Merge #265: state the member trust model at startup (#184)

fleetd/src/main/java/dev/ltms/fleet/Fleetd.java

@@ -121,6 +121,7 @@ public final class Fleetd {
         // else can fail on a silently-empty one. A daemon started without a login shell (launchd)
         // boots fine either way — this is the only thing that says so out loud.
         reportRequiredSecrets(cfg);
+        reportMemberTrustModel(cfg);
         // CB-596: an absent (or empty) memberCredentials: block blocks NOTHING — no credential
         // name is hardcoded any more to fall back on. Say so loudly, the same way a missing
         // secret is reported above, so upgrading past this commit never silently drops CB-592's
@@ -1136,6 +1137,24 @@ public final class Fleetd {
         });
     }
 
+    /**
+     * fleetd #184: state the member trust model at startup. Environment controls and worktrees do
+     * not make a sandbox when fleetd and its members use the same OS user. A separate herdr may
+     * provide that boundary, but fleetd cannot inspect the uid at the other end of its socket.
+     */
+    static void reportMemberTrustModel(FleetConfig cfg) {
+        if (cfg.memberHerdrSocket() != null && !cfg.memberHerdrSocket().isBlank()) {
+            log.info("member trust model: members are routed to a separate herdr through "
+                    + "memberHerdrSocket. fleetd cannot see that herdr's uid, so confirm it runs "
+                    + "as a different OS user before treating it as a boundary.");
+            return;
+        }
+        log.info("member trust model: members run as the same OS user as fleetd, not in a sandbox. "
+                + "A member can read any file this user can read, including SSH keys and credential "
+                + "stores, whatever memberCredentials says. To add a real boundary, route members to "
+                + "a second herdr under a different OS user with memberHerdrSocket.");
+    }
+
     /**
      * CB-596: {@code known:} empty (block absent entirely, or present but empty) means {@link
      * FleetConfig.MemberCredentials#blockedSet()} is empty too — every member pane inherits the

fleetd/src/test/java/dev/ltms/fleet/MemberTrustModelReportTest.java

@@ -0,0 +1,73 @@
+package dev.ltms.fleet;
+
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.read.ListAppender;
+import dev.ltms.fleet.config.FleetConfig;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.slf4j.LoggerFactory;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * fleetd #184: startup must state whether members share fleetd's OS user or use a separate herdr.
+ */
+class MemberTrustModelReportTest {
+
+    private static FleetConfig load(Path dir, String yaml) throws Exception {
+        Path f = dir.resolve("fleetd.yaml");
+        Files.writeString(f, yaml);
+        return FleetConfig.load(f);
+    }
+
+    private static ListAppender<ILoggingEvent> attach() {
+        Logger logger = (Logger) LoggerFactory.getLogger(Fleetd.class);
+        ListAppender<ILoggingEvent> appender = new ListAppender<>();
+        appender.start();
+        logger.addAppender(appender);
+        return appender;
+    }
+
+    private static void detach(ListAppender<ILoggingEvent> appender) {
+        ((Logger) LoggerFactory.getLogger(Fleetd.class)).detachAppender(appender);
+    }
+
+    private static String report(FleetConfig cfg) {
+        Logger logger = (Logger) LoggerFactory.getLogger(Fleetd.class);
+        ch.qos.logback.classic.Level original = logger.getLevel();
+        logger.setLevel(ch.qos.logback.classic.Level.INFO);
+        ListAppender<ILoggingEvent> appender = attach();
+        try {
+            Fleetd.reportMemberTrustModel(cfg);
+        } finally {
+            detach(appender);
+            logger.setLevel(original);
+        }
+        return appender.list.getFirst().getFormattedMessage();
+    }
+
+    @Test
+    void unsetMemberHerdrSocketStatesThatMembersAreNotSandboxed(@TempDir Path dir) throws Exception {
+        FleetConfig cfg = load(dir, "bind:\n  host: 127.0.0.1\n  port: 8765\n");
+
+        assertEquals("member trust model: members run as the same OS user as fleetd, not in a sandbox. "
+                        + "A member can read any file this user can read, including SSH keys and credential "
+                        + "stores, whatever memberCredentials says. To add a real boundary, route members to "
+                        + "a second herdr under a different OS user with memberHerdrSocket.",
+                report(cfg));
+    }
+
+    @Test
+    void configuredMemberHerdrSocketStatesThatFleetdCannotConfirmTheBoundary(@TempDir Path dir) throws Exception {
+        FleetConfig cfg = load(dir, "memberHerdrSocket: /tmp/member-herdr.sock\n");
+
+        assertEquals("member trust model: members are routed to a separate herdr through "
+                        + "memberHerdrSocket. fleetd cannot see that herdr's uid, so confirm it runs "
+                        + "as a different OS user before treating it as a boundary.",
+                report(cfg));
+    }
+}