mirror of
https://github.com/Droid-Deck/DroidDeck.git
synced 2026-11-11 02:51:10 +00:00
The412Banner
ecbce4c8d3
The session's proot runs with -i <app uid>, and the rootfs names that uid root, so the client calls itself root while geteuid() returns the app's uid. The read-only retry required geteuid() == 0 and never ran: the Proton Experimental (ARM64) update still failed with Missing file permissions on wineopenxr.dll (2026-09-26 16:07, 2,471 read-only files). Also recognise the client by the path it was started by: the kernel's /proc/self/exe names proot's loader for every process in the session.
83 lines
3.2 KiB
C
83 lines
3.2 KiB
C
/*
|
|
* Root's way past a read-only file, for the Steam client.
|
|
*
|
|
* The client runs as "root" inside the session - the rootfs names the app's own uid root, and
|
|
* proot (-i) shows it that uid - but the kernel treats it as the ordinary user it is. The client
|
|
* leaves many content files read-only (r-x------,
|
|
* ~290 files of Proton Experimental (ARM64) alone), and when an update later rewrites one of them
|
|
* it opens the file for writing expecting root's permission to override the mode. The kernel
|
|
* refuses (EACCES), the client reports "Missing file permissions" and cancels the update
|
|
* (2026-09-26: Proton Experimental (ARM64), "CFileWriter: errno: 13 ... wineopenxr.dll").
|
|
*
|
|
* So for the client's own processes, a refused write-open of a file this user owns is answered the
|
|
* way root's would be: the owner's write bit is added - to the file, or to the directory a new
|
|
* file is being created in - and the open is tried once more. chmod only succeeds on what the app
|
|
* owns, so nothing it could not already change is touched. Games, Wine and everything else keep
|
|
* ordinary permissions: only the processes started from the client's own directories take this.
|
|
*/
|
|
#define _GNU_SOURCE
|
|
#include <errno.h>
|
|
#include <fcntl.h>
|
|
#include <limits.h>
|
|
#include <string.h>
|
|
#include <sys/stat.h>
|
|
#include <unistd.h>
|
|
|
|
static int in_steam_dirs(const char *path) {
|
|
return path != NULL && (strstr(path, "/Steam/steamrtarm64/") != NULL
|
|
|| strstr(path, "/Steam/ubuntu12_64/") != NULL || strstr(path, "/Steam/linuxarm64/") != NULL);
|
|
}
|
|
|
|
/*
|
|
* The client and its helpers run from the Steam root's platform directories. The kernel's
|
|
* /proc/self/exe names proot's loader for every process in the session, so the program's own
|
|
* name - the path it was started by - is asked as well.
|
|
*/
|
|
static int is_steam_client(void) {
|
|
static int cached = -1;
|
|
char exe[PATH_MAX];
|
|
ssize_t n;
|
|
|
|
if (cached >= 0) return cached;
|
|
n = readlink("/proc/self/exe", exe, sizeof(exe) - 1);
|
|
if (n > 0) exe[n] = '\0';
|
|
cached = (n > 0 && in_steam_dirs(exe)) || in_steam_dirs(program_invocation_name);
|
|
return cached;
|
|
}
|
|
|
|
static int grant_owner_write(int dirfd, const char *path) {
|
|
struct stat st;
|
|
|
|
if (fstatat(dirfd, path, &st, 0) != 0 || (st.st_mode & S_IWUSR)) return 0;
|
|
return fchmodat(dirfd, path, (st.st_mode & 07777) | S_IWUSR, 0) == 0;
|
|
}
|
|
|
|
/*
|
|
* After an open refused with EACCES: returns 1 when a write bit was added and the open is worth
|
|
* one more try. errno is left as the open set it.
|
|
*/
|
|
__attribute__((visibility("hidden")))
|
|
int bl_writable_retry(int dirfd, const char *path, int flags) {
|
|
int saved = errno;
|
|
int granted = 0;
|
|
char parent[PATH_MAX];
|
|
const char *slash;
|
|
|
|
if (saved != EACCES || path == NULL || (flags & O_ACCMODE) == O_RDONLY || !is_steam_client()) return 0;
|
|
if (faccessat(dirfd, path, F_OK, 0) == 0) {
|
|
granted = grant_owner_write(dirfd, path);
|
|
} else if (flags & O_CREAT) {
|
|
/* A new file in a read-only directory. */
|
|
slash = strrchr(path, '/');
|
|
if (slash == NULL) {
|
|
granted = grant_owner_write(dirfd, ".");
|
|
} else if ((size_t) (slash - path) < sizeof(parent)) {
|
|
memcpy(parent, path, slash - path);
|
|
parent[slash - path] = '\0';
|
|
granted = grant_owner_write(dirfd, parent[0] ? parent : "/");
|
|
}
|
|
}
|
|
errno = saved;
|
|
return granted;
|
|
}
|