1 files changed, 142 insertions, 0 deletions
diff --git a/jail/seccomp.c b/jail/seccomp.c
new file mode 100644
index 0000000..de01fc6
--- /dev/null
+++ b/jail/seccomp.c
@@ -0,0 +1,142 @@
+/*
+ * seccomp example with syscall reporting
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Authors:
+ *  Kees Cook <keescook@chromium.org>
+ *  Will Drewry <wad@chromium.org>
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#define _GNU_SOURCE 1
+#include <stdio.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <syslog.h>
+
+#include <libubox/utils.h>
+#include <libubox/blobmsg.h>
+#include <libubox/blobmsg_json.h>
+
+#include "seccomp-bpf.h"
+#include "seccomp.h"
+#include "../syscall-names.h"
+
+static int max_syscall = ARRAY_SIZE(syscall_names);
+
+static int find_syscall(const char *name)
+{
+	int i;
+
+	for (i = 0; i < max_syscall; i++)
+		if (syscall_names[i] && !strcmp(syscall_names[i], name))
+			return i;
+
+	return -1;
+}
+
+static void set_filter(struct sock_filter *filter, __u16 code, __u8 jt, __u8 jf, __u32 k)
+{
+	filter->code = code;
+	filter->jt = jt;
+	filter->jf = jf;
+	filter->k = k;
+}
+
+int install_syscall_filter(const char *argv, const char *file)
+{
+	enum {
+		SECCOMP_WHITELIST,
+		SECCOMP_POLICY,
+		__SECCOMP_MAX
+	};
+	static const struct blobmsg_policy policy[__SECCOMP_MAX] = {
+		[SECCOMP_WHITELIST] = { .name = "whitelist", .type = BLOBMSG_TYPE_ARRAY },
+		[SECCOMP_POLICY] = { .name = "policy", .type = BLOBMSG_TYPE_INT32 },
+	};
+	struct blob_buf b = { 0 };
+	struct blob_attr *tb[__SECCOMP_MAX];
+	struct blob_attr *cur;
+	int rem;
+
+	struct sock_filter *filter;
+	struct sock_fprog prog = { 0 };
+	int sz = 5, idx = 0, default_policy = 0;
+
+	INFO("%s: setting up syscall filter\n", argv);
+
+	blob_buf_init(&b, 0);
+	if (!blobmsg_add_json_from_file(&b, file)) {
+		INFO("%s: failed to load %s\n", argv, file);
+		return -1;
+	}
+
+	blobmsg_parse(policy, __SECCOMP_MAX, tb, blob_data(b.head), blob_len(b.head));
+	if (!tb[SECCOMP_WHITELIST]) {
+		INFO("%s: %s is missing the syscall table\n", argv, file);
+		return -1;
+	}
+
+	if (tb[SECCOMP_POLICY])
+		default_policy = blobmsg_get_u32(tb[SECCOMP_POLICY]);
+
+	blobmsg_for_each_attr(cur, tb[SECCOMP_WHITELIST], rem)
+		sz += 2;
+
+	filter = calloc(sz, sizeof(struct sock_filter));
+	if (!filter) {
+		INFO("failed to allocate filter memory\n");
+		return -1;
+	}
+
+	/* validate arch */
+	set_filter(&filter[idx++], BPF_LD + BPF_W + BPF_ABS, 0, 0, arch_nr);
+	set_filter(&filter[idx++], BPF_JMP + BPF_JEQ + BPF_K, 1, 0, ARCH_NR);
+	set_filter(&filter[idx++], BPF_RET + BPF_K, 0, 0, SECCOMP_RET_KILL);
+
+	/* get syscall */
+	set_filter(&filter[idx++], BPF_LD + BPF_W + BPF_ABS, 0, 0, syscall_nr);
+
+	blobmsg_for_each_attr(cur, tb[SECCOMP_WHITELIST], rem) {
+		char *name = blobmsg_get_string(cur);
+		int nr;
+
+		if (!name) {
+			INFO("%s: invalid syscall name\n", argv);
+			continue;
+		}
+
+		nr  = find_syscall(name);
+		if (nr == -1) {
+			INFO("%s: unknown syscall %s\n", argv, name);
+			continue;
+		}
+
+		/* add whitelist */
+		set_filter(&filter[idx++], BPF_JMP + BPF_JEQ + BPF_K, 0, 1, nr);
+		set_filter(&filter[idx++], BPF_RET + BPF_K, 0, 0, SECCOMP_RET_ALLOW);
+	}
+
+	if (default_policy)
+		/* return -1 and set errno */
+		set_filter(&filter[idx], BPF_RET + BPF_K, 0, 0, SECCOMP_RET_LOGGER(default_policy));
+	else
+		/* kill the process */
+		set_filter(&filter[idx], BPF_RET + BPF_K, 0, 0, SECCOMP_RET_KILL);
+
+	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		INFO("%s: prctl(PR_SET_NO_NEW_PRIVS) failed: %s\n", argv, strerror(errno));
+		return errno;
+	}
+
+	prog.len = (unsigned short) idx + 1;
+	prog.filter = filter;
+
+	if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
+		INFO("%s: prctl(PR_SET_SECCOMP) failed: %s\n", argv, strerror(errno));
+		return errno;
+	}
+	return 0;
+}