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macOS: restrict elevated SetFileOwner to disk device nodes (#1758)

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The privileged CoreService handler for SetFileOwnerRequest passed the
client-supplied path straight to chown() as root with no validation --
unlike the adjacent APFS formatter handler, which strictly validates its
device argument. Every legitimate macOS caller of the elevated
SetFileOwner targets a real disk device node (/dev/[r]diskN[sM]), so a
crafted IPC request, or a symlink planted at the target, could otherwise
make the root process change ownership of an arbitrary path.

Validate the target service-side: require the strict device-path form
already used by the formatter, and lstat() it to confirm a block or
character device (rejecting symlinks rather than following them) before
the chown.

Co-authored-by: Damian Rickard <damian@rickard.us>
This commit is contained in:
damianrickard
2026-06-14 10:31:42 -04:00
committed by GitHub
parent 54a23eeacb
commit 575262a104
1 changed files with 26 additions and 0 deletions
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src/Core/Unix/CoreService.cpp
+26
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@@ -12,6 +12,7 @@
#include "CoreService.h"
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <stdio.h>
#include "Platform/FileStream.h"
@@ -60,6 +61,27 @@ namespace VeraCrypt
|| IsMacOSXDevicePathWithPrefix (path, "/dev/rdisk");
}
// The elevated service runs as root, so it must not be tricked into changing
// ownership of an arbitrary path. Every legitimate macOS caller of the
// elevated SetFileOwner targets a real disk device node (/dev/[r]diskN[sM]),
// so restrict the operation to that. lstat() (not stat) is used so a symlink
// is rejected outright rather than followed, and the st_mode check confirms an
// actual block/character device before the chown.
static void ValidateMacOSXSetFileOwnerTarget (const FilesystemPath &path)
{
const string pathStr = path;
if (!IsMacOSXFormatterDevicePath (pathStr))
throw ParameterIncorrect (SRC_POS);
struct stat sb;
if (lstat (pathStr.c_str(), &sb) != 0)
throw ParameterIncorrect (SRC_POS);
if (!S_ISBLK (sb.st_mode) && !S_ISCHR (sb.st_mode))
throw ParameterIncorrect (SRC_POS);
}
static list <string> BuildMacOSXAPFSFormatterArguments (const ExecuteMacOSXAPFSFormatterRequest &request)
{
if (!IsMacOSXFormatterDevicePath (request.Device))
@@ -292,6 +314,10 @@ namespace VeraCrypt
if (!coreUnix)
throw ParameterIncorrect (SRC_POS);
#ifdef TC_MACOSX
// Restrict the root-privileged chown to real disk device nodes.
ValidateMacOSXSetFileOwnerTarget (setFileOwnerRequest->Path);
#endif
coreUnix->SetFileOwner (setFileOwnerRequest->Path, setFileOwnerRequest->Owner);
SetFileOwnerResponse().Serialize (outputStream);
continue;