From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40892) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dqFy1-0006sY-Ch for qemu-devel@nongnu.org; Fri, 08 Sep 2017 05:52:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dqFxw-0001xU-9s for qemu-devel@nongnu.org; Fri, 08 Sep 2017 05:52:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59284) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dqFxv-0001wp-W6 for qemu-devel@nongnu.org; Fri, 08 Sep 2017 05:52:48 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id EFB355F73C for ; Fri, 8 Sep 2017 09:52:46 +0000 (UTC) References: <20170908091027.9104-1-otubo@redhat.com> <20170908091027.9104-2-otubo@redhat.com> <20170908095020.GC16888@vader> From: Thomas Huth Message-ID: <36e21758-2a47-d6b9-1141-67470e30754f@redhat.com> Date: Fri, 8 Sep 2017 11:52:42 +0200 MIME-Version: 1.0 In-Reply-To: <20170908095020.GC16888@vader> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCHv5 1/5] seccomp: changing from whitelist to blacklist List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Otubo Cc: qemu-devel@nongnu.org On 08.09.2017 11:50, Eduardo Otubo wrote: > On Fri, Sep 08, 2017 at 11:43:27AM +0200, Thomas Huth wrote: >> On 08.09.2017 11:10, Eduardo Otubo wrote: >>> This patch changes the default behavior of the seccomp filter from >>> whitelist to blacklist. By default now all system calls are allowed and >>> a small black list of definitely forbidden ones was created. >>> >>> Signed-off-by: Eduardo Otubo >>> --- >>> include/sysemu/seccomp.h | 2 + >>> qemu-seccomp.c | 264 ++++++----------------------------------------- >>> vl.c | 1 - >>> 3 files changed, 35 insertions(+), 232 deletions(-) >>> >>> diff --git a/include/sysemu/seccomp.h b/include/sysemu/seccomp.h >>> index cfc06008cb..23b9c3c789 100644 >>> --- a/include/sysemu/seccomp.h >>> +++ b/include/sysemu/seccomp.h >>> @@ -15,6 +15,8 @@ >>> #ifndef QEMU_SECCOMP_H >>> #define QEMU_SECCOMP_H >>> >>> +#define QEMU_SECCOMP_SET_DEFAULT (1 << 0) >>> + >>> #include >>> >>> int seccomp_start(void); >>> diff --git a/qemu-seccomp.c b/qemu-seccomp.c >>> index df75d9c471..bc9a1f77ff 100644 >>> --- a/qemu-seccomp.c >>> +++ b/qemu-seccomp.c >>> @@ -28,232 +28,34 @@ >>> >>> struct QemuSeccompSyscall { >>> int32_t num; >>> - uint8_t priority; >>> + int type; >> >> What's this "type" field good for? I failed to spot the place in the >> sources where you are using it...? Anyway, some comments here right >> after the struct members would be useful. > > The type is exactly the type of the system call on the blacklist array > below. Being QEMU_SECCOMP_SET_DEFAULT, QEMU_SECCOMP_SET_OBSOLETE, etc. Sorry, I still do not understand. If that's the case, what's the difference between the "type" field and the "set" field? Where do you use the "type" field? Thomas >>> + uint8_t set; >>> }; >>> >>> -static const struct QemuSeccompSyscall seccomp_whitelist[] = { >>> - { SCMP_SYS(timer_settime), 255 }, >> [...] >>> - { SCMP_SYS(memfd_create), 240 }, >>> -#ifdef HAVE_CACHEFLUSH >>> - { SCMP_SYS(cacheflush), 240 }, >>> -#endif >>> - { SCMP_SYS(sysinfo), 240 }, >>> +static const struct QemuSeccompSyscall blacklist[] = { >>> + /* default set of syscalls to blacklist */ >>> + { SCMP_SYS(reboot), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(swapon), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(swapoff), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(syslog), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(mount), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(umount), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(kexec_load), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(afs_syscall), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(break), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(ftime), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(getpmsg), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(gtty), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(lock), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(mpx), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(prof), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(profil), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(putpmsg), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(security), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(stty), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(tuxcall), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(ulimit), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> + { SCMP_SYS(vserver), 1, QEMU_SECCOMP_SET_DEFAULT }, >>> }; >>> >>> int seccomp_start(void) >>> @@ -262,19 +64,19 @@ int seccomp_start(void) >>> unsigned int i = 0; >>> scmp_filter_ctx ctx; >>> >>> - ctx = seccomp_init(SCMP_ACT_KILL); >>> + ctx = seccomp_init(SCMP_ACT_ALLOW); >>> if (ctx == NULL) { >>> rc = -1; >>> goto seccomp_return; >>> } >>> >>> - for (i = 0; i < ARRAY_SIZE(seccomp_whitelist); i++) { >>> - rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, seccomp_whitelist[i].num, 0); >>> - if (rc < 0) { >>> - goto seccomp_return; >>> + for (i = 0; i < ARRAY_SIZE(blacklist); i++) { >>> + switch (blacklist[i].set) { >>> + default: >>> + break; >>> } >>> - rc = seccomp_syscall_priority(ctx, seccomp_whitelist[i].num, >>> - seccomp_whitelist[i].priority); >>> + >>> + rc = seccomp_rule_add(ctx, SCMP_ACT_KILL, blacklist[i].num, 0); >>> if (rc < 0) { >>> goto seccomp_return; >>> } >>> diff --git a/vl.c b/vl.c >>> index fb1f05b937..76e0b3a946 100644 >>> --- a/vl.c >>> +++ b/vl.c >>> @@ -1032,7 +1032,6 @@ static int bt_parse(const char *opt) >>> >>> static int parse_sandbox(void *opaque, QemuOpts *opts, Error **errp) >>> { >>> - /* FIXME: change this to true for 1.3 */ >>> if (qemu_opt_get_bool(opts, "enable", false)) { >>> #ifdef CONFIG_SECCOMP >>> if (seccomp_start() < 0) { >>> >> >> >