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-rw-r--r--pkg/abi/linux/seccomp.go48
-rw-r--r--pkg/seccomp/seccomp.go32
-rw-r--r--pkg/seccomp/seccomp_test.go14
-rw-r--r--pkg/sentry/kernel/seccomp.go53
-rw-r--r--pkg/sentry/kernel/task_syscall.go18
-rw-r--r--pkg/sentry/platform/ptrace/subprocess_linux.go16
6 files changed, 93 insertions, 88 deletions
diff --git a/pkg/abi/linux/seccomp.go b/pkg/abi/linux/seccomp.go
index 785f2f284..8673a27bf 100644
--- a/pkg/abi/linux/seccomp.go
+++ b/pkg/abi/linux/seccomp.go
@@ -14,22 +14,52 @@
package linux
+import "fmt"
+
// Seccomp constants taken from <linux/seccomp.h>.
const (
SECCOMP_MODE_NONE = 0
SECCOMP_MODE_FILTER = 2
- SECCOMP_RET_KILL_PROCESS = 0x80000000
- SECCOMP_RET_KILL_THREAD = 0x00000000
- SECCOMP_RET_TRAP = 0x00030000
- SECCOMP_RET_ERRNO = 0x00050000
- SECCOMP_RET_TRACE = 0x7ff00000
- SECCOMP_RET_ALLOW = 0x7fff0000
-
- SECCOMP_RET_ACTION = 0x7fff0000
- SECCOMP_RET_DATA = 0x0000ffff
+ SECCOMP_RET_ACTION_FULL = 0xffff0000
+ SECCOMP_RET_ACTION = 0x7fff0000
+ SECCOMP_RET_DATA = 0x0000ffff
SECCOMP_SET_MODE_FILTER = 1
SECCOMP_FILTER_FLAG_TSYNC = 1
SECCOMP_GET_ACTION_AVAIL = 2
)
+
+type BPFAction uint32
+
+const (
+ SECCOMP_RET_KILL_PROCESS BPFAction = 0x80000000
+ SECCOMP_RET_KILL_THREAD = 0x00000000
+ SECCOMP_RET_TRAP = 0x00030000
+ SECCOMP_RET_ERRNO = 0x00050000
+ SECCOMP_RET_TRACE = 0x7ff00000
+ SECCOMP_RET_ALLOW = 0x7fff0000
+)
+
+func (a BPFAction) String() string {
+ switch a & SECCOMP_RET_ACTION_FULL {
+ case SECCOMP_RET_KILL_PROCESS:
+ return "kill process"
+ case SECCOMP_RET_KILL_THREAD:
+ return "kill thread"
+ case SECCOMP_RET_TRAP:
+ return fmt.Sprintf("trap (%d)", a.Data())
+ case SECCOMP_RET_ERRNO:
+ return fmt.Sprintf("errno (%d)", a.Data())
+ case SECCOMP_RET_TRACE:
+ return fmt.Sprintf("trace (%d)", a.Data())
+ case SECCOMP_RET_ALLOW:
+ return "allow"
+ }
+ return fmt.Sprintf("invalid action: %#x", a)
+}
+
+// Data returns the SECCOMP_RET_DATA portion of the action.
+func (a BPFAction) Data() uint16 {
+ return uint16(a & SECCOMP_RET_DATA)
+}
diff --git a/pkg/seccomp/seccomp.go b/pkg/seccomp/seccomp.go
index 9d714d02d..ba2955752 100644
--- a/pkg/seccomp/seccomp.go
+++ b/pkg/seccomp/seccomp.go
@@ -33,16 +33,6 @@ const (
defaultLabel = "default_action"
)
-func actionName(a uint32) string {
- switch a {
- case linux.SECCOMP_RET_KILL_PROCESS:
- return "kill process"
- case linux.SECCOMP_RET_TRAP:
- return "trap"
- }
- panic(fmt.Sprintf("invalid action: %d", a))
-}
-
// Install generates BPF code based on the set of syscalls provided. It only
// allows syscalls that conform to the specification. Syscalls that violate the
// specification will trigger RET_KILL_PROCESS, except for the cases below.
@@ -67,12 +57,12 @@ func Install(rules SyscallRules) error {
// Uncomment to get stack trace when there is a violation.
// defaultAction = uint32(linux.SECCOMP_RET_TRAP)
- log.Infof("Installing seccomp filters for %d syscalls (action=%s)", len(rules), actionName(defaultAction))
+ log.Infof("Installing seccomp filters for %d syscalls (action=%v)", len(rules), defaultAction)
instrs, err := BuildProgram([]RuleSet{
RuleSet{
Rules: rules,
- Action: uint32(linux.SECCOMP_RET_ALLOW),
+ Action: linux.SECCOMP_RET_ALLOW,
},
}, defaultAction)
if log.IsLogging(log.Debug) {
@@ -95,21 +85,21 @@ func Install(rules SyscallRules) error {
return nil
}
-func defaultAction() (uint32, error) {
+func defaultAction() (linux.BPFAction, error) {
available, err := isKillProcessAvailable()
if err != nil {
return 0, err
}
if available {
- return uint32(linux.SECCOMP_RET_KILL_PROCESS), nil
+ return linux.SECCOMP_RET_KILL_PROCESS, nil
}
- return uint32(linux.SECCOMP_RET_TRAP), nil
+ return linux.SECCOMP_RET_TRAP, nil
}
// RuleSet is a set of rules and associated action.
type RuleSet struct {
Rules SyscallRules
- Action uint32
+ Action linux.BPFAction
// Vsyscall indicates that a check is made for a function being called
// from kernel mappings. This is where the vsyscall page is located
@@ -127,7 +117,7 @@ var SyscallName = func(sysno uintptr) string {
// BuildProgram builds a BPF program from the given map of actions to matching
// SyscallRules. The single generated program covers all provided RuleSets.
-func BuildProgram(rules []RuleSet, defaultAction uint32) ([]linux.BPFInstruction, error) {
+func BuildProgram(rules []RuleSet, defaultAction linux.BPFAction) ([]linux.BPFInstruction, error) {
program := bpf.NewProgramBuilder()
// Be paranoid and check that syscall is done in the expected architecture.
@@ -147,7 +137,7 @@ func BuildProgram(rules []RuleSet, defaultAction uint32) ([]linux.BPFInstruction
if err := program.AddLabel(defaultLabel); err != nil {
return nil, err
}
- program.AddStmt(bpf.Ret|bpf.K, defaultAction)
+ program.AddStmt(bpf.Ret|bpf.K, uint32(defaultAction))
return program.Instructions()
}
@@ -217,7 +207,7 @@ func checkArgsLabel(sysno uintptr) string {
// not insert a jump to the default action at the end and it is the
// responsibility of the caller to insert an appropriate jump after calling
// this function.
-func addSyscallArgsCheck(p *bpf.ProgramBuilder, rules []Rule, action uint32, ruleSetIdx int, sysno uintptr) error {
+func addSyscallArgsCheck(p *bpf.ProgramBuilder, rules []Rule, action linux.BPFAction, ruleSetIdx int, sysno uintptr) error {
for ruleidx, rule := range rules {
labelled := false
for i, arg := range rule {
@@ -240,7 +230,7 @@ func addSyscallArgsCheck(p *bpf.ProgramBuilder, rules []Rule, action uint32, rul
}
// Matched, emit the given action.
- p.AddStmt(bpf.Ret|bpf.K, action)
+ p.AddStmt(bpf.Ret|bpf.K, uint32(action))
// Label the end of the rule if necessary. This is added for
// the jumps above when the argument check fails.
@@ -319,7 +309,7 @@ func buildBSTProgram(n *node, rules []RuleSet, program *bpf.ProgramBuilder) erro
// Emit matchers.
if len(rs.Rules[sysno]) == 0 {
// This is a blanket action.
- program.AddStmt(bpf.Ret|bpf.K, rs.Action)
+ program.AddStmt(bpf.Ret|bpf.K, uint32(rs.Action))
emitted = true
} else {
// Add an argument check for these particular
diff --git a/pkg/seccomp/seccomp_test.go b/pkg/seccomp/seccomp_test.go
index f2b903e42..11ed90eb4 100644
--- a/pkg/seccomp/seccomp_test.go
+++ b/pkg/seccomp/seccomp_test.go
@@ -72,12 +72,12 @@ func TestBasic(t *testing.T) {
data seccompData
// want is the expected return value of the BPF program.
- want uint32
+ want linux.BPFAction
}
for _, test := range []struct {
ruleSets []RuleSet
- defaultAction uint32
+ defaultAction linux.BPFAction
specs []spec
}{
{
@@ -357,7 +357,7 @@ func TestBasic(t *testing.T) {
t.Errorf("%s: bpf.Exec() got error: %v", spec.desc, err)
continue
}
- if got != spec.want {
+ if got != uint32(spec.want) {
t.Errorf("%s: bpd.Exec() = %d, want: %d", spec.desc, got, spec.want)
}
}
@@ -380,9 +380,9 @@ func TestRandom(t *testing.T) {
instrs, err := BuildProgram([]RuleSet{
RuleSet{
Rules: syscallRules,
- Action: uint32(linux.SECCOMP_RET_ALLOW),
+ Action: linux.SECCOMP_RET_ALLOW,
},
- }, uint32(linux.SECCOMP_RET_TRAP))
+ }, linux.SECCOMP_RET_TRAP)
if err != nil {
t.Fatalf("buildProgram() got error: %v", err)
}
@@ -397,11 +397,11 @@ func TestRandom(t *testing.T) {
t.Errorf("bpf.Exec() got error: %v, for syscall %d", err, i)
continue
}
- want := uint32(linux.SECCOMP_RET_TRAP)
+ want := linux.SECCOMP_RET_TRAP
if _, ok := syscallRules[uintptr(i)]; ok {
want = linux.SECCOMP_RET_ALLOW
}
- if got != want {
+ if got != uint32(want) {
t.Errorf("bpf.Exec() = %d, want: %d, for syscall %d", got, want, i)
}
}
diff --git a/pkg/sentry/kernel/seccomp.go b/pkg/sentry/kernel/seccomp.go
index d6dc45bbd..cec179246 100644
--- a/pkg/sentry/kernel/seccomp.go
+++ b/pkg/sentry/kernel/seccomp.go
@@ -27,24 +27,6 @@ import (
const maxSyscallFilterInstructions = 1 << 15
-type seccompResult int
-
-const (
- // seccompResultDeny indicates that a syscall should not be executed.
- seccompResultDeny seccompResult = iota
-
- // seccompResultAllow indicates that a syscall should be executed.
- seccompResultAllow
-
- // seccompResultKill indicates that the task should be killed immediately,
- // with the exit status indicating that the task was killed by SIGSYS.
- seccompResultKill
-
- // seccompResultTrace indicates that a ptracer was successfully notified as
- // a result of a SECCOMP_RET_TRACE.
- seccompResultTrace
-)
-
// seccompData is equivalent to struct seccomp_data, which contains the data
// passed to seccomp-bpf filters.
type seccompData struct {
@@ -83,48 +65,47 @@ func seccompSiginfo(t *Task, errno, sysno int32, ip usermem.Addr) *arch.SignalIn
// in because vsyscalls do not use the values in t.Arch().)
//
// Preconditions: The caller must be running on the task goroutine.
-func (t *Task) checkSeccompSyscall(sysno int32, args arch.SyscallArguments, ip usermem.Addr) seccompResult {
- result := t.evaluateSyscallFilters(sysno, args, ip)
- switch result & linux.SECCOMP_RET_ACTION {
+func (t *Task) checkSeccompSyscall(sysno int32, args arch.SyscallArguments, ip usermem.Addr) linux.BPFAction {
+ result := linux.BPFAction(t.evaluateSyscallFilters(sysno, args, ip))
+ action := result & linux.SECCOMP_RET_ACTION
+ switch action {
case linux.SECCOMP_RET_TRAP:
// "Results in the kernel sending a SIGSYS signal to the triggering
// task without executing the system call. ... The SECCOMP_RET_DATA
// portion of the return value will be passed as si_errno." -
// Documentation/prctl/seccomp_filter.txt
- t.SendSignal(seccompSiginfo(t, int32(result&linux.SECCOMP_RET_DATA), sysno, ip))
- return seccompResultDeny
+ t.SendSignal(seccompSiginfo(t, int32(result.Data()), sysno, ip))
case linux.SECCOMP_RET_ERRNO:
// "Results in the lower 16-bits of the return value being passed to
// userland as the errno without executing the system call."
- t.Arch().SetReturn(-uintptr(result & linux.SECCOMP_RET_DATA))
- return seccompResultDeny
+ t.Arch().SetReturn(-uintptr(result.Data()))
case linux.SECCOMP_RET_TRACE:
// "When returned, this value will cause the kernel to attempt to
// notify a ptrace()-based tracer prior to executing the system call.
// If there is no tracer present, -ENOSYS is returned to userland and
// the system call is not executed."
- if t.ptraceSeccomp(uint16(result & linux.SECCOMP_RET_DATA)) {
- return seccompResultTrace
+ if !t.ptraceSeccomp(result.Data()) {
+ // This useless-looking temporary is needed because Go.
+ tmp := uintptr(syscall.ENOSYS)
+ t.Arch().SetReturn(-tmp)
+ return linux.SECCOMP_RET_ERRNO
}
- // This useless-looking temporary is needed because Go.
- tmp := uintptr(syscall.ENOSYS)
- t.Arch().SetReturn(-tmp)
- return seccompResultDeny
case linux.SECCOMP_RET_ALLOW:
// "Results in the system call being executed."
- return seccompResultAllow
case linux.SECCOMP_RET_KILL_THREAD:
// "Results in the task exiting immediately without executing the
// system call. The exit status of the task will be SIGSYS, not
// SIGKILL."
- fallthrough
- default: // consistent with Linux
- return seccompResultKill
+
+ default:
+ // consistent with Linux
+ return linux.SECCOMP_RET_KILL_THREAD
}
+ return action
}
func (t *Task) evaluateSyscallFilters(sysno int32, args arch.SyscallArguments, ip usermem.Addr) uint32 {
@@ -155,7 +136,7 @@ func (t *Task) evaluateSyscallFilters(sysno int32, args arch.SyscallArguments, i
thisRet, err := bpf.Exec(f.([]bpf.Program)[i], input)
if err != nil {
t.Debugf("seccomp-bpf filter %d returned error: %v", i, err)
- thisRet = linux.SECCOMP_RET_KILL_THREAD
+ thisRet = uint32(linux.SECCOMP_RET_KILL_THREAD)
}
// "If multiple filters exist, the return value for the evaluation of a
// given system call will always use the highest precedent value." -
diff --git a/pkg/sentry/kernel/task_syscall.go b/pkg/sentry/kernel/task_syscall.go
index 2a39ebc68..9e43f089a 100644
--- a/pkg/sentry/kernel/task_syscall.go
+++ b/pkg/sentry/kernel/task_syscall.go
@@ -199,16 +199,16 @@ func (t *Task) doSyscall() taskRunState {
// is rare), not needed for correctness.
if t.syscallFilters.Load() != nil {
switch r := t.checkSeccompSyscall(int32(sysno), args, usermem.Addr(t.Arch().IP())); r {
- case seccompResultDeny:
+ case linux.SECCOMP_RET_ERRNO, linux.SECCOMP_RET_TRAP:
t.Debugf("Syscall %d: denied by seccomp", sysno)
return (*runSyscallExit)(nil)
- case seccompResultAllow:
+ case linux.SECCOMP_RET_ALLOW:
// ok
- case seccompResultKill:
+ case linux.SECCOMP_RET_KILL_THREAD:
t.Debugf("Syscall %d: killed by seccomp", sysno)
t.PrepareExit(ExitStatus{Signo: int(linux.SIGSYS)})
return (*runExit)(nil)
- case seccompResultTrace:
+ case linux.SECCOMP_RET_TRACE:
t.Debugf("Syscall %d: stopping for PTRACE_EVENT_SECCOMP", sysno)
return (*runSyscallAfterPtraceEventSeccomp)(nil)
default:
@@ -345,14 +345,18 @@ func (t *Task) doVsyscall(addr usermem.Addr, sysno uintptr) taskRunState {
args := t.Arch().SyscallArgs()
if t.syscallFilters.Load() != nil {
switch r := t.checkSeccompSyscall(int32(sysno), args, addr); r {
- case seccompResultDeny:
+ case linux.SECCOMP_RET_ERRNO, linux.SECCOMP_RET_TRAP:
t.Debugf("vsyscall %d, caller %x: denied by seccomp", sysno, t.Arch().Value(caller))
return (*runApp)(nil)
- case seccompResultAllow:
+ case linux.SECCOMP_RET_ALLOW:
// ok
- case seccompResultTrace:
+ case linux.SECCOMP_RET_TRACE:
t.Debugf("vsyscall %d, caller %x: stopping for PTRACE_EVENT_SECCOMP", sysno, t.Arch().Value(caller))
return &runVsyscallAfterPtraceEventSeccomp{addr, sysno, caller}
+ case linux.SECCOMP_RET_KILL_THREAD:
+ t.Debugf("vsyscall %d: killed by seccomp", sysno)
+ t.PrepareExit(ExitStatus{Signo: int(linux.SIGSYS)})
+ return (*runExit)(nil)
default:
panic(fmt.Sprintf("Unknown seccomp result %d", r))
}
diff --git a/pkg/sentry/platform/ptrace/subprocess_linux.go b/pkg/sentry/platform/ptrace/subprocess_linux.go
index 25b8e8cb7..e2aab8135 100644
--- a/pkg/sentry/platform/ptrace/subprocess_linux.go
+++ b/pkg/sentry/platform/ptrace/subprocess_linux.go
@@ -38,7 +38,7 @@ const syscallEvent syscall.Signal = 0x80
// Precondition: the runtime OS thread must be locked.
func probeSeccomp() bool {
// Create a completely new, destroyable process.
- t, err := attachedThread(0, uint32(linux.SECCOMP_RET_ERRNO))
+ t, err := attachedThread(0, linux.SECCOMP_RET_ERRNO)
if err != nil {
panic(fmt.Sprintf("seccomp probe failed: %v", err))
}
@@ -112,14 +112,14 @@ func createStub() (*thread, error) {
// ptrace emulation check. This simplifies using SYSEMU, since seccomp
// will never run for emulation. Seccomp will only run for injected
// system calls, and thus we can use RET_KILL as our violation action.
- var defaultAction uint32
+ var defaultAction linux.BPFAction
if probeSeccomp() {
log.Infof("Latest seccomp behavior found (kernel >= 4.8 likely)")
- defaultAction = uint32(linux.SECCOMP_RET_KILL_THREAD)
+ defaultAction = linux.SECCOMP_RET_KILL_THREAD
} else {
// We must rely on SYSEMU behavior; tracing with SYSEMU is broken.
log.Infof("Legacy seccomp behavior found (kernel < 4.8 likely)")
- defaultAction = uint32(linux.SECCOMP_RET_ALLOW)
+ defaultAction = linux.SECCOMP_RET_ALLOW
}
// When creating the new child process, we specify SIGKILL as the
@@ -135,7 +135,7 @@ func createStub() (*thread, error) {
// attachedThread returns a new attached thread.
//
// Precondition: the runtime OS thread must be locked.
-func attachedThread(flags uintptr, defaultAction uint32) (*thread, error) {
+func attachedThread(flags uintptr, defaultAction linux.BPFAction) (*thread, error) {
// Create a BPF program that allows only the system calls needed by the
// stub and all its children. This is used to create child stubs
// (below), so we must include the ability to fork, but otherwise lock
@@ -148,11 +148,11 @@ func attachedThread(flags uintptr, defaultAction uint32) (*thread, error) {
syscall.SYS_TIME: {},
309: {}, // SYS_GETCPU.
},
- Action: uint32(linux.SECCOMP_RET_TRAP),
+ Action: linux.SECCOMP_RET_TRAP,
Vsyscall: true,
},
}
- if defaultAction != uint32(linux.SECCOMP_RET_ALLOW) {
+ if defaultAction != linux.SECCOMP_RET_ALLOW {
rules = append(rules, seccomp.RuleSet{
Rules: seccomp.SyscallRules{
syscall.SYS_CLONE: []seccomp.Rule{
@@ -191,7 +191,7 @@ func attachedThread(flags uintptr, defaultAction uint32) (*thread, error) {
syscall.SYS_MMAP: {},
syscall.SYS_MUNMAP: {},
},
- Action: uint32(linux.SECCOMP_RET_ALLOW),
+ Action: linux.SECCOMP_RET_ALLOW,
})
}
instrs, err := seccomp.BuildProgram(rules, defaultAction)
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-05 08:23:28 +0000