acl: rename UpdatePerms to Update

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

1 files changed, 190 insertions, 12 deletions

diff --git a/acl/acl.go b/acl/acl.go
index 8b775688..fe355612 100644
--- a/acl/acl.go
+++ b/acl/acl.go
@@ -1,19 +1,197 @@
 // Package acl implements simple ACL manipulation via libacl.
 package acl
 
-type Perms []Perm
+import (
+	"errors"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
 
-func (ps Perms) String() string {
-	var s = []byte("---")
-	for _, p := range ps {
-		switch p {
-		case Read:
-			s[0] = 'r'
-		case Write:
-			s[1] = 'w'
-		case Execute:
-			s[2] = 'x'
+/*
+#cgo linux pkg-config: --static libacl
+
+#include <stdlib.h>
+#include <sys/acl.h>
+#include <acl/libacl.h>
+
+static acl_t _go_acl_get_file(const char *path_p, acl_type_t type) {
+	acl_t acl = acl_get_file(path_p, type);
+	free((void *)path_p);
+	return acl;
+}
+
+static int _go_acl_set_file(const char *path_p, acl_type_t type, acl_t acl) {
+	if (acl_valid(acl) != 0) {
+		return -1;
+	}
+
+	int ret = acl_set_file(path_p, type, acl);
+	free((void *)path_p);
+	return ret;
+}
+*/
+import "C"
+
+func getFile(name string, t C.acl_type_t) (*ACL, error) {
+	a, err := C._go_acl_get_file(C.CString(name), t)
+	if errors.Is(err, syscall.ENODATA) {
+		err = nil
+	}
+
+	return newACL(a), err
+}
+
+func (acl *ACL) setFile(name string, t C.acl_type_t) error {
+	_, err := C._go_acl_set_file(C.CString(name), t, acl.acl)
+	return err
+}
+
+func newACL(a C.acl_t) *ACL {
+	acl := &ACL{a}
+	runtime.SetFinalizer(acl, (*ACL).free)
+	return acl
+}
+
+type ACL struct {
+	acl C.acl_t
+}
+
+func (acl *ACL) free() {
+	C.acl_free(unsafe.Pointer(acl.acl))
+
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(acl, nil)
+}
+
+const (
+	Read    = C.ACL_READ
+	Write   = C.ACL_WRITE
+	Execute = C.ACL_EXECUTE
+
+	TypeDefault = C.ACL_TYPE_DEFAULT
+	TypeAccess  = C.ACL_TYPE_ACCESS
+
+	UndefinedTag = C.ACL_UNDEFINED_TAG
+	UserObj      = C.ACL_USER_OBJ
+	User         = C.ACL_USER
+	GroupObj     = C.ACL_GROUP_OBJ
+	Group        = C.ACL_GROUP
+	Mask         = C.ACL_MASK
+	Other        = C.ACL_OTHER
+)
+
+type (
+	Perm C.acl_perm_t
+)
+
+func (acl *ACL) removeEntry(tt C.acl_tag_t, tq int) error {
+	var e C.acl_entry_t
+
+	// get first entry
+	if r, err := C.acl_get_entry(acl.acl, C.ACL_FIRST_ENTRY, &e); err != nil {
+		return err
+	} else if r == 0 {
+		// return on acl with no entries
+		return nil
+	}
+
+	for {
+		if r, err := C.acl_get_entry(acl.acl, C.ACL_NEXT_ENTRY, &e); err != nil {
+			return err
+		} else if r == 0 {
+			// return on drained acl
+			return nil
+		}
+
+		var (
+			q int
+			t C.acl_tag_t
+		)
+
+		// get current entry tag type
+		if _, err := C.acl_get_tag_type(e, &t); err != nil {
+			return err
+		}
+
+		// get current entry qualifier
+		if rq, err := C.acl_get_qualifier(e); err != nil {
+			// neither ACL_USER nor ACL_GROUP
+			if errors.Is(err, syscall.EINVAL) {
+				continue
+			}
+
+			return err
+		} else {
+			q = *(*int)(rq)
+			C.acl_free(rq)
+		}
+
+		// delete on match
+		if t == tt && q == tq {
+			_, err := C.acl_delete_entry(acl.acl, e)
+			return err
+		}
+	}
+}
+
+// Update replaces ACL_USER entry with qualifier uid.
+func Update(name string, uid int, perms ...Perm) error {
+	// read acl from file
+	a, err := getFile(name, TypeAccess)
+	if err != nil {
+		return err
+	}
+	// free acl on return if get is successful
+	defer a.free()
+
+	// remove existing entry
+	if err = a.removeEntry(User, uid); err != nil {
+		return err
+	}
+
+	// create new entry if perms are passed
+	if len(perms) > 0 {
+		// create new acl entry
+		var e C.acl_entry_t
+		if _, err = C.acl_create_entry(&a.acl, &e); err != nil {
+			return err
+		}
+
+		// get perm set of new entry
+		var p C.acl_permset_t
+		if _, err = C.acl_get_permset(e, &p); err != nil {
+			return err
+		}
+
+		// add target perms
+		for _, perm := range perms {
+			if _, err = C.acl_add_perm(p, C.acl_perm_t(perm)); err != nil {
+				return err
+			}
+		}
+
+		// set perm set to new entry
+		if _, err = C.acl_set_permset(e, p); err != nil {
+			return err
+		}
+
+		// set user tag to new entry
+		if _, err = C.acl_set_tag_type(e, User); err != nil {
+			return err
+		}
+
+		// set qualifier (uid) to new entry
+		if _, err = C.acl_set_qualifier(e, unsafe.Pointer(&uid)); err != nil {
+			return err
 		}
 	}
-	return string(s)
+
+	// calculate mask after update
+	if _, err = C.acl_calc_mask(&a.acl); err != nil {
+		return err
+	}
+
+	// write acl to file
+	return a.setFile(name, TypeAccess)
 }