From 63e9d849f662d1a494c6396d4a439cd4c91dfa7e Mon Sep 17 00:00:00 2001
From: Topi Miettinen <toiwoton@gmail.com>
Date: Sun, 13 Aug 2017 14:07:31 +0300
Subject: Allow any syscall to be blacklisted (#1447)

Allow any syscall to be blacklisted with aid of LD_PRELOAD library,
libpostexecseccomp.so.

Closes: #1447
---
 src/libpostexecseccomp/libpostexecseccomp.c | 59 +++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 src/libpostexecseccomp/libpostexecseccomp.c

(limited to 'src/libpostexecseccomp/libpostexecseccomp.c')

diff --git a/src/libpostexecseccomp/libpostexecseccomp.c b/src/libpostexecseccomp/libpostexecseccomp.c
new file mode 100644
index 000000000..801f968a6
--- /dev/null
+++ b/src/libpostexecseccomp/libpostexecseccomp.c
@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2017 Firejail Authors
+ *
+ * This file is part of firejail project
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+#include "libpostexecseccomp.h"
+#include <fcntl.h>
+#include <linux/audit.h>
+#include <linux/bpf.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+#include <sys/mman.h>
+#include <sys/prctl.h>
+#include <sys/ptrace.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+__attribute__((constructor))
+static void load_seccomp(void) {
+	int fd = open(RUN_SECCOMP_POSTEXEC, O_RDONLY);
+	if (fd == -1)
+		return;
+
+	int size = lseek(fd, 0, SEEK_END);
+	unsigned short entries = (unsigned short) size / (unsigned short) sizeof(struct sock_filter);
+	struct sock_filter *filter = MAP_FAILED;
+	if (size != 0)
+		filter = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
+
+	close(fd);
+
+	if (size == 0 || filter == MAP_FAILED)
+		return;
+
+	// install filter
+	struct sock_fprog prog = {
+		.len = entries,
+		.filter = filter,
+	};
+
+	prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	munmap(filter, size);
+}
-- 
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