Currently we are unable to use capsicum for the primary worker process,

because we need to do ioctl(2)s, which are not permitted in the capability
mode. What we do now is to chroot(2) to /var/empty, which restricts access
to file system name space and we drop privileges to hast user and hast
group.

This still allows to access to other name spaces, like list of processes,
network and sysvipc.

To address that, use jail(2) instead of chroot(2). Using jail(2) will restrict
access to process table, network (we use ip-less jails) and sysvipc (if
security.jail.sysvipc_allowed is turned off). This provides much better
separation.

MFC after:	1 week

sbin/hastctl/hastctl.c

@@ -480,7 +480,7 @@ main(int argc, char *argv[])
 		    cfg->hc_controladdr);
 	}
 
-	if (drop_privs(true) != 0)
+	if (drop_privs(NULL) != 0)
 		exit(EX_CONFIG);
 
 	/* Send the command to the server... */

sbin/hastd/primary.c

@@ -904,7 +904,7 @@ hastd_primary(struct hast_resource *res)
 	init_ggate(res);
 	init_environment(res);
 
-	if (drop_privs(true) != 0) {
+	if (drop_privs(res) != 0) {
 		cleanup(res);
 		exit(EX_CONFIG);
 	}

sbin/hastd/secondary.c

@@ -436,7 +436,7 @@ hastd_secondary(struct hast_resource *res, struct nv *nvin)
 	init_local(res);
 	init_environment();
 
-	if (drop_privs(true) != 0)
+	if (drop_privs(res) != 0)
 		exit(EX_CONFIG);
 	pjdlog_info("Privileges successfully dropped.");
 

sbin/hastd/subr.c

@@ -32,9 +32,10 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/capability.h>
-#include <sys/types.h>
+#include <sys/param.h>
 #include <sys/disk.h>
 #include <sys/ioctl.h>
+#include <sys/jail.h>
 #include <sys/stat.h>
 
 #include <errno.h>
@@ -147,13 +148,15 @@ role2str(int role)
 }
 
 int
-drop_privs(bool usecapsicum)
+drop_privs(struct hast_resource *res)
 {
+	char jailhost[sizeof(res->hr_name) * 2];
+	struct jail jailst;
 	struct passwd *pw;
 	uid_t ruid, euid, suid;
 	gid_t rgid, egid, sgid;
 	gid_t gidset[1];
-	bool capsicum;
+	bool capsicum, jailed;
 
 	/*
 	 * According to getpwnam(3) we have to clear errno before calling the
@@ -173,10 +176,34 @@ drop_privs(bool usecapsicum)
 			return (-1);
 		}
 	}
-	if (chroot(pw->pw_dir) == -1) {
-		KEEP_ERRNO(pjdlog_errno(LOG_ERR,
-		    "Unable to change root directory to %s", pw->pw_dir));
-		return (-1);
+
+	bzero(&jailst, sizeof(jailst));
+	jailst.version = JAIL_API_VERSION;
+	jailst.path = pw->pw_dir;
+	if (res == NULL) {
+		(void)snprintf(jailhost, sizeof(jailhost), "hastctl");
+	} else {
+		(void)snprintf(jailhost, sizeof(jailhost), "hastd: %s (%s)",
+		    res->hr_name, role2str(res->hr_role));
+	}
+	jailst.hostname = jailhost;
+	jailst.jailname = NULL;
+	jailst.ip4s = 0;
+	jailst.ip4 = NULL;
+	jailst.ip6s = 0;
+	jailst.ip6 = NULL;
+	if (jail(&jailst) >= 0) {
+		jailed = true;
+	} else {
+		jailed = false;
+		pjdlog_errno(LOG_WARNING,
+		    "Unable to jail to directory to %s", pw->pw_dir);
+		if (chroot(pw->pw_dir) == -1) {
+			KEEP_ERRNO(pjdlog_errno(LOG_ERR,
+			    "Unable to change root directory to %s",
+			    pw->pw_dir));
+			return (-1);
+		}
 	}
 	PJDLOG_VERIFY(chdir("/") == 0);
 	gidset[0] = pw->pw_gid;
@@ -197,15 +224,10 @@ drop_privs(bool usecapsicum)
 		return (-1);
 	}
 
-	capsicum = false;
-	if (usecapsicum) {
-		if (cap_enter() == 0) {
-			capsicum = true;
-		} else {
-			pjdlog_errno(LOG_WARNING,
-			    "Unable to sandbox using capsicum");
-		}
-	}
+	if (res == NULL || res->hr_role != HAST_ROLE_PRIMARY)
+		capsicum = (cap_enter() == 0);
+	else
+		capsicum = false;
 
 	/*
 	 * Better be sure that everything succeeded.
@@ -223,8 +245,8 @@ drop_privs(bool usecapsicum)
 	PJDLOG_VERIFY(gidset[0] == pw->pw_gid);
 
 	pjdlog_debug(1,
-	    "Privileges successfully dropped using %schroot+setgid+setuid.",
-	    capsicum ? "capsicum+" : "");
+	    "Privileges successfully dropped using %s%s+setgid+setuid.",
+	    capsicum ? "capsicum+" : "", jailed ? "jail" : "chroot");
 
 	return (0);
 }

sbin/hastd/subr.h

@@ -51,6 +51,6 @@ int snprlcat(char *str, size_t size, const char *fmt, ...);
 
 int provinfo(struct hast_resource *res, bool dowrite);
 const char *role2str(int role);
-int drop_privs(bool usecapsicum);
+int drop_privs(struct hast_resource *res);
 
 #endif	/* !_SUBR_H_ */