From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 9 Jan 2025 22:57:32 +0000 (+0100)
Subject: login: actually honour $HOME for chdir()
X-Git-Tag: v2.42-start~95^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2e269ff4bc32cb61e1d576d4f932b4027f5bc2c8;p=thirdparty%2Futil-linux.git

login: actually honour $HOME for chdir()

When login is almost done it chdir()'s into the user's home directory.
It currently uses pwd->pw_dir, i.e the home dir actually assigned to the
user.

OTOH it explicitly allows overriding HOME (see comment in
init_environ()), and explicitly imports PAM's env vars (which quite
possibly contain $HOME) into its env block.

This patch makes sure that HOME is *properly* overridable via the env
var and via PAM: it actually honours it for the chdir().

(Background: I am working on a PAM module that under some conditions
would like to redirect the home dir to some other dir, and while I can
nicely set $HOME from the PAM module, it has not as much as effect as I
wish, because whie the rest of userspace respects it login so far didn't
and leaves the user in the wrong dir).
---

diff --git a/include/logindefs.h b/include/logindefs.h
index fa6aa2f07..24732ca70 100644
--- a/include/logindefs.h
+++ b/include/logindefs.h
@@ -30,6 +30,6 @@ extern const char *getlogindefs_str(const char *name, const char *dflt);
 extern void free_getlogindefs_data(void);
 extern int logindefs_setenv(const char *name, const char *conf, const char *dflt);
 extern int effective_access(const char *path, int mode);
-extern int get_hushlogin_status(struct passwd *pwd, int force_check);
+extern int get_hushlogin_status(struct passwd *pwd, const char *override_home, int force_check);
 
 #endif /* UTIL_LINUX_LOGINDEFS_H */
diff --git a/lib/logindefs.c b/lib/logindefs.c
index 5f76ebd0f..7b6959921 100644
--- a/lib/logindefs.c
+++ b/lib/logindefs.c
@@ -467,7 +467,7 @@ int effective_access(const char *path, int mode)
  * BSD setreuid().
  */
 
-int get_hushlogin_status(struct passwd *pwd, int force_check)
+int get_hushlogin_status(struct passwd *pwd, const char *override_home, int force_check)
 {
 	const char *files[] = { _PATH_HUSHLOGINS, _PATH_HUSHLOGIN, NULL };
 	const char *file;
@@ -520,7 +520,7 @@ int get_hushlogin_status(struct passwd *pwd, int force_check)
 		if (strlen(pwd->pw_dir) + strlen(file) + 2 > sizeof(buf))
 			continue;
 
-		if (snprintf(buf, sizeof(buf), "%s/%s", pwd->pw_dir, file) < 0)
+		if (snprintf(buf, sizeof(buf), "%s/%s", override_home ?: pwd->pw_dir, file) < 0)
 			continue;
 
 		if (force_check) {
diff --git a/login-utils/login.c b/login-utils/login.c
index 1d7dd3a67..321f9d6ce 100644
--- a/login-utils/login.c
+++ b/login-utils/login.c
@@ -1493,7 +1493,7 @@ int main(int argc, char **argv)
 		}
 	}
 
-	cxt.quiet = get_hushlogin_status(pwd, 1) == 1 ? 1 : 0;
+	cxt.quiet = get_hushlogin_status(pwd, pam_getenv(cxt.pamh, "HOME"), 1) == 1 ? 1 : 0;
 
 	/*
 	 * Open PAM session (after successful authentication and account check).
@@ -1543,8 +1543,9 @@ int main(int argc, char **argv)
 	}
 
 	/* wait until here to change directory! */
-	if (chdir(pwd->pw_dir) < 0) {
-		warn(_("%s: change directory failed"), pwd->pw_dir);
+	const char *home = getenv("HOME") ?: pwd->pw_dir;
+	if (chdir(home) < 0) {
+		warn(_("%s: change directory failed"), home);
 
 		if (!getlogindefs_bool("DEFAULT_HOME", 1))
 			exit(0);
diff --git a/login-utils/lslogins.c b/login-utils/lslogins.c
index 7c1ba6893..ebfdf6a79 100644
--- a/login-utils/lslogins.c
+++ b/login-utils/lslogins.c
@@ -904,7 +904,7 @@ static struct lslogins_user *get_user_info(struct lslogins_control *ctl, const c
 			}
 			break;
 		case COL_HUSH_STATUS:
-			user->hushed = get_hushlogin_status(pwd, 0);
+			user->hushed = get_hushlogin_status(pwd, /* override_home= */ NULL, 0);
 			if (user->hushed == -1)
 				user->hushed = STATUS_UNKNOWN;
 			break;