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Keep agent-planted git hooks and drivers out of capture - #2071
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The capture, the re-attach capture and the branch commit ran git inside the agent's clone after its turn, with the network on and no hardening. An agent that wrote its own .git during the run could make those commands run its code: client hooks (a vetoing pre-commit silently lost the produced branch), an agent-set core.hooksPath, a core.fsmonitor program, and textconv or external diff drivers selected through .gitattributes or diff.external. Every git command over the agent clone now goes through one builder, AgentCloneGitCommand: -c core.hooksPath=/dev/null, -c core.fsmonitor= and --no-ext-diff --no-textconv on diffs, with no network and no credential. The fsmonitor value is empty rather than "false" because git before 2.36 reads the key only as a program path and runs a PATH-resolved "false" on every index refresh. The hooks path is /dev/null rather than an empty value, which git resolves to the filesystem root. The -c values also reach the gc --auto a commit can start, so an agent that lowers gc.auto and re-enables the maintenance gc task (off by default since git 2.54) cannot run pre-auto-gc either. A repo filter.<driver>.clean still runs on add -A because git has no command-line switch for it. It runs at the agent's own uid with no secret and, under bubblewrap, with no egress. Global and system config stay in force for git-lfs and operator CA or proxy settings. The sandbox lane's floor counts the bubblewrap case that proves the egress is severed, and the lane requires that case to have passed, because a skipped case reads as green. The authenticated push and its ls-remote readback still run in the agent clone. Moving them to a platform-owned repository is a separate change.
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Summary
.gitcould therefore run code:pre-commitsilently lost the produced branch)core.hooksPathcore.fsmonitorprogramAgentCloneGitCommand(backend/src/CodeSpace.Core/Services/Agents/Workspace/AgentCloneGitCommand.cs). It adds-c core.hooksPath=/dev/null,-c core.fsmonitor=, and--no-ext-diff --no-textconvon diffs, and runs with no network and no credential.filter.<driver>.cleanstill runs onadd -A, because git has no switch for it. It runs at the agent's uid, with no secret and, under bubblewrap, no egress.Test plan
AgentCloneGitCommandTests; theLocalGitWorkspaceProviderTestsrouting Theory (every post-turn command in the clone is hardened, off the network, credential-free)AgentCloneGitHookIsolationFlowTests: 13 planted vectors stay silent under the hardened capture and commit, and a positive-control Theory shows each one fires when unhardened. Run on git 2.33.0, 2.50.1 and 2.56.0. The pre-auto-gc plant also setsmaintenance.gc.enabled=true: from git 2.54 auto maintenance uses the geometric strategy by default, which skips the gc task, so without that key the positive control never fired on CI's git 2.55.0.GitWorkspaceIsolationE2ETests.A_repo_clean_filter_runs_during_capture_with_its_egress_severedpasses and the lane reports ≥ 97 executed