libstore/local-store: remove xattrs all the time

xattrs scrubbing was gated behind Linux platforms, but Lix can safely
assume that POSIX APIs are available.

macOS implements these APIs modulo some creative ideas.

Fixes #1008.

Change-Id: I1566df4923bf24092d3fd32ccf6a96e4256e87b2
Signed-off-by: Raito Bezarius <raito@lix.systems>

lix/libstore/local-store.cc

@@ -544,7 +544,6 @@ static void canonicalisePathMetaData_(
         return;
     }
 
-#if __linux__
     /* Remove extended attributes / ACLs. */
     ssize_t eaSize = sys::llistxattr(path, nullptr, 0);
 
@@ -573,8 +572,7 @@ static void canonicalisePathMetaData_(
             (void) sys::chmod(path, st.st_mode);
             resetMode = false;
         }
-     }
-#endif
+    }
 
     inodesSeen.insert(Inode(st.st_dev, st.st_ino));
 

lix/libstore/settings/ignored-acls.md

@@ -1,9 +1,14 @@
 ---
 name: ignored-acls
 internalName: ignoredAcls
-platforms: [linux]
 type: StringSet
-default: [security.csm, security.selinux, system.nfs4_acl]
+defaultExpr: |
+  #if __linux__
+    {"security.csm", "security.selinux", "system.nfs4_acl"}
+  #else
+    {}
+  #endif
+defaultText: '*Linux:* `security.csm, security.selinux, system.nfs4_acl`, *other platforms:* nothing.'
 ---
 A list of ACLs that should be ignored, normally Lix attempts to
 remove all ACLs from files and directories in the Nix store, but

lix/libutil/c-calls.cc

@@ -187,6 +187,23 @@ ssize_t getxattr(const std::string & path, const std::string & name, void * valu
 }
 #endif
 
+#if __APPLE__
+ssize_t llistxattr(const std::string & path, char * list, size_t size)
+{
+    return ::listxattr(requireCString(path), list, size, XATTR_NOFOLLOW);
+}
+
+ssize_t lremovexattr(const std::string & path, const std::string & name)
+{
+    return ::removexattr(requireCString(path), requireCString(name), XATTR_NOFOLLOW);
+}
+
+ssize_t getxattr(const std::string & path, const std::string & name, void * value, size_t size)
+{
+    return ::getxattr(requireCString(path), requireCString(name), value, size, 0, XATTR_NOFOLLOW);
+}
+#endif
+
 int chdir(const std::string & path)
 {
     return ::chdir(requireCString(path));

lix/libutil/c-calls.hh

@@ -113,6 +113,7 @@ int mount(
     unsigned long mountflags,
     const void * data
 );
+#endif
 
 [[nodiscard]]
 ssize_t llistxattr(const std::string & path, char * list, size_t size);
@@ -122,7 +123,6 @@ ssize_t lremovexattr(const std::string & path, const std::string & name);
 
 [[nodiscard]]
 ssize_t getxattr(const std::string & path, const std::string & name, void * value, size_t size);
-#endif
 
 [[nodiscard]]
 int chdir(const std::string & path);