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mingw: special-case administrators even more

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The check for dubious ownership has one particular quirk on Windows: if
running as an administrator, files owned by the Administrators _group_
are considered owned by the user.

The rationale for that is: When running in elevated mode, Git creates
files that aren't owned by the individual user but by the Administrators
group.

There is yet another quirk, though: The check I introduced to determine
whether the current user is an administrator uses the
`CheckTokenMembership()` function with the current process token. And
that check only succeeds when running in elevated mode!

Let's be a bit more lenient here and look harder whether the current
user is an administrator. We do this by looking for a so-called "linked
token". That token exists when administrators run in non-elevated mode,
and can be used to create a new process in elevated mode. And feeding
_that_ token to the `CheckTokenMembership()` function succeeds!

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Johannes Schindelin
2025-03-25 10:38:29 +00:00
committed by Junio C Hamano
parent 683c54c999
commit 03a4e46d12
1 changed files with 28 additions and 11 deletions
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39
compat/mingw.c
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@@ -2826,31 +2826,44 @@ static void setup_windows_environment(void)
} }
} }
static PSID get_current_user_sid(void) static void get_current_user_sid(PSID *sid, HANDLE *linked_token)
{ {
HANDLE token; HANDLE token;
DWORD len = 0; DWORD len = 0;
PSID result = NULL; TOKEN_ELEVATION_TYPE elevationType;
DWORD size;
*sid = NULL;
*linked_token = NULL;
if (!OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &token)) if (!OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &token))
return NULL; return;
if (!GetTokenInformation(token, TokenUser, NULL, 0, &len)) { if (!GetTokenInformation(token, TokenUser, NULL, 0, &len)) {
TOKEN_USER *info = xmalloc((size_t)len); TOKEN_USER *info = xmalloc((size_t)len);
if (GetTokenInformation(token, TokenUser, info, len, &len)) { if (GetTokenInformation(token, TokenUser, info, len, &len)) {
len = GetLengthSid(info->User.Sid); len = GetLengthSid(info->User.Sid);
result = xmalloc(len); *sid = xmalloc(len);
if (!CopySid(len, result, info->User.Sid)) { if (!CopySid(len, *sid, info->User.Sid)) {
error(_("failed to copy SID (%ld)"), error(_("failed to copy SID (%ld)"),
GetLastError()); GetLastError());
FREE_AND_NULL(result); FREE_AND_NULL(*sid);
} }
} }
FREE_AND_NULL(info); FREE_AND_NULL(info);
} }
CloseHandle(token);
return result; if (GetTokenInformation(token, TokenElevationType, &elevationType, sizeof(elevationType), &size) &&
elevationType == TokenElevationTypeLimited) {
/*
* The current process is run by a member of the Administrators
* group, but is not running elevated.
*/
if (!GetTokenInformation(token, TokenLinkedToken, linked_token, sizeof(*linked_token), &size))
linked_token = NULL; /* there is no linked token */
}
CloseHandle(token);
} }
static BOOL user_sid_to_user_name(PSID sid, LPSTR *str) static BOOL user_sid_to_user_name(PSID sid, LPSTR *str)
@@ -2931,18 +2944,22 @@ int is_path_owned_by_current_sid(const char *path, struct strbuf *report)
else if (sid && IsValidSid(sid)) { else if (sid && IsValidSid(sid)) {
/* Now, verify that the SID matches the current user's */ /* Now, verify that the SID matches the current user's */
static PSID current_user_sid; static PSID current_user_sid;
static HANDLE linked_token;
BOOL is_member; BOOL is_member;
if (!current_user_sid) if (!current_user_sid)
current_user_sid = get_current_user_sid(); get_current_user_sid(&current_user_sid, &linked_token);
if (current_user_sid && if (current_user_sid &&
IsValidSid(current_user_sid) && IsValidSid(current_user_sid) &&
EqualSid(sid, current_user_sid)) EqualSid(sid, current_user_sid))
result = 1; result = 1;
else if (IsWellKnownSid(sid, WinBuiltinAdministratorsSid) && else if (IsWellKnownSid(sid, WinBuiltinAdministratorsSid) &&
CheckTokenMembership(NULL, sid, &is_member) && ((CheckTokenMembership(NULL, sid, &is_member) &&
is_member) is_member) ||
(linked_token &&
CheckTokenMembership(linked_token, sid, &is_member) &&
is_member)))
/* /*
* If owned by the Administrators group, and the * If owned by the Administrators group, and the
* current user is an administrator, we consider that * current user is an administrator, we consider that