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From 2f0a18b499b9b0e1afbdab8a8bb31d38f2acc6d8 Mon Sep 17 00:00:00 2001
From: Jakub Filak <jfilak@redhat.com>
Date: Fri, 17 Apr 2015 16:06:33 +0200
Subject: [ABRT PATCH] ccpp: emulate selinux for creation of compat cores

This issue was discovered by Florian Weimer of Red Hat Product Security.

http://article.gmane.org/gmane.comp.security.selinux/21842

v2: use the _raw interface and do the preparation steps as root
v3: don't fail if SELinux is disabled
    https://github.com/abrt/abrt/commit/c4f06d4198658c82550e93bb2617b96022c06cf4#commitcomment-11021276

Signed-off-by: Jakub Filak <jfilak@redhat.com>
---
 configure.ac               |  1 +
 src/hooks/Makefile.am      |  4 ++-
 src/hooks/abrt-hook-ccpp.c | 85 ++++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 86 insertions(+), 4 deletions(-)

diff --git a/configure.ac b/configure.ac
index 9ff616d..6c6d2e8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -106,6 +106,7 @@ PKG_CHECK_MODULES([LIBREPORT_GTK], [libreport-gtk])
 PKG_CHECK_MODULES([POLKIT], [polkit-gobject-1])
 PKG_CHECK_MODULES([GIO], [gio-2.0])
 PKG_CHECK_MODULES([SATYR], [satyr])
+PKG_CHECK_MODULES([LIBSELINUX], [libselinux])
 
 PKG_PROG_PKG_CONFIG
 AC_ARG_WITH([systemdsystemunitdir],
diff --git a/src/hooks/Makefile.am b/src/hooks/Makefile.am
index e536089..9a527f4 100644
--- a/src/hooks/Makefile.am
+++ b/src/hooks/Makefile.am
@@ -33,10 +33,12 @@ abrt_hook_ccpp_CPPFLAGS = \
     -DDEFAULT_DUMP_DIR_MODE=$(DEFAULT_DUMP_DIR_MODE) \
     $(GLIB_CFLAGS) \
     $(LIBREPORT_CFLAGS) \
+    $(LIBSELINUX_CFLAGS) \
     -D_GNU_SOURCE
 abrt_hook_ccpp_LDADD = \
     ../lib/libabrt.la \
-    $(LIBREPORT_LIBS)
+    $(LIBREPORT_LIBS) \
+    $(LIBSELINUX_LIBS)
 
 # abrt-merge-pstoreoops
 abrt_merge_pstoreoops_SOURCES = \
diff --git a/src/hooks/abrt-hook-ccpp.c b/src/hooks/abrt-hook-ccpp.c
index 81f9349..00ae621 100644
--- a/src/hooks/abrt-hook-ccpp.c
+++ b/src/hooks/abrt-hook-ccpp.c
@@ -20,6 +20,7 @@
 */
 #include <sys/utsname.h>
 #include "libabrt.h"
+#include <selinux/selinux.h>
 
 #define  DUMP_SUID_UNSAFE 1
 #define  DUMP_SUID_SAFE 2
@@ -286,6 +287,54 @@ static int dump_suid_policy()
     return suid_dump_policy;
 }
 
+/* Computes a security context of new file created by the given process with
+ * pid in the given directory represented by file descriptor.
+ *
+ * On errors returns negative number. Returns 0 if the function succeeds and
+ * computes the context and returns positive number and assigns NULL to newcon
+ * if the security context is not needed (SELinux disabled).
+ */
+static int compute_selinux_con_for_new_file(pid_t pid, int dir_fd, security_context_t *newcon)
+{
+    security_context_t srccon;
+    security_context_t dstcon;
+
+    const int r = is_selinux_enabled();
+    if (r == 0)
+    {
+        *newcon = NULL;
+        return 1;
+    }
+    else if (r == -1)
+    {
+        perror_msg("Couldn't get state of SELinux");
+        return -1;
+    }
+    else if (r != 1)
+        error_msg_and_die("Unexpected SELinux return value: %d", r);
+
+
+    if (getpidcon_raw(pid, &srccon) < 0)
+    {
+        perror_msg("getpidcon_raw(%d)", pid);
+        return -1;
+    }
+
+    if (fgetfilecon_raw(dir_fd, &dstcon) < 0)
+    {
+        perror_msg("getfilecon_raw(%s)", user_pwd);
+        return -1;
+    }
+
+    if (security_compute_create_raw(srccon, dstcon, string_to_security_class("file"), newcon) < 0)
+    {
+        perror_msg("security_compute_create_raw(%s, %s, 'file')", srccon, dstcon);
+        return -1;
+    }
+
+    return 0;
+}
+
 static int open_user_core(uid_t uid, uid_t fsuid, pid_t pid, char **percent_values)
 {
     proc_cwd = open_cwd(pid);
@@ -294,6 +343,14 @@ static int open_user_core(uid_t uid, uid_t fsuid, pid_t pid, char **percent_valu
 
     errno = 0;
 
+    /* http://article.gmane.org/gmane.comp.security.selinux/21842 */
+    security_context_t newcon;
+    if (compute_selinux_con_for_new_file(pid, dirfd(proc_cwd), &newcon) < 0)
+    {
+        log_notice("Not going to create a user core due to SELinux errors");
+        return -1;
+    }
+
     xsetegid(get_fsgid());
     xseteuid(fsuid);
 
@@ -388,10 +445,25 @@ static int open_user_core(uid_t uid, uid_t fsuid, pid_t pid, char **percent_valu
      * (However, see the description of the prctl(2) PR_SET_DUMPABLE operation,
      * and the description of the /proc/sys/fs/suid_dumpable file in proc(5).)
      */
+
+    /* Set SELinux context like kernel when creating core dump file */
+    if (newcon != NULL && setfscreatecon_raw(newcon) < 0)
+    {
+        perror_msg("setfscreatecon_raw(%s)", newcon);
+        return -1;
+    }
+
     struct stat sb;
     errno = 0;
     /* Do not O_TRUNC: if later checks fail, we do not want to have file already modified here */
     int user_core_fd = openat(dirfd(proc_cwd), core_basename, O_WRONLY | O_CREAT | O_NOFOLLOW | g_user_core_flags, 0600); /* kernel makes 0600 too */
+
+    if (newcon != NULL && setfscreatecon_raw(NULL) < 0)
+    {
+        error_msg("setfscreatecon_raw(NULL)");
+        goto user_core_fail;
+    }
+
     xsetegid(0);
     xseteuid(0);
     if (user_core_fd < 0
@@ -404,16 +476,23 @@ static int open_user_core(uid_t uid, uid_t fsuid, pid_t pid, char **percent_valu
             perror_msg("Can't open '%s' at '%s'", core_basename, user_pwd);
         else
             perror_msg("'%s' at '%s' is not a regular file with link count 1 owned by UID(%d)", core_basename, user_pwd, fsuid);
-        return -1;
+        goto user_core_fail;
     }
     if (ftruncate(user_core_fd, 0) != 0) {
         /* perror first, otherwise unlink may trash errno */
         perror_msg("Can't truncate '%s' at '%s' to size 0", core_basename, user_pwd);
-        unlinkat(dirfd(proc_cwd), core_basename, /*unlink file*/0);
-        return -1;
+        goto user_core_fail;
     }
 
     return user_core_fd;
+
+user_core_fail:
+    if (user_core_fd >= 0)
+    {
+        close(user_core_fd);
+        unlinkat(dirfd(proc_cwd), core_basename, /*unlink file*/0);
+    }
+    return -1;
 }
 
 static bool dump_fd_info(const char *dest_filename, char *source_filename, int source_base_ofs, uid_t uid, gid_t gid)
-- 
1.8.3.1