Re: a problem with git describe

["Carlo Marcelo Arenas Belón" <carenas@gmail.com>]

On Mon, Apr 25, 2022 at 12:02:45AM -0700, Carlo Marcelo Arenas Belón wrote:
> On Sun, Apr 24, 2022 at 11:39:27PM -0700, Junio C Hamano wrote:
> > Carlo Marcelo Arenas Belón <carenas@gmail.com> writes:
> > 
> > > At that point, though you might as well excempt root from this check
> > 
> > But "root" or any higher-valued account is what needs this kind of
> > protection the most, no?
> 
> correct, and I didn't meant to excempt root from the protection, but
> from the check that requires that the config file ownership matches.
> 
> if the config file is owned by root, we already lost, regardless of what
> uid git is running as.

apologies for my confusing english, hopefully this C is clearer

diff --git a/git-compat-util.h b/git-compat-util.h
index 58fd813bd01..6a385be7d1d 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -440,9 +440,19 @@ static inline int git_offset_1st_component(const char *path)
 static inline int is_path_owned_by_current_uid(const char *path)
 {
 	struct stat st;
+	uid_t euid;
+
 	if (lstat(path, &st))
 		return 0;
-	return st.st_uid == geteuid();
+
+	euid = geteuid();
+	if (!euid && st.st_uid && isatty(0)) {
+		struct stat ttyst;
+		if (!stat(ttyname(0), &ttyst))
+			euid = ttyst.st_uid;
+	}
+
+	return st.st_uid == euid;
 }
 
 #define is_path_owned_by_current_user is_path_owned_by_current_uid

it uses stdin instead not to fall in the issue that was raised by
Gábor, but I am affraid that it might need to check all stdnandles for
a valid tty to be safe, and it looking even more complex.

Carlo