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From c8b74ac5cf508c7bcec92d197880043af1d2bad7 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Tue, 9 Oct 2018 22:23:41 +0200
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Subject: [PATCH] logind: validate /run/user/1000 before we set it
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Let's be safe than sorry, in particular as logind doesn't set it up
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anymore, but user-runtime-dir@.service does, and logind doesn't really
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track success of that.
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(cherry picked from commit b92171124819305985ed292cc472f6668a027425)
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Related: #1642460
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---
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src/login/pam_systemd.c | 48 +++++++++++++++++++++++++++++++++++------
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1 file changed, 41 insertions(+), 7 deletions(-)
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diff --git a/src/login/pam_systemd.c b/src/login/pam_systemd.c
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index b2b62540bb..64e1b4d1bf 100644
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--- a/src/login/pam_systemd.c
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+++ b/src/login/pam_systemd.c
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@@ -319,6 +319,36 @@ static int update_environment(pam_handle_t *handle, const char *key, const char
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return r;
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}
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+static bool validate_runtime_directory(pam_handle_t *handle, const char *path, uid_t uid) {
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+ struct stat st;
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+
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+ assert(path);
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+
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+ /* Just some extra paranoia: let's not set $XDG_RUNTIME_DIR if the directory we'd set it to isn't actually set
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+ * up properly for us. */
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+
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+ if (lstat(path, &st) < 0) {
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+ pam_syslog(handle, LOG_ERR, "Failed to stat() runtime directory '%s': %s", path, strerror(errno));
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+ goto fail;
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+ }
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+
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+ if (!S_ISDIR(st.st_mode)) {
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+ pam_syslog(handle, LOG_ERR, "Runtime directory '%s' is not actually a directory.", path);
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+ goto fail;
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+ }
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+
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+ if (st.st_uid != uid) {
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+ pam_syslog(handle, LOG_ERR, "Runtime directory '%s' is not owned by UID " UID_FMT ", as it should.", path, uid);
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+ goto fail;
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+ }
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+
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+ return true;
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+
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+fail:
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+ pam_syslog(handle, LOG_WARNING, "Not setting $XDG_RUNTIME_DIR, as the directory is not in order.");
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+ return false;
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+}
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+
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_public_ PAM_EXTERN int pam_sm_open_session(
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pam_handle_t *handle,
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int flags,
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@@ -377,10 +407,12 @@ _public_ PAM_EXTERN int pam_sm_open_session(
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if (asprintf(&rt, "/run/user/"UID_FMT, pw->pw_uid) < 0)
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return PAM_BUF_ERR;
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- r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", rt, 0);
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- if (r != PAM_SUCCESS) {
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- pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
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- return r;
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+ if (validate_runtime_directory(handle, rt, pw->pw_uid)) {
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+ r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", rt, 0);
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+ if (r != PAM_SUCCESS) {
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+ pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
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+ return r;
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+ }
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}
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r = export_legacy_dbus_address(handle, pw->pw_uid, rt);
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@@ -584,9 +616,11 @@ _public_ PAM_EXTERN int pam_sm_open_session(
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* in privileged apps clobbering the runtime directory
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* unnecessarily. */
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- r = update_environment(handle, "XDG_RUNTIME_DIR", runtime_path);
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- if (r != PAM_SUCCESS)
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- return r;
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+ if (validate_runtime_directory(handle, runtime_path, pw->pw_uid)) {
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+ r = update_environment(handle, "XDG_RUNTIME_DIR", runtime_path);
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+ if (r != PAM_SUCCESS)
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+ return r;
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+ }
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r = export_legacy_dbus_address(handle, pw->pw_uid, runtime_path);
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if (r != PAM_SUCCESS)
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