runsc/fsgofer/filter: add Rules() for composable seccomp filters#12904
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runsc/fsgofer/filter: add Rules() for composable seccomp filters#12904copybara-service[bot] wants to merge 1 commit intomasterfrom
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Today `runsc/fsgofer/filter` exports only `Install(opt Options) error`, which builds and installs the seccomp program in one shot with no way to compose additional rules. I am looking into building a custom gofer over LisaFS that needs a small number of extra syscalls such as outbound TCP and `setns(CLONE_NEWNET)` for namespace switching but otherwise wants the stock seccomp baseline. The only option today is to fork `config.go` and its arch-specific files and manually track upstream changes, which is a security concern because if upstream tightens a rule forks silently diverge and may run with a wider-than-intended syscall surface.
This change adds `Rules(opt Options) seccomp.SyscallRules`, which returns the merged baseline without installing it so custom gofers can compose their own rules on top.
rules := filter.Rules(opts)
rules.Merge(myNetworkingRules)
// build and install seccomp program with the merged rules
`Install()` now delegates to `Rules()` internally. The implementation uses `allowedSyscalls.Copy()` to deep-copy the package-level rules before merging, which also fixes a latent issue where calling `Install` more than once would double-merge rules through the shared underlying map.
FUTURE_COPYBARA_INTEGRATE_REVIEW=#12903 from shayonj:s/composable-seccomp c0b4b74
PiperOrigin-RevId: 897168280
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runsc/fsgofer/filter: add Rules() for composable seccomp filters
Today
runsc/fsgofer/filterexports onlyInstall(opt Options) error, which builds and installs the seccomp program in one shot with no way to compose additional rules. I am looking into building a custom gofer over LisaFS that needs a small number of extra syscalls such as outbound TCP andsetns(CLONE_NEWNET)for namespace switching but otherwise wants the stock seccomp baseline. The only option today is to forkconfig.goand its arch-specific files and manually track upstream changes, which is a security concern because if upstream tightens a rule forks silently diverge and may run with a wider-than-intended syscall surface.This change adds
Rules(opt Options) seccomp.SyscallRules, which returns the merged baseline without installing it so custom gofers can compose their own rules on top.Install()now delegates toRules()internally. The implementation usesallowedSyscalls.Copy()to deep-copy the package-level rules before merging, which also fixes a latent issue where callingInstallmore than once would double-merge rules through the shared underlying map.FUTURE_COPYBARA_INTEGRATE_REVIEW=#12903 from shayonj:s/composable-seccomp c0b4b74