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>

1 files changed, 39 insertions, 0 deletions

diff --git a/libpod/oci_conmon_exec_linux.go b/libpod/oci_conmon_exec_linux.go
new file mode 100644
index 000000000..617e8d601
--- /dev/null
+++ b/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
+}