sandbox: move params setup functions

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

internal/app/init0/main.go

@@ -9,7 +9,6 @@ import (
 	"syscall"
 	"time"
 
-	"git.gensokyo.uk/security/fortify/helper/proc"
 	"git.gensokyo.uk/security/fortify/internal"
 	"git.gensokyo.uk/security/fortify/internal/fmsg"
 	"git.gensokyo.uk/security/fortify/internal/sandbox"
@@ -42,11 +41,11 @@ func Main() {
 		payload    Payload
 		closeSetup func() error
 	)
-	if f, err := proc.Receive(Env, &payload, nil); err != nil {
-		if errors.Is(err, proc.ErrInvalid) {
+	if f, err := sandbox.Receive(Env, &payload, nil); err != nil {
+		if errors.Is(err, sandbox.ErrInvalid) {
 			log.Fatal("invalid config descriptor")
 		}
-		if errors.Is(err, proc.ErrNotSet) {
+		if errors.Is(err, sandbox.ErrNotSet) {
 			log.Fatal("FORTIFY_INIT not set")
 		}
 

internal/app/shim/main.go

@@ -13,7 +13,6 @@ import (
 
 	"git.gensokyo.uk/security/fortify/fst"
 	"git.gensokyo.uk/security/fortify/helper"
-	"git.gensokyo.uk/security/fortify/helper/proc"
 	"git.gensokyo.uk/security/fortify/internal"
 	"git.gensokyo.uk/security/fortify/internal/app/init0"
 	"git.gensokyo.uk/security/fortify/internal/fmsg"
@@ -38,11 +37,11 @@ func Main() {
 		payload    Payload
 		closeSetup func() error
 	)
-	if f, err := proc.Receive(Env, &payload, nil); err != nil {
-		if errors.Is(err, proc.ErrInvalid) {
+	if f, err := sandbox.Receive(Env, &payload, nil); err != nil {
+		if errors.Is(err, sandbox.ErrInvalid) {
 			log.Fatal("invalid config descriptor")
 		}
-		if errors.Is(err, proc.ErrNotSet) {
+		if errors.Is(err, sandbox.ErrNotSet) {
 			log.Fatal("FORTIFY_SHIM not set")
 		}
 
@@ -108,7 +107,7 @@ func Main() {
 	var extraFiles []*os.File
 
 	// serve setup payload
-	if fd, encoder, err := proc.Setup(&extraFiles); err != nil {
+	if fd, encoder, err := sandbox.Setup(&extraFiles); err != nil {
 		log.Fatalf("cannot pipe: %v", err)
 	} else {
 		conf.SetEnv[init0.Env] = strconv.Itoa(fd)

internal/app/shim/manager.go

@@ -13,6 +13,7 @@ import (
 	"git.gensokyo.uk/security/fortify/helper/proc"
 	"git.gensokyo.uk/security/fortify/internal"
 	"git.gensokyo.uk/security/fortify/internal/fmsg"
+	"git.gensokyo.uk/security/fortify/internal/sandbox"
 )
 
 // used by the parent process
@@ -56,7 +57,7 @@ func (s *Shim) Start(
 	s.cmd = exec.Command(fsuPath)
 
 	// pass shim setup pipe
-	if fd, e, err := proc.Setup(&s.cmd.ExtraFiles); err != nil {
+	if fd, e, err := sandbox.Setup(&s.cmd.ExtraFiles); err != nil {
 		return nil, fmsg.WrapErrorSuffix(err,
 			"cannot create shim setup pipe:")
 	} else {

internal/sandbox/container.go

@@ -13,7 +13,6 @@ import (
 	"syscall"
 	"time"
 
-	"git.gensokyo.uk/security/fortify/helper/proc"
 	"git.gensokyo.uk/security/fortify/seccomp"
 )
 
@@ -163,7 +162,7 @@ func (p *Container) Start() error {
 	}
 
 	// place setup pipe before user supplied extra files, this is later restored by init
-	if fd, e, err := proc.Setup(&p.cmd.ExtraFiles); err != nil {
+	if fd, e, err := Setup(&p.cmd.ExtraFiles); err != nil {
 		return wrapErrSuffix(err,
 			"cannot create shim setup pipe:")
 	} else {

internal/sandbox/init.go

@@ -13,7 +13,6 @@ import (
 	"syscall"
 	"time"
 
-	"git.gensokyo.uk/security/fortify/helper/proc"
 	"git.gensokyo.uk/security/fortify/seccomp"
 )
 
@@ -56,11 +55,11 @@ func Init(prepare func(prefix string), setVerbose func(verbose bool)) {
 		setupFile   *os.File
 		offsetSetup int
 	)
-	if f, err := proc.Receive(setupEnv, &params, &setupFile); err != nil {
-		if errors.Is(err, proc.ErrInvalid) {
+	if f, err := Receive(setupEnv, &params, &setupFile); err != nil {
+		if errors.Is(err, ErrInvalid) {
 			log.Fatal("invalid setup descriptor")
 		}
-		if errors.Is(err, proc.ErrNotSet) {
+		if errors.Is(err, ErrNotSet) {
 			log.Fatal("FORTIFY_SETUP not set")
 		}
 

internal/sandbox/params.go

@@ -0,0 +1,47 @@
+package sandbox
+
+import (
+	"encoding/gob"
+	"errors"
+	"os"
+	"strconv"
+)
+
+var (
+	ErrNotSet  = errors.New("environment variable not set")
+	ErrInvalid = errors.New("bad file descriptor")
+)
+
+// Setup appends the read end of a pipe for setup params transmission and returns its fd.
+func Setup(extraFiles *[]*os.File) (int, *gob.Encoder, error) {
+	if r, w, err := os.Pipe(); err != nil {
+		return -1, nil, err
+	} else {
+		fd := 3 + len(*extraFiles)
+		*extraFiles = append(*extraFiles, r)
+		return fd, gob.NewEncoder(w), nil
+	}
+}
+
+// Receive retrieves setup fd from the environment and receives params.
+func Receive(key string, e any, v **os.File) (func() error, error) {
+	var setup *os.File
+
+	if s, ok := os.LookupEnv(key); !ok {
+		return nil, ErrNotSet
+	} else {
+		if fd, err := strconv.Atoi(s); err != nil {
+			return nil, err
+		} else {
+			setup = os.NewFile(uintptr(fd), "setup")
+			if setup == nil {
+				return nil, ErrInvalid
+			}
+			if v != nil {
+				*v = setup
+			}
+		}
+	}
+
+	return setup.Close, gob.NewDecoder(setup).Decode(e)
+}