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fix(agent): validate --id as a DNS label to stop /etc/hosts injection - #774
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Root cause: agent --id was only TrimSpace'd before being embedded into a
hostname (agentruntime.Hostname) and written to /etc/hosts via
dns.EnsureHostsEntries (sudo tee), with no newline/char filtering. A
newline in --id injects arbitrary /etc/hosts lines.
Fix (defense in depth):
1. hermes.Onboard and openclaw.Onboard now validate the resolved id with
the existing validate.Name DNS-label check (^[a-z0-9][a-z0-9-]{0,62}$)
before it is used to build deploymentDir/namespace/hostname, rejecting
ids with newlines, spaces, slashes, leading dashes, or empty/oversized
values.
2. dns.EnsureHostsEntries now skips any hostname that fails a new
isValidHostname DNS-charset check before it is written into the
/etc/hosts managed block, so a malformed hostname can never reach the
file even from a caller that bypasses Onboard's validation.
Confirmed Canary402 full-surface audit finding.
Claude-Session: https://claude.ai/code/session_014YjPMViNrZ7zBVgUQzwEKk
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Full-surface audit finding (HIGH): agent
--idinjects lines into root-owned/etc/hostsFound by the 2026-07-16 whole-product-surface audit (PR #770), adversarially confirmed.
obol agent new --id <value>passed the raw--id(onlyTrimSpaced) into a hostname string that is written to/etc/hostsviasudo tee(internal/dns/resolver.go) with no character filtering. An--idcontaining a newline injects arbitrary/etc/hostsentries (e.g. redirect a domain to an attacker IP). The same unvalidated--idalso flowed into filesystem paths and a recursive-delete target (the sibling MEDIUM finding) — both closed here.Fix (defense in depth)
--idis validated as a strict DNS label (^[a-z0-9]([-a-z0-9]*[a-z0-9])?$, bounded length) at theOnboardboundary (sharedvalidatehelper, used by both hermes and openclaw paths) — it becomes a hostname, so this is correct regardless of the injection./etc/hostswriter skips any hostname containing a non-DNS character, so no malformed value can reach the file even from another caller.Test: validator rejects newline/space/slash/leading-dash/empty ids, accepts normal ones; resolver skips a malformed hostname. Tests green.
https://claude.ai/code/session_014YjPMViNrZ7zBVgUQzwEKk