slackware-current/testing/source/vtown/kde/patch/sddm/sddm_honor-PAM-supplemental-groups-v2.patch

From 75e6e00d9e1ecf25e3a9c8332530a1e40d737cdb Mon Sep 17 00:00:00 2001
From: "J. Konrad Tegtmeier-Rottach" <jktr@0x16.de>
Date: Thu, 9 May 2019 03:06:48 +0200
Subject: [PATCH] Honor PAM's supplemental groups (v2) (#834, #1159)

This moves the supplemental group initialization step from
UserSession.cpp to the Backend system, so that the Pam Backend can
inject additional supplemental groups via modules like pam_group.so.

pam_setcred(3) assumes that it operates on an already initialized
supplemental group list. However, PamBackend calls
pam_setcred(PAM_ESTABLISH_CRED) earlier, at the start
PamBackend::openSession, so a pam_setcred(PAM_REINITIALIZE_CRED) call
must be issued to repeat the injection of PAM's supplemental groups.
---
 src/helper/Backend.cpp            |  5 +++++
 src/helper/Backend.h              |  3 +++
 src/helper/HelperApp.cpp          |  4 ++++
 src/helper/HelperApp.h            |  1 +
 src/helper/UserSession.cpp        | 13 ++++++++-----
 src/helper/backend/PamBackend.cpp | 18 ++++++++++++++++++
 src/helper/backend/PamBackend.h   |  2 ++
 7 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/src/helper/Backend.cpp b/src/helper/Backend.cpp
index d6bb4d0a..35ae2bdf 100644
--- a/src/helper/Backend.cpp
+++ b/src/helper/Backend.cpp
@@ -29,6 +29,7 @@
 #include <QtCore/QProcessEnvironment>
 
 #include <pwd.h>
+#include <grp.h>
 
 namespace SDDM {
     Backend::Backend(HelperApp* parent)
@@ -79,4 +80,8 @@ namespace SDDM {
     bool Backend::closeSession() {
         return true;
     }
+
+    bool Backend::setupSupplementalGroups(struct passwd *pw) {
+        return !initgroups(pw->pw_name, pw->pw_gid);
+    }
 }
diff --git a/src/helper/Backend.h b/src/helper/Backend.h
index b790e001..3caf1592 100644
--- a/src/helper/Backend.h
+++ b/src/helper/Backend.h
@@ -22,6 +22,7 @@
 #define BACKEND_H
 
 #include <QtCore/QObject>
+#include <pwd.h>
 
 namespace SDDM {
     class HelperApp;
@@ -38,6 +39,8 @@ namespace SDDM {
         void setAutologin(bool on = true);
         void setGreeter(bool on = true);
 
+        virtual bool setupSupplementalGroups(struct passwd *pw);
+
     public slots:
         virtual bool start(const QString &user = QString()) = 0;
         virtual bool authenticate() = 0;
diff --git a/src/helper/HelperApp.cpp b/src/helper/HelperApp.cpp
index cad93bd8..d0891d75 100644
--- a/src/helper/HelperApp.cpp
+++ b/src/helper/HelperApp.cpp
@@ -253,6 +253,10 @@ namespace SDDM {
         return m_session;
     }
 
+    Backend *HelperApp::backend() {
+        return m_backend;
+    }
+
     const QString& HelperApp::user() const {
         return m_user;
     }
diff --git a/src/helper/HelperApp.h b/src/helper/HelperApp.h
index 3742df12..cb5959a7 100644
--- a/src/helper/HelperApp.h
+++ b/src/helper/HelperApp.h
@@ -39,6 +39,7 @@ namespace SDDM {
         virtual ~HelperApp();
 
         UserSession *session();
+        Backend *backend();
         const QString &user() const;
         const QString &cookie() const;
 
diff --git a/src/helper/UserSession.cpp b/src/helper/UserSession.cpp
index f71fd358..62fd4d70 100644
--- a/src/helper/UserSession.cpp
+++ b/src/helper/UserSession.cpp
@@ -19,6 +19,7 @@
  *
  */
 
+#include "Backend.h"
 #include "Configuration.h"
 #include "UserSession.h"
 #include "HelperApp.h"
@@ -129,7 +130,8 @@ namespace SDDM {
 #endif
 
         // switch user
-        const QByteArray username = qobject_cast<HelperApp*>(parent())->user().toLocal8Bit();
+        HelperApp* app = qobject_cast<HelperApp*>(parent());
+        const QByteArray username = app->user().toLocal8Bit();
         struct passwd pw;
         struct passwd *rpw;
         long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
@@ -146,12 +148,13 @@ namespace SDDM {
                 qCritical() << "getpwnam_r(" << username << ") failed with error: " << strerror(err);
             exit(Auth::HELPER_OTHER_ERROR);
         }
-        if (setgid(pw.pw_gid) != 0) {
-            qCritical() << "setgid(" << pw.pw_gid << ") failed for user: " << username;
+
+        if (!app->backend()->setupSupplementalGroups(&pw)) {
+            qCritical() << "failed to set up supplemental groups for user: " << username;
             exit(Auth::HELPER_OTHER_ERROR);
         }
-        if (initgroups(pw.pw_name, pw.pw_gid) != 0) {
-            qCritical() << "initgroups(" << pw.pw_name << ", " << pw.pw_gid << ") failed for user: " << username;
+        if (setgid(pw.pw_gid) != 0) {
+            qCritical() << "setgid(" << pw.pw_gid << ") failed for user: " << username;
             exit(Auth::HELPER_OTHER_ERROR);
         }
         if (setuid(pw.pw_uid) != 0) {
diff --git a/src/helper/backend/PamBackend.cpp b/src/helper/backend/PamBackend.cpp
index f86d77d6..cccfa258 100644
--- a/src/helper/backend/PamBackend.cpp
+++ b/src/helper/backend/PamBackend.cpp
@@ -289,6 +289,24 @@ namespace SDDM {
         return QString::fromLocal8Bit((const char*) m_pam->getItem(PAM_USER));
     }
 
+    bool PamBackend::setupSupplementalGroups(struct passwd *pw) {
+        if (!Backend::setupSupplementalGroups(pw))
+            return false;
+
+        // pam_setcred(3) may inject additional groups into the user's
+        // list of supplemental groups, and assumes that the user's
+        // supplemental groups have already been initialized before
+        // its invocation. Since pam_setcred was already called at the
+        // start of openSession, we need to repeat this step here as
+        // the user's groups have only just now been initialized.
+
+        if (!m_pam->setCred(PAM_REINITIALIZE_CRED)) {
+            m_app->error(m_pam->errorString(), Auth::ERROR_AUTHENTICATION);
+            return false;
+        }
+        return true;
+    }
+
     int PamBackend::converse(int n, const struct pam_message **msg, struct pam_response **resp) {
         qDebug() << "[PAM] Conversation with" << n << "messages";
 
diff --git a/src/helper/backend/PamBackend.h b/src/helper/backend/PamBackend.h
index 4c8b4b35..5b079099 100644
--- a/src/helper/backend/PamBackend.h
+++ b/src/helper/backend/PamBackend.h
@@ -28,6 +28,7 @@
 #include <QtCore/QObject>
 
 #include <security/pam_appl.h>
+#include <pwd.h>
 
 namespace SDDM {
     class PamHandle;
@@ -61,6 +62,7 @@ namespace SDDM {
         explicit PamBackend(HelperApp *parent);
         virtual ~PamBackend();
         int converse(int n, const struct pam_message **msg, struct pam_response **resp);
+        virtual bool setupSupplementalGroups(struct passwd *pw);
 
     public slots:
         virtual bool start(const QString &user = QString());