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Tap plugin - alternative PR #794
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mmirecki
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,83 @@ | ||
| package security | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "github.com/opencontainers/selinux/go-selinux" | ||
| "os" | ||
| "os/exec" | ||
| "strconv" | ||
| "strings" | ||
| "syscall" | ||
| ) | ||
|
|
||
| type SecurityModule interface { | ||
| PrepareSecurityModule() error | ||
| RequiresReboot() bool | ||
| ReRunCommandWithSecurityLabels(addLinkString string, tmpName string, mtu int, nsFd int, multique bool, mac string) error | ||
| } | ||
|
|
||
| type NoSecurityModel struct { | ||
| } | ||
|
|
||
| type SELinuxSecurityModel struct { | ||
| } | ||
|
|
||
| func GetSecurityModule() SecurityModule { | ||
| if selinux.EnforceMode() != -1 { | ||
| return SELinuxSecurityModel{} | ||
| } | ||
| return NoSecurityModel{} | ||
| } | ||
|
|
||
| func (sm NoSecurityModel) PrepareSecurityModule() error { | ||
| return nil | ||
| } | ||
| func (sm NoSecurityModel) RequiresReboot() bool { | ||
| return false | ||
| } | ||
| func (sm NoSecurityModel) ReRunCommandWithSecurityLabels(addLinkString string, tmpName string, mtu int, nsFd int, multique bool, mac string) error { | ||
| return nil | ||
| } | ||
|
|
||
| func (sm SELinuxSecurityModel) PrepareSecurityModule() error { | ||
| output, err := exec.Command("getsebool", "container_use_devices").CombinedOutput() | ||
| if err != nil { | ||
| return fmt.Errorf("failed to run getsebool command %s: %v", string(output), err) | ||
| } | ||
| if strings.Contains(string(output), "off") { | ||
| output, err := exec.Command("setsebool", "-P", "container_use_devices", "true").CombinedOutput() | ||
| if err != nil { | ||
| return fmt.Errorf("failed to run setsebool command %s: %v", string(output), err) | ||
| } | ||
| } | ||
| return nil | ||
| } | ||
| func (sm SELinuxSecurityModel) RequiresReboot() bool { | ||
| return true | ||
| } | ||
|
|
||
| // This is a workaround for a SELinux issue when creating taps in containers. | ||
| // The tap device must be created with approperiate SE Linux labels, which the plugin is missing. | ||
| // To achieve this we run another copy of the plugin with the required labels applied. This will | ||
| // create the tap device from a process with the correct labels. The controll then returns to the | ||
| // main instance of the plugin which performs the rest of the configuration. | ||
| func (sm SELinuxSecurityModel) ReRunCommandWithSecurityLabels(addLinkString string, tmpName string, mtu int, nsFd int, multique bool, mac string) error { | ||
| // Apply the appropriate se linux label. This will affect the newly executed plugin process. | ||
| if err := selinux.SetExecLabel("system_u:system_r:container_t:s0"); err != nil { | ||
| return fmt.Errorf("failed set socket label: %v", err) | ||
| } | ||
| minFDToCloseOnExec := 3 | ||
| maxFDToCloseOnExec := 256 | ||
| // we want to share the parent process std{in|out|err} - fds 0 through 2. | ||
| // Since the FDs are inherited on fork / exec, we close on exec all others. | ||
| for fd := minFDToCloseOnExec; fd < maxFDToCloseOnExec; fd++ { | ||
| syscall.CloseOnExec(fd) | ||
| } | ||
|
|
||
| args := []string{addLinkString, tmpName, strconv.Itoa(mtu), strconv.Itoa(nsFd), strconv.FormatBool(multique), mac} | ||
| output, err := exec.Command(os.Args[0], args...).CombinedOutput() | ||
| if err != nil { | ||
| return fmt.Errorf("failed to run a nested plugin call (%s %s) to add link: %s: %v", os.Args[0], strings.Join(args, ", "), output, err) | ||
| } | ||
| return nil | ||
| } | ||
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I see these labels are hard-coded; is that the norm?
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This is specific to just the selinux security module. Other modules would of course have different mechanisms (if present).
This PR was a proposal on how to extract the security module specific items from the main plugin code, but it seems this approach has not met with approval either, so I'm closing it.