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nspawn: lock down system call filter a bit

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Let's block access to the kernel keyring and a number of obsolete system calls.
Also, update list of syscalls that may alter the system clock, and do raw IO
access. Filter ptrace() if CAP_SYS_PTRACE is not passed to the container and
acct() if CAP_SYS_PACCT is not passed.

This also changes things so that kexec(), some profiling calls, the swap calls
and quotactl() is never available to containers, not even if CAP_SYS_ADMIN is
passed. After all we currently permit CAP_SYS_ADMIN to containers by default,
but these calls should not be available, even then.
This commit is contained in:
Lennart Poettering 2016-06-10 18:04:02 +02:00
parent 4e069746fe
commit 54a17e01de
1 changed files with 67 additions and 11 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

78
src/nspawn/nspawn-seccomp.c
View file

@ -44,20 +44,76 @@ static int seccomp_add_default_syscall_filter(scmp_filter_ctx ctx,
uint64_t capability;
int syscall_num;
} blacklist[] = {
{ CAP_SYS_RAWIO, SCMP_SYS(iopl) },
{ CAP_SYS_RAWIO, SCMP_SYS(ioperm) },
{ CAP_SYS_BOOT, SCMP_SYS(kexec_load) },
{ CAP_SYS_ADMIN, SCMP_SYS(swapon) },
{ CAP_SYS_ADMIN, SCMP_SYS(swapoff) },
{ CAP_SYS_ADMIN, SCMP_SYS(open_by_handle_at) },
{ CAP_SYS_MODULE, SCMP_SYS(init_module) },
{ CAP_SYS_MODULE, SCMP_SYS(finit_module) },
{ CAP_SYS_MODULE, SCMP_SYS(delete_module) },
{ CAP_SYSLOG, SCMP_SYS(syslog) },
{ 0, SCMP_SYS(_sysctl) }, /* obsolete syscall */
{ 0, SCMP_SYS(add_key) }, /* keyring is not namespaced */
{ 0, SCMP_SYS(afs_syscall) }, /* obsolete syscall */
{ 0, SCMP_SYS(bdflush) },
#ifdef __NR_bpf
{ 0, SCMP_SYS(bpf) },
#endif
{ 0, SCMP_SYS(break) }, /* obsolete syscall */
{ 0, SCMP_SYS(create_module) }, /* obsolete syscall */
{ 0, SCMP_SYS(ftime) }, /* obsolete syscall */
{ 0, SCMP_SYS(get_kernel_syms) }, /* obsolete syscall */
{ 0, SCMP_SYS(getpmsg) }, /* obsolete syscall */
{ 0, SCMP_SYS(gtty) }, /* obsolete syscall */
#ifdef __NR_kexec_file_load
{ 0, SCMP_SYS(kexec_file_load) },
#endif
{ 0, SCMP_SYS(kexec_load) },
{ 0, SCMP_SYS(keyctl) }, /* keyring is not namespaced */
{ 0, SCMP_SYS(lock) }, /* obsolete syscall */
{ 0, SCMP_SYS(lookup_dcookie) },
{ 0, SCMP_SYS(mpx) }, /* obsolete syscall */
{ 0, SCMP_SYS(nfsservctl) }, /* obsolete syscall */
{ 0, SCMP_SYS(open_by_handle_at) },
{ 0, SCMP_SYS(perf_event_open) },
{ 0, SCMP_SYS(prof) }, /* obsolete syscall */
{ 0, SCMP_SYS(profil) }, /* obsolete syscall */
{ 0, SCMP_SYS(putpmsg) }, /* obsolete syscall */
{ 0, SCMP_SYS(query_module) }, /* obsolete syscall */
{ 0, SCMP_SYS(quotactl) },
{ 0, SCMP_SYS(request_key) }, /* keyring is not namespaced */
{ 0, SCMP_SYS(security) }, /* obsolete syscall */
{ 0, SCMP_SYS(sgetmask) }, /* obsolete syscall */
{ 0, SCMP_SYS(ssetmask) }, /* obsolete syscall */
{ 0, SCMP_SYS(stty) }, /* obsolete syscall */
{ 0, SCMP_SYS(swapoff) },
{ 0, SCMP_SYS(swapon) },
{ 0, SCMP_SYS(sysfs) }, /* obsolete syscall */
{ 0, SCMP_SYS(tuxcall) }, /* obsolete syscall */
{ 0, SCMP_SYS(ulimit) }, /* obsolete syscall */
{ 0, SCMP_SYS(uselib) }, /* obsolete syscall */
{ 0, SCMP_SYS(ustat) }, /* obsolete syscall */
{ 0, SCMP_SYS(vserver) }, /* obsolete syscall */
{ CAP_SYSLOG, SCMP_SYS(syslog) },
{ CAP_SYS_MODULE, SCMP_SYS(delete_module) },
{ CAP_SYS_MODULE, SCMP_SYS(finit_module) },
{ CAP_SYS_MODULE, SCMP_SYS(init_module) },
{ CAP_SYS_PACCT, SCMP_SYS(acct) },
{ CAP_SYS_PTRACE, SCMP_SYS(process_vm_readv) },
{ CAP_SYS_PTRACE, SCMP_SYS(process_vm_writev) },
{ CAP_SYS_PTRACE, SCMP_SYS(ptrace) },
{ CAP_SYS_RAWIO, SCMP_SYS(ioperm) },
{ CAP_SYS_RAWIO, SCMP_SYS(iopl) },
{ CAP_SYS_RAWIO, SCMP_SYS(pciconfig_iobase) },
{ CAP_SYS_RAWIO, SCMP_SYS(pciconfig_read) },
{ CAP_SYS_RAWIO, SCMP_SYS(pciconfig_write) },
#ifdef __NR_s390_pci_mmio_read
{ CAP_SYS_RAWIO, SCMP_SYS(s390_pci_mmio_read) },
#endif
#ifdef __NR_s390_pci_mmio_write
{ CAP_SYS_RAWIO, SCMP_SYS(s390_pci_mmio_write) },
#endif
{ CAP_SYS_TIME, SCMP_SYS(adjtimex) },
{ CAP_SYS_TIME, SCMP_SYS(clock_adjtime) },
{ CAP_SYS_TIME, SCMP_SYS(clock_settime) },
{ CAP_SYS_TIME, SCMP_SYS(settimeofday) },
{ CAP_SYS_TIME, SCMP_SYS(stime) },
};
for (i = 0; i < ELEMENTSOF(blacklist); i++) {
if (cap_list_retain & (1ULL << blacklist[i].capability))
if (blacklist[i].capability != 0 && (cap_list_retain & (1ULL << blacklist[i].capability)))
continue;
r = seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), blacklist[i].syscall_num, 0);