/usr/share/gocode/src/github.com/opencontainers/runc/libcontainer/seccomp/seccomp_linux.go is in golang-github-opencontainers-runc-dev 0.0.8+dfsg-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 | // +build linux,cgo,seccomp
package seccomp
import (
"bufio"
"fmt"
"log"
"os"
"strings"
"syscall"
"github.com/opencontainers/runc/libcontainer/configs"
libseccomp "github.com/seccomp/libseccomp-golang"
)
var (
actAllow = libseccomp.ActAllow
actTrap = libseccomp.ActTrap
actKill = libseccomp.ActKill
actTrace = libseccomp.ActTrace.SetReturnCode(int16(syscall.EPERM))
actErrno = libseccomp.ActErrno.SetReturnCode(int16(syscall.EPERM))
// SeccompModeFilter refers to the syscall argument SECCOMP_MODE_FILTER.
SeccompModeFilter = uintptr(2)
)
// Filters given syscalls in a container, preventing them from being used
// Started in the container init process, and carried over to all child processes
// Setns calls, however, require a separate invocation, as they are not children
// of the init until they join the namespace
func InitSeccomp(config *configs.Seccomp) error {
if config == nil {
return fmt.Errorf("cannot initialize Seccomp - nil config passed")
}
defaultAction, err := getAction(config.DefaultAction)
if err != nil {
return fmt.Errorf("error initializing seccomp - invalid default action")
}
filter, err := libseccomp.NewFilter(defaultAction)
if err != nil {
return fmt.Errorf("error creating filter: %s", err)
}
// Add extra architectures
for _, arch := range config.Architectures {
scmpArch, err := libseccomp.GetArchFromString(arch)
if err != nil {
return err
}
if err := filter.AddArch(scmpArch); err != nil {
return err
}
}
// Unset no new privs bit
if err := filter.SetNoNewPrivsBit(false); err != nil {
return fmt.Errorf("error setting no new privileges: %s", err)
}
// Add a rule for each syscall
for _, call := range config.Syscalls {
if call == nil {
return fmt.Errorf("encountered nil syscall while initializing Seccomp")
}
if err = matchCall(filter, call); err != nil {
return err
}
}
if err = filter.Load(); err != nil {
return fmt.Errorf("error loading seccomp filter into kernel: %s", err)
}
return nil
}
// IsEnabled returns if the kernel has been configured to support seccomp.
func IsEnabled() bool {
// Try to read from /proc/self/status for kernels > 3.8
s, err := parseStatusFile("/proc/self/status")
if err != nil {
// Check if Seccomp is supported, via CONFIG_SECCOMP.
if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_GET_SECCOMP, 0, 0); err != syscall.EINVAL {
// Make sure the kernel has CONFIG_SECCOMP_FILTER.
if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_SECCOMP, SeccompModeFilter, 0); err != syscall.EINVAL {
return true
}
}
return false
}
_, ok := s["Seccomp"]
return ok
}
// Convert Libcontainer Action to Libseccomp ScmpAction
func getAction(act configs.Action) (libseccomp.ScmpAction, error) {
switch act {
case configs.Kill:
return actKill, nil
case configs.Errno:
return actErrno, nil
case configs.Trap:
return actTrap, nil
case configs.Allow:
return actAllow, nil
case configs.Trace:
return actTrace, nil
default:
return libseccomp.ActInvalid, fmt.Errorf("invalid action, cannot use in rule")
}
}
// Convert Libcontainer Operator to Libseccomp ScmpCompareOp
func getOperator(op configs.Operator) (libseccomp.ScmpCompareOp, error) {
switch op {
case configs.EqualTo:
return libseccomp.CompareEqual, nil
case configs.NotEqualTo:
return libseccomp.CompareNotEqual, nil
case configs.GreaterThan:
return libseccomp.CompareGreater, nil
case configs.GreaterThanOrEqualTo:
return libseccomp.CompareGreaterEqual, nil
case configs.LessThan:
return libseccomp.CompareLess, nil
case configs.LessThanOrEqualTo:
return libseccomp.CompareLessOrEqual, nil
case configs.MaskEqualTo:
return libseccomp.CompareMaskedEqual, nil
default:
return libseccomp.CompareInvalid, fmt.Errorf("invalid operator, cannot use in rule")
}
}
// Convert Libcontainer Arg to Libseccomp ScmpCondition
func getCondition(arg *configs.Arg) (libseccomp.ScmpCondition, error) {
cond := libseccomp.ScmpCondition{}
if arg == nil {
return cond, fmt.Errorf("cannot convert nil to syscall condition")
}
op, err := getOperator(arg.Op)
if err != nil {
return cond, err
}
return libseccomp.MakeCondition(arg.Index, op, arg.Value, arg.ValueTwo)
}
// Add a rule to match a single syscall
func matchCall(filter *libseccomp.ScmpFilter, call *configs.Syscall) error {
if call == nil || filter == nil {
return fmt.Errorf("cannot use nil as syscall to block")
}
if len(call.Name) == 0 {
return fmt.Errorf("empty string is not a valid syscall")
}
// If we can't resolve the syscall, assume it's not supported on this kernel
// Ignore it, don't error out
callNum, err := libseccomp.GetSyscallFromName(call.Name)
if err != nil {
log.Printf("Error resolving syscall name %s: %s - ignoring syscall.", call.Name, err)
return nil
}
// Convert the call's action to the libseccomp equivalent
callAct, err := getAction(call.Action)
if err != nil {
return err
}
// Unconditional match - just add the rule
if len(call.Args) == 0 {
if err = filter.AddRule(callNum, callAct); err != nil {
return err
}
} else {
// Conditional match - convert the per-arg rules into library format
conditions := []libseccomp.ScmpCondition{}
for _, cond := range call.Args {
newCond, err := getCondition(cond)
if err != nil {
return err
}
conditions = append(conditions, newCond)
}
if err = filter.AddRuleConditional(callNum, callAct, conditions); err != nil {
return err
}
}
return nil
}
func parseStatusFile(path string) (map[string]string, error) {
f, err := os.Open(path)
if err != nil {
return nil, err
}
defer f.Close()
s := bufio.NewScanner(f)
status := make(map[string]string)
for s.Scan() {
if err := s.Err(); err != nil {
return nil, err
}
text := s.Text()
parts := strings.Split(text, ":")
if len(parts) <= 1 {
continue
}
status[parts[0]] = parts[1]
}
return status, nil
}
|