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/**************************************************************************/
/* */
/* OCaml */
/* */
/* David Allsopp, MetaStack Solutions Ltd. */
/* */
/* Copyright 2015 MetaStack Solutions Ltd. */
/* */
/* All rights reserved. This file is distributed under the terms of */
/* the GNU Lesser General Public License version 2.1, with the */
/* special exception on linking described in the file LICENSE. */
/* */
/**************************************************************************/
#define CAML_INTERNALS
/*
* Windows Vista functions enabled
*/
#undef _WIN32_WINNT
#define _WIN32_WINNT 0x0600
#include <caml/mlvalues.h>
#include <caml/memory.h>
#include <caml/alloc.h>
#include <caml/fail.h>
#include <caml/signals.h>
#include <caml/osdeps.h>
#include <caml/platform.h>
#include "caml/unixsupport.h"
#ifndef SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE
#define SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE (0x2)
#endif
static _Atomic DWORD additional_symlink_flags = -1;
// Developer Mode allows the creation of symlinks without elevation - see
// https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createsymboliclinkw
static BOOL IsDeveloperModeEnabled(void)
{
HKEY hKey;
LSTATUS status;
DWORD developerModeRegistryValue, dwordSize = sizeof(DWORD);
status = RegOpenKeyExW(
HKEY_LOCAL_MACHINE,
L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\AppModelUnlock",
0,
KEY_READ | KEY_WOW64_64KEY,
&hKey
);
if (status != ERROR_SUCCESS) {
return FALSE;
}
status = RegQueryValueExW(
hKey,
L"AllowDevelopmentWithoutDevLicense",
NULL,
NULL,
(LPBYTE)&developerModeRegistryValue,
&dwordSize
);
RegCloseKey(hKey);
if (status != ERROR_SUCCESS) {
return FALSE;
}
return developerModeRegistryValue != 0;
}
CAMLprim value caml_unix_symlink(value to_dir, value osource, value odest)
{
CAMLparam3(to_dir, osource, odest);
DWORD flags, additional_flags;
BOOLEAN result;
LPWSTR source;
LPWSTR dest;
caml_unix_check_path(osource, "symlink");
caml_unix_check_path(odest, "symlink");
additional_flags = atomic_load_relaxed(&additional_symlink_flags);
if (additional_flags == -1) {
additional_flags = IsDeveloperModeEnabled() ?
SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE : 0;
atomic_store_relaxed(&additional_symlink_flags, additional_flags);
}
flags =
(Bool_val(to_dir) ? SYMBOLIC_LINK_FLAG_DIRECTORY : 0) | additional_flags;
/* Copy source and dest outside the OCaml heap */
source = caml_stat_strdup_to_utf16(String_val(osource));
dest = caml_stat_strdup_to_utf16(String_val(odest));
caml_enter_blocking_section();
result = CreateSymbolicLink(dest, source, flags);
caml_leave_blocking_section();
caml_stat_free(source);
caml_stat_free(dest);
if (!result) {
caml_win32_maperr(GetLastError());
caml_uerror("symlink", odest);
}
CAMLreturn(Val_unit);
}
#define luid_eq(l, r) (l.LowPart == r.LowPart && l.HighPart == r.HighPart)
CAMLprim value caml_unix_has_symlink(value unit)
{
CAMLparam1(unit);
HANDLE hProcess = GetCurrentProcess();
BOOL result = FALSE;
if (IsDeveloperModeEnabled()) {
CAMLreturn(Val_true);
}
if (OpenProcessToken(hProcess, TOKEN_READ, &hProcess)) {
LUID seCreateSymbolicLinkPrivilege;
if (LookupPrivilegeValue(NULL,
SE_CREATE_SYMBOLIC_LINK_NAME,
&seCreateSymbolicLinkPrivilege)) {
DWORD length;
if (!GetTokenInformation(hProcess, TokenPrivileges, NULL, 0, &length)) {
if (GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
TOKEN_PRIVILEGES* privileges = (TOKEN_PRIVILEGES*)caml_stat_alloc(length);
if (GetTokenInformation(hProcess,
TokenPrivileges,
privileges,
length,
&length)) {
DWORD count = privileges->PrivilegeCount;
if (count) {
LUID_AND_ATTRIBUTES* privs = privileges->Privileges;
while (count-- && !(result = luid_eq(privs->Luid, seCreateSymbolicLinkPrivilege)))
privs++;
}
}
caml_stat_free(privileges);
}
}
}
CloseHandle(hProcess);
}
CAMLreturn(Val_bool(result));
}
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