libpod: Factor out capabilites code from prepareProcessExec

This moves the code which sets the process capabilites for the exec to
oci_conmon_exec_linux.go since this is a linux-specific feature. Adding
a no-op stub for FreeBSD enables 'podman exec' when using the ocijail
runtime.

[NO NEW TESTS NEEDED]

Signed-off-by: Doug Rabson <dfr@rabson.org>

libpod/oci_conmon_exec_common.go

@@ -12,7 +12,6 @@ import (
 	"syscall"
 	"time"
 
-	"github.com/containers/common/pkg/capabilities"
 	"github.com/containers/common/pkg/config"
 	"github.com/containers/common/pkg/resize"
 	cutil "github.com/containers/common/pkg/util"
@@ -386,7 +385,7 @@ func (r *ConmonOCIRuntime) startExec(c *Container, sessionID string, options *Ex
 		finalEnv = append(finalEnv, fmt.Sprintf("%s=%s", k, v))
 	}
 
-	processFile, err := prepareProcessExec(c, options, finalEnv, sessionID)
+	processFile, err := c.prepareProcessExec(options, finalEnv, sessionID)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -665,7 +664,7 @@ func attachExecHTTP(c *Container, sessionID string, r *http.Request, w http.Resp
 
 // prepareProcessExec returns the path of the process.json used in runc exec -p
 // caller is responsible to close the returned *os.File if needed.
-func prepareProcessExec(c *Container, options *ExecOptions, env []string, sessionID string) (*os.File, error) {
+func (c *Container) prepareProcessExec(options *ExecOptions, env []string, sessionID string) (*os.File, error) {
 	f, err := ioutil.TempFile(c.execBundlePath(sessionID), "exec-process-")
 	if err != nil {
 		return nil, err
@@ -745,35 +744,10 @@ func prepareProcessExec(c *Container, options *ExecOptions, env []string, sessio
 		pspec.User = processUser
 	}
 
-	ctrSpec, err := c.specFromState()
+	if err := c.setProcessCapabilitiesExec(options, user, execUser, pspec); err != nil {
-	if err != nil {
 		return nil, err
 	}
 
-	allCaps, err := capabilities.BoundingSet()
-	if err != nil {
-		return nil, err
-	}
-	if options.Privileged {
-		pspec.Capabilities.Bounding = allCaps
-	} else {
-		pspec.Capabilities.Bounding = ctrSpec.Process.Capabilities.Bounding
-	}
-
-	// Always unset the inheritable capabilities similarly to what the Linux kernel does
-	// They are used only when using capabilities with uid != 0.
-	pspec.Capabilities.Inheritable = []string{}
-
-	if execUser.Uid == 0 {
-		pspec.Capabilities.Effective = pspec.Capabilities.Bounding
-		pspec.Capabilities.Permitted = pspec.Capabilities.Bounding
-	} else if user == c.config.User {
-		pspec.Capabilities.Effective = ctrSpec.Process.Capabilities.Effective
-		pspec.Capabilities.Inheritable = ctrSpec.Process.Capabilities.Effective
-		pspec.Capabilities.Permitted = ctrSpec.Process.Capabilities.Effective
-		pspec.Capabilities.Ambient = ctrSpec.Process.Capabilities.Effective
-	}
-
 	hasHomeSet := false
 	for _, s := range pspec.Env {
 		if strings.HasPrefix(s, "HOME=") {

libpod/oci_conmon_exec_freebsd.go

@@ -0,0 +1,10 @@
+package libpod
+
+import (
+	"github.com/opencontainers/runc/libcontainer/user"
+	spec "github.com/opencontainers/runtime-spec/specs-go"
+)
+
+func (c *Container) setProcessCapabilitiesExec(options *ExecOptions, user string, execUser *user.ExecUser, pspec *spec.Process) error {
+	return nil
+}

libpod/oci_conmon_exec_linux.go

@@ -0,0 +1,39 @@
+package libpod
+
+import (
+	"github.com/containers/common/pkg/capabilities"
+	"github.com/opencontainers/runc/libcontainer/user"
+	spec "github.com/opencontainers/runtime-spec/specs-go"
+)
+
+func (c *Container) setProcessCapabilitiesExec(options *ExecOptions, user string, execUser *user.ExecUser, pspec *spec.Process) error {
+	ctrSpec, err := c.specFromState()
+	if err != nil {
+		return err
+	}
+
+	allCaps, err := capabilities.BoundingSet()
+	if err != nil {
+		return err
+	}
+	if options.Privileged {
+		pspec.Capabilities.Bounding = allCaps
+	} else {
+		pspec.Capabilities.Bounding = ctrSpec.Process.Capabilities.Bounding
+	}
+
+	// Always unset the inheritable capabilities similarly to what the Linux kernel does
+	// They are used only when using capabilities with uid != 0.
+	pspec.Capabilities.Inheritable = []string{}
+
+	if execUser.Uid == 0 {
+		pspec.Capabilities.Effective = pspec.Capabilities.Bounding
+		pspec.Capabilities.Permitted = pspec.Capabilities.Bounding
+	} else if user == c.config.User {
+		pspec.Capabilities.Effective = ctrSpec.Process.Capabilities.Effective
+		pspec.Capabilities.Inheritable = ctrSpec.Process.Capabilities.Effective
+		pspec.Capabilities.Permitted = ctrSpec.Process.Capabilities.Effective
+		pspec.Capabilities.Ambient = ctrSpec.Process.Capabilities.Effective
+	}
+	return nil
+}