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Add --publish: the one ingress control

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Everything else in the file gates egress, which left an everyday request unanswered: the
agent starts a dev server inside the sandbox and a human wants to look at it. This puts a
listener on the host that forwards into the container, so a browser, curl or an API
tester reaches the server the sandboxed process runs.

`--publish [ADDR:]HOST:CONTAINER`, config `publish` and AISB_PUBLISH, repeatable, with the
cost named in the flag: it is ingress, so whatever that server serves is reachable from
the address it binds. The default address is 127.0.0.1 because a bare podman -p binds
every interface (measured) -- a port committed in a repo config must not quietly be a port
on the LAN. publish_addr changes the default machine-wide; a spec with a non-loopback
address warns on every run. The grammar is smaller than podman's on purpose: one port per
entry, no ranges, no /udp, no `*` -- this list is reviewed line by line, and typing
0.0.0.0 is the whole warning. An address means three parts, so `127.0.0.1:8000` is refused
rather than guessed. No -p alias: that flag belongs to the harness (claude -p prints).

Fail closed, as elsewhere: --net none cannot forward a port and podman discards the
mapping while starting the container anyway, so "it ran" would mean "nothing is
listening"; a host port already in use is named before the container starts, not after a
build; pick_port() will not hand the gate a port this run publishes. The container is
labelled with the ports it was given, and doctor reports them.

Inside, publish_rules() accepts tcp on the published ports in the input chain and never
the output one. Measured (docs/networking.md): pasta delivers the connection over
loopback, so that rule counts 0 packets on the reference host; it is there for a host or a
bridge network that delivers on the interface, and so that `nft list table inet aisb`
answers "what can reach this container". The ports are validated again inside the
entrypoint, because a ruleset is not somewhere to splice an unvalidated string. And the
measurement that makes a configured preview look broken: a server bound to 127.0.0.1
inside answers inside and refuses the published port outside, so dev servers must bind
0.0.0.0 -- both skills say so in the change that writes the port.

Tests. Unit: the grammar and every port list that looks right and is not, config/env/flag
precedence and dedup, the canonical spec in --print-policy, the `# ingress:` header, the
flags reaching the invocation before the image, egress enforcement byte-identical with a
port open, which chain the rule lands in and that a non-numeric port never reaches nft as
code. e2e (tests/e2e/13_publish.sh): one real container with enforce=nft where the host
gets its 200 and the same run still refuses a domain outside the allowlist at 403, the
server runs as uid 1000 with no capabilities so it cannot widen its own port, and the host
listener is gone when the container exits.

LLM-Generated: true
This commit is contained in:
ducoterra
2026-10-30 22:53:57 -04:00
parent ac2f310d10
commit 144e322391
21 changed files with 993 additions and 79 deletions
Download Patch File Download Diff File Expand all files Collapse all files
tests/unit/06_entrypoint.sh
+37 -2
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@@ -41,9 +41,21 @@ printf '::1 8080\n' > "$POL/direct6.list"
RULES="$AISB_STATE_DIR/rules.f"
# Render the ruleset by extracting the generator and feeding it the policy above.
# Render the ruleset the way the entrypoint would. publish_rules() is a function of its own
# in there, so it comes along: extracting only gen_rules() would ask a half-program to run.
render_rules() { # render_rules <AISB_PUBLISH_PORTS value> -> the ruleset on stdout
local g="$WORK/render.$$.sh"
{ awk '/^publish_rules\(\) \{/{f=1} f{print} f&&/^\}$/{exit}' "$EP"
awk '/^gen_rules\(\) \{/{f=1} f{print} f&&/^\}$/{exit}' "$EP"
printf 'POLICY_DIR=%q\nAISB_PROXY_IPS="100.64.0.1"\nAISB_PROXY_PORTS="18081"\nAISB_ALLOW_ICMP=1\nAISB_ALLOW_DNS=0\nAISB_PUBLISH_PORTS=%q\n' "$POL" "$1"
printf 'gen_rules\n'; } > "$g"
bash "$g" 2>"$WORK/render.err"
}
GEN="$WORK/gen.sh"
awk '/^gen_rules\(\) \{/{f=1} f{print} f&&/^\}$/{exit}' "$EP" > "$GEN"
{ printf 'POLICY_DIR=%q\nAISB_PROXY_IPS="100.64.0.1"\nAISB_PROXY_PORTS="18081"\nAISB_ALLOW_ICMP=1\nAISB_ALLOW_DNS=0\n' "$POL"
awk '/^publish_rules\(\) \{/{f=1} f{print} f&&/^\}$/{exit}' "$EP" > "$GEN"
awk '/^gen_rules\(\) \{/{f=1} f{print} f&&/^\}$/{exit}' "$EP" >> "$GEN"
{ printf 'POLICY_DIR=%q\nAISB_PROXY_IPS="100.64.0.1"\nAISB_PROXY_PORTS="18081"\nAISB_ALLOW_ICMP=1\nAISB_ALLOW_DNS=0\nAISB_PUBLISH_PORTS=""\n' "$POL"
printf 'gen_rules\n'; } >> "$GEN"
bash "$GEN" > "$RULES" 2>"$WORK/gen.err" && _ok "rules render" || _bad "rules render" "$(tail -3 "$WORK/gen.err")"
@@ -58,6 +70,29 @@ grep -q 'ip daddr 100.64.0.1 tcp dport 18081' "$RULES" && _ok "gate endpoi
grep -q 'aisb-est' "$RULES" && _ok "established traffic accepted" || _bad "established rule"
grep -c 'accept comment "aisb-direct"' "$RULES" | grep -qx 3 && _ok "exactly 3 direct rules" || _bad "direct rule count: $(grep -c 'aisb-direct' "$RULES")"
t_name "the published ports appear in the input chain, and nowhere else"
# Nothing published means no ingress rule at all: the ruleset must not open a port that was
# never asked for, and an empty set must not render an empty port list (nft refuses those).
PUBRULES="$(render_rules "8000 18080 8000")"
# Is a line matching <regex> present inside the named chain? An ingress rule in the output
# chain would be an egress hole, which is the one thing this feature must never become.
in_chain() { # in_chain <chain> <regex>
awk -v c="chain $1 {" -v re="$2" 'index($0, c){inside=1; next} /^ }/{inside=0}
inside && $0 ~ re {found=1} END{exit !found}' <<< "$PUBRULES"
}
printf '%s' "$PUBRULES" | grep -qF 'comment "aisb-publish"' && _ok "a rule names the published ports" || _bad "aisb-publish rule" "$(printf '%s' "$PUBRULES" | sed -n '/chain input/,/}/p')"
printf '%s' "$PUBRULES" | grep -qF 'tcp dport { 8000,18080 }' && _ok "both ports, de-duplicated" || _bad "port set" "$(printf '%s' "$PUBRULES" | grep aisb-publish)"
in_chain input 'aisb-publish' && _ok "the publish rule is in the input chain" || _bad "the publish rule is in the input chain"
in_chain output 'aisb-publish' && _bad "the publish rule is also an egress hole" || _ok "publishing opens no egress path"
in_chain input 'policy drop' && _ok "input still defaults to drop with a port open" || _bad "input policy drop survived"
printf '%s' "$PUBRULES" | grep -qF 'aisb-default-drop' && _ok "the egress default-drop is untouched" || _bad "default-drop rule"
# The policy file is host-written and mounted read-only, but a ruleset is not somewhere to
# splice an unvalidated string: anything that is not a port is dropped on the floor.
BADRULES="$(render_rules '8000 nft delete table inet aisb accept')"
printf '%s' "$BADRULES" | grep -qF 'delete table' && _bad "a port value reached the ruleset as code" || _ok "a non-numeric port never reaches the ruleset"
printf '%s' "$BADRULES" | grep -qF 'tcp dport { 8000 }' && _ok " ... and the valid port in it still lands" || _bad "valid port kept" "$(printf '%s' "$BADRULES" | grep aisb-publish)"
render_rules '' | grep -qF 'aisb-publish' && _bad "a rule appeared with nothing published" || _ok "no publish rule when nothing is published"
t_name "no DNS hole when the gate is in front"
grep -E 'th dport 53' "$RULES" >/dev/null && _bad "DNS is closed in gate mode" || _ok "DNS is closed in gate mode"