Documentation: prctl/seccomp_filter

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / samples / seccomp / bpf-fancy.c

diff --git a/samples/seccomp/bpf-fancy.c b/samples/seccomp/bpf-fancy.c
new file mode 100644 (file)
index 0000000..8eb483a
--- /dev/null
+++ b/samples/seccomp/bpf-fancy.c
@@ -0,0 +1,102 @@
+/*
+ * Seccomp BPF example using a macro-based generator.
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_ATTACH_SECCOMP_FILTER).
+ */
+
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+#include <linux/unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#include "bpf-helper.h"
+
+#ifndef PR_SET_NO_NEW_PRIVS
+#define PR_SET_NO_NEW_PRIVS 38
+#endif
+
+int main(int argc, char **argv)
+{
+       struct bpf_labels l;
+       static const char msg1[] = "Please type something: ";
+       static const char msg2[] = "You typed: ";
+       char buf[256];
+       struct sock_filter filter[] = {
+               /* TODO: LOAD_SYSCALL_NR(arch) and enforce an arch */
+               LOAD_SYSCALL_NR,
+               SYSCALL(__NR_exit, ALLOW),
+               SYSCALL(__NR_exit_group, ALLOW),
+               SYSCALL(__NR_write, JUMP(&l, write_fd)),
+               SYSCALL(__NR_read, JUMP(&l, read)),
+               DENY,  /* Don't passthrough into a label */
+
+               LABEL(&l, read),
+               ARG(0),
+               JNE(STDIN_FILENO, DENY),
+               ARG(1),
+               JNE((unsigned long)buf, DENY),
+               ARG(2),
+               JGE(sizeof(buf), DENY),
+               ALLOW,
+
+               LABEL(&l, write_fd),
+               ARG(0),
+               JEQ(STDOUT_FILENO, JUMP(&l, write_buf)),
+               JEQ(STDERR_FILENO, JUMP(&l, write_buf)),
+               DENY,
+
+               LABEL(&l, write_buf),
+               ARG(1),
+               JEQ((unsigned long)msg1, JUMP(&l, msg1_len)),
+               JEQ((unsigned long)msg2, JUMP(&l, msg2_len)),
+               JEQ((unsigned long)buf, JUMP(&l, buf_len)),
+               DENY,
+
+               LABEL(&l, msg1_len),
+               ARG(2),
+               JLT(sizeof(msg1), ALLOW),
+               DENY,
+
+               LABEL(&l, msg2_len),
+               ARG(2),
+               JLT(sizeof(msg2), ALLOW),
+               DENY,
+
+               LABEL(&l, buf_len),
+               ARG(2),
+               JLT(sizeof(buf), ALLOW),
+               DENY,
+       };
+       struct sock_fprog prog = {
+               .filter = filter,
+               .len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
+       };
+       ssize_t bytes;
+       bpf_resolve_jumps(&l, filter, sizeof(filter)/sizeof(*filter));
+
+       if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+               perror("prctl(NO_NEW_PRIVS)");
+               return 1;
+       }
+
+       if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
+               perror("prctl(SECCOMP)");
+               return 1;
+       }
+       syscall(__NR_write, STDOUT_FILENO, msg1, strlen(msg1));
+       bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf)-1);
+       bytes = (bytes > 0 ? bytes : 0);
+       syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2));
+       syscall(__NR_write, STDERR_FILENO, buf, bytes);
+       /* Now get killed */
+       syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2)+2);
+       return 0;
+}