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[83.57.172.113]) by smtp.gmail.com with ESMTPSA id t131sm4707925wmb.13.2020.01.21.07.54.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Jan 2020 07:54:42 -0800 (PST) Subject: Re: [PATCH v2 051/109] virtiofsd: add seccomp whitelist To: "Dr. David Alan Gilbert (git)" , qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com, berrange@redhat.com, slp@redhat.com References: <20200121122433.50803-1-dgilbert@redhat.com> <20200121122433.50803-52-dgilbert@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: Date: Tue, 21 Jan 2020 16:54:41 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20200121122433.50803-52-dgilbert@redhat.com> Content-Language: en-US X-MC-Unique: 5v99KJzZO2yT_z2xtVpMaA-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: m.mizuma@jp.fujitsu.com, misono.tomohiro@jp.fujitsu.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 1/21/20 1:23 PM, Dr. David Alan Gilbert (git) wrote: > From: Stefan Hajnoczi > > Only allow system calls that are needed by virtiofsd. All other system > calls cause SIGSYS to be directed at the thread and the process will > coredump. > > Restricting system calls reduces the kernel attack surface and limits > what the process can do when compromised. > > Signed-off-by: Stefan Hajnoczi > with additional entries by: > Signed-off-by: Ganesh Maharaj Mahalingam > Signed-off-by: Masayoshi Mizuma > Signed-off-by: Misono Tomohiro > Signed-off-by: piaojun > Signed-off-by: Vivek Goyal > Signed-off-by: Eric Ren > Signed-off-by: Dr. David Alan Gilbert > --- > Makefile | 2 +- > tools/virtiofsd/Makefile.objs | 5 +- > tools/virtiofsd/passthrough_ll.c | 2 + > tools/virtiofsd/seccomp.c | 150 +++++++++++++++++++++++++++++++ > tools/virtiofsd/seccomp.h | 14 +++ > 5 files changed, 171 insertions(+), 2 deletions(-) > create mode 100644 tools/virtiofsd/seccomp.c > create mode 100644 tools/virtiofsd/seccomp.h > > diff --git a/Makefile b/Makefile > index a87e06ad93..967d59c98a 100644 > --- a/Makefile > +++ b/Makefile > @@ -327,7 +327,7 @@ HELPERS-y += vhost-user-gpu$(EXESUF) > vhost-user-json-y += contrib/vhost-user-gpu/50-qemu-gpu.json > endif > > -ifdef CONFIG_LINUX > +ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP),yy) > HELPERS-y += virtiofsd$(EXESUF) Something is weird here, because I got: $ make virtiofsd ... CC tools/virtiofsd/seccomp.o tools/virtiofsd/seccomp.c:14:21: fatal error: seccomp.h: No such file or directory #include ^ Indeed I don't have libseccomp installed, ./configure reported: ... QGA MSI support no seccomp support no coroutine backend ucontext coroutine pool yes debug stack usage no ... Note also: $ make print-CONFIG_LINUX CONFIG_LINUX=y $ make print-CONFIG_SECCOMP CONFIG_SECCOMP= $ make print-CONFIG_LIBCAP_NG CONFIG_LIBCAP_NG=y $ make print-HELPERS-y HELPERS-y=qemu-bridge-helper > vhost-user-json-y += tools/virtiofsd/50-qemu-virtiofsd.json > endif > diff --git a/tools/virtiofsd/Makefile.objs b/tools/virtiofsd/Makefile.objs > index 45a807500d..076f667e46 100644 > --- a/tools/virtiofsd/Makefile.objs > +++ b/tools/virtiofsd/Makefile.objs > @@ -5,5 +5,8 @@ virtiofsd-obj-y = buffer.o \ > fuse_signals.o \ > fuse_virtio.o \ > helper.o \ > - passthrough_ll.o > + passthrough_ll.o \ > + seccomp.o > > +seccomp.o-cflags := $(SECCOMP_CFLAGS) > +seccomp.o-libs := $(SECCOMP_LIBS) > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index 752beb459a..8748e64f33 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -58,6 +58,7 @@ > #include > > #include "passthrough_helpers.h" > +#include "seccomp.h" > > struct lo_map_elem { > union { > @@ -2090,6 +2091,7 @@ static void setup_sandbox(struct lo_data *lo, struct fuse_session *se) > { > setup_namespaces(lo, se); > setup_mounts(lo->source); > + setup_seccomp(); > } > > int main(int argc, char *argv[]) > diff --git a/tools/virtiofsd/seccomp.c b/tools/virtiofsd/seccomp.c > new file mode 100644 > index 0000000000..2aa4d3cc66 > --- /dev/null > +++ b/tools/virtiofsd/seccomp.c > @@ -0,0 +1,150 @@ > +/* > + * Seccomp sandboxing for virtiofsd > + * > + * Copyright (C) 2019 Red Hat, Inc. > + * > + * SPDX-License-Identifier: GPL-2.0-or-later > + */ > + > +#include "seccomp.h" > +#include "fuse_i.h" > +#include "fuse_log.h" > +#include > +#include > +#include > +#include > + > +/* Bodge for libseccomp 2.4.2 which broke ppoll */ > +#if !defined(__SNR_ppoll) && defined(__SNR_brk) > +#ifdef __NR_ppoll > +#define __SNR_ppoll __NR_ppoll > +#else > +#define __SNR_ppoll __PNR_ppoll > +#endif > +#endif > + > +static const int syscall_whitelist[] = { > + /* TODO ireg sem*() syscalls */ > + SCMP_SYS(brk), > + SCMP_SYS(capget), /* For CAP_FSETID */ > + SCMP_SYS(capset), > + SCMP_SYS(clock_gettime), > + SCMP_SYS(clone), > +#ifdef __NR_clone3 > + SCMP_SYS(clone3), > +#endif > + SCMP_SYS(close), > + SCMP_SYS(copy_file_range), > + SCMP_SYS(dup), > + SCMP_SYS(eventfd2), > + SCMP_SYS(exit), > + SCMP_SYS(exit_group), > + SCMP_SYS(fallocate), > + SCMP_SYS(fchmodat), > + SCMP_SYS(fchownat), > + SCMP_SYS(fcntl), > + SCMP_SYS(fdatasync), > + SCMP_SYS(fgetxattr), > + SCMP_SYS(flistxattr), > + SCMP_SYS(flock), > + SCMP_SYS(fremovexattr), > + SCMP_SYS(fsetxattr), > + SCMP_SYS(fstat), > + SCMP_SYS(fstatfs), > + SCMP_SYS(fsync), > + SCMP_SYS(ftruncate), > + SCMP_SYS(futex), > + SCMP_SYS(getdents), > + SCMP_SYS(getdents64), > + SCMP_SYS(getegid), > + SCMP_SYS(geteuid), > + SCMP_SYS(getpid), > + SCMP_SYS(gettid), > + SCMP_SYS(gettimeofday), > + SCMP_SYS(linkat), > + SCMP_SYS(lseek), > + SCMP_SYS(madvise), > + SCMP_SYS(mkdirat), > + SCMP_SYS(mknodat), > + SCMP_SYS(mmap), > + SCMP_SYS(mprotect), > + SCMP_SYS(mremap), > + SCMP_SYS(munmap), > + SCMP_SYS(newfstatat), > + SCMP_SYS(open), > + SCMP_SYS(openat), > + SCMP_SYS(ppoll), > + SCMP_SYS(prctl), /* TODO restrict to just PR_SET_NAME? */ > + SCMP_SYS(preadv), > + SCMP_SYS(pread64), > + SCMP_SYS(pwritev), > + SCMP_SYS(pwrite64), > + SCMP_SYS(read), > + SCMP_SYS(readlinkat), > + SCMP_SYS(recvmsg), > + SCMP_SYS(renameat), > + SCMP_SYS(renameat2), > + SCMP_SYS(rt_sigaction), > + SCMP_SYS(rt_sigprocmask), > + SCMP_SYS(rt_sigreturn), > + SCMP_SYS(sendmsg), > + SCMP_SYS(setresgid), > + SCMP_SYS(setresuid), > +#ifdef __NR_setresgid32 > + SCMP_SYS(setresgid32), > +#endif > +#ifdef __NR_setresuid32 > + SCMP_SYS(setresuid32), > +#endif > + SCMP_SYS(set_robust_list), > + SCMP_SYS(symlinkat), > + SCMP_SYS(time), /* Rarely needed, except on static builds */ > + SCMP_SYS(tgkill), > + SCMP_SYS(unlinkat), > + SCMP_SYS(utimensat), > + SCMP_SYS(write), > + SCMP_SYS(writev), > +}; > + > +void setup_seccomp(void) > +{ > + scmp_filter_ctx ctx; > + size_t i; > + > +#ifdef SCMP_ACT_KILL_PROCESS > + ctx = seccomp_init(SCMP_ACT_KILL_PROCESS); > + /* Handle a newer libseccomp but an older kernel */ > + if (!ctx && errno == EOPNOTSUPP) { > + ctx = seccomp_init(SCMP_ACT_TRAP); > + } > +#else > + ctx = seccomp_init(SCMP_ACT_TRAP); > +#endif > + if (!ctx) { > + fuse_log(FUSE_LOG_ERR, "seccomp_init() failed\n"); > + exit(1); > + } > + > + for (i = 0; i < G_N_ELEMENTS(syscall_whitelist); i++) { > + if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, > + syscall_whitelist[i], 0) != 0) { > + fuse_log(FUSE_LOG_ERR, "seccomp_rule_add syscall %d", > + syscall_whitelist[i]); > + exit(1); > + } > + } > + > + /* libvhost-user calls this for post-copy migration, we don't need it */ > + if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(ENOSYS), > + SCMP_SYS(userfaultfd), 0) != 0) { > + fuse_log(FUSE_LOG_ERR, "seccomp_rule_add userfaultfd failed\n"); > + exit(1); > + } > + > + if (seccomp_load(ctx) < 0) { > + fuse_log(FUSE_LOG_ERR, "seccomp_load() failed\n"); > + exit(1); > + } > + > + seccomp_release(ctx); > +} > diff --git a/tools/virtiofsd/seccomp.h b/tools/virtiofsd/seccomp.h > new file mode 100644 > index 0000000000..86bce72652 > --- /dev/null > +++ b/tools/virtiofsd/seccomp.h > @@ -0,0 +1,14 @@ > +/* > + * Seccomp sandboxing for virtiofsd > + * > + * Copyright (C) 2019 Red Hat, Inc. > + * > + * SPDX-License-Identifier: GPL-2.0-or-later > + */ > + > +#ifndef VIRTIOFSD_SECCOMP_H > +#define VIRTIOFSD_SECCOMP_H > + > +void setup_seccomp(void); > + > +#endif /* VIRTIOFSD_SECCOMP_H */ >