path.suffix != ".md":
         return None
     stem = path.stem
-    if not _FILENAME_RX.match(stem):
+    if not is_valid_entity_name(stem):
         return None
     return stem