[kbd] [PATCH] vlock: allow sudo user to unlock his session

[Mikhail Novosyolov <m.novosyolov@rosalinux.ru>]

https://github.com/legionus/kbd/pull/45


If a non-root user ran sth like "sudo -i" and vlock'ed from inside it,
then that user himself should be able to unlock his console.

[user@HP-Elite-7300 tmp]$ echo $LOGNAME
user
[user@HP-Elite-7300 tmp]$ sudo -i
root@HP-Elite-7300:~# echo $LOGNAME
root
root@HP-Elite-7300:~# echo $SUDO_USER
user
root@HP-Elite-7300:~#

Tested on rosa2019.1 + kbd 2.2.0 + this patch:
[root@rosa-2019 kbd]# su - user
[user@rosa-2019 ~]$ sudo -i
[sudo] password for user:
[root@rosa-2019 ~]# vlock
Данное устройство tty (console) не является виртуальной консолью.
Блокировка console установлена user.
Пароль:
[root@rosa-2019 ~]#
sudo root session was successfully unlocked with user's password.
[root@rosa-2019 ~]# unset SUDO_USER
[root@rosa-2019 ~]# vlock
Данное устройство tty (console) не является виртуальной консолью.
Блокировка console установлена root.
Пароль:
root password is requested without $SUDO_ENV.

Another vlock implementation [1, 2] does not check that UIDs match,
I do not see sense in this check, removing it to make what I want work.

[1] Another vlock implementation: https://github.com/WorMzy/vlock
[2] My similar patch for it: https://github.com/mikhailnov/vlock/commit/ba38d5d563cdfaad3b2f260248b3434c235a7afd
---
 src/vlock/username.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/vlock/username.c b/src/vlock/username.c
index a26a148..4c6d295 100644
--- a/src/vlock/username.c
+++ b/src/vlock/username.c
@@ -40,17 +40,18 @@ get_username(void)
 {
     const char *name;
     struct passwd *pw = 0;
+    char *logname = NULL;
     uid_t uid         = getuid();
 
-    char *logname = getenv("LOGNAME");
+    /* If a non-root runs a sudo session, ask for user's
+     * password to unlock it, not root's password */
+    logname = getenv("SUDO_USER");
+    if (logname == NULL)
+        logname = getenv("LOGNAME");
 
-    if (logname) {
-        pw = getpwnam(logname);
-        /* Ensure uid is same as current. */
-        if (pw && pw->pw_uid != uid)
-            pw = 0;
-    }
-    if (!pw)
+    pw = getpwnam(logname);
+
+    if (!pw && uid)
         pw = getpwuid(uid);
 
     if (!pw)
-- 

Please CC me when replying, I am not subscribed to kbd@lists.altlinux.org
The same patch was submited as a pull request on Github: https://github.com/legionus/kbd/pull/45