internal/app: modularise outcome finalise

This is the initial effort of splitting up host and container side of finalisation for params to shim. The new layout also enables much finer grained unit testing of each step, as well as partition access to per-app state for each step.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/app/sppulse.go

@@ -0,0 +1,170 @@
+package app
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"syscall"
+
+	"hakurei.app/container"
+	"hakurei.app/hst"
+)
+
+const pulseCookieSizeMax = 1 << 8
+
+// spPulseOp exports the PulseAudio server to the container.
+type spPulseOp struct {
+	// PulseAudio cookie data, populated during toSystem if a cookie is present.
+	Cookie *[pulseCookieSizeMax]byte
+}
+
+func (s *spPulseOp) toSystem(state *outcomeStateSys, _ *hst.Config) error {
+	pulseRuntimeDir, pulseSocket := s.commonPaths(state.outcomeState)
+
+	if _, err := state.k.stat(pulseRuntimeDir.String()); err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			return &hst.AppError{Step: fmt.Sprintf("access PulseAudio directory %q", pulseRuntimeDir), Err: err}
+		}
+		return newWithMessage(fmt.Sprintf("PulseAudio directory %q not found", pulseRuntimeDir))
+	}
+
+	if fi, err := state.k.stat(pulseSocket.String()); err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			return &hst.AppError{Step: fmt.Sprintf("access PulseAudio socket %q", pulseSocket), Err: err}
+		}
+		return newWithMessage(fmt.Sprintf("PulseAudio directory %q found but socket does not exist", pulseRuntimeDir))
+	} else {
+		if m := fi.Mode(); m&0o006 != 0o006 {
+			return newWithMessage(fmt.Sprintf("unexpected permissions on %q: %s", pulseSocket, m))
+		}
+	}
+
+	// hard link pulse socket into target-executable share
+	state.sys.Link(pulseSocket, state.runtime().Append("pulse"))
+
+	// publish current user's pulse cookie for target user
+	var paCookiePath *container.Absolute
+	{
+		const paLocateStep = "locate PulseAudio cookie"
+
+		// from environment
+		if p, ok := state.k.lookupEnv("PULSE_COOKIE"); ok {
+			if a, err := container.NewAbs(p); err != nil {
+				return &hst.AppError{Step: paLocateStep, Err: err}
+			} else {
+				// this takes precedence, do not verify whether the file is accessible
+				paCookiePath = a
+				goto out
+			}
+		}
+
+		// $HOME/.pulse-cookie
+		if p, ok := state.k.lookupEnv("HOME"); ok {
+			if a, err := container.NewAbs(p); err != nil {
+				return &hst.AppError{Step: paLocateStep, Err: err}
+			} else {
+				paCookiePath = a.Append(".pulse-cookie")
+			}
+
+			if fi, err := state.k.stat(paCookiePath.String()); err != nil {
+				paCookiePath = nil
+				if !errors.Is(err, fs.ErrNotExist) {
+					return &hst.AppError{Step: "access PulseAudio cookie", Err: err}
+				}
+				// fallthrough
+			} else if fi.IsDir() {
+				paCookiePath = nil
+			} else {
+				goto out
+			}
+		}
+
+		// $XDG_CONFIG_HOME/pulse/cookie
+		if p, ok := state.k.lookupEnv("XDG_CONFIG_HOME"); ok {
+			if a, err := container.NewAbs(p); err != nil {
+				return &hst.AppError{Step: paLocateStep, Err: err}
+			} else {
+				paCookiePath = a.Append("pulse", "cookie")
+			}
+			if fi, err := state.k.stat(paCookiePath.String()); err != nil {
+				paCookiePath = nil
+				if !errors.Is(err, fs.ErrNotExist) {
+					return &hst.AppError{Step: "access PulseAudio cookie", Err: err}
+				}
+				// fallthrough
+			} else if fi.IsDir() {
+				paCookiePath = nil
+			} else {
+				goto out
+			}
+		}
+	out:
+	}
+
+	if paCookiePath != nil {
+		if b, err := state.k.stat(paCookiePath.String()); err != nil {
+			return &hst.AppError{Step: "access PulseAudio cookie", Err: err}
+		} else {
+			if b.IsDir() {
+				return &hst.AppError{Step: "read PulseAudio cookie", Err: &os.PathError{Op: "stat", Path: paCookiePath.String(), Err: syscall.EISDIR}}
+			}
+			if b.Size() > pulseCookieSizeMax {
+				return newWithMessageError(
+					fmt.Sprintf("PulseAudio cookie at %q exceeds maximum expected size", paCookiePath),
+					&os.PathError{Op: "stat", Path: paCookiePath.String(), Err: syscall.ENOMEM},
+				)
+			}
+		}
+
+		var r io.ReadCloser
+		if f, err := state.k.open(paCookiePath.String()); err != nil {
+			return &hst.AppError{Step: "open PulseAudio cookie", Err: err}
+		} else {
+			r = f
+		}
+
+		s.Cookie = new([pulseCookieSizeMax]byte)
+		if n, err := r.Read(s.Cookie[:]); err != nil {
+			if !errors.Is(err, io.EOF) {
+				_ = r.Close()
+				return &hst.AppError{Step: "read PulseAudio cookie", Err: err}
+			}
+			state.msg.Verbosef("copied %d bytes from %q", n, paCookiePath)
+		}
+
+		if err := r.Close(); err != nil {
+			return &hst.AppError{Step: "close PulseAudio cookie", Err: err}
+		}
+	} else {
+		state.msg.Verbose("cannot locate PulseAudio cookie (tried " +
+			"$PULSE_COOKIE, " +
+			"$XDG_CONFIG_HOME/pulse/cookie, " +
+			"$HOME/.pulse-cookie)")
+	}
+
+	return nil
+}
+
+func (s *spPulseOp) toContainer(state *outcomeStateParams) error {
+	innerPulseSocket := state.runtimeDir.Append("pulse", "native")
+	state.params.Bind(state.runtimePath().Append("pulse"), innerPulseSocket, 0)
+	state.env["PULSE_SERVER"] = "unix:" + innerPulseSocket.String()
+
+	if s.Cookie != nil {
+		innerDst := hst.AbsTmp.Append("/pulse-cookie")
+		state.env["PULSE_COOKIE"] = innerDst.String()
+		state.params.Place(innerDst, s.Cookie[:])
+	}
+
+	return nil
+}
+
+func (s *spPulseOp) commonPaths(state *outcomeState) (pulseRuntimeDir, pulseSocket *container.Absolute) {
+	// PulseAudio runtime directory (usually `/run/user/%d/pulse`)
+	pulseRuntimeDir = state.sc.RuntimePath.Append("pulse")
+	// PulseAudio socket (usually `/run/user/%d/pulse/native`)
+	pulseSocket = pulseRuntimeDir.Append("native")
+	return
+}