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

1 files changed, 40 insertions, 18 deletions

diff --git a/sbin/hastd/subr.c b/sbin/hastd/subr.c
index ea84e2a..29f33e7 100644
--- a/sbin/hastd/subr.c
+++ b/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);
 }