commit - 7146dd552fe47a38934be51b8cf075096e4ff518
commit + 71b7eb2f8c3d0a85dfdf23e08bf89d0a4ad82aaf
blob - a8e301db2c554b8c7458a070d392692f8242d9f5
blob + 3fc469cdeb48dfc4dfa3ead5f9a97d08f318550f
--- sandbox.c
+++ sandbox.c
#elif defined(__linux__)
+#include <sys/prctl.h>
+#include <sys/syscall.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+
+#include <linux/audit.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <seccomp.h>
+#include <string.h>
+
+/* thanks chromium' src/seccomp.c */
+#if defined(__i386__)
+# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_I386
+#elif defined(__x86_64__)
+# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_X86_64
+#elif defined(__arm__)
+# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_ARM
+#elif defined(__aarch64__)
+# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_AARCH64
+#elif defined(__mips__)
+# if defined(__mips64)
+# if defined(__MIPSEB__)
+# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_MIPS64
+# else
+# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_MIPSEL64
+# endif
+# else
+# if defined(__MIPSEB__)
+# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_MIPS
+# else
+# define SECCOMP_AUDIT_ARCH AUDIT_ARCH_MIPSEL
+# endif
+# endif
+#else
+# error "Platform does not support seccomp filter yet"
+#endif
+
+/* uncomment to enable debugging. ONLY FOR DEVELOPMENT */
+/* #define SC_DEBUG */
+
+#ifdef SC_DEBUG
+# define SC_FAIL SECCOMP_RET_TRAP
+#else
+# define SC_FAIL SECCOMP_RET_KILL
+#endif
+
+/* make the filter more readable */
+#define SC_ALLOW(nr) \
+ BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_##nr, 0, 1), \
+ BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW)
+
+#ifdef SC_DEBUG
+
+#include <signal.h>
+#include <unistd.h>
+
+static void
+sandbox_seccomp_violation(int signum, siginfo_t *info, void *ctx)
+{
+ (void)signum;
+ (void)ctx;
+
+ fprintf(stderr, "%s: unexpected system call (arch:0x%x,syscall:%d @ %p)\n",
+ __func__, info->si_arch, info->si_syscall, info->si_call_addr);
+ _exit(1);
+}
+
+static void
+sandbox_seccomp_catch_sigsys(void)
+{
+ struct sigaction act;
+ sigset_t mask;
+
+ memset(&act, 0, sizeof(act));
+ sigemptyset(&mask);
+ sigaddset(&mask, SIGSYS);
+
+ act.sa_sigaction = &sandbox_seccomp_violation;
+ act.sa_flags = SA_SIGINFO;
+ if (sigaction(SIGSYS, &act, NULL) == -1) {
+ fprintf(stderr, "%s: sigaction(SIGSYS): %s\n",
+ __func__, strerror(errno));
+ exit(1);
+ }
+ if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1) {
+ fprintf(stderr, "%s: sigprocmask(SIGSYS): %s\n",
+ __func__, strerror(errno));
+ exit(1);
+ }
+}
+#endif /* SC_DEBUG */
+
void
sandbox()
{
- /* TODO: seccomp */
+ struct sock_filter filter[] = {
+ /* load the *current* architecture */
+ BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
+ (offsetof(struct seccomp_data, arch))),
+ /* ensure it's the same that we've been compiled on */
+ BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K,
+ SECCOMP_AUDIT_ARCH, 1, 0),
+ /* if not, kill the program */
+ BPF_STMT(BPF_RET | BPF_K, SC_FAIL),
+
+ /* load the syscall number */
+ BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
+ (offsetof(struct seccomp_data, nr))),
+
+ /* allow logging on stdout */
+ SC_ALLOW(write),
+ SC_ALLOW(writev),
+ SC_ALLOW(readv),
+
+ /* these are used to serve the files. note how we
+ * allow openat but not open. */
+ SC_ALLOW(ppoll),
+ SC_ALLOW(accept),
+ SC_ALLOW(fcntl),
+ SC_ALLOW(read),
+ SC_ALLOW(openat),
+ SC_ALLOW(fstat),
+ SC_ALLOW(close),
+ SC_ALLOW(lseek),
+ SC_ALLOW(brk),
+ SC_ALLOW(mmap),
+ SC_ALLOW(munmap),
+
+ /* we need recvmsg to receive fd */
+ SC_ALLOW(recvmsg),
+
+ /* XXX: ??? */
+ SC_ALLOW(getpid),
+
+ SC_ALLOW(exit),
+ SC_ALLOW(exit_group),
+
+ /* allow ioctl but only on fd 1, glibc doing stuff? */
+ BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_ioctl, 0, 3),
+ BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
+ (offsetof(struct seccomp_data, args[0]))),
+ BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 1, 0, 1),
+ BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
+
+ /* disallow enything else */
+ BPF_STMT(BPF_RET | BPF_K, SC_FAIL),
+ };
+
+ struct sock_fprog prog = {
+ .len = (unsigned short) (sizeof(filter) / sizeof(filter[0])),
+ .filter = filter,
+ };
+
+#ifdef SC_DEBUG
+ sandbox_seccomp_catch_sigsys();
+#endif
+
+ if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) {
+ fprintf(stderr, "%s: prctl(PR_SET_NO_NEW_PRIVS): %s\n",
+ __func__, strerror(errno));
+ exit(1);
+ }
+
+ if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog) == -1) {
+ fprintf(stderr, "%s: prctl(PR_SET_SECCOMP): %s\n",
+ __func__, strerror(errno));
+ exit(1);
+ }
}
#elif defined(__OpenBSD__)